engleski

Environmental conditions conducive to anchovy (Engraulis encrasicolus) spawning in the Adriatic Sea

The goal of the paper is to investigate environmental influences on the occurrence of anchovy spawning over a year, in order to enable the timing and strength of high spawning activity to be predicted. Biological sampling of anchovy was conducted on the fishing ground of the eastern Adriatic (the northernmost semi-enclosed basin in the Mediterranean) on a monthly basis from January 1999 to December 2010, while data on environmental parameters were taken from in situ measurements at the most representative and best surveyed eastern Adriatic hydrographic station and from I-COADS monthly surface climatological fields. Anchovy spawning seasonality was defined by monthly changes of the maturity stages and the gonadosomatic index. Fluctuations of the gonadosomatic index reveal that spawning begins in March and lasts till September, with reproductive activity peaking from April to July. Early or late occurrence of a high gonadosomatic index has a significant negative correlation with upper layer salinity in the two preceding months and a sporadic and weak connection with the wind-mixing index and surface temperature. An enhanced input of nutrient-rich freshwater of river origin, which reduces upper layer salinity and enhances primary production up to two months before anchovy spawning, seems to be important for the anchovy fertility, especially if a late spawning maximum (in July) occurs in a certain year.

reproduction; salinity; temperature; Engraulis encrasicolus; Adriatic

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