Problems in Fisheries and Management of Fish Resources in the Gulf of Riga
Fisheries, health resorts, tourism and maritime transportation connected with the Gulf of Riga have been of special importance for Estonia and Latvia.
Due to the special characteristics of its nature, the gulf supports a variety of organisms with different adaptational backgrounds. The most important are eurytherm euryhaline marine boreal species. Freshwater species are mainly distributed in south-eastern areas, especially in the estuaries of large rivers — the Daugava, Lielupe, Gauja, Pärnu etc. Glacial relicts are mostly inhabitants of deeper water layers.
The dynamics of the stocks are directly or indirectly connected with fluctuations in climatic conditions. The effects of pollution have been controversial. Eutrophication has increased the productivity in the pelagic system but deteriorated the conditions for benthic animals.
The total fish catches within the Gulf of Riga have varied from an average of 13,000 tonnes in the 1930s to the peak figures in the late 1960s and early 1970s (50,000–90,000 tonnes). During the 1990s, they have fluctuated around a moderate level (20,000–30,000 tonnes). Presently, the catches of pelagic fish are good, but demersal stocks are at a low level. The abundance of some cold-water fishes (eelpout, smelt) is increasing. However, the stocks of four-horned sculpin, sea snail and a number of other relict species remain depleted.
In the management of the Gulf of Riga fish resources it should be taken into account that some species (e.g. spring spawning herring) have developed a local population in the gulf which should be assessed and managed separately. Eutrophication should be controlled and overexploitation of fish stocks avoided. This would allow an optimisation of the yield of both commercial mass species and valuable fishes, the suppression of inferior fishes, and it would contribute to the stabilisation of the gulf’s ecosystem. The recently increased tension in the management of living resources connected with the increase in the abundance of top predators (seals, cormorants) should be regulated.
KeywordsBiomass Migration Depression Transportation Respiration
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