Age Structure and Growth by Otolith Interpretation of Neogobius Melanostomus (Gobiidae) From Southern Black Sea

Abstract

Age and growth of the round goby Neogobius melanostomus (Pallas, 1814) were studied by examination of growth increments within otoliths of 868 specimens caught between October 2002 and March 2005 from offshore of Samsun city in the southern Black Sea. The values of intercept and slope in length-weight relationships were calculated as 0.0110 and 3.07 for males and 0.0076 and 3.23 for females, respectively. Marginal increment analysis showed that the opaque zone was laid down in spring and summer and the translucent zone in autumn and winter. Mean lengths at age data, as derived using otolith readings, were used to estimate growth parameters of the von Bertalanffy equation. The parameters of L∞, k and to were calculated for males as 21.5 cm, 0.375 year -1and -0.83 year and for females as 23.7 cm, 0.223 year-1 and -1.59 year, respectively. There was significant differential growth between sexes. Males attained greater length-at-age values than females. Otolith weight was a better predictor of fish length and age than other otolith dimensions. Age of males and females ranged between 1 and 5 years, while 2 and 3-year old fish were the dominant age classes in both sexes. Age-length keys indicated a great length variability within age groups which was considered as a natural outcome of intermittent spawning in round goby.