Zebrasoma Flavescens - Yellow Tang

Coral reefs are some of the most exquisite and beguiling habitats on Earth. These teaming ecological societies play host to a myriad of vibrant marine species, from crustaceans and small fish to reef sharks and turtles. Amidst this hectic and heavenly environment, every creature has its own, fascinating secrets - and they're just waiting for mankind to discover them.

With its lurid yellow scales, the Yellow Tang blends into its alluring and effervescent environment with ease. They can grow to sizes of 20 centimetres in diametre, excluding their elongated snout and pectoral fins. Yellow Tangs possess large dorsal and anal fins which are slightly thinner than their actual body, which in itself is extremely fine. At the join between the Tang's oval body and triangular tail, there is a distinctive white spine - known as a scalpel, on account of the Tang's membership to the Surgeonfish family. This aptly-named scalpel is the Tang's greatest defence against predation - it can launch this at a predator in order to inflict it a grave injury. Young Tangs' spines are also poisoned, making them even more potent than those of older specimens. Since all Tang, not just Yellows, are territorial fish, these scalpels are of paramount importance.

Yellow Tang prefer sub-tropical, coastal waters with temperatures of around 21 degrees Celsius. They are found in abundance on the coral reefs of Hawaii, Micronesia, Palau, the Philippines, Japan, Hong Kong and Vietnam at depths of between 2 and 46 metres.

For reef fish, Yellow Tang are fairly long-lived - able to endure for around 30 years in the wild, although most do not survive past 10 years of age when held in captivity. These vibrant marine creatures reach sexual maturity at the age of around 2 or 3.

Yellow Tang reproduce externally, either in groups or in pairs. Group spawning occurs frequently, with large groups of females releasing their eggs and males releasing their sperm over a small area. Occasionally, Yellow Tang will mate with a partner; a male and female Tang will swim parallel to each other vertically, simultaneously releasing their eggs and sperm into the water. This act, unlike group spawning, is preceded by courtship, during which the male will attempt to attract a passing female by exhibiting his size and vibrance. Females release up to 40,000 eggs during a single spawning session and will reproduce once a month over a period from from March to September. Males, meanwhile, will mate several times and with several different females during a single spawning session.

Yellow Tang are of great importance to the coral reef ecosystem, as they feed on coral-constricting algae - limiting its growth across a wide area. Some Tang will also graze upon zooplankton, although their forty teeth are better suited to the consumption of algae and seaweed.

Generally speaking, people think of reef fish as being virtually immune to the threat of humanity, since they are hunted neither for sport nor for food. This, however, is a great misconception. Human encroachment into coral reefs causes great habitat destruction, as does the use of explosives to harvest game fish. Larger numbers of Yellow Tang are captured for aquariums and private fish tanks than any other tropical or subtropical fish, causing a vast decrease in their natural population. This is also a cause of great devastation to the coral reefs themselves, since a lack of Yellow Tang and other reef fish gives constrictive algae more time to grow over the coral - consuming it and gradually causing the entire environment to deteriorate. This is the extent to which food chains have an effect on their ecosystems - the removal of one single, vital link can result in complete and utter destruction.

Bibliography

http://animaldiversity.org/accounts/Zebrasoma_flavescens/

http://freefishfacts.com/the-yellow-tang/

http://www.iucnredlist.org/details/178015/0

Daniel Bailey

Sunday 7th of February 2016, 16:24 GMT

England

Dedicated to Beth at London Sea Aquarium - thank you for being a wonderful teacher; I will never forget all you taught me.

Prionace Glauca - Blue Shark

Slender, agile and skilled in the hunt, the Blue Shark is the epitome of the pelagic predator - one of the most divine and glorious creatures to grace the oceans of our blue planet.

Reaching lengths of 3.8 metres and attaining weights of up to 200 kilograms, Blue Sharks are one of the larger species in the requiem shark family. As is evident, their name derives from the magnificent indigo pigmentation on their backs, which fades into a white on its underbelly as camouflage from above and below.

Blue Sharks are easily identifiable by their large, round eyes and distinctive, streamlined or cigar-shaped figure. It possesses an elongated snout, at the end of which are the usual five gill-slits found in more recently evolved shark species. Beneath these are a pair of long, pointed pectoral fins, which, as with the rest of the shark's body, are white on the underside and indigo-blue on top. Unlike many sharks, the dorsal fin of the Blue Shark is closer to its pelvic fins than to the pectoral fins. An anterior, or second, dorsal fin is situated close to the tail, or caudal fin. This same caudal fin has a longer dorsal, or upper, lobe than ventral, or lower, lobe, the former accounting for up to a quarter of the shark's body length. An anal fin is present on the underbelly, between the pelvic fins and caudal fin. As with all requiem sharks, nictitating, or inner, eyelids distinguish them from the family of mackerel sharks. These tough membranes close over the eyes during the last few seconds of a hunt or attack, shielding the eye from any damage its prey might attempt to inflict upon it.

