2 x 2 hours: 14:00 - 16:00 and 18:00 - 20:00 (same Gatherly link)

Come and meet old and new colleagues from around the world in the pre-conference mixer on Gatherly. The networking platform is ideal for spontaneous meetings, like the one you would do with a colleague you meet on the eve of a 'normal' conference. Your 'avatar' symbol lands in the Welcome Area and then you can then explore different floors and join colleagues and "huddles" for video-chats. Not sure, who will attend? Look for registered participants at the "Who will attend the LFC44?" tab.

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LFC44 strongly advises to read our Meeting on Gatherly guidelines before, to hopefully give everyone a satisfactory experience. You need to use Google Chrome as your browser for this. You should probably be where your best LAN/W-LAN connection is. Gatherly does not currently support phones or tablets. We strongly recommend using a screen of at least 11" size (laptop).

Long-term ichthyoplankton datasets exist around the globe either as dedicated routine sampling efforts funded through government agencies or as series of independent-PI sampling programs conducted in common geographic areas. These datasets have been used to address ecological and oceanographic questions that have provided valuable data for forecasting and managing global fisheries. However, funds for and logistics of maintaining such programs are daunting. Further, sampling design, continuity of methodology, sample preservation, metadata associated with data archiving, and open access to written, digital, and biological data are essential components of a useful dataset. In this era of global climate change, long-term datasets are especially useful for the examination of process-oriented questions. Initiating, continuing, or collaborating to use a long-term dataset is possible with creative approaches. All of us should look to the future and prepare our field to generate data critical to advancing our knowledge of fisheries ecology in a changing ocean.

• Theme: Recruitment processes
• Authors: Raphael Lagarde*, Jason Peyre, Elsa Amilhat, Francois Bourrin, Alexandre Perrault, Gal Simon, Elisabeth Faliex
• Title: Phenology and environmental drivers of glass eels recruitment in a Mediterranean lagoon

 

European eel, Anguilla anguilla, is an emblematic diadromous species which population has dropped since 1980. Although Mediterranean lagoons represent productive brackish ecosystems, particularly important for eel, knowledge of eel ecology in Mediterranean lagoons is not as developed as it is in rivers. Particularly, data on glass eels recruitment to the lagoons are scares. To address this lack of data, recruitment was monitored daily during 647 days from December 2018 to march 2021 using passive traps in Bages-Sigean lagoon. Simultaneously, environmental drivers were measured at the sampling site (turbidity, flow velocity, temperature) or at the closest meteorological stations (rainfalls, wind, atmospheric pressure, cloud cover). Recruitment was highly variable with an annual peak of abundances occurring between November and March. This work highlights that the discharge of the main tributary of the lagoon mainly influenced glass eel recruitment, enabling us to identify key periods when anthropogenic activities should be limited.

• Theme: Recruitment processes
• Authors: Christoffer Nagel*, Melanie Mueller, Joachim Pander, Bernhard C. Stoeckle, Ralph Kuehn & Juergen Geist
• Title: Fish larvae drift in regulated large alpine rivers- a case study from the River Inn

 

In this study, we characterized spatio-temporal drift patterns of fish larvae in the heavy regulated large alpine River Inn and within a constructed nature-like fish bypass. Drift was investigated in the main reproduction period of the fish fauna in this river. Diel patterns were assessed during day, dusk, night and dawn. Phenotypic species identification was verified by DNA barcoding. We detected drifting larvae from 16 species including several target species of conservation. By comparing spatially resolved drift densities, we found strong evidence that several endangered species successfully reproduced in the bypass system. Distinct seasonal patterns were observed, with Thymallus thymallus and Cottus gobio dominating larval drift in the beginning of the observation followed by abundance peaks of several Cyprinid species. Nocturnal drift prevailed in all species. Our results represent a vital basis to direct future management in large alpine rivers towards a protection of the sensitive larval stages.

• Theme: Recruitment processes
• Authors: Oyvind Langnes, Elena Eriksen, Arild Folkvord*
• Title: Liver condition of 0 and 1-group cod (Gadus morhua) in the Barents Sea

 

Liver condition is hypothesized to be a better condition index for juvenile cod than other somatic condition indices, since cod store most of their excess energy in their liver. It is suggested that population changes in liver condition can be used as a proxy for overwinter mortality. Here we have collected 0 and 1-group cod from the same cohort in the Barents Sea, before and at the end of the winter season and taken measurements for somatic- and liver-based condition indices, as well as enumerating endoparasites found in each individual. The average wet weight of sampled cod increased 85 %, or approx. 0.4% day-1, from 6.0 to 10.4 g from September to February, while the average liver wet weight decreased 15%. The relative water content of the liver also increased significantly over the winter, resulting in a 42% reduction in average dry liver weight from 0.116 to 0.067 g over the 4-5 month period between samplings. The significance of this loss of organic liver content is discussed in relation to the marked seasonality and the challenges this imposes on survival of 0-group cod in high latitude environments during their first winter.

• Theme: Recruitment processes
• Authors: Anna Akimova, Gregor Boerner, Cindy van Damme, Myron A. Peck, Marta Moyano
• Title: Physiological modelling helps pinpoint processes contributing to the recent recruitment failure of North Sea herring

 

Early-life history of marine fishes is one of the main drivers of the recruitment variability and an important bottleneck in the adaptation of fish populations to changing climate. We combined observations on zooplankton size-structure and larval physiological modelling to explore the mechanism(s) causing recent recruitment depression of North Sea herring. Starvation morality mainly occurred in very young first-feeding larvae (< 10 mm), rates of mortality rapidly decreased with increasing body size, and that prey fields supported maximum growth rates for larvae > 13-14 mm. Model-based estimates of the cumulative starvation mortality were highly sensitive to the variability in the length distribution (8 to 10 mm) of first-feeding larvae, a trait which appears to be poorly known for the North Sea herring stock. Despite this uncertainty, our estimates of starvation mortality were 3 to 10 times lower than the total morality calculated from the in situ larval abundance. These results suggest that starvation was not the main source of larval mortality and that additional processes (e.g. predation and/or prey deficits impacting later larval or juvenile stages) have likely contributed to the recruitment failure in this stock.

• Theme: Recruitment processes
• Authors: V. Baptista*, Claudio Carere, Pedro Morais, Joana Cruz, Francisco Leitao, Maria Alexandra Teodesio
• Title: Personality in a temperate pelagic fish larva may affect recruitment in nursery habitats

 

Animals show personality traits, i.e., they differ consistently in behavior. This inter-individual variability has significant ecological consequences since it affects a range of population-level processes. Here, we focus on the selection of nursery habitats in temperate fish larvae. The Sense Acuity and Behavioral Hypothesis states that temperate fish larvae could detect and follow environmental cues to choose nursery habitats. We empirically tested this hypothesis questioning if this non-random and active process occurs and if it could be mediated by consistent individual differences in behavior. We used Diplodus sargus larvae as a model species to perform repeated tests along ontogeny using a choice chamber. In the chamber, larvae were exposed to stimuli of different nursery habitats (lagoon, coastal) and environmental cues (two levels of temperature and salinity) to quantify preference and exploratory activity. Most of the larvae changed their behavior during ontogeny, but they were also significantly consistent in their behavior revealing strong individuality. However, no significant preference for the presented stimuli emerged. Exploratory activity was higher when larvae showed unresponsive or inconclusive behaviors, meaning that the larvae were trying to find a different stimulus or had random habitat selection. Overall, consistent individual differences in D. sargus behavior may influence the search for nursery habitats and, consequently, dispersion and connectivity.

Dr. Aditya Nayak | Florida Atlantic University | -- Holographic imaging

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Dr. Lee Fuiman | The University of Texas) | -- Food-web tracing in fish eggs

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Dr. Jessica Miller | Oregon State University | -- Otolith microchemistry

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Dr. Wes Larson | NOAA Fisheries | -- eDNA

• Theme: Larval Assemblages
• Authors: Sinan Mavruk*, Cihan Toslak, Fatma Banu Yalim, Ozgur Aktas, Fethi Bengil, Meltem Ok, Ahsen Yuksek
• Title: Spatial, intra and interannual changes of summer larvalfish assemblages and influence of environmental conditions in Antalya Bay, North-Eastern Mediterranean

 

Here we investigated the spatial and temporal changes of the structure of the larval-fish assemblages (LFAs) in Antalya Bay, the Eastern Mediterranean. Ichthyoplankton samples were collected in June 2018 and June, July, August, September, and October 2019 using oblique Bongo-60 tows. The temperature below thermocline was lower in 2019 and this caused a change in assemblage composition with an increase in abundance of several mesopelagic species like Ceratoscopelus maderensis. After June, significant changes existed in the structure of LFAs, the richness and total abundance values of which decreased in correlation with the increasing temperature. While bathy and mesopelagic species dominated the offshore assemblages, larvae of Indo-Pacific fish were among characteristic species of the coastal assemblages throughout the late summer and early autumn. In conclusion, temperature was the primary driver of spatio-temporal patterns, and spawning activities of invasive fish have important roles in the structuring of LFAs in Antalya Bay.

