Reproduction and Seasonal Growth Estimates of the Black Goby, Gobius niger (Osteichthyes: Perciformes: Gobiidae) in the Southeastern Black Sea Region of Turkey

Abstract

Seasonal growth pattern and reproductive biology of the black goby, Gobius niger (n= 568; 2.1-14.6 cm TL), were monthly studied in southern Black Sea between December 2012 and November 2013. The seasonal von Bertalanffy growth parameters, computed from ELEFAN, were estimated as L∞= 11.9 cm TL, K= 0.701 year -1 , C= 0.633, and WP= 0.492 for the Hoenig seasonal model and as L∞= 12.1 cm TL, K= 0.680 year -1 for non-seasonal von Bertalanffy model. The size at sexual maturity (Lm) was estimated as 8.9 cm TL. The Gonadosomatic index (GSI) ranged between 0.60 in December and 8.57 in April 2013 (mean 3.82±0.82) for females and 0.61 in October 2013 and 2.90 in May 2013 (mean 1.70±0.26) for males. The seasonal growth was pronounced probably due to reproduction activity which extended investment of energy in reproduction causing slower growth. The GSI development was related to photoperiod and the monthly variations of GSI values indicating that the intensive spawning occurred between April 2013 and August 2013. During spawning time, the mean GSI value of females (6.04±1.18) was 2.9 times higher than the mean GSI values of males (2.08±0.42) (P< 0.05). The results of this study were offered as biological input parameters regarded as a reference for the conservation and management of the Black Sea stocks of the black goby.

Population Dynamics, Current Trends and Future Prospects of the Black Goby (Gobius niger) in the Eastern Part of the Black Sea (Turkiye)

“…The average TL of females was significantly lower, due to the predominance of males in the higher length classes (Figure 2). In contrast, different populations have been described where there is no difference in TL between males and females of black goby (Kasapoğlu, 2016;Kırdar & İşmen, 2018;Bilgin & Onay, 2020). The L max of the black goby in the study area is close to that in previous studies in the Black Sea (Table 4).…”

“…The sex ratio may differ from the theoretical ratio of 1:1 by size class and gender in the same population, being influenced by reproductive behavior, the adaptation of the population, environmental conditions, and food availability (Clarke, 1983). In other studies of Gobius niger in the Black Sea, females were found to predominate males (Kasapoğlu, 2016;Bilgin & Onay, 2020;Van & Gümüş, 2021). However, in this study we report more males.…”

“…In this study, however, males were dominant during the reproduction period, and in other periods, sex ratios were almost equal (Table 1). Researchers in previous studies (Kasapoğlu, 2016;Bilgin & Onay, 2020;Van & Gümüş, 2021) used bottom trawls for sampling and this indicates non-selective sampling and a sampling site away from the shore. In this study, gill nets were used and sampling was made in a narrow depth range.…”

“…The LWR results in the Turkish coasts of the Black Sea show that the calculated b values were changed between 2.86 (Kasapoğlu, 2016) and 3.54 (Bilgin & Onay, 2020). LWR parameters may differ significantly due to environmental or biological factors, and temporal, geographical, and sampling factors (Bagenal & Tesch, 1978;Froese, 2006).…”

“…The status of black goby populations in the Black Sea was examined by different researchers between 2008 and 2013. Unlike this study, Kasapoğlu (2016) studied a lower number of samples, a study carried out by Bilgin & Onay (2020) included only the province of Rize, and the age determination was made according to the computer-based length frequency distribution analysis. Van & Gümüş (2021) studied in the same region as the current study and examined more samples, but more than ten years have passed since their study.…”