Growth and Energy Expenditures of Eurasian Perch Perca fluviatilis (Linnaeus) in Different Temperatures and of Different Body Sizes

Carin Magnhagen,Anders Alanärä,Åsa Strand

doi:10.4172/2155-9546.1000114

Abstract

To calculate the theoretical daily energy requirement of fish, information about the daily growth increment and the amount of digestible energy needed (DEN) to obtain one unit of biomass gain is required. The thermal unit growth coefficient (TGC) can be used for estimation of the daily growth increment. TGC is thought to be less affected by body size of the fish and temperature than the specific growth rate (SGR). However, there are some indications that the TGC may not be as stable as previous studies have shown. Furthermore, according to the theoretical background, DEN should increase as fish body size increases and with temperature. However, some data indicate that the DEN for percid fish may be unaffected by both these factors. The main objectives of this study was to estimate the effects of temperature and fish body weight on growth (TGC and SGR) and digestible energy need (DEN) of the Eurasian perch Perca fluviatilis (Linnaeus). In two separate laboratory experiments, feed intake, growth and energy expenditures were measured at either different temperatures (8.5-27.1oC) or for fish of different body sizes (20-110g). TGC and SGR proved to be affected by temperature and body size of the fish, while DEN was only affected by body size. The advantages with TGC for growth model construction thus seem to be less apparent than earlier believed. Thus, for evaluation of the theoretical daily energy requirement of fish, a growth model including both temperature and body size of fish, and an energy expenditure model including body size of fish is required.

Highlights

To calculate feed requirements of farm animals, approaches based on energetic principles are frequently used
Our prediction that thermal unit growth coefficient (TGC) of perch is unaffected by temperature and body size was not fulfilled
TGC of perch was affected by temperature in a similar way as specific growth rate (SGR), and follow the classical bellshaped curve of increasing growth rate with increasing temperature to an intermediate temperature, after which the growth rate declines

Summary

Introduction

To calculate feed requirements of farm animals, approaches based on energetic principles are frequently used. The extent of nutritional knowledge is much more developed compared to that of fish, and there is a long tradition to utilize this knowledge for calculation of the daily feed allowances of the animals [1,2]. The energy requirements of fish has traditionally been estimated by constructing complete energy budgets, balancing energy intake against energy expenditures such as faecal production, nitrogen excretion, metabolism and growth [3,4,5,6]. The proposed model was based on two major components; one that estimates the daily growth increment (g) of the fish and one that calculates the amount of digestible energy needed (kJ) to obtain one unit of biomass gain (g) of the fish

Objectives

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Results

Conclusion