Among the stranded turtles found on the country's southeast beaches were leatherbacks, a critically endangered species, the group said.
"The entire coast has historically been a significant nesting area for olive ridley and leatherback sea turtles," Colum Muccio of the Wildlife Rescue and Conservation Association told Mongabay.com.
Concerned Guatemalan citizens founded the non-profit group in 1989.
"We manage two of the 24 hatcheries on the Pacific Coast of Guatemala, and carry out research and advocacy for sea turtle conservation," Muccio said.
The appearance of dead turtles on area beaches coincides with the presence of shrimp trawlers in waters off these beaches, the conservation group said in a statement.
"I don't think it's a coincidence that when shrimp trawlers appear in the ocean that we begin having stranded turtles," Muccio said.
"We are currently working on instituting a ban on bottom trawling," he said. "This has recently been done in Belize, Costa Rica and Ecuador, and El Salvador doesn't allow them closer than 3 miles from shore."