Impact of artisanal benthic fisheries on marine ecosystems: A case study in the Gulf of California
The most basic level of artisanal fisheries is represented by hand-collecting, which is highly selective and widely recognized as having minimal impact on the environment. Nevertheless, there are some concerns that hand-collecting fisheries have the potential to negatively affect marine environments. We assessed the potential impacts of hookah diving for the pen shell Atrina maura, a hand-collecting fishery, in the Gulf of California, México. In situ observations revealed high sediment resuspension and Atrina shell remains widespread on the rhodolith bed where they are collected (‘fishery’ site), and on a nearby shallow sedimentary habitat where fishermen dump empty shells and tissue remains (‘polluted’ site). Structural complexity (i.e. size, shape and degree of branching) of rhodoliths at the fishery site were lower than previous reports in the area, while high mud and organic matter content was characteristic of the polluted site. Comparisons of faunal samples at the polluted site and control site showed that while faunal density and taxa abundance was greater at the polluted site, taxa evenness and Shannon's diversity indices were greater at the control site. Faunal abundance was highest for detritivorous gastropods (e.g. Cerithiidae, Caecidae) and bivalves tolerant to muddy substrata with potential low oxygen conditions (e.g. Thyasiridae), as well as deposit-feeding polychaetes (e.g. Flabelligeridae, Cirratulidae) at the polluted site. This study suggests impacts of artisanal hand-collecting fisheries on the benthos can be more severe than previously assumed and highlights the need to devise and implement adequate fishing education and management programs to protect benthic resources and the livelihood of local fishermen.