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.

Analysis of the cycle of reproduction of Sardina pilchardus (Walbaum, 1792) off the Moroccan Atlantic coast

This work focuses on aspects of reproductive biology of Sardina pilchardus from the Atlantic coast of Morocco. The mean values of batch fecundity estimated for the species is 23150(+/-1301) oocytes for a mean size of 19.5(+/-0.49) cm, the mean relative fecundity being 346(+/-7.34) oocytes per gram of female without ovary. Batch fecundity increases with total length and body weight without ovary. Sizes at first sexual maturity (L50) are reached for males and females at 15.8(+/-0.29) cm and 15.8(+/-0.35) cm, respectively. The spawning period for the population extends between October and July and the spawning peak occurs from October to February. However, the small sardines (14.5-17 cm) in their first reproduction spawn between November and June, whereas larger fish (17.5-25 cm) spawn between October and July. The factor of condition (K) increased in summer during the sexual resting phase. It is weak in winter during the period of reproduction. Regarding, the sex ratio, there was no significant difference in the number of males and females.