Does harvest of the European grayling, Thymallus thymallus (Actinopterygii: Salmoniformes: Salmonidae), change over time with different intensity of fish stocking and fishing effort?

Abstract

Background. The European grayling, Thymallus thymallus (Linnaeus, 1758), is a fish species of high value in recreational fishing. The monitoring of changes in grayling populations is a high priority in fisheries. Data on the harvest of recreational anglers can potentially serve as an easy and inexpensive way to monitor changes in fish populations. This study aimed to assess spatio-temporal trends in catches of grayling in a larger geographical area. Materials and methods. This study analysed harvest rates of grayling by recreational anglers on 241 fishing grounds, in the Czech Republic, within 1986-2015 (30 years). Data from individual angling logbooks were used. The data were collected by individual anglers and processed by the Czech Fishing Union (Český rybářský svaz). Results. Over the period of 30 years, Czech anglers harvested a total of 9 928 grayling specimens weighing altogether 3 357 kg. Within the period surveyed, both parameters (the grayling biomass harvested and the representation of grayling in overall fish harvest) decreased to 10% of the initial values. The percentage of fishing grounds with a harvest of grayling decreased to 30% of the initial values. Harvest per effort decreased to 20% of the initial values over 11 years. There was only a weak correlation between fish stocking and fish harvest. There was a negative relation between the number of angler fishing visits with both catch (fish number) and yield (biomass) of grayling. The harvest was positively correlated with fishing effort. The mean size of harvested grayling remained constant (~0.35 kg) over 30 years. Conclusion. Harvest of grayling significantly declined over the last three decades, implying that increased effort in conservation of grayling is necessary. Future studies should focus on monitoring of the remaining selfreproducing grayling populations.

Harvest Rates of Rheophilic Fish Vimba vimba, Chondrostoma nasus, and Barbus barbus Have a Strong Relationship with Restocking Rates and Harvest Rates of Their Predator Silurus glanis in Lowland Mesotrophic Rivers in Central Europe

“…The angling effort strongly affected the harvest rates of the rheophilic fishes. Previous studies also agreed that the harvest rates of fish are driven by the angling effort [33,35,45,46]. The angling effort is relatively hard to estimate because each angler fishes at a different intensity.…”

“…Bonferroni correction was applied in all three models because multiple groups were tested for differences. This method of fisheries data analysis was previously used to analyze fish harvest rates in different research papers [32][33][34][35].…”

Fisheries Volume 48 Number 5 May 2023

“…The fi shing sites on rivers cover a total area of 38,000 ha, while the fi shing sites on streams cover an area of 3,700 ha. They are located mostly in lowlands (200-600 m above sea level), have mesotrophic or eutrophic nutrient levels, and have a fi sh biomass of 150-300 kg/ha (Lyach and Remr 2020 ). Lake waters are dominated by cyprinid species, mainly Roach Rutilus rutilus , Bleak Alburnus alburnus , and European Chub Squalius cephalus .…”

Fisheries and Aquaculture in the Czech Republic: History, Current Status, Management, and Regulations

“…The fishing sites on rivers cover a total area of 38,000 ha, while the fishing sites on streams cover an area of 3,700 ha. They are located mostly in lowlands (200–600 m above sea level), have mesotrophic or eutrophic nutrient levels, and have a fish biomass of 150–300 kg/ha (Lyach and Remr 2020). Lake waters are dominated by cyprinid species, mainly Roach Rutilus rutilus , Bleak Alburnus alburnus , and European Chub Squalius cephalus (Lyach et al 2018).…”

“…Almost every aspect of fisheries has started turning from the full‐production idea to a more sustainable and ecosystem‐friendly approach. Recreational fisheries management has turned its focus toward the conservation of fish populations, as fishing regulations are getting stricter every year (e.g., minimum legal angling sizes are increasing and closed seasons are becoming more prolonged; Lyach and Remr 2019b, 2020; Lyach 2020a). Management is focusing on decreased harvest of native fishes and reduced stocking of nonnative fishes, with the goal of making recreational fisheries more sustainable.…”