Virtual population analysis of the big eye Priacanthus macracanthus in the waters off northeastern Taiwan

Abstract

A length–frequency data set including 9548 specimens of the big eye, Priacanthus macracanthus, from the waters off northeastern Taiwan during the period from 1994 to 1997 was analyzed. Six age classes were identified from a length–frequency analysis and dominant age classes were 3+, and 4+. Instantaneous total mortality (Z) was estimated to be 0.88, 1.36, 1.97 and 1.56/yr for 1994–1997, respectively. Natural mortality (M) estimated from Pauly's equation ranged from 0.326 to 0.373/yr. Age-specific abundance estimated from virtual population analysis indicated that the abundance of 2+ peaked in 1995, 3+ in 1996, 4+ in 1997, and 5+ and 6+ in 1994. The abundance of the 1989–1994 year–class indicated that the big eye stock experienced the highest mortality during the period of ages 4 and 5. Abundance of the big eye stock (for 2+ to 6+) increased from 1994 to 1995 and decreased thereafter. Similar patterns of abundance, catch and catch per unit of effort suggested that the big eye stock might fluctuate periodically.