Hawaiian Reef Sharks: possible competition for food causing massive decline

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.

5/21/12 - As a follow-up, I received some information from Dr. Chris Lowe, director of the Shark Lab at the California State University at Long Beach.  He has some concerns regarding the accuracy of the researcher's claims based on the reliability of the study's methods.  We'll have to wait and see what future studies produce.  Here are Chris' comments:

"Don't buy the 97% decline. There are some methodology problems here. I don't dispute that there are more sharks in the Northwestern Hawaiian Islands, but not by 97%. These numbers are based on towboard diver surveys and anyone who has ev...er dived in a remote location knows that a diver is a novel things - sharks come flocking to you. However, in places like the main Hawaiian Isl. sharks tend to avoid divers (spearfishermen) - who shoot at them when they approach their fish. We've set 100s of short longlines all around the most populated island (Oahu) to catch sharks to tag and have caught a lot of sharks even though we rarely saw them diving in those areas. This suggests there are behavioral responses of sharks to divers in these areas that make it likely to overestimate sharks in remote locations, while underestimating them in populated locations. In addition, diver surveys are limited to 100', but we know that reef sharks are deeper around the Main Hawaiian Isl. and this is probably because there is more food at those depths. This depth shift could be due to human depletion of reef fishes, but it doesn't mean there are 97% fewer sharks, they are just outside their survey area."

Source: KITV.com        

Philippine's Irrawaddy Dolphin: endangered but with a potential future thanks to local fishermen

In the Philippines, the Malampaya Sound is known for its ecological diversity, ranging from coral reefs to sea grasses to mangroves and lowland forests. It is also home to one of the most endangered species of dolphin: the Irrawaddy dolphin. The number of dolphin in the sound has dropped from 79 in 2001 to 42 and scientists believe that if the number dips below 40, the Irrawaddy dolphin population in the sound will collapse.

The Irrawaddy dolphin is a rather cute looking creature; a bit like a small beluga whale with a similar head shape and light grey in color. There are only about 6,000 Irrawaddy dolphins worldwide and it has been listed as "critically endangered" by the IUCN. Because of the Malampaya Sound's biodiversity, commercial and local fisherman have been attracted to the area and the sound is showing the impact of overfishing. No more so than with the plight of the Irrawaddy dolphin which is not commercially sought after but does become ensnared in the longline nets and, being then unable to reach the surface, drowns.

However, there could very well be a positive future for the Irrawaddy dolphin if the indigenous Tagbanua people have anything to say about it. Representatives of the World Wildlife Fund (WWF) who have been monitoring the situation and working with local Philippine officials, say that the Tagbanua tribe have both a cultural history that supports protecting the dolphin and employ fishing techniques that could allow the Irrawaddy dolphin's numbers to return.

“For them [the Tagbauna people], the dolphins are bearer of good tidings and are also the omen of something bad that will happen like typhoons or calamities, depending on the behavior of the animal,” said Mavic Matillano, who lead a study five years ago on the Irrawaddy dolphin. “That, in a way made the lumad [non-Muslim indigenous peoples in Mindanao] also believe that when you hurt a dolphin, something bad may happen to you.”

The cultural position forms the background for their approach to fishing. The Tagbanua fishermen use specific moon and tide schedules and selective harvesting, regardless of market demands, to avoid overfishing and wasted bycatch (which is the category in which the Irrawaddy dolphin finds itself).

According to the Philippine's Inquirer News, "WWF officials said the most important thing to do right now was to change the fishing practices of the coastal communities there. The group and [WWF author Raoul] Cola pointed to the Tagbanua fishing practices as a model of sustainable practice."

“Based on the principle of the interconnection, not only of ecosystems but also of the natural, social and spiritual worlds, these strategies demonstrate that the world view of the users molds their environment and defines the prospect of its sustainability,” said Cola.

The WWF is working with several Philippine agencies to implement commercial fishery management strategies based on the techniques employed by the Tagbanuas. The WWF is working hard to address funding issues, but they are encouraged by that fact that an indigenous Philippine tribe can serve as a model for many local coastal areas, rather than some outside group of "foreigners" imposing their beliefs on local fishermen.

The Irrawaddy dolphin, like other dolphins, is an important apex predator and vital to maintaining a healthy biodiversity in the Malampaya Sound. Let's hope that local wisdom and responsible fishing techniques can spread to ensure the dolphin's future.

Source: Inquirer News

Fiji's Sharks: study shows big business and locals are depleting a tourism and natural resource

Following on the accomplishments of island nations like Palau to establish shark sanctuaries, there is a movement developing to do the same in Fiji. While it has not yet reached the point of actual legislation or regulations for consideration by the Fijian government, it would appear to not be a moment too soon either.

According to a study just completed by Dr. Demian Chapman of the Institute for Ocean Conservation Science, Stony Brook University in New York, shark fishermen are targeting at least 10 species that are listed on the International Union for the Conservation of Nature's (IUCN) Red List. Included are sharks that make up a large part of Fiji's shark eco-tourism operations which contributes to the islands' tourism base.

Working in consort with the Fiji Fisheries Department, Dr. Chapman, who gained scientific recognition for his research in shark DNA that allowed for the tracking of hammerhead fins back to their place of origin, studied two shark fin traders in Fiji and combined his data with that of other researchers to paint an overall disturbing picture of the shark fin trade between Fiji and Hong Kong.

