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Compartive network analyses for Nigerian coastal waters using two ecopath models developed for the years 1985 and 2000

Adebola, Tunde, de Mutsert, Kim
Fisheries research 2019 v.213 pp. 33-41
Farfantepenaeus notialis, Penaeus monodon, coastal water, coasts, continental shelf, ecosystems, food webs, models, shrimp, shrimp fisheries, Nigeria, United States
In the late 1990s, depletion of Pink Shrimp (Penaeus notialis) in Nigerian coastal waters (NCW) resulted in increased exploitation of Brown Shrimp (Penaeus monodon), and in spatial redistribution of fishing effort for coastal shrimp fisheries in Nigeria. We investigate the hypothesis that ecosystem impacts of fishing increased as industrial trawler fleets encroached into shallower areas of the Nigerian coast in search of Brown Shrimp to augment their shrimp catch. To this purpose, we describe the ecosystem structure in NCW using a mass-balanced ecosystem modeling approach in Ecopath with Ecosim for two years –1985 and 2000. We then quantify impacts of increasing fishing intensity by comparing these two models using network analysis. We also compare the NCW EwE models with models developed for the Catalan Sea, Carribean Seas, and the USA continental shelf. Our analyses reveal that over the course of 15 years, the NCW ecosystem became less structurally complex, and less productive. The EwE Mixed Trophic Impact (MTI) index showed increasing negative impacts of coastal fishing activities in the 2000 model compared to the 1985 model. This is the first attempt to provide fisheries ecosystem models for Nigeria, and this research contributes to fisheries ecology by furthering our understanding of coastal food webs and ecological responses, especially in perturbed ecosystems such as in NCW.