• Theme: Larval Assemblages
• Authors: Stacy Provo, April Simmons, Robin DeBruyne, Hannah Schaefer, Dimitry Gorsky, Brendan Nee, Stacey Ireland, and Edward Roseman
• Title: Distribution of Larval Coregonines in Southern Lake Erie

 

Cisco (Coregonus artedi) and Lake Whitefish (C. clupeaformis) historically supported a robust commercial fishery in Lake Erie. By the mid-20th century, the fishery declined due to overfishing, habitat degradation, and invasive species impacts. Increased interest in coregonine restoration identified a need for contemporary information on spawning and nursery habitat. To address this, we sampled pelagic coregonine larvae in 2017 and 2019 at 38 sites along the southern shore of the central and eastern basins. Coregonines were detected during April and May, with densities peaking in mid-April. Larval densities were highest near Sandusky, OH, close to the western basin where widespread Lake Whitefish reproduction occurs. Based on our catches of yolksac larvae, additional coregonine spawning is likely occurring in the eastern basin. Our results provide a contemporary assessment of coregonine larval distribution in Lake Erie and insight about spawning and nursey habitat necessary to develop restoration and recovery strategies.

• Theme: Larval Assemblages
• Authors: Dauden-Bengoa G*, Jiminez-Rosenberg SPA, Fernandez-Alamo MA, Ordoez-Lopez U, Echeverri-Garcia, LP, Herzka SZ
• Title: Comparison of ichthyoplankton with contrasting life histories as function of oceanographic variables in the GoM

 

In the southern Gulf of Mexico, larvae of neritic species are captured alongside oceanic species in the deep water region, likely due to cross-shelf transport. We used GAMs to examine the relationship between oceanographic variables and ichthyoplankton of species with contrasting life history strategies based on data from 12 cruises within the Mexican EEZ. We hypothesized that the abundance of oceanic species would have a significant relationship with oceanographic variables indicative of higher productivity, while there would be no correlation for neritic species. Abundance of neritic larvae was low and limited to near the slope, and few correlations with oceanographic variables were found. Larvae of mesopelagic species were broadly distributed, and their abundance was correlated with higher chlorophyll concentration and lower SST, indicative of high nutrient availability. Larvae of neritic species caught in oceanic waters do not exhibit specific habitat requirements and will likely fail to recruit to adult populations.

• Theme: Form, function, development
• Authors: Thornton Ritz* and Jill B.K. Leonard
• Title: Understanding larval development of burbot (Lota lota) and its role in their persistence throughout North America

 

Burbot (Lota lota) exhibit unique life history characteristics for a freshwater fish and are often under researched in North America. Utilizing laboratory-reared samples from Great Lakes and Idaho populations and historical wild caught Great Lakes samples, we explored larval burbot characteristics and hypothesized on their ecological relevance. Geometric and linear morphology displayed significant morphological differences throughout the stages of larval development. Among populations, significant morphological differences associated with development and larval size were apparent. We hypothesize that variability in laboratory-reared and wild caught samples demonstrate important flexibility in larval development of burbot. Distinct larval stages and growth patterns help stress the importance of asynchronous hatching and the potential ecological consequences related to this process. From patterns discerned in both laboratory and wild samples we demonstrate the importance of asynchronous hatching, source location and temporal variability in larval burbot development and ultimately point to its role in their continued persistence.

• Theme: Form, function, development 
• Authors: Aubree E. Jones*, Matthew J. O'Donnell, Amy M. Regish, Jacqueline F. Webb
• Title: Larval Period Duration and the Timing of Lateral Line Development in Brook Trout (Salvelinus fontinalis)

 

The lateral line system (LL) undergoes rapid changes in fishes from hatch through metamorphosis. The neuromast receptor organs of the LL develop on the skin, and either remain on the skin (superficial neuromasts) or become enclosed in bony, pored canals on the head and trunk (canal neuromasts; CNs). Salmonids are known for their long larval stage, the duration of which is affected by temperature. They also have a high number of CNs compared to other fishes. We showed that in brook trout the number of presumptive CNs doubles during the long alevin stage. The occurrence of a long larval period and high CN number suggests that the prolonged larval stage allows for the generation of more CNs than in non-salmonid species with shorter larval stages. Further, increased temperatures, one of the factors that affect salmonid development (including larval stage duration) will likely impact CN number with consequences for flow sensing.

• Theme: Form, function, development
• Authors: E.T. Mason*, L. Buckeley, A.C. Salazar Sawkins, A.R. Thompson, W. Watson, and B.X. Semmens
• Title: Uncoding comparable morphologies: Using genetics, morphological traits, and machine learning to calibrate classification

 

Temporal trends in larval fish abundance are indices of spawning stock biomass and provide fishery-independent measures of population dynamics. However, when larvae are morphologically indistinguishable and preserved in formalin (degrades DNA thus precluding genetic identification), unraveling species-specific larval abundances from long-term monitoring efforts can seem insurmountable. We used a novel combination of molecular identities of ethanol-preserved larvae, morphological characters of each larva, Bayesian inference, and a Random Forest Classifier (RFC) to calibrate species classifications for three congeners of marine bass (Paralabrax spp.). Data on morphological traits accurately predicted species with > 90% probability for most larvae. The RFC uncovered traits having the greatest positive effect on classification accuracy across larval stage. A refined morphological key yielded >95% accuracy and precision for each species. We thus provide a robust template for future development of accurate taxonomic keys that inherently incorporates inter-specific variability in morphological characters and taxonomic bias.

• Theme: Recruitment processes
• Authors: Kelsey Swieca*, Su Sponaugle, Mortiz Schmid, Robert K. Cowen
• Title: Oceanographic and trophodynamic underpinnings of anchovy success in the northern California Current

 

The recent breakdown in the anchovy-sardine cold-warm paradigm in the California Current (CC) suggests that recruitment may not be a simple reflection of large-scale physical drivers. Instead, consideration of larval fish trophodynamics together with local oceanography is likely necessary to mechanistically relate survival and recruitment to the physical environment. We examined otolith-derived metrics of northern anchovy (Engraulis mordax) growth in the context of local oceanography and their in situ prey and predators in the northern CC during two years of contrasting local summer conditions: upwelling relaxation (2018) and sustained upwelling (2019). Overall anchovy growth rate did not differ between years but was substantially faster than previously recorded for this species. Early larval growth was similar across space until 11 dph when growth diverged such that offshore anchovy grew significantly faster than inshore anchovy in 2018 whereas the reverse occurred in 2019. Variability in anchovy recent (last 3 full days) growth with local oceanographic conditions and fine-scale distributions of prey and predators illustrates the importance of examining food-web dynamics when predicting the response of forage fish to ecosystem variability.

• Theme: Recruitment processes
• Authors: Rasmus Swalethorp*, Michael R. Landry, Brice X. Semmens, Lihini Aluwihare, Dereka Chargualaf, Andrew R. Thompson
• Title: Trophic shifts in larval diet explains booms and busts of Northern Anchovy

 

Northern Anchovy (Engraulis mordax) stocks have experienced large size fluctuations historically, even before the onset of fishing, likely in response to oceanographic changes. Despite decades of research, the mechanisms driving these fluctuations are elusive. We tested the hypothesis that larval trophic dynamics drives population volatility. We used a new high-precision isotopic analytical procedure on amino acid nitrogen from individual formalin-preserved larvae collected off California from 1960-2005 by the CalCOFI program. Immediately prior and during the population crash (late 1980s), the food chain length (FCL) of larval increased significantly in response to changes in prey community impacting the survival of young larvae particularly vulnerable to starvation. FCL correlated significantly with adult spawning stock biomass, with correlation being highest (r2=0.6) with a lag of two years. These findings suggest that low larval survival due to inefficient energy transfer from the food web base is the main mechanism driving Anchovy booms and busts.

