Fishes Fishes are mainly ectothermic or “cold-blooded” due to

Fishesare mainly vertebrates that live and thrive in marine environments.

Theytypically have an inner skeleton which includes a skull, ribs, and a backboneexcept for sharks and rays, which have cartilage. Fishes are mainly ectothermicor “cold-blooded” due to relying on environmental heat sources. Some exceptionsare tuna, swordfish, and sharks that are “warm- blooded” because they have theability to heat their bodies higher than the water’s temperature. Scalesusually surround the skin of most fish and act as reflectors and give the fishcolors. Scales come in a variety of size, shape and color as well as toughnessof the plates.  Fish breathe using gills,feathery organs full of blood vessels, which help them extract dissolved oxygenfrom the water. They accomplish this by taking in water through the mouth andforcing it out of the gills.

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As the water passes the thin walls of the gills,the dissolved oxygen moves into the bloodstream and travels throughout thefish’s body. The exceptions are lungfish and coelacanth which have paired lungsand breathe similarly to tetrapods.  Mostfish move by contracting a pair of muscles found on either side of the backbone,which travels down the body. The fins, found on either side of the body andtail, increase the surface area as well as speed. Fish usually have astreamlined body which decreases friction from the water.

Bony fish also haveswim bladders that help them to adjust buoyancy. Fish typically possess highlydeveloped sense organs; they rely less on their vision and more on theirhearing, taste, and smell because water transmits sounds, disperses chemicals,and conducts electricity better than air. They can easily detect motion in thewater using a row of scales with sensors commonly known as the lateral line.They use this lateral line system, which detects currents and vibrations, tofind nearby fish and their food source like prey, as well as navigating throughthe waters by detecting electrical charges.1   About 70% of theEarth’s surface is covered in water so fish are found nearly anywhere as longas they have an ideal environment with sufficient living conditions. Fish cantolerate different environmental conditions according to their preferredbiological settings but are sensitive to the water having different amounts ofsalt, oxygen, types and amount of food, water temperature, hiding areas andbreeding areas.2 There are two types of fishes: saltwater fishes andfreshwater fishes.

Freshwater fishes and saltwater fishes control water flowwithin their bodies differently to adapt to their environment by usingosmoregulation. Freshwater fishes have body tissues that have a greater saltcontent than the water. Their gills help diffuse water and make sure theirbodily fluids remain inside the fish while their kidneys process large amountsof water. Saltwater fish, on the other hand, lose large amounts of internalbody fluids because the saline water draws water from the body tissues andleaves through the skin and gills.

Because of osmosis the salt water is lessdilute than the internal fluids and rushes in to replace the internal fluids toform an equilibrium.3 Fish eat a variety of food from plants andalgae to other fish or animals. Freshwater fish arefound in shallow wetlands, lakes and rivers, where the salinity of water isless than 0.

05 percent.4 Saltwater fish are found from the coldAntarctic and Arctic ocean to warmer tropical seas. Since prehistoric times,fish have adapted to living in the water and are found throughout the world’soceans from tropical seas with exotic coral reefs to icy polar waterssurrounded by glaciers and ice. Saltwater fish prefer habitats that includecoral reefs. Salt ponds, mangroves, seagrassbeds and the deep sea.

4The saltwater ocean is the main environment that all fish survived in untilgeologic events such as earthquakes and volcanic activity created conditions toisolate groups of fish. Evolutionary adaptations such as time and naturalselection helped create new freshwater fish species. Fish live close to theoceans surface as well as the darkest depths of the sea. There are many fishthat live in freshwater habitats such as rivers, lakes, and swamps.  Freshwater fish can be characterized as eithera cold water fish or a tropical fish. Examples of tropical freshwater fishesare: angelfish, cichlids, discus.5 Cold water fish are mostlygoldfish.

Examples of cold water saltwater fishes are clown fish, eels,seahorses, butterfly fish and lionfish. Examples of popular saltwater fish are:bluefish, cod, flounder, striped bass, sea trout, tarpon, tuna, halibut,rockfish, sea perch, lingcod, and yellowtail.5 Most ponds, reservoirsand rivers across North America are freshwater. Common freshwater fish include bluegills,carp, catfish, crappie, bass, perch, northern pike, trout, and walleye.5An estuary is where fresh water streams and rivers meet the saltwater from theocean.

