Effects of egg stocking density on egg hatchability, larval quality and water quality for pinfish, Lagodon rhomboides , and pigfish, Orthopristis chrysoptera

Abstract

Pinfish (Lagodon rhomboides Linnaeus) and pigfish (Orthopristis chrysoptera L.) are relatively new, cultured species commonly used as marine baitfish in the south-eastern United States and currently have no defined protocols for egg incubation. Thus, experiments were conducted to determine efficient egg stocking densities during static and flow-through incubation that yielded higher quality larvae. Eggs of each species were incubated statically at 250, 500, 1000 and 2000 eggs L−1, and after incubation, egg hatching success, larval survival to first feeding, larval morphometrics and water quality were assessed. Stocking densities above 250 eggs L−1 led to significant reductions in pinfish hatching success and water quality degradation, evident from decreased dissolved oxygen and pH levels and increased nitrogenous wastes. Increased stocking densities for pigfish also resulted in significant water quality degradation, although hatching success was unaffected up to a density of 1000 eggs L−1. A high flow-through water exchange rate of 2000% daily resulted in significant reductions in nitrogenous wastes and greater stability in dissolved oxygen and pH levels during incubation when compared to static treatments of the same egg density. Additionally, the high exchange rate of 2000% was critical in maintaining high hatching success and larval survival to first feeding at stocking densities of 1000 eggs L−1 for pinfish and up to 4000 eggs L−1 for pigfish. No clear patterns in larval morphometrics were observed among stocking densities. Static incubation densities of 250 and 1000 eggs L−1 are recommended for pinfish and pigfish, respectively.