• Theme: Recruitment processes
• Authors: Megan N. Wilson*, Kirsten Grorud-Colvert, Su Sponaugle
• Title: Tortoise and Hare: distinct early growth strategies in a groundfish persist in a seasonally variable environment

 

The Northern California Current (NCC) is a highly productive eastern boundary current system that sustains socio-economically important fisheries. One such species, cabezon (Scorpaenichthys marmoratus) recruits in multiple events throughout the reproductive season, a departure from the more common single-pulse recruitment strategy. Given the extended recruitment window coupled with seasonal variability in the NCC, we hypothesized that cabezon exhibit a “portfolio” of early life strategies that increase survival by maximizing chances of alignment with suitable environmental conditions. We quantified otolith-based early life history traits (e.g., growth rate, age-at-settlement) of new settlers across five annual recruitment seasons. Our findings revealed that at least two distinct early life strategies were consistently represented each year, encompassing significant environmental variability. Plasticity in early life may be a source of resilience for populations, which is especially important considering that phenological processes that regulate recruitment are predicted to become decoupled with climate change.

• Theme: Recruitment processes
• Authors: Jess Hopf
• Title: Larval recruitment variability and sampling design interact to influence the detectability of marine reserve effects

 

Abundances of harvested populations are expected to increase monotonically after establishing a no-take marine protected area (hereafter, 'reserve'). However, large-scale temporal fluctuations in larval recruitment drive interannual variations in fish populations that likely interact with reserve effects. The consequence of this for monitoring and assessing reserve success are unknown. To predict population changes in the years following the implementation of a no-take reserve, we tested for periodicity in larval recruitment in an important U.S. Pacific coast recreational fishery species (Kelp Bass) and then included that periodic pattern in a population model. We also used this model to determine the detectability of population increases under alternative sampling approaches and minimum age sampled.We demonstrate that variable larval recruitment can obscure reserve effects and that some types of reserve assessment designs (before-after) are more sensitive to that variation than others (control-impact, before-after-control-impact). We encourage managers to account for variable larval recruitment when planning monitoring and assessment programs.

• Theme: Form, function, development
• Authors: Michaela Kolker*, Ken Thompson, Asli Munzur, Prof. Dolph Schluter, Prof. Shai Meiri, Prof. Roi Holzman
• Title: Accelerating morphological disparity during ontogeny leads to two convergent morphotypes in the three-spine stickleback

 

The three-spine stickleback species complex presents a unique opportunity for exploring habitat-derived convergent morphologies. As marine sticklebacks colonized glacial lakes repeatedly, they rapidly evolved morphotypes that occupy separate niches: pelagic and benthic. Adult morphotypes differ in niche use, diet, and feeding-related functional morphology. It was unclear when during ontogeny these differences manifest, and whether they represent any adaptations to the shared larval habitat, or to the divergent adult one. We examined three British Columbia lakes species-pairs and a coastal marine population. All populations are morphologically distinct throughout their ontogeny. Traits consistently present a shift in their morphological trajectory at a standard length of ~13 mm, during which they diverge more rapidly between morphotypes. Our findings show a departure from a hypothetical abrupt niche shift from larvae to juveniles. Traits are disparate from hatching and continue to diverge continuously, even after the period traditionally defined as the end of ontogenetic change.

• Theme: Form, function, development
• Authors: V. Puig-Pons, A. Ladino* , V. Espinosa , I. Perez-Arjona , A. Ortega, F. de la Gandara
• Title: Using ultrasound for the monitoring and control of larval development of gilthead seabream (Sparus aurata) in tanks.

 

In this work, we propose a non-invasive acoustic technique using ultrasound for the monitoring and control of larval development of gilthead seabream (Sparus aurata) in tanks. Biological measurements and target strength (TS) measurements have been carried out using a EK60 Simrad echosounder working at 200 kHz. The experiments have been carried out for three consecutive years in the marine aquaculture plant that Spanish Institute of Oceanography (IEO) has at Mazarran (Murcia, Spain). For the interpretation of the results, backscatter models were considered using the finite element method. The target strength values were evidenced with and without the presence of the developed swimbladder, showing a statistically significant relationship with the standard length, the area of the swimbladder and the percentage of larvae with a swimbladder.

• Theme: Form, function, development
• Authors: Todd R. Clardy*, Alison L. Deary
• Title: Ontogeny of the feeding apparatus of the White Croaker, Genyonemus lineatus (Sciaenidae)

 

In fishes, elements of the jaws can undergo drastic changes during development as species transition from larval diets to specialized adult diets. The family Sciaenidae is a species-rich group of nearshore fishes with varied, specialized diets as adults and can be classified into three broad foraging guilds: benthic, generalist, and pelagic. Here, we describe the jaw development of the White Croaker, Genyonemus lineatus, a benthic sciaenid from the Northeastern Pacific. A developmental series of G. lineatus, ranging from 4.1 to 43.2 mm TL, was cleared and stained. Anatomical features of the oral and pharyngeal jaws and gill arches were measured to assess development of the feeding apparatus. The observed patterns for G. lineatus then were compared against sciaenids from the Northwestern Atlantic from benthic, generalist, and pelagic guilds to test whether G. lineatus shares a similar benthic guild developmental trajectory.

• Theme: Form, function, development
• Authors: Fanny Rioual*, Claudia Ofelio, Maryandrea Rosado-Salazar, Jhon Dionicio-Acedo, Myron A. Peck, Arturo Aguirre-Velarde
• Title: Captive rearing of Peruvian anchovy (Engraulis ringens): Early development and growth modelling

 

The Peruvian anchovy supports one of the worlds largest single-species fisheries. Predicting how its early life stages are affected by environmental factors, such as temperature, is particularly important for recruitment dynamics and stock assessment. Anchovy larvae were successfully reared up to 33 days, at 14.5 and 18.5°C. Mouth opening and complete yolk sac absorption occurred after 1 and 3 days post-hatch (dph), respectively. Larvae were sequentially fed motile dinoflagellates (Akashiwo sanguinea), rotifers (Brachionus plicatilis) and Artemia nauplii and first exhibited schooling behaviour at 31 dph at 18.5°C. Temperature significantly affected larval size-at-age and was incorporated into a von Bertalanffy growth function, as a correction factor based on the Vant Hoff-Arrhenius equation. Using the same set of parameters, this simple, bioenergetics-based model captured not only larval but also juvenile and adult size-at-age and will prove useful in future explorations of how environmental factors influence anchovy growth.

• Theme: Form, function, development
• Authors: Monica G. Mai*, Maria Rita Pegado, Rui Rosa, Pedro Pouso-Ferreira, Ana Mendes, Marta S. Pimentel
• Title: Transgenerational acclimation of seabream (Sparus aurata) to ocean warming

 

The oceans play a key role in mitigating global climate change, one of the most serious challenges facing our world today. Consequently, oceans are suffering dramatic changes such as ocean warming. An elevation of 4C in the global ocean temperature is expected in a business-as-usual scenario until the end of the century. Ocean warming effects on fish early ontogenetic stages have been deeply studied, however, it is still unclear if transgenerational acclimation can be an important mechanism to mediate its impacts. Therefore, the present work aimed to investigate if parental exposure of Gilthead seabream (Sparus aurata) to ocean warming (4C) affects the progeny's early development. To unravel these effects, we collected eggs from breeders kept for 5 months in different temperatures, a control one (16C) and other in warming conditions (20C). In a multi-factorial design, we assigned the progeny to both treatments. We will here present preliminary data regarding how parental acclimation affects the impacts of warming on larval hatching rates, growth, and otoliths size.

