video transcript

In the Gulf of Mexico, the world's biggest fish are having a whale of a time. Hundreds of whale sharks have arrived for their annual summer congregation off the Mexican coast of Isla Mujeres. The enormous fish come to feed in the coastal waters during the months of June, July and August. Marine biologist Rafael de la Parra says some 250 whale sharks have been seen so far this season, a positive sign for a species listed by conservation groups as "vulnerable" SOUNDBITE: Rafael de la Parra, lead marine biologist for Project Domino, saying (Spanish) "Comparing the fact we have this large amount of animals in this area of whale sharks, something to note is that in other places, there are a lot of young males, or a few females and a few males but here we have males, females, youngsters, older whale sharks, pregnant females, so we have to look after this. It's an area where they aggregate to mainly feed but it's probable, due to the great number of animals, sexes, and social components, there could be another type of activity, namely the reproductive one, why not?" The whale shark is a gentle giant of the ocean. It's not dangerous to humans, and can live between 60 and 150 years. Whale sharks have been recorded up to 14 metres in length, and can weigh up to 15 tonnes. Scientists say the increased sightings have provided new insight into the whale shark's behavioural patterns. SOUNDBITE: Rafael de la Parra, lead marine biologist for Project Domino, saying (Spanish) "We can't still talk about a migration route. We originally thought that they were migrating from south to north because the main season in Honduras is around April. Then between May and June, they are most seen in Belize and we are seeing them here in May, June, July, August and September. Afterwards, further north in the Gulf of Mexico, they are seen in Autumn. We thought it was a route from south to north, but today, thanks to the incorporation of real-time and file satellite trackers, we know these animals are really going around making a figure eight, looking for food that is where they group, to make the most of it." The whale sharks have also become a major tourism draw-card, with tour companies offering the adventurous a chance to swim alongside the giant sea creatures. SOUNDBITE: TRIXIE DE LEON, TOURIST, SAYING (ENGLISH) "It was nice to be able to be so close to it, it's not like in a zoo where you have to be far away, you actually get to swim close to them." But with that, comes risk. Tour operator John Vater says the biggest threat to whale sharks is careless ship operators. SOUNDBITE: John Vater, owner of Ceviche tours, saying (English) "The main risk for whale sharks in this area are large ships, ship strikes and the propellors of boats. That is the primary risk that the whale sharks have in the area around Isla Mujeres and north. The passage of vessels, they need to take care in this area to not hit whale sharks, that's their major enemy, boat propellers." Each July, supporters try to raise awareness of the giant sea creatures with the annual Whale Shark Festival. Given their numbers this year, the sharks are only too happy to take part. Gemma Haines, Reuters.