Early survival of marble trout Salmo marmoratus: evidence for density dependence? |
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| Authors: | S Vincenzi A J Crivellì D Jesensek J-F Rubin G A De Leo |
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| Institution: | Dipartimento di Scienze Ambientali, Universitàdegli Studi di Parma, Parma, Italy;, Station Biologique de la Tour du Valat, Le Sambuc, Arles, France;, Tolmin Angling Association, Most na Soci, Slovenia;, Ecole d'ingénieurs HES, Geneva, Switzerland |
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| Abstract: | Abstract – The role of endogenous and exogenous factors in regulating population dynamics of freshwater salmonids is still a matter of debate. The aim of the present work was to assess the relative importance of density-dependent and -independent factors in determining the survival of marble trout ( Salmo marmoratus ) yearlings in two populations living in Slovenian streams (Zakojska and Gorska). The investigation was performed by combining a classical life table analysis with Monte Carlo simulation. Size-dependent fecundity was estimated by stripping wild adults in the fish farm. A significant positive relationship was found between length of marble trout females and the number of eggs produced. Egg density was the major determinant of survival from eggs to age 1+ ( σ 0) in both streams. Residuals of the relationship between σ 0 and egg density were positively correlated with rainfall only in Zakojska, probably because, within a certain range, more intense rainfalls increases stream flow and, consequently, suitable habitat for trout. Our study shows how density-dependent and environmental factors can interact to determine the survival of marble trout during the first year of life. |
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| Keywords: | density-dependent survival marble trout Salmo marmoratus population dynamics endogenous versus exogenous factors |
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