WP 3: Case study – Black Sea anchovy

Lead: Central Fisheries Research Institute, Turkey

Anchovy (Engraulis encrasicolus) is the key fish species in the Black Sea food web and has high ecological and economic importance for the Black Sea fisheries. Moreover, anchovy is an important predator of zooplankton (especially copepods) and is a main food resource for top predators (dolphins, spiny dogfish, mackerel, whiting, turbot, skates etc.).

Its migration pattern covers the whole Black Sea. In October-November migration starts to the wintering grounds along the Anatolian and Caucasian coasts in the southern Black Sea. In November-March it forms dense wintering schools that are subject to intensive commercial fishing. During the rest of the year, the species occupies spawning and feeding habitats across the Black Sea with some preference for shelf areas mainly in the northwestern part of the Black Sea where the largest and most productive shelf areas are located. However, according to the studies carried out in the southern Black Sea anchovy also spawns there. This may be a result from climatic changes and other ecological impacts occurring in the last three decades.

Anchovy mature at age 1, spawns during summer, which is also the main feeding and growth season. Anchovy spawn mainly in the surface layer and eggs and larvae are retained in the coastal layer stabilized in depth by the thermocline and protected from the offshore by thermo-haline fronts.

Anchovy is mostly exploited by the commercial purse-seine fishery, and Turkey is responsible for > 97% of the total Black sea catch. Anchovy is also captured in artisanal fisheries with coastal trap nets and beach seines mainly in Bulgaria, Romania and Ukraine. The catch of the Black Sea countries increased until 1984 up to 566,000 tonnes, remained at a high level until 1988 (526,000 tonnes) and then abruptly dropped to 86,000 tonnes in 1988. Overfishing and accidental introduction of the ctenophore (Mnemiopsis leidyi, which preys on anchovy larvae and competes with anchovy adults) are believed primarily responsible for the collapse. From 1995 to 2010 the catch ranged with wide oscillations from year to year in the range 135,000-400,000 tonnes. In 2012, total Black Sea catch was 193181 tonnes.

Such rapid fluctuations in catch could be attributed to several factors, including changes in the species targetted by the Turkish purse seiners, an increase of predators, invasive species, and climate effects. The collapse of small and medium-sized pelagic fish stocks happened at the same time and in all regions of the Black Sea, and suggests that factors such as eutrophication, climatic effects, Mnemiopsis population explosion as well as overfishing drive population dynamics. As zooplanktivores, anchovy have similar prey preferences as other organisms at the same trophic level such as sprat, shad, pilchard and comb jellyfish and therefore compete for the same food resource.

In this workpackage recruitment and migration of anchovy will be analysed in relation to variations in zooplankton abundance. Some new samples of anchovy and zooplankton will be obtained to maintain long time series and to provide data for skill assessment of lower trophic level oceanographic models.

 

 

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19 DECEMBER 2018