Forming and Realization of Fecundity in the Black Sea Turbot Scophthalmus maeoticus (Scophthalmidae) at the South-Wester
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ing and Realization of Fecundity in the Black Sea Turbot Scophthalmus maeoticus (Scophthalmidae) at the South-Western Shelf of the Crimean Peninsula V. E. Giragosov* Kovalevsky Institute of Biology of the Southern Seas, Russian Academy of Sciences, Sevastopol, Russia *e-mail: [email protected] Received July 23, 2019; revised August 26, 2019; accepted October 8, 2019
Abstract—The reproductive characteristics of the females of the Black Sea turbot Scophthalmus maeoticus were studied on the materials collected in 2007–2018 at the south-western shelf of the Crimean Peninsula. The spawning of the Black Sea turbot in this area lasts for two months on average, from the second decade of April to the end of the first decade of June; the most intensive spawning is observed during the first and the second decades of May. The average number of vitellogenic oocytes is 4368 thousands per female (average somatic body weight of 2.96 kg); these oocytes form potential fecundity before the spawning starts. On average, 73% of potential fecundity (3189 thousand oocytes) is realized during the spawning period. The vitellogenic oocytes remaining in the ovaries undergo resorption for 2–3 months after spawning. Batch fecundity averages 412 thousand oocytes (12.9% of realized fecundity); according to our estimates, each female spawns seven to eight times on average during the spawning season. Keywords: Black Sea turbot Scophthalmus maeoticus, fecundity, oogenesis, Crimean Peninsula shelf, Black Sea DOI: 10.1134/S0032945220040050
INTRODUCTION The Black Sea turbot Scophthalmus maeoticus is a valuable commercial fish species and a prospective object of marine aquaculture. Females of the Black Sea turbot mature at the 6–8th year of life (Popova, 1967), single specimens, even earlier, at the age of 3+ (Oven, 2004) or 4+ (Popova, 1954; Giragosov et al., 2008). According to the most recent data (Nadolinskii et al., 2018), female maturation en masse (58%) occurs at the age of 4 years. Differences in the estimates of this characteristic may be related to the complexity of determining the age of the Black Sea turbot, since the interpretation of the growth zones of its otoliths is quite subjective. According to the results of probit analysis, the standard length (SL) at which 50% of females mature is 39.8 (37.5–41.2) cm (Pyatinskii, 2017). The Black Sea turbot spawns along all the shores of the Black Sea; spawning periods depend on the area and hydrological conditions of a particular year. In general, this species spawns from late March to the second half of June, sometimes until the end of July, most intensively in May (Popova, 1954). The Black Sea turbot is characterized by discontinuous oogenesis, batch spawning, and determinate fecundity (Oven, 2004). The potential fecundity of the Black Sea turbot is very high, ranging from 3 to 13–
14 million eggs, depending on the female body size (Krotov, 1941; Popova, 1972; Talikina and Vorob’eva, 1975). However, the survival rate of pelagic eggs in the sea is low, from 2–3 up to 10–20% (Popova, 197
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