Impact of environmental deviations on the larval and year-class abundances in the spring spawning herring Clupea harengus membras L of the Gulf of Riga Baltic Sea in 1947-2004
Ojaveer, E.; Arula, T.; Lankov, A.; Shpilev, H.
Fisheries Research (Amsterdam) 107.1-3: 159-168
2011
ISSN/ISBN: 0165-7836 DOI: 10.1016/j.fishres.2010.11.001
Accession: 037432267
Regular weekly sampling of larvae with a Hensen net in the stationary stations on the main spawning grounds of the brackishwater herring population in the Gulf of Riga was carried out in 1947-2004. Probably due to the rapidly increasing anthropogenic eutrophication and the rising winter temperature the yearly abundance of herring larvae has significantly increased with a shift in the average abundance in 1972/1973. Correlation of the average number of herring larvae with the year-class strength was significant for the intermediate (10-16 mm, P =17 mm, P 0.05). In the period of milder winters the importance of the SSB in determination of the abundance of year classes considerably increased and it significantly correlated with the abundance of year classes (P< 0.05). The winter-spring temperatures and other climatic variables presumably control the abundance of the forming year-class during the period of the highest larval mortality mainly via the production of their food.