Contributed Session.
Lead Organizer: Mariana Hill Cruz, GEOMAR Helmholtz Centre (mhill-cruz@geomar.de)
Co-organizers:
Shannon Powers, University of South Carolina (sp62@email.sc.edu)
Presentations
04:30 PM
Potential southern flounder spawning locations identified with particle dispersal modeling (9724)
Primary Presenter: Brian Bartlett, East Carolina University (bartlettbr24@ecu.edu)
Historically, southern flounder (Paralichthys lethostigma) is one of North Carolina’s most valuable finfish fisheries. Despite this, the species is managed without knowledge of its spawning location making it difficult to determine an appropriate spatial scale for management. Southern flounder is regulated at the state level, despite evidence that a single genetic population exists from Virginia to Florida. In addition to current management challenges, southern flounder has experienced a long-term recruitment decline, which became more pronounced around 2007. Currently, little data exist for southern flounder spawning events. Here, potential spawning locations of southern flounder are identified using Lagrangian simulations that backtrack larval particles collected near Beaufort Inlet in North Carolina. Backtracking simulations are conducted using the Connectivity Modeling System (CMS) forced by ocean circulation fields generated by a global earth system reanalysis and then a ROMS model. Simulations reveal a large range of potential spawning locations exist for southern flounder. However, in all years analyzed and under both models, the highest probability of spawning occurred in southern Onslow Bay, NC. There is also evidence that some larvae may originate from other states, such as off the coasts of Georgia and Florida. This suggests that genetic homogeneity may result from infrequent, long-distance dispersal. These results provide useful insights on the primary spawning grounds of southern flounder, which can help to support better spawning stock biomass assessments.
04:45 PM
LINKING LARVAL TEMPERATURE TOLERANCE IN THE LAB TO SETTLEMENT AND PERFORMANCE IN THE FIELD IN THE AMERICAN LOBSTER (9305)
Primary Presenter: Eric Annis, Hood College (annis@hood.edu)
American lobster (Homarus americanus) populations in the Gulf of Maine are settlement driven and our research focuses on how temperature tolerance of planktonic larvae shapes patterns of settlement. We defined physiological thresholds of thermal tolerance for the planktonic postlarval stage through laboratory experiments quantifying growth and mortality, scope for activity and gene expression. We related these thresholds to performance in the field by deploying wild postlarvae in cages at depths of approximately 10, 40 and 80 m for two months and quantifying settlement over the same depth range. Mean bottom temperature for caged larvae was 9 °C at 80 m and 14 °C at 10 m and was well within the critical temperature range of 4-27 °C determined in our laboratory assays. Mortality was less than 5% at all depths. However, larvae deployed at 80 m for two months had significantly reduced carapace length and molt increment than those deployed at 10 m. Larval settlement in the field decreased significantly with depth and decreasing temperature, and was 60-fold lower at 80 m than at 10 m. Our results suggest larvae can successfully settle across the entire depth range sampled but sublethal effects may provide a selective pressure to settle in shallower, warmer depths. Moreover, there is an apparent disconnect between physiologically defined thermal tolerance and the vertical distribution of settlement in the field. The proximate determinate of depth of settlement is likely due to behavioral rather than physiological responses to decreasing temperature with depth.
