Nutritional and animal husbandry aspects of rearing early life stages of Eurasian perch Perca fluviatilis

Abstract

The Eurasian perch Perca fluviatilis larviculture can be divided into three major areas: the ontogeny of the digestive system, the nutritional requirements and, the growth, production and cannibalism in different culture systems. Ontogeny of digestive system of larvae and juveniles, i.e., the morphological and histological characteristics of the digestive system (including the digestive tract, liver, pancreas and pyloric caeca), is described from hatching up to 1-month-old. Preliminary data on proteolytic activities (pepsin, trypsin and chymotrypsin) during larval growth and weaning on dry diet are also provided. The effects of diet (type of live prey, live food vs. dry or mixed diet) on survival and growth of perch are compared and discussed. In many perch larvae, mouth size constitutes a limiting factor to an optimal utilization of Artemia nauplii from hatching onwards. However, this diet can support satisfactory survival and growth in larger larvae, usually obtained from large breeders. Although perch larvae ingest dry food after yolk sac absorption, survival and growth rates are very low at that stage, compared with results obtained with live food and mixed diet. Weaning experiments performed at different larval and juvenile body weights demonstrated that fish can be trained to accept and to use a dry diet efficiently as a unique food supply starting at 50 mg. Some data related to the nutritional requirements (feeding level, dietary protein, fatty acids) of perch larvae are provided. Juvenile production in different culture conditions (fertilized ponds, green water tanks, recirculated system) indicated that the optimal system for the production of weaned fry was the semiintensive one. In this method, combining an enhanced production of natural plankton and a regular supply of Artemia nauplii and dry food after 44 days of rearing, survival rate varied from 9.2 to 38.6% and body weight from 350 to 950 mg, depending on temperature and stocking densities (400–4000 eyed eggs m−2).