Procedures to estimate reproductive traits of fish by combining field surveys and tank experiments
2006
Kurita, Y.(Tohoku National Fisheries Research Inst., Shiogama, Miyagi (Japan))
Problems in examining reproductive traits of fish species by field surveys and the advantages of tank experiments were reviewed. Required tank experiments differ due to the maturation-spawning type of the studied fish. For asynchronously maturing species which spawn many batches in a spawning season, rate of degeneration of postovulatory follicles (POF) in relation to temperature, diel changes in both final maturation and spawning, and the stage of spawning are required to be clarified by tank experiments. While for group-synchronously maturing species which spawn one or several batches, oocyte growth rate and the duration of atresia both in relation to temperature are required to be clarified by tank experiments. Effects of ration size and feeding period on the number of spawning eggs are also important issues to be examined. While tank experiments are very useful methods, they have risks of producing biased results because of the artificial environment and food. Thus, field surveys and tank experiments should be concurrently carried out to allow comparison and validation of results.
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