About 10 years ago New Zealand decided that the Antarctic toothfish, known to the rest of the world as Chilean sea bass, should be extracted from the Ross Sea. It’s the last place left on Earth where the ocean fish have not been depleted. After five years of “experimental fishing” by NZ, a full-fledged fishery was launched. This now includes about a dozen countries and 21 fishing vessels. Despite their charter to protect the living resources of Antarctica’s seas, CCAMLR instituted no procedures for monitoring the impact of the fishery on the ecosystem. So we’ve taken it upon ourselves to come up with some procedures by which this can be done.

Adult Chilean sea bass (on snow) and subadult (held by person) caught through a hole in the fast ice of McMurdo Sound.

Antarctic silverfish, which both Chilean sea bass and Weddell seals eat in the Ross Sea.

Weddell seals eat a lot of toothfish and the best-known population of these seals, and perhaps the best-studied pinnipeds population in the World, is in southern McMurdo Sound, in the vicinity of Cape Royds. Thus, with the seal folks from Montana State University, we submitted a procedure to CCAMLR last summer to monitor the seal population using aerial photography. The idea is that as more Chilean sea bass are taken from the Ross Sea, the seal population should change. Seal numbers would either decline because there are fewer sea bass to eat or increase because with fewer sea bass there would be more silverfish for the seals to eat (the fish and the seals also compete for Antarctic silverfish).

Weddell seal mom and pup, Erebus Bay, McMurdo Sound

Weddell seal with toothfish (Chilean sea bass) that it captured, and which it is beginning to consume.

CCAMLR accepted our aerial protocol but then told us we had to demonstrate its utility in the field. This led to our aerial flight. To say the least, with aerial photography having been used to count seals in the Arctic for decades, our counts from the air were close in number to those counted on foot two days previously. We’ll now submit a report to CCAMLR and hopefully the fishing industry will take the responsibility to begin at least one measure to keep track on how their fishing may affect the ecosystem of the Ross Sea.

Weddell seals spread along a tide crack in Erebus Bay; view from 1000 ft.