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  • 1.
    Amcoff, Mirjam
    et al.
    Uppsala universitet, Zooekologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Does female feeding motivation affect the response to a food-mimicking male ornament in the swordtail characin Corynopoma riisei?2013In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 83, no 2, p. 343-354Article in journal (Refereed)
    Abstract [en]

    Female response to various aspects of male trait morphology and the effect of female feeding motivation were investigated in the swordtail characin Corynopoma riisei, a species where males are equipped with a flag-like food-mimicking ornament that grows from the operculum. Unfed females responded more strongly to the male ornament and showed a stronger preference for larger ornaments than did fed females. Females were shown not to discriminate between artificial male ornaments of either undamaged or damaged shape.

  • 2.
    Bergendahl, I. Ahlbeck
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Holliland, Per Benjamin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Karlöf, Oliver
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Feeding range of age 1+year Eurasian perch Perca fluviatilis in the Baltic Sea2017In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 90, no 5, p. 2060-2072Article in journal (Refereed)
    Abstract [en]

    Using the widespread Eurasian perch Perca fluviatilis as a model organism, feeding ranges were investigated using stable-isotope ratios (N-15 and C-13) and body condition. Differences were found between closely located sampling sites in a littoral area without obvious migration barriers, indicating that individual fish had small feeding ranges. Body condition differences between sampled stations were consistent over 4 years. Such sedentary behaviour is important to consider in, e.g. fisheries management and environmental monitoring, as local catch regulations may be meaningful or geographic stability in sampling locations may reduce noise in data.

  • 3. Beveridge, M. C. M.
    et al.
    Thilsted, S. H.
    Phillips, M. J.
    Metian, Marc
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Troell, Max
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. The Beijer Institute of Ecological Economics, Sweden.
    Hall, S. J.
    Meeting the food and nutrition needs of the poor: the role of fish and the opportunities and challenges emerging from the rise of aquaculture2013In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 83, no 4, p. 1067-1084Article in journal (Refereed)
    Abstract [en]

    People who are food and nutrition insecure largely reside in Asia and Sub-Saharan Africa and for many, fish represents a rich source of protein, micronutrients and essential fatty acids. The contribution of fish to household food and nutrition security depends upon availability, access and cultural and personal preferences. Access is largely determined by location, seasonality and price but at the individual level it also depends upon a person's physiological and health status and how fish is prepared, cooked and shared among household members. The sustained and rapid expansion of aquaculture over the past 30years has resulted in >40% of all fish now consumed being derived from farming. While aquaculture produce increasingly features in the diets of many Asians, it is much less apparent among those living in Sub-Saharan Africa. Here, per capita fish consumption has grown little and despite the apparently strong markets and adequate biophysical conditions, aquaculture has yet to develop. The contribution of aquaculture to food and nutrition security is not only just an issue of where aquaculture occurs but also of what is being produced and how and whether the produce is as accessible as that from capture fisheries. The range of fish species produced by an increasingly globalized aquaculture industry differs from that derived from capture fisheries. Farmed fishes are also different in terms of their nutrient content, a result of the species being grown and of rearing methods. Farmed fish price affects access by poor consumers while the size at which fish is harvested influences both access and use. This paper explores these issues with particular reference to Asia and Africa and the technical and policy innovations needed to ensure that fish farming is able to fulfil its potential to meet the global population's food and nutrition needs.

  • 4.
    Charlier, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Palmé, Anna
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Laikre, Linda
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Andersson, Jens
    Ryman, Nils
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Census (NC) and genetically effective (Ne) population size in a lake-resident population of brown trout Salmo trutta2011In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 79, no 7, p. 2074-2082Article in journal (Refereed)
    Abstract [en]

    Census (NC) and effective population size (Ne) were estimated for a lake-resident population of brown trout Salmo trutta as 576 and 63, respectively. The point estimate of the ratio of effective to census population size (Ne:NC) for this population is 0·11 with a range of 0·06–0·26, suggesting that Ne:NC ratio for lake-resident populations agree more with estimates for fishes with anadromous life histories than the small ratios observed in many marine fishes

  • 5. Clevestam, P. D.
    et al.
    Ogonowski, Martin
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Sjöberg, N. B.
    Wickström, H.
    Too short to spawn?: Implications of small body size and swimming distance on successful migration and maturation of the European eel Anguilla anguilla2011In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 78, no 4, p. 1073-1089Article in journal (Refereed)
    Abstract [en]

