MercoPress. South Atlantic News Agency

Scientists carry out research at sea aboard FPV Dorada

SCIENTISTS from the Fisheries Department have been reporting on a research cruise they carried out last month.

On October 4, Fishery Patrol Vessel Dorada left Stanley for the 14 day scientific survey. Up to four bottom trawls and three oceanographic stations were conducted daily around the south and south-west of the Islands. Seven scientists from the Fisheries Department were involved with the research cruise.

The main aims of the cruise were to initialise a skate tagging and release programme, investigate red cod and its spawning grounds, survey the spawning grounds of redfish and continue oceanographic studies of the Falkland shelf.

The cruise gave a great opportunity to start a new departmental programme investigating the migration of skates. Around 16 species occur in the Falkland waters with the more common species fished by Korean trawlers.

The programme involved tagging skates with external tags that can identify them after being re-captured. "Six hundred and fifty-nine skates were tagged and released over a wide area. It is hoped that one in ten of these animals will be recovered by the commercial fleet and the data will be able to tell us something about their migration patterns," explained Joost Pompert.

He added, "It is intended that this programme will be long term and continued on subsequent research trips."

Redcod is an important commercial resource and is often fished to the south-west of the Falkland Islands. During the cruise several catches resulted in a number of large females ready to spawn their eggs.

Dr Paul Brickle explained, "We collected the ovaries from large females to bring back for laboratory investigations. They will be used to identify the fecundity by counting the number of eggs each female is capable of spawning."

He added, "This kind of information helps us to build up a better picture of the numbers of redcod in the Falkland waters which over the last few years have been declining."

Three research cruises have already been conducted on Dorada this year. During this trip and the previous trips, detailed oceanographic surveys were carried out. Sensors deployed from the vessel record oceanographic features such as salinity, temperature, oxygen and chlorophyll content.

These profiles can be linked to the fisheries data and are a useful tool in explaining fluctuations in species abundance.

The final aim was surveying redfish; a small spiny and tasty sea perch found in rocky areas. It is widely distributed on the Patagonian shelf but is not a major commercial species.

"The last trawl close to the Jason Islands yielded a catch in which high proportions of females were ready to spawn their eggs. Continued collection of data will allow us to build up a good picture of where and when this fish spawns in the Falkland waters," fisheries observer Sarah Crofts explained.

The team accumulated data on many other species. Work continued on loligo squid and was particularly successful in collecting data from spawning stocks inhabiting shallow waters.

One catch in Queen Charlotte Bay produced an unusual species of rockcod. Sarah, who spotted the fish, commented, "This fish has only ever been seen once before in the Falkland waters in 1913, it is obviously quite rare and probably inhabits shallow water." Chief scientist Dr Alexander Arkhipkin concluded, "The trip produced some interesting and worthwhile data, hampered only by a few days of bad weather, all in all it was a success." (PN)