Changes in lipid classes and trypsin activity during the early development of brook charr, Salvelinus fontinalis (Mitchill), fry
1998
Roche-Mayzaud, O. | Mayzaud, P. | Audet, C.
Fertilized eggs of brook charr, Salvelinus fontinalis (Mitchill), (Nashua x Baldwin domestic strains) held for 86 days under laboratory conditions from eggs to fry were split into three groups: FWF2, FWF3 and SWF2. Breeders originated from the same broodstock, but rearing procedures were different: FWF2 and FWF3 were always kept in fresh water, whereas SWF2 had spent the previous summer in sea water. The SWF2 and FWF2 females were sexually mature before the FWF3 females. The feeding experiment started 16 weeks after fertilization. Juveniles were fed with the same commercial pellets at three different levels, a complete ration (R1) and two restricted rations, 50% and 25% of R1. Eggs and fry were analysed for size, dry weight, total lipids, lipid classes (polar lipids, cholesterol and triglycerides), soluble proteins and trypsic activity. Although dry weight, mean length, soluble protein and trypsic activities increased with food availability, lipid changes showed a permanent use of the endogenous reserve. No lipid synthesis was detected in any developmental stage, even though exogenous food sources were used. When the 25% restricted ration was given, fry mortality increased. Unexpectedly, fry survival tended to increase in individuals from small eggs. The data from this study showed that reserve distribution and its use can improve the resistance of fry hatching from small eggs and prompt better survival despite changes in the nutritional environment. The two factors related to the breeders, summer environmental rearing conditions and sexual maturation time, had significant effects on the response of progeny to feeding conditions.
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