Abstract
The length distributions of gillnet catches obtained by fishing on unexploited or slightly exploited Arctic charr, Salvelinus alpinus (L.), and brown trout, Salmo trutta L., populations are frequently bimodal. To test the hypothesis that these length distributions may not only be due to sampling bias, but also an effect of population structure, fleets of gillnets were used in sampling from allopatric populations of Arctic charr and brown trout, where the population numbers had been estimated by mark–recapture experiments. In both populations, the length distributions of the populations and the corresponding gillnet catches appeared as bimodal. The second mode of the length frequency distributions consisted of individuals from many age classes accumulated within a restricted length range, which is in turn a consequence of stagnation or low annual growth in old fish. Our results show that the gillnet catches by the use of fleets of gillnets described the overall bimodal length frequency distributions of the populations, although the fraction of larger fish may be significantly overestimated due to a strong increase in gillnet catchability by increasing fish size.
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References
Amundsen P-A (1989) Effects of intensive fishing on food consumption and growth of stunted arctic charr (Salvelinus alpinus L.) in Takvatn, northern Norway. Physiol Ecol Jan Spec 1:265–278
Amundsen P-A, Klemetsen A, Grotnes PE (1993) Rehabilitation of a stunted population of Arctic char by intensive fishing. North Am J Fish Manag 13:483–491
Amundsen P-A, Damsgård B, Arnesen AM, Jobling M, Jørgensen EH (1995) Experimental evidence of cannibalism and prey specialization in Arctic charr, Salvelinus alpinus. Environ Biol Fish 43:285–293
Borgstrøm R (1992) Effect of population density on gillnet catchability in four allopatric populations of brown trout (Salmo trutta). Can J Fish Aquat Sci 49:1539–1545
Borgstrøm R, Ebne I, Svenning M-A (2010) High lacustrine gillnet catchability of anadromous Arctic charr. Hydrobiologia 650:203–212
Borgstrøm R, Isdahl T, Svenning M-A (2014) Population structure, biomass, and diet of landlocked Arctic charr (Salvelinus alpinus) in a small, shallow High Arctic lake. Polar Biol. doi:10.1007/s00300-014-1587-6
Byström P (2006) Recruitment pulses induce cannibalistic giants in Arctic char. J Anim Ecol 75:434–444
Christensen JM (1964) Burning of otoliths, a technique for age determination of soles and other fish. J Cons Perm Int Explor Mer 26:73–81
Finstad AG, Berg OK (2004) Bimodal population size distributions and biased gillnet sampling. Can J Fish Aquat Sci 61:2151–2157
Finstad AG, Jansen PA, Langeland A (2000) Gillnet selectivity and size and age structure of an alpine Arctic char (Salvelinus alpinus) population. Can J Fish Aquat Sci 57:1718–1727
Finstad AG, Jansen PA, Hirvonen H (2003) Bimodal size distributions in Arctic char, Salvelinus alpinus: artefacts of biased sampling. Can J Fish Aquat Sci 60:1104–1110
Griffiths D (1994) The size structure of lacustrine Arctic charr (Pisces: Salmonidae) populations. Biol J Linn Soc 51:337–357
Hamley JM (1975) Review of gillnet selectivity. J Fish Res Board Can 32:1943–1969
Hamley JM (1980) Sampling with gillnets. In: Backiel T, Welcomme RL (eds) Guidelines for sampling fish in inland waters, EIFAC tech papers 33. FAO, Rome, pp 37–53
Hamley JM, Regier HA (1973) Direct estimation of gillnet selectivity to walleye (Stizostedion vitreum vitreum). J Fish Res Board Can 30:817–830
Hammar J (2000) Cannibals and parasites: conflicting regulators of bimodality in high latitude Arctic charr, Salvelinus alpinus. Oikos 88:33–47
Haraldstad Ø, Jonsson B (1983) Age and sex segregation in habitat utilization by brown trout in a Norwegian lake. Trans Am Fish Soc 112:27–37
Hart PJB, Pitcher TJ (1969) Field trials of fish marking using a jet inoculator. J Fish Biol 1:383–385
Hartigan JA, Hartigan PM (1985) The dip test of unimodality. Ann Stat 13:70–84
Jensen KW (1977) On the dynamics and exploitation of the population of brown trout, Salmo trutta L., in Lake Øvre Heimdalsvatn, southern Norway. Report Inst Freshw Res Drottningholm 56:18–69
Jensen JW, Hesthagen T (1996) Direct estimates of the selectivity of a multimesh and a series of single gillnets for brown trout. J Fish Biol 49:33–40
Jensen H, Kahilainen KK, Amundsen P-A, Gjelland KØ, Tuomaala A, Malinen T, Bøhn T (2008) Predation by brown trout (Salmo trutta) along a diversifying prey community gradient. Can J Fish Aquat Sci 65:1831–1841
