Relationships between somatic tissues, reproductive organs and fishing season in the commercially exploited European squid Loligo vulgaris from the western Mediterranean Sea

Loligo vulgaris samples were obtained monthly from October 2003 to December 2005 on board commercial trawlers from two ports (Cambrils and Roses) off the Catalan coast (NW Mediterranean). The main aim of this work was to understand what controls the onset of the maturation process in L. vulgaris: size, nutritional state, fishing season, or a combination of some of these elements. We investigated the relationships between gonad weight (ovary/testis) and total body weight, eviscerated weight, mantle length, digestive gland weight, nidamental and accessory glands weight and capture date (month). Generalised Additive Models (GAMs) were applied. The results indicated that gonad weight variation, in both the ovary and testis, was explained by the month of capture. There was also evidence of an opposite seasonality between gonads and eviscerated weights, possibly indicating remobilization of somatic mantle tissue to grow the gonads in both males and females. There was a positive relationship between ovary weight and size, measured as dorsal mantle length (DML), at DML >14 cm, which indicates the size at which maturation starts. The digestive gland would not take a relevant participation as an organ of storage and therefore in the energetic expense during the process of maturation. Nidamental and accessory reproductive glands weight was also positively related to ovary weight. The relationships between the different variables analyzed were more complex in males than in females. They showed, however, a clear energy transfer between testis weight and spermatophoric complex weight. The results also suggested the existence of two or more growth patterns leading to different sizes at maturity in L. vulgaris males.