Title: Fish health indices as a marker of surface water quality (229/2/A)
Author: A.P. Barnes
Author: I.D. Hirst
Document Type: Monograph
Abstract:
This report describes the findings of an epidemiological study assessing the effects of
differing water quality on the health of fish populations in freshwater river systems under the
jurisdiction of the National Rivers Authority. A variety of techniques for quantifying
and describing the health status of fish populations were used. Suitable target waters were
identified from existing NRA data using National Water Council scores, Biological
Monitoring Working Party scores and fisheries survey data. A total of 3613 fish
from 35 sites were examined in the field for the presence of a number of easily recognisable
external disease characteristics. In addition a sub sample of 231 fish were examined in the
laboratory to assess several physiological, immunological and biochemical parameters.
The overall external disease prevalence was found to be 8.2 per cent. Using a generalised linear
model able to cope with binomial responses, there was no compelling evidence that
prevalence rates differed with respect to river quality data at polluted and reference sites or
with month sampled. In each case NWC class 1 rivers provided the lowest prevalence rates
for each external abnormality, however, these sites were not statistically separable from other
NWC 2 and 3 rivers. One variable was, however, found to be associated with prevalence
rates (at the 7 per cent level of significance) and was included in a statistical model. However, the
predictions of the model were considered to be close to the thresholds of detectability in an
epidemiological study. In laboratory based studies, for the majority of 12 variables examined,
differences between sites were greater than the variation between individual fish. Using oneway
analysis of variance 3 parameters differed significantly (at the 5 per cent level of significance)
with different river water qualities. Of the 52 possible bivariate correlations between the 12
laboratory variables and 4 river quality variables, 2 indicated a possible cause and effect
relationship and would warrant further investigation.
This study highlights the need to examine a suite of variables in assessing the overall health
status of fish populations. Recommendations for an integrated approach to disease studies are
discussed.
Publisher: National Rivers Authority
Publication Date: 1994
Publication Place: Bristol
Subject Keywords: Water quality; Fishes; Fish diseases; Roach; Morbidity; Symptoms; Pollutants
Extent: 82
Permalink: http://www.environmentdata.org/archive/ealit:3962
Total file downloads: 23
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