[ Introduction ]
[ State ]
[ Pressure ]
[ Response ]
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The condition of the herring population presently is good, and due to favourable spawning conditions between 1989 and 1995, the herring population has been increasing continuously in the last years.
The sprat population is characterised by wide fluctuations. Research in the Baltic Sea in 1996 indicates that the number of young sprats is low, and evidently a decrease of the sprat population can be expected.
In contrast to the pelagic fishes herring and sprat, cod is a demersal sea fish, and its reproduction is strongly influenced by poor water exchange in the deepest parts of the Baltic Sea. The total resources of cod in the beginning of 1990ies have diminished by 5 times (from 1 million to 200,000 tonnes). Already for many years, the cod catches have been over-caught to such an extent that the spawn shoal even under good spawning conditions could not ensure a generation of at least medium productivity. Additional factor is insufficient inflows of saltwater from the North Sea into the Gotland deep area resulting in poor replacement of saltwater and oxygen in the deep layers, creating adverse conditions for spawning.
According to the data for the 1990ies, the total number of salmon smolts in the Baltic Sea was 5.3 millions in each year, of which only around 400,000 (8%) arose in natural spawning. The maintenance of the natural populations and natural spawning is endangered by intensive catches both in the open sea and in coastal areas, and as a result, insufficient numbers of breeding fishes can reach rivers.
In Salaca, the main salmon river in Latvia, research and monitoring of young fish from natural spawning is conducted yearly. In spite of the natural fluctuations of the salmon population, these investigations indicate its stability during the last decades. The annual average number of salmon smolts in Salaca River is 26,000. In total, all rivers in Latvia provide annually 80 to 85 thousand natural salmon smolts.
Due to the stagnation of the hydrological conditions, the spawn shoal has been decreasing, and therefore an increase in the flounder population cannot be expected in the next years.
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