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Showing posts with label fish. Show all posts
Showing posts with label fish. Show all posts
Global Warming Threatens Native Marine Species
As meteorologists tell us that natural disasters are becoming regular occurrences due to climate change, so the threat to certain animals species increases. Marine animals are in serious danger. The sea is warming up.
It is accepted that whales beaching themselves is "normal". However, dugong doing the same thing is not. CSIRO which is always at the forefront of Australian research says that south-eastern and north-western sea regions around Australia have become significantly warmer.
As some species move or even die out and new species arrive the ecological dynamic is disrupted. Death from new diseases becomes the norm. New species eat the food that native creatures eat, so marine animals that have been in the same place for thousands of years are doubly threatened.
The future looks bleak. The climate could level off and remain changed but stabilize. On the other hand, change could be ongoing and the variation in marine species could decline. This could affect food supplies for people.
Conservation
Climate Change Could Make Timid Animals More Aggressive
Climate change can cause changes in behavior. As water becomes warmer so some species of fish become aggressive. Some fish are inherently timid while others are bold. In experiments on fish from the Australian Barrier reef, when water was slowly warmed normally timid fish became aggressive. Their rate of activity increased as well. Evolution has created fish that fit into a niche where survival depends on a fish being very careful about its surroundings. If they openly attack larger fish it could mean the smaller ones will be eaten.
It is possible that similar changes will occur with reptiles, amphibians, ectotherms and even mammals. If timid animals become bold then they could be killed off by predators or by humans using harvesting equipment trying to catch other animals for food. Only a very small increase in temperature led to the change.
In the tests, fish were bred in captivity then released into holding tanks where the water was slowly warmed. They had no chance to socialize with wild fish. When the water was cool the fish hid in plastic pipe. As the water heated up the fish ventured further from the protective pipe.
Certain assumptions can be made from this research. As the Arctic ice disappears, Polar bears wandering near small towns in Alaska, Canada and Northern Europe could become more brazen in their search for food from garbage cans and dump sites. They could kill humans more frequently in their anger. Similarly, rats living in these cold climes may not just die of shock when hit. They could turn on people and fight back.
It is possible that similar changes will occur with reptiles, amphibians, ectotherms and even mammals. If timid animals become bold then they could be killed off by predators or by humans using harvesting equipment trying to catch other animals for food. Only a very small increase in temperature led to the change.
In the tests, fish were bred in captivity then released into holding tanks where the water was slowly warmed. They had no chance to socialize with wild fish. When the water was cool the fish hid in plastic pipe. As the water heated up the fish ventured further from the protective pipe.
Certain assumptions can be made from this research. As the Arctic ice disappears, Polar bears wandering near small towns in Alaska, Canada and Northern Europe could become more brazen in their search for food from garbage cans and dump sites. They could kill humans more frequently in their anger. Similarly, rats living in these cold climes may not just die of shock when hit. They could turn on people and fight back.
Conservation
New Ways to Repel Sharks
Like South Africa, Australia is known as a region of frequent shark attacks. A lot of research has been done over the years in an attempt to reduce such attacks. Humans are not normal food for sharks. It is when humans behave in a similar way to injured fish that attacks occur.
Electronic pulses and sounds have been tried with limited success. Colored diving suits have also proven to be ineffective, until now. It has been discovered that blue lines on wetsuits disrupts the vision of sharks because they are color-blind.
White stripes also work as a deterrent but in a different way. Poisonous fish have white on their bodies. It tells potential predators that eating them will have dire consequences.
The cryptic wetsuit that "blinds" sharks is aimed at divers, while the white stripped warning suite is for those close to the beach. Diving equipment and surfing gear is also being colored to match the wetsuits.
Though shark attacks cannot be stopped entirely, the number of people injured is certain to fall. Tests at the Oceans Institute in Western Australia has shown that the new suits work very well. The new products will be sold by a company called Radiator.
Conservation
Fish Oil Prevents Premature Birth
Over recent years there has been a host of controversial claims about fish oil, calcium and glucosamine. The questions are do these supplements do any good and do they all have to be taken? Some doctors say take them and other GPs say claims about them are nonsense.
