A trophic model to explore fishing effects for Eritrea's Red Sea coral reef fisheries

I.W. Tsehaye, L.A.J. Nagelkerke

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Abstract

We assessed the potential for fisheries in the coral reefs of Eritrea from an ecosystem perspective using an Ecopath with Ecosim model. The model combined observed and literature data on the ecosystem and its inhabitants into a single framework, with the aim to gain a better insight into the structure and functioning of the ecosystem and assess potential impacts of fishing. Model outputs indicated that primary productivity in the system is mostly recycled through a detritus based food web, implying a bottom-up energy flow control. However, ecotrophic efficiencies were higher at higher trophic levels, suggesting that top-down mechanisms are also ecologically important. Despite an estimated high degree of primary productivity, the fishery yields from the coral reef ecosystem were relatively low, apparently because of lower ecotrophic efficiencies at the lower trophic levels. A retrospective simulation of trends in these fisheries using Ecosim showed that, given existing levels of fishing, as suggested by official statistics (0.114 tonnes km-2 year-1), levels of decline in abundance of reef-associated demersals inferred from CPUE analysis (ca. 25%) were unlikely. However, our model could reproduce past declines in yield when, based on anecdotal evidence on unreported catches, we assumed that existing fishing levels were five-fold official estimates. Simulation results showed that an optimal fishing strategy requires a slight reduction in annual catch of reef-associated fishes (to 0.32 tonnes km-2 year-1) and an increase in harvest of near-reef pelagics and large pelagics (to 0.19 and 0.39 tonnes km-2 year-1, respectively) from the putative levels.
Original languageEnglish
Publication statusPublished - 2015
EventCoral Reefs of Arabia Conference, Abu Dhabi, UAE -
Duration: 15 Feb 201517 Feb 2015

Conference

ConferenceCoral Reefs of Arabia Conference, Abu Dhabi, UAE
Period15/02/1517/02/15

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Tsehaye, I. W., & Nagelkerke, L. A. J. (2015). A trophic model to explore fishing effects for Eritrea's Red Sea coral reef fisheries. Abstract from Coral Reefs of Arabia Conference, Abu Dhabi, UAE, .