Age, growth, and reproductive biology of turbot, Scophthalmus maximus (Actinopterygii: Pleuronectiformes: Scophthalmidae), from the south-western coasts of Black Sea, Turkey

Abstract

Background. The turbot, Scophthalmus maximus (Linnaeus, 1758), is of high economical value in Turkey and its biological characteristics have hitherto not been studied in the South-western Black Sea. The purpose of this study was to determine the age and growth, length–weight relation, condition factor, sex ratio, age and length at first maturity, and reproduction period of the turbot in the south-western Black Sea coast of Turkey. Materials and methods. Turbots were collected monthly in the south-western Black Sea coast of Turkey using bottom trawl and turbot gillnets. The fish samples were obtained between October 2004 and September 2005. Results. A total of 264 turbots were sampled and the age groups ranged from I to X (no individuals found at age group IX). Total lengths were between 14.0 and 70.0 cm, while weights varied from 34 to 5550 g. The length–weight relation for combined sexes was determined as W = 0.0085L3.1581. The von Bertalanffy growth equation parameters were: L¥ = 73.55 cm, k = 0.17 year–1, t0 = –0.12 year. The observed sex ratio (female : male) was 1 : 0.35. The length at first maturity (L50) of the species was 20.38 cm for females and 24.68 cm for males (both at two years old). Monthly gonadosomatic index (GSI) values suggest the spawning activity extends from 15 April to late June. Conclusion. The legal fishing season of the turbot, imposed in 2012, begins on 15 June. We recommend that this date should be postponed to 30 of June due to turbot’s reproduction extending to late June.

Keywords

• turbot
• age and growth
• reproduction period
• Black