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Temp: Surf 32°C Bottom 27°C
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Dive type : Recreational, Reef
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Visibility: Good
Water: Salt
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Data provided by EOL.org
Species Identified
Sphyrna lewini (Griffith and Smith, 1834) (scalloped hammerhead)
Forming impressively large schools, female scalloped hammerheads gather in the Gulf of California during the day, around underwater mountains known as seamounts, where they perform a wide range of poorly-understood behavio...
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Forming impressively large schools, female scalloped hammerheads gather in the Gulf of California during the day, around underwater mountains known as seamounts, where they perform a wide range of poorly-understood behaviours . These aggregations are thought to be a result of many sharks, particularly younger females, seeking refuge in a safe place near a rich food supply, although many alternative theories have been put forward . Young scalloped hammerheads also tend to live in large schools, whereas adults usually occur singly, in pairs, or in small groups . These sharks feed on fish, cephalopods, lobsters, shrimps, crabs, other sharks, and rays. They are thought to be potentially dangerous to humans although few attacks have been recorded . The teeth of the scalloped hammerhead are best suited to seizing prey that can be swallowed whole, rather than ripping into larger prey. The hammer-shaped head is thought to be a mechanism to spread out the ampullae of Lorenzini – sensory organs that detect electric currents, chemicals in the water, and temperature changes . Larger shark species may attack young scalloped hammerheads, but adults have no natural enemies. Adults visit cleaning stations where fish known as cleaner wrasse remove parasites from their skin and mouths . During the 9 to 10 month gestation, the eggs of the scalloped hammerhead hatch inside the body of the female. After hatching, but before birth, they are nourished by a yolk sac placenta. The female moves to shallow waters during the summer where she will give birth to between 15 and 31 live young .
Alopias vulpinus (Bonnaterre, 1788) (Common thresher shark)
The thresher shark is an active strong-swimming fish that is occasionally seen leaping out of the water . It feeds primarily on small, schooling fish, but also fish that dwell on the ocean bottom, squids, octopi and, very...
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The thresher shark is an active strong-swimming fish that is occasionally seen leaping out of the water . It feeds primarily on small, schooling fish, but also fish that dwell on the ocean bottom, squids, octopi and, very rarely, seabirds . It uses its unique tail fin to herd fish together in tight shoals, and then stuns them with powerful swipes of the tail. Sometimes two threshers may cooperate in their attack, swimming round the school of fish in ever decreasing circles, then striking the shoal with their tails before turning to swallow their stunned or dead victims . Thresher sharks possess some remarkable physiological adaptations which explain their strength and endurance in a wide range of latitudes and depths. Along each of their flanks runs a strip of red muscle, which can contract powerfully for long periods, enabling the thresher shark to swim for long periods without fatigue . In addition, this red muscle contains a meshwork of tiny blood vessels which transfer heat back towards the body core. Retaining body heat enables the shark to remain active and react quickly even in cold water , and also results in much faster digestion, enabling it to feed again rapidly, should the opportunity arise . Thresher sharks are ovoviviparous, meaning that the young develop inside a weakly formed shell within the female. The gestation period is reported to be nine months, with litters of two to seven pups born during the spring . Thresher sharks reach maturity at between three and eight years old, and are estimated to live for 45 to 50 years .
Sphyraena lucasana Gill, 1863 (Barracuda)
Eretmochelys imbricata (LINNAEUS) 1766 (Hawksbill Turtle)
Hawksbills may take decades to mature and it could be between 20 to 40 years before they are ready to breed . Upon reaching sexual maturity, a female will typically lay up to five clutches of around 100 to 140 eggs in one ...
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Hawksbills may take decades to mature and it could be between 20 to 40 years before they are ready to breed . Upon reaching sexual maturity, a female will typically lay up to five clutches of around 100 to 140 eggs in one breeding season, and then wait a few years before nesting again . Nesting is much more dispersed than in other marine turtles, but individuals do tend to return to a particular beach season after season . Having survived the dash to the sea, hatchlings are believed to spend their first few years in the open ocean before returning to more sheltered coastal waters. Recent studies indicate that the oceanic phase may be shorter for hawksbills, or even omitted in certain regions, as hatchlings swim less vigorously than those of other species . Probably less than one out of 1000 eggs will survive and reach adulthood . Adults are opportunistic predators, using their sharp beak to prize invertebrate prey from crevices within the reef. Unusually amongst marine animals , sponges make up the majority of the hawksbill's diet .
Carcharhinus longimanus (Poey, 1861) (Oceanic white-tip shark)
The diet of the oceanic whitetip shark primarily consists of bony fishes such as tuna and mackerel, but also includes stingrays, sea turtles, sea birds, squid, crustaceans, mammalian carrion , and occasionally even rubbish...
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The diet of the oceanic whitetip shark primarily consists of bony fishes such as tuna and mackerel, but also includes stingrays, sea turtles, sea birds, squid, crustaceans, mammalian carrion , and occasionally even rubbish that is disposed in the sea . The species is usually solitary, but will occasionally congregate in groups during 'feeding frenzies' where food is plentiful , such as around whale carcasses . However, if other shark species are encountered competing for the same food source, the oceanic whitetip shark usually dominates over them, and may become aggressive . This shark is often accompanied by remoras, dolphin fishes and pilot fishes, and reportedly demonstrates an unusual association with the shortfin pilot whale (Globicephala macrorhynchus) in Hawaiian waters . Although the exact reason for this shark swimming along with pods of pilot whales is unknown, it is suspected that oceanic whitetip sharks are following them to sources of squid, which the pilot whales are extremely efficient at locating . This species mates during the early summer in the north-western Atlantic and the south-western Indian Ocean, and females give birth to 1 to 15 live young approximately a year later . Reproduction is viviparous, with live young being born after being nourished by a placental yolk-sac that is attached to the uterine wall by umbilical cords . Sexual maturity is attained at an age of six to seven years for both sexes .
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Clive Temple
Egypt
Date: 2017-07-18 - 12:19
Max Depth: 39.8m Duration: 49mins
