Friday, May 2, 2008

Wonderous Whip Morays


Studying Bermuda's Own Spotted Eagle Rays

A BZS-supported graduate research project undertaken in 2006, 2007 and again this summer by Matt Ajemian, a student at the U. South Alabama, Marine Science Dept, and the Dauphin Island Sea Lab's Fisheries Lab

Project Context
The spotted eagle ray (Aetobatus narinari), locally known at the “Whip Moray”, is fairly abundant over seagrass beds and sand flats of Bermuda. The Government of Bermuda has expressed interest in placing spotted eagle rays on the Protected Species List – however insufficient information of their population status and ecology has prevented any such action. The urgency for A. narinari data has become critical as they are potential predators of conch and scallops, both of which are also undergoing restoration from overharvest in Bermuda. Rapid population increases of other rays in North America (Science journal pdf) demonstrate that rays can impact shellfisheries quickly - highlighting the need for understanding the ecology of spotted eagle rays in Bermuda as soon as possible.


Matt (right) and "Flookie" (right) prepare an Eagle Ray for tagging with a tracking device


Objectives
In conjunction with Dr. Thad Murdoch (BZS) and Chris Flook and his team (BAMZ), PhD student Matt Ajemian (DISL, University of South Alabama) is trying to understand the ecological role of Bermudian spotted eagle rays. Matt is from Long Island, New York, and has been interested science, and in particular the biology of sharks and rays since a very young age. He studied the feeding behaviour of deepwater chain catsharks as part of his Masters degree at Hofstra University and studies the foraging ecology of cownose rays in the northern Gulf of Mexico.

Specific objectives include:

  • Determining populations size across Bermuda
  • Assessing their diets, foraging behaviour and motion across Bermuda using ultrasonic tracking transmitters and datalogging hydrophones.
  • Measuring the ecological role and impact of eagle rays on shellfish stocks

Recent Findings
Since May of 2007, the research team has captured, photographed and measured 13 spotted eagle rays, all of which were released harmlessly back into their native environment. Key findings include:

  • Acquisition of basic biological information on these animals (size, sex, maturity state, food habits)
  • Tracked the movements of eagle rays throughout Harrington Sound and Flatts for 2 months, to show possible aggregation areas and residency within HS

Implications
Spotted eagle rays are probably slow-growing, late-maturing species that produce few pups per litter. These reproductive parameters make spotted eagle rays vulnerable to exploitation. Our continued work on this charismatic and potentially ecologically important species will provide critical data for conservation purposes while bringing information on living resources to Bermuda’s public eye.