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Circle of life: Marauding deep-sea monkfish prey on shallow-diving dovekies when the timing is right

Shallow-diving dovekies are opportunistically eaten by deep-sea dwelling monkfish.

Shallow-diving dovekies are opportunistically eaten by deep-sea dwelling monkfish. Photo courtesy Chris Melrose, NEFSC/NOAA.

Research aims to learn more about bird-eating fish

By Summit Voice

SUMMIT COUNTY — Everybody knows it’s a dog-eat-dog world out there, but when cute little seabirds start showing up in the stomachs of bottom-dwelling, deep-sea fish, biologists get curious.

So when USGS biologist Matthew Perry heard that New England fishermen were finding tiny dovekies inside monkfish, he decided to investigate how this previously unknown link in the ocean foodchain works.

“I was studying long-tailed ducks and thought, to avoid being eaten, these birds fly 30 to 50 miles to Nantucket Sound each night and return to the ocean in the morning,” said Perry, a research wildlife biologist at the USGS Patuxtent Wildlife Research Center in Maryland. “People ask why don’t dovekies fly to Nantucket Sound at night like the long-tailed ducks to avoid goosefish?  My explanation is that dovekies have small wings and can’t make the routine flight.”

Dovekies are small Arctic seabirds and the smallest member of the puffin family. They breed along the Arctic coast and head south in the winter, typically as far as New England.  The dovekie (Alle alle), also known as little auk, is the smallest of the auks. It lives in the open ocean and can dive to depths of more than 100 feet to prey on small fish, crustaceans, and zooplankton.

A goosefish or monkfish (Lophius americanus) is measured at sea. Photo courtesy NOAA.

A goosefish or monkfish (Lophius americanus) is measured at sea. Photo courtesy NOAA.

Monkfish, also called goosefish (Lophius americanus) are highly opportunistic predators. Distributed from the Gulf of Maine to Cape Hatteras, N.C., the fish are typically  partially buried on soft bottom habitats and attract a variety of prey by using a modified dorsal fin ray that resembles a fishing pole and lure.

Perry and other wildlife biologists wanted to know how this deep-water fish finds a shallow-feeding bird in offshore waters, so they looked at when, where, and how these animals were most likely to be in the same place at the same time.

It may all be a question of timing, they concluded, publishing their findings online in the Northeastern Naturalist. Study co-author Anne Richards, of  NOAA’s Northeast Fisheries Science Center, said tagging studies that she and colleagues have conducted reveal that goosefish swim considerable vertical distances from the bottom to near the surface, especially during their spring and fall migrations onshore and offshore in response to water temperatures and related factors.

Goosefish leave the bottom to use the currents during migration periods or to spawn at the surface. If prey items are encountered during their vertical movements, the goosefish take advantage. Hence, timing may be the key factor in bringing dovekies and goosefish together in the same place.

“Given the common name ‘goosefish’, it is not surprising to find birds in goosefish stomachs, but it is surprising to find that this predation occurs over deep water, “Richards said.  “Goosefish do not actively seek out the dovekies, but when such tasty morsels are available in the water column, the fish are going to consume them.”

Another source of data used in the study is the NOAA NEFSC food-habits database, which contains decades of predation information collected from the stomachs of fish that are caught during regular research vessel surveys. While not a particularly good measure of how often or how many birds are eaten by fish, these data confirm that not only goosefish, but also spiny dogfish, Atlantic herring, pollock, Atlantic cod, red hake, and fourspot flounder will eat birds.

“One thing we know is that dovekies cannot dive to the bottom in 300 to 400 feet of water,” Perry said. “Goosefish probably come up from the ocean bottom to within 10 to 20 feet of the water surface at night. As dovekies dive for amphipods, small crustaceans, in the morning at first light, goosefish seize the opportunity and might use their ‘fishing lure’ to simulate one of these prey species by attracting the dovekies with their typical ‘sit and wait’ behavior.”

The magnitude of fish predation on seabirds is poorly understood. Perry says most food habit studies for goosefish have been conducted during summer when the dovekies have migrated north to their Arctic breeding areas; thus, they seldom have been recorded as prey.  Perry hopes more telemetry tracking of goosefish will be done in winter when birds are in the area and are potential prey.

As for what’s ahead, Richards says ongoing use of electronic tags on goosefish will provide more information on their vertical movements.

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