• Theme: Form, function, development
• Authors: A. Pons*; E. Aspillaga; R. Rosselli-Mora; T. Viver; M. Signaroli; J. Sanllehi; M. Martorell; M. Barceli; J. A.
• Title: Behavioral types correlate with gut microbiome in early-life stages of wild gilthead seabream

 

There is a lack of understanding of how behavior is shaped along fish ontogeny. The interaction between intestinal microbiome (IM) and behavior, and the underlying mechanisms, are well documented in some mammals, but remain largely unexplored in wild fish. We conducted behavioral tests in wild juvenile gilthead seabream, Sparus aurata, along five axes of personality (activity, boldness, aggressiveness, sociability, and exploration), to determine among- and within-individual variances using LMM. We detected high levels of repeatability and consistent behavioral types along these axes. Subsequently, we collected gut samples from individuals categorized in different behavioral types and quantified the microbial diversity using operational phylogenetic units (OPUs) based on the analysis of 16S rRNA gene amplicons using Illumina high-throughput sequencing. The behavioral types correlated with the diversity, composition, and structure of the IM. This is one of the first evidence of the link between individual behavioral types and IM in juvenile marine fish.

• Theme: Form, function, development
• Authors: Olivia Lestrade, Leila Hamdan, Anirban Ray, Robert Griffitt, and Frank J. Hernandez
• Title: Microbial Communities of Sargassum and Associated Microplastics Influence Juvenile Gray Triggerfish Gut Microbiome

 

Microplastics in surface waters of the Gulf of Mexico are concentrated within holopelagic Sargassum (a nursery habitat for juvenile fishes), and provide a new substrate for marine microbe colonization. This study aims is to examine relationships among the microbial communities of co-occurring juvenile Gray Triggerfish (gut flora), microplastics, Sargassum, and ambient water. DNA was extracted from each sample type and the 16S rRNA genes were sequenced to characterize each associated microbiome. Microplastics, Sargassum, and ambient water had higher microbial diversity and richness than Gray Triggerfish guts, and each associated microbiome was defined by specific operational taxonomic units. Our results suggest, Gray Triggerfish gut flora was sourced from microplastics (10.3%), Sargassum (6.9%), and water (16.4%) microbial communities. This study provides the first quantitative estimates of Sargassum-associated microplastic and Gray Triggerfish gut microbial communities, and provides evidence that the gut flora of developing fishes are being influenced by microplastic microbial communities.

• Theme: Recruitment processes
• Authors: Emilie A. Geissinger*; Chelsea R. Bloom; Robert S. Gregory; Benjamin J. Laurel, Paul V.R. Snelgrove
• Title: Size, condition, and winter duration: Insights on winter survivorship of juvenile cod

 

Juvenile Atlantic cod in coastal Newfoundland settle within nearshore habitats in multiple events (3-6) each year. These events, known as pulses, create a unique size-structured population in the first year of life. Multiple settlement periods, combined with intense winters, can result in size-structured survival. Cod that settle earlier in the year could potentially grow larger and develop more fat stores to survive long, harsh winters in coastal Newfoundland. Our study combines a 25-year juvenile cod survey with winter temperature logs and archived juvenile cod samples to determine the impact of winter duration, body condition, and settlement time on overwinter survival. Our analyses demonstrate the importance of condition entering winter for survival and for high overwinter survival in late-settling pulses. These findings represent an important step in understanding the importance of broadcast spawning for overwinter survival in sub-arctic marine systems in a changing climate.

• Theme: Recruitment processes
• Authors: Robin L. DeBruyne*, Taaja R. Tucker, Clara Lloyd, Andrew S. Briggs, Megan Belore, Edward F. Roseman
• Title: Distribution and Abundance of Pelagic Larval Yellow Perch in Lake St. Clair (US/Canada) and Adjoining Waters

 

Long-term ichthyoplankton surveys revealed Yellow Perch originating from Lake St. Clair contribute to the recreationally and commercially important Lake Erie stock. We examined the density and distribution of larval Yellow Perch in Lake St. Clair and the Detroit River (2018 -2019) to identify spawning and nursery areas and ecological factors influencing their early life history. Larval Yellow Perch were first captured when mean lake temperatures reached 7-11°C. Significant larval density hot spots were present in Mitchell's and Anchor Bays coinciding with high levels of submerged aquatic vegetation. Weekly Detroit River larval densities were generally lower than those in Lake St. Clair. Larval densities were higher in 2018 than 2019. By combining measurements of larval density with environmental factors, we identified two areas providing suitable habitat for larval Yellow Perch survival and growth through mid-summer to aid future management of this species and its habitats in Lake St. Clair.

• Theme: Recruitment processes
• Authors: Katelyn Cunningham* and Erin Dunlop
• Title: Changes in density and growth of larval lake whitefish after ecosystem changes in Lake Huron

 

Lake whitefish (Coregonus clupeaformis) are an ecologically and commercially significant species in the Laurentian Great Lakes. Over the past 20 years, lake whitefish populations in Lake Huron have shown drastic declines, potentially linked to the invasion of dreissenid mussels and resulting ecosystem changes. In this study, larval fish were sampled from the Fishing Islands region in Lake Huron in order to determine if declines in recruitment are linked to poor growth and survival during the larval period. Larval fish were collected during two time periods: a historical time period prior to dreissenid mussel establishment (1976-1986) when lake whitefish population abundances were higher, and a recent period (2017-2019) when lake whitefish population abundances were low. Substantial year-to-year variability was observed in both time periods in larval production and growth, pointing to the possible role of environmental factors (e.g., ice cover) affecting larval dynamics. Importantly, we observed lower larval lake whitefish densities in recent years, suggesting that recruitment is being limited at the larval stage. We furthermore observed a lower larval growth rate in recent years after accounting for variation in growing degree days. These slower larval growth rates are consistent with the hypothesis that reduced food availability during critical early life stages are contributing to reduced recruitment of lake whitefish, potentially due to dreissenid mussel establishment.

• Theme: Recruitment processes
• Authors: Ghinter Leopold*
• Title: A first glimpse into the larval ecology of halibut species in the Gulf of St. Lawrence, Canada

 

Knowledge on the larval ecology of winter-spawning fishes of the Gulf of St. Lawrence (GSL), Canada, remains scarce due to a seasonal ice cover that prevents ichthyoplankton sampling using conventional methods. Two of those winter-spawning species, the Atlantic halibut (Hippoglossus hippoglossus) and Greenland halibut (Reinhardtius hippoglossoides), support the most important groundfish fisheries of the region. In March 2020, we captured 10 halibut larvae of size ranging between 5 and 14 mm through an opportunistic survey in the GSL onboard an icebreaker vessel. However, the morphological identification to the species was not possible due to the lack of knowledge on morphological characteristics of early larvae for these species, so we proceeded to genetic analysis to confirm species identity. This effort constitutes a first step for validating the putative spawning areas for those two important stocks in the GSL, a key aspect for the conservation and sustainable management of these fisheries.

• Theme: Larval Assemblages
• Authors: Gregor Boerner, Anna Akimova, Romain Frelat, Cindy van Damme, Myron A. Peck, Marta Moyano
• Title: The impact of the zooplankton size structure on foraging and growth of early herring larvae in the North Sea

 

Implementing additional plankton sampling on routine fisheries assessment cruises offers a unique opportunity to monitor concurrent changes of zoo- and ichtyoplankton. We analyzed plankton data collected in the North Sea in September and December between 2013 and 2019 during the International Herring Larval Survey. Different image analysis techniques (FlowCam, ZooScan) were combined to cover the size range between 55 to >1000 µm. Principle component analysis (PCA) and redundancy analysis (RDA) were applied to investigate the spatio-temporal changes in abundance and size of the plankton community. Our results show that changes across the size spectra are not synchronous, and we identified salinity in September and temperature in December to be the main drivers. Our results contribute to a better understanding of the fluctuations in larval fish prey composition as well as biomass, and provide useful estimates for modelling approaches investigating its impacts on larval growth and survival.

• Theme: Larval Assemblages
• Authors: Shannan C McAskill, Stormy Paxton, Simon J Geist
• Title: Trophic niche partitioning of three larval Sciaenidae species in the North-western Gulf of Mexico

 

Trophic interactions of larval fish play an important role in determining survivorship. To understand trophic niche partitioning and the potential for competition, we analyzed digestive tract content of three closely related, co-occurring, sciaenid fish species: Cynoscion nothus, Larimus fasciatus, and Micropogonias undulatus. Larvae were collected in the Gulf of Mexico off Galveston, TX in October/November 2017. Diet composition was analyzed between three ontogenetic development stages and two sampling locations (nearshore vs mid-shelf). Copepoda dominated all larval diets. Corycaeidae and Paracalanidae were the two most important families and mainly responsible for observed ontogenetic dietary shifts for all three species. However lesser consumed prey like Harpacticoida, Ostracoda and Chaetognatha were responsible for dissimilarities between the species. In C. nothus, distance to shore impacted the timing and number of ontogenetic dietary shifts, with larvae at nearshore stations undergoing dietary shifts at an earlier development stage compared to larvae at mid-shelf stations.

