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.
Source: San Diego Reader

Great White Shark: San Diego sighting adds one more juvenile to population

This past Thursday, in San Diego, California, a 5-foot juvenile great white shark was reported by two scuba divers at around 500 yards off shore of La Jolla Cove in about 30 feet of water. Lifeguards briefly closed the beach while they cruised the area but soon reopened the beach, issuing a precaution to swimmers and leaving it at that. The local press reported the sighting without any overwrought hysteria and moved on to their next sound bite.

Chock up one for common sense.

Frankly, it does my heart good to hear of these sightings. With each juvenile seen, we know there is one more shark to add to the white shark's precarious population; one more shark that can, in 10 years, reproduce and, as Matt Hooper said, "make little sharks." Juvenile white sharks do not pose a substantial threat to humans as they are fixated on fish as menu items. It won't be until they reach maturity that they graduate to pennipeds (seals and sea lions) and the possibility of a surfer or swimmer being mistaken for a seal could occur, and has occurred.

But why off of warm Southern California? Juveniles have been sighted from Malibu to San Diego. There are deep canyons that run along the coastline in which juvenile white sharks can comfortably cruise, feeding on fish, while adults have generally taken up their migration patterns that often bring them to areas of seal or sea lion concentrations, like the Farallon Islands off San Francisco and Isla Guadalupe far off the Baja coast.

A recent report from the Shark Research Committee, a California non-profit headed by well-known shark behaviorist Ralph Collier, cited 7 unprovoked shark attacks along the Pacific Coast in 2010; 5 in California waters and 2 off the Oregon coast. Only one attack produced a fatality. Of interest were the activities the people were involved in at the time of the incidents: 3 surfing, 2 kayaking, 1 paddle-boarding, and 1 boogie-boarding. All surface activities, all included an elongated shape with limbs or paddles in the water. When you add in the right conditions of low visibility or other possible attractants like heavy splashing or nearby pinnipeds, all lend themselves to the classic scenario of mistaken identity as the white shark executes its typical single-bite ambush technique which it uses on an unsuspecting seal or sea lion (although not definitively confirmed, the white shark was suspected in all seven incidents). The attacks also took place in the late summer/early fall. This is when many adult great whites are on the move, returning from their mid-Pacific migration, back to their coastal hangouts.

Given the image that is generally served up by the media, I don't expect the general public to rejoice with every sighting of a great white shark along the California coast. But it's good to know that the circle of life is still taking place for these threatened ocean predators who play such an important role in balancing the marine ecosystem. Hopefully, the juvenile white shark seen off La Jolla Cove will not encounter poachers and live to carry on the species.

Read about the white shark sighting in San Diego.
Read about the Shark Research Committee report.

Moon Jellies: mass stranding near San Francisco

Just this past September I reported on a sea jelly invasion in Monterey, California. For a good portion of the late summer, the popular central California ocean community was beset with west coast sea nettles - beautiful to look at but potentially painful, given the numbers that were accumulating from the bay right up to the shoreline.

Another high concentration of sea jellies recently occurred at Ocean Beach, located near San Francisco. This time it was thousands upon thousands of moon jellies that had washed up on the beach overnight this past weekend. But in this instance, it was not so much an invasion as it was a freak occurrence linked to a cyclical event.

Moon jellies are one of the more prolific of all jellies. A popular attraction at many aquariums, they are relatively easier to breed, compared to other species, and do not pose a threat to humans. In the fall, they can have large spikes in their populations along the eastern Pacific coast. These sea jelly "blooms" can go unnoticed for the most part, unless the right tidal and wave conditions push the floating moon jellies ashore. Which is apparently what happened this past weekend.

Gary Williams, a researcher of invertebrates at the California Academy of Sciences described it as a "regular event," “Jellyfish cluster in massive blooms well offshore that we rarely see. But sometimes, with just the right combination of wind and currents, those blooms wash ashore.”

As relatively common as the moon jelly is, there is surprisingly little we know about them. The when, where, and how of their reproduction habits is still predominantly a mystery. Because of that, it makes it difficult for scientists to attribute any apparent rise in population to outside factors such as climate change.

