Quality considerations and malformation surveillance in a marine stocking program

Abstract

Marine enhancement programs can be helpful for the conservation of important species. Many variables are considered in managing a marine enhancement program, and external fish quality prior to release should be one of them. Quality assessment aids in understanding the influence of rearing variables, limits a recognizable cultured fish phenotype, and maximizes the success of the conservation program by emulating the survivorship potential of wild stocks. We rear white seabass, Atractoscion nobilis, for stock enhancement and developed a semiquantitative assessment and control program to document and reduce the incidence of abnormal physical attributes prior to their release. Clearing and staining techniques were used to define normal processes of ossification, and wild fish surveys were performed to understand variability in natural stock morphology. In the hatchery, A. nobilis were examined in lots of 125 fish cohort –1 at 50 and 80 d post hatch of their development. Specimens evaluated were normal or classified as having malformations involving the bone or cartilage (13 categories) ranked 1–3, mild to severe. Malformations that were unique or differed substantially from wild A. nobilis specimens were culled from the cultured cohort as part of a quality control process prior to release. The most common malformations involved the head region, which accounted for 98% of all hard tissue malformations. Malformations of the jaws accounted for 30% of observed malformations and lower jaw prognathism was the most common observation. This program has proven useful for identifying malformations and minimizing the release of affected cultured marine fish.