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News Article | February 28, 2017
Site: www.eurekalert.org

A new analysis of population trends among coastal sharks of the southeast U.S. shows that all but one of the seven species studied are increasing in abundance. The gains follow enactment of fishing regulations in the early 1990s after decades of declining shark numbers. Scientists estimate that over-fishing of sharks along the southeast U.S. coast--which began in earnest following the release of Jaws in 1975 and continued through the 1980s--had reduced populations by 60-99% compared to un-fished levels. In response, NOAA's National Marine Fishery Service in 1993 enacted a management plan for shark fisheries that limited both commercial and recreational landings. Now, says lead scientist Cassidy Peterson, a graduate student at William & Mary's Virginia Institute of Marine Science, "We've shown that after over two decades of management measures, coastal shark populations are finally starting to recover and reclaim their position as top predators, or regulators of their ecosystem. Our research suggests we can begin to shift away from the era of 'doom and gloom' regarding shark status in the United States." Joining Peterson in the study, published in the latest issue of Fish and Fisheries, were VIMS professor Rob Latour, Carolyn Belcher of the Georgia Department of Natural Resources, Dana Bethea and William Driggers III of NOAA's Southeast Fisheries Science Center, and Bryan Frazier of the South Carolina Department of Natural Resources. The researchers say their study--based on modeling of combined data from six different scientific surveys conducted along the US East Coast and in the Gulf of Mexico between 1975 and 2014--provides a more accurate and optimistic outlook than previous studies based on commercial fishery landings or surveys in a single location. "Data from shark long-lining operations or shark bycatch can be suspect," says Peterson, "because what looks like a change in abundance might instead be due to changes in fishing gear, target species, market forces, or other factors." Research surveys are scientifically designed to remove these biases. Survey crews purposefully sample a random grid rather than visiting known shark hot spots, and strive to use the exact same gear and methods year after year to ensure consistency in their results. But even with these safeguards, data from a single survey often aren't enough to capture population trends for an entire shark species, whose members may occupy diverse habitats and migrate to different and far-flung areas depending on age and sex. "Because many shark species undergo vast migrations and have complex life cycles," says Peterson, "it's not uncommon for results from different surveys to conflict. Producing an estimate of total abundance requires combining data from different surveys--sometimes from several states or even countries--and applying intricate stock-assessment models." For the current study, the scientists combined data from six different shark surveys: the VIMS Longline Survey, the SouthEast Area Monitoring and Assessment Program's South Atlantic Coastal Trawl Survey, the South Carolina Coastal Longline Survey, the Georgia Red Drum Longline Survey, the Southeast Fisheries Science Center's Longline Survey, and the Gulf of Mexico Shark Pupping and Nursery Area Gillnet Survey. "Our study represents the most comprehensive analysis of patterns in abundance ever conducted for shark species common to our area and the Southeast coast," says Latour, who directs the longline survey at VIMS. Established in 1973, it is the world's longest running fishery independent monitoring program for sharks, skates, and rays. By pooling and modeling data from all six surveys, the researchers were able to estimate population trends for seven of the region's most common coastal species: the large-bodied sandbar, blacktip, spinner, and tiger sharks, and the smaller Atlantic sharpnose, blacknose, and bonnethead sharks. The results of the analysis were clear, says Peterson. "All the large-bodied sharks showed similar population trends, with decreasing abundance from the mid-1970s to the early 1990s, then a multi-year period of low abundance, and recent indications of recovery from past exploitation." All but one population of small coastal sharks also increased in abundance. The exception was blacknose sharks in the Gulf of Mexico, which decreased from the onset of records in 1989 until the study's end in 2014. This species is known to be susceptible to by-catch within the trawl fishery for Gulf shrimp. The blacknose population along the Atlantic coast of the southeast U.S. actually increased during the same period. The overall population trends make biological sense, says Latour. "The large-bodied species saw the greatest initial declines, both because they were highly sought by anglers, and because they mature late and produce relatively few pups. Their slow growth rate also helps explain the pause in their recovery following the onset of fishing regulations in the early 1990s." The smaller shark species, whose higher growth rates make them less susceptible to fishing pressure, saw lesser declines and more rapid recoveries. The team also found a correlation between shark numbers and both fishing pressure and large-scale climatic patterns. Funding for the study was provided by NOAA Fisheries, the NMFS Highly Migratory Species Office, the Atlantic States Marine Fisheries Commission, the South Carolina Saltwater Recreational Fishing License Funds, and the Federal Assistance for Interjurisdictional Fisheries Program.


