Distribution and population structure of the Chlorophthalmus agassizi (Bonaparte, 1840) on an unexploited fishing ground in the Greek Ionian Sea

Abstract

Summary The distribution and population structure of the shortnose green eye, Chlorophthalmus agassizi, were studied in the Greek Ionian Sea using data collected during experimental trawl surveys carried out from December 1996 to November 1997. The length–frequency distribution ranged between 45 and 201 mm total length (TL). The significant increase in average size linked with depth has been observed, supporting the general bigger-deeper phenomenon. Specifically, 1528 individuals were measured in the 300–400 m depth zone with a mean TL ¼ 101 mm, 2351 individuals in the 400–500 m depth zone with a mean TL ¼ 132 mm and 1889 individuals in the 500–600 depth zone with a mean TL ¼ 145 mm. Age and growth of the population were determined by otolith readings. Twelve age groups were identified. The von Bertalanffy growth function (VBGF) parameters were L¥ ¼ 202.22 mm, K ¼ 0.20 and to ¼ )1.6 years. Natural mortality was estimated at 0.285 per year, while total mortality was estimated at 0.65. The reproductive period of C. agassizi extends from spring to autumn, with greater activity in the summer.