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43-451: John Dory , St Pierre , or Peter's fish , refers to fish of the genus Zeus , especially Zeus faber , of widespread distribution. It is an edible demersal coastal marine fish with a laterally compressed olive-yellow body which has a large dark spot, and long spines on the dorsal fin . Its large eyes at the front of the head provide it with binocular vision and depth perception, which are important for predators. The John Dory's eye spot on

86-576: A 17th-century song about a sea-captain, John Dory. Etymologies claiming it comes from the French jaune dorée (meaning "golden yellow") which sounds like 'John Dory' in English, or the Italian gianitore 'janitor' are now rejected. A legend says that the dark spot on the fish's flank is St. Peter's thumbprint. In the north coast of Spain, it is known commonly as San Martiño. The Māori language name for

129-413: A dark spot on its side. Its eyes are near the top of its head. It has a flat, round body shape and is a poor swimmer. The John Dory catches prey by stalking it, then extending its jaw forward in a tube-like structure to suck the fish in with some water. The water then flows out through the gills; the pre-maxillary bone, the only tooth-bearing bone in this fish, is used to grind the food. The John Dory has

172-521: A dive light. Water in the open ocean appears clear and blue because it contains much less particulate matter , such as phytoplankton or other suspended particles, and the clearer the water, the deeper the light penetration. Blue light penetrates deeply and is scattered by the water molecules, while all other colours are absorbed; thus the water appears blue. On the other hand, coastal water often appears greenish. Coastal water contains much more suspended silt and algae and microscopic organisms than

215-424: A fast rate. In fact, ninety five percent of photosynthesis in the ocean occurs in the photic zone. Therefore, if we go deeper, beyond the photic zone, such as into the compensation point , there is little to no phytoplankton, because of insufficient sunlight. The zone which extends from the base of the euphotic zone to the aphotic zone is sometimes called the dysphotic zone. Ninety percent of marine life lives in

258-406: A food source. Detritivores and scavengers are rare in the photic zone. Microbial decomposition of dead organisms begins here and continues once the bodies sink to the aphotic zone where they form the most important source of nutrients for deep sea organisms. The depth of the photic zone depends on the transparency of the water. If the water is very clear, the photic zone can become very deep. If it

301-458: A high laterally compressed body – its body is so thin it can hardly be seen from the front. The large eyes at the front of the head provide it with the binocular vision and depth perception it needs to catch prey. This eye spot also confuses prey, which can then be sucked into its mouth. It primarily eats smaller fish, especially schooling fish such as sardines . Occasionally it eats squid and cuttlefish . Its main predators are sharks such as

344-456: A large impact on those who reside in it. The depth is, by definition, where radiation is degraded down to 1% of its surface strength. Accordingly, its thickness depends on the extent of light attenuation in the water column. As incoming light at the surface can vary widely, this says little about the net growth of phytoplankton. Typical euphotic depths vary from only a few centimetres in highly turbid eutrophic lakes, to around 200 meters in

387-502: A specific gravity of just 0.86. In the velvet belly lanternshark ( Etmopterus spinax ), a benthopelagic species, 17% of the bodyweight is liver of which 70% are lipids. Benthic rays and skates have smaller livers with lower concentrations of lipids; they are therefore denser than water and they do not swim continuously, intermittently resting on the seabed. Some fish have no buoyancy aids but use their pectoral fins which are so angled as to give lift as they swim. The disadvantage of this

430-546: A suitable substrate. Cuttlefish are able to adjust their buoyancy using their cuttlebones , lightweight rigid structures with cavities filled with gas, which have a specific gravity of about 0.6. This enables them to swim at varying depths. Another invertebrate that feeds on the seabed and has swimming abilities is the nautilus , which stores gas in its chambers and adjusts its buoyancy by use of osmosis , pumping water in and out. Photic zone The photic zone (or euphotic zone , epipelagic zone , or sunlight zone )

