Age and growth of four-spotted megrim (Lepidorhombus boscii Risso, 1810) from Saros Bay (Northern Aegean Sea, Turkey)

In this study, the growth parameters of the four-spotted megrim, (Lepidorhombus boscii Risso, 1810), were studied in Saros Bay, which had been closed to bottom trawl fishery since 2000. The sex ratio of females to males was 1:0.42. Length-weight relationships were W=0.0032L3.31 and W=0.0069L3.04 for females and males, respectively. Growth parameters of the populations were L∞=49.8 cm, k=0.09 year-1, t0=-2.15 year for females; L∞=39.1 cm, k=0.11 year-1, t0=-2.59 year for males. The growth performance index (Φ’) was found to be 2.35 and 2.23 for females and males, respectively

Effect of twine thickness on selectivity of gillnets for bogue, Boops boops,in Turkish waters

To investigate the effect of twine thickness on the selectivity of multifilament gillnet targeting bogue,Boops boops L., four different stations were sampled between March and November 2008 in the northern Aegean Sea. Gillnets with 22, 23, and 25 mm nominal mesh size (bar length) each having two different twine thicknesses (approximately 0.45 mm and 0.54 mm ∅) were applied for this purpose. The deviances from the SELECT method revealed that lognormal models provided the best fits for both of the twine thicknesses. Results from the two-way ANOVA analyses revealed that the mean total lengths increased with the mesh size (F = 87.36; df = 2; P < 0.0001) and decreased with the twine thickness (F = 46.12; df = 1; P < 0.0001). The 22 mm mesh size net (0.45 mm ∅) captured significantly larger fish than the 23 mm mesh size net (0.54 mm ∅) probably due to the higher elasticity and flexibility of the thinner twine. Thus, fisheries managers should take into consideration the twine thickness while advising mesh size regulations in gillnet fisheries

Reproductive biology of the spotted flounder, Citharus linguatula (Actinopterygii: Pleuronectiformes: Citharidae), from Saros Bay (northern Aegean Sea, Turkey)

Background. Understanding the reproduction of the spotted flounder, Citharus linguatula (Linnaeus, 1758), has been considered a major step toward understanding its population dynamics, especially, in the northern Aegean Sea. So, the presently reported study aimed to study the reproductive biology of C. linguatula and provided the first data of its fecundity. Materials and methods. This study was carried out between September 2006 and September 2008 in Saros Bay (Northern Aegean Sea, Turkey), which had been closed to trawl fishing since 2000. The gonadosomatic index, length at maturity (L50), and absolute fecundity were analysed. Results. The elevated GSI values observed, suggested the spawning period was from September to November. The length at maturity (L50) was at 15.0 cm TL for females and 14.0 TL cm for males. The relations between the absolute fecundity and total length, total weight, and age of the spotted flounder females were estimated as Fa = 0.1878TL3.29, Fa = 58.515TW + 36.453, and Fa = 887.59A – 389.43, respectively. Conclusion. The identification of reproductive strategy is necessary to obtain a better understanding of its biology

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

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