Abstract
Marine Protected Areas (MPAs) are increasingly implemented to facilitate the conservation of marine biodiversity and key habitats. However, these areas are often less effective to conserve mobile marine species like elasmobranchs (i.e., sharks and rays). Industrial fishing near MPA borders possibly impacts vulnerable species utilizing these protected areas. Hence, we aimed to study spatiotemporal patterns of industrial fisheries near MPAs, in relation to the bycatch of elasmobranchs. Specifically, we analyzed the spatiotemporal fishing effort within the West African region, mapped fishing effort in the direct vicinity of the Parc National du Banc d’Arguin (PNBA, Mauritania) and the Bijagós Archipelago (BA, Guinea Bissau), and compared the seasonal overlap between elasmobranch bycatch and fishing effort near these MPAs. We combined Automatic Identification System (AIS) data and local fisheries observer data, and determined fishing effort for each gear type and compared this with bycatch of elasmobranchs. We found that industrial fishing effort was dominated by trawling, drifting longlines, and fixed gear types. Although no industrial fishing was observed within both MPAs, 72 and 78% of the buffer zones surrounding the MPAs were fished for the Banc d’Arguin and Bijagós, respectively. Within the Banc d’Arguin buffer zone, trawling and drifting longlines dominated, with longlines mainly being deployed in fall. In the Bijagós buffer zone, trawling and fixed gears were most prevalent. Fisheries observer data for Mauritania showed that elasmobranch catches increased during the most recent sampling years (2016–2018). Elasmobranch catches within the waters of Guinea Bissau peaked in 2016 and decreased in the following two years. Seasonal patterns in elasmobranch bycatch within the waters of both countries are likely caused by increased catches of migratory species. Catches of rays peaked in May and June for Mauritania, and in October for Guinea Bissau. Shark catches were highest in February and July in Mauritanian waters, and in May and October in the waters of Guinea Bissau. Our study indicates that industrial fisheries near the border of ecologically important MPAs may have potentially major implications for ecosystem functioning by the removal of (migratory) predatory species.
Highlights
To halt the degradation of marine ecosystems and to counter overexploitation of marine resources, an increasing number of Marine Protected Areas (MPAs) have been implemented over the last two decades (Watson et al, 2014; McDermott et al, 2018)
Fishing effort concentrated in coastal waters (70% in EEZs compared to 30% in high seas), with the EEZs of Mauritania (10%), Western Sahara (8%), Morocco (8%), and Guinea Bissau (7%) together containing over 36% of the total fishing effort (Supplementary Table S1)
Automatic Identification System (AIS) records demonstrated that fishing activity is concentrated near the borders of MPA: Parc National du Banc d’Arguin (PNBA) (Mauritania) and the Bijagós Biosphere Reserve (BA, Guinea Bissau)
Summary
To halt the degradation of marine ecosystems and to counter overexploitation of marine resources, an increasing number of Marine Protected Areas (MPAs) have been implemented over the last two decades (Watson et al, 2014; McDermott et al, 2018) The majority of these implemented MPAs cover coastal areas, like vegetated wetlands and coastal reefs, which can be important for marine megafauna species (Fox et al, 2012; Sievers et al, 2019). Megafauna species generally have large home ranges and are often migratory (Lewison et al, 2014) They only spend a limited, but essential proportion of their life cycle in such areas. Due to their migratory nature, these species form important functional links (e.g., transferring nutrients) between coastal areas and other systems, such as the pelagic zone (Williams et al, 2018; Sievers et al, 2019)
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