473-461: Is a typical demersal fish , but can also be found in the open water column , and the Atlantic herring ( Clupea harengus ) is predominantly a pelagic species but forms large aggregations near the seabed when it spawns on banks of gravel. Two types of fish inhabit the demersal zone: those that are heavier than water and rest on the seabed, and those that have neutral buoyancy and remain just above

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516-411: Is considered by some persons as the most delicious fish that appears at table". She recommends simply baking it "very gently", avoiding it drying out in the oven. John Dory is a popular choice among professional chefs due to the versatility of the fish, though access to home cooks is limited; the bycatch fish is not typically sold at supermarkets. Demersal Being just above the ocean floor,

559-515: Is left at 100 metres. No light penetrates beyond 1000 metres. In addition to overall attenuation, the oceans absorb the different wavelengths of light at different rates. The wavelengths at the extreme ends of the visible spectrum are attenuated faster than those wavelengths in the middle. Longer wavelengths are absorbed first; red is absorbed in the upper 10 metres, orange by about 40 metres, and yellow disappears before 100 metres. Shorter wavelengths penetrate further, with blue and green light reaching

602-514: Is that, if they stop swimming, the fish sink, and they cannot hover, or swim backwards. Demersal fish have various feeding strategies; many feed on zooplankton or organisms or algae on the seabed; some of these feed on epifauna ( invertebrates on top of the seafloor), while others specialise on infauna (invertebrates that burrow beneath the seafloor). Others are scavengers , eating the dead remains of plants or animals, while still others are predators . Zooplankton are animals that drift with

645-485: Is the aphotic (or midnight) zone, where no light penetrates. This region includes the majority of the ocean volume, which exists in complete darkness. Phytoplankton are unicellular microorganisms which form the base of the ocean food chains . They are dominated by diatoms , which grow silicate shells called frustules . When diatoms die their shells can settle on the seafloor and become microfossils . Over time, these microfossils become buried as opal deposits in

688-430: Is the uppermost layer of a body of water that receives sunlight , allowing phytoplankton to perform photosynthesis . It undergoes a series of physical, chemical, and biological processes that supply nutrients into the upper water column . The photic zone is home to the majority of aquatic life due to the activity ( primary production ) of the phytoplankton. The thicknesses of the photic and euphotic zones vary with

731-431: Is very murky, it can be only fifty feet (fifteen meters) deep. Animals within the photic zone use the cycle of light and dark as an important environmental signal, migration is directly linked to this fact, fishes use the concept of dusk and dawn when its time to migrate, the photic zone resembles this concept providing a sense of time. These animals can be herrings and sardines and other fishes that consistently live within

774-484: The dusky shark , and large bony fish. John Dory are benthopelagic coastal fish , found on the coasts of Africa, South East Asia, New Zealand , Australia , the coasts of Japan , and on the coasts of Europe . They live near the seabed, living in depths from 5 to 360 metres (16 to 1,200 ft). They are normally solitary. John Dory are more commonly found in the waters of the North Island of New Zealand, than

817-595: The marine sediment . Paleoclimatology is the study of past climates. Proxy data is used in order to relate elements collected in modern-day sedimentary samples to climatic and oceanic conditions in the past. Paleoclimate proxies refer to preserved or fossilized physical markers which serve as substitutes for direct meteorological or ocean measurements. An example of proxies is the use of diatom isotope records of δ13C , δ18O , δ30Si (δ13C diatom , δ18O diatom , and δ30Si diatom ). In 2015, Swann and Snelling used these isotope records to document historic changes in

860-463: The substrate . In many species of fish, neutral buoyancy is maintained by a gas-filled swim bladder which can be expanded or contracted as the circumstances require. A disadvantage of this method is that adjustments need to be made constantly as the water pressure varies when the fish swims higher and lower in the water column. An alternative buoyancy aid is the use of lipids, which are less dense than water— squalene , commonly found in shark livers, has

903-478: The amount of light penetration, as discussed in pelagic zone . The upper 200 metres is referred to as the photic or euphotic zone. This represents the region where enough light can penetrate to support photosynthesis, and it corresponds to the epipelagic zone. From 200 to 1000 metres lies the dysphotic zone, or the twilight zone (corresponding with the mesopelagic zone). There is still some light at these depths, but not enough to support photosynthesis. Below 1000 metres

