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A model relating the results of low pH bioassay experiments to the fishery status of Norwegian lakes
Author(s) -
SADLER K.
Publication year - 1983
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 - 10.1111/j.1365-2427.1983.tb00004.x
Subject(s) - salmo , brown trout , bioassay , trout , norwegian , biology , fishery , ecology , environmental science , fish <actinopterygii> , linguistics , philosophy
SUMMARY. 1. Data from the literature concerning several Norwegian brown trout (Salmo trutta) populations are used to construct Leslie matrices in order to estimate their capacity to withstand egg and fry mortalities. These estimates are compared with the results of bioassay studies conducted at pH 4.5 and at various calcium concentrations in order to predict the percentage of trout populations which would be able to survive these conditions. 2. These predictions are in good agreement with the observed fishery status of Norwegian lakes at calcium concentrations <30 /μeq I −1 but above this concentration the recorded status is worse than predicted. 3. Likely causes for this difference are considered to be effects acting on fish older than those used in the bioassay experiments (either mortality or reduction in fecundity possibly due to impaired growth) or the effects of other water quality factors, for example aluminium. 4. These effects need only be fairly slow acting as compared with the egg and fry mortalities so far studied in detail. Thus the discrepancy between predicted and observed results at pH 4.5 and 50μeq 1‐ −1 calcium could be caused by an additional 80% mortality acting over the 4–8 year period before maturation. 5. An additional factor which could result in the observed fishery status being worse than predicted is temporal variation in water chemistry which is not assessed in the survey of Norwegian lakes. In particular, the adverse conditions occurring at time of snowmelt could be critically important.