The changes in the salinity will determine which fish can live in thearea. Fish like redfish, sea trout, snook and striped bass. Fish need oxygen aswell to survive which plants in the water help create by the process ofphotosynthesis. Water temperature also affects the amount of oxygen the watercan hold seeing as how cold water can hold more oxygen molecules than warmwater as well as different locations. Pollution reduces oxygen in the water bychemicals trapping the particles and heat reducing the amount of oxygen in thewater. Saltwater fish are found all around North America in waters such as the:Atlantic Ocean, Pacific Ocean, Arctic Ocean, Caribbean Sea, Gulf of Mexico,Gulf of Alaska, Beaufort Sea, Hudson Bay, Labrador Sea etc. Freshwater fish inNorth America are found mainly wherever fresh water lies in Canada, the UnitedStates and Mexico. Examples would be: Lake Superior, Lake Winnipeg, Lake Erie,Lake Ontario, Reindeer Lake, Lake Athabasca etc.

   Thereare about 33,000 living fish species according to FishBase, which is greaterthan the total of amphibians, reptiles, birds and mammals combined. Around 510million years back, during the Cambrian era, chordates were the first earliestorganisms that could be considered fish. They had notochords therefore lackinga true spine, and that allowed them to be more agile that invertebrates. ThePaleozoic era is where fish began to diversify and many of which developedexternal armor which aided in defending them from predators.

The Silurian erais when fish began to develop jaws and that made predators more formidable.6One of the oldestclasses of fishes are Cyclostomata which include lampreys and hagfish, a groupof jawless fish known for their toothed vacuum-like sucking mouth and little teeth.The class, Chondrichthyes, holds what are known as cartilaginous fish which arebest known as chimeras, sharks, skates and rays.8 They definingstructures are their skeletons which are made out of calcified cartilage andnot bone.

All cartilaginous fishes are carnivorous and most species feed onlive prey making this group famous for its largest extent of marine lifepredators. There are some species that feed on the remains of dead animals andstill others that are filter feeders. The most diverse of the major groups offishes are ray-finned fishes (Actinopterygii), which contain more than 25,000species such as bowfin, eels, salmon, trout, catfish, piranhas, lanternfish,cods, anglerfish, tarpon, basses, parrotfish, and many others. 8 Ray-finnedfishes share a set of basic characteristics, including a skeleton made up oftrue bone, an upper jaw that consists of two bones and fins that are supportedby a set of bony spines and rays covered with a thin layer of skin. Ray-finnedfishes have diverse and highly adaptable skulls which allow differentmechanisms to occur such as enhancing bite force and jaw protrusion. Thisresults in a wide range of feeding adaptations and ecological roles for theactinopterygian fishes.

8 Lobe-finned fishes (Sarcopterygii) are a groupof bony fishes with limb-like fins that are fleshy at the base and bonesconnected in series that appear and function as limb bones. The livingsarcopterygians include lungfishes (which have both lungs and limb-like fins)and coealacanths, both are living representatives of diverse fossil groups.8Lobe-finned fishes hold special interest to evolutionary biologists because membersthis group gave rise to the first four-legged land vertebrates (tetrapods). Accordingto scientists, there are approximately 3.5 trillion fish currently living inthe ocean and about 32,000 fish species identified living alongside other seacreatures.

1 The population of fish are constantly fluctuating due tofishing, predation, reproduction and environmental factors. Humans haveimpacted wildlife fishes around North America by overfishing, causing pollutionleading to habitat destruction since industrial times. In the past, humans havetake to hunting fish in the water as a means of survival. Fish are heavilyrelied upon as a source of food which humans have caught both as a recreationand as a means of survival, commonly known as fishing. Fisheries are globalcorporations that dedicate their business to catching and selling fish,offering millions of people income.

Fishing from the earliest centuries turnedfrom a recreational activity and a source of food into a huge worldwidebusiness, exporting and importing exotic and delicious fish for means ofconsumers. The industries have created jobs that help fishers and other peoplemaintain a source of income. In the future, it would be hard to tell if we haveany fishes left if we are quickly depleting the ocean’s source. Fishing dates back to at least theUpper Paleolithic period approximately 40,000 years ago. There is evidence thata 40,000 year old Tianyuan man from eastern Asia, included freshwater fish inhis diet using isotopic analysis. There have also been fossils of fish bonesand cave paintings found indicating sea food was important for survival inprehistoric times. The hunter-gatherer lifestyle contained hunting fish as an importantpart of early settlements lives.

Weapons changed over the course of time toofrom using bare hands to nets to harpoons and now to fishing rods.  As the Neolithic culture and technologyflourished, fishing methods became easier and made fishing in dangerous watersmore accessible. Native Americans, from 7500 to 3000 years ago, were known tofish using gorge hook and line off the Californian coast.