Some tests have been done. It has still not been proven that taking calcium prevents deterioration of bones in old age. And there is no proof that glucosamine gets into joints thus reducing pain. Tests on fish oil offer some hope of benefit.
During research into omega 3 (which is in fish oil) on young children a potential benefit came to light. It seems that premature birth is delayed when fish oil is taken. Omega 3 prolongs pregnancy. Subjects who took the supplement also had larger babies. Their birth date was later than predicted. Of course, this brings up another question: Are heavier babies healthier? As the cause of premature birth is unknown perhaps this benefit overrides the perceived consequences of larger babies.
Health
Australian Blog★
Fish Are Intelligent and Can Remember
For years scientists told us what we wanted to believe - that fish have short memories only lasting one lap of the fish bowl. Now the truth has got out. They are intelligent creatures who can learn to do things and can even deceive other animals. Once attacked, if they escape, they remember which predator tried to kill them. Unlike humans, however, there is a cost when they use their intelligence. If they are given one fish for food they are very efficient in catching it, but if given two types of prey they apparently become confused and their effectiveness declines.
Fish interact in a social way. They recognize familiar others and modify their behavior accordingly. Siamese fighting fish will take advantage of a weak fighter by observing fish fights and readily attacking the weaker fish. Fish that clean others act busy when potential "customers' are watching. In a way they advertise.
The myth about fish having no memory or even intelligence is most likely promulgated to justify fishing, when fishermen say it is alright to jab in a hook or gut a fish because they "don't feel any pain".
An example of fish learning occurred when Professor Charles Erikson fed fish after calling to them by saying "fish-fish". When he returned five years later he called to them and some fish came to the surface expecting food. Examples of smart thinkers are trigger fish which use tools to trick prey that hunt them, and frillfin which jump back into rock pools to avoid birds.
Fish interact in a social way. They recognize familiar others and modify their behavior accordingly. Siamese fighting fish will take advantage of a weak fighter by observing fish fights and readily attacking the weaker fish. Fish that clean others act busy when potential "customers' are watching. In a way they advertise.
The myth about fish having no memory or even intelligence is most likely promulgated to justify fishing, when fishermen say it is alright to jab in a hook or gut a fish because they "don't feel any pain".
An example of fish learning occurred when Professor Charles Erikson fed fish after calling to them by saying "fish-fish". When he returned five years later he called to them and some fish came to the surface expecting food. Examples of smart thinkers are trigger fish which use tools to trick prey that hunt them, and frillfin which jump back into rock pools to avoid birds.
Environment
New Research on Box Jellyfish
There has been a breakthrough in the research on box jellyfish. They have thousands of stinging cells on their ten-foot long tentacles. New discoveries have been made into their evolution. This will help in finding antivenom and new treatment for stings to humans.
Some species of jelly fish have good sight: they have 24 eyes, can sense light and form images of their surroundings. Little is known, however, about what they actually see. They don't need to see to mate. Females and males just get together and fertilize eggs in a mass spawning, though some species do appear to mate one-on-one.
The most dangerous jelly fish, in Australia, is the Box Jellyfish (sea wasp or stinger). Some can immobilize while others can kill. The Portuguese man of war is held to be very dangerous, but despite its name it cannot kill humans. Chironex flecken, an Australian box jellyfish, can be lethal. A similar type, Chironex yamaguchii, has killed people in Japan.
Evolution of jellyfish has been pinned down by DNA extracted from tissue samples. It is now known how species are related. It was found that several types cause Irukandji Syndrome which leaves sufferers with body pain, severe depression and feelings of impending doom. If you are stung by members of this group then these symptoms can be expected. Some types have been isolated from others for a long period of time. Sea level changes from tectonic plate movements apparently create new species.
Some species of jelly fish have good sight: they have 24 eyes, can sense light and form images of their surroundings. Little is known, however, about what they actually see. They don't need to see to mate. Females and males just get together and fertilize eggs in a mass spawning, though some species do appear to mate one-on-one.
The most dangerous jelly fish, in Australia, is the Box Jellyfish (sea wasp or stinger). Some can immobilize while others can kill. The Portuguese man of war is held to be very dangerous, but despite its name it cannot kill humans. Chironex flecken, an Australian box jellyfish, can be lethal. A similar type, Chironex yamaguchii, has killed people in Japan.
