Grayling in the battle for food: The bigger one usually wins, but the more aggressive can too
How do salmonid fish prepare for the harsh Alaskan winter? During the short summer period, they must catch enough food and accumulate energy reserves to survive the cold remainder of the year. The battle for food among Arctic grayling (Thymallus arcticus) has become the focus of scientists from the Biology Centre of the Czech Academy of Sciences and the University of Georgia. Thanks to advanced underwater videography, they managed to capture fascinating moments from the pristine Alaskan rivers' underwater world and reveal how grayling decide when and with whom to engage in a battle for the best position in the current. The scientific study was published in the Journal of Fish Biology, where it was selected for the Editor’s Choice as one of the key articles of the issue. Additionally, a photograph from the study graces the cover of the current issue.
Picture above: the head of a Arctic grayling (Thymallus arcticus) clearly visible below the water surface while eating insects. The photo made the cover of the Journal of Fish Biology. Photo: Jason Neuswanger
The results of the study showed that grayling spend most of their time (81%) in favorable positions in the current, where they have the best access to food. They actively hunt for insects about 14% of the time, but when it comes to a worthwhile catch, they can become fierce competitors. Although aggressive encounters made up only 5% of the observations, they were not random – grayling chose opponents of similar size (±10 cm), indicating that they carefully weigh whether to engage in a fight. Surprisingly, however, the winners of the encounters were mostly larger individuals, suggesting that the fish may not have a perfect size assessment of their opponents or that in certain situations, even smaller fish take risks by fighting with larger rivals.
Another interesting finding? The fish that initiate the conflict have the advantage! The study showed that the fish that initiated the conflict had a higher chance of winning – regardless of their size. This suggests that, in addition to strength, courage and strategy also play an important role in underwater battles.
The significance of this study is highlighted by Journal of Fish Biology, which emphasizes how crucial it is to study fish behavior directly in their natural environment. “The results from this study illuminate the amazing conflicts, struggles, tradeoffs, and strategies playing out every day, below the waterline. It also demonstrates the value of assessing organisms in their natural environment, capturing the fantastic diversity that fish are renowned for,” writes William Bernard Perry in Editor’s Choice.
Publication:
Holubová M., Peterka J., Simon T., Neuswanger J., Grossman G. (2025) Dominance and size affect foraging position choice by Arctic grayling (Thymallus arcticus). Journal of Fish Biology 106: 552-563.
DOI: 10.1111/jfb.15974
