Shark: The King Of Water World

They are one of the few individuals that survived themselves from being extinct. Many think that shark is cruel in nature but the fact is that there are only few out of 350 species of sharks that are considered dangerous: the great white shark, tiger shark, bull shark and oceanic white tip shark.

They can survive in all the weather conditions from cold to temperate waters. They are also found in water bodies with temperatures around 90 degrees Fahrenheit. Almost all sharks are carnivores and eat seals, dolphins, sharks and other fish. They are classified into cold-blooded animals. This means that their bodies change temperature as the water temperature changes. Sharks have a body structure of sleek, streamlined design which supports them to swim without using up a lot of energy. This is very important because they don’t sleep and most of them continue their journey without sleeping.

God always provide every creature an ability to defend itself from enemies and so sharks have skin like the spiky suit of armor. Just as the teeth in their jaws are replaced after certain period of time and same as spiky teeth on their body are also changed. Throughout the life the sharks have supply of teeth. In a year an adult shark goes through 7 to 12 sets of teeth. In order to satisfy their needs different species of sharks have different types of teeth. Sharks do not make use of their teeth to chew. They gulp down things whole or in big pieces. The most common shape of teeth of sharks is plate-like triangular one.

They are provided with six senses which make them very well equipped to have their prey. The six senses which shark use very effectively for searching and hunting their prey are vision, vibration, hearing, smell, taste and electro-perception. A shark with its ampullae’s can sense vibrations in the water and will fly through the water straight to the source. Shark has very sensitive nostrils and can find its prey even of small size with great accuracy. They rest during the day time and go for their hunt at the evening and dark hours. As per survey in a zoological environment they eat about 1 % to 10% of its total body weight per week.

Mating of Sharks

The mating actions change as per their size. In smaller species the male curls around the female. In larger species the male arranges himself parallel and in line with the female. Males of many species during mating bite females on the pectoral fins or the middle of the back to hold onto them. Females often bear wound or marks after mating. A close look at these marks shows that they have been made by upper jaw teeth. In some blue shark female sharks, the skin on the back and flanks is double as compared to those of males. Fertilization of Shark and batoid eggs takes place within their body. For energy-intensive reproduction, internal fertilization is a key adaptation.

After the birth young sharks are fully formed and physically able to survive themselves. The number of sharks found in a group usually does not go beyond 100 since the sharks can survive on their own even when they are very young. Clasper is the name given for modified inner edges of the pelvic fins of male sharks. While mating, the straight claspers are bent forward. The male puts in one clasper at a time into the female. The muscles cause seminal fluid down a groove in the clasper and into the female oviduct.

At a time depending on its species, sharks have from 1 to 100 pups. Some sharks lay eggs while other give birth to live pups. Some sharks do not worry about their pups after they are born, although they will search out safe places, where they can lay eggs or give birth. Many pups swim near to shore to grow up on their own. They require 10 to 15 years to grow fully and have an average life span of 100 years.

More time humans spent in their world, the more trouble is cause to them. Human beings should not interfere in their world doing so causes harm to both. A shark is the creativity of God and we should respect their power.

http://www.buzzle.com/editorials/8-9-2004-57651.asp

by: : http://www.buzzle.com/authors.asp?author=949

A Wonderful Fishy World

Have you ever stopped to take a look at the world that a fish lives in? For us it’s such a dark and mysterious place but that is not all that captures us, it is the fact that the fish not only live but also thrive in such an environment. But how do they do it? How do they manage?

Well let’s see, shall we?

Everybody knows that fish have gills. The gills are what make it possible for the fish to breath under water, every gill is made up of curved arches of cartilage on this cartilage are little gill filaments which , to make a long story short, allow the water to pass next to tiny capillaries which absorb the oxygen. Everybody knows that, at least I hope everybody knows that, it is basic fish knowledge.

