Browsing by Author "May, Eva"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Applying Fishery Catch Data to Population Trends and Community Structures in Atlantic Pelagic Species
    (2017-05-06) May, Eva
    Recent 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.
  • Thumbnail Image
    ItemOpen Access
    Assessing Data Requirements for Calculating Sustainable Marine Mammal Bycatch Limits
    (2022-04-15) May, Eva
    The Fish and Fish Product Import Provisions of the Marine Mammal Protection Act extend several domestic marine mammal management tools to foreign fisheries wishing to export their products to the United States. One of these tools is the calculation of bycatch limits for marine mammal populations impacted by fishing operations. Several methods exist for these calculations, with the most ubiquitous methodology being the Potential Biological Removal model. This study explores all calculation methods and their data requirements, categorizing methods based on model structure and input data. Measures and concepts of population size are most crucial to creating bycatch limit models across existing methods. Exporting fishery managers in low-data environments should focus on collecting population abundance data while being mindful of other important factors such as data uncertainties, how models fit into larger regulatory schemes, and conservation objectives. Further, these models are most accurate and impactful when they are updated and grown as more data about marine mammal populations are collected. Data availability is the primary limiting factor in implementing bycatch limit methods, and this work has important implications for comparability determinations for foreign fisheries under the new Import Provisions.