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Modeling the impact of climate variability on Black Sea anchovy recruitment and production

Güraslan, Ceren
Fach Salihoğlu, Bettina Andrea
Oğuz, Temel
The connection of climate variability with anchovy spawning and recruitment in the Black Sea in particular, and other ecosystems in general, was studied using a two-way coupled lower trophic level and anchovy bioenergetics model. Climate variability was represented by a 50-yr time series of daily temperature and vertical mixing rates with stochastic variations. Temperature was found to be the dominant factor influencing early life stages and hence population dynamics of Black Sea anchovy as marked by a high correlation of anchovy egg production and recruitment success in response to changes in temperature. Each decrease of 2 degrees C in summer mean temperatures resulted in a delay in the timing of egg production of between 12 and 19 days. Water temperatures in the spawning season had a greater influence than the number of available spawning females on the intensity of egg production. Anchovy recruitment was similarly influenced by temperature, with decreased temperatures resulting in a significant delay in the onset of peak recruitment during the fall by 21-38 days. Also, recruitment numbers in December decreased by about 20% with decreasing temperatures. The impact of temperature on production was slightly diminished by the impact of vertical mixing. The strong linkage of climate variability with anchovy spawning and recruitment has an important prediction potential for short-term anchovy stock estimations, which may serve fisheries management purposes.