Something that maybe fewer people know is the fact that fish have a swim bladder; this is the organ that allows the fish to stay in one place without having to tread water as we do. The swim bladder does this by filling up with oxygen from the blood stream. How does it get the oxygen out of the blood stream? There is a little organ attached to the side, this is what collects the oxygen and inflates the swim bladder. Up until now you might say…boring, but did you know that it is because of the swim bladder that the fish can go to depths of up to seven thousand feet or more?

Every diver knows the fact that when you swim up and down in water that deep you have to pressurize or depressurize yourself (or you would either explode or implode); fish manage to do this with the swim bladder, by pressurizing the fish is able to go to depths that we can't even dream of, our little fishy has to take care though and not try to go about pressurizing and depressurizing too fast or he could seriously injure himself, even to the point of losing his life.

If we take an even closer look at fish and the way that they use their swim bladders, we would find that some fish don't only use it for going into the deep blue sea or to stay in one place, there are fish that use their swim bladder to make certain noises such as the catfish, other fish use their swim bladder to breath out of the water, like the lungfish and of course there are the fish that don't even have swim bladders, they found other ways to stay buoyant...I guess some fish just like to be different.

Talking about different, how many people do you know who can produce their own electricity, with their own body? There are many fish that can do just that, they have special organs that can either produce light or even electricity...this is usually used for predatory reasons but there are some fish that just want to be able to see in the dark.

It is usually the fish that can only be found in the depths of the sea that produce light, and it is a light so strong that it can pierce the thickest night, it can light up places that have not seen light for thousands of years, but like I said, most of those fish have dark intentions on their side because all they are trying to do is to attract a smaller fish so that they can have a good supper. The fish that produce electricity are the electric eel and the electric catfish, they also use their abilities for food. The biggest electric eel can output enough electricity to electrocute a grown man!

Fish are such amazing creatures, you know man thinks that he knows so much about everything, but I think that God is not willing to give up all of His secrets so soon. I believe that there is much more out there to see and to discover. Not just weird fish organs, if we were to stop and take a closer look at the world around us I think that we would be amazed at what we would find.

Yes, fish are amazing creatures!

by: Claudia Miclaus

Sounder and Sonar

SONAR (SOund NAvigation and Ranging) — or sonar — is a technique that uses sound propagation under water (primarily) to navigate, communicate or to detect other vessels. There are two kinds of sonar — active and passive. Sonar may be used as a means of acoustic location.

Acoustic location in air was used before radar. Sonar may also be used in air for robot navigation while SODAR (an upward looking in-air sonar) is used for atmospheric investigations. Acoustic emission measurements can also be made for crack detection.

The term sonar is also used for the equipment used to generate and receive the sound. The frequencies used in sonar systems vary from infrasonic to ultrasonic. The study of underwater sound is sometimes known as hydroacoustics.
Principle of an active sonar - send and return pings.


Sounder and Sonar in the fisheries

The use of sonar and sounding equipment is commonplace in many fisheries vessels. Modern sonar gives the ability to locate schools of fish in the water column and then to position the fishing gear accurately to target the school. The technology is now commercially available to classify the bottom type (e.g. rock, sand, silt) by processing the signal from a depth sounder. This, in conjunction with Global Positioning Systems (GPS), digital charts and personal computers, allows an operator to build a highly detailed three-dimensional model of their fishing grounds over time. When further integrated with information on catches, weather, time and tide, such systems can incorporate much of the information and experience an operator gains over time. Improvements in commercially available sounder and sonar technology will likely continue with the incorporation of more frequencies, higher levels of resolution and a better ability to detect and discriminate fisheries resources for targeting.

