Lipid distribution patterns of nine commercial fish in Thailand

Lipid distribution pattern is an important trait, which is related to flesh quality and the yield rate of aquaculture products. Here we investigated lipid distribution patterns by oil red O staining for nine economically important fish in Thailand. The most remarkable feature was that Siluriformes species had a thick layer of subcutaneous lipids, possibly to compensate the evolutionary loss of scales. In addition, we found several other characteristic staining patterns: (1) dotted stains at the boundary of red and white muscles and along the subcutaneous tissue in crystal-eyed catfish, (2) double lines of staining along the subcutaneous layer in crystal-eyed catfish, (3) dotted stains along the horizontal septum lines in hybrid catfish, (4) pronounced retroperitoneal fat accumulation in Nile tilapia and red tilapia, (5) pronounced fat accumulation in the inclinator muscle of the fins in Indian spiny turbot, (6) intense staining under the scales of common carp and (7) three dotted stains in soft finrays in clown knifefish. Although lipid distribution patterns are known to be affected by environmental conditions, the observed species differences suggest the strong genetic control of lipid distribution. This trait should be considered as a target of selective breeding especially for Siluriformes, in addition to commonly used parameters such as growth rate and disease resistance.