A bait ball in the ocean is the name given to a tight, spherical group of
small fish or other small creatures that swim together for protection when
threatened by predators. It's a bit like starlings swirling around when they
come into roost. By packing close together into a ball, thousands of
animals act as one large shape to confuse attackers and protect individuals on
the inside.
Hundreds of guillemots and razorbills dive deep into the water creating bait
balls and driving them to the surface. Eventually the fish have nowhere to go
and will leap clear of the water to avoid their pursuers. This attracts other
birds which either can't dive or can't go as deep as the auks such as gannets,
kittiwakes, shearwaters and petrels. These in turn attract other predators
such as skuas. There can be hundreds or even thousands of birds feeding in the
vicinity of a bait ball and these are known as feeding frenzies which can been
seen from quite a distance.
Unsurprisingly, cetaceans are also attracted to bait balls, so if we see a
feeding frenzy it's always worth watching for a while because whales often
surface in the middle of them. A couple of years ago I watched in awe as
humpback whales drove North Atlantic Krill to the surface (opens in a new window) and created a massive orange pink bait ball
which eventually also attempted to leap clear of the water.
This afternoon I was out again on the Minch with Steve Truluck and Hebridean
Whale Cruises. We headed from Gairloch towards Kilt Rock on Skye and there
were feeding frenzies everywhere.
