Sunday, January 22, 2012

Ghost Fishing Nets: San Diego divers retrieve abandoned nets off old shipwreck

In July of 2011, I wrote about ocean debris - in particular, abandoned fishing nets and lobster traps - which can continued to ensnare and destroy sealife long after they have been given up as lost. Once hooked on a reef or submerged wreck, fishing nets continue "ghost fishing" and can damage reefs as they get swung about in the ocean currents or swells. Off Point Loma, near San Diego, California's Mission Bay, lies the wreck, High Seas and recently, local divers succeeded in removing approximately 200 pounds of derelict fishing nets that had become snagged on the remains of the ship.

The removal operation was overseen by Ocean Defenders Alliance, a Huntington Beach-based non-profit that solicits the help of volunteer divers to remove derelict nets. When fishing boats release their nets, which can be hundreds, if not thousands, of feet in length, the sharp edges and contours of reefs and particularly shipwrecks can easily tear away large sections of the nets. Initially the nets smother resident sealife and can continue to catch fish that get wrapped up in the nets. Then, as the net begins to settle over time, smaller portions begin to batter the reef as swells or the back and forth motion of ocean currents, called surge, begin to take its toll.

Over a greater length of time, the nets can actually become part of the reef itself, with encrusting algae, anemones, and other plants and invertebrates using the net as a strata or foundation for new growth. At this point, removal of the nets may produce more damage than intended. So, in some locations, the derelict nets are monitored for deterioration that might reverse their sedentary condition and once again damage sealife with portions of loose nets subject to moving ocean conditions.

The High Seas is a 128-foot Navy vessel built near the end of WWII and later sold and converted to a fishing boat. It sank in 1970 and has collected a considerable amount of "ghost fishing" nets over the ensuing years. The Ocean Defenders Alliance (ODA) and its team of volunteer divers first surveyed the wreck to determine how much net could be removed without doing unintended damage and then proceeded to lift portions of the nets with floats, which enabled them to cut away a large section more easily and safely. Since ODA works with volunteers, diver safety is a crucial issue regardless of the diver's experience level. A free-floating net is a hazard to fish and humans as well.

Here is a video taken in 2010 by a local San Diego diver, Jim Ridgway, of dives on San Diego's USS Logan and High Seas. The first part of the video focuses on the USS Logan and you can see the range of sealife, from fish to colorful anemones, that can call a shipwreck home. Then the video turns to the High Seas and you can clearly see the accumulated nets and the diver even came upon a small leopard shark caught in the netting.

Fisherman view the loss of nets as a frustrating and expensive occupational hazard. However, long after the commercial and economic loss, ghost nets can continue to exert a deadly toll on unintended sealife.

Click here to learn more about the Ocean Defenders Alliance.
San Diego Reader

No comments: