Spatial, temporal, and demographic variability in patagonian toothfish (Dissostichus eleginoides) spawning from twenty-five years of fishery data at South Georgia

Patagonian toothfish (Dissostichus eleginoides) are a commercially important species that support a longline fishery at the subantarctic island of South Georgia (CCAMLR Subarea 48.3). Understanding the life history of Patagonian toothfish is key to the successful management and sustainability of this fishery. Using catch data from the past 25-years, 1997 to 2021, we provide an updated assessment of the spatial, temporal, and demographic variability of Patagonian toothfish spawning at South Georgia. Our findings confirm that spawning occurs in the vicinity of the shelf-break of South Georgia, with significant spawning hotspots detected at Shag Rocks, midway along both the northern and southern shelf breaks, and at the eastern end of the island. The location of these hotspots were consistent over the 25-years examined. Based on data between 1997 and 2007, when fishing occurred routinely all around the island and at Shag Rocks, 40% of detected hotspot locations overlapped with regions where Benthic Closed Areas (BCAs) were established in 2008. With this, we can estimate that approximately 40% of spawning hotspots are located within, and already protected by, the existing network of BCAs. There was evidence that the timing of toothfish spawning exhibited bimodality at South Georgia with a peak in April being observed in the first two years of the time series. This peak fell outside the seasonally restricted fishing season for many subsequent years. These findings are discussed in the context of both historic, current, and possible future regulatory changes to this longline fishery.

Details