For some decades acoustic techniques have been used as a survey tool in estimating the abundance or biomass of fish stocks. Only recently has it been possible to determine, with some confidence, the identity of the fish schools being detected. The CSIRO's multi-frequency towed device (MUFTI) technology is capable of discriminating both fish species and size, and has been used in trial surveys of deep-water species such as orange roughy and blue grenadier. Acoustic biomass-surveys are particularly suited to species were the population aggregates into a small area, such as during spawning. In the case of orange roughy the multi-frequency system has significantly reduced the uncertainty surrounding biomass estimates, and generally improved the assessment of the stocks' condition. Whilst not directly applicable at present, this sort of technology is under continuous development and will eventually flow through to the fishing industry in the future.

The other main acoustic device that will have an increasingly marked affect on fisheries development is the sidescan sonar with its ability to produce detailed maps of the seabed. Sidescan sonar maps the seafloor in a swath either side of the vessel—hence the term 'swath mapping'. Despite the comprehensive look of broad-scale bathymetric charts, most Australian waters are very poorly mapped, with large areas virtually unknown. The directed use of high-resolution swath mapping over the past few years has had spectacular results in the waters around, and to the south of, Tasmania. Examination of swath mapping of the Chatham Rise (east coast of New Zealand) almost doubled the estimated area suitable for orange roughy in the area. Geoscience Australia (GA) is currently undertaking the Seabed Mapping and Characterisation project, which is expected to provide detailed seabed mapping of the entire Exclusive Economic Zone (EEZ). The project will provide data to support Australia's UNCLOS claim to seabed beyond the EEZ and assist in Regional Marine Planning.

LINKS and REFERENCE:
* Fisheries Acoustics Research (FAR) at University of Washington http://www.acoustics.washington.edu/

* "ACOUSTICS IN FISHERIES AND AQUATIC ECOLOGY" http://www.ifremer.fr/sympafae/

* http://www.daff.gov.au/brs/fisheries-marine/info/technology

Deep Sea Fishing Tips

Just as with any other type of fishing, deep sea saltwater fishing techniques are largely dependent on what specifically you are trying to catch. However, the good news is that there are particular tips and techniques that can help you have a better chance of landing your fish of choice while you're out on your deep sea expedition. Though there are a host of targets for deep sea fishermen, a few of the common ones are the albacore, yellowtail, white sea bass, and barracuda. Each one of these requires a specific knowledge and approach to make your deep sea expedition a success.

The albacore tuna can be found in temperate deep seas across the globe. It is distinguished from other tunas by the elongated pectoral fins. The albacore eats primarily small fish, but squid crab and shrimp play an important part as well. When you set out to go deep sea fishing, keep in mind that they are located and caught most often by trolling through an area that offers prime diet and temperature conditions for the fish.


Most often, the environment in the waters off of California and Mexico present an ideal place for the albacore. As a result, most albacore deep sea fishing success comes when they are sought after in those waters. Most deep sea sport fishing boats supply trolling rigs for albacore, but if you prefer to use your own rod, you need to make sure that it is between five and a half to six and a half feet long with a sixty to eighty pound test.

The majority of troll caught albacore are caught on feather jigs with colors depending on the condition. If you decide to use bait when fishing for albacore, the most effective kinds are anchovies or sardines. One of the key things to remember when deep sea fishing is to always be alert and prepared - from the very first cast on. It is often the first baits into the water that are bit. Also, when your boat has stopped, make sure that your line is straight out in front of you - this will prevent tangles.

Another popular target of deep sea fishermen is the yellowtail. Typically found in more tropical waters, there are a number of ways to fish yellowtail. They will take a variety of baits and lures, with squid, sardines, mackerels, and anchovies being the most preferred. One thing to keep in mind when dealing with yellowtail is that they are extremely fast.

You will most likely want to use a kind of jig fishing, which allows you to fish with much heavier line. A thirty to fifty pound test works pretty well. However, when the yellowtail are feeding on or near the surface, they sometimes will take surface iron. Squid is certainly the most effective bait of all when dealing with yellowtail. The specific type of hook and jig that will work best is most accurately determined by certain conditions - such as current, depth, and the typical size of yellowtail in the area.

http://ezinearticles.com/?expert=Daniel_Eggertsen