An evaluation of specific ionic and growth parameters affecting the feasibility of commercially producing red drum (Sciaenops ocellatus)

Abstract

Typescript (photocopy).Seven experiments were conducted to determine whether red drum might be commercially cultured in inland salt or fresh waters. Four of these were to define specific environmental requirements, absolute and survival ranges, for calcium and magnesium. Two initial and two secondary studies were conducted in salt and fresh waters differing in concentrations of calcium and/or magnesium. Red drum weighing 1-3 g were stocked in each experimental trial at 15/114 l tank; treatments had three replicates. Environmental calcium significantly affected red drum survival in salt and fresh waters; magnesium produced no discernible performance effects. In saltwater (35 g/l total dissolved solids (TDS)) experiments, fish in treatments containing less than 176 mg/l calcium exhibited 100% mortality within 96 hours. Best survivals, 78-84% at 96 hours, were observed in treatments containing 340-465 mg/l calcium. Red drum stocked in fresh water (0.56-1.9 g/l TDS) with calcium concentrations 1.7 mg/l or less performed poorly (0-33% survival within 96 hours). Growth and survival were not significantly affected when calcium was between 9-407 mg/l. Ammonia-nitrogen concentrations were significantly higher in saltwater treatments containing trace magnesium. Generally, fish from initial fresh water and saltwater experiments had significantly better long term (42 day) survivals than those from the second set of experiments. This appeared to be related to the use of acid washed biofiltration media (removal of essential trace components perhaps) in the second trials. Three growth feasibility studies were performed, two in ponds with hard (120 mg/l calcium) fresh water and one in a low salinity (5 g/l TDS) closed system. Pond results suggested that red drum fingerlings (35 g) performed better, mean weight 450 g with 90% survival after 215 days, than fry (4-6 g), mean weight 18 g with 9-15% survival after 106-115 days. Apparently, floating catfish feed was not consumed, while crawfish and tilapia fry were. Closed system research demonstrated that red drum fed commercial salmon feeds (44-48% protein) displayed exponential growth. It appears that red drum fingerlings offered crawfish forage or commercial salmon formulations can be pond cultured to market size in one season