Behavioral Ontogeny of Marine Pelagic Fishes with the Implications for the Sustainable Management of Fisheries Resources

Behavioral ontogeny of marine pelagic fishes is reviewed in the context of sustainable fisheries resource management. In carangid fishes, development of sensory organs corresponds with their basic behavior such as phototaxis and optokinetic response, whereas the onset of schooling requires the development of the central nervous systems (CNS). Because docosahexaenoic acid (DHA) is indispensable for the development of CNS, quality as well as quantity of prey is important for the development of behavior and thus survival. Among common pelagic fishes, chub mackerel, Scomber japonicus, had the best growth performance and their cruise swimming speed was remarkably fast. Japanese anchovy, Engraulis japonicus, were slow both at cruise and burst swimming speeds, and were extremely vulnerable to predation by jellyfish. Jack mackerel were slow at cruise swimming speed, but they can make use of jellyfish as a refuge and as a prey collector. Each biotic and abiotic environmental factor, such as water temperature, the amount of phytoplankton, copepods and jellyfish, may work in a positive or negative way for each species, and this can be a driving force for the replacement of predominant fish species. Considering that there are always competition and predator–prey relations among different pelagic fish species, ecosystem based management is indispensable for the sustainable utilization of pelagic fishes. 2 Behavioral Ontogeny of Marine Pelagic Fishes for Sustainable Management of Fisheries Resources Aqua-BioScience Monographs VOL. 2 NO. 2 2009 then the ontogenetic changes of behavior in this species, described in Chapter 3, were compared to these morphological changes. Because developmental timing of schooling behavior (Chapter 3) was posterior to the morphological development of sensory organs (Chapter 2), development of the central nervous system was speculated to be the limiting factor for the onset of schooling. To test this hypothesis, feeding experiments using docosahexaenoic acid (DHA) enriched or deficient diets were conducted so that development of the brain was manipulated (Chapter 4). Chapter 5 focuses on the association behavior of jack mackerel, Trachurus japonicus, with jellyfishes, the ecological functions of which were revealed based on laboratory experiments and field underwater observations. Chapter 6 deals with ontogeny of behavioral characteristics such as swimming speed, schooling, and antipredator performance against jellyfish in common pelagic fishes (jack mackerel, chub mackerel Scomber japonicus and anchovy Engraulis japonicus). Emphasis was on the understanding of population fluctuation and replacement of predominance among these species which occurs in about a decade of a cycle in Japanese coastal waters. The final chapter provides perspectives towards the sustainable management of fisheries resources. In this monograph, fish body length was expressed either in total length (TL) or in standard length (SL) depending on the original data. SLs were about 83, 84, 86 and 88% of TL in early juveniles of striped jack, jack mackerel, chub mackerel and anchovy, respectively (Masuda R, unpublished data). 2. Morphological development of sensory and swimming organs and the central nervous system in the striped jack