Evolution of jellyfish has been pinned down by DNA extracted from tissue samples. It is now known how species are related. It was found that several types cause Irukandji Syndrome which leaves sufferers with body pain, severe depression and feelings of impending doom. If you are stung by members of this group then these symptoms can be expected. Some types have been isolated from others for a long period of time. Sea level changes from tectonic plate movements apparently create new species.
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Science
Less Atractive Males Make do With Plainer Females
An audience affects the behavior of mating male fish. If a male Atlantic Molly (Poecilia mexicana) is left alone he will try to mate with the healthiest looking female - the best female in his eyes. If there are other males in the vicinity he will not choose this female.
It may be thought that he is giving up. This is not the case. He is thinking strategically. By choosing a less desirable female he leads other males away from the intended target best female. The male hopes to mate with this female later when the other rival males have gone.
Some males are just too ordinary and have to mate with lesser females because other fitter males stop them getting close to "ideal" females. Mating with any female is better than not mating at all.
This behavior could be present in humans. When a group of young men meet with a group of young females the handsomest men can be expected to pair off with the prettiest young ladies. The less attractive have to make do with second best. This means that some of the good genes carried by the plainer individuals can be passed on despite mating between the healthier, fitter thus better looking people being the norm.
It may be thought that he is giving up. This is not the case. He is thinking strategically. By choosing a less desirable female he leads other males away from the intended target best female. The male hopes to mate with this female later when the other rival males have gone.
Some males are just too ordinary and have to mate with lesser females because other fitter males stop them getting close to "ideal" females. Mating with any female is better than not mating at all.
This behavior could be present in humans. When a group of young men meet with a group of young females the handsomest men can be expected to pair off with the prettiest young ladies. The less attractive have to make do with second best. This means that some of the good genes carried by the plainer individuals can be passed on despite mating between the healthier, fitter thus better looking people being the norm.
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Society
Global Warming Changes Fish Behavior
Animals will not only die if they remain in regions affected by global warning, they will not know what they are doing. Research shows that rising carbon dioxide changes the behavior of fish.
Carbon dioxide makes the acidity of ocean water rise. Like humans, fish rely on nerve cells to "perceive" the environment they live in, like detecting hot and cost, pain or painless. They also have to rely on environmental cues to behave in a particular way. Fish smell predators so they normally move away from them, but high acidity in the water makes the smell attractive. Small fish move too close to predators, so they are easily caught and eaten.
Fish behave this way due to their nerve cells trying to maintain a balance with the environment. With a rise in carbon dioxide and acidity, bicarbonate and chloride levels rise inside nerve cells, so a feeling of security is not turned off by the smell of predators. A switching chemical, GABA, becomes irregular opening nerves which suddenly release all of the bicarbonate and chloride. This causes dramatic changes in fish behavior.
Carbon dioxide makes the acidity of ocean water rise. Like humans, fish rely on nerve cells to "perceive" the environment they live in, like detecting hot and cost, pain or painless. They also have to rely on environmental cues to behave in a particular way. Fish smell predators so they normally move away from them, but high acidity in the water makes the smell attractive. Small fish move too close to predators, so they are easily caught and eaten.
Fish behave this way due to their nerve cells trying to maintain a balance with the environment. With a rise in carbon dioxide and acidity, bicarbonate and chloride levels rise inside nerve cells, so a feeling of security is not turned off by the smell of predators. A switching chemical, GABA, becomes irregular opening nerves which suddenly release all of the bicarbonate and chloride. This causes dramatic changes in fish behavior.
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Biology
Fish Hooks Made of Shell Found in Timorese Cave
The Timor region is a fascinating place to study early humans. At the eastern end of East Timor fish hooks made from shells have been found. They were among bones of more than 2,800 fish.
Jerimalai cave was a home for humans up to 42,000 years ago. The fish hooks were used between 23,000 and 16,000 years before the present. Deep sea pelagic fish were the target food. Tuna bones were abundant.
Professor Sue O'Connor based at the College of Asia and the Pacific at the Australian National University led the research. The varieties of fish identified showed that ancient humans were skilled fishermen. Fishing for tuna is complex even today.
