NUTRITIONAL AND ANIMAL HUSBANDRY ASPECTS OF REARING EARLY-LIFE STAGESOF EURASIAN PERCH PERCA-FLUVIATILIS

The Eurasian perch Perca fluviatilis larviculture can be divided into three major areas: the ontogeny of the digestive system, the nutrition al requirements and, the growth, production and cannibalism in differe nt culture systems. Ontogeny of digestive system of larvae and juvenil es, i.e., the morphological and histological characteristics of the di gestive system (including the digestive tract, liver, pancreas and pyl oric caeca), is described from hatching up to 1-month-old. Preliminary data on proteolytic activities (pepsin, trypsin and chymotrypsin) dur ing larval growth and weaning on dry diet are also provided. The effec ts of diet (type of live prey, live food vs. dry or mixed diet) on sur vival and growth of perch are compared and discussed. In many perch la rvae, mouth size constitutes a limiting factor to an optimal utilizati on of Artemia nauplii from hatching onwards. However, this diet can su pport satisfactory survival and growth in larger larvae, usually obtai ned from large breeders. Although perch larvae ingest dry food after y olk sac absorption, survival and growth rates are very low at that sta ge, compared with results obtained with live food and mixed diet. Wean ing experiments performed at different larval and juvenile body weight s demonstrated that fish can be trained to accept and to use a dry die t efficiently as a unique food supply starting at 50 mg. Some data rel ated to the nutritional requirements (feeding level, dietary protein, fatty acids) of perch larvae are provided. Juvenile production in diff erent culture conditions (fertilized ponds, green water tanks, recircu lated system) indicated that the optimal system for the production of weaned fry was the semi-intensive one. In this method, combining an en hanced production of natural plankton and a regular supply of Artemia nauplii and dry food after 44 days of rearing, survival rate varied fr om 9.2 to 38.6% and body weight from 350 to 950 mg, depending on tempe rature and stocking densities (400-4000 eyed eggs m(-2)).