Premium
The role of phosphorus release by roach [ Rutilus rutilus (L.)] in the water quality changes of a biomanipulated lake
Author(s) -
Tarvainen M.,
Sarvala J.,
Helminen H.
Publication year - 2002
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1046/j.1365-2427.2002.00992.x
Subject(s) - rutilus , biomanipulation , littoral zone , eutrophication , dreissena , phosphorus , perch , biomass (ecology) , cyprinidae , biology , benthic zone , zoology , water column , population , zooplankton , trophic state index , ecology , percidae , bioenergetics , nutrient , chemistry , fish <actinopterygii> , fishery , demography , organic chemistry , sociology , mollusca , bivalvia , mitochondrion , microbiology and biotechnology
SUMMARY 1. Following fish removal, the water quality in biomanipulated lakes often improves concomitant with decreased phosphorus (P) levels. Because the decrease in P concentrations derives most probably either directly or indirectly from fish, which are the main target of biomanipulation, this study examined the P release of 0+, 1+ and 2+ roach [ Rutilus rutilus (L.)] and changes in the P release during summer in a shallow eutrophic lake in Finland. 2. The P release was separated into P derived from benthic and littoral food items and into recycled P derived from feeding on zooplankton, to estimate the contribution of net P additions to the water column by the fish to the increase in P concentrations of the lake water (75–110 mg P m −3 ) in summer 1991–96. 3. Individual P release of roach by both egestion and excretion was estimated with a bioenergetics model. The size of the roach population was estimated with a depletion method and the proportions of different age groups from catch samples, using a programme separating mixtures of normal distributions. The sensitivity of the release estimates to variation in the growth data was estimated with the jackknife technique. 4. The biomass‐specific P release by 0+ roach (0.36–0.54 mg P g −1 day −1 ) was higher than that by older roach (0.07–0.16 mg P g −1 day −1 ) throughout the summer. The P release by the whole roach population deriving from benthic and littoral food items (0.7–2.7 mg m −3 during July to August, representing a net addition to the water column) was 5–19 times lower in 1991–96 than the recycled P release deriving from zooplankton (8.9–25.7 mg m −3 ), and too low to explain the increase in the P concentration of the lake water during the summer. Because the biomass‐specific P release and roach diet composition vary with fish age, it is important to consider the age structure of fish populations to obtain correct estimates of P release and net additions to the water column. 5. The removal of roach by fishing diminished the roach stock greatly, but the fish‐mediated P release to the water column changed little. This effect was because of the high compensation capacity of the roach population, leading to high recruitment of young fish with higher biomass‐specific P release rates. 6. External loading is very low during summer months and therefore it cannot explain the increase in the P concentration of water during that time. Internal loading from the sediment might be as high as 10.2 mg P m −2 day −1 , i.e. 50 times higher than the maximum net P addition by the total roach population.