The area of this action is Lake Päijänne (1060 km2) and its watershed area (southern Finland, Lake Päijänne FinLTSER site). Lake Päijänne is the second largest lake in Finland. It is a very important area for recreational fishing (with more than 100 000 recreational fishermen) and also for profes-sional fishing. Lake water is used as tap water for more than 1 milj. people in Helsinki metropol area. Lake is loaded by municipal waste waters of 300 000 inhabitants living around the lake. At present lake water is of very good quality but concerns rise due to the climatic change and increasing human activities around the lake and catchment.
The aim is to estimate the changes induced by the climate change in fisheries production in L. Päijänne. The climate change can have profound effects on fish stocks and thus also on fisheries and fish industry and marketing. The sustainable management of fish stocks and fisheries needs infor-mation on expected changes for successful adaptation.We will predict the changes in fisheries production (growth, reproduction, recruitment) of the most important fish species (vendace, whitefish, smelt, pikeperch, perch, brown trout and roach ; production of certain species is dependent on the natural reproduction but the stocks of others are maintained by the fish stockings) by probabilistic modelling approach. The analysis of changes in fish production includes biomass, species distribution and economic value.
Further, the effects on fishing operation in winter and summer fishing seasons will be analysed. For instance, the changes in the duration of ice period will affect remarkably the total effort of different gear used by commercial fishermen in Lake Päijänne.
This action also aims to assess the impact of climate change impact on nutrient and organic matter wash off and load from catchment area. Because the load from industry and communities has decreased, load from catchment area is now the most important risk for water quality in L. Päijänne. Climate change affects to ice-covered period of the lake and unfrozen period of catchment areas. These changes can have serious effects on lake thermal system, load from catchment area and thus on water quality. These can furthermore affect to whole lake ecosystem and ecosystem services of the lake, for example usability of water or recreational use of the lake.
Methods employed
The data on growth and recruitment of important fish species will be analyzed in relation to temperature. The changes in fish production will be derived for different species. Fish growth in relation to available food resources will be estimated with bioenergetics models. Risk evaluation will be used to find out which parameters are the most critical according to our present knowledge. Focus group method used widely in social science will be applied to build up the model constructions for local fisheries system and the relevant variables in relation to climate change problems.
Data for water quality and loading assessments are well available from the Lake and its catchment. Data sets on meteorology and lake hydrology are some of the longest in Finland. In this work we will model the nutrient load from catchment area applying unit loading and GIS-approach as well as collecting data available on point loads. For lake modelling we use a one dimensional hydrophysical and water quality model, which has been applied already in climatic change studies in several lakes of Finland.
Expected results
In general the results support the decision-making of the sustainable use of aquatic resources and produce information e.g. in action plans in fish stock managements, especially stocking plans, adaptation of professional fishery to new fishing methods, innovation of new fisheries products, market plan of professional fishery and industry. Furthermore, the action will create new awareness among decision makers and public about the possible changes and risks concerning lake water quality and hydrology, as well as innovation and adaptation of new techniques for lake protection.
Contact person
Juha Karjalainen, University of Jyväskylä, juhakar(at)bytl.jyu.fi