Hyvarinen P.,Finnish Game And Fisheries Research Institute |
Rodewald P.,Finnish Game And Fisheries Research Institute |
Rodewald P.,University of Helsinki
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2013
Low survival of stocked fish has been associated with fitness declines of the captive reared fishes because of genetic domestication and unnatural rearing environments. The effects of broodstock origin (wild or captive) or rearing method (standard or enriched) on survival and migration of hatchery-reared Atlantic salmon smolts (Salmo salar) were investigated in the Tornionjoki River using radiotelemetry. Smolts that were reared with enriched methods had a twofold increase in survival (∼38%) compared with smolts that had been reared in a standard hatchery environment (∼19%). Nature-caught smolts had highest survival (∼57%). Smolts from enriched rearing had a higher initial migration speed than fish from standard rearing. Initial migration speed during the first 3 km was positively correlated to survival probability after 290 km for hatchery fish. There was no clear effect of origin on survival or migration speed. The results of this study show that enriching the rearing environment with methods easily applicable to large-scale production promotes smolt survival and migration speed during river migration, which is imperative for stocking success.
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.
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.
Suuronen P.,Finnish Game And Fisheries Research Institute |
Lehtonen E.,Finnish Game And Fisheries Research Institute
Fisheries Research | Year: 2012
We examined the digestive tract contents of 63 Baltic grey seals (Halichoerus grypus) and 37 Baltic ringed seals (Phoca hispida botnica) collected during May to November in 2008 and 2009 in the northern part of the Bothnian Bay to assess the role of Atlantic salmon (Salmo salar) and sea trout (Salmo trutta) in the diet of seals. For grey seals the three most common prey species in numbers were vendace (Coregonus albula), Baltic herring (Clupea harengus) and common whitefish (Coregonus lavaretus). Thirteen grey seals contained remnants of a total of 93 salmonids (Atlantic salmon and sea trout). Salmon ingested were, in general, older and larger than the ingested sea trout. Six grey seals had in their digestive tract Carlin-tags which are used to mark stocked salmonid smolts. Stocked sea trout appear particularly vulnerable to predation during the first months after the stocking. Our study suggests that salmonids may play a marked role in the diet of grey seals during the season when salmonids aggregate in coastal waters in the Bothnian Bay. Three-spined stickleback (Gasterosteus aculeatus), Baltic herring, smelt (Osmerus eperlanus) and vendace dominated in the ringed seal's diet. No salmonids were found in the dietary tracts of ringed seals. © 2012 Elsevier B.V.
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.
Kauhala K.,Finnish Game And Fisheries Research Institute |
Kowalczyk R.,Polish Academy of Sciences
Current Zoology | Year: 2011
We aimed to review the history of the introduction and colonization of the raccoon dog Nyctereutes procyonoides in Europe, the features behind its successful expansion and its impact on native fauna. The raccoon dog quickly colonized new areas after being introduced to the European part of the former Soviet Union. Today it is widespread in Northern and Eastern Europe and is still spreading in Central Europe. Features behind its success include its adaptability, high reproductive potential, omnivory, hibernation in northern areas, multiple introductions with > 9000 individuals from different localities, and tendency to wander enabling gene flow between populations. Firm evidence of the raccoon dog's negative impact on native fauna, such as a reduction in bird populations, is still scarce. Raccoon dogs may destroy waterfowl nests, although a nest predation study in Latvia did not confirm this. Predator removal studies in Finland suggested that the raccoon dog's impact on game birds is smaller than expected. However, raccoon dogs may have caused local extinction of frog populations, especially on islands. Raccoon dogs may compete with other carnivores for food, for example for carrion in winter, or for the best habitat patches. In northern Europe potential competitors include the red fox Vulpes vulpes and the badger Meles meles, but studies of their diets or habitat preferences do not indicate severe competition. The raccoon dog is an important vector of diseases and parasites, such as rabies, Echinococcus multilocularis and Trichinella spp. and this is no doubt the most severe consequence arising from the spread of this alien species in Europe. © 2011 Current Zoology.
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.
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.
Hiedanpaa J.,Finnish Game And Fisheries Research Institute
Ecology and Society | Year: 2013
Finland has struggled with formulating and implementing policies regarding the national grey wolf (Canis lupus) population. It seems that after major institutional adjustments undertaken to improve wolf protection, the wolf population has, in fact, decreased. This calls for an explanation. My approach to the question of institutional fit builds upon classical institutional economics and pragmatism. I will apply Charles S. Peirce's conception of habits and his theory of categories and the idea of normative sciences. The case study from southwestern Finland shows that if the institutional designers would address the habits of feeling, mind, and action, including their own, that frame and constitute the problematic situation and potential solutions, the critical conditions of institutional fit would be more tangible and easier to identify and handle. As long as policy adjustments are reactive and compulsive and not built upon a reasonable engagement of whole epistemic community in habit-breaking and habit-taking, policies will most likely fail. © 2013 by the author(s).
Lehtonen E.,Finnish Game And Fisheries Research Institute |
Suuronen P.,Finnish Game And Fisheries Research Institute
Fisheries Research | Year: 2010
Seal-induced catch damages have increased dramatically in the coastal trap-net fishery in the Baltic Sea. Most damage is caused by the rapidly growing grey seal (Halichoerus grypus) population. These seal-fishery interactions require practical and sustainable solutions. A potential measure is capture of live seals using fishers' commercial trap-nets. The benefit of this approach to fishers would be to catch "nuisance" seals that have learned to use commercial fishing gear for finding their food sources and to remove them in an ethical way while endangered species could be released. We developed a capture system that can easily be installed into a modern salmon trap-net, commonly referred to as the pontoon trap. The aim was to develop a technique that enables undisturbed fishing while allowing live-capture of seals. Development work involved the testing of various structures and recording the behaviour of seals and fish on video. This paper demonstrates the criteria for a successful trap design and presents some observations of seal behaviour. The technique developed provides a unique method for scientific studies where seals have to be captured alive. © 2009 Elsevier B.V. All rights reserved.