    Individual net fat reserves after migration and reproductive investments were calculated for migrating female silver eels Anguilla anguilla (n = 387) collected in the outlet region of the Baltic Sea during the autumn run. It is estimated that 20 center dot 4% of the A. anguilla had completely exhausted all initial fat reserves and that 45 center dot 0% of A. anguilla were within 90% of complete energy depletion after migration and reproduction. This study concludes that a combination of body size and distance (6900 km) to the spawning area in the Sargasso Sea explains the results. An increase in the costs of migration due to heavy infection with Anguillicoloides crassus was also evaluated in an additional scenario with results showing that 26 center dot 4% of the A. anguilla had completely depleted all fat reserves. It is hypothesized that a large proportion of female silver A. anguilla from the Baltic Sea catchment area will have inadequate or suboptimal reserves for successful migration and reproduction.

  • 6.
    Hedberg, Per
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Rybak, Fanny F.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Jiddawi, Narriman S.
    Winder, Monika
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Fish larvae distribution among different habitats in coastal East Africa2019In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 94, no 1, p. 29-39Article in journal (Refereed)
    Abstract [en]

    Fish larvae abundances, diversity and trophic position across shallow seagrass, coral reef and open water habitats were examined to characterize their distribution in coastal East Africa. Larvae were identified to family and analysed for abundance differences between sites and habitats, trophic level using stable-isotope analysis and parental spawning mode. Abundances differed greatly between sites with the highest numbers of larvae occurring in the open-water and seagrass habitats. Larval fish diversity was high across habitats with 51 families identified with small differences between sites and among habitats. Notably, larvae of abundant large herbivorous fishes present in reef and seagrass habitats were almost completely absent at all sampling locations. In the seagrass, demersal spawned larvae were more abundant compared with the reef and open-water habitats. Stable-isotope analysis revealed that fish larvae have a varied diet, occupying trophic level two to three and utilizing planktonic prey. This study offers new insights into distributional aspects of fish larvae along the East African coast where such information is sparse.

  • 7. Jensen, O. P.
    et al.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Didrikas, T.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Stockwell, J. D.
    Hrabik, T. R.
    Axenrot, T.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Kitchell, J. F.
    Foraging, bioenergetic and predation constraints on diel vertical migration: field observations and modelling of reverse migration by young-of-the-year herring Clupea harengus2011In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 78, no 2, p. 449-465Article in journal (Refereed)
    Abstract [en]

    Diel vertical migration (DVM) of young-of-the-year (YOY) herring Clupea harengus and one of their major predators, pikeperch Sander lucioperca, was examined using bottom-mounted hydroacoustics in Himmerfjarden, a brackish bay of the Baltic Sea, in summer. In contrast to previous studies on DVM of C. harengus aggregated across size and age classes, YOY C. harengus showed a reverse DVM trajectory, deeper at night and, on average, shallower during the day. This pattern was observed consistently on five acoustic sampling occasions in 3 years and was corroborated by two out of three trawl surveys. Large acoustic targets (target strength >-33 dB, probably piscivorous S. lucioperca > 45 cm) showed a classic DVM trajectory, shallow at night and deeper during the day. Variability in YOY C. harengus vertical distribution peaked at dawn and dusk, and their vertical distribution at midday was distinctly bimodal. This reverse DVM pattern was consistent with bioenergetic model predictions for YOY C. harengus which have rapid gut evacuation rates and do not feed at night. Reverse DVM also resulted in low spatial overlap with predators.

  • 8.
    Kolm, Niclas
    et al.
    Uppsala universitet, Zooekologi.
    Ahnesjö, Ingrid
    Uppsala universitet, Zooekologi.
    Do egg size and parental care coevolve in fish?2005In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 66, no 6, p. 1499-1515Article in journal (Refereed)
    Abstract [en]

    A phenomenon that has attracted a substantial theoretical and empirical interest is the positive relationship between egg size and the extent of parental care in fishes. Interestingly, despite the effort put into solving the causality behind this relationship over the past two decades it remains largely unsolved. Moreover, how general the positive relationship between egg size and parental care is among fishes is also poorly understood. In order to stimulate research exploring egg size and parental care variation in fishes, the potential selective forces from both natural and sexual selection on egg size and parental care are discussed. Recent empirical findings on how oxygen requirements and developmental times may differ between differently sized eggs are incorporated into a critical view of the current theory of this field. Furthermore, it is suggested that the up to now neglected effects of sexual selection, through both mate choice and sexual conflict, can have strong effects on the relationship between egg size and parental care in fishes. In light of the recent developments of comparative and experimental methods, future approaches that may improve the understanding of the relationship between egg size and care in fishes are suggested.