Jerimalai cave was a home for humans up to 42,000 years ago. The fish hooks were used between 23,000 and 16,000 years before the present. Deep sea pelagic fish were the target food. Tuna bones were abundant.
Professor Sue O'Connor based at the College of Asia and the Pacific at the Australian National University led the research. The varieties of fish identified showed that ancient humans were skilled fishermen. Fishing for tuna is complex even today.
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Anthropology
Man Caught Deep Ocean Fish 42,000 Years Ago
Our ancestors not only fished rivers and the coastline. They caught marine food in the deep ocean. It is known that people travelled across oceans 50,000 years ago. However, proof that they could catch fish in the deep sea went back only 12,000 years.
New evidence shows that Man ate fish from the ocean further back than 12,000 years. In caves on the island of East Timor remains of tuna and other large fish have been found.
East Timor was "out of bounds" for paleontologists until recently because of the ongoing troubles with Indonesia. Information on ancient Man is changing scientific knowledge about our ancestors. Bone fish hooks dating back 42,000 years have been found there.
The diet of early Timorese was varied. It included birds, rodents, bats, snakes turtles and fish. Few large animals lived there. Half of the fish found were tuna, a fast moving fish that would have taken great skill to catch. Using nets was the only way, so they had an advanced culture.
New evidence shows that Man ate fish from the ocean further back than 12,000 years. In caves on the island of East Timor remains of tuna and other large fish have been found.
East Timor was "out of bounds" for paleontologists until recently because of the ongoing troubles with Indonesia. Information on ancient Man is changing scientific knowledge about our ancestors. Bone fish hooks dating back 42,000 years have been found there.
The diet of early Timorese was varied. It included birds, rodents, bats, snakes turtles and fish. Few large animals lived there. Half of the fish found were tuna, a fast moving fish that would have taken great skill to catch. Using nets was the only way, so they had an advanced culture.
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Paleontology
Study on Bony Fish, Sharks and Lungfish Clarifies Evolutionary Development
A study on lungfish, bony fish and cartilaginous fish has a great deal to offer in understanding development of legs for life on land. Lungfish are ancient ancestors of tetrapods - four legged animals. Walking on their fins and breathing air, lungfish bravely moved onto the land.
Research has relied on bones preserved as fossils, but muscles cannot be "saved" in this way. A fetus shows ancient stages in a creatures development. This is why a human fetus seems to be reptile-like in its early stages. Examining muscle development of modern lungfish is very informative. Tests were also done on cartilaginous fish such as sharks and ordinary fish.
Embryos of cartilaginous and bony fish were genetically altered to promote growth of precursor pelvic fins that in lungfish became legs. Engineered cells were made to emit red and green light. The study on muscles highlighted the fact that bony fish evolved legs while cartilaginous fish did not. Pelvic muscles of bony fish are a transitory stage between cartilaginous fish and land animals.
Research has relied on bones preserved as fossils, but muscles cannot be "saved" in this way. A fetus shows ancient stages in a creatures development. This is why a human fetus seems to be reptile-like in its early stages. Examining muscle development of modern lungfish is very informative. Tests were also done on cartilaginous fish such as sharks and ordinary fish.
Embryos of cartilaginous and bony fish were genetically altered to promote growth of precursor pelvic fins that in lungfish became legs. Engineered cells were made to emit red and green light. The study on muscles highlighted the fact that bony fish evolved legs while cartilaginous fish did not. Pelvic muscles of bony fish are a transitory stage between cartilaginous fish and land animals.
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Biology
Eight Stages Toward Coral Reef Collapse
Coral reefs may look okay but on closer examination they may be dying. Overfishing, particularly in the Indian Ocean, causes eight steps that lead to reef collapse. Each step is a stage toward the end of a reef.
Keeping fish numbers up is important. When the level falls below 1000 kilograms of fish per hectare seaweed growth increases as well as urchin activity. This is a major indication of a problem. If fish density falls below 300 kilograms a crisis is reached.
Until now, coral cover has been used as a measure of coral health. This research shows that coral cover is the last threshold: the reef is heading toward ecosystem collapse.