As an ocean-dwelling, pelagic shark species, Blue Sharks are generally only found in open water, where they are a frequent menace to anglers and long-line-fishermen, stealing fish from their lines in an opportunistic fashion. Blues only inhabit waters between the temperatures of ten and twenty degrees Celsius, so despite being found in all of Earth's oceans - with the exception of the Southern and Arctic Oceans - and many of its warmer Seas, such as the Mediterranean Sea, Caribbean Sea and the Gulfs of Mexico and California, specimens tend to remain at depths of around 400 metres. Only in colder parts of the Global Ocean, such as the North Atlantic, the North Sea and the North Pacific, can they be found closer to the surface. Atlantic Blue Sharks undertake vast, trans-Atlantic migrations with great frequency, following the Gulf Stream from the United States of America to the United Kingdom, the Canary Current from the United Kingdom to West Africa and the North Equatorial Current from West Africa to the Caribbean and back on to the United States. Some sharks have been known to deviate from this common course, using the North Atlantic Drift and the Labrador Current to circle from the United Kingdom to Iceland and back to the United States. Blues in other areas, such as the Indian and Pacific Oceans, make similar migrations in their own waters. During this time, the sharks remain in small, single-sex schools, with larger specimens dominant over smaller and younger Blues.

Provided the evade death at the hands of human hunters and at the jaws of larger predatory animals, Blue Sharks can live for up to 20 years, reaching sexual maturity at around 6 years of age. Blue Shark mating takes places in the open ocean and at great depths, meaning marine biologists know little about its course. It is believed, however, that male sharks will bite females as an act of courtship, inflicting little damage due to the thickness of the female sharks' skin - three times that of a male's.

Following mating, a gestation period of roughly one year takes place before the female gives birth to a litter of pups numbering from 4 to 135. These young sharks spend the first few years of their life closer to shore, undertaking migrations at later ages.

As with the majority of pelagic sharks, Blue Sharks are scavengers and opportunists - consuming fish from lines and nets as well as human refuse left in the sea. Whale, porpoise and dolphin carcasses attract large numbers of Blues as well as other species of sharks and fish. Occasionally, large congregations of Blues will go into the infamous feeding-frenzy in competition over such an opportunity. Large schools of mating squid and of schooling mackerel can also send specimens into a similar state, although for the most part the sharks will work together to herd prey towards the surface before attacking. Should a Blue Shark come across a large food source, it will feed incessantly - ejecting previously consumed food through the mouth in order to continue feeding. This trait is not endemic to Blue Sharks, although it is best observed in them.

To the sadness of biologists and conservationists alike, Blue Sharks,once the most abundant shark species, are drawing closer to classification as an endangered species. An estimated 20,000,000 Blue Sharks are caught and killed each year, primarily for the shark-fin soup industry in Eastern Asia. Drift nets and trawler nets also pose terrible threats not only to Blue Sharks but to all pelagic marine life, and it is these nets which are targeted for illegality by conservation groups such as SharkTrustUK and Shark Savers in America. As Blue Shark numbers decrease, it is humanity's duty to act now, and save our beloved marine ecosystem from the brink of extinction.

Bibliography

http://www.sharktrust.org/shared/downloads/id_guides/blue_shark_st_id_guide.pdf

http://www.sharksavers.org/en/about/successes/

http://www.sharksider.com/blue-shark/

http://www.iucnredlist.org/details/39381/0

http://species-identification.org/species.php?species_group=sharks&id=471

https://www.flmnh.ufl.edu/fish/education/questions/biology.html#membrane

Jonathan Bird's Blue World, Season One, Episode One, Blue Shark Adventure

Page 183, The Nature Company Guides; Sharks & Rays, The Nature Company Guides, Time-Life Books, 1997

Page 93, The Nature Company Guides; Sharks & Rays, The Nature Company Guides, Time-Life Books, 1997

Page 15, A Very Short Introduction: Marine Biology, Philip B. Mladenov, Oxford University Press, 2013

Page 24 - 25, Encyclopaedia of Sharks, Sally Morgan, Igloo Books Ltd, 2010

Daniel Bailey

Sunday 7th of February 2016, 14:19 GMT

England

Dedicated to Ron and Valerie Taylor - my inspiration.

Chelonia Mydas - Green Sea Turtle

Few creatures embody the spirit of the oceans to such an extent as the turtle; a graceful, gentle, glorious creature, drifting at the whim of the tides and currents. These marvellous beasts are some of nature's finest creations - the physical personification of beauty.

Green Sea Turtles are amongst the most well known sea creatures, growing to lengths of 1.5 metres and amassing weights of up to 240 kilograms - making them the second-largest species of the turtle family.

A common misconception concerning the green sea turtle is the etymology of its name; whilst many would assume that the species derives its name from the colouring of its shell, this is, in fact, false. Green Sea Turtle shells range in colour from the famous olive green to darker shades and even the idiosyncratic black-shelled specimen. Their name is in fact derived from the green pigment of the fat beneath its shell, otherwise known as the subdermal body fat. Thus, the Pacific Black Turtle is actually a misidentified variation of the Green, the darker colouration of its shell being the only differentiation between the two.