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946-527: The colder waters surrounding the South Island . When John Dories are three or four years of age, they are ready to reproduce. This happens around the end of winter. They are substrate scatterers, which means that they release sperm and eggs into the water to fertilize. Typical lifespan is about 12 years in the wild. Cookery writer Eliza Acton in her 1845 book Modern Cookery for Private Families observed that John Dory "though of uninviting appearance,

989-422: The current, but many have some limited means of locomotion and have some control over the depths at which they drift. They use gas-filled sacs or accumulations of substances with low densities to provide buoyancy, or they may have structures that slow down any passive descent. Where the adult, benthic organism is limited to life in a certain range of depths, their larvae need to optimise their chances of settling on

1032-421: The deepest depths. This is why things appear blue underwater. How colours are perceived by the eye depends on the wavelengths of light that are received by the eye. An object appears red to the eye because it reflects red light and absorbs other colours. So the only colour reaching the eye is red. Blue is the only colour of light available at depth underwater, so it is the only colour that can be reflected back to

1075-439: The demersal zone is variable in depth and can be part of the photic zone where light can penetrate, and photosynthetic organisms grow, or the aphotic zone , which begins between depths of roughly 200 and 1,000 m (700 and 3,300 ft) and extends to the ocean depths, where no light penetrates. The distinction between demersal species of fish and pelagic species is not always clear cut. The Atlantic cod ( Gadus morhua )

1118-535: The establishment of globally cooler conditions and the expansion of glaciers across the Northern Hemisphere from 2.73 Ma. While the halocline appears to have prevailed through the late Pliocene and early Quaternary glacial–interglacial cycles , other studies have shown that the stratification boundary may have broken down in the late Quaternary at glacial terminations and during the early part of interglacials. Phytoplankton are restricted to

1161-400: The eye, and everything has a blue tinge under water. A red object at depth will not appear red to us because there is no red light available to reflect off of the object. Objects in water will only appear as their real colours near the surface where all wavelengths of light are still available, or if the other wavelengths of light are provided artificially, such as by illuminating the object with

1204-405: The familiar “ROYGBIV”; red, orange, yellow, green, blue, indigo, and violet. Water is very effective at absorbing incoming light, so the amount of light penetrating the ocean declines rapidly (is attenuated) with depth. At one metre depth only 45% of the solar energy that falls on the ocean surface remains. At 10 metres depth only 16% of the light is still present, and only 1% of the original light

1247-425: The fish, kuparu , appears to be unique to New Zealand, as there are no cognates found in other Polynesian languages . The John Dory grows to a maximum size of 65 cm (2 ft) and 5 kg (12 lb) in weight. It has 10 long spines on its dorsal fin and 4 spines on its anal fin . It has microscopic, sharp scales that run around the body. The fish is an olive green color with a silver white belly and has

1290-578: The intensity of sunlight as a function of season and latitude and with the degree of water turbidity. The bottommost, or aphotic, zone is the region of perpetual darkness that lies beneath the photic zone and includes most of the ocean waters. In the photic zone, the photosynthesis rate exceeds the respiration rate. This is due to the abundant solar energy which is used as an energy source for photosynthesis by primary producers such as phytoplankton. These phytoplankton grow extremely quickly because of sunlight's heavy influence, enabling it to be produced at

1333-430: The nutricline. Chemical factors include oxygen and trace elements. Biological factors include grazing and migrations. Upwelling carries nutrients from the deep waters into the photic zone, strengthening phytoplankton growth. The remixing and upwelling eventually bring nutrient-rich wastes back into the photic zone. The Ekman transport additionally brings more nutrients to the photic zone. Nutrient pulse frequency affects

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1376-448: The open ocean . It also varies with seasonal changes in turbidity, which can be strongly driven by phytoplankton concentrations, such that the depth of the photic zone often decreases as primary production increases. Moreover, the respiration rate is actually greater than the photosynthesis rate. The reason why phytoplankton production is so important is because it plays a prominent role when interwoven with other food webs . Most of