  • 9.
    Kolm, Niclas
    et al.
    Uppsala universitet, Zooekologi.
    Olsson, Jens
    Uppsala universitet, Limnologi.
    Differential investment in the Banggai cardinalfish: can females adjust egg size close to egg maturation to match the attractiveness of a new partner?2003In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 63, no S1, p. 144-151Article in journal (Refereed)
    Abstract [en]

    To test whether females can change their egg investment according to the different attractiveness ( i.e. size as measured by standard length, Ls) of a new mate after eggs have already matured in response to an earlier mate, female Banggai cardinalfish Pterapogon kauderni were first allowed to produce eggs for small (unattractive) or large (attractive) males. Then, when spawning was initiated, but prior to actual spawning, their partner was switched to either a significantly larger or a significantly smaller partner, respectively. A strong positive correlation between egg size and days until spawning with the second male was found for the females initially paired to a small and then a large male. Within a few days, these females apparently increased their egg size to match the attractiveness of their new male. No correlation between days until spawning and egg size in females initially paired to a large and then a small male, however was found, so apparently females were unable to adjust egg size in response to a decrease in mate attractiveness. Consequently, it is suggested that females can increase their egg size investment even after the onset of egg maturation and that this change can be quite rapid.

  • 10.
    Kotrschal, Alexander
    et al.
    Uppsala universitet, Zooekologi.
    Sundström, L. Fredrik
    Brelin, D.
    Devlin, R. H.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Inside the heads of David and Goliath: environmental effects on brain morphology among wild and growth-enhanced coho salmon Oncorhynchus kisutch2012In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 81, no 3, p. 987-1002Article in journal (Refereed)
    Abstract [en]

    Transgenic and wild-type individual coho salmon Oncorhynchus kisutch were reared in hatchery and near-natural stream conditions and their brain and structure sizes were determined. Animals reared in the hatchery grew larger and developed larger brains, both absolutely and when controlling for body size. In both environments, transgenics developed relatively smaller brains than wild types. Further, the volume of the optic tectum of both genotypes was larger in the hatchery animals and the cerebellum of transgenics was smaller when reared in near-natural streams. Finally, wild types developed a markedly smaller telencephalon under hatchery conditions. It is concluded that, apart from the environment, genetic factors that modulate somatic growth rate also have a strong influence on brain size and structure.

  • 11.
    Kvarnemo, C.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Mobley, K. B.
    Partridge, C.
    Jones, A. G.
    Ahnesjo, I.
    Evidence of paternal nutrient provisioning to embryos in broad-nosed pipefish Syngnathus typhle2011In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 78, no 6, p. 1725-1737Article in journal (Refereed)
    Abstract [en]

    In two experiments, radioactively labelled nutrients (either (3)H-labelled amino-acid mixture or (14)C-labelled glucose) were tube-fed to brooding male Syngnathus typhle. Both nutrients were taken up by the males and radioactivity generally increased in the brood pouch tissue with time. Furthermore, a low but significant increase of (3)H-labelled amino acids in embryos was found over the experimental interval (48 h), whereas in the (14)C-glucose experiment the radioactivity was taken up by the embryos but did not increase over the experimental time (320 min). Uptake of radioisotopes per embryo did not differ with embryo size. A higher uptake mg(-1) tissue of both (3)H-labelled amino acids and (14)C-labelled glucose was found in smaller embryos, possibly due to a higher relative metabolic rate or to a higher surface-area-to-volume ratio compared to larger embryos. Uptake in embryos was not influenced by male size, embryonic developmental advancement or position in the brood pouch. It is concluded that brooding males provide amino acids, and probably also glucose, to the developing embryos in the brood pouch. (C) 2011 The Authors Journal of Fish Biology (C) 2011 The Fisheries Society of the British Isles