Johnson L (1976) Ecology of arctic populations of lake trout, Salvelinus namaycush, lake whitefish, Coregonus clupeaformis, Arctic char, S. alpinus, and associated species in unexploited lakes of the Canadian Northwest Territories. J Fish Res Board Can 33:2459–2488
Klemetsen A, Grotnes PE, Holthe H, Kristoffersen K (1985) Bear Island charr. Report Inst Freshw Res Drottningholm 62:98–119
L’Abée-Lund JH, Langeland A, Sægrov H (1992) Piscivory by brown trout Salmo trutta L. and Arctic charr Salvelinus alpinus (L.) in Norwegian lakes. J Fish Biol 41:91–101
Langeland A, L’Abée-Lund JH, Jonsson B, Jonsson N (1991) Resource partitioning and niche shift in Arctic charr Salvelinus alpinus and brown trout Salmo trutta. J Anim Ecol 60:895–912
Nordeng H (1961) On the biology of char (Salmo alpinus L.) in Salangen, North Norway. I. Age and spawning frequency determined from scales and otoliths. Nytt Mag Zool 10:67–123
Parker HH, Johnson L (1991) Population structure, ecological segregation and reproduction in non-anadromous Arctic charr, Salvelinus alpinus (L), in four unexploited lakes in the Canadian high Arctic. J Fish Biol 38:123–147
Pitcher TJ, Kennedy GJA (1977) The longevity and quality of fin marks made with a jet inoculator. Fish Manag 8:16–18
Power G (1978) Fish population structure in arctic lakes. J Fish Res Board Can 35:53–59
R Core Team (2014) R: a language and environment for statistical computing. http://www.R-project.org. Accessed 14 Nov 2014
Ricker WE (1975) Computation and interpretation of biological statistics of fish populations. Bull Fish Res Board Can 191. Department of Environment Fisheries and Marine Service, Ottawa
Riget FF, Nygaard KH, Christensen B (1986) Population structure, ecological segregation, and reproduction in a population of Arctic char (Salvelinus alpinus) from Lake Tasersuag, Greenland. Can J Fish Aquat Sci 43:985–992
Riget F, Jeppesen E, Landkildehus F, Lauridsen TL, Geertz-Hansen P, Christoffersen K, Sparholt H (2000) Landlocked Arctic charr (Salvelinus alpinus) population structure and lake morphometry in Greenland—is there a connection? Polar Biol 23:550–558
Rudstam LG, Magnusson JJ, Tonn WM (1984) Size selectivity of passive fishing gears: a correction for encounter probability applied to gill nets. Can J Fish Aquat Sci 41:1252–1255
Sømme I (1941) Ørretboka. Jakob Dybwad Forlag, Oslo. (in Norwegian)
Sparholt H (1985) The population, survival, growth, reproduction and food of arctic charr, Salvelinus alpinus (L.), in four unexploited lakes in Greenland. J Fish Biol 26:313–330
Svalastog D (1991) A note on maximum age of brown trout, Salmo trutta L. J Fish Biol 38:967–968
Svärdson G (1976) Interspecific population dominance in fish communities of Scandinavian lakes. Report Inst Freshw Res Drottningholm 55:144–171
Svenning M-A (1993) Life history variations and polymorphism in Arctic charr, Salvelinus alpinus (L.) on Svalbard and in Northern Norway. Dr. scient. thesis. University of Tromsø, Tromsø
Svenning M-A, Borgstrøm R (1995) Population structure in landlocked Spitzbergen Arctic charr sustained by cannibalism? Nord J Freshw Res 71:424–431
Svenning M-A, Borgstrøm R (2005) Cannibalism in Arctic charr: do all individuals have the same propensity to be cannibals? J Fish Biol 66:957–965
Svenning M-A, Klemetsen A, Olsen T (2007) Habitat and food choice of Arctic charr in Linnévatn on Spitsbergen, Svalbard: the first year-round investigation in a High Arctic lake. Ecol Freshw Fish 16:70–77
Winters GH, Wheeler JP (1990) Direct and indirect estimation of gillnet selection curves of Atlantic herring (Clupea harengus harengus). Can J Fish Aquat Sci 47:460–470
Acknowledgments
We thank the Governor of Svalbard for transport to and from the island Danskøya. Jenny Stien is acknowledged for improving the English, and John Gunnar Dokk for his field assistance in Lake Skavatn. We are also grateful to Audun Stien for help with the statistics, and three unknown referees, as well as the editor, Dieter Piepenburger, for valuable corrections and suggestions concerning the manuscript.
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Borgstrøm, R., Haugen, M., Madsen, K.E. et al. Recorded bimodal length frequency distributions of Arctic charr, Salvelinus alpinus (L.), and brown trout, Salmo trutta L.: an effect of both population structure and sampling bias. Polar Biol 38, 895–903 (2015). https://doi.org/10.1007/s00300-015-1650-y
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DOI: https://doi.org/10.1007/s00300-015-1650-y