Results of a longline survey on seamounts in the southeast Atlantic and in Subarea 48.6 and Division 58.4.4
A bottom longline survey took place between 22 October and 1 December 1997, and several seamounts were surveyed to the south of Africa: close to the Antarctic Polar Front (Meteor Bank) and in the CCAMLR region (Shona and Spiess seamounts, the western slope of Bouvet Island, Ob and Lena Banks). Samples were collected from longlines set perpendicularly to the isobaths and in depths down to 1 500-2 000 m. Numerically, catches were dominated by Patagonian toothfish (Dissostichus eleginoides), with 2 822 individuals caught (83% of total catch). Grenadiers of the genus Macrourus were the second most abundant taxon (248 individuals). The total catch by weight was 21.430 tonnes, of which D. eleginoides comprised 20.502 tonnes (96%). The seamounts differed substantially in relation to seabed topography, species composition of catches, and relative abundance and size structure of D. eleginoides caught. Lengths of individual D. eleginoides generally increased with depth although this trend may be confounded by the presence of local seabed features, and juvenile fish in nearby shallow water. The sex ratio of immature D. eleginoides less than 90 cm total length did not significantly vary from 1:1. Females accounted for 70% of individuals of more than 90 cm in total length. The stratum with the highest catch (weight) per unit effort was 600 to 800 m, although absolute values varied between areas. Catch per unit effort ranged from a maximum value of 359 kg/1 000 hooks on Ob and Lena Banks to a minimum of 185 kg/1 000 hooks on Meteor Bank.