Survival and growth of juvenile hatchery-reared spotted seatrout, cynoscion nebulosus, stocked into rearing ponds at 2 and 9 days post-hatch

Abstract

Of concern to recreational fisheries is the growth and survival of hatchery-reared sport fish released for stock enhancement purposes. This study was conducted to evaluate the effect of water quality/source on growth and survival of larval spotted seatrout (Cynoscion nebulosus) reared in captivity. Trials were conducted both indoors under controlled conditions and in outdoor tanks. For the indoor trials, seatrout eggs were stocked into replicated (n = 4) 83-L tanks at 50,000 eggs/tank for either 2 or 9 days post-hatch (DPH). During this period, tanks received either filtered seawater, raw seawater, or filtered seawater containing marine microalgae. There was no significant difference (P>0.05) in survival of either 2 DPH (49.95 ± 13.6%) or 9 DPH (30.73 ± 14.2%) larvae regardless of water source. However, a significant difference was observed between the growth rates of 9 DPH larvae, as the larvae in the clear water treatment were significantly smaller (P = 0.01) than the two other treatments. Outdoor tanks (13,000-L) were stocked with 1,500 larvae (2 DPH or 9 DPH) (n = 3) which were reared for 30 days. Growth (TL) and survival rates in the outdoor tanks approximated 1.06 and 1.41 mm/day and 11 and 7.5%, respectively. There was no significant difference (P =0.15) in survival which was similar between the two age groups; a highly significant growth rate difference was shown. Results from this preliminary research indicate that current protocols used to rear juvenile spotted seatrout can be improved by increasing indoor rearing period.