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Dive type : Recreational, Training, Reef
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Visibility: Average
Recent Divers in Sisal, Yucatan
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Data provided by EOL.org
Species Identified
Chelonia mydas Linnaeus 1758 (Green Turtle)
Green turtles are long-lived and may take up to 59 years to reach sexual maturity Undertaking tremendous feats of navigation, adults return to the same beach to breed each season, part of the population in Brazil astonish...
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Green turtles are long-lived and may take up to 59 years to reach sexual maturity Undertaking tremendous feats of navigation, adults return to the same beach to breed each season, part of the population in Brazil astonishingly migrates around 2,250 kilometres across the open ocean to breed on the Ascension Islands . Mating tends to occur just offshore of the nesting beaches; using a curved claw on each front flipper and a flat nail at the end of the tail, males are able to grip their mates . Females haul out onto the beach at night and dig large nests with their back flippers beyond the high tide mark, they typically lay between 100 and 150 eggs in one nest and then proceed to cover the eggs with sand; the whole process takes around two hours . A single female returns to breed only once every two to five years but will lay up to nine nests in that one season . Incubation takes between 45 and 70 days, and temperature has been shown to determine of the sex of hatchlings; with females being produced at warmer temperatures . Breaking open their eggs with a special hooked 'egg tooth' that will subsequently be lost; hatchlings use their powerful front flippers to reach the surface, and then proceed to the sea . The soft-bodied juveniles are particularly vulnerable at this time from a variety of predators, such as ghost crabs and gulls on the beach to sharks and dolphins in the water . Unlike other marine turtles, adult green turtles are almost exclusively herbivorous, grazing on seagrasses and algae ; it is assumed that juveniles are more omnivorous although the exact composition of their diet is unknown
Ginglymostoma cirratum (Bonnaterre, 1788) (Nurse shark)
During the day the nurse shark is a sluggish animal, spending most of its time resting on sandy bottoms, or in crevices in rocks and coral reefs. Often several nurse sharks may congregate when resting, sometimes even pili...
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During the day the nurse shark is a sluggish animal, spending most of its time resting on sandy bottoms, or in crevices in rocks and coral reefs. Often several nurse sharks may congregate when resting, sometimes even piling on top of one another . At night however, the nurse shark actively roams the sea bottom and reef for prey. It feeds on bottom invertebrates such as spiny lobsters, shrimps, crabs, sea urchins, squid and octopi . It is also feeds on fish, its nocturnal nature enabling it to prey on resting fish that would be too active during the day to capture . The nurse shark's small mouth and large pharynx enable it to feed by a unique suction method, effectively making the nurse shark the 'hoover' of the ocean floor. By cupping its mouth over a hole or crevice and expanding its throat, it creates a vacuum that sucks prey out of their hiding . This suction-feeding is also useful for extracting snails from their shells , and it will dig in sand to root out prey sensed by its fleshy barbels . The nurse shark is one of few sharks in which courtship behaviour is relatively well known . The male swims alongside the female, grabs one of the pectoral fins in his mouth, rolls her over and they mate . A large number of males will often try to mate with a single female, and females often bear numerous bite-scars and bruises received during mating attempts. It is therefore not surprising that females frequently try to avoid males by swimming in very shallow water, where they can bury their pectoral fins in the sand . Nurse sharks are ovoviviparous , a method of reproduction whereby the young develop inside a weakly-formed egg shell within the mother, receiving nourishment from their yolk sac, for five to six months . The females move to shallow seagrass beds and coral reefs to give birth to 20 to 30 pups in late spring and summer . Like many sharks the nurse shark is slow growing, with males not reaching maturity until 10 to 15 years of age, and females 15 to 20 years .
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Nando
Mexico
Date: 2012-05-27 - 11:00
Max Depth: 12m Duration: 55mins
Dive buddies:
Wim Deputter
Arrecife Sisal a 23 km del puerto de Sisal, tambien conocido como 3.30 o bajo de 10