Guidelines For Coastal Fish Monitoring

Fish are studied to an increasing extent in environmental monitoring around the coasts of Sweden, and the coastal fishery has a good potential for further development. Standardized techniques for long-term monitoring and predictions of the size and productive capacity of fish populations, as well as continuous control of their health in a wide context thus are required. This report describes a basic programme and guidelines designed to study coastal fish. The system also constitutes a basis for an integration of physiological health studies and measurements of contaminant levels with basic ecological data. Both population monitoring and collection of fish for analytical purposes are done by means of fishing using established methods -gill nets and fyke nets. A detailed description of the principles behind the systemis given by Neuman (1985). The monitoring and prognosis system is designed for coastal species. Such species mainly occur close to the bottom; the dominating pelagic fishes are mainly found further out to sea. In order to be able to link the reactions of the fish to the environmental situation in a specific study area, priority is given to stationary species, particularly with regard to measurements on the individual level. In addition, the system concentrates on relatively large species because they are often of commercial interest, they allow individual chemical and biological analyses and are easy to catch with established methods. The species monitored, i.e., demersal (bottom-living) fairly large fish, can begrouped into two communities on the coasts of the Baltic: littoral, mainly stationary warm-water species, and less stationary cold-water species living in deeper water. The most common fish in the former group are perch, roach and ruffe, whereas the latter mainly consists of flounder, cod, sculpins, viviparous blenny, and whitefish. At the Swedish West Coast, cold-water species such as cod, flatfish, viviparous blenny and sea scorpion dominate also in shallow water; eel is the only major representative of warm-water fishes. The design of the test fishing, as in all other monitoring of inter-year variations in biological processes, places strict demands on statistical planning. The methods described here have been developed through many years of pilot studies and statistical tests. By means of stratification as regards choice of species and size groups, depth intervals, stations and times of year, it has been possible to create statistica