European anchovy is most abundant in the Azov and Black Sea Basin ichthyocenosis and plays leading role in the marine fisheries. There are two subspecies of the European anchovy in the Black Sea: the Black Sea anchovy Engraulis encrasicolus ponticus Aleksandrov and the Azov anchovy Engraulis encrasicolus maeoticus Pusanov. Wintering areas of both subspecies (stocks) are located in the Black Sea. Basing on the more than 30-years research of anchovy, this chapter summarizes data on catches, catch per unit effort, population parameters, spatial distribution patterns, abundance, and scientific survey results separately for two stocks. Direct methods of stock assessment, based on trawl, lampara and hydroacoustic surveys data, have been applied. Authors recommend to the Black Sea countries authorities to build their anchovy fishery-regulating decisions mainly on the hydroacoustic surveys' results. A major impact of invasive Atlantic ctenophores Mnemiopsis leidyi and Beroe ovata on anchovy populations is revealed.
TopBackground
All authors, who have been researching this species in the Azov and Black Sea basin, acknowledge the existence of two subspecies: the Azov anchovy (Engraulis encrasicolus maeoticus Pusanov) and the Black Sea anchovy (E. e. ponticus Alexandrov) (Aleksandrov, 1927; Mayorova, 1934; Pusanov, 1936). These subspecies are typical geographic populations (races), spawning areas of which are limited to different reservoirs. The Azov anchovy breeds in summer in the Sea of Azov, and the Black sea anchovy breeds in the Black Sea at the same time.
For the anchovy cannot exist at the water temperature below 6°C for a long time, its schools migrate from the northern part of the sea southward as winter cold sets in (Mayorova, 1951; Kornilova, 1960; Danilevsky, 1964). In such event the Azov anchovy goes to the Black sea through the Kerch strait. The population structure of the anchovy in Black Sea and the Sea of Azov and the relationships between its subspecies have been studied rather well to date (Altukhov, 1974; Kalnina&Kalnin, 1984; Chashchin, 1996). The anchovy race (subspecies) identification was carried out in the previous studies, with the use of morphological characters (otolith shape, body length, head and body proportions) (Skazkina, 1965; Gubanov& Limansky, 1968; Shevchenko, 1980; Chashchin 1985), as well as genetic methods. Last ones included the identification of blood groups by means of erythrocytes heteroagglutination reactions with pig and horse serums; as well as isocytratedehydrogenase and esterase isoenzymes allele frequencies detecting (Altukhov, 1974; Kalnin et al, 1984, 1985). Divergence by muscle proteins was found out as well (Ivanova&Dobrovolov, 2006).
Furthermore, these anchovy subspecies differ by the parasitic nematodes infestation rate. In anchovy, which feeds in the Black Sea in summer, the body cavity infestation rate with the Conracaecum aduncum nematodes is higher (Terekhov, 1979; Chashchin, 1981).