  • 12.
    Kvarnemo, C.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Svensson, O.
    Stockholm University, Faculty of Science, Department of Zoology.
    Manson, W.
    Investment in testes, sperm-duct glands and lipid reserves differs between male morphs but not between early and late breeding season in Pomatoschistus minutus2010In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 76, no 7, p. 1609-1625Article in journal (Refereed)
    Abstract [en]

    This study of the sand goby Pomatoschistus minutus, a nest-holding fish with paternal care, focused on gonadal investment among males of different sizes collected early and late in the breeding season. All males caught at the nest had breeding colour, whereas trawl-caught fish consisted of males both with and without colour. The absence or presence of breeding colour was a good predictor of testes investment. Compared to males with breeding colour, males without colour were smaller in body size but had extraordinarily large testes. In absolute terms, testes mass of males without breeding colour was on average 3.4 times greater than those of males with breeding colour. Since small colourless males are known to reproduce as sneaker males, this heavy investment in testes probably reflects that they are forced to spawn under sperm competition. Contrary to testes size, sperm-duct glands were largest among males with breeding colour. These glands produce mucins used for making sperm-containing mucous trails that males place in the nest before and during spawning. Since both sneakers and nest-holders potentially could benefit from having large glands, this result is intriguing. Yet, high mucus production may be more important for nest-holders, because it also protects developing embryos from infections. There was no significant effect of season on body size, testes or sperm-duct glands size, but colourless males tended to be less common late in the season. Possibly this may indicate that individual small colourless males develop into their more colourful counterparts within the breeding season.

  • 13. Meager, J. J.
    et al.
    Rodewald, P.
    Domenici, P.
    Ferno, A.
    Järvi, Torbjörn
    Stockholm University, Faculty of Science, Department of Zoology.
    Skjaeraasen, J. E.
    Sverdrup, G. K.
    Behavioural responses of hatchery-reared and wild cod Gadus morhua to mechano-acoustic predator signals2011In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 78, no 5, p. 1437-1450Article in journal (Refereed)
    Abstract [en]

    The behavioural responses of wild (predator-experienced) and hatchery-reared (predator-naive) cod Gadus morhua to standardized mechano-acoustic (MA) stimuli were compared in the laboratory. Wild fish responded mainly with freezing and fast-start escapes away from the stimulus, whereas hatchery-reared fish often ignored or approached the stimulus. Wild fish also had stronger responses, turning faster during escapes and reducing activity immediately after the stimulus. Both fish types were less active on a 'risky' bare substratum after the stimulus. The antipredator responses of wild fish were consistent to repeated stimuli, whereas hatchery-reared fish that had generally only encountered harmless stimuli showed more variable responses with lower repeatability. This suggests that experience plays a role in shaping the behavioural response of fishes to MA stimuli.

  • 14. Miller, Jessica S.
    et al.
    Bose, Aneesh P. H.
    Fitzpatrick, John L.
    Stockholm University, Faculty of Science, Department of Zoology.
    Balshine, Sigal
    Sperm maturation and male tactic-specific differences in ejaculates in the plainfin midshipman fish Porichthys notatus2019In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 94, no 3, p. 434-445Article in journal (Refereed)
    Abstract [en]

    Using the plainfin midshipman fish Porichthys notatus, a species with alternative reproductive tactics (ARTs), we investigated how sperm maturation shapes sperm competitive abilities. We compared sperm performance and morphology before and after final sperm maturation by sampling sperm from the testes and stripped ejaculates of guarders and sneakers. In accordance with sperm competition risk theory, ejaculates from sneaker males had three times as much sperm as ejaculates from guarder males and sneaker males produced faster swimming sperm than guarder males, but this was only the case after final sperm maturation had occurred. Additionally, fully mature sperm found in ejaculates had larger heads and midpieces than sperm found in the testes. These results emphasize the important role played by non-sperm components of an ejaculate in mediating sperm performance and potentially also morphology.

