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Recruitment variability of resident brown trout in peripheral populations from southern Europe
Department of Environmental Sciences, University of Castilla-La Mancha, Toledo, Spain.
Department of Zoology, Complutense University of Madrid, Madrid, Spain.
Norwegian Institute for Nature Research, Oslo, Norway. (Naturresurs Rinnande Vatten)
Department of Zoology, Complutense University of Madrid, Madrid, Spain.ORCID-id: 0000-0002-6127-5302
2008 (engelsk)Inngår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 53, s. 2364-2374Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

1. Population regulation was studied for seven consecutive years (1992–98) in five rivers at

the periphery of the distribution of Salmo trutta, where the fish were living under

environmental constraints quite different from those of the main distribution area.

2. Recruitment is naturally highly variable and the populations had been earlier classified

as overexploited. Thus we expected that densities of young trout in most populations

would be too low for density-dependent mortality to operate. We tested this by fitting the

abundance of recruits to egg densities over seven consecutive years (stock–recruitment

relationship), and used the results to judge whether exploitation should be restricted in the

interests of conserving the populations.

3. The density of 0+ trout in early September, as well as the initial density of eggs and

parents, varied greatly among localities and years. The data for all populations fitted the

Ricker stock–recruitment model. The proportion of variance explained by the population

curves varied between 32% and 51%. However, in most cases the observations were in the

density-independent part of the stock–recruitment curve, where densities of the recruits

increased proportionally with egg densities.

4. Our findings suggest that recruitment densities in most rivers and years were below the

carrying capacity of the habitats. Although density-dependent mechanisms seemed to

regulate fish abundance in some cases, environmental factors and harvesting appeared

generally to preclude populations from reaching densities high enough for negative

feedbacks to operate. The findings thus lend support to Haldane’s (1956) second

hypothesis that changes in population density are primarily due to density-independent

factors in unfavourable areas and areas with low density due to exploitation. Exploitation

should be reduced to allow natural selection to operate more effectively.

sted, utgiver, år, opplag, sider
2008. Vol. 53, s. 2364-2374
Emneord [en]
density-dependence, fisheries management, marginal populations, population abundance
HSV kategori
Identifikatorer
URN: urn:nbn:se:kau:diva-34227DOI: 10.1111/j.1365-2427.2008.02056.xISI: 000260670100003OAI: oai:DiVA.org:kau-34227DiVA, id: diva2:753994
Tilgjengelig fra: 2014-10-09 Laget: 2014-10-09 Sist oppdatert: 2017-12-05bibliografisk kontrollert

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