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Northern 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 at the slopes and in the open sea
• most of the catches taken by demersal trawl fishery
• extreme environmental conditions: temperature highly variable, salinity very low
• low exploitation rate

Assessment Summary
year	2000 (WG 2001)
type	single species: Extended Survivors Analysis (XSA)
assessment quality	poor, 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
catch	3'000 t (1999: 4'200 t)
spawning stock biomass	11'000 t (1999: 14'300 t)
fishing mortality	F(adults [3-7])=0.28 (1999: 0.41)
reference points	not defined
state of the stock	uncertain
perspective	uncertain, but rather high exploitation rate

Stock parameters (under construction)

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

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

Management advice
Exploitation rate should be decreased.

Migration pattern
Herring is stationary in this area. Some migrations to the south (Southern Bothnian Bay/Bothnian Sea) may occur.

Spawning
Spawning starts in late May and ceases by late July. The feeding migration occurs mainly inside the Bothnian Bay (Aro 1989).

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 (21-07-00)/Tomas Gröhsler (06-11-00/27-06-01)

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