Alimentação, ciclo reprodutivo e associação de Loligo sanpaulensis Brakoniecki, 1984 (Cephalopoda: Loliginidae) com a ictiofauna demersal na plataforma costeira do Cabo Frio, RJ

Abstract

The reproduction and feeding of Loligo sanpaulensis Brakoniecki, 1984 and its relationship with demersal fish assemblages was studied from specimens collected in the continental shelf off Cabo Frio region (23ºS 42ºW). A total of 71 samples were taken aboard the R/V "Suboficial Oliveira" between November 1986 and October 1988, using an otter-trawl with 10 m footrope and a 25 mm cod-end mesh size, towed over 30, 45 and 60 m isobaths. The dorsal mande length, total weight, sex and maturity stages were recorded from 1594 specimens. The degree of stomach and digestive caecum fulness were examinated on 859 specimens and 351 squids had their stomach contents analysed. Loligo sanpaulensis occurred over the shelf in all seasons, with a mean catch of 39.2 ind/hour trawling. Best yields were obtained at 45 m depth with an average catch of 116 ind/h during the two years of sampling. Both abundance indicators (kg/h and ind/h) were markedly associated with the upwellings of Subtropical waters, namely South Atlantic Central Water, at temperatures between 16ºC and 18°C. Length-weight relationships were different among males P = 0.00049 CM 2.4065 and females P = 0.00030 CM 2.5436_ Recruits and mature animais altemated temporal and spatialy. Indirect evidence suggests that a migratory pattem may be envolved in the reproductive cycle. The variation of the gonadossomatic index indicated that the population undergoes two broad periods of sexual maturation along the year. The onset of maturation begins in April and October, reaching a maximum around August and February, respectively. Spawning is likely to take place in late summer and during winter. Spent females were not found, although egg masses occurred in several occasions at 30 meters. Stomach contents analysis showed that fish, planktonic crustaceans ( eufausids) and squids were taken as food. Crustaceans were more frequent in juveniles and sub adults, while fish was the principal prey in adults. The feeding intensity increased with size up to the length of first maturity, declining at greater sizes. Feeding activity was associated with the more productive subtropical water and lower temperatures. Positive covariation was found between L.sanpaulensis and Trachurus lathamiand Mullus argentinae.Cluster analysis applied to the species and stations data revealed that temperatures and depth were important factors affecting the assemblages. The main species association formed by L.sanpaulensis, Merluccius hubbsi, Lophius gastrophysus, Porichthys porosissimus and Dules auriga remained the sarne during the two periods of study, at a 0.6 coincidence levei. Seasonaly, Trachurus /athami, Percophis brasi/iensis, Mullus argentinae and Pagrus pagrus integrated the main association, according to the intensity of the upwelling events.