The Salt Water GameFish of North America figure shows the fish species that were mostly caught touse as a resource of food.9Overfishingis a major threat to edible threat like tuna and cod. Overfishing causes thepopulation of fish to collapse and forcing the survivors to not being able toreplace those fish that were removed. This is known as commercial extinctionwhich means the species can no longer sustain a fishery.

An example of afishery collapse would involve the Paciffic sardine (Sadinops sagax caerulues) typically found off the coast ofCalifornia. In the beginning of 1937 to then end of 1968, the catch declinedfrom 790,000 long tons to 24,000 long tons and after that the fishery was nolonger economically viable to stay afloat.4 Fishes are an importantfood resource not only in North America but worldwide and fishing pressure hascaused fish stocks to crash or be at risk. Besides reducing fish stocks,unsustainable fishing practices can have other negative impacts on the marineenvironment.

For example, methods of fishing like dredging and trawling cancause widespread damage to marine habitats and organismsliving on the sea floor. These techniques also tend to capture non-target species, or bycatch, whichare then discarded. 98 Scientistsand conservationists push for protection and warn that many stocks of fishcould be wiped out in fifty years as government and corporations push forcatching more fish.   Technological improvementsimproved the style of fishing by gaining an exact measure of navigation andtelecommunication.

Habitatdestruction is another way humans have negatively impacted the fish. Humanshave polluted the water, built dams, removed water for our own uses, farm fishand introduced exotic species. Marine pollution involves industries dumpingsewage, run-off and chemicals and endangers the lives of fish. They accumulatethe toxic chemicals and produce serious illnesses to humans since we consumethem and are on top of the food chain, a prime example being mercury poisoning.An example of an endangered fish due to habitat destruction is the NorthAmerican freshwater fish, the pallid sturgeon, which lost its home due torivers being damaged. Eutrophication also harms fishes and is caused by humansreleasing excess nutrients from fertilizers into streams and rivers. The excessnutrients promote phytoplankton growth and gives rise to algal blooms whichprevent sunlight from reaching the fish in the water and deprive the water ofits oxygen when decomposition occurs. Acidification of the ocean is also ahuman impact because of the excess carbon dioxide we have created, the waterabsorbs it and results in seawater becoming too acidic for fishes to live in.

10Introduction of nonnative species causes a problem for native fish in the areaand leads to a competition for resources. Some fish that have caused problem bybeing introduced as exotic species include tilapia, carp, brown trout, rainbow trout,and sea lampreys. Commercialfisherman and sport fishermen exploit coastal marine fish throughout the worldand fish farming is becoming more common. Aquaculture, more knownas fish farming, has been practiced since 3,500 BCE in China and is basicallyraising fish commercially in an enclosed body of water. This is different froma fish hatchery where fish would live and breed as a means of a conservationeffort to save an endangered species. Common important fish that are producedin fish farming are tilapia, carp, salmon, and catfish. This is an alternativeto wildlife fishing because the demand for fish is increasing and overfishingis a barrier. As of 2016, more than 50% of seafood is produced by fish farmingwith China providing 62% of the world’s most farmed fish.

4   The2006 IUCN Red List has named 1,173 fish species that are threatened withextinction including Atlantic cod, coelancanths, and great white sharks. Freshwaterfish are more threatened because there is a small amount of freshwateravailable to them. Different organizations such as the National Oceanic andAtmospheric Administration and the U.S Wildlife and Fisheries are working tohelp save fish in North America and worldwide by getting behind laws such asthe Clean Water Act and the Endangered Species Act and are influencing peopleto help save the marine environment. People need fishes as a resource for foodand survival and to observe for scientific research. In the future, thepopulation growth of humans is expected to increase even more and yet by theyear 2050, it will be impossible to tell if humans will have the luxury ofeating fish if we are depleting the supply already. These organizations shouldbe better supported and humans need to become aware of the situation at handand limit polluting the marine environment as well as overusing the resourcefor commercial gain.

Asa recreational activity, fish have been known to be kept as decorative pets andare often displayed in diverse sizes shapes and colors in aquariums for ourviewing pleasure. Fishing is also a relaxing activity using fishing rods andbait where people often throw the fish back into the water. Fish have come tosignify a great deal in religion, such as Christianity by representing Jesus orBuddhism where the fish symbolizes happiness and “going with the flow”. Humansenjoy the mass amount of biodiversity that fishes have and often visitaquariums to see the different shapes and colors of fish. People enjoy fishingas a hobby and throw the fish back into the water when they’re done.

We alsotend to keep fishes as pets. In historical times, fish were symbolic of Christianityand represented happiness in other religions as well. Humans have made storiesinvolving fish from books to movies using animation and narratives, such asFinding Nemo and Jaws.