Investigations on Age, Growth, and Gonadal Developments of European hake (Merluccius merluccius Linneaus, 1758) in the Sea of Marmara

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Kahraman A. E. (Executive), Karakulak F. S., Yıldız T., Uzer U.

Project Supported by Higher Education Institutions, 2014 - 2017

  • Project Type: Project Supported by Higher Education Institutions
  • Begin Date: July 2014
  • End Date: February 2017

Project Abstract

European hake (Merluccius merluccius Linneaus, 1758), which is a member of Merluccidae, is a species exhibiting wide distribution in the world’s oceans. This study aimed to identify the age and growth parameters, sex ratio, gonadosomatic index (GSI) values, spawning season, and developmental stages of oocytes of M. merluccius in the Sea of Marmara, an area where little information on this species is available. In this study, a total of 777 specimens (341 females, 192 males, and 244 undetermined) were caught during the fishing season between October 2014 and September 2015 from the Sea of Marmara. Total lengths of all sampled individuals were between 10.4 cm and 55.3 cm. Among the total 533 individuals whose sexes were identified, the lengths of female individuals were between 13.4 cm and 55.3 cm, and that of male individuals were between 15.6 cm and 40.5 cm. Sagittal otoliths of 767 individuals were extracted for use in age and growth analyses, and age determination was conducted by using otolith readings. Age of the fish ranged from 1 and 6 years and mean fork length values for each age group were separately calculated for both sexes. Growth parameters calculated according to Von Bertalanffy growth equation were estimated for females: L∞ = 106.36 cm, k = 0.082, t0 = –1,097; for males: L∞ = 102.43 cm, k = 0.091, t0 = –0.829; and for all samples: L∞ = 103.97 cm, k = 0.087, t0 = –0.926. According to age–structured analysis, the total, natural, and fishing mortality rates were calculated as 2.01, 0.19, and 1.81, respectively. The exploitation rate, E = 0.90, indicated a high fishing pressure on the European hake stock in the Sea of Marmara. Furthermore, the length-weight relationship for all individuals was calculated as W = 0.9656 L2.989. Sex ratio was found as 0.56 (M/F). Based on the GSI values calculated for female individuals, it is understood that ovulation activities occur especially in November, December, and June. On account of the histologic analyses on 341 female gonads, it was determined that a total of 51 females which were sexually mature (in c and d oocyte stage) were sampled in November, December, and June, when the spawning activities reached maximum levels.