PHOTOPERIOD CONTROL OF PUBERTY IN FARMED FISH - USE OF MOLECULAR TECHNIQUES TO STUDY UNDERLYING PHYSIOLOGICAL MECHANISMS

摘要

A major constraint in farming of fish is the timing of the first sexual maturation or puberty (Bromage et al. 2001). Sexual maturation results in reduced growth, regressive changes in harvest quality, increased susceptibility to diseases, and reducedfeed conversion efficiency, and ultimately increased production costs. The term puberty describes developmental processes that constitute the transition from an immature juvenile to a mature adult state of activity of the reproductive system (Schulz andGoos 1999). The two core components of the reproductive system are the gonads that produce germ cells as well as hormones, and the endocrine system that regulates the gonadal functions, the brain-pituitary-gonad (BPG) axis. Apart from the putative permissive factors related to body size, growth and/or adiposity, the question on how the quiescent state is of the BPG axis in juveniles is overcome has not yet been fully explained in mammals, and is rather unclear in fish. Photoperiod alteration has proveda simple and rapid way to delay puberty in farmed Atlantic salmon (e.g. Taranger et al. 1998). Promising results have also been obtained in other European farmed fish such as rainbow trout, Atlantic cod, Atlantic halibut and sea bass (e.g. Rodriguez et al. 2001). However, the photoperiod treatments are not always effective in salmon, and have to be optimized and commercialized yet in other species. To achieve this, a better understanding of the activation of the BPG axis during puberty and the effects of photoperiod on the BPG axis is needed.