Effectiveness of fishing regulations Fishing is regulated – how about the results?Unregulated fishing may lead to a situation in which fish are harvested before their first spawning. Fishing regulations are in place to make the optimal profit from the fish stock and secure fish breeding. This project examines the effects of fishing regulation on:
- fish stocks
- fish communities
- catches and fishing efforts of professional fishermen and anglers
- attitudes of fishermen
The project methods employ modelling and the effects of regulation are monitored by means of fishing surveys and experimental fishing. The results are used to develop the regulation of fishing for different kinds of watersheds and to fulfil various objectives.
Effects of mesh-size regulation in lakes
Gillnet fishing has been regulated since the late 1990s in fishing areas such as Kolovesi and Koitere in the Vuoksi watershed.
Gillnet fishing with mesh sizes smaller than 110 mm (stretched mesh) is forbidden in areas where the overall water depth is more than 10 m.
The aim is to preserve a larger percentage of small individuals that will grow to become large predatory fish (sander, brown trout, landlocked salmon) from catches that target small fish, thereby allowing the young predatory fish to grow to spawning size.
As a result, net fishing with dense nets has decreased by one third and the mean size of caught sanders has increased from 700 g to one kilo. Regulation did not affect the total catches of any fish species.
The effects of the mesh-size change on professional fishing for sander
The increase in mesh size from the current 86 mm to 100 mm or 110 mm (stretched mesh) was studied with modelling in the Finnish Archipelago. Economic factors were also considered, because most sander fishing is done on a professional basis. An increase in mesh size would cause a loss of profit for professional fishermen, creating economically intolerable consequences that would have an effect lasting up to 8 years. (Fisheries Research 77)
Saimaa ringed seal diet does not adversely affect vendace stock
The effects of Saimaa ringed seal on the vendace stock were studied with modelling in the Pihlajavesi area of the Saimaa watershed. In Pihlajavesi, ringed seals consume about 68 tonnes of fish per year. When the vendace stock is strong, seals do not cause any significant harm to fishing, or increase the need for fishing regulations. (Biological Conservation 125)
Stocking of land-locked salmon affects vendace recruitment
CPUE, echo sounding and age structure data were used to assess the regulation needs of vendace fishing in Lake Paasivesi.
The feeding of stocked land-locked salmon was assessed with modelling to have a key role in determining the size of vendace stocks. It would be possible to increase the recruitment of vendace by increasing the spawning stock size of vendace with fishing regulations. (Ann. Zool. Fennici 41).
Scientist in charge of project
Heikki Auvinen
Turku Game and Fisheries Research
Itäinen Pitkäkatu 3
FI-20520 Turku, Finland
Tel. +358 205 751 695
E-mail: firstname.lastname@rktl.fi
Other research staff: Outi Heikinheimo, Juha Jurvelius, Irma Kolari, Jari Raitaniemi
Cooperation
The fishing areas of the Vuoksi watershed, the Technological Development Centres of Finland, the Swedish Board of Fisheries, the Northern Fisheries Research Institute of Russian Karelia, and the University of Durham (UK), among others.
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