Age, growth and reproduction of the Asian sheephead wrasse Semicossyphus reticulatus in the western Seto Inland Sea, Japan

The Asian sheephead wrasse, Semicossyphus reticulatus , is the largest labrid in temperate waters around Japan. However, the growth pattern of this wrasse remains unclear. Age, growth, and reproduction of S. reticulatus specimens were investigated by sampling in the western Seto Inland Sea, Japan. Opaque ring marks formed on the marginal zone of sectioned otoliths during February–March, suggesting their validity for age estimates. The largest individual was a male, with a standard length (SL) of 591 mm, weight of 8.5 kg, and age of 17 years. Males had significantly larger SLs and older ages than females, and male gonads were histologically confirmed to have secondary testis structures retaining central lumens, suggesting monandric protogyny. The oldest S. reticulatus individual captured was estimated to be a 31-year-old male. The von Bertalanffy growth equation calculated from estimated age and SL was L t = 489 (1 − e −0.12 ( t + 1.75) ), indicating considerably slow growth, particularly after the age of 10 years, which is similar to that of the California sheephead wrasse, Semicossyphus pulcher . The humpheads of S. reticulatus enlarged gradually as their body grew, often resulting in a conspicuous humphead, even in large females.