05:00 PM
Icefish age groups and growth. (9691)
Primary Presenter: Ryszard Traczyk, AFS (ryszardtraczyk@gmail.com)
Until recent decades, Antarctic resources were regarded to belong to no one and, therefore, were harvested without restrictions. This exploitation ultimately led to the near-complete exhaustion of economically valuable Antarctic animals. The process began with the largest whale species, followed by seals, smaller whale species, porpoises, penguins, large species of icefish and now krill. At present further exploitation is planned and administered sustainable fishery which needs to be based on estimations of all age groups of fish. However, that is difficult to the obtain, because of inaccessibility of the icefish’s habitat of sharp rocky peaks and the larger shelf depths. Unique icefish biology determine age estimation only from otoliths (lack of scales and bone reduction). However interpretation of annual otolith increments performed by specialists from around the world provided very different estimates of the age groups in the range of 1 to 17 years with an error of 8 ys for the same otolith. Manual accounting of 2000 daily increments in 2 mm otoliths radius is terrified too. Therefore, I performed detailed studies of Ps. georgianus, Chaen. aceratus and Champ. gunnari otolith microstructures to determine how and why they form and to relate particular patterns and composition to growth, age groups, and life histories. Icefish ages were automatically estimated from daily increments in otoliths that were verified with age estimation for large ichthyologic samples by the modal frequency of otolith mass time series to fit superimposed normal distributions of age group of juveniles and adults. They were verified also by age estimation from body lengths. The long time series data of icefish that were hatch every year in July-August-September and caught every year in December-January – in the same time and place since 1970 show separate age group at length by the length frequency analysis. Each age group constitute close neighbors in body length (TL) that have the same age and are larger than previous length group by one year increment of 6-10 cm of body until the smaller one was only preceded by 1.5 cm hatched larvae. We determined that maximum ages were 8 y for C. gunnari, 7 y for C. aceratus, and 6 y for P. georgianus. Sizes at first maturity were became smaller for icefish males than females in order to adaptation to vertical distributions. In upper waters C. gunnari females matured at about 32 cm and 5 y; in middle pelagic P. georgianus females matured at about 46.4 cm and 3.3 y; and in bottom adults C. aceratus females matured at about 61.5 cm and 5.6 y. C. aceratus females were 2.5 cm longer than males in age group 5 and in age groups 6 and 7+ we found only females. The females of the other two species averaged 2 cm longer than males among which sex size differences were smaller for C. gunnari. Older, larger fish can be hidden in the hilly rocky bottom and avoid bottom nets. The otolith masses and shapes of the three icefish species varied with their body morphologies and levels of bone and muscle reduction, that is the largest for bottom adults C. aceratus and lack for upper small C. gunnari. The relationship between body mass and total length varied by species, habitat occupied, thermal regime, diet, individual life histories, season, and growth rate. Icefish have responded to exploitation and climate change by different feeding strategies. The smaller, slender pelagic species, C. gunnari, has shifted their organizational level of feeding from individually to previously not know large pelagic swarms having larger encounter probabilities of pelagic schools of small krill and appropriate to warming decreased substantially in size at maturity. The largest benthic species, C. aceratus, has remained relatively large by remaining as adults in colder, deeper waters that have shifted from feeding on krill to feeding on large benthic animals. The size at maturity of the mid-sized, stocky semipelagic species, P. georgianus, has been reduced by reductions in ice-algae feeding Euphausia superba as a result of warming. Larger P. georgianus were found congregated at whirls that concentrated larger older krill driven from south cold Weddell Sea on east shelves where inshore is the spawning ground too and the smaller icefish migrated after hatch with along shore current to western shores having inflow from south of the fresh small krill after hatch in warmer South Shetland waters - that both different distributions further rely on changes in pressure systems and ice cover. Recently, abnormal otoliths have been observed, reducing their mass and shape (loss of edges, replacement of aragonite with lighter vaterite). Those deficiencies and defects correspond to the effects and nature of dioxin activity multiplied by their uptake and transport as oxygen through skin in icefish. Monitoring of dioxin concentration is difficult and costly, requires protection against the toxic effects. Thus, cheaper, safer methods of analyzing the natural signs of otoliths resulting from the influence of dioxins on icefish biology and existence are needed to reduce the risk of their destruction.
05:15 PM
A century of climate change and freshwater growth in juvenile sockeye salmon from Bristol Bay, Alaska (8948)
Primary Presenter: Emma Christman, University of Washington (echristm@uw.edu)
Lack of long data records currently impedes our understanding of how aquatic populations and ecosystems respond to ongoing climate change. An additional challenge is to understand how geographic context controls ecological responses to changing environmental drivers. Sockeye salmon in Bristol Bay, Alaska have become increasingly abundant over the last century as nursery lakes have warmed and become more productive. However, population responses are widely variable among the watersheds across the region. For example, the Nushagak River jumped from producing 5% of the Bristol Bay sockeye to nearly 20% in 2022, while sockeye populations in the nearby Wood River began increasing gradually in the 1980s. We hypothesize that the differences between these two river systems is a function of local watershed control on climate forcing and local ecological responses to warming lakes. The large, cold lakes that feed the Nushagak and Wood Rivers are oriented in a N-S pattern, with the Nushagak lakes located north of the Wood River lakes, and nearly 100km farther from the ocean. We analyzed a century-long (1917-2023) archive of sockeye salmon scales to reconstruct juvenile growth in fresh water to assess the lake-specific responses to warming climate. Preliminary results support the hypothesis that the sequential population response is attributed to landscape-filtered climate shifts that have positively affected salmon growth: that the natal lakes closer to the coast (Wood lakes) experienced a climate shift sooner than the inland lakes (Nushagak lakes).
