Salmon

Anadromous fish species such as salmon (Salmo salar) spend most of their lives in the sea, but then migrate into fresh waters to spawn. In genetic terms, each of the salmon rivers contains a unique population and therefore the loss of even a single river population is irreversible. The decline of Baltic salmon stocks started already in the mid-19th century and since about the same time, artificial stocking activities were started. Decline of natural stocks was essentially fast since the late 1940s, because of the construction of hydroelectric power plants, damming and pollution of the Baltic rivers and river mouths.

The Baltic countries have carried out extensive restocking programs for salmon many years. Salmon fry are raised in artificial hatcheries and then released to compensate for the loss of the natural spawning areas. This has staved off the extinction of the Baltic salmon, but has also inevitably diminished the overall genetic diversity of the population as wild fish interbreed with hatchery-reared fish, which have low genetic variability.

The recent development of wild salmon stocks

The natural smolt production of salmon populations has improved in recent years and salmon is recovering after having been in danger of extinction. The proportion of truly wild salmon among hatchery-reared fish declined in 1990s from 14% to less than 8%, but increased between 2000 and 2007 from 17% to over 60% in the catch samples in the Bothnian Bay. The production of wild Baltic smolt has increased up to 2 million from the figure of 0.3 million in 1995 (report/2008/Baltic Sea). The former International Baltic Sea Fishery Commission (IBSFC) established a goal to have at least 50% of the potential smolt production in a number of salmon rivers reached by 2010. Most of the northernmost stocks are either likely or very likely to reach this objective, while the stocks in the more southern areas have slightly more varying and on average poorer status (ICES 2007-2008).

A key factor influencing the stocks currently is the lower survival rate of post-smolts in the sea. The scientists do not know the reasons behind the decrease, but the current hypotheses associate the low survival rate to food competition, seal abundance and fitness of hatchery-reared salmon.

The fisheries and management of salmon

ICES divides salmon stocks to 6 assessment units in the Baltic Sea (report/2008/Baltic Sea). The smolt production in the units 1-3 in the Bothnian Sea and in the rivers of the Bothnian Bay has increased and is at the moment close to the potential production of the rivers. In the rivers of assessment units 4-6 the smolt production has not been as good. Proportion of wild salmon in catch samples has risen continuously during 2000s and is now at the level of 60 % in the Bothnian Bay.

As the offshore salmon fishery has declined, the natural smolt production has improved in recent years in the northern Baltic rivers. The salmon catches in 2007 were at their lowest level in records since 1970 (ICES 2007). Offshore and coastline fishery has been reduced for many reasons, e.g. low price and high content of dioxin.

Due to total ban of EU driftnet fishery as of January 2008 the salmon catches are expected to be leven ower in the future. This will likely result in an increased number of salmon spawners. However, the impact of the increased number of spawners will be offset by continued low survival rates in sea. In order to ensure the recovery of the salmon stocks, ICES recommends that landings in 2009 in the Baltic Proper and in the Gulf of Bothnia should not exceed the catches expected for 2008.

Fisheries and the adopted TACs of salmon in the Gulf of Finland have decreased continuously in the recent years. ICES is advising that fisheries should only be permitted at sites where there is virtually no chance of taking wild salmon. To improve selectivity of harvesting, coastal fisheries at sites likely to be on migration paths of wild salmon from Estonian rivers should be prohibited. Poaching also occurs in these rivers and must be stopped. Fishing in rivers and river mouths supporting wild stocks should be prevented (report/2008/Baltic Sea).

A new management plan for Baltic salmon in 2009

In 1995-97 IBSFC launched the Salmon Action Plan 1997-2010 together with HELCOM in order to prevent the extinction of the wild Baltic salmon. Attempts have been made to rebuild stocks to at least 50% of their potential reproductive capacity. As part of the plan the IBSFC listed rivers with naturally reproducing salmon populations whose stocks should no longer be artificially supplemented after 2005.

A new management plan for the Baltic salmon is currently being prepared by the European Commission and is expected to be proposed in 2009. One important element of the new plan will in all probability be to set stock or river specific management targets for Baltic salmon. The estimation of the potential smolt production, especially in small rivers, is difficult due to limitations in the amount of relevant information on the rivers.

HELCOM’s river inventory

HELCOM is planning to contribute to the EC management plans by an inventory project aiming at a new classification of the Baltic salmon and sea-trout rivers. Updated information on the status of the rivers is needed and a new inventory of Baltic salmon and sea trout rivers needs to be carried out. This inventory will be put into effect on a project basis and in cooperation with the competent scientists and all the Baltic Sea state fisheries and environmental administrations.

 

 

Last updated 10 December 2008