Since the 1920s, fishermen have congregated at Gladden Spit on the Belize Barrier Reef to harvest mutton snapper and grouper during the ten-day period around full moon during the months of March to June. The fishermen often landed huge catches, and many of the fish were gravid (carrying eggs). Often the men noticed huge whale sharks swimming nearby, usually surrounded by a milkiness in the water.
In 1997, a team of scientists and local fishermen found that the snappers came together to spawn, filling the water with milky eggs and sperm, and that the whale sharks -- filter feeders -- had come to eat the eggs -- a combination of events that is both biologically important and thrilling.
Some local tour operators from Placencia, the closest village to Gladden Spit, soon discovered the tourism potential of the predictable presence of whale sharks, and a new industry quickly grew up.
In 2001, the site of the whale sharks was declared a protected area, Gladden Spit and Silk Cayes Marine Reserve (GSSCMR). In 2002, a local NGO called Friends of Nature signed a Memo Of Understanding with the Government of Belize to co-manage the Reserve.
Friends of Nature has studied the spawning fish every month for years. We send a team of divers to the site twice a day for at least 10 days after the full moon. We have round that over 20 different species of reef fishes that come together at the site each with its own month, and moon-timing, a biological clock. Friends is particularly concerned about the snappers.
Mutton snappers are the most common commercial fin fish harvested in Belize. They appear from March to June, during the same months as the cubera snappers and dog snappers. The latter two species produce particularly large, tasty eggs, which seems to be one of the primary motives for the presence of the whale sharks.
FoN also manages whale shark tourism at Gladden, with direct input from a whale shark working group made up of national stakeholders. A set of guidelines to ensure a safe and ecologically-sound experience for everyone, including the sharks, has been developed.