Indicative Value of Anglers´ Records for Fish Assemblage Evaluation in a Reservoir (Case Study Brno Reservoir, Czech Republic)
Zdenĕk Adámek and Pavel Jurajda
Abstract.—Regularly administered and appropriately collected anglers´ records not only provide very important information about the particular fishing effort and stocking efficiency (rate of return), but may also be used for understanding fish growth, natural spawning success, and fish assemblage composition and its development. The data from anglers´ records are of particular importance in bigger reservoirs where the evaluation of fish assemblage structure, abundance, and biomass using routine fisheries sampling methods is quite difficult. Using data from the Brno Reservoir, we examined the utility of anglers´ records for the evaluation of fish assemblage composition and development with respect to water quality development. The deterioration of water quality in past decades was presented in considerably increasing ratio between nonpredatory and predatory fishes biomass in anglers´ catches. In 1991–2007, cyprinids prevailed in anglers´ catches. The mean annual angling effort in the Brno Reservoir was 55,063 ± 10,393 angling trips (man-day performance). The mean annual angling yield reported in anglers´ records amounted to 32,613 ± 7,411 kg (26,236 ± 7,428 fish individuals), which corresponds to an individual angling yield of 148 ± 34 kg/ha during the period mentioned above. Thus, the yearly angling yield from the Brno Reservoir de facto exploits the natural productivity of this type of reservoirs (250 m above sea level), which usually corresponds to 150–200 kg/ha.