Zoological Studies

Hatching Period and Early-Stage Growth Rate of the Gold Estuarine Anchovy Stolephorus insularis in Taiwan as Inferred from Otolith Daily Growth Increments

Wann-Nian Tzeng, Han Chu, Kang-Ning Shen, and Yu-Tzu Wang (2008) To understand the reproductive strategies and recruitment dynamics of the gold estuarine anchovy Stolephorus insularis in a subtropical area, their seasonal abundance was investigated, and their hatching period and growth rate were estimated from otolith daily growth increments.  Specimens were collected from the Tatu River estuary on the west-central coast of Taiwan during 1997-1998.  Juvenile fish dominated the catch composition, suggesting that the estuary is a nursery for newly recruited juveniles of S. insularis.  The distribution of hatching dates for anchovy in subtropical Taiwan was similar to that of temperate zone fish, with a major spawning season in spring and a minor spawning season in autumn.  This spawning strategy coincided with a new production cycle that was higher in spring than in autumn.  Mean standard lengths and ages of the anchovy at recruitment were significantly larger for the autumn than for the spring and summer cohorts (all p < 0.001), while the somatic and otolith growth rates were higher in spring than in summer and autumn (all p < 0.001).  Larval anchovy grew faster and reached their maximum growth rate (inflexion point of the growth curve) earlier during summer than during either spring or autumn.  The growth rate after the inflexion point was lower in autumn than in either spring or summer.  The reproductive and growth rate variability indicated that the spring cohort is the major component of the stock and that the autumn cohort is a minor supplement to overall recruitment.