Several indicators show that the world population is rapidly increasing with prospects of reaching close to 10 billion people in 2050. Optimal production of fish is a tentative goal to ensure human feeding and resources sustainability. The present study was performed on eggs of the silver carp, collected during the breeding season of consecutive years with different environmental temperature profiles at the Deroua Fisheries Station to evaluate the seasonal and inter-seasonal changes of eggs quality in order to promote a predictive marker for optimal production of silver carp. The viability of the obtained eggs was detected using ANOVA  followed by the Tukey test to analyze fertilization rate, embryos survival rate, and fry survival rate. Data analysis showed no significant difference in the fertilization and survival rate of the embryos during the two breeding seasons, and therefore these can not be used as an adequate criterion to predict the viability of the fry of silver carp. Although the survival rate of the fry did not change during the first season, it changed significantly during the second when there was an increase in the environmental temperature. This factor could be responsible for the disturbance of the females' oogenesis and consequently the degradation of the eggs' quality. The results showed that the fry survival rate could be used as a parameter to predict the yield of silver carp production rather than the success of fertilization and the survival of embryos. This paper discusses the importance and scope of this approach.

The present study is performed in order to determine the relationship between fatty acid (FA) profile of silver carp (Hypophthalmichthys molitrix) eggs and fertilization success, embryos viability and larval production. Mature unfertilized ova were collected during the reproductive season from 23 mature and healthy females, reared in Deroua fish farm (Morocco). Total lipids were extracted from ova sample and subjected to trans-esterification then the resulting fatty acids methyl esters were analyzed by gas chromatography tandem mass spectrometry (GC/MS/MS). The results showed that silver carp ova are dominated on total FA by docosahexaenoic acid (DHA) (21.21%) followed by oleic acid (21.07%), palmitic acid (17.71%) and eicosapentaenoic acid (EPA) (10.25%). During the breeding season, polyunsaturateds (PUFAs), monounsaturateds (MUFAs) and saturated fatty acids (SFA) didn’t show any significant difference. Moreover, within the PUFAs, the n-3 series were more abundant than the n-6 series, the total mean was 31.57 ± 1.01% and 5.33 ± 0.32%, respectively. No correlation was between fatty acids and the fertilization success. Maternal weight has effect on the levels of oleic acid (C18:1), arachidonic acid (C20:4) and docosahexaenoic acid (C22:6) in the egg whereas levels of palmetoleic acid (C16:1), eicosapentaenoic acid (C20:5) and docosahexaenoic acid (C22:6) are related to female age.

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Sander lucioperca hasbeen introduced in Morocco since 1939. This noble fish has shown a good ability to acclimatize to Moroccan conditions and has developed well [1]. The present study examines diet composition and predator-prey relationships that are dependent on size and weight between sander and its preys during the period October 2018-April 2019. Stomach contents of 287 specimens, whose size varies between 17 and 72 cm, from Al-Massira dam, wereanalyzed. The results showed that Sander feeding is composed of six categories of prey, the most important species was the Blue gill (Perch) with an occurrence index equal to 14.9%, the occurrence indices for other preys were respectively : Pike perch (8.01%), Tilapia (5.57%), Roach (0.69%), Black bass (0.69%) and Common carp (0.69%). It has been found that the total length of the preys increases with that of the Pike perch. Thus, the Pike perch is able to ingest preys of big weight and size. We also revealed that cannibalism was high, indicating a lack of forage fish in this lake.

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