Long-distance movements of Antarctic toothfish (Dissostichus mawsoni) as inferred from tag-recapture data.

Examining the causes and consequences of animal movement is fundamental to understanding the ecology of any species. This analysis focuses on Antarctic toothfish movements in the Southern Ocean as inferred from tagging data collected from 2001 to 2019 with a focus on the characteristics of long-distance movements, defined as an individual recaptured greater than 200 km from their release location. The results of this analysis indicate that while adult Antarctic toothfish are generally quite sedentary a small proportion (~7%) move long distances, consistent with findings from previous studies examining movements of toothfish. There appears to be no relationship between time at liberty and long-distance movements, no strong influence of sex and results indicate a distinct bias in the direction of long-distance travel from release to recapture towards a counter-clockwise direction. Frequency and scale of long-distance movements are likely influenced by localized physical oceanographic processes and life-history traits. Knowledge of these movements patterns remains highly important for stock assessments and the design of spatial and temporal fisheries management regimes.

Thirty years of marine debris in the Southern Ocean: Annual surveys of two island shores in the Scotia Sea.

We report on three decades of repeat surveys of beached marine debris at two locations in the Scotia Sea, in the Southwest Atlantic sector of the Southern Ocean. Between October 1989 and March 2019 10,112 items of beached debris were recovered from Main Bay, Bird Island, South Georgia in the northern Scotia Sea. The total mass of items (data from 1996 onwards) was 101 kg. Plastic was the most commonly recovered item (97.5% by number; 89% by mass) with the remainder made up of fabric, glass, metal, paper and rubber. Mean mass per item was 0.01 kg and the rate of accumulation was 100 items km-1 month-1. Analyses showed an increase in the number of debris items recovered (5.7 per year) but a decline in mean mass per item, suggesting a trend towards more, smaller items of debris at Bird Island. At Signy Island, South Orkney Islands, located in the southern Scotia Sea and within the Antarctic Treaty area, debris items were collected from three beaches, during the austral summer only, between 1991 and 2019. In total 1304 items with a mass of 268 kg were recovered. Plastic items contributed 84% by number and 80% by mass, with the remainder made up of metal (6% by number; 14% by mass), rubber (4% by number; 3% by mass), fabric, glass and paper (<1% by number; 3% by mass). Mean mass per item was 0.2 kg and rate of accumulation was 3 items km-1 month-1. Accumulation rates were an order of magnitude higher on the western (windward) side of the island (13-17 items km-1 month-1) than the eastern side (1.5 items km-1 month-1). Analyses showed a slight decline in number and slight increase in mean mass of debris items over time at Signy Island. This study highlights the prevalence of anthropogenic marine debris (particularly plastic) in the Southern Ocean. It shows the importance of long-term monitoring efforts in attempting to catalogue marine debris and identify trends, and serves warning of the urgent need for a wider understanding of the extent of marine debris across the whole of the Southern Ocean.