Gruss A.,Southeast Fisheries Science Center | Gruss A.,University of Miami | Drexler M.,University of South Florida | Ainsworth C.H.,University of South Florida
Fisheries Research | Year: 2014

Spatial ecosystem models, such as OSMOSE, have become integral tools in achieving ecosystem-based management for their ability to thoroughly describe predator-prey dynamics in a spatially explicit context. Distribution maps, which define the initial spatial allocation of functional groups abundance, can have a large effect on the predator-prey dynamics that spatially explicit ecosystem models simulate. Here, we introduce the delta GAM approach we developed to be able to produce distribution maps for an OSMOSE model of the West Florida Shelf (Gulf of Mexico), OSMOSE-WFS. This delta GAM approach predicts the spatial distribution of different life stages of the multiple functional groups represented in OSMOSE-WFS ('life-stage groups') at different seasons, over the entire Gulf of Mexico (GOM) shelf including areas where abundance estimates do not exist, using different research survey datasets and regional environmental and habitat features. Our delta GAM approach consists of fitting two independent models, a binomial GAM and a quasi-Poisson GAM, whose predictions are then combined using the delta method to yield spatial abundance estimates. To validate delta GAMs, bootstraps are used and Spearman's correlation coefficients (Spearman's ρ's) between predicted and observed abundance values are estimated and tested to be significantly different from zero. We use pink shrimp (Farfantepenaeus duorarum) to demonstrate our delta GAM approach by predicting the summer distribution of this species over the GOM shelf and the West Florida Shelf. Predictions of the delta GAM reflect existing empirical research related to pink shrimp habitat preferences and predictions of a negative binomial GAM previously designed for the GOM. We find that using a delta rather than a negative binomial GAM saves significant computation time at the expense of a slight reduction in GAM performance. A positive and highly significant Spearman's ρ between observed and predicted abundance values indicates that our delta GAM can reliably be used to predict pink shrimp spatial distribution. Spearman's ρ was also positive and highly significant in every life-stage group represented in OSMOSE-WFS and season, though often low. Therefore, delta GAMs fitted for the different life-stage groups and seasons correctly predict qualitative differences between low- and high-abundance areas and are deemed appropriate for generating distribution maps for OSMOSE-WFS. The delta GAM approach we developed is a simple, convenient method to create distribution maps to be fed into spatially explicit ecosystem models, where wide spatial and taxonomic coverage is desired while benefits of high precision estimates are lost at run-time. © 2014.


Gruss A.,Montpellier University | Gruss A.,University of Miami | Gruss A.,Southeast Fisheries Science Center
Aquatic Living Resources | Year: 2015

Marine protected areas (MPAs) are increasingly being considered and used for the management of fisheries targeting mobile fish populations. Here, the recent modelling literature on MPA effects for mobile fish populations and their fisheries is reviewed. Modelling studies conducted since 2011 have filled a considerable number of knowledge gaps on the impacts of MPAs for species exhibiting home-range behaviour, nomadic movements or behavioural polymorphism, and on the effects of "targeted MPAs", which aim to protect relatively small areas where migratory fishes spend an inordinate fraction of time or are highly vulnerable to fishing (e.g., nursery or spawning zones). Also, in recent years, two studies investigated the consequences of MPAs targeting highly migratory (tuna-like) fish populations for the first time in the history of MPA modelling. Recent modelling studies found that MPAs aimed at protecting mobile species may have positive conservation eff ects under a relatively wide range of situations, but may generate long-term fisheries benefits only under a very limited set of conditions. In particular, MPAs were not found to be beneficial for the fisheries targeting highly migratory populations. Strategies producing both conservation and fisheries benefits were identified, which depend on fish movement patterns and numerous aspects of fish life history and fisheries dynamics. However, in view of the diversity of fish movement patterns in MPA systems and current dynamics in resource management, it is clear that additional modelling work is needed to fully understand how protected areas aff ect mobile fish populations and their fisheries and to be able to implement pertinent MPAs. In particular, future modelling studies should systematically assess the effects of MPAs in relation to other management tools to find strategies that are most eff ective in meeting management objectives, and explore the impacts of "dynamic" MPAs that follow highly migratory fish populations in space and time. © EDP Sciences, IFREMER, IRD 2015.


