Exceptional longevity in northern peripheral populations of Wels catfish (Silurus glanis)

Studies of life-history variation across a species range are crucial for
ecological understanding and successful conservation. Here, we examined
the growth and age of Wels catfish (Silurus glanis) in Sweden, which
represent the northernmost populations in Europe. A total of 1183
individuals were captured, marked and released between 2006 and 2020.
Mark-recapture data from 162 individuals (size range: 13–195 cm) were used
to estimate von Bertalanffy growth curve parameters which revealed very
slow growth rates compared to catfish within the core distribution area
(central Europe). The fitted von Bertalanffy growth curve predicted a 150
cm catfish to be around 40 years old, while the largest recaptured
individual (length 195 cm) was estimated to be 70 (95% CI 50–112) years
old. This was substantially older than the previously documented maximum
age of a catfish. The weight at length relationships in these northern
peripheral populations were similar to those documented for catfish in
central Europe indicating that resources did not constrain growth. This
indicates that the slow growth and exceptional high age in the northern
catfish populations are the result of lower temperatures and/or local
adaptations.