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Fish and fisheries dynamics at Banc d’Arguin, Mauritania: consequences for the intertidal food webs

PhD ceremony:Mr S.A. (Sidi) Lemrabott
When:February 28, 2023
Supervisors:prof. dr. H. (Han) Olff, prof. dr. T. (Theunis) Piersma
Co-supervisor:dr. A. Van Leeuwen
Where:Academy building RUG
Faculty:Science and Engineering
Fish and fisheries dynamics at Banc d’Arguin, Mauritania:
consequences for the intertidal food webs

The overfishing of marine resources is a global problem. This situation is even more alarming when it concerns the top-predator species and particularly the vulnerable species of elasmobranchs. These species play an important role in the ecological balance of marine ecosystems through their top-down controls of trophic levels. Traditionally, the fishing in the Banc d'Arguin ecosystem mainly targeted migratory species such as Mullet (Mugil cephalus) and Meagre (Argyrosmus regius), and only for subsistence. Since the mid-1980s, fishing shifted focus to elasmobranchs (sharks and rays) as a result of the temptations of the global market. The loss of these species will have had an impact on the structure of the entire food web as well as on the functioning of the ecosystem overall.

In his thesis, Sidi Lemrabott combined fishing data obtained from the long-term fisheries monitoring programme and ecological data from field experiments to understand the interplay between fishing activities and aspects of ecosystem functioning.

Lemrabott: ‘The abundance indices of the main species involved in the Banc d'Arguin fishery have been showing steep declines. Therefore, most fish resources in this ecosystem are overfished as a result of the fishing down of the food web. In contrast to the negative impact of fishing, we laid bare a positive ecological impact of shorebird-probing on the growth of seagrass and hence primary productivity in the Banc d’Arguin ecosystem. I propose new and sincere intentions towards management steps leading to sustainable fishing practices. This includes a complete break with any form of exploitation of elasmobranchs fish within the Banc d'Arguin ecosystem.’