Judkins H.,University of South Florida | Arbuckle S.,Texas A&M University | Vecchione M.,NMFS National Systematics Laboratory | Garrison L.,Southeast Fisheries Science Center | Martinez A.,Southeast Fisheries Science Center
Journal of Natural History | Year: 2015

Cephalopods of the northern Gulf of Mexico are widely distributed and provide an important food source for a variety of marine animals. Sperm whales are year-round residents in the northern Gulf of Mexico. Prey availability has been proposed as an explanation for this non-migratory whale population. To examine this explanation, a short pilot cruise was conducted during the summer of 2009 to test equipment and to obtain preliminary observations. Then the 3-month Sperm Whale Acoustic Prey Study (SWAPS) was conducted during the winter/spring of 2010 to sample the mid-water pelagic community for possible prey of sperm whales. It also compared sperm whale distribution and prey composition across habitats of the northern Gulf of Mexico. This paper focuses on the cephalopod diversity within the mid-water pelagic community and assesses potential prey of the endangered sperm whales. © 2013, Copyright © 2013 Taylor & Francis.


Long W.C.,National Oceanic and Atmospheric Administration | Van Sant S.B.,National Oceanic and Atmospheric Administration | Van Sant S.B.,Southeast Fisheries Science Center | Haaga J.A.,National Oceanic and Atmospheric Administration
Journal of Experimental Marine Biology and Ecology | Year: 2015

Since the 1970s, dominance of the shallow water Pribilof Islands king crab populations has shifted from blue king crab (. Paralithodes platypus) to red king crab (. Paralithodes camtschaticus), potentially influenced by interactions at the juvenile stage. In laboratory experiments, we determined whether habitat and temperature could mediate competitive and predatory interactions between juveniles of both species. We examined how density and predator presence affect habitat choice by red and blue king crabs. Further experiments determined how temperature and habitat affect predation by year-1 red king crab on year-0 blue king crab. Finally, long-term interaction experiments examined how habitat and density affected growth, survival, and intra-guild interactions between red and blue king crab. Red king crabs had a greater affinity for complex habitat than blue king crabs and the presence of predators increased preference for complex habitat for both species. Predation on year-0 blue king crabs by year-1 red king crabs was lower in complex habitats and at colder temperatures. When reared alone, red king crab survival was higher at low densities and in complex habitats. When reared with blue king crab, survival of red king crab was higher in complex habitats and in the presence of blue king crab. Blue king crab survival was substantially lower in the presence of red king crabs regardless of habitat. In both rearing experiments, differences in changes in crab size appeared to be driven by mortality rates and size-selective predation. This demonstrates that interactions between juvenile red and blue king crabs are primarily driven by intra-guild predation and not competition for resources. These results, suggest that juvenile red king crabs have an advantage over blue king crabs which could lower productivity of the Pribilof Islands blue king crab stock since the former became dominant in that system. © 2014.


Donahue M.J.,Hawaii Institute of Marine Biology | Karnauskas M.,Southeast Fisheries Science Center | Toews C.,University of Puget Sound | Paris C.B.,University of Miami
PLoS ONE | Year: 2015

Many species of reef fishes form large spawning aggregations that are highly predictable in space and time. Prior research has suggested that aggregating fish derive fitness benefits not just from mating at high density but, also, from oceanographic features of the spatial locations where aggregations occur. Using a probabilistic biophysical model of larval dispersal coupled to a fine resolution hydrodynamic model of the Florida Straits, we develop a stochastic landscape of larval fitness. Tracking virtual larvae from release to settlement and incorporating changes in larval behavior through ontogeny, we found that larval success was sensitive to the timing of spawning. Indeed, propagules released during the observed spawning period had higher larval success rates than those released outside the observed spawning period. In contrast, larval success rates were relatively insensitive to the spatial position of the release site. In addition, minimum (rather than mean) larval survival was maximized during the observed spawning period, indicating a reproductive strategy that minimizes the probability of recruitment failure. Given this landscape of larval fitness, we take an inverse optimization approach to define a biological objective function that reflects a tradeoff between the mean and variance of larval success in a temporally variable environment. Using this objective function, we suggest that the length of the spawning period can provide insight into the tradeoff between reproductive risk and reward. © 2015, Public Library of Science. All rights reserved. This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.


