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Huusko A.,Finnish Game And Fisheries Research Institute | Louhi P.,University of Oulu
Freshwater Biology | Year: 2012

Rivers in boreal forested areas were often dredged to facilitate the transport of timber resulting in channels with simplified bed structure and flow fields and reduced habitat suitability for stream organisms, especially lotic fishes. Currently, many streams are being restored to improve their physical habitat, by replacing boulders and gravel and removing constraining embankments. The most compelling justification behind stream restoration of former floatways has been the enhancement of native fish populations, specifically salmonids. We examined the success of a stream management programme aimed at re-building diminished brown trout (Salmo trutta) populations by monitoring densities of young-of-year and older trout in 18 managed and three reference streams during 2000-2005. Rehabilitation included in-stream restoration combined with a 5-year post-restoration period of stocking young brown trout. Our space-for-time substitution design comprised four pre-management, four under-management, 10 post-management and three reference streams. Densities of young-of-year brown trout, indicating population establishment, were significantly higher in post- compared with pre-management streams. However, density of young-of-year brown trout in post-management streams was significantly lower compared with near-pristine reference streams. Furthermore, success of managed brown trout population re-building varied, indicating stream-specific responses to management measures. Density of burbot (Lota lota), a native generalist predator, was associated with low recruitment of brown trout. Stream-specific responses imply that rehabilitation of brown trout populations cannot be precisely predicted thereby limiting application. Our findings support the importance of adaptive stream restoration and management, with focus on identifying factor(s) limiting the establishment of target fish populations. © 2012 Blackwell Publishing Ltd. Source

Vainikka A.,University of Eastern Finland | Hyvarinen P.,Finnish Game And Fisheries Research Institute
Fisheries Research | Year: 2012

Due to the multitude of participants and a diverse range of fishing gear used freshwater fisheries are often managed using minimum size limits (MSL) rather than regulations of total fishing effort. However, a concern has arisen whether attempts to improve ecological sustainability of fisheries by increasing MSLs would induce undesired adaptations to selective fishing. We examined the ecological and evolutionary impacts of varying fishing mortality rates under varying MSLs, with and without stockings, in an age-, size-, and maturity-structured evolutionary model which was parameterized for the Lake Oulujärvi pikeperch, Sander lucioperca. We found that at the current level of harvesting (fishing mortality rate, F=0.7) and stockings (430000 year -1), and under the assumption of strongly density-dependent growth, the nation-wide MSL of 370mm maximizes theoretical biomass yield in a deterministic model but does not prevent severe recruitment overfishing under further increased fishing pressures or stochasticity in recruitment success. The recently imposed, local MSL of 450mm better ensures stable yields, and even increases them if individual growth is density-independent, but further increase of MSL to 500mm would already reduce yield especially if there was discard mortality for undersized fish. Given density-dependent growth, equal survival between wild and stocked fish, and sustainable fishing mortality rate, stockings do not increase yield or significantly improve the stability of yields. Evolutionarily stable size at maturation decreases under strong fishing mortality, but increased MSLs reduce the magnitude of this undesired effect. Negatively size-dependent natural mortality was found to have a positive effect on the otherwise negative selection for length-at-age. Increased MSLs also reduce the total selection for decreased length-at-age. Our results support the intentions to increase MSLs in order to improve both ecological and evolutionary sustainability of recreational fisheries. © 2011 Elsevier B.V. Source

Salmi P.,Finnish Game And Fisheries Research Institute
Maritime Studies | Year: 2012

The concept of social sustainability is occasionally used in fisheries political argumentation, but practical policies are typically guided by ecological and economic arguments rather than the social. On the other hand, social justice and moral acceptability are general prerequisites for successful fisheries governance. This paper studies the changing social dimensions in Finnish fisheries where interactions between the water-owner-based management system and various user groups have produced enduring contradictions. Along with a shift towards recreational fishing, the national and international levels of fisheries governance have largely replaced the local owner-based management system. Consequently, increasing numbers of new interest groups, rural-urban relations, management measures and governance institutions have become part of the fisheries complex. Contradictions typically culminate in fishing rights and the power to decide over access to fishing waters. The biodiversity and wildlife conservation measures have often underrated the social, as well as economic, aspects of fishing. © 2012 Salmi. Source

Heikinheimo O.,Finnish Game And Fisheries Research Institute
Ecological Modelling | Year: 2011

The interactions between cod (Gadus morhua), herring (Clupea harengus) and sprat (Sprattus sprattus) in the Central Baltic Sea were examined with a simple dynamic model, an alternative to more complicated and data-demanding multispecies and ecosystem models. The main aims of the study were to compare the effect of alternative structures on the model output and examine the control relationships in the fish assemblage under different environmental conditions. The effect of environmental conditions was modelled using a stock-recruitment equation for cod incorporating an environmental index. The model output was especially sensitive to the functional response in predation by cod on herring and sprat. The type II functional response led to a collapse of the clupeid stocks when cod was abundant, while the type III response produced more realistic stock dynamics. According to the simulations, an abundant cod stock was able to keep the sprat stock at a low level, while the herring stock was less affected and benefited from the decreased density of sprat. Simulation of different fishing scenarios indicated that reducing fishing mortality to the level currently advised by ICES would allow the recovery of the cod stock even in unfavourable environmental conditions. © 2011 Elsevier B.V. Source

Hiedanpaa J.,Finnish Game And Fisheries Research Institute | Bromley D.W.,University of Wisconsin - Madison
Environmental Policy and Governance | Year: 2011

Since Finland joined the European Union (EU) in 1995, the European Commission has shown growing impatience with how EU rules with respect to protection of wolves and other large carnivores have been enforced within Finland. In 2005 the Commission referred the matter to the European Court of Justice, which subsequently found Finland deficient in the strict protection of wolves. We investigate the reasons underlying the court case. We identify two problems in the realm of 'reason giving'. The first problem arises from the lack of a causal model linking decentralized actions on the part of the subjects of administrative rules with the desired outcomes imagined by the centralized entities issuing the new administrative rulings. The second problem arises from the authoritarian tendencies of the EU that fail to understand the context of wolves for rural livelihoods in Finland. Both of these problems give rise to surprising practical effects emerging from the 'harmonization game'. We introduce the concept of 'instrumentality' with respect to the goal of sustainable wolf populations. We also introduce the concept of 'inverse high-grading' of wolves under the umbrella of biodiversity protection. The EU and the people of rural Finland will continue to struggle over wolves until a more coherent policy goal, and a more defensible administrative rule structure, can be formulated. © 2010 John Wiley & Sons, Ltd. and ERP Environment. Source

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