South Carolina Bull Shark

Another shark video is making the viral rounds on the Internet. But rather than be one that invokes sadness or anger for depicting some poor trophy prize hung by its tail or a sea of shark fins drying in the sun, this short video from South Carolina illustrates a unique quality of what is considered to be one of the more aggressive sharks. Along South Carolina's North Myrtle Beach is House Creek which is fed by tens of smaller creeks and streams and ultimately spills out to the sea. This transition from fresh to saltwater makes for brackish water that some ocean fish are able to tolerate. One such animal is the bull shark. If you have not yet seen the video, a young woman, Sarah Brame, accompanied by her fiance and stepfather, was fishing off the dock at Cherry Grove Inlet, a small body of water connected to House Creek by a small feeder stream. As she was reeling in her first fish, a local variety called drum, a 5-6 foot bull shark suddenly lunged, breaking the surface and taking her catch in one swift flurry of splashing water and hungry shark. Quite a remarkable piece of video (see below).  What makes the video all the more remarkable is its illustration of the bull shark's ability to withstand brackish to near fresh water, which allows it to move up streams and rivers and get into places where you least expect to find a large shark. (See the map of the Cherry Grove Inlet and House Creek.) Bull sharks have been found many miles upstream in South American rivers and the famous Matawan Creek shark attack of 1916 in New Jersey, which many at the time attributed to a great white, was, in hindsight,
 very likely  a bull shark. Bull sharks are also one of the more aggressive sharks. Aggressive in that, when on the hunt, they do not rely on a single massive bite, like a white shark will do to a seal (or a mistaken swimmer). Instead, the bull shark will hunt large prey with repeated bites. This has been borne out by reports of swimmers or surfers who, when attacked by a bull shark, found that it would give chase and bite repeatedly in a rather tenacious, never-give-up manner. While a bull shark, like all sharks, do not single out humans as a specific prey, it is this determined behavior by the bull shark that puts it in the top four of most dangerous sharks (the other three being, white sharks, tiger sharks, and oceanic white tips). I have had the opportunity to get up close with a variety of shark species and the bull shark is the one that draws my utmost attention. After Sarah lost her catch in such a spectacular fashion, her fiance and stepfather contemplated taking their 10-foot boat out on the water to track down the shark, but after a few minutes on the water, they rethought the matter. "We need a bigger boat and a bigger net," said Van Hughes, Sarah's stepfather. "We need a bigger boat." Now, where have I heard that before. . . .  According to Dan Abel, shark researcher at the Coastal Carolina University, "It's not like just because we saw this shark yesterday that was just chasing this fish that was struggling on a line means that everything is going haywire. They're out there all the time anyway. It just so happens that this one opportunity a person caught it on film." Just another apex predator doing its thing.Source: RTSea Blog

Read More........→July 21, 2012

Manta Rays: new study tracks their movements off Yucatan

RTSea: While marine advocates fret over the plight of sharks and their fate at the hands of commercial fishermen, another of the shark's relatives is heading into perilous waters: the majestic and graceful Manta Ray. Given the unfortunate nickname "devil fish" by local fishermen, the manta ray, which can attain an enormous 25-foot wingspan, is a filter-feeder and completely harmless to humans (it does not have a stinger like other rays). Similar to baleen whales, the manta ray draws water through its mouth and, as it passes through its gills, structures called gill rakers strain zooplankton from the water. What has put the manta ray at risk - it is currently listed as "vulnerable" to extinction by the International Union for Conservation of Nature (IUCN) - is that they are hunted in some quarters for those gill rakers, a favorite of traditional Chinese medicine, and they are also caught as accidental bycatch. Part of the elasmobranch subclass that includes sharks, skates, and rays, the manta ray, like their relatives, does not have a high reproductive rate. So, they are not well-prepared to withstand high losses.However, there's much we do not know about these large rays that are so popular with scuba divers and snorklers in several tropical resort locations, representing not only a threatened species but a tourism generator as well. To fill the gap in our knowledge, a recent study which was just published in PLoS One used satellite tags, the ones often used on sharks and other pelagic fish, to learn more about the movement patterns of manta rays. Organized by the Wildlife Conservation Society, UK's University of Exeter, and the Mexican government, the study involved tagging six manta rays - four females, one male, and one juvenile - over a 13-day period off the coast of the Yucatan Peninsula. In that approximate two week period, the manta rays mostly stayed within 200 miles of the shoreline but did travel a good distance. “The satellite tag data revealed that some of the rays traveled more than 1,100 kilometers during the study period,” said Dr. Matthew Witt of the University of Exeter’s Environment and Sustainability Institute. “The rays spent most
of their time traversing coastal areas plentiful in zooplankton and fish eggs from  spawning events.” Of concern was the fact that, with the rays not necessarily staying centralized to one area but more on the prowl for waters rich in zooplankton, they spent a considerable amount of time outside the boundaries of marine protected areas and, by doing so, putting themselves at risk from commercial fishing, being caught in nets accidentally, and even exposing themselves to the risk of being struck by large ships. Less than 12 percent of the locations were the tagged animals were tracked were within marine protected areas. “Almost nothing is known about the movements and ecological needs of the manta ray, one of the ocean’s largest and least-known species,” said Dr. Rachel Graham, lead author on the study and director of the Wildlife Conservation Society's Gulf and Caribbean Sharks and Rays Program. “Our real-time data illuminate the previously unseen world of this mythic fish and will help to shape management and conservation strategies for this species.” We can only hope that this and other future studies will provide a base of knowledge that will motivate governments and international agencies to take steps to arrest the apparent decline in manta ray populations. All filter-feeders play a role in maintaining the proper balance in zooplankton and other microscopic marine animals. Were we to lose the manta ray, we would be faced with unknown consequences. Source: RTSea