• Theme: Larval Assemblages
• Authors: April E. Simmons*, Allyse Ferrara, Solomon David, Quenton Fontenot
• Title: Comparison of larval and juvenile fish assemblage between newly created marsh terrace habitat and existing marsh habitat

 

Louisiana has lost roughly 25% of coastal lands since 1932 and is vulnerable to continued coastal land loss from anthropogenic activities and natural disasters. To remediate these losses, marsh terracing is used to restore open water habitat for aquatic species. Marsh terraces have a high edge to area ratio with an extended littoral zone potentially creating high quality nursery grounds. I assessed the temporal and spatial use of newly created marsh terrace habitat and existing marsh habitat by larval and juvenile fish in Chauvin, Louisiana using quatrefoil light traps deployed every other week from April to September 2019 and March to September 2020. In 2020, assemblages and habitat characteristics were similar between the terrace and marsh habitat. Results indicated that marsh terraces produced nursery grounds that were similar to natural marsh thus supporting the use of terraces in degraded estuary systems.

• Theme: Larval Assemblages
• Authors: Whitney JL*, Gove JM, McManus MA, Lecky J, Smith KS, Neubauer P, Phipps JE, Contreras EA, Kobayashi DR, Asner GP.
• Title: Ocean Oases: Surface slicks are pelagic nurseries for larval coral reef, epipelagic & deep-water fishes.

 

The survival and transport of marine fish larvae are expected to be tightly coupled to oceanic features. But, for the majority of marine species we have a poor understanding of where larvae go and what pelagic habitats they use. Therefore, we surveyed surface-dwelling zooplankton and ichthyoplankton communities inside and outside of surface slicks along the coast of Hawai‘I Island. Here, we provide evidence that surface slicks, a ubiquitous ocean convergence feature, provide nursery habitat for more than 100 species of commercially and ecologically important fishes from diverse ocean zones. Our work shows that slicks are oases for food and shelter in an otherwise fluid desert. By providing these survival advantages, slicks enhance larval supply and replenishment of adult populations from coral reef, epipelagic, and deep-water ecosystems. Our findings suggest that slicks play an underappreciated, yet critically important role in enhancing ecosystem and fisheries productivity in tropical marine systems.

• Theme: Commercial & ornamental aquaculture
• Authors: Brogan E. Holcombe, Savannah Lilyhorn, Danielle M. Contrada, Jennifer C. Dawson, Sydney Dennis, and Paul A. Anderson*
• Title: A Framework for the Selection of Marine Aquarium Fishes to Target for Aquaculture

 

Currently, only 5% of marine aquarium fish species traded in the U.S. are aquacultured. This study presents a data-driven framework to empower the selection of species to target for aquaculture research and development. The framework is based on species-specific data for 105 of the top 130 imported species into the U.S., including market characteristics (aquarium suitability, number of imports, retail price), aquaculture practicality (demersal/pelagic spawning strategy, pelagic larval duration, size at hatch) and conservation assessment (aquacultured status, ecological niche, geographical distribution and mid-depth). A principal components analysis (PCA) illuminates the relationships among these characteristics. Results highlight 36 species that cluster into groups which are not yet commercially available as aquacultured and merit investment in aquaculture research and development.

• Theme: Commercial & ornamental aquaculture
• Authors: Jessie Castanier*, Andrew Fields, John Scarpa, Simon Geist, David Portnoy
• Title: Public Aquariums as a Potential Source of Marine Fish for Exhibits and Conservation - Identification of Eggs and Larvae

 

The global ornamental fish trade is valued at an estimated $348M per year. The marine aquarium trade is highly dependent on wild sources of reef fishes. Marine fish populations and reef ecosystems are threatened by overexploitation and harmful collection techniques. Aquariums can provide an alternative source of ornamental fishes through rearing of eggs and larvae from volitional spawning. Pelagic eggs and early-stage larvae in the Coral Reef (CR) exhibit at the Texas State Aquarium, Corpus Christi, TX (TSA) were photographed, measured, and morphologically analyzed. Bicolor damselfish (Stegastes partitus) larvae from the CR exhibit were identified by characteristic pigmentation and DNA barcoding. Early-stage identification of eggs and larvae in mixed species tanks will provide a foundation for determining and implementing specialized larval culture techniques of target species. Further research will strengthen the capacity of TSA and other public aquariums in supporting and providing outreach for sustainable aquaculture and fisheries.

• Theme: Commercial & ornamental aquaculture
• Authors: Venturelli, P*; Blevins, T; Hawkins, S; McCord, A; McDonald, Z; Minhinnett, S; Schwer, J; Teletchea, S; Teletchea, F*
• Title: Comparative biology of early life stages of over 300 temperate freshwater fishes based on an updated STOREFISH database

 

Teleosts exhibit the highest reproductive diversity of all vertebrates, but this diversity has not been extensively documented or analyzed - in part due to a lack of life history information. The STOREFISH (STrategies Of REproduction in FISH) was published in 2007, and then released online in 2020 to facilitate data visualization and utilization (www.storefish.org). The database contains information on up to 50 life history traits from ~1200 references for 80 freshwater, mostly European, species. In this presentation, we describe efforts to extend STOREFISH, and then reassess previous relationships between oocyte diameter, larval size, and temperature that were based on data from just 65 freshwater fishes. Students in the United States and France used data from nearly 800 references to increase the STOREFISH database to 7,442 records (55% increase) for 368 species (360% increase) and 41 families (116% increase). Data were from mostly North American species, and focused on 14 egg and larval traits (www.storefish.org/description). The increased sample size improved the strength of and insight gained from relationships between oocyte diameter, larval size, and temperature. We anticipate that this updated and expanded database will continue to grow, and be useful for freshwater biodiversity research, conservation, assessment, management, and aquaculture.

• Theme: Commercial & ornamental aquaculture
• Authors: Jeppe Have Rasmussen*, Rebekah Alice Oomen, Marta Moyano
• Title: FishSizer; A new software solution for efficiently sizing fish larva.

 

Larval growth rate is a fundamentally important life history trait directly linked to fish population productivity and persistence. Consequently, there is great interest in measuring larval length and width. Unfortunately, obtaining these measurements often involves extensive manual work and thus increased intra- and inter-observer variability. To lessen these issues through semi-automation, we have created a custom-made graphical user interface. Using edge-detection for segmenting larva images, the software automatically estimates length and width across taxa while considering curvature in the process. Special attention has been put on optimizing workflow: Input is any number of images and output is one file containing all parameters extracted. The graphical user-interface includes interactive windows for visual verification of automated parameter estimation, easy outlier detection, and additionally allows manual measurement using methods similar to pre-existing software. Testing on images of tuna and cod larva found a time saving of 66-78% compared to most commonly used software.

15:00 - 16:00

Come and meet Fridays poster presenters and speakers on Gatherly. The networking platform is ideal for asking questions informally, like you would do during a poster session or reception during a 'normal' conference. Your 'avatar' symbol lands in the Welcome Area and can then explore different floors and join colleagues and "huddles" for video-chats. Not sure, who will attend? Look for registered participants at the "Who will attend the LFC44?" tab.

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LFC44 strongly advises to read our Meeting on Gatherly guidelines before, to hopefully give everyone a satisfactory experience. You need to use Google Chrome as your browser for this. You should probably be where your best LAN/W-LAN connection is. Gatherly does not currently support phones or tablets. We strongly recommend using a screen of at least 11" size (laptop).

Over the past years, research on impacts of climate change on fish larvae has progressed from experiments using single stressors and global averages to more complex designs, incorporating multiple stressors, fluctuating conditions and accounting for local variability. This talk will give an overview and highlight recent work incorporating local conditions and variability and show how it can advance our understanding of the vulnerability of larval fishes to climate change.

