Three Decades of Swedish Experience Demonstrates the Need for Integrated Long-Term Monitoring of Fish in Marine Coastal Areas

Abstract

The first attempts to monitor coastal fish in Sweden were made in the 1960s and 1970s. Ecological, physiological, biochemical and environmental chemistry data were collected in separate projects. When the National Marine Monitoring Programme was revised in 1992, a new strategy was introduced for assessments of long-term trends in coastal fish communities. Annual integrated monitoring of contaminants, biomarkers and population and community indicators of ecosystem health was started in selected areas using common sentinel species. Data from one monitoring area at the coast of the Baltic proper are analyzed in this paper. The results have shown a shift in fish community structure indicating changes in ecosystem productivity. Trends have been detected in growth rate (positive) and relative gonad size (negative) in perch (Perca fluviatilis), suggesting a metabolic disturbance according to the predictive response model developed for interpretations. One factor which may have contributed to the reduced GSI was a decrease in mean age of sampled fish during the period of study. Chemical exposure was indicated by a 3-fold increase of EROD activity during the monitored 15-year period. However, concentrations of most measured contaminants in perch have decreased during the same period. The experience of the integrated approach has shown that a tentative analysis of cause and environmental significance could be made, improving the assessment, but there still remain unsolved questions to be answered in follow-up studies. The analysis has also shown the importance of long-term monitoring at several levels of biological organization to distinguish between natural variation and low-level effects on ecosystems.

Changes to Marine Trophic Networks Caused by Fishing

“…With the often unrestrained increase in fishing activity, some have sounded the alarm on the possible effects of this practice on populations and the world's marine ecosystems (Jackson et al, 2001;Lotze & Worm, 2009). Since fisheries have both direct and indirect effects on the ecosystem, wherein commercial and non-commercial species establish feeding interactions, it is very likely that impacts from human activities, which are exerted on individuals, propagate to populations and finally emerge at the community level (Sandström et al, 2005).…”

Evaluation of long‐term biomarker data from perch (Perca fluviatilis) in the Baltic sea suggests increasing exposure to environmental pollutants

“…When catches of all perch between three (3+) and six (6 +) years old are summarized, the same trend occurs [6]. Furthermore, the size of the perch at a certain age has increased because of increasing body growth rate [4].…”

Spatial and annual variation to define the normal range of biological endpoints: An example with biomarkers in perch

“…The number of sampled fish, size (weight and length), age, and water temperature at sampling are shown in Table 1. All reference sites except Missjö are included in the Swedish Environmental Monitoring Program [7][8][9]. All variables were measured in female perch, with the exception of Vtg, which was measured in both female and male perch.…”

“…However, sampling of multiple reference sites is costly and it would be beneficial to be able to use historical data to estimate the normal range of the biomarkers. In Sweden, biomarkers in perch are sampled annually at three reference areas along the Baltic coast [7]. This is performed within the Swedish Environmental Monitoring Program, which is financed by the Swedish Environmental Protection Agency.…”