Read More........→July 20, 2012

Thresher Shark Airborne: researcher takes remarkable pix of shark leaping

RTSea: With an elongated upper lobe of its caudal fin, the thresher shark is one of the most striking of all sharks. I guess that descriptor could be taken figuratively and literally as it has been shown that the thresher shark uses its tail to swat and stun its prey. Making the media rounds right now is a remarkable series of still photographs taken by marine researcher Scott Sheehan of a thresher shark leaping from the water in Jervis Bay, Australia. Possibly feeding on yellowtail baitfish, the shark leaped from the water and was first thought to be a dolphin. Sheehan readied his camera for a possible second leap and the shark did not disappoint, allowing the researcher to take a rapid series of shots. It is perhaps unusual behavior - or at least a rare occurrence - for a thresher shark to go airborne, but mako sharks have been seen taking large leaps and then, of course, there are the powerful images of great white sharks breaching as they

ambush seals from underneath. If you look at the complete series of photos, you can see the thresher sharks long tail curled - most likely snapping from side-to-side as it first breaks the surface; part of its powerful propelling motion as it moved through the bait fish. I have reported on thresher sharks before: about video taken showing one using its tail to hunt, highlighting ongoing behavioral research, and citing organizations working to help preserve this shark - listed as "vulnerable to extinction" by the IUCN. As Sheehan's images show, the thresher shark is a magnificent shark to behold whether in the water or in the air. It is also another important predator and member of a healthy marine community. Not a threat to man, it deserves our respect and protection.Source: RTSea

Read More........→June 09, 2012

Hawaiian Reef Sharks: possible competition for food causing massive decline

RTSea: For reef sharks, commercial shark fishing isn't the only thing that threatens their survival. In reef communities near populated islands, an additional threat comes from the taking of fish by local fishermen - fish that often constitute a major portion of the sharks' diets. When local and/or commercial fishermen compete for the same food source as reef shark species, it can be a crippling blow to the shark population. A recent study by Hawaii's Joint Institute for Marine and Atmospheric Research showed a drastic reduction in reef shark populations around populated islands in Hawaii as opposed to more uninhabited islands or pristine reefs. "We found 90-97 percent decline in reef shark abundance: white tip, grey, galapagos and nurse sharks," said Marc Nadon, a researcher with the Institute. The researchers have not been able to determine a more specific cause but look to accidental bycatch (sharks are now more protected, at least from legal commercial shark fishing, due to recent legislation) and overall fishing pressure as contributing factors. "70 percent of reef shark diet is reef fish, so if you remove the food source it would be logical that reef shark would follow the same trend and decline," said Nadon. While the researchers will be doing more studies this fall, their research's concern with competition for food has support based on what has been observed in other island nations. Both Samoa and the Marianas have seen major declines in reef shark populations around populated islands compared to other unspoiled reefs. Source: RTSea

Read More........→May 22, 2012

Bisarbeat: 2,000 Pound white Shark Caught in Mexico

Two fisherman in Mexico netted a monstrous catch quite unexpectedly this week: a 2,000 pound great white shark. The enormous shark, which measured almost 20 feet in length, was caught up in a net cast by commercial fishermen in the Sea of Cortez in Mexico on Sunday. The shark was already dead when the men found it, but the fisherman, identified only as Guadalupe and Baltazar, were still overwhelmed by it. “We were amazed and immediately realized that we had a huge, dead, great white shark and then we thought what are we going to do?” Guadalupe told Pisces Sportfishing’s Tracy Ehrenberg. The fishing boat had to be towed to shore with the extra weight, and more than 50 bystanders helped the men drag the dead shark onto the docks. Pisces Sportfishing reported that the shark “fed the whole town. Source: Bisarbeat

Read More........→April 22, 2012