Reproduction of the squid « Loligo vulgaris » off the South Atlantic coast of Morocco

Abstract

This paper focuses on the study of the squid Loligo vulgaris (Lamarck, 1798) reproduction, in the Atlantic southern waters of Morocco (Saharan bank) using data obtained from bottom trawls surveys performed by the Research vessel during the period 2000–2014 (springs and autumns seasons). Results shows a marked seasonal periodicity and an irregularity of the spawning periods.L.vulgaris hatched throughout the year with two distinct peaks, in spring which is the main breeding period, and in autumn.The sizes at first sexual maturity (L50%) of population squid defines the size at which half of the population (50 %) is mature for each sexes. During spring season squid individuals are characterized by smaller sizes at sexual maturity (males: 15,4 cm; female: 19,16 cm) than those recorded during the autumn season (males: 24,5 cm; female: 21,12 cm). Likewise, squid males are characterized by a more advanced maturity than the one of females, especially during the spring season, this can be explained by environmental factors mostly temperatures, which affect maturity.In the autumn season, the sex ratio is in favour of females in the smaller sizes below 5 cm. At the intervals of 6 to 19 cm and over 30 cm of mantle length, the sex ratio becomes exclusively in favour of males. Unlike the spring season the sex ratio for small sizes and sizes greater than 29 cm from the mantle is in favour of males.The length-weight relationship was calculated from biological data collected in surveys. There is a significant correlation between these two variables. The relative weight-length constant b is lower in males than in females.