• Theme: Climate change effects
• Authors: M. Conor McManus*, Joseph A. Langan, Richard J. Bell, Jeremy S. Collie, Grace Klein-MacPhee, Michael D. Scherer, Richard G. Balouskus
• Title: Spatiotemporal patterns in early life stage winter flounder highlight phenology changes and habitat dependencies

 

Decadal changes in marine species life history events are becoming increasingly important to identify under a warming climate, yet many long-term monitoring programs do not collect data at the resolution needed to identify them. We addressed these considerations for Narragansett Bay winter flounder by leveraging two ichthyoplankton monitoring programs: a spatially comprehensive survey across the Bay, and a longer time series centered in one of the Bay’s sub-estuaries. Using these data, we investigated a suite of research questions for a comprehensive spatiotemporal synthesis of early life stage winter flounder. We identified changes in larval phenology via earlier seasonal peaks in density through time. Results also indicated stable larval spatial patterns during a period of larval decline, as well as spatial coherence between larval and young-of-the-year stages. Our results highlight the importance of high spatiotemporal ichthyoplankton sampling to identify changes in phenology and site-fidelity for the historically significant marine flatfish.

• Theme: Climate change effects
• Authors: Johnson, D.W.
• Title: How ocean acidification may alter natural selection on larvae: A case study of California Grunion

 

In order to anticipate the long-term effects of Ocean Acidification, we need to know how selection will operate as seawater chemistry changes, and whether evolutionary changes will be quick enough to affect the dynamics of populations over the coming decades. In a study of California Grunion, we tested whether tolerance of OA conditions was related to larval size by rearing larvae in both ambient and high-CO2 conditions. We found that not only do larger larvae survive better in general, but the survival advantage of larger larvae was more pronounced under OA conditions. These results suggest that changes in seawater chemistry can change the functional form of natural selection on larval size. Model projections of responses to these changes in selection suggest that although larvae can evolve to become more tolerant of OA, evolutionary responses will slow, but not stop the long-term decline in population sizes expected under future climate change.

• Theme: Climate change effects
• Authors: Caroline Bouchard
• Title: Sailboats and fish larvae : a combo with the wind in their sails

 

Sampling fish larvae in remote and harsh environments like the Arctic is often complex and costly. As the number of research vessels operating in Arctic waters are limited and highly sought after, sailboats are increasingly being used as marine science platforms in the region. In this presentation, I will share my experience collaborating with past and upcoming sailboat expeditions and show some of the findings. For example, larval Arctic cod (Boreogadus saida) collected from the ATKA expedition in West Greenland in 2019 allowed to associate warm water with partial recruitment failures resulting from thermal stress to the eggs and larvae hatched late in the season. Paradoxically, climate change could have positive effect on Arctic cod larval survival, as in some fjords, glacial meltwater create a subsurface thermal refuge allowing the larvae to avoid sea surface temperature warmer than their thermal limit.

• Theme: Form, function, development
• Authors: Marianne Nyegaard* and Tom Trnski
• Title: A study of tiny shapeshifters: microCT scanning of a rare collection of Giant Sunfish larvae (Molidae, Mola alexandrini)

 

The heaviest teleosts in our seas, the ocean sunfishes (genus Mola) are extreme examples of fish evolution and specialisation. They are the world's most fecund vertebrate, yet spawning is poorly understood. The larvae are rarely found, and the early ontogeny is only cursorily described. The Australian Museum and CSIRO (Australia) fish collection hold in total 33 Mola specimens from eastern Australia, of 2 - 32 mm. This size range includes some of the smallest Mola specimens ever reported, and covers the transition from larva to the taxa-specific Molacanthus stage. In this presentation we ponder what this small number of specimens may reveal of sunfish spawning time and location. We further recap current knowledge of Molidae larval species identification, and how their large growth spectrum presented a challenge in early systematics. We also present preliminary results from microCT scanning of unstained larval specimens and experimental reconstruction using phase signal to enhance contrast.

• Theme: Form, function, development
• Authors: Goldyn Anne G. Aquino*, Patrick C. Cabaitan, David H. Secor
• Title: Movement of glass eel Anguilla marmorata (Anguilliformes: Anguillidae) exposed to different salinity levels

 

Temperate eels are well known to remain settled in marine habitats or move between different salinity habitats during their glass eel stage. This behavior is less described in tropical Anguillid eels. In this study, glass eels of Anguilla marmorata were collected from an estuary (5‰) near Cagayan River, northern Philippines for 30-minute individual and group behavioral experiments during wet and dry seasons. A. marmorata glass eels spent most of their time in freshwater followed by brackish water and seawater. Settlement was only observed in brackish water during group trials. Switching and settled behaviors were observed for both lone and clustered glass eels. These findings bring concerns on the increased fishing pressure of eels, water pollution, and quarrying which is concentrated in freshwater and estuarine habitats of the river.

Conservation comes in all forms. In the world of reef conservation, a focus on marine ornamentals (as opposed to food fish) is a critical element in the big picture. An approach to this challenge is addressed by Rising Tide Conservation (RTC). RTC focuses on creating techniques and technicians in aquaculture to produce sustainable solutions for marine ornamental fish. Through research funding, public education, and technology transfer, this program has been instrumental in a shift in both the display and aquarium hobby. While not the complete solution, aquaculture of marine species addresses one element of coral reef conservation. Advances regularly continue, but adoption and commercial production still need further development. Legislation and consumer awareness will continue to serve as drivers for this work.

• Theme: Climate change effects
• Authors: M Sswat*, C Ofelio, S Goldenberg, A Aguirre Velarde, F Rioual, MA Peck, C Clemmesen, M Moyano, U Riebesell
• Title: Effect of upwelling intensity and light regime on larval fish growth: a mesocosm study in the Humboldt Current System

 

The Humboldt Current System hosts the world's most productive fishery, due to the upwelling of nutrient-rich deep water boosting a short, efficient food chain from phytoplankton to small pelagic fish. However, the functional relationship between environmental conditions and biological productivity, is not yet properly established. The timing of nutrient supply and primary production, for instance, seem to be out-of-phase. This enigma may be explained by seasonal differences in light intensity and residence times of coastal water masses. Shifting upwelling dynamics under climate change may lead to ecosystem changes, which could affect the livelihoods of people regionally and the export of fisheries products. We investigated how upwelling intensity and light regime influence the growth and survival of fish larvae as end-consumers of a natural food chain in nine 30-m3 off-shore mesocosms. The plankton community developed for 19 days under different supplies of nutrient-rich deep water and two light regimes, before each mesocosm received 190 fish larvae (120 Anchovy E. ringens and 70 Peruvian grunt A. scapularis). The fish larvae now fed exclusively on the plankton community within each mesocosm and all survivors were caught 17 days after introduction. Larval survival and growth rates of the two fish species will be discussed in relation to changes in upwelling intensity and light regime with potential consequences for the ecosystem and economy in the Humboldt Current System.

• Theme: Climate change effects
• Authors: Marta S. Pimentel*, Catarina Santos, Maria Rita Pegado, Eduardo Sampaio, Pedro Pousao-Ferreira, Rui Rosa
• Title: Deleterious effects of the deadly trio (warming, acidification, and deoxygenation) on fish early ontogeny

 

The interaction between ocean warming, acidification, and deoxygenation is expected to affect much of marine biota over the coming years, potentially undermining ocean services. Nonetheless, no study has scrutinized the impacts of their interaction on fish early ontogenetic stages. We implemented a multi-factorial design to investigate the effects of ocean warming, acidification, and deoxygenation over an array of biological responses across the early development of the seabream (Sparus aurata). Deoxygenation was the main driver of negative impacts in the hatching success, survival, and routine heart rates of recently hatch larvae, being generally further exacerbated when warming and acidification co-occurred. Meanwhile, acidification was the only factor to induce a significant decrease in the proportion of phototactic larvae behaviour. The behavioural responses were found to be highly correlated with the other analysed features. Overall, our findings highlight the need to assess the concurrent impacts of multistressors in order not to underestimate their impacts and ecosystem-wide consequences when analysed alone, and to better predict future ecosystem responses to ocean changes.

• Theme: Climate change effects
• Authors: Lea J. Joly*, Jose-Luis Zambonino-Infante, Carolina Giraldo, Cedric L. Meunier
• Title: Can herring larvae cope with global changes (warming, acidification, food quality)? A multi-stressor experiments

 

The larval stage is for fish a period of high mortality, which largely determines the recruitment and sustainability of stocks. As such, it is crucial to investigate how fish larvae may be affected by global changes. We conducted a multi-stressor experiment to assess direct (OWA: Ocean Warming and Acidification) and indirect (change in food quality) effects of environmental changes on herring larval development. Individuals were reared in two contrasted abiotic environments (11°C*pH8.0 vs 14°C*pH7.6) crossed with two food treatments (regular vs enriched food in phosphorus and omega 3) for about 700 degree-days. Differences in size and in the expression of genes involved in the aerobic metabolism, growth and cellular stress response were observed for stage 3 larvae. Our results suggest that herring larvae are affected and challenged by projected global changes. Transposed to the natural environment with other stressors, the larval survival could therefore be negatively impacted.

