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Marine Resources


June 2012 Issue

1st Satellite Study of Manta Rays Reveals Species' Habitats
A research team attached satellite transmitters to six manta rays off the coast of Mexico's Yucatan Peninsula, tracking them in the first satellite tag study of the species. The manta rays, which included four females, one male and one juvenile, traveled more than 1,100 kilometers in 13 days.

Scientists from the Wildlife Conservation Society, the University of Exeter (UK) and the government of Mexico published their findings in May in PLoS One. The team found that the manta rays spent nearly all their time in Mexico's territorial waters (within 200 miles of the coastline), but only 11.5 percent of the locations gathered from the tagged rays occurred within marine protected areas. And the majority of ray locations were recorded in major shipping routes in the region, indicating manta rays could be vulnerable to ship strikes.

Manta rays, which are listed as a vulnerable species by the International Union for Conservation of Nature, are apparently declining in the Caribbean and other tropical regions, in part because they are captured for shark bait and in demand for their gill rakers (small, finger-like structures that filter out the ray's zooplankton prey) in the traditional Chinese medicinal trade, the Wildlife Conservation Society said.

SeaSketch Prepares for Launch After $500,000 Gift From ESRI
Researchers at the University of California, Santa Barbara's (UCSB) Marine Science Institute (MSI) are finalizing SeaSketch, the next generation of MarineMap, a free Web-based marine mapping and spatial planning program developed in 2009.

SeaSketch scientists received a $500,000 gift from ESRI (Redlands, California) to fund the updated tool, UCSB announced in May.

'We wanted to do this in such a way that it results in conservation benefits in places like the Galapagos, or New Zealand, or Madagascar,' said Will McClintock, project scientist at MSI. 'So the half-million dollars does that. Not by itself, but it allows us to leverage additional funds.'

Shortly after receiving funding from ESRI, the MSI researchers received a call from an official in the Department of Conservation in New Zealand who asked for a customized SeaSketch program for the country, which has a mandate to set up ocean conservation areas throughout the entire exclusive economic zone.

The researchers hope to launch the application in August, about the same time that New Zealand will be unveiling its marine spatial plan in the Hauraki Gulf. Designed to be accessible to those without GIS training, the application will be launched first in New Zealand, but anyone will be able to access it and define study regions.

'Objective science and its criteria tell you right after you've drawn the plan how well it meets science and policy guidelines, and what the economic impact will be to fisheries,' McClintock said.

The prime minister of the Cook Islands has also asked MSI to help create a plan covering a 1-million-square-kilometer marine park that's been proposed for the South Pacific country.

Study Finds Prey Distribution, Not Biomass, Key to Food Chain
A study has found that each step of the marine food chain is clearly controlled by the trophic level below it—and the driving factor influencing that relationship is not the abundance of prey but how that prey is distributed.

Ocean 'patchiness' is not a new concept, but it may have been under-appreciated in importance, as scientists are now increasingly using technologies such as sonar and acoustics to study animal behavior patterns, said Kelly Benoit-Bird, lead author of the study, which was published in May in Biology Letters. In the past, ecologists have primarily used biomass to understand the food chain.

While studying krill in the Bering Sea, researchers used acoustics to study the species behavior and found the distribution of krill was not uniform. This explained why two colonies of fur seals and seabirds were faring poorly, but a third was healthy.

'The amount of food near the third colony was not abundant,' Benoit-Bird said. 'But what was there was sufficiently dense—and at the right depth—that made it more accessible for predation than the krill near the other two colonies.'

While studying the Bering Sea, researchers found they could also use sonar to plot the dives of thick-billed murres, which plunge to 200 meters below the surface for krill. Although the krill were spread throughout the water column, the murres ended up focusing on areas where the patches of krill were the densest.

US Researchers Search for Cause Of Asian Tiger Shrimp Invasion
The recent rise in sightings of non-native Asian tiger shrimp off the U.S. Atlantic and Gulf of Mexico coasts has NOAA and U.S. Geological Survey (USGS) scientists working to determine the cause of the increase and the possible consequences for native fish and seafood in those waters. Reports of Asian tiger shrimp rose tenfold in 2011, NOAA said in April.

Government researchers are working with state agencies to look into how this species from Indo-Pacific, Asian and Australian waters reached U.S. waters, and what the increase in sightings means for native species.

The research will examine shrimp collected from the Gulf and Atlantic coasts to look for subtle differences in the shrimps' DNA, which could offer clues to their origin. This is the first look at the genetics of wild Asian tiger shrimp populations in this part of the U.S.

The cause of the rapid increase in sightings remains uncertain, NOAA said. The shrimp may have escaped from aquaculture facilities, although there are no longer any known Asian tiger shrimp farms presently operating in the United States. It may have been transported in ballast water from ships or possibly arrived on ocean currents from wild populations in the Caribbean or other locations.

Scientists have not officially deemed the Asian tiger shrimp 'established' in U.S. waters, and no one is certain what triggered the recent round of sightings. With many alternative theories about where these shrimp are coming from and only a handful of juveniles reported, it is hard for scientists to conclude whether they are breeding or being carried in by currents.


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