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Bothnian Sea (Southern Bothnian Bay) herring

Main characteristics and peculiarities
• total allowable catches are set combined for Northern and Southern Bothnian Bay herring.
• coastal spring spawning and feeding/wintering areas on the slopes/in the open sea
• most of the catches are taken by trawl fishery, which became much more effective during the last decade
• a large proportion of the catches is used as animal food

Assessment Summary
year	2000 (WG 2001)
type	single species: Extended Survivors Analysis (XSA)
assessment quality	medium, has improved in recent years
main problems	(1) unreported catches (2) low quality of tuning data
fisheries independent information	(1) Fishing effort in three fleets: Trapnet, Pelagic trawl, Demersal trawl (2) Acoustic Survey since 1999
catch	61'300 t (1999: 61'600 t)
spawning stock biomass	213'000 t (1999: 185'700 t)
fishing mortality	F(adults [3-7])=0.30 (1999: 0.34)
reference points	Bpa: 200'000 t, Blim: 145'000 t, Fpa: 0.21, Flim: 0.30
state of the stock	outside safe biological limits (SSB below Bpa, F above Fpa)
perspective	unclear

Stock parameters (under construction)

This standard figure can be downloaded as a printable pdf-file (requires Acrobat Reader)

Distribution
Southern Bothnian Bay (Bothnian Sea) herring is distributed in Sub-Division 30. The current TAC is, however, set for Sub-Divisions 29 (North), 30 and 31.

Management advice
Fishing mortality should be reduced to below Fpa=0.21, corresponding to catches of less than 39'500 t in 2002.

Migration pattern
Migrations to the south or north are unusual.

Spawning
Two spring spawning coastal herring populations are inhabiting the Bothnian Sea: one along the west and one along the east coast (Aro 1989). Both populations are spawning in May-July. The feeding migration starts soon after spawning. The main feeding/wintering areas are the slopesand the open sea of the Bothnian Sea .The autumn spawning stock is very small.

Stock separation
Vertebrae counts are generally higher than in the Central Baltic but also more variable (mean 55.10-55.60, ICES 1998/H:2)

References
Aro, E. 1989: A review of fish migration patterns in the Baltic. Rapp. P. –v. Reun. Cons. Int. Explor Mer 190: 72-96.
ICES 1998. Report of the Baltic Herring Age-Reading Study Group. ICES CM 1998/H:2. 86 pp.

Source
ICES Baltic Fisheries Assessment Working Group 2000, ICES CM 2000/ACFM:14, and 2001, ICES CM 20010/ACFM:16

Data entered/updated by (Date)
Christopher Zimmermann (01-07-00)/Tomas Gröhsler (06-11-00/27-06-01)

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