1419-508: The open ocean. Many of these organisms, such as phytoplankton, absorb light in the blue and red range through their photosynthetic pigments, leaving green as the dominant wavelength of reflected light. Therefore the higher the phytoplankton concentration in water, the greener it appears. Small silt particles may also absorb blue light, further shifting the colour of water away from blue when there are high concentrations of suspended particles. The ocean can be divided into depth layers depending on

1462-417: The photic zone conditions of the north-west Pacific Ocean , including nutrient supply and the efficiency of the soft-tissue biological pump , from the modern day back to marine isotope stage 5e , which coincides with the last interglacial period . Peaks in opal productivity in the marine isotope stage are associated with the breakdown of the regional halocline stratification and increased nutrient supply to

1505-404: The photic zone, which is approximately two hundred meters deep. This includes phytoplankton (plants), including dinoflagellates , diatoms , cyanobacteria , coccolithophores , and cryptomonads . It also includes zooplankton , the consumers in the photic zone. There are carnivorous meat eaters and herbivorous plant eaters. Next, copepods are the small crustaceans distributed everywhere in

1548-414: The photic zone. The initial development of the halocline and stratified water column has been attributed to the onset of major Northern Hemisphere glaciation at 2.73 Ma, which increased the flux of freshwater to the region, via increased monsoonal rainfall and/or glacial meltwater, and sea surface temperatures . The decrease of abyssal water upwelling associated with this may have contributed to

1591-444: The photic zone. Due to biological uptake, the photic zone has relatively low levels of nutrient concentrations. As a result, phytoplankton doesn't receive enough nutrients when there is high water-column stability. The spatial distribution of organisms can be controlled by a number of factors. Physical factors include: temperature, hydrostatic pressure, turbulent mixing such as the upward turbulent flux of inorganic nitrogen across

1634-409: The photic zone. Finally, there are nekton (animals that can propel themselves, like fish, squids, and crabs), which are the largest and the most obvious animals in the photic zone, but their quantity is the smallest among all the groups. Phytoplankton are microscopic plants living suspended in the water column that have little or no means of motility. They are primary producers that use solar energy as

1677-420: The photo zone only. As its growth is completely dependent upon photosynthesis. This results in the 50–100 m water level inside the ocean. Growth can also come from land factors, for example minerals that are dissolved from rocks, mineral nutrients from generations of plants and animals ,that made its way into the photic zone. An increase in the amount of phytoplankton also creates an increase in zooplankton,

1720-407: The phytoplankton competition. Photosynthesis produces more of it. Being the first link in the food chain, what happens to phytoplankton creates a rippling effect for other species. Besides phytoplankton, many other animals also live in this zone and utilize these nutrients. The majority of ocean life occurs in the photic zone, the smallest ocean zone by water volume. The photic zone, although small, has

1763-643: The side of its body also confuses prey, which are scooped up in its large mouth. In New Zealand , Māori know it as kuparu , and on the East Coast of the North Island, they gave some to Captain James Cook on his first voyage to New Zealand in 1769. Several casks of them were pickled. The name dory is attested from 1440, derived from the French dorée 'gilded', a French name for the fish. The addition of "John" appears in 1609, and probably comes from

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1806-457: The solar energy reaching the Earth is in the range of visible light, with wavelengths between about 400-700 nm. Each colour of visible light has a unique wavelength, and together they make up white light. The shortest wavelengths are on the violet and ultraviolet end of the spectrum, while the longest wavelengths are at the red and infrared end. In between, the colours of the visible spectrum comprise

1849-410: The zooplankton feeds on the phytoplankton as they are at the bottom of the food chain. Dimethylsulfide loss within the photic zone is controlled by microbial uptake and photochemical degradation. But what exactly is dimethylsulfide and why is it important? This compound (see the photo) helps regulate sulfur cycle and ecology within the ocean. Marine bacteria, algae, coral and most other organisms within

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