New video footage of dolphins, whales and sharks being caught and killed in mile-long fishing nets off Southern California could create pressure to end the controversial practice of drift-net fishing statewide, according to a coalition of marine wildlife conservation groups that is publicly releasing the material.

The footage, obtained by Mercy for Animals and other groups, graphically depicts marine mammals entangled in the long nets and shows fishing boat crews using knives to kill inadvertently caught animals.

“It’s very disturbing,” said Lindsay Wolf, a spokeswoman for Mercy for Animals, a group based in Los Angeles. “It exposes a shocking level of marine animal abuse.”

The video, which may be viewed on www.bandeathnets.com, is the latest weapon in the conservationists’ decades-long battle against the use of drift nets, which are known to catch such marine mammals as dolphins and whales in addition to the swordfish that the nets are intended to catch. A typical drift net is a mile long and hangs 100 feet deep and often yields what is called a “bycatch” of unwanted fish and marine mammals that cannot escape the net, the conservation groups maintain.

The size of the California drift-net fishing fleet is about 20 vessels, down about 80 percent from two decades ago, according to Michael Milstein, a spokesman for the National Oceanic and Atmospheric Association, which regulates the drift-net fishery.

Milstein acknowledged that drift-net fishing “has been controversial for a long time and has been scrutinized for a long time.” He said the NOAA closely regulates the fleet and routinely posts observers on vessels to ensure that fishermen follow drift-net rules.

But the animal rights coalition — which also include SeaLegacy, Sharkwater and the Turtle Island Restoration Network — maintained that drift nets “indiscriminately trap sea animals, including protected species such as dolphins, whales and sea lions, who are then killed or thrown away.”

The images in the minute-long video montage show suffocating fish, trapped dolphins and sea lions, an entangled seabird and other animals being cut apart while still alive.

Wolf said most of the footage came from an “undercover investigator” who had been aboard two vessels last year in the Channel Islands area off Southern California, where much of the state’s drift-net fishing takes place.

The head of a fishermen’s trade association called the deaths of dolphins and whales an “unfortunate and very rare” problem that the industry has done its best to reduce.

“It’s always possible to have an accident such as this, but our folks do everything they can to make sure it doesn’t happen,” said Glen Spain, regional director of the Pacific Coast Federation of Fishermen’s Associations, which includes about 600 fishing boats in its membership.

“It’s a disaster for us when we catch a fish that we cannot keep and cannot sell,” he said. “We don’t want to do that. But it’s unfortunate that some groups try to demonize the fishing industry.”

Spain said his group believes closely regulated drift-net fishing should be allowed to continue.

The video campaign is tied to a proposed new state and federal legislation to ban drift-net fishing.