Author(s): Pavithra Hegde, Padma S Hidkal, Deepak Shinde, Gayatri B Gaikwad, Ganesh C.B

Abstract: This study examined whether chronic exposure to mild hypoxic condition can limit growth and survival in the mosquitofish Gambusia affinis. Exposure of fish to mild hypoxic conditions (4.0 mg O2/L) for a period of 25 days resulted in reduction in mean body weight gain, specific growth rate (SGR), survival rate and protein efficiency ratio (PER), whereas the feed conversion ratio (FCR) remained high compared to those of controls on day 25. On the other hand, re-exposure of fish to normoxic condition (between days 26-40) after initial exposure to hypoxia for 25 days partially improved the mean body weight gain, SGR, PER and FCR values, but not survival rate. These results indicate that chronic moderate hypoxic condition causes reduction in growth and survival rate by interfering with the efficacy of feed conversion into biomass in G. affinis. It is suggested that monitoring of optimum dissolved oxygen levels is criticalrnfor attaining maximum growth and survival in mosquitofish culture.

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