Browsing by Author "Boustany, Andre"
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Item Open Access ANALYZING THE SPATIAL DISTRIBUTION OF FISH SPECIES ALONG THE MID AND SOUTH ATLANTIC BIGHTS AND PROJECTING FUTURE DISTRIBUTIONS UNDER A CLIMATE CHANGE SCENARIO(2017-04-27) Roberts, Sarah MAs anthropogenic climate change increases the temperatures of the world’s oceans, the survival rates, spatial distribution, and phenology of marine species are adversely impacted. This study evaluates the potential effects of anthropogenic climate change on seven commercially regulated fish species along the South Atlantic and Mid-Atlantic Bight. Coupling random forest models with the outputs from 27 climate models, this study projects the future distribution of species using bottom temperature, salinity, substrate type and AMO and NAO indices. Results indicate that species distribution shifts vary depending on the season, the species preferred temperature range, and the relative importance of habitat and salinity for the species.Item Open Access Applying Fishery Catch Data to Population Trends and Community Structures in Atlantic Pelagic Species(2017-05-06) May, EvaRecent studies have shown that fishing can influence marine trophic networks, as larger, higher trophic level species are preferentially targeted by fishers. In this study, we investigate US Pelagic Longline catch dynamics of twenty-nine Atlantic species from 1986 to 2008 using information provided by the fishermen’s logbook data program. Two different analyses were performed on the data for this study. Data were cleaned and monthly catch per unit effort (CPUE) for each species within each of five fishing effort regions – the Mid Atlantic Bight and Northeast Costal area, The Caribbean area, the Florida East Coast and South Atlantic Bight area, the Gulf of Mexico area, and the Northeast Distant area – were calculated to examine trends in catch rates. Annual CPUE graphs were made for all areas combined, correcting for changes in fishing dynamics to examine changes in relative abundance of species over time. A regression was run through these annual graphs of CPUE over the study period in order to estimate increases or decreases in relative population abundance for each species. The slopes from these annual abundances regressions were further regressed versus trophic level, average generation length, and resiliency to test for significant correlations between these ecological factors and trends in population size. Though trends matched our predictions (species with higher trophic level, lower resiliency, and longer generation length showed greater declines in abundance), no significant p-values were found. It seems likely that ecosystem structural shifts similar to those seen in other recent studies are occurring, but the lack of significance makes it difficult to draw strong conclusions. The lack of significance between ecological factors and population trends observed in this study may be due to trophic shifts in fishing are not occurring or may be due to issues with the data used for regressions. Future studies using different methods of obtaining demographic factors and incorporating additional years of catch data could bring more clarity to this work.Item Open Access Economic and Ecological Analysis of the Cape Hatteras Area Closure in the Atlantic Bluefin Tuna Fishery(2015-04-21) Ware, MeganAtlantic bluefin tuna are overfished and, consequently, NOAA is implementing a Cape Hatteras area closure to reduce catch in the longline fishery. The objective of this Masters Project was to investigate the ecological and economic impact of this management measure. Data from the fishery was mapped in ArcGIS to calculate CPUE, model the redistribution of displaced fishing effort, and understand the ecological benefits to the fishery. Results showed that fishermen are expected to relocate effort south of the area closure. Corresponding ecological benefits do not fully account for dead discards and are not expected to rebuild stocks. CPUE is not consistently high within the closure but instead migrates seasonally along the coast. This suggests that dynamic fisheries management may have greater ecological benefits to Atlantic bluefin tuna.Item Open Access Feeding habits of the tiger shark, Galeocerdo cuvier, in the northwest Atlantic Ocean and Gulf of Mexico(2017-04-14) Aines, AlexandraSharks are apex predators that structure marine communities through predation. Despite a large number of studies in other areas, especially the Pacific, there are no quantitative data on the diet of tiger sharks, Galeocerdo cuvier, in the northwest Atlantic Ocean and Gulf of Mexico. Diet was assessed from 169 tiger sharks by life stage, area, and environmental factors. Fifteen prey groups were identified, with teleosts, molluscs, birds, cephalopods, and reptiles being the predominant prey categories. There was an ontogenetic shift in diet, prey size and diversity with an increase in shark size. Molluscs were most common in smaller sharks, while teleosts and reptiles became more important in the diet of larger sharks. Dietary overlap was significant by area (Gulf of Mexico vs Atlantic Ocean) and among all life stages except for young-of-the-year and adult tiger sharks. Overall, tiger sharks in the northwest Atlantic and Gulf of Mexico had diverse diets and exhibited ontogenetic shifts, similar to Pacific tiger sharks. Juvenile tiger sharks also demonstrated selective feeding by targeting gastropod foot over ingesting the entire animal. The results of this study can contribute to developing ecosystem models for tiger sharks in an area where their diet has been studied very little.Item Open Access Optimizing Conservation Benefits of Pelagic Marine Protected Areas: Assessing Alternative Timing of the Charleston Bump Time-Area Closure(2017-04-28) Cleaver, SaraThe three-month Charleston Bump time-area closure was implemented in 2001 with the primary goal of reducing bycatch of juvenile swordfish in the U.S. Atlantic pelagic longline fishery. Due to this closure and other management measures, the swordfish stock has since rebuilt, and the fishery is currently underutilized; swordfish landings are below the recommended quota. To meet consumer demand in the United States, swordfish are imported from foreign fleets, many of which are not held to the same bycatch reduction standards as U.S. fisheries. By analyzing the composition of pre and post-closure catch data, as well as predicting catch per unit effort during the closure, this project investigates potential temporal alternatives for the closure which would optimize conservation benefits; increasing domestic catch of swordfish while limiting interactions