TOWARD COMMERCIAL PRODUCTION OF PIGFISH Orthopristis chrysoptera FOR THE LIVE BAIT INDUSTRY: EFFECTS OF STOCKING DENSITY ON POND GROW-OUT

Lee A. Fuiman*
 
Fisheries and Mariculture Laboratory
University of Texas Marine Science Institute
Port Aransas, Texas 78373  
lee.fuiman@utexas.edu
 

Red claw crayfish Pigfish are a popular marine baitfish in the southeastern United States, and the entire supply comes from harvesting natural stocks. Commercial production could increase supply, expand the season of availability, and reduce pressure on wild populations. Laboratory research has refined many aspects of captive spawning, larval rearing, and the effects of ration and temperature on growth and survival of larvae and juveniles. Here, the effects of stocking density on survival and growth were evaluated during the grow-out phase in pond-based cages.

Figure 1. Growth of pigfish in cages at stocking densities of 100 to 1000 fish per m3. G is average growth rate in mm per week.

Fingerlings were reared to a total length of 54 + 4.3 mm (2.3 + 0.09 g) from captive spawned adults. They were placed into 1-m3 cages constructed of 12-mm nylon mesh at densities of 100, 250, 500, 750, and 1000 fish m-3. Cages were attached to a dock and submerged in a 2-acre pond. Fish were fed a commercial dry diet 3 times per week. Samples of fish were measured weekly for length and wet weight and returned to the cage. Survival was tallied at 7 weeks (end of experiment). The experiment was repeated three times. Salinity, temperature, and dissolved oxygen averaged 16.7 ppt, 27.9°C, and 5.5 mg l-1, respectively.

Mean survival was 88.5% with no significant effect of stocking density (P = 0.24), but mean survival at the highest stocking density (83.1%) was less than it was at all other densities (89.8%). Growth rate was affected by stocking density (P < 0.01), with slower growth at the three highest densities (Fig. 1). Mean grow-out time to market size (100 mm, 9.5 g) from a stocking size of 54 mm was 5.7 weeks at the lowest density and 8.5 weeks at the highest density.

Separately, a half-acre fertilized pond stocked with 1 million eggs produced approximately 8,000, 100-mm pigfish in 16 weeks.

Stocking density had minor effects mortality and growth rate of pigfish in ponds. Results suggest that pigfish can be cultured at high densities and reach market size quickly.