STOCKS: North-East Atlantic

. Atlanto-Scandian herring

The Atlanto-Scandian Herring complex is at present the largest one in the world. It consists of only two stocks inhabiting the entire mid and North-East Atlantic. The smaller part of the stock is the Icelandic Summer Spawning Herring, and the by far larger part the Norwegian Spring Spawning Herring. Both these stocks have experienced severe depletion during the late 60ies and throughout the 70ies. However, during the 80ies and 90ies both stocks have recovered tremendously and can be regarded healthy and inside safe biological limits*). While the stock of the Norwegian Spring Spawning Stock is currently shrinking due to recently weak recruitment, the Icelandic Summer Spawning Stock has climbed to levels which have never been recorded so far.

*) The term safe biological limits refers to fishery biological criteria with respect to the reproductive potential of the stock and optimum harvest strategies. It does not imply that neither the stock nor the species is in the immediate threat of biological extinction.

. Icelandic Summer Spawning herring

Main characteristics and peculiarities
• catches of the Icelandic summer spawning herring increased rapidly in the early 1960ies due to the development of the purse seine fishery off the south coast of Iceland. This resulted in a rapidly increasing exploitation rate until the stock collapsed in the late 1960ies. A fishing ban was enforced during 1972-1975. Thereafter the catches have increased gradually to over 100’000 t. In the most recent years a change in exploitation pattern has occurred with the increased exploitation of the 3- and 4-years old fish
• managed nationally by Iceland; no formal management strategy has been adopted, but the practice has been to management this stock at F=0.1 for more than 20 years. This fishing mortality is proposed as Fpa.

Assessment Summary
year 2000 (WG 2001)
type agreed assessment, single species: ADAPT
assessment quality good
main problems tendency to underestimate fishing mortality
fisheries independent information (1) hydroacoustic survey
catch 100'300 t (1999: 93'000 t)
spawning stock biomass 627'000 t (1999: 507'000 t)
fishing mortality F(adults [4-14])=0.18 (1999: 0.19)
reference points Blim (MBAL)=200'000 t, Bpa=300'000 t, Fpa(adults)=0.22
state of the stock within safe biological limits
perspective SSB at record high, excellent recruitment

Stock parameters (under construction)

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

Distribution
ISSH is distributed around Iceland (ICES Area Va). See map for detailled migration patterns.

. Norwegian Spring Spawning herring

Main characteristics and peculiarities
largest single herring stock in the world
• large increase in fishing effort, new technology and environmental changes contributed to the collapse of the stock in the early 70ies. Recruitment failed when the stock was reduced to below 2.5 mill t. In the following years the aim was to rebuild the spawning stock above this minimum limit. In order to reach this goal , after a period of almost no fishing, the management restricted the fishing between the years 1985-1993 to a fishing mortality of only F=0.05. In the late 80ies the stock recovered steadily. Most fishery in these years was coastal Norwegian fishery. During 1994 there were also catches in the offshore areas of the Norwegian Sea for the first time in 26 years. In 1997 the stock had reached about 9 mill. t and the fishery has reached catches of over one mill. t since 1996. However, the recent recruiting year classes are generally weak and it must be expected that the stock will decline in the near future.
•now managed according to an internationally agreed management plan

Assessment Summary
year 1999 (WG 2000)
type agreed assessment, single species: ICA
assessment quality medium
main problems (1) estimation of recruiting year classes
(2) inadaequate sampling of commercial catches
fisheries independent information (1) international hydroacoustic survey on SSB May-June
(2a) Norw. hydroacoustic survey on SSB in Feb-March
(2b) Norw. hydroacoustic winter survey on SSB in Dec.
(2c) Norw. hydroacoustic winter survey on SSB in Jan.
(3) hydroacoustic summer survey in the Barents Sea on juveniles in May-June
catch 1'207'300 t (1999: 1'235'000 t)
spawning stock biomass 6'725'000 t (1999: 7'790'000 t) expectet for 2001: 6'000'000 t
fishing mortality F(adults [5-14])=0.16 (1999: 0.16)
reference points Blim (MBAL)=2'500'000 t, Bpa=5'000'000 t, Fpa(adults)=0.15
state of the stock within safe biological limits, but F(adults) at Fpa
perspective SSB shrinking due to weak recruiting year classes. A stronger 1998-and 1999 year classes are possible, but not yet confirmed

Stock parameters (under construction)

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

Distribution
The Norwegian Spring Spawning Herring stock is known to undertake widespread feeding migrations through the NE-Atlantic during the summertime. The migration starts already in later winter in February, when the fish leave their over-wintering grounds in Fjords close to the Lofoten Islands. The fish spread out for spawning all over the Norwegian in March and April (Jakobsson & Østvedt, 1996; Slotte & Johannessen, 1997). After spawning the fish form schools and leave the coast in the search of food, while the hatched larvae drift north towards the Barents Sea (Svendsen et.al. 1995). In May these schools have reached the open sea, starting to forage in the Norwegian current. Depending on the local availability of the food (preferably Calanus copepods) they progress further west and usually also south, until the schools reach the polar front (Misund et al., 1997), the mixing zone of warm water of the Norwegian current and the cold water masses of the East Greenland current from the North. The Norwegian Spring Spawning Herring migrates along the front usually south during summertime. However in the recent years the schools have been migrating preferably northwards and are found at the latitude of the Lofoten Islands or even much further north. In September the schools start swimming towards the overwintering grounds in the Fjords at the Lofoten Islands again, where they stay inactive in densely packed schools (Foote & Røttingen, 1995; Huse et. A., 1997).

Source
ICES Northern Pelagic and Blue Whiting Working Group 2000, ICES CM 2000/ACFM:16, and 2001, ICES CM 2001/ACFM:17

Further reading
Foote, K.G & Røttingen, I. (1995) Acoustic assessment of Norwegian spring Spawning herring in the wintering area, December 1994 and January 1995. ICES C.M. 1995/H:9.
Huse, I., Foote, K.G. & Ostrowski, M. (1997) Dynamics of wintering Norwegian spring-spawning herring at the entrance to Tysfjorden, December 1996. ICES. C.M. 1997/CC:16.
Jakobsson, J. & Østvedt, O.J. (1996) A preliminary review of the joint investigations on the distribution of herring in the Norwegian and Iceland Seas 1950-1970. ICES C.M. 1996/H:14.
Misund, O.A., Fernö, A., Guenette, S., Mackinson, S., Melle, W., Nøttestad, L. & Slotte, A. (1997) Migration of herring along the cold front in the Norwegian sea in April 1997. ICES C.M. 1997/EE:12.
Slotte, A. & Johannessen, A. (1997) Spawning of Norwegian spring spawning herring (Clupea harengus L.) related to geographical location and population structure. ICES C.M. 1997/CC:17.
Svendsen, E., Fossum, P., Skogen, M.D., Eriksrød, G., Bjørke & Nedraas, K. (1995) Variability of the drift patterns of spring spawned herring larvae and the transport of water along the Norwegian shelf. ICES C.M. 1995/Q:25.

Data entered/updated by (Date)
Cornelius Hammer (07-06-00), Christopher Zimmermann (27-06-01)

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