05:30 PM
IMPACT OF CLIMATOLOGICAL EVENTS ON THE SPAWNING OF SONIFEROUS SCIAENIDS IN THE MAY RIVER ESTUARY, SOUTH CAROLINA (9704)
Primary Presenter: Makiah Mooney, Savannah State University (mmooney1@student.savannahstate.edu)
IMPACT OF CLIMATOLOGICAL EVENTS ON THE SPAWNING OF SONIFEROUS SCIAENIDS IN THE MAY RIVER ESTUARY, SOUTH CAROLINA Makiah Mooney, Dr. Amanda M. Kaltenberg, Alyssa Marian, Dr. Eric Montie The U.S east coast experiences various climatological anomalies. In the past decade, estuaries along the South Atlantic Bight have experienced hurricanes, tropical storms, temperature anomalies, and heavy rain events. Extreme climatological events like these are hypothesized to impact various estuarine fauna. This study investigated potential impacts of climatological events on the spawning season of soniferous fishes in the May River Estuary, South Carolina. Analysis of the call intensity of each soniferous sciaenid species was quantified from acoustic hydrophone data collected over the past 10 years at station 37M in the May River. Call intensity of each species was compared for years with a climatological event to adjacent years without an event. Results showed that call intensity of red drum were lower during a hurricane and increased again after the storm, suggesting that the hurricane could possibly impact their spawning season. All red drum chorusing in 2016 occurred before Hurricane Matthew struck the area, but no chorusing was observed afterwards. However, chorusing did occur immediately following Hurricane Irma in 2017. A cold summer period was observed in 2020, but did not notably impact the summer spawning season of spotted seatrout. The number of summer chorusing events in 2020 was similar to the number of chorusing events in other years. Additional ongoing analyses on the potential impact between climatic events and soniferous sciaenids will improve our understanding of how a changing climate may impact estuarine ecosystems.
05:45 PM
Fish kill lessons and data needs: a spatiotemporal analysis of citizen fish kill reports in coastal SW Florida (9497)
Primary Presenter: Edna Fernandez-Figueroa, University of Tampa (efernandezfigueroa@ut.edu)
Fish kill events threaten aquatic life, local economies, and human health worldwide. However, due to their unpredictable and often short-lived nature, information about fish kill spatiotemporal trends, as well as the species composition and abundance of carcasses, remains limited. In coastal SW Florida, fish kill events are frequent, but much of what we know is based on citizen reports to the Florida Fish Kill Hotline and fisher experiences. This study aimed to identify spatiotemporal patterns of fish kill events in coastal SW Florida from 2010 to 2022 by analyzing open access Florida Fish Kill Hotline reports, red tide-related manatee mortality cases, and environmental monitoring data. Additionally, fish categories identified in Fish Kill Hotline reports were compared to carcass enumeration surveys conducted by the authors during a fish kill event in Tampa Bay, Florida, in July 2021. The results of the 2010-2022 dataset analysis indicate that Fish Kill Hotline reports were useful in identifying the location and duration of fish kills. The number of reports has also increased over the past 12 yr, particularly during the warmer summer months. However, Fish Kill Hotline reports were spatially biased and did not provide carcass enumeration results. Additionally, Fish Kill Hotline reports mainly included recreational fish groups, whereas enumeration surveys indicated the abundance of pinfish Lagodon rhomboides and demersal fish. These findings highlight the need for resources that enable citizens to accurately identify and enumerate carcasses accurately.
CS07 - Fish and Fisheries
Description
Time: 4:30 PM
Date: 28/3/2025
Room: W206B