A Multivariate Assessment of Factors Influencing Survival of Red Drum in Earthen Outdoor Rearing Ponds

Abstract

Abstract.Extensive culture of larval Red Drum Sciaenops ocellatus in outdoor ponds occasionally results in low survival, thereby stifling stock enhancement goals. Mortality is probably tied to multiple environmental influences rather than to any singular factor. We assessed factors influencing Red Drum mortality and survival in the context of an extensive aquaculture operation in Texas. Larvae were stocked into 120 rearing ponds of various sizes in the spring, summer, and fall of 2012 and 2013. Water quality variables (temperature, salinity, dissolved oxygen, and pH) were assessed throughout culture. A principal components analysis of water quality, pond size, stocking density, and zooplankton density (number of organisms/L) was used to determine how each variable related to survival (measured as a ratio of the total number of Red Drum harvested to the total number of Red Drum stocked). Temperature, salinity, dissolved oxygen, and pH all loaded significantly onto the first ordination axis, suggesting correlations among water quality variables. Survival loaded significantly on the second and third ordination axes and was positively associated with larger ponds, lower stocking density, higher zooplankton density, and lower pH. Stepwise regression of observed variables in ponds pooled by year suggested that pH and stocking density were important in both 2012 (r2 = 0.452) and 2013 (r2 = 0.305, P < 0.05). These data indicate that ponds with moderate densities of Red Drum larvae will have a higher probability of survival than ponds with high larval densities; the results also confirm previous findings that pH is a significant mortality factor in extensive aquaculture of Red Drum.