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| 2. |
- Bergek, Sara, et al.
(författare)
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From individuals to populations : Impacts of environmental pollution on natural eelpout populations
- 2012
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Ingår i: Ecotoxicology and Environmental Safety. - : Elsevier BV. - 0147-6513 .- 1090-2414. ; 79, s. 1-12
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Forskningsöversikt (refereegranskat)abstract
- Investigating how individuals are affected by environmental pollution is relatively straightforward, for example through conducting field studies or laboratory toxicity tests. Exploring such effects at a population level is considerably more difficult. Nonetheless, the exploration of population-level effects is important as the outcomes may differ from those seen at the individual level. Eelpout (Zoarces viviparus L) have been used for several years as a bioindicator for hazard substances in both the field and laboratory tests, and individual effects on reproduction have been reported. However, the influence of these effects at the population level remained unexplored. In this study, four Leslie matrix models were parameterized using data from non-polluted eelpout populations (Skagerrak, Baltic Proper, Gulf of Bothnia and Gulf of Finland). The four sites represent an environmental gradient in salinity. Furthermore, life-history data revealed differences between the sites with growth rate, fecundity, age at maturity and longevity being the most significant. The effect of pollution on natural eelpout populations was then simulated by combining the outputs from the Leslie matrices with data from laboratory and field studies exploring reproductive impairment in contaminated environments. Our results show that despite differences in life-history characteristics between sites, survival of early life stages (i.e. larvae and zero-year-old fish) was the most important factor affecting population growth and persistence for all sites. The range of change in survival of larvae necessary to change population dynamics (i.e. growth) and persistence is well within the range documented in recipient and experimental studies of chemicals and industrial waste waters. Overall, larval malformation resulting from environmental pollution can have large effects on natural populations, leading to population losses and possibly even extinction. This study hereby contributes valuable knowledge by extending individual-level effects of environmental contaminants to the population level. (C) 2012 Elsevier Inc. All rights reserved.
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| 3. |
- Hansson, Sture, et al.
(författare)
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Competition for the fish - fish extraction from the Baltic Sea by humans, aquatic mammals, and birds
- 2018
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 75:3, s. 999-1008
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Tidskriftsartikel (refereegranskat)abstract
- Seals and fish-eating birds have increased in the Baltic Sea and there is concern that they compete with fisheries. Using data from around year 2010, we compare consumption of different fish species by seals and birds to the catch in the commercial and recreational fishery. When applicable this is done at the geographical resolution of ICES subdivisions. Predation by birds and mammals likely has limited impact on the populations of the commercially most important species (herring, sprat, and cod). In the central and southern Baltic, seals and birds consume about as much flatfish as is caught by the fishery and competition is possible. Birds and seals consume 2-3 times as much coastal fish as is caught in the fishery. Many of these species are important to the fishery (e. g. perch and whitefish) and competition between wildlife and the fishery is likely, at least locally. Estimated wildlife consumption of pike, sea trout and pikeperch varies among ICES subdivisions and the degree of competition for these species may differ among areas. Competition between wildlife and fisheries need to be addressed in basic ecosystem research, management and conservation. This requires improved quantitative data on wildlife diets, abundances and fish production.
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| 4. |
- Hansson, Sture, 1953-, et al.
(författare)
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Response to comments by Heikinheimo et al. (in press) on Hansson et al. (2018): competition for the fish—fish extraction from the Baltic Sea by humans, aquatic mammals, and birds
- 2018
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 75:5, s. 1837-1839
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Tidskriftsartikel (refereegranskat)abstract
- As discussions and debates are crucial to science, we appreciate the comments by Heikinheimo et al. (in press) on our article on competition for Baltic Sea fish resources between fishery and wildlife. We cannot see that the comments by Heikinheimo et al. changes the general conclusion derived in our original article—that there are cases of competition between wildlife and fisheries in the Baltic Sea, although not for all species and not to the same extent everywhere. Our responses are structured in the same order as the comments by Heikinheimo et al.
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| 6. |
- Rohtla, Mehis, et al.