It is during the first three stages that constructive change will save a reef. Fishing should be regulated. If a reef is in the final five stages, it is near impossible to save it. Only marine reserves have really healthy coral reefs because fishing is restricted. Unmonitored reefs fare the worst. A management system for each reef needs to be developed and put in place.
Keeping fish numbers up is important. When the level falls below 1000 kilograms of fish per hectare seaweed growth increases as well as urchin activity. This is a major indication of a problem. If fish density falls below 300 kilograms a crisis is reached.
Until now, coral cover has been used as a measure of coral health. This research shows that coral cover is the last threshold: the reef is heading toward ecosystem collapse.
It is during the first three stages that constructive change will save a reef. Fishing should be regulated. If a reef is in the final five stages, it is near impossible to save it. Only marine reserves have really healthy coral reefs because fishing is restricted. Unmonitored reefs fare the worst. A management system for each reef needs to be developed and put in place.
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Science
Filefish Blends in Perfectly With Coral
It's well known that fish living near coral are colored the same as Othe background for protection from predators. The Harlequin filefish (orange spotted filefish), Oxymonacanthus longirostris, goes to extremes to blend into the coral it lives in.
The fish has a hook on the back of its head that it uses to hook onto coral so it can sleep in peace. The shape with the polka-dot blue and yellow spots on its body perfectly match the coral it lives in. Its fin is the same color as the coral's growing tip. It blends in so well predators just swim past them.
When fish use shape and color to match background coral the system is called masquerading. Using color alone is called crypsis. Insects look like plants that they live in, but coral fish have perfected camouflage.
The fish has a hook on the back of its head that it uses to hook onto coral so it can sleep in peace. The shape with the polka-dot blue and yellow spots on its body perfectly match the coral it lives in. Its fin is the same color as the coral's growing tip. It blends in so well predators just swim past them.
When fish use shape and color to match background coral the system is called masquerading. Using color alone is called crypsis. Insects look like plants that they live in, but coral fish have perfected camouflage.
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Science
Australian Moths and Butterflies Are Barcoded
Australian moths and butterflies are being barcoded. There are 10,000 species in Australia and 65 per cent of them have been coded, 28,000 specimens in all. They are not flying around with a tag on them. DNA is analyzed then recorded with an image of a specimen in a barcode system.
The database is a combined project by the Atlas of Living Australia (ALA) and CSIRO's Australian National Insect Collection (ANIC). It is the first time such a system has been used to categorize a group of insects in a country. This is the beginning. Plans are in train to record most organisms worldwide.
The technology has been used to determine if wrongly named fish are being sold. It will be used to identify dangerous pests coming into Australia. Species will now be more effectively categorised in research.
The database is a combined project by the Atlas of Living Australia (ALA) and CSIRO's Australian National Insect Collection (ANIC). It is the first time such a system has been used to categorize a group of insects in a country. This is the beginning. Plans are in train to record most organisms worldwide.
The technology has been used to determine if wrongly named fish are being sold. It will be used to identify dangerous pests coming into Australia. Species will now be more effectively categorised in research.
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Science
New Jellyfish in Coffs Harbour
It seems humans know just about everything. This is a myth really. A new species of jellyfish has be seen in Coffs Harbour, NSW. It seems the marine creature has been there for a long time.
The mystery "object" is a box jellyfish that appears to be totally harmless. It is unlike the Irujandji and is smaller than the dangerous Chironex flecker box jellyfish. Fishermen have been seeing the new jellyfish for sometime but authorities took no notice. A game crew took photos of the animal last week.
The mystery "object" is a box jellyfish that appears to be totally harmless. It is unlike the Irujandji and is smaller than the dangerous Chironex flecker box jellyfish. Fishermen have been seeing the new jellyfish for sometime but authorities took no notice. A game crew took photos of the animal last week.
Finally "professionals" acted and arrangements are being made to catch some specimens. Fish of all kinds are moving south as the temperature of the ocean increases due to climate change. It is believed the visiting jellyfish come from more northern climes. Usually jellyfish do not move south because they can be harmed by rougher seas. They prefer the warm, calmer tropics.
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~~~~~Science~~~~~
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