• Theme: Climate change effects
• Authors: Katharina Alter* and Myron A. Peck
• Title: Ocean acidification but not elevated spring warming threatens a European seas predator

 

Ocean acidification may negatively affect marine ecosystems by influencing key members of food webs. The garfish is an important European seas predator and it remains unknown how garfish will be impacted by climate change. We reared garfish until hatch at present and future pCO2 levels within two daily warming regimes (natural spring warming and increased warming rate) and one constant high temperature. Survival decreased at both future pCO2 and the constant high temperature while the highest survival was observed at increased warming rate. The proportion of deformities increased with future pCO2 but not temperature. Hatch characteristics, heart rate, and critical thermal limits were not affected by pCO2 but temperature. Garfish benefit from climate-driven increases in rates of spring warming but not the concomitant increase in pCO2. Moreover, this piscivorous fish is more sensitive to pCO2 than its prey which may have implications for the trophodynamic structure of the food web.

• Theme: Climate change effects
• Authors: Ofelio, C.*, Moyano M., Sswat, M., Rioual, F., Moullec, F., Aguirre-Velarde, A., Peck, M.A.
• Title: Effects of temperature and prey density on growth, otoliths and thermal tolerance of lab-reared Peruvian anchovy larvae

 

The Peruvian anchovy (Engraulis ringens) supports the largest fishery worldwide. The recruitment of these stocks markedly shifts due to changes in temperature and prey density associated with the climate variability (e.g. El Nino Southern Oscillation). We investigated how temperature (14.5°C and 18.5°C) and prey conditions (low and high) impacted growth rate, otolith formation and critical thermal maximum and minimum (CTmax, CTmin) of Peruvian anchovy larvae reared in captivity. The age and growth of well-fed larvae at 18.5°C was well depicted in their otolith microstructure but otolith size was decoupled from fish size in poor-fed larvae and larvae reared at 14.5°C. The acclimatization influenced the thermal tolerance, with higher effect on CTmax than CTmin in larvae reared at 18.5°C compared to 14.5°C, suggesting their capability to acquire tolerance and gradually adapt to warmer temperatures. Our results provide a contribution to introduce in modelling projections and help to predict future changes in these valuable fisheries.

• Theme: Climate change effects
• Authors: João Almeida, Ana R. Lopes, Ana F. Lopes, Laura Ribeiro, Ana M. Faria*
• Title: Effects of acute and long-term exposure to warming on the escape response and aerobic scope of white seabream juveniles

 

The end of the larval phase, when larvae need to find an adequate habitat to settle, is considered a critical step, associated with high levels of mortality, mostly due to predation. It has been shown that increasing temperature can substantially impact behaviour and locomotor performance components of escape response in fish, but few studies have disentangled the acute sensitivity response, i.e., the degree to which a species is likely to respond to sudden changes in the environment, from the potential to compensate for thermal stress, through developmental plasticity. Here, we aimed at evaluating the effects of higher temperature on the escape response of late-stage larvae of white seabream, Diplodus sargus. Additionally, as elevated temperature might reduce aerobic metabolism, which in turn can affect individual fitness, we assessed aerobic scope. Larval fish were reared under two temperatures: ambient temperature (19ºC), and high temperature scenario, set to +3ºC, which reflects acute heating events and is in line with projected future climate change conditions. Escape responses and aerobic scope were measured immediately after high temperature was attained, and after 4 weeks. Results indicate that acute exposure to high temperature significantly affects fish escape response, while aerobic scope shows a tendency to be higher under warming conditions, although there is a high variability associated. Long-term exposure might suggest some developmental plasticity.

• Theme: Form, function, development
• Authors: Ralf Friedrich Schneider*, Joost M Woltering, Dominique Adriaens, Olivia Roth
• Title: Comparative analysis of the embryogenesis of three syngnathids provides insights into the development of these fishes

 

Syngnathids are an astonishingly diverse group among teleosts and throughout the last decades this diversity motivated numerous studies addressing, for example, their phylogenetic relationships, their skeletons’ functional morphology, and the genomic underpinnings of specific phenotypes. However, studies exploring syngnathid early development remain scarce and often lack detail in this challenging model system. Our study describes the development of Nerophis ophidion, Syngnathus typhle and Hippocampus erectus from hours post fertilization to birth and beyond. A staging table facilitates comparative analyses, specifically of the chondro-, osteo- and myogenic development. We show that although very early development is similar, later ossification varies markedly among species, as does muscle development. Furthermore, different syngnathid fin phenotypes can be linked to paedomorphism or the entirely abortion of developmental programs. By elucidating syngnathid development in detail, this research sheds light on the processes that led to some of the iconic characteristics observed in this taxon.

• Theme: Form, function, development
• Authors: Thieme, Philipp*
• Title: Caudal-fin skeleton of atherinomorphs: Development reveals Convergences

 

Within Atherinomorpha different configurations of the caudal-fin skeleton can be observed. These range from highly complex conditions to rather simplified ones. To determine the homology of the skeletal elements between atherinomoph taxa, it is not sufficient to solely rely on adult specimens, but necessary to study their development. Therefore, we examined ontogenetic series of multiple atheriniform, beloniform and cyprinodontiform species to follow the development of the caudal-fin skeleton. Subsequently, similarities and differences in terms of which structures are formed and which structures fuse during ontogeny were determined. The development of the hypurals revealed a high variation of fusions within different taxa, while two modes of formation of the compound centrum were observed. Additionally, we reconstructed the grundplan of the developmental patterns of the caudal-fin skeleton of atherinomorphs and its subtaxa. The results showed a high congruence between extant atheriniforms and the last common ancestor of all atherinomorphs.

• Theme: Recruitment processes
• Authors: Madeline Tomczak*, Brian Schmidt, Robin L. DeBruyne, Dustin Bowser, Jason L. Fischer, Gregory W. Kennedy, Nicole King, Christine M. Mayer, Edward F. Roseman
• Title: Retention and Collection Efficiency of Egg Mats

 

Benthic egg mats can provide a spawning index for lithophilic spawning fishes, although collection efficiency and bias is unknown. We conducted a literature review of egg collection methods to evaluate gear biases based on species, waterbody, and gear design. We also conducted experiments using lake whitefish (Coregonus clupeaformis) and walleye (Stizostedion vitreum) eggs in flume tanks to quantify retention and assess capture efficiency, followed by field-based egg sampling. Of 57 studies reviewed, 28 used egg mats with identified limitations and biases including clogging with sediment, egg predation, and dislodging of eggs. Our lab and field observations indicate using egg mats may be biased due to differing retention and capture efficiencies compared to natural substrate, and biases vary between species. Compared to other egg collection gears, egg mats are informative for assessing egg deposition by lithophilic spawning fishes, but species and habitat specific gear biases may need to be considered.

• Theme: Recruitment processes
• Authors: Corinne Burns*, P. Pepin, G. Veillet, S. Plourde, P. Sirois, D. Roberet
• Title: Identifying Physical Oceanographic Variables Driving Larval Redfish (Sebastes sp.) Growth in the Gulf of St. Lawrence

 

Fast larval growth has been shown to increase a larva’s chance of survival to recruitment, however species-specific drivers of growth are often unknown. We aimed to describe environmental effects on recent growth of larval redfish (Sebastes sp.) in the Gulf of St. Lawrence (GSL). Otolith microstructure from larvae was analyzed and compared with local environmental conditions at the time of collection. There were no significant correlations between recent larval growth and sea surface temperature. Recent growth was however positively correlated with a water stratification index in larvae older than 8 days post-extrusion only. Strong stratification likely increases small-scale densities of potential larval fish prey and larval feeding success, which may explain the faster growth at these stations. Next, time series analyses will be used to determine whether physical variables, like water stratification, and biological variables, such as abundance of key prey taxa, are drivers of redfish recruitment in the GSL.

