Trawling has “negligible” effect on soft-bottom

Petrale sole, a flatfish caught by trawling on soft-bottom seafloor. Credit: The Nature Conservancy

A groundbreaking new study recently conducted by California fishermen, The Nature Conservancy and CSU Monterey Bay indicates that bottom trawling only has a “negligible effect” on the seafloor and fish habitat in certain types of soft sea bottom.

Trawling is continually criticised by environmental advocates for the damage it causes to rocky marine habitats and the long-lived animals that occur in them. However, important questions remain about the extent of any damage to sandy and muddy environments.

During the three-year study, fishermen trawled patches of the ocean floor off Morro Bay. Those areas were analysed by underwater photos and video and compared with nearby areas that were untouched.

Their peer-reviewed work, published in the Fishery Bulletin, found that California’s largely soft-bottom seafloor saw little lasting impacts from trawling with a small-footrope trawl.

The researchers say that their study adds to a growing body of literature from around the world showing trawling impacts are context-dependent – the impacts depend on the type of gear used, the types of habitats trawled and how often trawling occurs.

The scientists point out that their study does not imply that all soft-bottom habitats should be open to trawling; but, with new research and technology, “we can fine-tune our fishery regulations to protect truly vulnerable habitats.”

One of the researchers, Dr. James Lindholm has been studying marine ecosystems for 20 years and this autumn he will conduct a similar experiment off Half Moon Bay using trawling nets of different sizes. Commercial fishermen will also be involved.

Read the original post: www.worldfishing.net

Bottom trawling gets a bum rap, CSUMB study finds.

Nic Coury
Local petrale sole, like this dish at the former Alvarado Fish & Steakhouse, may be a more sustainable fish than we thought.

Bottom trawling—dragging nets along the sea floor to catch species like halibut and sanddabs—isn’t always the destructive fishing method it’s made out to be, according to a collaborative study by fishermen, The Nature Conservancy and CSU Monterey Bay.

The study, published in National Marine Fisheries Service’s Fishery Bulletin, found that not all sea floors are created equal. The “soft” sea floor (mostly mud and sand) that comprises up to 85 percent of the continental shelf off the California coast may be able to recover quickly from small footrope trawl gear, the study concludes. Yet most of the state waters and much of the federal waters are closed to bottom trawling.

“Our study adds to a growing body of literature from around the world showing trawling impacts are context dependent—they depend on the type of gear used, the types of habitats trawled and how often trawling occurs,” a press release states. “Trawling in rocky areas with long-lived corals will likely have more long-lasting impacts than trawling in soft-bottom habitats that may be less vulnerable and can recover more quickly.”

Monterey Bay Aquarium’s Seafood Watch guide, which has long shunned much of Monterey Bay’s own local catch because it viewed bottom trawling as environmentally unfriendly, is now picking up on that more nuanced approach. The updated Seafood Watch guide upgraded 21 species of West Coast groundfish from red (avoid) to yellow (good alternative) or green (best choice) rankings, as the Weekly reported last fall.

Also promising: next-generation light-trawl gear that floats just above the sea floor instead of dragging. Environmental Defense Fund consultants Huff McGonigal and David Crabbe developed the technology to allow fishermen to “fish a wider area, travel faster, reduce fuel costs by a quarter and preserve bottom-dwelling fauna,” as the Weekly reported in 2013.

Read the original post: MontereyCountyWeekly.com | by Kera Abraham