The burbot is a fish that may be familiar to many readers of this blog. This handsome creature is a close relative of cod and haddock, and is the only member of the Gadiformes (the ‘cod-like’ fish) found in freshwater. Many anglers have encountered burbot when ice fishing for lake trout. While they are not a highly sought after game-fish, they are a tenacious predator and are capable of eating fish that are nearly as large as themselves.
Interestingly, burbot are one of the few species in Canada that spawn in mid-winter, underneath lake ice. Because of this, very little is known about their reproductive ecology, and it has been challenging to prevent burbot declines because of this limited knowledge. One important question about mid-winter breeding is how male and female burbot find one another. In mid-winter lakes are dark (because of ice cover) and very cold, which means that searching for mates is challenging and energetically costly.
A recent study from a group of Canadian and Scottish researchers has found that burbot actually sing to attract mates during the breeding season. The researchers took adult burbot from the wild and kept them in a artificial under-ice enclosure that was fitted with underwater microphones. They found that burbot make a suite of different sounds, and that they probably use a drumming muscle that is attached to their swim bladder in order to do so. Burbot drumming muscles increase in size during the breeding season, and males have larger muscles than females, suggesting that males do most of the singing.
Singing to attract a mate may be a clever adaptation to breeding in a low light environment, and is yet another interesting characteristic of a very cool fish. It also suggests that noise disturbance, for example from industrial activity, could disrupt burbot reproduction. As a result, burbot conservation may depend on limiting noise pollution during winter in freshwater ecosystems.
Citation PA Cott et al. 2014. Song of the burbot: Under-ice acoustic signaling by a freshwater gadoid fish. Journal of Great Lakes Research 40:435-440.
Find the study here