  • 15. Obregón, C.
    et al.
    Lyndon, A. R.
    Barker, J.
    Christiansen, H.
    Godley, B. J.
    Kurland, Sara
    Stockholm University, Faculty of Science, Department of Zoology.
    Piccolo, J. J.
    Potts, R.
    Short, R.
    Tebb, A.
    Mariani, S.
    Valuing and understanding fish populations in the Anthropocene: key questions to address2018In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 92, no 3, p. 828-845Article in journal (Refereed)
    Abstract [en]

    Research on the values of fish populations and fisheries has primarily focused on bio-economic aspects; a more nuanced and multidimensional perspective is mostly neglected. Although a range of social aspects is increasingly being considered in fisheries research, there is still no clear understanding as to how to include these additional values within management policies nor is there a cogent appreciation of the major knowledge gaps that should be tackled by future research. This paper results from a workshop held during the 50th anniversary symposium of the Fisheries Society of the British Isles at the University of Exeter, UK, in July 2017. Here, we aim to highlight the current knowledge gaps on the values of fish populations and fisheries thus directing future research. To this end, we present eight questions that are deeply relevant to understanding the values of fish populations and fisheries. These can be applied to all habitats and fisheries, including freshwater, estuarine and marine.

  • 16.
    Olsson, Jens
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Mo, K.
    Florin, A. B.
    Aho, T.
    Ryman, Nils
    Stockholm University, Faculty of Science, Department of Zoology.
    Genetic population structure of perch Perca fluviatilis along the Swedish coast of the Baltic Sea2011In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 79, no 1, p. 122-137Article in journal (Refereed)
    Abstract [en]

    In this study, the genetic variation of perch Perca fluviatilis from 18 different sites along the Swedish coast of the Baltic Sea was assessed. There was a relative strong support for isolation by distance and the results suggest an overall departure from panmixia. The level of genetic divergence was moderate (global FST = 0·04) and indications of differences in the population genetic structure between the two major basins (central Baltic Sea and Gulf of Bothnia) in the Baltic Sea were found. There was a higher level of differentiation in the central Baltic Sea compared to the Gulf of Bothnia, and the results suggest that stretches of deep water might act as barriers to gene flow in the species. On the basis of the estimation of genetic patch size, the results corroborate previous mark–recapture studies and suggest that this is a species suitable for local management. In all, the findings of this study emphasize the importance of considering regional differences even when strong isolation by distance characterize the genetic population structure of species.

  • 17. Petersson, E.
    et al.
    Järvi, Torbjörn
    Stockholm University, Faculty of Science, Department of Zoology.
    Characteristics of brown trout males influence growth and survival of their offspring2007In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 71, no 2, p. 493-509Article in journal (Refereed)
    Abstract [en]

    Half-sib groups of juvenile brown trout Salmo trutta (0+ years) having fathers with different characteristics were compared in several respects. Two kinds of experiments were performed, aquarium observations in the laboratory and stocking in a semi-natural stream. It was found in the aquarium experiments that the offspring of fathers with larger adipose fins were more active and were probably better at defending territories. Offspring of males chosen by females had higher growth rate. The feeding rate was higher in juveniles having a less aggressive father or a father that was chosen by the mother. The stream experiments showed that offspring of dominant males had higher growth rates, and that offspring of less aggressive fathers had higher survival. Thus, characteristics of the males (fathers) influences the quality of the offspring, and there seem to be benefits for the females both to choose among potential mates and to spawn with the most dominant male. As these male characteristics are never regarded during the process of artificial breeding in hatcheries, the results indicate a basis for divergence between hatchery and wild populations.

  • 18.
    Roufidou, Chrysoula
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Borg, Bertil
    Stockholm University, Faculty of Science, Department of Zoology.
    Ovarian fluid in the three-spined stickleback Gasterosteus aculeatus: effects of egg overripening and sex steroid treatment2019In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 94, no 3, p. 446-457Article in journal (Refereed)
    Abstract [en]

    The ovarian fluid properties of the three-spined stickleback Gasterosteus aculeatus were studied in overripe and non-overripe ovulated female sticklebacks and in females that were implanted with Silastic capsules containing testosterone (T), oestradiol (E2), 17,20-dihydroxypregn-4-en-3-one (17,20-P) or progesterone (P4) into the abdominal cavity. Overripe females had less ovarian fluid than non-overripe females, but with higher dry mass, higher protein concentration and lower viscosity. T and 17,20-P increased the amount of ovarian fluid and the fluid protein concentration was increased by 17,20-P. 1-D sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that ovarian fluid contains several proteins, with high individual variability but with no consistent differences between groups. Some of the ovarian fluid proteins appeared to correspond to proteins from the eggs. The results suggest that secretion of ovarian fluid may be influenced by steroid hormones and that changes in its properties are related to the overripening of ovulated eggs. In at least some respects it appears that the changes in the ovarian fluid is a result, rather than the cause of overripening.

