Morphometric changes in the cultured starry flounder, Platichthys stellatus, in open marine ranching areas

Hatchery seeds released into open coasts for wildstock enhancement are often a biological pollutant and affect the recipient ecosystem integrity. We studied morphological changes in two hatchery populations of the starry flounder Platichthys stellatus; one released into the open coast from the hatchery (released population) and the other kept in the hatchery (captive population). The released population differed significantly from the captive population 3-36 months after release from the hatchery. Two-way ANOVA comparison revealed that 11 of 15 starry flounders differed significantly in morphological measurements, 10 of 15 differed in pigmentation, and 5 of 15 differed in morphometric ratios between the two populations. Pigmentation on the blind side (a representative sign of captive flounders) also differed between the two populations with an occurrence rate of 22.7% for the former and 39.5% for the latter groups. The released population was more similar to wild populations than to captive populations in terms of morphology; namely, longer and broader heads, a narrower body shape, longer fins, and a shorter and narrower peduncle.