Open AccessPatchiness Formation and Development of Schooling Behavior in Pacific Threadfin Polydactylus sexfilis Reared with Different Dietary Highly Unsaturated Fatty Acid Contents
Author(s) -
Masuda Reiji,
Ziemann David A.,
Ostrowski Anthony C.
Publication year - 2001
Publication title -
journal of the world aquaculture society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 60
eISSN - 1749-7345
pISSN - 0893-8849
DOI - 10.1111/j.1749-7345.2001.tb00454.x
Subject(s) - biology , eicosapentaenoic acid , larva , ichthyoplankton , hatching , docosahexaenoic acid , metamorphosis , fatty acid , juvenile fish , zoology , juvenile , fishery , food science , fish <actinopterygii> , ecology , polyunsaturated fatty acid , biochemistry
.— Nutritional condition in larval fish culture has generally been evaluated based on growth and survival, and stress tolerance by air exposure. Here we made direct observations of fish in rearing tanks to estimate the quality of the fish. Pacific threadfin Polydactylu.s sexfilis larvae were reared with rotifers and Artemia nauplii enriched with three levels of highly unsaturated fatty acids (HUFA). The three levels were defined as no‐, medium‐, or high‐HUFA groups, in which the fatty acids emulsions contained 0, 30, or 50%. respectively. of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). The formation of patchiness (dense aggregations of fish on the surface) and development of schooling behavior were observed in four replicate rearing tanks for each feed treatment. Patchiness was formed in every tank with the highest densities of 60–250 fish/L on day 7–8 posthatch. Both medium‐HUFA and high‐HUFA groups showed schooling behavior at 19 d after hatching, whereas fish in the no‐HUFA group did not form schools even at day 25. The body lengths of fish from each group were not significantly different, although the no‐HUFA group suffered high mortality after day 20. Our results suggest that HUFA deficiency has a serious negative impact on P. sexfilis during metamorphosis rather than during the early larval stage. We also consider that direct observation rather than stress tests by air exposure may be an effective tool to measure the quality of juvenile fish.