Drumming Up Love in the Cold
By Angela Ten

Winter is the season for love. Nothing is more romantic than cuddling up with your partner to shelter from the cold. Don’t agree? Ask the burbot!

Burbot (Lota lota) are the only freshwater members of the cod (Gadidae) family. They’re sometimes called Ling, or Ling Cod. They can be easily identified by the long, eel-like body, and the single barbel on their chin.

Note the barbel on this young burbot’s chin

In the winter, most fish hunker down from cold, but for burbot, this is the perfect time to get frisky! To prepare for their sub-zero courtship, burbot spend much of the fall and early winter bulking up. One organ that grows in preparation for spawning season is their swim bladder!

The swim bladder is a gas-filled organ in fish that regulates their buoyancy, or their position in the water column. This may seem like it has nothing to do with reproduction, but burbot also use their swim bladder to make sounds! Burbot have drumming muscles that beat on their swim bladders and create rapid, low-pitched vocalizations that sound like a motorcycle revving.

These burbot could form an amazing drumline!

Vocalizations in burbot are not well-studied, but scientists believe that drumming is a spawning behaviour in burbot, since the organ grows leading up to the spawning season. In Atlantic Cod, males that can drum louder and longer are more successful at attracting mates; this may be true for burbot as well.

Between December to May, lake-dwelling burbot migrate at night to shallow waters and small streams to spawn. Since spawning occurs at night when visibility is poor, burbot do not develop any visual cues for spawning, like changes in colour or size. This is another reason why drumming may be a key part of their spawning rituals, since you don’t need to see to hear!

Burbot are well camouflaged year round

While many other fish will defend mates or territories during the spawning season, burbot are relatively peaceful fish, and do not fight with each other. Instead, dozens of individuals will come together in a big, squirming burbot ball to spawn.

Female burbot in these spawning balls may release up to 3,000,000 eggs each! After spawning, these small eggs are carried with the current until they settle to the bottom of the lake or stream, and hatch 1-3 months later. After another 2-8 years of growing, these burbot will be ready for some winter loving of their own!