B.C.'s commercial spot prawn fishermen have, for the first time, agreed to voluntarily avoid nine prehistoric glass-sponge reefs in the Strait of Georgia during this year's spot prawn fishery.

The scientific community was stunned when glass-sponge reefs, described by the Vancouver Aquarium as the "longest living animals in the world." were first discovered in Hecate Strait in 1987.

Spot prawn fishery

Approximately 2,450 metric tonnes of wild spot prawns are harvested annually in B.C. The fishery begins May 8 and lasts between six to eight weeks. (CBC)

"Prior to the discovery of glass-sponge bioherms in Hecate Strait, these sponge reef structures were thought to have gone extinct more than 60 million years ago,” said Jeff Marliave, vice president of marine science at the Vancouver Aquarium.

Since then they have also been found in the Strait of Georgia.

Marliave says the prehistoric reefs are living sponge growing atop layers of dead sponge structure that provide a complex and unique habitat for fish and other marine life. Some grow to be as high as a five-storey building.

Prehistoric sponges fragile

To date they have only been observed along B.C.'s coast line says Marliave, and they are easily damaged because they are slow growing and like glass, fragile.

Spot prawns tend to inhabit rocky or hard bottoms and favour B.C.'s glass-sponge reefs which makes the reefs particularly susceptible to the lowering of crab and prawn traps or sport fishing gear trolled along the ocean bottom, says Marliave.

Glass-sponge reefs

The other worldly glass sponge reefs were thought to have died out with the dinosaurs until their discovery in B.C.'s Hecate Strait in 1987. (Vancouver Aquarium)

This season, Fisheries and Oceans Canada has secured an agreement that commercial fishermen will not fish near the reefs.

A Howe Sound research team has been identifying and mapping their locations.

Steve Johansen with Ocean Wise partner, Organic Ocean, says the information will be put to good use.

"Effective this year as a condition of licence, prawn-trap fishers must have a GPS-based monitoring system on board that records the vessel location every 15 minutes and records when a fisher sets and hauls in gear," says Johansen.

"The technology can help them avoid the glass sponge reefs, and continue to harvest spot prawns sustainably.

In B.C., approximately 2,450 metric tonnes of wild B.C. spot prawns are harvested annually, with about 65 per cent of the harvest coming from the waters between Vancouver Island and the Mainland.

The harvest season began May 8, and will last anywhere from six to eight weeks.

With files from the CBC's Terry Donnelly