Reproductive Biology of Sardinella sp. (Sardinella aurita and Sardinella maderensis) in the South of Morocco.

BACKGROUND AND OBJECTIVE: Sardinella sp. has gained much attention lately because of its biomass increase, which might be the result of climatic changes occurring across the Atlantic sea. Little information is known about reproduction of these species particularly in the Moroccan Atlantic area. The objective of the this study was to explore some aspects of the reproductive biology of Sardinella in the South of Atlantic Moroccan coast.

MATERIALS AND METHODS: Monthly samples were collected during the period between February, 2015 and January, 2016 in the area between Cape Boujdor and Cape Blanc. The data collected concerned the measure of the total length, the weight, the gonad weight as well as the sex and maturity stages. The χ2 test was used to compare the differences between both sexes and the ANOVA test was adopted to analyze the data variation.

RESULTS: Sardinella sp. is a gonochoristic fish. The overall female to male ratio was not statistically different for both species (χ2 = 0.68 for Sardinella aurita and χ2 = 1.04 for Sardinella maderensis), although it varied seasonally and according to the length of the fish. The monthly changes in the gonadosomatic index and the macroscopic characteristics of gonads showed that round Sardinella in the South of Morocco spawns between February and July and between November and December with a spawning peak on April. For the flat Sardinella, it spawns between February and March and in July with a spawning peak on July. Females round Sardinella reach first sexual maturity at a smaller size than males (26.17 and 26.78 cm, respectively). Concerning the flat Sardinella, it was the opposite. Males reaching sexual maturity are smaller than females (20.75 and 21.76 cm, respectively).

CONCLUSION: It is concluded that the size at first maturity revealed that mature females in the South of Moroccan Atlantic Ocean were smaller than males for the round Sardinella and the opposite was observed for the flat Sardinella. The spawning of S. aurita presented a pick in April and for S. maderensis in July. As a shared stock these findings will be used for stock assessment in the North West Africa area.