OPTIMIZING REARING CONDITIONS FOR LARVAL PIGFISH, Orthopristis chrysoptera

Cynthia K. Faulk*, Kathryn L. Thompson, and Lee A. Fuiman
 
Fisheries and Mariculture Laboratory
University of Texas Marine Science Institute
Port Aransas, Texas 78373  
cfaulk@utexas.edu

Pigfish are a popular marine baitfish in the southeastern United States, and commercial production could increase availability and reduce pressure on wild populations. Research on optimal rearing conditions for pigfish is needed for production to be feasible. We investigated the effects of temperature and weaning protocols on larval pigfish growth and survival.

First, larvae were reared on live feed to 20 days post-hatch (dph) at 5 temperatures from 22-30 °C (Table 1a). Larval growth was slowest at 22 °C and final size was significantly smaller compared to higher temperatures. In contrast, survival was highest at 22 °C, decreasing with increasing temperature.

We quantified the ontogeny of digestive enzyme activity in larvae, and the results suggested that larvae could be weaned at approximately 11 mm SL, or 30 dph when reared at 24 °C. To test this estimate, we conducted a weaning study at 24 °C where larvae were co-fed live prey and a dry microdiet (MD) beginning 15 dph (~5 mm SL). Live prey was eliminated from the diet at 24, 28, 32, or 36 dph corresponding to approximate SLs of 7, 10, 12, and 15 mm. Controls were co-fed with live prey and MD throughout. On 43 dph, larval size was not significantly different across treatments, but survival was lower when the fish were weaned at 24 dph (Table 1b).

In order to maximize both growth and survival, we suggest a rearing temperature of 24 °C. At this temperature, larvae were efficiently weaned to a MD at 28 dph, corresponding to 10 mm SL. Producers rearing larvae at lower or higher temperatures to match production goals, could schedule weaning once larvae reach this size.