15:00 - 16:00

Come and meet Saturdays speakers and Network Hour with ELHS mentors on Gatherly. The networking platform is ideal for asking questions informally, like you would do during a poster session or reception during a 'normal' conference. Your 'avatar' symbol lands in the Welcome Area and can then explore different floors and join colleagues and "huddles" for video-chats. Not sure, who will attend? Look for registered participants at the "Who will attend the LFC44?" tab.

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LFC44 strongly advises to read our Meeting on Gatherly guidelines before, to hopefully give everyone a satisfactory experience. You need to use Google Chrome as your browser for this. You should probably be where your best LAN/W-LAN connection is. Gatherly does not currently support phones or tablets. We strongly recommend using a screen of at least 11" size (laptop).

• Theme: Commercial & ornamental aquaculture
• Authors: Jonathan Lee*, Matt Cook, Adam Luckenbach, Barry Berejikian, Crystal Simchick, Rick Goetz
• Title: Temperature effects on larval sablefish (Anoplopoma fimbria)

 

In marine finfish aquaculture, the daily costs of larval rearing exceed any other life stage. Increased temperatures may speed development and shorten the larval stage, but other unintended effects may result. We reared sablefish larvae at 12, 15, or 18°C. After larval temperature exposures, body size increased with temperature, but survival peaked at 15°C. After the larval stage, fish were reared at a common ambient temperature. After nine months, growth and survival were highest for fish previously reared at 15°C. Eight months after exposures, each treatment had a higher prevalence of a different deformity. Spinal deformities had the most-negative growth impacts and were most prevalent at 12°C. Flesh nine months after exposures was softer at 15°C, but likely undetectable by consumers. Phenotypic sex matched genetic sex, suggesting that sex was not altered by rearing between 12 to 18°C. These results inform aquaculture methods and may help predict climate change effects.

• Theme: Commercial & ornamental aquaculture
• Authors: Casey A. Murray*, Nathan D. Evans, Sarah W. Hutchins, Fred A. Shopnitz, Cortney L. Ohs, Joshua T. Patterson, Angela B. Collins, Matthew A. DiMaggio
• Title: Developing larval culture protocols for hogfish (Lachnolaimus maximus) to minimize the use of live feeds

 

Hogfish (Lachnolaimus maximus) are large reef-dwelling wrasses endemic to Florida and the Caribbean that are popular targets for commercial and recreational fishers. Fishing pressure has led to increased management and concern regarding population status over the past several decades. Aquaculture of this species would allow for commercial production to meet market demands while also creating opportunities for stock enhancement, however commercial culture protocols for L. maximus have yet to be developed. Larval digestive development and physiology was examined to discern appropriate feeds and timing of feed transition. In a series of experiments, the earliest points at which larval L. maximus could be transitioned from copepods to rotifers and from rotifers to an inert microdiet were determined. Survival and total length were greatest when rotifers were offered at first feeding compared to later in the larval period and microdiet should be introduced after metamorphosis.

• Theme: Commercial & ornamental aquaculture
• Authors: Daniel Hardin*, Ivonne R Blandon, Simon J Geist
• Title: Metabolic Rate Responses to different Salinity levels in Reared Larval Spotted Seatrout

 

We studied the metabolic response of estuarine-dependent larval Spotted Seatrout to changes in salinity levels during their first month of life. Spawning occurs in shallow estuaries where environmental factors have profound effects on salinity, making it a challenging environment for larval fish as they shown greater sensitivity and are less capable of regulation. Spawns were provided by two Texas Parks and Wildlife Department (TPWD) Coastal Fisheries Stock Enhancement Program (SEP) hatcheries and reared at the TPWD Marine Development Center. Metabolic rate experiments were conducted using Loligosystems Microplate closed respirometers. Standard SEP rearing conditions were used as a midpoint for experimentation, with upper and lower bounds of salinity established based on organismal tolerance and expected estuarine conditions. Testing groups were then exposed to these conditions slowly, before being held for 72 hours prior to testing. Preliminary data analyses suggest a positive correlation of salinity and metabolic energy requirement for this species.

• Theme: Recruitment processes 
• Authors: April Hugi, Frank Hernandez
• Title: Trophic Ecology of Billfish Larvae in the Gulf of Mexico: An Analysis of Diet and Prey Availability and Predator Growth

 

The Gulf of Mexico is an important spawning and early life habitat for billfishes, whose larvae experience high growth rates despite living in offshore, oligotrophic waters. Using samples collected in 2019, the goals of this study were to examine the relationships between zooplankton prey (abundance and quality) and larval billfish growth, and to identify the environmental drivers that influence larval billfish trophic dynamics. Our results indicate that billfish larvae are highly selective predators; poecilostomatoid copepods and Evadne spp. cladocerans comprised 100% of the diet for preflexion larvae. However, feeding niche expanded throughout larval ontogeny to include larger prey items (calanoid copepods, larval fish). With respect to available zooplankton prey, billfish larvae showed significant positive selection for Evadne spp. and female Farranula spp. Variability in larval billfish growth estimated by otolith increment analysis will be examined in relation to diet, fatty acid profiles of prey species, and environmental variables.

• Theme: Recruitment processes
• Authors: Michael Bode, Severine Choukroun, Michael Emslie, Nina Gerber, Hugo B Harrison, Jeffrey M Leis*, Luciano B Mason, David H Williamson, Geoffrey P Jones
• Title: No-take zones of the Great Barrier Reef provide most of the larval supply of Coral Grouper to fished areas

 

Marine reserve networks can deliver impressive increases in local abundance of exploited species, but the magnitude of larval supply beyond reserve boundaries has not been quantified. Australia's Great Barrier Reef's (GBR) no-take marine reserve (NTMRs) network covers ~30% of reef habitat. We calculated the NTMR's to contribution to reproductive output, larval supply, and commercial catch, for the GBR's most important, and well managed, fishery (Coral Groupers - Plectropomus spp). GBR NTMRs contain half of Coral Grouper biomass, and 52% of reproductive output. Using extensive data on stock biomass, size distributions, larval dispersal, and commercial catches, we show that NTMRs provide 51% of GBR larval supply, including 61% of supply into NTMRs themselves and 47% into fished areas. Based on the present commercial catch distribution, this translates to 46% of fishery yield. Larval dispersal is estimated with a validated biophysical model (GBR-Larvo), which includes larval swimming, orientation and vertical distribution behaviour.

• Theme: Recruitment processes
• Authors: Juan Cao*, Fei Cheng, Songguang Xie
• Title: Confirmation of recovery distances of the Three Gorges Dam by larval fish assemblages in the Yangtze River

 

Based on the Serial Discontinuity Concept, we tested the recovery distances of the Three Gorges Dams (TGD) on a finer scale. Same approaches were applied to collect larval fishes and environmental variables at 11 sites along 1139 km length mainstem from downstream of TGD monthly through April to August in 2018. 59 taxa were identified, ranged from 1 to 23, and larval density was 98.02±299.03 ind./100m3 (means±SD), ranged from 3.77E10-3 to 20.43E10+2 ind./100m3 through the sampling period. Abundances showed gradient variations (from 2.08±3.60 to 32.61±37.43 ind./100m3 with distance increase) and dramatic increases at confluence entrances of tributary (51.14±59.51,521.35 ±768.77, and 136.97±146.50 ind./100m3). Inferred recovery distances of TGD were variable from different variables, and extended to almost 800 km based on larval abundance. Our results confirmed the recovery distances of TGD and effects of tributaries on the distance, promoting better understanding on fish recovery process under dam impacts.

• Theme: Recruitment processes
• Authors: Charles Hinchliffe*, Pierre Pepin, Iain M. Suthers, Daniel S. Falster
• Title: A novel approach for estimating growth and mortality of fish larvae

 

Accurate estimates of growth and mortality are needed to understand drivers of production and cohort success. Existing methods for estimating mortality rates, such as catch-curves, require large sample sizes, as they work by grouping individuals into age bins to determine a frequency distribution. Yet, sampling enough larvae is often not possible at fine scales within the constraints of research projects, due to low density of larvae in pelagic environments. Here, we develop a novel method to simultaneously estimate growth and mortality rates of fish larvae as a continuous function of size using theory of size-structured populations, eliminating the need to group data into age bins. We compare the effectiveness of our model to existing methods by generating data from a known distribution. This comparison demonstrates, that while all models recover correct parameter values under ideal circumstances, our new method performs better than existing methods when sample sizes are low.