Endangered rays may have unknown birthing zone in Mexican waters

phys.org | 4/23/2019 | Staff
bungienet (Posted by) Level 3
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The discovery of dozens of pregnant giant devil rays accidentally caught in fishing nets in a village along Mexico's northern Gulf of California could mean the endangered species has a previously unknown birthing zone in nearby waters, a new Duke University study suggests.

If further research confirms the possibility, authorities and local fishers should work together to devise a plan that minimizes the risk of negative interactions when pregnant rays migrate there each year in and around April, said study author Leo Chan Gaskins, a doctoral student in marine science and conservation at Duke's Nicholas School of the Environment.

Animals - Maturity - Pup - Litter - Number

"These animals reach sexual maturity very slowly and they have only one pup per litter, so losing even a small number of pregnant females to by-catch can have dire effects on a local population's birth potential and long-term survival," Gaskins said.

The largest of the ray species, giant devil rays (Mobula mobular) can grow to 17 feet long and are known for their acrobatic leaps and deep dives. Large numbers of them are caught and killed as accidental by-catch each year when they become entangled in fishing nets while foraging for krill and other prey in shallow tropical and subtropical waters.

Population - Size - Movement - Patterns - Zones

"We still know very little about their global population size, annual movement patterns and reproductive zones, so the discovery and protection of a previously unknown pupping ground would be good news for conservation," Gaskins said.

He published his peer-reviewed paper April 23 in the journal Ecology.

Field - Course - Marine - Conservation - Gulf

While taking a field course on community-based marine conservation in the Gulf of California as a Duke undergraduate in April 2014, Gaskins observed dozens of dead giant devil rays tangled in gillnets on the beach of a small-scale fishing community in northern Sonora. Because of the animals' immense size and weight, the fishers were unable to return them to the...
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