Reproductive cycle and population structure of Loligo sanpaulensis of the northeastern coast of Patagonia

Abstract

The squid Loligo sanpaulensis is distributed from southern Brazil to northern Patagonia. Previous studies have been conducted on the reproduction of this species in northern and central areas of its distribution. In northern Patagonia, lower and more variable temperatures were expected to cause sharper patterns in the temperature-regulated aspects of the reproduction. Periodic sampling was conducted from December 1996 to July 1999, and main biological characters and maturity stages were registered. Average mantle length (ML) was 55.1 mm (n = 1455). Large specimens were most abundant in November–March and small specimens were found in April–July. Sex ratio was significantly different from 1:1 (10 females:7 males). Mean ML at maturity was 65.3 mm in males and 77.6 mm in females. Mature specimens and recruits were found in summer. During fall, the largest size classes disappeared and juveniles were abundant. Throughout winter, juveniles progressively disappeared, and recruits were present. In late spring mature specimens entered the sampling area. A single spawning season from late spring to summer was observed. The disappearance of the largest size classes occurred three to four months latter than that reported for Mar del Plata (38°S).