Resource limitation during early ontogeny: constraints induced by growth capacity in larval and juvenile fish |
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Authors: | L Persson P Byström E Wahlström A Nijlunsing S Rosema |
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Institution: | Department of Ecology and Environmental Science, Ume? University, S-90187 Ume?, Sweden e-mail: lennart.persson@eg.umu.se Tel.: +46-90-7866316, Fax: +46-90-7867665, SE
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Abstract: | The presence of and mechanisms behind density-dependent growth and resource limitation in larval and juvenile stages of organisms
with high mortality such as fish are much debated. We compare observed consumption and growth rates with maximum consumption
and growth rates to study the extent of resource limitation in young-of-the-year (YOY) roach (Rutilus rutilus) and perch (Perca fluviatilis). Diet, habitat use, consumption rate and growth rate were measured under varying YOY fish densities over 2 years in four
lakes. In the first year, YOY roach and perch were studied under allopatric conditions. Experimental addition of perch roe
in the second year also allowed study of YOY of the two species under sympatric conditions in two of the lakes. The diet of
YOY roach was dominated by cladoceran zooplankton and YOY roach habitat use was restricted to the shore region in both years.
This restricted habitat use did not involve any cost in foraging gain in the first year as consumption and growth rates were
very close to maximum rates. During the second year, when the two species coexisted, resources were limited in late season,
more so in the littoral than in the pelagic habitat in one lake while the reverse was the case in the other lake. The diet
of YOY perch was also dominated by zooplankton, and with increasing perch size the proportion of macroinvertebrate prey in
the diet increased. After hatching, YOY perch first utilized the pelagic habitat restricting their habitat use to the shore
after 1 to several weeks in the pelagic zone. During the larval period, perch were not resource limited whereas juvenile perch
were resource limited in both years. The fact that YOY perch were more resource limited than YOY roach was related to the
higher handling capacity and lower attack rate of perch relative to roach, rendering perch more prone to resource limitation.
Estimates of resource limitation based on consumption rates and growth rates yielded similar results. This supports the adequacy
of our approach to measure resource limitation and suggests that this method is useful for studying resource limitation in
organisms with indeterminate growth. Our results support the view that density-dependent growth is rare in larval stages.
We suggest that density-dependent growth was absent because larval perch and roach were feeding at maximum levels over a wide
range of larvae densities.
Received: 14 June 1999 / Accepted: 29 October 1999 |
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Keywords: | Resource limitation Larvae and juvenile fish Attack rate Maximum consumption rate Maximum growth rate |
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