|Saving Whale Sharks Off Kenya’s Coast
News Segments Tue, 08/19/2008 – 14:19
The whale shark is the biggest fish species in the ocean. Up to 18 meters long, this vegetarian is found across the world’s tropical waters, from Belize to northern Australia. Their huge dorsal fins, which make for highly prized culinary delicacies, fetch high prices on South-East Asian markets, leading them to be almost fished to extinction off India’s western coast a few years ago. On the other side of the Indian Ocean, whale sharks have come under threat in recent years off Kenya’s southern coast. But there, they have been collateral damage: often accidentally trapped in drift nets donated by US AID to local fishers. A grassroots organization is now working to stem the damage caused by these nets which they say has been endangering not only the sharks, but the coral reef as well. Arusha Topazzini reports from Diani, Kenya.
From Free Speech Radio News
|Marine life rebounds dramatically in areas designated off-limits to fishing, according to the first comprehensive review of the impacts of marine reserves over time. Moreover, the effects are fast and long-lasting. And that’s unexpectedly good news for ailing marine ecosystems, scientists say.
Although marine reserves are gaining popularity as a means to protect areas of the sea from overfishing and other human activities, much less than 1% of ocean waters is protected worldwide. And although it makes sense that ocean life would benefit from areas without the pressures of fishing, reserves were set up with little understanding of their actual effectiveness.
To determine how marine life responds to reserves, marine ecologists Ben Halpern and Robert Warner of the University of California, Santa Barbara, reviewed 81 studies that measured the biological health of 80 “no-take” reserves ranging in age from 6 months to 40 years. The results were striking: Overall, reserves boasted 20% to 30% more species, and the average size of fish and invertebrates was similarly greater, they report in the May issue of Ecological Letters. Populations were nearly twice as dense, and the total amount of living matter was nearly three times greater in reserves than in unprotected areas.
When the researchers analyzed the changes within individual reserves over time, they discovered something even more remarkable: The benefits of protection kicked in quickly and peaked within a few years. “Many species seem to be quite resilient when given a permanent refuge,” Halpern says. The fast recoveries are very surprising, he adds, because most people expected that reserves would have to be in place for many years before the effects would be so obvious.
Charles Wahle, director of the Science Institute of NOAA’s Marine Protected Areas Center, says the work “represents an important turning point in the national dialog about using protected areas to conserve our most important marine ecosystems.” He says the findings present the most compelling and comprehensive evidence to date that marine reserves are effective within their boundaries.
|Rehabilitation of stranded marine mammals elicits polarized attitudes: initially done alongside display collections, but release of rehabilitated animals has become more common. Justifications include animal welfare, management of beach use conflict, research, conservation, and public education. Rehabilitation cost and risks have been identified that vary in degree supported by data rather than perception. These include conflict with fisheries for resources, ignorance of recipient population ecology, poor understanding of long-term survival, support of the genetically not-so-fit, introduction of novel or antibiotic-resistant pathogens, harm to human health, and cost. Thus facilities must balance their welfare appeal against public education, habitat restoration, human impact reduction, and other conservation activities. Benefits to rehabilitating marine mammals are the opportunity to support the welfare of disabled animals and to publish good science and so advance our understanding of wild populations. In specific cases, the status of a population may make conservation the main reason for rehabilitation. These three reasons for rehabilitation lead to contrasting, and sometimes conflicting, management needs. We therefore outline a decision tree for rehabilitation managers using criteria for each management decision, based on welfare, logistics, conservation, research, and funding to define limits on the number of animals released to the wild.
Michael Moore, Greg Early, Kathleen Touhey, Susan Barco, Frances Gulland, Randall Wells (2007)
REHABILITATION AND RELEASE OF MARINE MAMMALS IN THE UNITED STATES: RISKS AND BENEFITS
Marine Mammal Science 23 (4), 731â€“750.
LOS ANGELES, CALIFORNIA–Marine mammals won some protection last week from the U.S. Navy’s submarine-chasing sonar technology. A federal judge imposed significant restrictions on use of the technology, known as mid-frequency active (MFA) sonar, in training exercises taking place off the southern California coast through January 2009. Environmental groups that brought the suit hailed the ruling. But researchers say it still leaves the most vulnerable species with little added protection.
MFA sonar detects ultraquiet submarines by bouncing powerful sound waves off their hulls. For more than 10 years, mass strandings of beaked whales and other marine mammals have been linked to its use, although the mechanism is not clear. Ruling on 3 January that the sonar posed a risk to species in the waters off southern California, Judge Florence-Marie Cooper of the U.S. District Court for the Central District of California ordered the Navy not to use it within 22 kilometers of the coast. She also told the Navy to use shipboard observers, aircraft, and hydrophones to monitor for marine mammals before and during the exercises and to turn off an MFA system if a marine mammal was detected within a 2000-meter “safe zone.”
The Navy had sought less stringent restrictions. But Cooper called one such proposal–a safe zone of 180 meters–“grossly inadequate to protect marine mammals from debilitating levels of sonar exposure.” At the same time, Cooper said that granting the 45-kilometer exclusion zone sought by plaintiffs, led by the Natural Resources Defense Council (NRDC), a New York City-based nonprofit, would “prevent the Navy from training to detect submarines in the very bathymetry [deep submarine canyons] in which submarines are most likely to hide.”
Those canyons are also a popular foraging spot for beaked whales, the group most susceptible to MFA sonar. Robin Baird, a marine mammalogist with the Cascadia Research Collective in Olympia, Washington, who gave expert testimony in the case, says the zone will protect porpoises and migrating whales, but it does little for beaked whales. Likewise, a 2000-meter safe zone around sonar sources won’t necessarily protect beaked whales, who Baird says are “more or less invisible” even at 300 meters.
