Antarctic demersal finfish around the Elephant and the South Orkney islands: distribution, abundance and biological characteristics

Summary

A comprehensive 2018 bottom trawl survey around Elephant Island and the South Orkney Islands catalogued the region's demersal finfish populations, identifying 37 different species with a total catch of 19.1 tonnes. The survey revealed distinct regional patterns in fish communities: around Elephant Island, Antarctic silverfish (Notothenia rossii) dominated the catches, making up 85% of all fish captured, while around the South Orkney Islands, the humped rockcod (Gobionotothen gibberifrons) was the most abundant species.This research provided crucial updated stock assessments for waters that have been under a fishing moratorium since the 1989/90 season, nearly three decades of protection. The survey documented significant regional differences in both species composition and fish abundance between the two island groups.Among the key discoveries was the identification of a nursery area for Antarctic dragonfish (Champsocephalus gunnari), where young fish concentrate to grow and develop. The survey also continued important long-term monitoring efforts to track fish population recovery in areas that were historically overfished and depleted before the fishing ban was implemented.

This map shows the navigation route and sampling locations for the 2018 research cruise. Panel (a) displays 15 bottom trawl stations around Elephant Island (Subarea 48.1), while panel (b) shows 21 sampling sites around the South Orkney Islands (Subarea 48.2). The systematic sampling pattern enabled comprehensive assessment of demersal finfish populations in these Antarctic waters under fishing moratorium since 1989/90.

Key Findings

Researchers collected 37 different fish species during 36 bottom trawl sampling operations, with 15 hauls conducted around Elephant Island and 21 around the South Orkney Islands.

Antarctic silverfish (N. rossii) overwhelmingly dominated catches at Elephant Island, accounting for 16.2 tonnes or 85% of all fish caught, but was virtually absent from South Orkney Islands waters.

The two regions showed distinctly different fish communities, with humped rockcod (G. gibberifrons) being the most common species around the South Orkney Islands.

Scientists discovered an important nursery area for young Antarctic dragonfish (C. gunnari) measuring 5-13 cm in total length on the western shelf waters of Elephant Island.

Population estimates revealed substantial fish stocks: approximately 376,229 tonnes of Antarctic silverfish around Elephant Island and 11,145 tonnes of humped rockcod around the South Orkney Islands.

Most captured fish showed developing or fully developed reproductive organs, indicating the survey timing coincided with important spawning periods in these species' life cycles.

Abstract

A research survey for demersal finfish was completed using bottom trawl fishing gear, following a random stratified sampling design, between 50 and 500 m on shelf areas of Subarea 48.1 (Elephant Island) and Subarea 48.2 (South Orkney Island). An acoustic survey was simultaneously carried out to enhance knowledge of bathymetry and the distribution of fish and krill in the studied area. The cruise took place between the 6 and 27 January 2018. A total of 36 hauls were carried out, 15 around Elephant Island and 21 around the South Orkney Islands. A total of 37 fish species were caught with a total biomass of 19,112 kg. The main species encountered included Notothenia rossii and Champsocephalus gunnari, with nominal catches weighing 16,204 (85%) and 876 kg (5%), respectively. Other species of fish accounted noticeably for lower amounts (11%), such as Gobionotothen gibberifrons (330 kg), Chaenocephalus aceratus (322 kg), and Pseudochaenichthys georgianus (299 kg). Indicative estimates of standing stock biomass suggested that in this cruise, N. rossii was the most abundant demersal finfish species in the Elephant Island area, followed by C. gunnari. Differently, on the South Orkney Islands shelf, the most abundant species was G. gibberifrons, followed by P. georgianus. The study provides biological data (length frequency distribution, median size, sex ratio, gonad maturity stages, length-weight relationship) on the main species captured during the survey, and the oceanographic characteristics (depth profiles of temperature, salinity, density) obtained with CTD around the South Orkney Islands.

Published in

Latin American Journal of Aquatic Research

2020

Authors

Arana, P.M., Jones, C.D., Alegría, N.A., Sarralde, R., Rolleri, R.

Institutions

Institute of Marine Research Norwegian Polar Institute British Antarctic Survey National Institute of Fisheries Science Chonnam National University Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences Institute of Fisheries and Marine EcologyNational Antarctic Scientific Center of Ukraine Limited liability company “IKF” Australian Antarctic Division CCAMLR Antarctic Ecosystem Research Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric AdministrationAssociation of Responsible Krill harvesting companies (ARK) AKER Biomarine AS

Methods

DataAcousticBiological sampling

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