(författare)
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Conservation restocking of the imperilled European eel does not necessarily equal conservation
- 2020
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; , s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- To stop the decline of the European eel population, one of the measures taken is translocating eels for restocking, despite its conservational value being largely unknown. We aimed to contribute to this knowledge gap by (i) investigating the origin of eels caught in coastal waters of Estonia and Finland using otolith microchemistry and (ii) directly estimating restocked eel escapement from Narva River Basin District (NRBD), which is part of the primary Eel Management Unit in Estonia. In Estonia, 74% of the sampled eels (n=140) were natural recruits and 26% were restocked. In Finland, 27% of the sampled eels (n=235) were natural recruits and 73% were restocked. Only 1% of all the coastally collected eels were originally restocked to NRBD. These new data together with the reported commercial landings from the escapement route conflict with the current silver eel escapement estimation for NRBD and question the accuracy and value of such indirect calculations compiled for most Eel Management Units throughout the European Union. It is concluded that restocking eels to freshwaters may be futile as a conservation measure in some situations, and better escapement is likely achieved in restocking eels to coastal waters or undammed freshwater systems with a direct connection to the sea.
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| 7. |
- Tverin, Malin, et al.
(författare)
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Complementary methods assessing short and long-term prey of a marine top predator ‒ Application to the grey seal-fishery conflict in the Baltic Sea
- 2019
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- The growing grey seal (Halichoerus grypus) population in the Baltic Sea has created conflicts with local fisheries, comparable to similar emerging problems worldwide. Adequate information on the foraging habits is a requirement for responsible management of the seal population. We investigated the applicability of available dietary assessment methods by comparing morphological analysis and DNA metabarcoding of gut contents (short-term diet; n = 129/125 seals, respectively), and tissue chemical markers i.e. fatty acid (FA) profiles of blubber and stable isotopes (SIs) of liver and muscle (mid- or long-term diet; n = 108 seals for the FA and SI markers). The methods provided complementary information. Short-term methods indicated prey species and revealed dietary differences between age groups and areas but for limited time period. In the central Baltic, herring was the main prey, while in the Gulf of Finland percid and cyprinid species together comprised the largest part of the diet. Perch was also an important prey in the western Baltic Proper. The DNA analysis provided firm identification of many prey species, which were neglected or identified only at species group level by morphological analysis. Liver SIs distinguished spatial foraging patterns and identified potentially migrated individuals, whereas blubber FAs distinguished individuals frequently utilizing certain types of prey. Tissue chemical markers of adult males suggested specialized feeding to certain areas and prey, which suggest that these individuals are especially prone to cause economic losses for fisheries. We recommend combined analyses of gut contents and tissue chemical markers as dietary monitoring methodology of aquatic top predators to support an optimal ecosystem-based management.
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| 8. |
- Wahlberg, Magnus, et al.
(författare)
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A review of the literature on acoustic herding and attraction of fish : Visual ecology of fish - a review with special reference to percids : Reproduction biology of the viviparousblenny (Zoarces viviparus L.)
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A review of the literature on acoustic herding and attraction of fishA literature study of fishing methods using acoustic herding, passive acoustic steering and acoustic attraction is presented. All three techniques are used world-wide in traditional fishing, but their applications to modern fisheries are very few. Optimization in terms of selectivity and increase in catches seems promising for acoustic attraction, and many successful trials have been carried out on various fish species of different hearing abilities. The results from acoustic herding are more negative and a more thorough knowledge of fish behaviour is needed before such techniques can be improved. When examining passive acoustic steering, little evidence has been found that fish actually use acoustic cues to detect fishing gear. Theoretical calculations show that claims that fish can detect the Aeolean tones generated by the water flowing through the net can probably be discounted, but measurements of the acoustic field around the fishinggear have to be made to finally confirm this. However, it has been shown that the fishinggear leading structures currently used are far from optimal. Studies of the sensory basis of gear detection by fish are needed to improve such structures. Psychoacoustic studies have shown that fish are essentially sensitive to very low frequency sounds. Therefore, improving acoustic fishing techniques demands an efficient, low-frequency sound source. It is shown that the fishing boat itself can be modified to become a relatively efficient transducer at the desired frequencies.
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