Spatial management measures benefit the critically endangered flapper skate, Dipturus intermedius

Abstract

While elasmobranchs are often a designated feature in Marine Protected Areas, there are few studies that have evaluated the effectiveness of spatial fishery restrictions on their recovery. Here we examine the effectiveness of fishery restrictions on the critically endangered flapper skate, Dipturus intermedius, based on changes in their abundance, demography and survival rate. Trends in local abundance at two sites within the Loch Sunart to the Sound of Jura Marine Protected Area (LStSJ MPA), were contrasted with that in surrounding waters off the west of Scotland where fishing remains unrestricted. Survival rate was estimated using a multi‐state model of capture mark recapture data, and spill‐over from the LStSJ MPA was considered from tag‐recapture rates between the two LStSJ MPA study areas and a further site south of the LStSJ MPA. In contrast to the wider trend across adjacent waters, skate abundance increased, especially for young juveniles, following the introduction of fishing restrictions in the LStSJ MPA. This increase could be explained by a reduction in juvenile and adult mortality as population growth rates following fishing restrictions were markedly higher than estimated in a pre‐restriction study of one site. Limited exchange of skate between the two study areas within the LStSJ MPA and a southern site beyond the LStSJ MPA indicated a low rate of spill‐over. This study demonstrates that spatial fishery restrictions have the potential to benefit populations of elasmobranchs which have a high site‐fidelity, but their wider conservation benefit may be partly confounded by a high level of residency.