On reproduction and age of the squid Loligo vulgaris from the Saharan Bank (north-west African coast)

Abstract

Loligo vulgaris (Cephalopoda: Loliginidae) is a commercially important species in the cephalopod trawl fishery in the Saharan Bank (21–26°N). This study on squid in central-east Atlantic waters aims to examine some important aspects of its reproductive biology. In the period from May 1993 to April 1994 monthly samples of L. vulgaris were collected from this commercial trawl fishery. The maturation pattern for males and females was described from the proportion of immature, maturing and mature animals in the samples and using a maturation index. A range of reproductive indices derived from the morphometrics of the somatic and reproductive systems were also estimated to provide comparative information. The proportion and an abundance index of mature and immature animals in commercial landings in the period 1983–1994 were calculated to provide comparative results of maturity and recruitment respectively. Peaks of mature animals were mainly seen between November and January. The summer months exhibited the maximum recruit abundance. Age determinations were also undertaken in order to obtain the hatching peaks and to complete the proposed life cycle of L. vulgaris on the Saharan Bank. A main hatching peak was observed in spring, particularly in May. The age–size relationship suggests differences related to sex and possibly to hatching season. The wide range of size at maturity observed in male L. vulgaris is analysed and discussed. Males showed a seasonal pattern in size at maturity. The dorsal mantle length–body weight relationship and the sex ratio were determined. The sex ratio exhibits a seasonal pattern in relation to body size. Results are compared with information on this species from European waters.

Patrones espaciales y temporales en talla y maduración de <i>Loligo plei</i> y <i>Loligo sanpaulensis </i>(Cephalopoda: Loliginidae) en aguas del sureste de Brasil, entre 23°S y 27°S.

“…Sexual dimorphism in size is well known in loliginids, and males of many species show larger maximum sizes than females (Moreno et al, 1994;Raya et al, 1999;Rocha and Guerra, 1999;Perez et al, 2002). This was clearly seen in the present study for both Loligo species.…”

“…Appropriate standard indices of maturity and reproductive activity were tested before adopting the gonadosomatic index (GSI) (sensu Macy, 1982;Raya et al, 1999;Perez et al, 2002), which is defined here as:…”

Embryonic life of the loliginid squid Loligo vulgaris: comparison between statoliths of Atlantic and Mediterranean populations

“…Studies on the age and growth of L. vulgaris from statolith analysis have estimated the duration of their post-hatching life to be about 1 yr, i.e. 240 to 396 d (Natsukari & Komine 1992, Arkhipkin 1995, Bettencourt et al 1996, Raya et al 1999, Rocha & Guerra 1999. Statolith analysis has proved to be the best tool for estimating loliginid age and growth of wild populations, with nearly all studies focusing on analysis of the post-hatching area of the statolith (see the reviews Jackson 1994 andO'Dor 2001).…”

“…the East Atlantic and the Mediterranean Sea. Statolith collections from previously published studies on L. vulgaris age and growth (Arkhipkin 1995, Raya et al 1999, Rocha & Guerra 1999 were analyzed, as well as newly collected material. From these aged statoliths it was possible to estimate by back-calculation the respective hatching dates and the sea temperature ranges recorded for each geographic region at hatching.…”

Reproductive activity of the tropical arrow squid Doryteuthis plei around São Sebastião Island (SE Brazil) based on a 10-year fisheries monitoring

“…Previous studies on loliginids reported that size-at-maturity in squid can vary dramatically, depending on the location and time of collection of samples (Raya et al, 1999;Perez et al, 2002;Rodrigues and Gasalla, 2008). The size-at-maturity of squid caught by the shrimp trawling off the coast of São Paulo and Santa Catarina, was relatively smaller than the ones found in SSI by the present study.…”