Sweeney K.L.,Duke University | Shertzer K.W.,Southeast Fisheries Science Center | Fritz L.W.,National Oceanic and Atmospheric Administration | Read A.J.,Duke University
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2015

Weutilized aerial images and employed photogrammetric methodologies to collect standardized lengths of Steller sea lions (Eumetopias jubatus) terrestrially hauled out. We conducted comparisons among all site types and separately for rookery and haulout site-types between the two distinct population segments (DPSs; eastern and western) and two broad regions within the western DPS experiencing contrasting population abundance trends. An observed adult female index was created from measurements of reproductive females — in the presence of a pup or juvenile — and was applied as a model constraint for “adult females”. We fitted a finite mixture distribution model to the length-frequency data to estimate the proportion population for three delineated age–sex classes (juveniles, adult females, and adult males) and mean length for juveniles and adult males. Estimated proportions reflected what we expected; however, the broad region within the western DPS exhibiting substantial population declines had greater proportion of all age–sex classes on rookery sites than increasing broad region. Adult sea lions were significantly shorter in the eastern DPS than the western area, providing further evidence of morphological differences between the DPSs. We also introduce a less resource-demanding method for estimating population demographics, and potentially vital rates, for pinnipeds across a vast geographic range. © 2015, National Research Council of Canada. All rights reserved.


Gruss A.,IRD Montpellier | Gruss A.,University of Miami | Gruss A.,Southeast Fisheries Science Center | Robinson J.,Seychelles Fishing Authority | And 4 more authors.
ICES Journal of Marine Science | Year: 2014

There is a global trend in the depletion of transient reef fish spawning aggregations ("FSAs"), making them a primary target for management with marine protected areas (MPAs). Here, we review the observed and likely effectiveness of FSAMPAs, discuss how future studies could fill knowledge gaps, and provide recommendations for MPA design based on species' life history and behaviour, enforcement potential, and management goals. Modelling studies indicate that FSA MPAs can increase spawning-stock biomass and normalize sex ratio in protogynous fish populations, unless fishing mortality remains high outside protected FSA sites and spawning times. In the field, observations of no change or continued decline in spawning biomass are more common than population recovery. When empirical studies suggest that FSA MPAs may not benefit fish productivity or recovery, extenuating factors such as insufficient time since MPA creation, poor or lack of enforcement, inadequate design, and poorly defined management objectives are generally blamed rather than failure of the MPA concept. Results from both the empirical and modelling literature indicate that FSA MPAs may not improve exploitable biomass and fisheries yields; however, investigations are currently too limited to draw conclusions on this point. To implement effective FSA MPAs, additional modelling work, long-term monitoring programmes at FSA sites, and collections of fisheries-dependent data are required, with greater attention paid to the design and enforcement of area closures. We recommend a harmonized, adaptive approach that combines FSA MPA design with additional management measures to achieve explicitly stated objectives. Conservation objectives and, therefore, an overall reduction in mortality rates should be targeted first. Fisheries objectives build on conservation objectives, in that they require an overall reduction in mortality rates while maintaining sufficient access to exploitable biomass. Communication among researchers, regulatory agencies, park authorities, and fishers will be paramount for effective action, along with significant funds for implementation and enforcement. © International Council for the Exploration of the Sea 2014. All rights reserved.


Lombardi-Carlson L.A.,University of Florida | Lombardi-Carlson L.A.,Southeast Fisheries Science Center | Andrews A.H.,National Oceanic and Atmospheric Administration
Environmental Biology of Fishes | Year: 2015

There is a growing concern over the lack of life history information for many deepwater fisheries species, including golden tilefish, Lopholatilus chamaeleonticeps. Fundamental life history characteristics, like age and growth, are required for effective, age-structured stock assessments and management decisions. A previous effort to validate golden tilefish age estimates using bomb radiocarbon dating was inconclusive, which led to an application of lead-radium dating in the current study. Lead-radium dating uses the radioactive disequilibrium of lead-210 (210Pb) and radium-226 (226Ra) in otoliths as an independent estimate of age. Ages were also estimated using traditional age estimates by counting growth zones in thin otolith sections and lead-radium dating was used to test these estimates. Radiometric ages (corrected for time since capture) were similar to age estimates from growth zone counts for two of the female age groups and the two oldest age groups of unknown sex, which confirmed an annual growth zone deposition. However, radiometric ages did not agree with age estimates from growth zone counts for males. The difference may be attributed to geographical variations in radium levels, growth rates and growth zone formation by gender or gender transition. Male sagittal otoliths revealed inconsistent growth zone patterns in thin sections, which may have contributed to underageing. Golden tilefish longevity was confirmed to 26 years. © 2015, Springer Science+Business Media Dordrecht (outside the USA).


