Interannual variability in the skate assemblage on the South Patagonian shelf and slope

Abstract

Observer data from the commercial fishery on the Patagonian shelf and slope around the Falkland Islands (home to an assemblage of >16 skate species (Rajiformes), for which commercial catches have been recorded since 1987), as well as survey data from an area closed to skate target fishing after exploitation, were summarized by species to examine changes in the population status of individual skate species. Total skate catch per unit effort increased significantly in the target fishery since 1994, and four species have made up >85% of all skate catch. Bathyraja brachyurops and Zearaja chilensis increased significantly in catch proportions and abundance from 1994 to 2013. Bathyraja albomaculata and Bathyraja griseocauda decreased significantly before rebounding with trends of increasing abundance. Concurrently, B. brachyurops and Z. chilensis showed decreasing trends in size at 50% maturity in areas where skates continue to be targeted commercially. The increasing abundances and concomitant reductions in size at maturity of B. brachyurops and Z. chilensis suggest either plasticity in life-history traits or a density-dependent growth response to fishing pressure. Bathyraja griseocauda decreased in size at 50% maturity in the area that was closed to skate target fishing, where it was initially larger, but only decreased to the same average size as in the commercially targeted areas. Bathyraja albomaculata and Z. chilensis are IUCN-listed as vulnerable and B. griseocauda is listed as endangered, but their abundance trends since 1994 indicate that these populations are not declining in Falkland waters.

Parasites as tags for stock identification of a highly exploited vulnerable skate Dipturus brevicaudatus (Chondrichthyes: Rajidae) in the south‐western Atlantic Ocean, a complementary tool for its conservation

“…In the northern Argentine Sea, the decline in size‐at‐maturity has been attributed to overfishing (Paesch & Oddone, 2008). A similar response to fishing pressure has also been observed in southern Patagonian waters (Winter et al, 2015). Consequently, this species was classified as ‘Vulnerable’ by the International Union for Conservation of Nature (IUCN) (Pollom et al, 2021).…”

“…A similar response to fishing pressure has also been observed in southern Patagonian waters (Winter et al, 2015). Consequently, this species was classified as 'Vulnerable' by the International Union for Conservation of Nature (IUCN) (Pollom et al, 2021).…”

The biology, ecology and conservation of elasmobranchs: recent advances and new frontiers

“…The role of fishing exploitation on elasmobranch populations and the future for their conservation was also a key theme of the symposium. It was evident that to identify accurately the effects of fishing it was also necessary to know about interannual variability in the presence of elasmobranchs due to other factors, a point well illustrated by the paper by Winter et al () on the skate assemblage of the Patagonian shelf in the South Atlantic Ocean. Deep‐water elasmobranchs are known to have slow growth and low fecundity and are thought to be particularly vulnerable to fisheries.…”