Three species - blue sharks, oceanic whitetips, and the silky shark were being targeted as bycatch from the tuna fisheries. However, one aspect of the study that was of particular concern was the extant to which local fishermen were involved, catching species more commonly found closer to shore. These are the sharks that divers from around the globe come to Fiji to see and so it represents a sizable lost economic value for the shark eco-tourism operators and the islands as a whole.

"I also observed a number of fins from inshore species. According to traders, these come from the coast of Fiji and are collected by local people who are paid by the dealers for shark fins and sea cucumbers," said Dr. Chapman.

This points to one of the major problems with the shark fin trade. While there is a large industrial fishing component that must be combated, there are also locals involved, merely trying to make a living. Like organized crime or the drug trade, these locals are not paid top dollar for their efforts - that's reserved for those further up in the shark fin distribution food chain - but they are tempted to participate as it could mean food on the table in a tough economy (not every Fiji citizen is employed by or benefits from the tourist trade).

And speaking of those further up the food chain, the amount of product that is being moved through Fiji alone is staggering. As reported in The Fiji Times Online, Dr. Chapman said, "I estimated the total number of fins present at each dealer by counting the number of fins visible in digital photographs taken onsite. Since most sharks produce four marketable fins (dorsal, two pectoral and lower caudal), I divided the estimated total number of fins by a factor of four to estimate the total number of individual sharks killed. One dealer had approximately 1000 fins drying, which represents at least 250 sharks killed.

"The dealer also had four large freezers full of frozen fins that were impossible to count. The other dealer had three very large piles of dried fins that I estimate contained a total of 10,000-12,000 fins and represented 2500-4000 dead sharks. The dealer indicated that they were exporting this volume on a monthly basis from Nadi International Airport to Hong Kong."

Twenty-five hundred to four thousand sharks each month, potentially coming from Fijian waters. Fiji's shark species and reef ecosystems can not withstand this kind of harvest.

The Fiji Times Online also quoted Ratu Manoa Rasigatale, who is spearheading an awareness campaign for the Coral Reef Alliance and Pew Environment Group to turn Fiji's waters into a shark sanctuary, '"It is sad to note from Dr Chapman's assessment that locals are heavily involved in the killing of reef sharks,' said Ratu Manoa, dubbed the Sharkman for his efforts to spread the gospel of shark conservation to all levels of the community in Fiji."

The only upside to a report like this is that it represents the kind of factual data needed to support a drive for establishing a shark sanctuary. No moral arguments about finning, no anecdotal evidence or stories of tradition or folklore; just the cold hard facts. Economic facts. Somebody is making a lot of money and it's not Fiji's everyday citizen; and one of the islands' major economic engines - the tourist trade - is at risk. Hopefully, that should catch the attention of government officials who are willing to look at the long-term future of Fiji's economy, its reefs and the sharks that call those reefs and the surrounding waters home.

Read about the shark fin trade in Fiji in The Fiji Times Online.

The Vaquita: Mexico's diminutive porpoise at risk of extinction

From the large and majestic humpback whale, mentioned in yesterday's post, we can travel to the other end of scale: the rare and diminutive Vaquita. Reaching a mere 5 feet in length, the vaquita is a member of the porpoise family and is only found in the northern end of the Sea of Cortez (Gulf of California). And at a scientific meeting of the International Whaling Commission being held in Agadir, Morocco, the findings of a 2008 population study show that there are only approximately 250 vaquitas alive today. As disturbing as that low number may seem, it is even more disconcerting when compared to a 1997 population study that estimated the population to be 567 - a decrease of 55% in just one decade.

The vaquita is similar to other small porpoise species that inhabit deltas and river outlets (one such species in China was considered extinct by 2007). Probably attracted to the shallows of the Sea of Cortez near the mouth of the Colorado River, the vaquita's habitat was impacted by the damming of the river in the U.S.; but researchers do not believe this has been a detriment to the vaquita. What appears to be the primary cause for the vaquita's decline is its tendency to get caught in the gill nets of local fishermen - a tragic victim of bycatch.

The 2008 population study represents the combined efforts of both Mexican and U.S. research groups with additional government support. To conduct the study required an elaborate high-tech version of a common biodiversity technique: to determine basic biodiversity, a transect is used to define an area and then sealife is counted within that area. Doing that several times over a wider area, estimates can then be extrapolated. For the vaquita population, several vessels were used to make large surface transects within which visual sightings and results from hydrophones (which picked up the distinctive clicking sounds made by the vaquitas) were tallied. From that raw data, the current population of 250 was estimated.

Although their primary range is now within a protected reserve, as of 2005, and includes a ban on the use of gill nets; the vaquitas are still very much at risk from illegal fishing. A lack of resources to provide effective enforcement combined with the economic needs of subsistence-level fishermen continue to put the vaquitas at risk. Plans are being considered to introduce fishing techniques that do not use gill nets, but getting local fishermen to abandon their traditional fishing methods will be challenging.

According to Nature News, "A more immediate challenge is to expand the protected area. 'We need to get all the gill nets out of the water,' says Timothy Ragen, executive director of the Marine Mammal Commission in Bethesda, Maryland. But a broader ban would be a difficult economic and political challenge, pitting the vaquita against the livelihoods of local fishermen."

The unique vaquita is one more cetacean that stands at the brink of extinction - not from industrialized commercial fishing or whaling, but from the needs of local fisherman trying to survive. This is dilemma being played out in many other parts of the world.

Read more in Nature News.