Reproductive biology and population structure of anchovy (engraulis encrasicolus linnaeus, 1758) in the black sea

In this doctoral dissertation, the reproductive biology and population structure of the European anchovy (Engraulis encrasicolus, Linnaeus, 1758), a species widely distributed throughout the Black Sea and of high economic importance to Turkish fisheries, were comprehensively investigated over a two-year period (2020–2022). Anchovy specimens were collected monthly from various regions of the Black Sea. Gonadal histology, sexual maturity stages, length at first sexual maturity (L₅₀), gonadosomatic index (GSI), hepatosomatic index (HSI), condition factor, fecundity parameters, spawning times, oocyte diameter, mortality rates, length composition, sex ratio, and age-growth parameters were analyzed separately for each year. The mean total length and weight were found to be 9,33±1,746 cm and 5,54±3,054 g in the first year, and 10,58±1,33 cm and 7,66±2,649 g in the second year, respectively. The female-to-male ratio was calculated as 1:1,02 in the first year and 1:1,06 in the second year, indicating a slight dominance of females in both years. The length-weight relationships were estimated as W = 0,0038 L³,²¹³⁵ (r² = 0,9287) for 2020–2021 and W = 0,0102 L²,⁷⁸⁶⁹ (r² = 0,9146) for 2021–2022. Growth parameters were estimated using the von Bertalanffy growth model, with L∞ = 14,67 cm, k = 0,551 year⁻¹, t₀ =-1,850 (2020–2021) and L∞ = 14,25 cm, k = 0,499 year⁻¹, t₀ =-2,126 (2021–2022). Based on mortality rates, the calculated exploitation rates for each year (E = 0,73 and E = 0,69) show that fishing pressure is high. Histological findings confirmed that E. encrasicolus exhibits asynchronous spawning, with the spawning season occurring between May and August in the first year and June and September in the second year. GSI and HSI values supported the histological assessments regarding the timing of reproduction. The length at first sexual maturity (L₅₀) for females was calculated as 9,82 cm and 9,81 cm for the first and second year, respectively. This study provides detailed insights into the reproductive and stock characteristics of European anchovy, offering valuable data for the sustainable management of Black Sea fisheries. It stands out as one of the most comprehensive regional investigations conducted on this species to date.