  • 19.
    Rowiński, Piotr K.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Uppsala University, Sweden.
    Mateos-Gonzalez, F.
    Sandblom, E.
    Jutfelt, F.
    Ekström, A.
    Sundström, L. F.
    Warming alters the body shape of European perch Perca fluviatilis2015In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 87, no 5, p. 1234-1247Article in journal (Refereed)
    Abstract [en]

    The consequences of elevated temperature on body shape were investigated by comparing European perch Perca fluviatilis from the Forsmark area of the Baltic Sea to P. fluviatilis from a nearby Biotest enclosure. The Biotest is a man-made enclosure within the Baltic Sea that has received warm water from a nuclear power plant since 1980, resulting in temperatures that are elevated 5-10 degrees C relative to the surrounding Baltic Sea. Sampled fish ranged from young-of-the-year to 14years. Geometric morphometrics and multivariate statistical analysis revealed significant morphological differences between individuals of P. fluviatilis from these two habitats. Most importantly, relative shape changed with size, with small individuals of P. fluviatilis from Biotest being characterized by a deeper body shape and a larger caudal peduncle than the smaller Baltic individuals. In large specimens, smaller differences were found with Biotest individuals being more slender than Baltic individuals. These results show that, in order to have a full understanding of the biological effects of elevated temperatures, studies that cover the entire size range of organisms will be important. Apart from the direct influence of temperature on growth rate and body shape, other ecological factors affected by temperature are discussed as possible contributors to the observed differences between the two populations.

  • 20.
    Sjöberg, N. B.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Petersson, E.
    Uppsala Univ, Dept Zool.
    Wickström, H.
    Swedish Board Fisheries.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Effects of the swimbladder parasite Anguillicola crassus on the migration of European silver eels Anguilla anguilla in the Baltic Sea2009In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 74, p. 2158-2170Article in journal (Refereed)
    Abstract [en]

    In a mark-recapture study in 2006, migrating European Anguilla anguilla silver eels were caught, tagged and released in the Baltic Sea and recaptures in commercial pound nets examined for possible effects on migration of infection with the swimbladder parasite Anguillicola crassus. The overall recapture rate was 36%. The prevalence of infection was lowest at the northernmost sampling site. There were no significant differences between infected and uninfected A. anguilla in condition indices, body fat content and estimated migration speeds. Parasite infection intensity levels were significantly negatively correlated with times and distances covered between release and recapture, but did not correlate with migration speed. It appears that more heavily infected A. anguilla were relatively more vulnerable to recapture in pound nets. It is hypothesized that parasite-induced damage to the swimbladder inhibited vertical migrations and infected A. anguilla tended to migrate in shallower coastal waters, relatively close to the shore.

  • 21.
    Sjöberg, Niklas B.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology. Swedish Board of Fisheries, Institute of Freshwater Research, Sweden.
    Petersson, Erik
    Wickström, Håkan
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Effects of the swimbladder parasite Anguillicola crassus on the migration of European silver eels Anguilla anguilla in the Baltic Sea2009In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 74, no 9, p. 2158-2170Article in journal (Refereed)
    Abstract [en]

    In a mark–recapture study in 2006, migrating European Anguilla anguilla silver eels were caught,tagged and released in the Baltic Sea and recaptures in commercial pound nets examined for possibleeffects on migration of infection with the swimbladder parasite Anguillicola crassus. The overallrecapture rate was 36%. The prevalence of infection was lowest at the northernmost sampling site.There were no significant differences between infected and uninfected A. anguilla in conditionindices, body fat content and estimated migration speeds. Parasite infection intensity levels weresignificantly negatively correlated with times and distances covered between release and recapture,but did not correlate with migration speed. It appears that more heavily infected A. anguilla wererelatively more vulnerable to recapture in pound nets. It is hypothesized that parasite-induced damageto the swimbladder inhibited vertical migrations and infected A. anguilla tended to migrate inshallower coastal waters, relatively close to the shore.

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