Fish and fisheries in large regulated peaking-power river reservoirs in northern Finland, with special reference to the efficiency of brown trout and rainbow trout stocking
✍ Scribed by Vehanen, Teppo
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 164 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0886-9375
No coin nor oath required. For personal study only.
✦ Synopsis
The Oulujoki, Iijoki and Kemijoki Rivers in northern Finland, all of them previously important rivers for the fishing of migratory salmonids, were dammed for hydropower production in the 1940s-1960s. Some 20 years after the construction of the last power plant, the fish communities, fishing and the effects of brown trout (Salmo trutta m. lacustris) and rainbow trout (Oncorhynchus mykiss) stocking were studied in fifteen reservoirs, five in each of these rivers. Test fishing, echo sounding and fish tagging were used to collect descriptive information about the fish communities and the distribution and movements of fish. Catch statistics were used to estimate the yields and the fishing in the reservoirs. The results showed similarity in the fishing effort and the fish stocks in the reservoirs studied. Cyprinids, especially roach (Rutilus rutilus), were the most numerous species in the area. The hydroacoustic survey suggested that most of the fish occurred near to the river banks. Fishing in these reservoirs has recently increased, but it is mostly directed at predatory species rather than roach. The increase in the amount of fishing can partly be attributed to the stocking of rainbow trout of a takeable size (018-112 kg), which give good yields. Poor yields resulting from the previously standard stockings of brown trout smolts have been improved by stocking fish exceeding 30 cm in length. The results, however, show that stocking is not profitable in all the reservoirs. The future prospects for recreational rod fishing in the reservoirs are good, but improvements in the conditions for operating traps and gill nets are needed to optimize yields. This could include an intensive stocking of predatory fish, brown trout and rainbow trout.