 As with almost all turtle species - Leatherback Turtles being the only exception - the Green Sea Turtle is possesses a hard carapace, or shell, comprised of large scutes, or shell plates. These scutes are arranged with four costal, or lateral, plates along the edges of the shell. Another important feature, endemic to Green and Flatback Turtles, is the number of prefrontal scales - the scales found in front of its eyes. Whilst the majority of turtle species have two pairs, only one pair is present in the aforementioned species. This leaves the Green Sea Turtle appearing almost identical to the Flatback Turtle, but with one final differentiation: a Green Sea Turtle's carapace is oval and smooth, the Flatback Turtle's has slightly upturned edges - a distinct differentiation. Green Sea Turtles colourations, as described before, range from olive green to brown and black on the carapace, with green subdermal body fat and a pale yellow plastron, or underside.

One of the more widely-distributed turtle species, Green Sea Turtles can be found inmost tropical waters, such as the Caribbean and Mediterranean Seas as well as the Atlantic, Indian and Pacific Oceans. Over eighty countries host turtle nesting beaches, which are frequented between three and five times a year between pelagic migrations. Generally, Green Sea Turtles will remain in coastal areas - although females often make vast migrations to nesting sites, with one known group of turtles travelling an immense 2,300 kilometres from the coast of Brazil to the South Atlantic Ascension Island.

Provided they evade death at the hands of human hunters or the jaws of marine predators, Green Sea Turtles, as with the majority of turtle species, can live for up to 100 years. Despite this longevity, however, Green Sea Turtles take between 20 and 50 years to reach sexual maturity. This, combined with the minute survival rate of hatchlings, results in wavering reproduction rates - greatly worsened by the presence of hunters and egg-stealers in coastal areas and on nesting beaches.

Green Sea Turtles reproduce at spasmodic intervals; females reproduce only every two or three years, nesting between three and five times per nesting season and laying in each nest an average of 115 eggs, which incubate for 60 days under the sand of ancestral nesting beaches. Turtles will always return to the nesting beaches upon which they hatched, which makes migration tracking far easier for marine biologists with satellite tags.

As juveniles, Green Sea Turtles consume a wide array of plant and animal life, ranging from seagrass to crustaceans, jellyfish and squid. In adulthood, specimens tend to become herbivores, surviving off of seagrass and algae. Some adult turtles have been known to prey on squid and jellyfish as well, although this is not the general pattern.

Tragically, Green Sea Turtles, as with a myriad of marine species, are endangered due to human interference in their habitats. Seagrass destruction jeopardises their food chains, whilst construction on nesting beaches often destroys eggs and prevents females from nesting. A rapidly expanding demand for turtle shells is yet another example of human greed driving nature into extinction. This, combined with the natural fluctuation in Green Sea Turtle reproduction, brings them dangerously close to the brink of the mire of extinction - a predicament from which they must be rescued at all costs.

Bibliography

https://www.nwf.org/Wildlife/Wildlife-Library/Amphibians-Reptiles-and-Fish/Sea-Turtles/Green-Sea-Turtle.aspx

http://www.seeturtles.org/green-turtles/

http://www.conserveturtles.org/seaturtleinformation.php?page=green

http://seaturtlesofindia.org/?page_id=12

http://animals.nationalgeographic.com/animals/reptiles/green-turtle/

Daniel Bailey

Sunday 7th of February 2016, 11:09 GMT

England


Dedicated to Beth, Andrew, Lauren, Sanye, Demy and Claire at London Sea Aquarium - thank you for reminding me how much I loved marine biology.

Marine Secrets

We know more about the surface of the moon than we do about the seabeds of the oceans.

Today, this fact is common knowledge. Few, however, appreciate its absurdity; the moon in question is 384,400 kilometres away through the vacuum of space, while the oceans have sat upon our doorstep since humanity's arrival on Earth some 200,000 years ago.

For centuries, we have had the technology to explore the oceans - in 1715, the French Chevalier Pierre Remy de Beauve invented the first underwater breathing apparatus, while in the same year, the English wool merchant John Lethbridge successfully developed a diving barrel, which he used to salvage valuables from shipwrecks. Only 61 years later, in 1776, the American David Bushnell invented the submarine, the first of which, christened the Turtle, although used for the purpose of naval warfare during the American Revolution, was perfectly capable of pelagic exploration.

Only in the last 55 years, however, has man developed the technology to voyage into space - Soviet cosmonaut Yuri Gagarin undertaking the first manned space flight on the 12th of April 1961.

Even today, a myriad of marine species await discovery. Vast swathes of oceanic landscape remain to be mapped. Unfathomable amounts of knowledge are yet to be understood.

Marine Secrets' purpose is to give a little knowledge on our most unexplored environment - to form the basis of knowledge for those who aspire to explore the unknown, to delve into the depths of a new, blue world.


Daniel Bailey
Monday 8th of February 2016, 21:22 GMT
England