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Effect of initial age variation on production of Florida red tilapia fry under intensive, brackishwater tank culture
Author(s) -
ELLIS S.C.,
WATANABE W. O.,
HEAD W. D.
Publication year - 1993
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/j.1365-2109.1993.tb00621.x
Subject(s) - biology , stocking , zoology , tilapia , hatchery , fishery , feed conversion ratio , cannibalism , body weight , fish <actinopterygii> , ecology , larva , endocrinology
. Growth and survival were compared among uniform‐ and mixed‐age groups of Florida red tilapia fry during sex reversal in brackishwater (12ppt) tanks, under commercial‐scale hatchery conditions. Three treatment groups of post‐yolksac (i.e. free‐swimming) stage fry of different age compositions were compared: (1) 100% fry collected at the free‐swimming stage (FSF); (2) 100% fry obtained through artificial incubation of eggs and non‐swimming sacfry (ENS); and (3) a mixed group consisting of 50% of each type (FSF+ENS). Fry were stocked into 530–1 cylindroconical tanks at a density of seven fish/l (3700/tank) and reared on an androgen‐treated diet for 30 days. While specific growth rates (range = 17·1–17·8% body weight/day) did not differ (P > 0·05) among treatments, significant (P < 0.05) differences were observed for survival and feed conversion ratio (FCR). ENS showed highest survival (76·8%) and lowest FCR (1·14), FSF showed intermediate survival (59·2%) and FCR(l·33), while the mixed‐age group (FSF+ENS) showed lowest survival (38·5%) and highest FCR (1·70). Under all treatments, a majority of fry losses were attributed to cannibalism. A highly significant ( P < 0·001) negative regression between survival and coefficient of variation of initial weights (CV = SD/X̄) indicated that cannibalism was reduced by minimizing age/size variation at stocking. The CV of initial weight may be a useful parameter for predicting fry survival under intensive tank culture.