Bathymetric distribution, seasonal growth and mortality of the deep-water rose shrimp parapenaeus longirostris (Decapoda: Penaeidae) in an unexploited stock in Saros Bay, Aegean Sea

Abstract

To describe the growth, mortality and distribution pattern of the deep-water rose shrimp, Parapenaeus longirostris in an unexploited resource, 301 trawl surveys were conducted between 20 and 465 m water depths from February 2005 to September 2008 in Saros Bay, Aegean Sea. Bathymetrical biomass distribution of the deep-water rose shrimp shown a clear tendency towards the deeper waters with highest biomass estimations exceeding 50 kg h-1 obtained in water depths between 201 and 300 m. Von Bertalanffy Growth (VBG) parameters were estimated from monthly Carapace Length (CL) frequency distribution data using three different methods: ELEFAN, PROJMAT and SLCA. For the data of this study, the seasonal VBG parameters obtained from ELEFAN was considered to best describe the growth pattern and were estimated as L° = 34.7 mm, K = 1.05 year-1, to = -0.95 year, WP = 0.87 (i.e., November) and C = 0.47 for females and as L° = 27.0 mm, K = 1.49 year-1, to = -0.88 year, WP = 0.35 (i.e., May), C = 0.53 for males. Growth performance index (?') was higher in females (?'1 = 3.10) than males (?' = 3.03). Instantaneous annual mortality rates (Z), assumed to represent annual natural Mortality rate (M), ranged between 1.19 and 4.73 year-1 for females and between 0.88 and 3.51 year-1 for males, depending on the method used for the estimation. The mortality rates estimated with the Seasonal Length Converted Catch Curve (SLCCC) method was the most appropriate one for the Saros Bay stock and was estimated as 1.72 year-1 for females and as 1.82 year-1 for males. © Medwell Journals, 2009.