Browsing by Subject "Fishery"

Now showing 1 - 4 of 4
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    An Evaluation of the Shrimp Industry in North Carolina: Could policy changes such as an altered harvest schedule increase the profitability of the shrimp fishery?
    (2007-08-31T19:12:34Z) Leister, Charles
    This study seeks to evaluate the ability of the North Carolina (NC) shrimp industry to cope with the impacts of imported shrimp on prices. First, this study provides a review of the literature and relevant background information. This essay then analyzes shrimp growth models and data from the National Oceanic and Atmospheric Administration (NOAA). This analysis evaluates the management decisions regarding the timing of the shrimp harvest by comparing the rate of change of prices to the rate of change of shrimp growth for four growth models. The first three models originated from the literature with the first model simulating the growth of male shrimp, the second model simulating the growth of female shrimp, and the third model simulating the growth of both sexes combined. While each of these models simulates the growth of individual shrimp, so the fourth model simulates shrimp population levels in addition to simulating shrimp growth resulting in biomass. Overall, the analysis yielded mixed results and proved highly dependent on the assumptions of the models. The results associated with the first and second models suggested the initial shrimp harvest occur in July rather than May, the analysis associated with the third model suggested managers delay the initial harvest until December or as late as possible to allow shrimpers to harvest all remaining shrimp, and the analysis associated with the fourth model suggested no change in the timing of the shrimp harvest. The mixed nature of these results suggests the need for more information regarding shrimp life history and growth. Following this conclusion, this study provides six general recommendations for the revision of the Fishery Management Plan (FMP) in 2011: 1) Explore the optimal harvest timing, 2) Increase marketing efforts, 3) Address issues of development such as water quality and habitat destruction, 4) Allow fishers to keep and/or sell bycatch within reasonable limits, 5) Increase environmentally responsible aquaculture, and 6) Increase funding for research. By addressing these issues surrounding the shrimp fishery in NC, managers can help to ensure the continued sustainability and profitability of one of North Carolina’s most valuable fisheries.
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    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.
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    Bycatch and Biomass: Mitigating dolphin bycatch while maintaining fish catch in the Virginia Beach pound net fishery
    (2008-04-18T22:24:11Z) Herman, Elia
    Pound nets are traditional, passive fishing traps that have been used since the 1870s to catch estuarine fish species in the Chesapeake Bay. Most unwanted species captured in the actual pound net can be released alive; however, sea turtles and marine mammals may die if they become entangled in the leader of the net. In 2004, NOAA Fisheries required changes in the construction of pound net leaders in part of the Chesapeake Bay to reduce entanglement rates of sea turtles. To date no actions have been taken to address the bycatch of bottlenose dolphins in pound net leaders. In the summer of 2007, I conducted a pilot study to sample catches of butterfish (Peprilus alepidotus and Peprilus triacanthus) and Spanish mackerel (Scomberomorus maculatus) in a Virginia Beach pound net fishery considering modifications to their leaders to reduce dolphin bycatch. Using these observations, I worked with the Virginia Aquarium to design an experiment to test the new leaders during the 2008 fishing season. The primary goal of this experiment is to determine whether the experimental leader will affect the catch of target fish species. From an analysis of dolphin strandings in Virginia from 1997-2004, I found that pound nets accounted for the greatest percentage (50%) of all documented Human Interaction (HI) strandings. I also used geospatial analyses to examine the distribution of bottlenose dolphin strandings that may be associated with bycatch in pound nets. HI stranded dolphins were found significantly closer to the Virginia Beach pound nets than dolphins that stranded for another reason (No HI) or for an unknown cause (CBD). Together these analyses help to improve our understanding of interactions between bottlenose dolphins and the Virginia Beach pound net fishery, as well as the importance of community-based management efforts.
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    Economic Valuation of Mangrove-Fishery Linkages in Guyana and Suriname
    (2019-04-24) Bollini, Celeste; Millar, Emily
    Mangroves are among the most productive ecosystems in the word. By providing valuable ecosystem services, mangroves enhance human well-being and contribute to biodiversity conservation in the tropical and subtropical regions where they are found. Mangroves provide nursery, feeding, breeding grounds, and shelter areas for many marine species, which in turn enhances the productivity of traditional and commercial fisheries. The objective of the present study is to evaluate how mangrove ecosystems affect fisheries in Guyana and Suriname, as part of a collaborative project between the Nicholas Institute for Environmental Policy Solutions and Conservation International. The evaluation involved conducting a meta-analysis of information drawn from 21 mangrove-fishery linkage studies from around the world to estimate a general model relating fish catch to mangrove area. A benefit transfer method was then used to apply the results from the meta-analysis to recent and projected future changes in mangrove areas in Guyana and Suriname, and thereby predict the impacts on fish catch in the two countries. The first section of this report provides an overview of mangrove ecosystems, definitions of the four types of ecosystem services identified by the Millennium Ecosystem Assessment, and an outline of the ecosystem services provided exclusively by mangroves. This section also highlights some of the main global drivers of mangrove loss. Lastly, it provides the main objectives of this project, an overview of Guyana and Suriname, and estimates of the areas and trends in mangroves in both countries. Mangrove area change was calculated using the average of estimates from two sources for each country. The estimated changes in mangrove area during 2000-2017 were -1.96% per year in Guyana and -0.76% per year in Suriname. The second section of this report describes the methods used to determine how these trends have affected fisheries in Guyana and Suriname. After providing an overview of the meta-analysis and benefit transfer methods, this section explains the variables selected for the meta-analysis. Variables were selected to capture essential characteristics of the study sites and the studies themselves. Finally, the equation estimated by the meta-analysis is defined. This equation relates the impacts of mangrove area reported by the studies to the selected variables. Observations were included in the dataset for estimating this equation only if a study included sufficient information for calculating the reported impact as an elasticity, which can be explained as follows: denoting the elasticity by Ɛ, a 1% increase in mangrove area increases fish catch by Ɛ%. The third section of this report applies the results from the meta-analysis to calculate the benefit transfer estimates for each country. There are two final models: a shellfish model and a finfish model. The shellfish model was used to generate the estimate for Guyana, while the finfish model was used to generate the estimate for Suriname. For Guyana, the predicted elasticity (Ɛ) is 0.924, which implies a 1.81% loss in shellfish catch per year resulting from the recent loss of mangroves in that country. For Suriname, the predicted elasticity (Ɛ) is 1.77, which implies a 1.34% loss in finfish catch per year resulting from that country’s recent loss of mangroves. These estimated losses in fish catch were calculated by multiplying each country’s elasticity by the observed changes in mangrove area noted previously. The fourth section of this study provides a discussion of the analysis and estimates the benefits of mangrove restoration in each country. If the estimated loss in mangrove area had not occurred in Guyana, the Guyanese fishery would have gained $586,440 in revenue net of costs. Similarly, if the estimated loss in mangrove area had not occurred in Suriname, the fishery in that country would have gained $180,900 in revenue net of costs. This section also provides a comparison to previous mangrove-fishery linkage studies. This is followed by a discussion of limitations of the present study, including the wide variation in mangrove area and mangrove area change estimates found in different sources. Lastly, recommendations for future data collection are provided. The final section of this study provides an insight into mangrove-fishery linkages within the countries of Guyana and Suriname for specific fisheries as well as the associated monetary gains resulting from conserving mangrove area. These estimates are insufficient for determining the total value of conserving mangrove area, but a more complete estimate of total value could be determined by applying valuation methods, similar to those used in this study, to additional ecosystem services.