News Article | February 28, 2017
Site: phys.org

Scientists estimate that over-fishing of sharks along the southeast U.S. coast—which began in earnest following the release of Jaws in 1975 and continued through the 1980s—had reduced populations by 60-99% compared to un-fished levels. In response, NOAA's National Marine Fishery Service in 1993 enacted a management plan for shark fisheries that limited both commercial and recreational landings. Now, says lead scientist Cassidy Peterson, a graduate student at William & Mary's Virginia Institute of Marine Science, "We've shown that after over two decades of management measures, coastal shark populations are finally starting to recover and reclaim their position as top predators, or regulators of their ecosystem. Our research suggests we can begin to shift away from the era of 'doom and gloom' regarding shark status in the United States." Joining Peterson in the study, published in the latest issue of Fish and Fisheries, were VIMS professor Rob Latour, Carolyn Belcher of the Georgia Department of Natural Resources, Dana Bethea and William Driggers III of NOAA's Southeast Fisheries Science Center, and Bryan Frazier of the South Carolina Department of Natural Resources. The researchers say their study—based on modeling of combined data from six different scientific surveys conducted along the US East Coast and in the Gulf of Mexico between 1975 and 2014—provides a more accurate and optimistic outlook than previous studies based on commercial fishery landings or surveys in a single location. "Data from shark long-lining operations or shark bycatch can be suspect," says Peterson, "because what looks like a change in abundance might instead be due to changes in fishing gear, target species, market forces, or other factors." Research surveys are scientifically designed to remove these biases. Survey crews purposefully sample a random grid rather than visiting known shark hot spots, and strive to use the exact same gear and methods year after year to ensure consistency in their results. But even with these safeguards, data from a single survey often aren't enough to capture population trends for an entire shark species, whose members may occupy diverse habitats and migrate to different and far-flung areas depending on age and sex. "Because many shark species undergo vast migrations and have complex life cycles," says Peterson, "it's not uncommon for results from different surveys to conflict. Producing an estimate of total abundance requires combining data from different surveys—sometimes from several states or even countries—and applying intricate stock-assessment models." For the current study, the scientists combined data from six different shark surveys: the VIMS Longline Survey, the SouthEast Area Monitoring and Assessment Program's South Atlantic Coastal Trawl Survey, the South Carolina Coastal Longline Survey, the Georgia Red Drum Longline Survey, the Southeast Fisheries Science Center's Longline Survey, and the Gulf of Mexico Shark Pupping and Nursery Area Gillnet Survey. "Our study represents the most comprehensive analysis of patterns in abundance ever conducted for shark species common to our area and the Southeast coast," says Latour, who directs the longline survey at VIMS. Established in 1973, it is the world's longest running fishery independent monitoring program for sharks, skates, and rays. By pooling and modeling data from all six surveys, the researchers were able to estimate population trends for seven of the region's most common coastal species: the large-bodied sandbar, blacktip, spinner, and tiger sharks, and the smaller Atlantic sharpnose, blacknose, and bonnethead sharks. The results of the analysis were clear, says Peterson. "All the large-bodied sharks showed similar population trends, with decreasing abundance from the mid-1970s to the early 1990s, then a multi-year period of low abundance, and recent indications of recovery from past exploitation." All but one population of small coastal sharks also increased in abundance. The exception was blacknose sharks in the Gulf of Mexico, which decreased from the onset of records in 1989 until the study's end in 2014. This species is known to be susceptible to by-catch within the trawl fishery for Gulf shrimp. The blacknose population along the Atlantic coast of the southeast U.S. actually increased during the same period. The overall population trends make biological sense, says Latour. "The large-bodied species saw the greatest initial declines, both because they were highly sought by anglers, and because they mature late and produce relatively few pups. Their slow growth rate also helps explain the pause in their recovery following the onset of fishing regulations in the early 1990s." The smaller shark species, whose higher growth rates make them less susceptible to fishing pressure, saw lesser declines and more rapid recoveries. The team also found a correlation between shark numbers and both fishing pressure and large-scale climatic patterns. Explore further: Researchers recalibrate shark population density using data they gathered during eight years of study on Palmyra atoll More information: Cassidy D Peterson et al, Preliminary recovery of coastal sharks in the south-east United States, Fish and Fisheries (2017). DOI: 10.1111/faf.12210

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