Biology subjects

Putys, Z.

Publications and source records attributed to Putys, Z..

3 recordsLinked to original sources

bioRxiv2025

Disregarding fish ageing method can compromise growth parameter comparability across studies

Reliable and comparable growth estimates are critical for accurate comparative studies, robust stock assessments, and effective fisheries management. Many studies compare fish growth Von Bertalanffy parameters (growth coefficient K and asymptotic length L{infty}) across species, populations, or time periods. These parameters are often obtained from literature or FishBase without accounting for ageing method used to estimate size-at-age, despite known differences in age estimates from different structures. In this study, we use four species as a case study and once again demonstrate that fish ageing based on otoliths and scales can produce significantly different estimates of L{infty} and K. We then analyse available K and L{infty} records from FishBase and show that L{infty} values derived from scales were, on average, 15% higher than those obtained from otoliths, while K values were 20% smaller (p < 0.01 in both cases). We strongly recommend that ageing methods be clearly reported in all growth studies and included in databases, that comparative analyses explicitly account for ageing method in statistical model structure, and that researchers consider methodological differences when interpreting growth parameter variations across studies.

ecology↗

bioRxiv2022

Status and future perspectives for pikeperch (Sander lucioperca) stocks in Europe

Pikeperch (Sander lucioperca) is a European fresh and brackish water piscivorous fish, important as both a key predator and a valuable commercial and recreational fisheries species. There are concerns that some stocks are depleted due to overfishing and environmental changes. We review data collection and population assessments currently used for nine pikeperch stocks across six European countries and apply a unified assessment framework to evaluate population status and trends. For this we first standardised commercial, scientific, and recreational catch-per-unit-effort (CPUE) and catch time series and then applied Bayesian surplus production models. Our results showed that three stocks (including two in the Baltic Sea) were strongly depleted, with estimated biomasses considerably lower than the biomass at maximum sustainable yield (Bmsy). Other stocks were either close or higher than their estimated Bmsy. Looking at the trends, we find that four stocks (Lake Oulujarvi, Kvadofjarden, Lake Peipsi and Lipno) showed increasing biomass trends and two (Curonian Lagoon, Galtfjarden) had a strong decline in biomass. In most cases the stocks with clear signs of recovery were also those for which strong management strategies have been implemented. We find that, despite pikeperch being one of the most valuable inland fisheries, formalised stock assessments and regular surveys remain rare. Importantly, although most stocks are strongly targeted by recreational fishing, estimates of recreational catch are highly uncertain. We conclude that data limited stock assessment methods are useful for assessing fish population status and highlight an urgent need to improve pikeperch scientific monitoring and assessment of recreational catches.

ecology↗

bioRxiv2022

Impacts of recreational angling on fish population recovery after a commercial fishing ban

It is often assumed that recreational fishing has negligible impact on fish stocks compared to commercial fishing. Yet, for inland water bodies in densely populated areas, this is unlikely to be true. In this study we demonstrate remarkably variable stock recovery rates among different fish species with similar life histories in a large productive inland freshwater ecosystem (Kaunas Reservoir, Lithuania), where all commercial fishing has been banned since 2013. We conducted over 900 surveys of recreational anglers during a period of four years (2016 to 2021) to assess recreational fishing catches. These surveys are combined with drone and fishfinder device-based assessment of recreational fishing effort. Fish population recovery rates were assessed using standardised catch per unit effort time series. We show that recreational fishing is having a major impact in retarding the recovery of predatory species, such as pikeperch and perch. In contrast, recovery of roach, rarely caught by anglers, has been remarkably rapid and the species is now dominating the ecosystem. Our study demonstrates that recreational fishing can have strong impacts on some fish species, alter relative species composition and potentially change ecosystem state and dynamics.

ecology↗