Baird says that sea-floor hydrophone arrays, such as the Navy operates off San Clemente Island, can detect the whales’ clicks and warn vessels of their presence. In other areas of the exercise zone, however, the downward directionality of the whales’ clicks, coupled with the high speed of Navy vessels, makes ship-mounted hydrophones “fairly ineffective,” according to Baird.
Necroscopies of stranded individuals point to decompression sickness–bubbles in the blood formed by rapid changes in pressure–as the cause of death. However, says Baird, “there’s still a lot of uncertainty about what could lead to those symptoms.” One possible reason that MFA sonar is particularly problematic for beaked whales is that its pings mimic the calls of killer whales, their primary predators. In a recent study, Peter Tyack of the Woods Hole Oceanographic Institution in Massachusetts speculates that the false calls might prompt the whales to leave the area rapidly by making a series of short, shallow dives that promote bubble growth.
|ALGAL TOXINS LINKED TO MARINE MAMMAL DEATHS.
When toxins from common microscopic algae build up in fish and seagrass, they can kill large numbers of dolphins and manatees, according to new research. The findings may help explain the recent deaths of these creatures in Florida waters, even when harmful algal blooms were no longer present.
Florida is no stranger to harmful algal blooms, also known as red tides. The phenomenon occurs when populations of toxic microscopic algae explode, turning the sea red, brown, green, or yellow. The organism responsible for red tides (Karenia brevis) produces a potent poison called brevetoxin that kills fish and sickens people when they eat filter-feeding organisms such as clams and oysters. Scientists suspected that the same toxin was causing the deaths of dolphins and manatees, but they couldn’t understand why the creatures continued to die long after the bloom had passed.
The search to find the cause of the deaths gained greater urgency in 2002 when 34 manatees turned up dead in southwest Florida. Two years later, 107 dolphins died. Although a test of the waters showed relatively low concentrations of K. brevis, marine biologist Jerome Naar of the University of North Carolina, Wilmington, and colleagues found that the stomach tissues from the dead animals contained high levels of brevetoxin, suggesting the poison was introduced through food. Further testing showed that seagrass in the manatee stomachs was loaded with the toxin, as were the menhaden fish inside the dolphins.
Since even small amounts of brevetoxin can kill fish, Naar wondered if live fish could accumulate and retain the poison. When he fed fish in his lab toxic clams and red tide algae with low levels of the toxin, the fish stayed healthy but accumulated the toxin in their tissues. The findings indicate that fish can remain a potent source of algal toxin long after a red tide has disappeared, says Naar, whose team publishes its findings in the 9 July issue of Nature.
“This is very bad news,” says David Townsend, an oceanographer at the University of Maine, Orono. Already facing danger from fishing nets and accidents with boats, he says, “Florida’s manatees and dolphins don’t need any more help dying.”
“REPORT OF THE SECOND INTERNATIONAL WORKSHOP ON CONSERVATION AND RESEARCH NEEDS OF THE EASTERN TAIWAN STRAIT POPULATION OF INDO-PACIFIC HUMPBACK DOLPHINS, SOUSA CHINENSIS
The workshop was held in Changhua City, Taiwan in early September 2007; below is a short summary.
Taiwan’s Indo-Pacific humpback dolphins (Sousa chinensis) face imminent extinction if measures are not taken to protect them and their habitat from a number of serious threats. The recent demise of the baiji (Lipotes vexillifer) in China’s Yangtze River gives a particular sense of urgency to concerns about the fate of Taiwan’s humpback dolphins. The humpback dolphin is a fish-eating mammal that lives in shallow estuaries and nearshore waters and is especially vulnerable because it relies on habitat at the interface of land and sea. Research suggests that humpback dolphins residing in the eastern Taiwan Strait (=waters of western Taiwan) comprise a distinct population of less than 100 individuals.
The eastern Taiwan Strait humpback dolphins were the focus of an international workshop held in ChanghuaCity (Taiwan) on 4-7 September 2007. Participants included local dolphin researchers, conservationists and marine engineers, as well as experts from Canada, the United States, Japan, Brazil, United Kingdom and Hong Kong. Officials from government agencies, representatives of academic institutions and members of local conservation groups provided a grim picture of the state of the coastal marine environment along the west coast of Taiwan. Five major threats were identified: reduced river flow into estuaries, habitat loss, entanglement in fishing gear, industrial and municipal pollutant discharges, and underwater noise.
The expert group called on the Taiwanese government to proceed with a formal and public declaration of important habitat for the humpback dolphins; carry out public and transparent evaluations of existing and planned projects that may have impacts on the humpback dolphins and their habitat; mitigate such impacts using best available methods; prohibit the use of gill nets and trammel nets in nearshore waters; limit tourism focused on humpback dolphin-watching to shore-based platforms (including provision of public access to degraded habitat, thus promoting support for clean-up programs); and disclose pollutant concentrations and other environmental data.Only through the concerted efforts of individuals, organizations, central and local government agencies and industry will the distinct eastern Taiwan Strait humpback dolphins survive.
John Y. Wang, Ph.D.
(Member of the IUCN Cetacean Specialist Group)
FormosaCetus Research and Conservation Group
310-7250 Yonge Street
Thornhill, Ontario, CANADA, L4J-7X1
National Museum of Marine Biology and Aquarium
2 Houwan Road
Checheng, Pingtung County, 944, TAIWAN”