Bubble-net feeding humpbacks

A humpback whale lunges at the surface to feed on small fish that have been corralled by a bubble-net. ©MICS Photo

Yesterday the team witnessed another surface feeding event, but this time, the whales were using a special technique: Bubble-net feeding!

This is a type of cooperative feeding behaviour that has been well-documented in humpback whales in southeast Alaskan waters, but is less commonly observed in the St. Lawrence.

During bubble-net feeding, certain whales in the group will slowly release a continuous stream of air from their blowhole (sometimes producing loud "feeding calls") while swimming in increasingly small concentric circles below a school of fish. Other whales will help corral the fish from the sides, thus "herding" them into a dense ball of prey close to the surface, which they then lunge through with open mouths, engulfing the dense patch of fish.

The concentric circles of the bubble-net are clearly visible from the surface, a telltale sign that a humpback is about to emerge in the middle of it all! ©MICS Photo

Many bird species take advantage of these occasions to feed on the fish that have been trapped just below the surface by the whales, as was the case of these Great Shearwaters and gulls!

Great Shearwaters take advantage of the bubble-nets corralling the fish at the surface to feed on fish as well. ©MICS Photo

Though we could not be sure, it seemed that the humpback whales we saw were feeding on small sand lance. As this group of humpbacks was not previously known to us, we biopsied them to add to our database.

A close up of the mouth of a humpback whale, with what appears to be a sand-lance stuck in its baleen. ©MICS Photo

Check out this humpback whale's eye! ©MICS Photo