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Separating two herring stocks from growth data: long‐term changes in survey indices for Western Baltic Spring Spawning Herring ( Clupea harengus ) after application of a stock separation function

Separating two herring stocks from growth data: long‐term changes in survey indices for Western... Summary In the Baltic Sea, herring stocks are surveyed and managed according to a spatial allocation based on ICES (International Council for the Exploration of the Sea) subdivisions. In the western Baltic, the distribution areas of two stocks overlap: the Western Baltic Spring Spawning Herring (WBSSH) and the Central Baltic Herring (CBH). Survey results of length‐at‐age data indicate in Subdivision (SD) 24, which is a part of the WBSSH management area, that a considerable fraction of CBH is present and correspondingly erroneously allocated to WBSSH stock indices. Accordingly, a stock Separation Function (SF) based on growth parameters was established to identify the fraction of CBH in the WBSSH area. In the present study, the SF was applied to 8 years of data from the GERman Acoustic Survey (GERAS), which is conducted annually in autumn in ICES subdivisions 21‐24. Results showed a distinct fraction of CBH in SD 24, and exclusion of the CBH greatly improved the quality of the GERAS index used in the assessment of the WBSSH stock. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Ichthyology Wiley

Separating two herring stocks from growth data: long‐term changes in survey indices for Western Baltic Spring Spawning Herring ( Clupea harengus ) after application of a stock separation function

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References (12)

Publisher
Wiley
Copyright
Copyright © 2016 Blackwell Verlag GmbH
ISSN
0175-8659
eISSN
1439-0426
DOI
10.1111/jai.12924
Publisher site
See Article on Publisher Site

Abstract

Summary In the Baltic Sea, herring stocks are surveyed and managed according to a spatial allocation based on ICES (International Council for the Exploration of the Sea) subdivisions. In the western Baltic, the distribution areas of two stocks overlap: the Western Baltic Spring Spawning Herring (WBSSH) and the Central Baltic Herring (CBH). Survey results of length‐at‐age data indicate in Subdivision (SD) 24, which is a part of the WBSSH management area, that a considerable fraction of CBH is present and correspondingly erroneously allocated to WBSSH stock indices. Accordingly, a stock Separation Function (SF) based on growth parameters was established to identify the fraction of CBH in the WBSSH area. In the present study, the SF was applied to 8 years of data from the GERman Acoustic Survey (GERAS), which is conducted annually in autumn in ICES subdivisions 21‐24. Results showed a distinct fraction of CBH in SD 24, and exclusion of the CBH greatly improved the quality of the GERAS index used in the assessment of the WBSSH stock.

Journal

Journal of Applied IchthyologyWiley

Published: Feb 1, 2016

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