Title: Recruitment Dynamics of the Gulf of Riga Herring Stock: Density-Dependent and Environmental Effects
Authors: RAID TiitKORNILOVS GeorgsLANKOV A.NISUMAA A.-M.SHPILEV H.JAERVIK A.
Citation: ICES JOURNAL OF MARINE SCIENCE vol. 67 no. 9 p. 1914-1920
Publisher: OXFORD UNIV PRESS
Publication Year: 2010
JRC N°: JRC55702
ISSN: 1054-3139
URI: http://icesjms.oxfordjournals.org/content/67/9/1914.full.pdf+html?sid=beaa9f96-9475-4f1f-8478-6c66774dd8cc
http://publications.jrc.ec.europa.eu/repository/handle/JRC55702
Type: Articles in Journals
Abstract: The Gulf of Riga and open-sea stocks of the Baltic herring have displayed remarkably consistent inverse recruitment and stock development patterns since the 1970s: the open-sea stocks steadily declined, whereas the Gulf stock increased rapidly in the early 1990s, reaching a peak abundance in the early 2000s and exceeding the level of the 1970s by a factor of 2¿3. The increase was accompanied by a decline in the mean weight-at-age and the condition factor. The estimated decline (by 30¿40%) in the average annual consumption rate per individual and changes observed in the zooplankton community suggest that density-dependent effects may have increased since the 1970s. The current period of high stock sizes is also characterized by greater recruitment variability. Historical fecundity investigations have established that the average egg production per individual has decreased in all age groups by 20¿ 50%, along with a decrease in mean weight and condition. Yet, the effect on recruitment has been low so far, because lower fecundity has been compensated by the greater abundance and population fecundity has been maintained at the original level. Recruitment appears to be more influenced by environmental conditions than by spawning-stock biomass.
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