Chapter one

Introduction

It is a well-known phenomenon that all changes in a population depend onreproduction. growth and mortality. The last two processes are mostintensely manifested in the early developmental stages (Hjort. 1914; Allen.1951; Marr. 1956; Bernatowicz et al.. 1975; Mahon et al.. 1979; Eldridge etal., 1981a. b; and many others). Planktivorous fish larvae are among themost efficient predators at transferring biomass from one particle size to alarger size (Borgmann and Ralph. 1985). Therefore the early life history offish was recognized as one of the key issues in fishery science (Azeta. 1981;Kernehan et al.. 1981; Sherman and Lasker. 1981; Nielsen et al.. 1986;Viljanen. 1988). Reproductive strategies and adaptations for early develop­ment define the ecological guilds of fishes proposed by Balon (197 5a).Evaluating studies on early life history of fishes. Alderdice (1985) found thatthey often receive less recognition and support than they merit. and drewattention to the multiple advantages of such studies when they areassociated with practical goals. He produced a list of ten activities by whichthese goals could be achieved; they included study of the bioenergetics ofgrowth and development, and of the physiological ecology of early lifestages.

In the last decade a number of papers have appeared pertaining to ecologyenergetics and the transformation of matter in fishes (reviews: Elliott, 1979,1982; Brett. 1979: Brett and Groves. 1979; Shatunovskij. 1980; Fischer.1983; Tytler and Calow. 1985; Gershanovich et al.• 1987). They wereconcerned with postlarval developmental periods: earlier development hasbeen less attractive for such studies because the processes occur rapidly. arecomplicated. and the fish are small. Information on energy and mattertransformations during the early development of fish is therefore far fromcomplete.

In studies aimed at optimization of egg incubation in hatcheries andrearing of fish larvae in aquaculture. survival and growth are most oftenevaluated. Morphometric. histological. physiological or bioenergetical inves-

E. Kamler, Early Life History of Fish© Chapman & Hall 1992

2 Introduction

tigations, or studies of the causes of size variability, are rarely employed.These methods can provide information on mechanisms that produce theobserved effects. Such an approach can be more fruitful, and less expensive.than blindly manipulating numerous variables in search of optimal combin­ations (e.g. by composing artificial diets for fish larvae).

The topics discussed in this book are energy and matter transformationduring fish gonad formation, the endogenous feeding period. and the larvalperiod, as well as energetical aspects of the feeding of fish larvae inaquaculture. Consideration is given to the specificity of these transforma­tions, as compared with analogous processes taking place during fishpostlarval development on the one hand and during reproduction and earlydevelopment of other animals, mostly aquatic invertebrates. on the otherhand. Attention is paid to the effects of endogenous and external factors.Methods are evaluated when necessary. An attempt has been made to coverboth Western and Eastern literature.