However, further south from San Francisco in San Diego, California, a rare black sea nettle has been making more frequent appearances along that Southern California coast. Actually deep purple in color, the black sea nettle is much larger than the west coast sea nettle, reaching 3 feet across and with up to 30 feet of trailing tentacles.

Though not yet seen in invasion-size numbers, the black sea nettle, according to some oceanographers, could be increasing in numbers due to warming temperatures or a consistent increase in the primary food source, plankton - which also "blooms" with warmer water temperatures.

Beautiful, fascinating, and in many ways a mystery, sea jellies are basic predatory invertebrates (and, technically, by definition not a fish - as in "jellyfish"), simple in structure with no brain or heart but exhibiting behaviors that have yet to be fully explained.

Read about San Francisco's moon jelly stranding.
Read about San Diego's black sea nettle.

Humboldt Squid: the "red demon" moves into Southern California

Like something from Disney's Twenty Thousand Leagues Under the Sea, the humboldt squid is a formidable predator typically found in deep Pacific waters off of Mexico and Central America. Reaching up to five feet in length and as much as 100 pounds, it is fast and aggressive with a voracious appetite.

And it is beginning to appear in shallower water off of Southern California. In San Diego, during night dives, scuba divers are encountering groups of humboldt squid, and several have moved too close into the shallows and been washed up on the beach.

According to a recent AP news report,

"Research suggests the squid may have established a year-round population off California at depths of 300 to 650 feet, said Nigella Hillgarth, executive director of the Birch Aquarium at Scripps Institution of Oceanography. Divers this summer have been encountering them at about 60 to 80 feet down, they said. No one knows how many squid are in the shallow waters, but one biologist estimated they could number in the hundreds, or possibly thousands.

'Usually where there's one squid, there's a lot of squid, so I would assume that there's a good number,' said John Hyde, a biologist with the National Marine Fisheries Service in San Diego."

Scientists are not sure why the squid have moved further north or are entering shallower waters. Explanations range from global warming to loss of prey to a reduction of natural predators. On this last point, I have read studies that have explained the bio-dispersion of various species based on the predators that feed upon them. When the predators are gone, then the species in question is no longer "corralled" as it normally would and changes in bio-dispersion or migrations can occur. In the case of humboldt squid, sharks are one of its key predators.

Whatever the explanation for the squid's movement north, there is reason for some concern. They can pose a serious risk to unsuspecting divers and their voracious appetites can severely impact local fisheries. Scott Cassell, CEO of the Undersea Voyager Project, who has spent many years studying and filming humboldt squid, recently told me that in his studies he had predicted the potential for this danger as much as ten years ago.

Another possible example of the ramifications either climate change, overfishing, or loss of apex predators - or all of the above.

Care for a calamari ring the size of your dinner plate?

Richard Theiss responds to San Diego shark incident on CBS News

On 04/28/08, RTSea wrote: From Richard Theiss, filmmaker Island of the Great White Shark, regarding the recent San Diego shark incident:

On Friday, 4/25, the news hit of a man fatally bitten by a white shark off Solana Beach, near San Diego, CA. I was asked by CBS and KCAL news to comment (http://www.cbs2.com/video/?id=65566@kcbs.dayport.com).

It's always a tragic event when someone is attacked by an animal and my heart goes out to the victim's family and friends. Judging by the news reports that filtered in over the course of the day, it would appear that the attack was a classic case of mistaken identity with the shark mistaking the swimmer for a possible seal. Apparently, the swimmer was slightly apart from a group of other swimmers 150 yards off shore, with some of the swimmers wearing dark wetsuits or swimsuits. The shark approached in the manner typical of a seal hunting behavior.

It has been many years since there has been a shark attack in Southern California and the news organizations have made quite a fuss, as the southland was preparing for a sunny and warm weekend. Without minimizing the loss of a popular local resident, let's hope level heads prevail so as to not generate 70's-style "Jaws" hysteria