The deep-sea red crab Chaceon notialis (Geryonidae) in the southwestern Atlantic Ocean: Spatial patterns and long-term effects of fishing

Abstract

The deep-sea crab Chaceon notialis is distributed along the continental shelf and slope of the SW Atlantic Ocean, mainly in Uruguayan waters, supporting a male-only fishery of high commercial value since 1993. A long-term study of catch per unit of effort (CPUE), population structure and individual weight was carried out before and after the onset of exploitation. Some 23,000 individuals were collected at 300–900m depth and between latitudes 35°00′ and 36°40′S during seven fishery-independent trap surveys. Additional data on weight and individuals with signs of molting were gathered from 1000 to 1600m south to 37°00′S after the start of the fishery. Individual weight decreased markedly over time, particularly after the start of the fishery, and decreased with depth for both sexes, with opposite patterns with latitude. CPUE peaked at 900m and 35°40′S and remained stable over time, suggesting that it does not reflect the condition of the stock. Ovigerous females were found between 300 and 500m and in the northernmost edge of the distribution range (35°00′S–35°40′S). The number of females decreased exponentially with depth and linearly with latitude. Molting males and females followed opposite latitudinal patterns, with highest percentages of molting individuals found between 600 and 900m depth. A spatial management framework is proposed, which includes closing areas to fishing where ovigerous females, juvenile crabs and largest males are concentrated.