CHANGES IN LIPID CLASSES AND TRYPSIN ACTIVITY DURING THE EARLY DEVELOPMENT OF BROOK CHARR, SALVELINUS-FONTINALIS (MITCHILL), FRY

Fertilized eggs of brook charr, Salvelinus fontinalis (Mitchill), (Nas hua x Baldwin domestic strains) held for 86 days under laboratory cond itions from eggs to fry were split into three groups: FWF2, FWF3 and S WF2, Breeders originated from the same broodstock, but rearing procedu res were different; FWF2 and FWF3 were always kept in fresh water, whe reas SWF2 had spent the previous summer in sea water, The SWF2 and FWF Z females were sexually mature before the FWF3 females, The feeding ex periment started 16 weeks after fertilization. Juveniles were fed with the same commercial pellets at three different levels, a complete rat ion (R1) and two restricted rations, 50% and 25% of R1, Eggs and fry w ere analysed for size, dry weight, total lipids, lipid classes (polar lipids, cholesterol and triglycerides), soluble proteins and trypsic a ctivity, Although dry weight, mean length, and trypsic activities incr eased availability, lipid changes showed a permanent use of the endoge nous reserve. No lipid synthesis was detected in any developmental sta ge, even though exogenous food sources were used. When the 25% restric ted ration was given, fry mortality increased, Unexpectedly, fry survi val tended to increase in individuals from small eggs. The data from t his 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 relat ed to the breeders, summer environmental rearing conditions and sexual maturation time, had significant effects on the response of progeny t o feeding conditions.