with protected and frequently discarded species of sharks, finfish, and sea turtles.Item Open Access Shark Week and Public Perceptions of Sharks(2019-04-12) O'Donnell, KatiePerceptions of predators, and the type of language used when describing them, can influence a person’s decision whether or not to support wildlife conservation. Many shark species are important apex predators that are found in oceans worldwide, giving sharks a unique role in our society. This study investigated social conversations about sharks by using sentiment analysis of the social media platform, Twitter. We wanted to see if popular annual programming, such as Discovery Channel’s Shark Week, influences the language used in public social conversations and how that affects attitudes toward sharks. Sentiment and statistical analyses show that Shark Week affects the sentiment of language used in Twitter conversations about sharks from 2012-2017. This study builds on the growing literature that increases understanding of public sentiment of sharks, which can contribute to more informative and effective policies to better protect sharks.Item Open Access Spatial and temporal variability of sea surface temperature and fisheries distribution with the North Atlantic Oscillation(2014-04-24) Griefen, Ana; Bonamusa, JessicaIncreasing evidence supports relationships between fisheries distribution and climate variability. The main driver of climate variability in the North Atlantic Ocean is the North Atlantic Oscillation (NAO). Fisheries distribution is influenced by sea surface temperature (SST), which displays a dynamic relationship with the NAO. To assess these relationships, we conducted a spatial and temporal analysis of SST, fisheries distribution, and the NAO from 1986 to 2008 in the Northwest Atlantic and Gulf of Mexico. We conducted a pixel-level linear regression analysis with the USGS Curve Fit tool in ArcMap to examine the spatial patterns of correlation coefficients and goodness of fit between monthly SST and monthly NAO index. We identified five regions in the Northwest Atlantic, and two regions in the Gulf of Mexico, where coefficients demonstrated relatively significant correlation between SST and the NAO. These regions were consistent with local ocean circulation patterns. To assess the relationship between the NAO and fisheries distribution in the identified correlation regions, we calculated linear regressions between tuna and swordfish catches and effort distribution with the NAO as the explanatory variable. Our results suggest that our linear model with the NAO as the single explanatory variable was too simplistic to explain fisheries catch and distribution variability. Further study using different models and explanatory variables may elucidate significant relationships between SST, fisheries distribution, and the NAO. Trends between fisheries and the NAO may provide insight into future effects of climate change on fish stocks with implications for fisheries management.Item Open Access Updated Age of Maturity of Pacific Bluefin Tuna(2017-05-08) Huff, SamanthaAlthough Pacific Bluefin Tuna (PBF) range throughout the Pacific Ocean, there are two main spawning grounds located in a geographically limited region, one in the area between the Philippines and the Ryukyu Islands (southern) and the other in the Sea of Japan (northern). As of now the age of maturity used in the stock assessment is based on histological observations from only the northern spawning ground. Using this maturity schedule might result in an underestimation of the age of maturity, since all the fish in the population might not be present on the spawning ground and the northern spawning ground has a younger distribution of fish than the southern spawning ground. In this paper, we compare the age distribution of PBF caught on the spawning grounds to the expected age distribution of fish in the overall population to determine the proportion of fish that are spawning in each age class and the probability of maturity at each age class. We found a large discrepancy between the spawning grounds with age of 50% maturity for the Taiwanese spawning grounds at approximately age 11 while in Sea of Japan there was a 50% probability of maturity between age 3 and 4. To explore the effects of estimated age of maturities, a simple age-structured model was created, and different scenarios were projected. An older age of maturity has serious repercussions for spawning stock biomass. With no reduction in fishing mortality, 3.10% of the population in the northern spawning ground reached maturity in comparison to 0.419% of the population in the southern spawning ground.Item Open Access Variability in Trans-Pacific Migration Rates of Pacific Bluefin Tuna (Thunnus orientalis)(2019-04-26) Markowski, WillWithin the past several decades, Pacific bluefin tuna (Thunnus orientalis; PBT) stocks have dropped to historically low levels, currently estimated at just 3.3% of unfished levels. All PBT are spawned in the Western Pacific Ocean (WPO) and an unknown proportion of juveniles (Ages 1 and 2) make trans-Pacific migrations across the Northern Pacific Ocean (NPO). This study was conducted to investigate potential environmental drivers of PBT trans-Pacific migration and support management of the stock through a better understanding of when and where they interact with fisheries. Two primary questions were explored: (1) what are the environmental correlates that drive the residency of Age-1 and Age-2 PBT in the WPO; and (2) what environmental correlates increase the residency duration in the Eastern Pacific Ocean (EPO)? We used long term (1952-2014) oceanographic and catch data, which allowed us to examine the influence of decadal scale environmental regime shifts. Generalized Additive Models (GAMs) were used to quantify the strength in relationships between modeled PBT catch-at-age (CAA) data, and focal explanatory variables. The effects of sea surface temperature (SST), sea surface height anomalies (SSHa), the Pacific Decadal Oscillation (PDO), the Arctic Oscillation (AO), upwelling, iron input from Asian dust, and prey availability on the proportion of PBT making eastward and westward trans-Pacific migrations were examined. Residency of Age-1 PBT in the WPO was positively correlated with anchovy and sardine landings in the WPO, as well as SSHa, while Age-2 PBT had significant relationships with sardine landings, SST, aeolian dust, and the PDO. In the EPO residency of both Age-4 and Age-5 PBT were significantly correlated with increased sardine and lower mackerel landings. These findings are aligned with previous hypotheses that prey abundance is a key influencing factor on PBT residency in the WPO.