Potential effects of climate variability and change on bycatch using Antarctic skates as a case study

Climate variability and change are likely already affecting Antarctic marine ecosystems, fish and fisheries, but monitoring these effects and predicting future trajectories of change is challenging. In this paper for the CCAMLR Climate Change Workshop, we present a summary of the likely effects of climate variability and change on Antarctic skates as a case study for bycatch species. Anticipating the potential effects of climate change is a step towards designing management measures to avoid, reduce or manage the risks that climate change and fishing will contravene CCAMLR principles of conservation. While climate change research on Antarctic skates is limited, studies of skates elsewhere suggest that the most at-risk life history stage for skates may be egg cases. Skates are oviparous, with female skates laying large eggs where embryos develop over prolonged periods lasting from months to years. Skate egg case nurseries are often reported from narrow depth ranges on the continental shelf and slope and in waters with constant bottom temperatures. To date, there are only two documented egg case nurseries in the Southern Ocean: one occurs along the continental shelf and slope west off Anvers Island in the western Antarctic Peninsula between a narrow depth band of 394–443 m and the other is in the Ross Sea at one location on the shelf break at ~460 m off Cape Adare. We recommend that efforts should continue to identify, characterise, and protect areas of essential habitat for bycatch species, including fish nest areas and skate egg case nurseries. We also recommend studies be carried out to understand the physiological and ecological (especially trophic) effects of climate change on Southern Ocean fish species caught as bycatch.