Usefulness as marking of deformity in the inter-nostril epidermis of the artificially produced blacktip grouper, Epinephelus fasciatus

Abstract

The frequency of fish with a deformity in the inter-nostril epidermis, the permanency of this abnormality, and its effects on survival and growth of the artificially produced blacktip grouper Epinephelus fasciatus were examined to clarify its potential as an external marking in stocking effectiveness surveys. The possibility of producing a percentage of ca. 90% of deformed inter-nostril epidermis under larviculture was inferred by the use of condensed freshwater Chlorella vulgaris containing n-3 HUFA for supply into larval-rearing water and supplement of nutritional enrichment of rotifer. No significant differences were observed in growth and survival rates of fish with deformed and normal inter-nostril epidermis during two years. The inter-nostril epidermis usually forms completely by a total length of about 12 mm. Fish with incomplete inter-nostril epidermis at this size did not show any subsequent improvement and could still be clearly identified by this deformity even after 2 years. These results represent that this marking method is a potential marking for stocking effectiveness surveys with blacktip grouper