Monterey Bay Whale Watch - June 1998 Feature


--- Humpback Whales, Dolphins, Sea Lions, and Sea Birds in Multi-Species Feeding Aggregations in Monterey Bay ---
By Nancy Black

Multi-species feeding (16K) Since early May we have observed an incredible feeding phenomenon. Groups of 5 to 10 Humpback Whales have been feeding with hundreds of Long Beaked Common Dolphins and on some days with Pacific White-Sided Dolphins, along with up to 100 California Sea Lions, and thousands of Sooty Shearwaters. This activity has occurred on a regular basis over the last few weeks and may continue into the summer. The reason for this concentrated multi-species feeding activity seems to be the tremendous number of sardines and anchovies in Monterey Bay. In addition to these aggregations there are many other Humpbacks in the Bay feeding individually or in small groups.

Every year we see feeding Humpback Whales and dolphins on a regular basis, but this year has been extraordinary. The dolphins appear to herd the fish up toward the surface and the whales often lunge feed through the balled up fish. In this way, the whales are benefiting from the dolphins' ability to herd fish. At times, we have seen as many as three Humpback Whales simultaneously lunging out of the water with their mouths wide open and throat pleats extended. Such cooperative feeding events by whales are usually rare here, but Humpback Whales are known to feed by a variety of methods and this behavior is probably the result of huge fish concentrations. In Alaska during cooperative feeding lunges, the whales usually produce sounds that coordinate the individual whales to lunge simultaneously. Our local biologists will be using a hydrophone (underwater microphone) in an attempt to record such sounds. We also have been photo-identifying individual whales by the underside of their tail flukes to document how many different whales are involved in this activity.

In addition to the whales and dolphins, the sea lions are right in the middle of this feeding frenzy and usually dive together in small groups to feed on the fish. We have been able to locate this activity due to the large number of shearwaters flocking over the feeding area. These seabirds also benefit by diving down to catch the surface fish as the dolphins drive the fish toward the surface. We have estimated up to 10,000 shearwaters in some of these flocks. By using binoculars we can locate these flocks from several miles away. Most of this action has been happening near the edge of the Monterey Submarine Canyon, an area that seems to concentrate prey. Although the feeding activity shifts to different areas, it has been happening within the inner Bay on a fairly regular basis.

The other amazing feature about these multi-species feeding aggregations is that they are very concentrated with all the animals tightly bunched together in one area. The amount of fish available for 10 whales, 500+ dolphins, 100+ sea lions and 5,000+ seabirds must be enormous. The warmer water conditions related to El Nino could be a factor as sardines are associated with higher water temperatures. Sea temperatures in the Bay are still 2-4 degrees above normal. Most passengers who have witnessed this activity have never seen anything like it, something that is comparable to large aggregations of animals in Africa.


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U R Here Features -- June 1998

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Last updated February 8, 1999