Tag Archives: fish

Amazon Molly Fish are All Female

A fish species, which is all female, has survived for 70,000 years without reproducing sexually, experts believe.
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The species, found in Texas and Mexico, interacts with males of other species to trigger its reproduction process. The offspring are clones of their mother and do not inherit any of the male’s DNA. Typically, when creatures reproduce asexually, harmful changes creep into their genes over many generations.
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One theory is that the fish may occasionally be taking some of the DNA from the males that trigger reproduction, in order to refresh their gene pool.

Dr Laurence Loewe, of the university’s School of Biological Sciences, said: “What we have shown now is that this fish really has something special going on and that some special tricks exist to help this fish survive. “Maybe there is still occasional sex with strangers that keeps the species alive. Future research may give us some answers.”

He added that their findings could also help them understand more about how other creatures operate. “I think one of the interesting things is that we are learning more about how other species might use these tricks as well,” he said. “It might have a more general importance.”

ASU Science Studio Podcasts

Science Studio offers podcasts by the Arizona State University School of Life Sciences with professors discussing science; it is another excellent source of science podcasts. Podcasts include:

Of Whales, Fish and Men: Managing Marine Reserves – With 90% of the world’s fisheries in a state of collapse, the questions around establishing marine reserves, monitoring, and species/stock recovery take on critical dimensions. But how do decision-makers, stakeholders, and the public formulate effective conservation policies; ones right for their community?
Biology on Fire – Regents’ Professor, Mac Arthur Fellow, author and a world’s expert on fire and fire ecology Stephen Pyne talks about how fire, its use, misuse, and its biological nature have shaped our world, before and because of man, and learn how policies of the past still reverberate in our present, in Arizona and globally.
Giant Insects: Not just in B movies – Professor Jon Harrison sheds light on the evolution of his scientific career and nature’s biggest order: arthropods. How big is big? In the Paleozoic, cockroaches were the size of housecats and dragonflies the size of raptors.
Special Feature: Building a science career – One of the most highly cited ecologists in the world, Jane Lubchenco trod her own unique path to success. In this live recording with the Association for Women in Science, she explains how assertiveness, the art of negotiation, and knowing the currency for promotion and tenure can make the difference between achieving balance between family and career and dropping out the leaky academic pipeline that leads to advancement.

These podcasts are great way to use the internet to serve the mission of universities: to educate. And a great way to promote science.

Mutualism – Inter-species Cooperation

Shrimp with Goby Fish

A Mutual Affair by Olivia Judson

I’d like to introduce you to one of my favorite animals: the shrimp goby. These pretty little fish lead lives of enviable indolence. As their name suggests, they live with shrimp (often, a pair). The shrimp build and maintain a burrow, which the goby and shrimp live in together. Each shrimp works hard, shoveling sand out of the front entrance like a miniature bulldozer. As soon as it’s delivered the rubble to a suitable distance, it shoots back into the burrow.

The front entrance of the burrow is often reinforced with bits of shell and coral — all of which is done by the shrimp. The goby just sits in the entrance of the burrow, keeping guard and warning the shrimp, which is nearly blind, of danger. At any sign of danger — a diver coming too close, a passing predator — the goby darts into the burrow. If the goby zooms in, the shrimp hastily retreats deep inside. And before the shrimp emerges from the burrow, it touches the goby’s tail with its long antennae. To show it’s safe to come out, the goby gently wiggles its tail. When the shrimp is out of the burrow, it keeps one antenna touching the goby. If the goby suddenly retreats, so does the shrimp.
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These animals are dependent on each other. Remove the fish, and the shrimp stops burrowing; the shrimp forage while burrowing, so without a fish, they grow more slowly, too. The shrimp need their guard goby. And the guard goby needs its shrimp: deny the goby shelter in a burrow, and it will promptly be killed by predators (yes, someone did the experiment). The shrimp keep the goby clean, too: they groom it.

photo by Boogies with Fish

Giant Star Fish and More in Antarctica

photo of giant starfish

Photo by John Mitchell, New Zealand’s National Institute of Water and Atmospheric Research. Read a great deal about the New Zealand Census of Antarctic Marine Life project: 26 scientists and 18 crew took a 50-day voyage aboard RV Tangaroa in February-March 2008.

Benthic invertebrates in Antarctica are well known for their large size. This feature, known as “gigantism” is common amongst certain groups including sea spiders, sponges, isopods, starfish, and amphipods. The phenomenon is a subject of intense scientific investigation, but there are many contributing factors.

Slow growth rates, late reproductive maturation, prolonged periods of embryonic development, and low predation rates that are typical of Antarctic waters contribute to long life-spans for many species and can also result in large size animals. Animal physiology is thought to play a role as well, as those groups that require large amounts of calcium should not, in theory, grow well in Antarctic waters. This is because the calcium carbonate (needed for growth of shells, or starfish ‘tests’) has low solubility in very cold seawater. Yet starfish, which have a calcareous exoskeleton or ‘test’ which needs lots of calcium, can reach much larger sizes than found in New Zealand waters, as seen in [photo].

Another crucial part of the story is that the low sea temperatures allow more oxygen to be dissolved in the sea water than in warmer latitudes. Sea spiders for example are not only larger, but reach more than 1000 times the weight of most temperate species. Amphipod crustaceans in the Southern Ocean are also large; more than five times as long as the largest temperate species.

Chinook Salmon Vanish Without a Trace

The Chinook salmon that swim upstream to spawn in the fall, the most robust run in the Sacramento River, have disappeared. The almost complete collapse of the richest and most dependable source of Chinook salmon south of Alaska left gloomy fisheries experts struggling for reliable explanations – and coming up dry.

Whatever the cause, there was widespread agreement among those attending a five-day meeting of the Pacific Fisheries Management Council here last week that the regional $150 million fishery, which usually opens for the four-month season on May 1, is almost certain to remain closed this year from northern Oregon to the Mexican border.
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So what happened? As Dave Bitts, a fisherman based in Eureka in Northern California, sees it, the variables are simple. “To survive, there are two things a salmon needs,” he said. “To eat. And not to be eaten.”

Fragmentary evidence about salmon mortality in the Sacramento River in recent years, as well as more robust but still inconclusive data about ocean conditions in 2005, indicates that the fall Chinook smolts, or baby fish, of 2005 may have lost out on both counts. But biologists, fishermen and fishery managers all emphasize that no one yet knows anything for sure.

Grand Flood

Grand Canyon photo by John Hunter

Model analysis helps protect river’s ecosystem

The goal of the high-flow experiment, the third since 1996, is to see if such high flows can help reconstruct some of the canyon’s beaches and sand bars that are instrumental to ecological systems and native fishes that have suffered since the building of the Glen Canyon Dam in 1963.
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By allowing flow of water that, at its peak, will be more than three times its normal rate (to a volume of 41,500 cubic feet per second), researchers hope to flush some of the dam system of its backed-up sediment and reconstruct habitat downstream. It is expected that the high water-flows will rebuild eroded beaches downstream of the dam by moving sand accumulated in the riverbed onto sandbars.

That in turn will allow the re-establishment of eddy sandbars that provide the slow moving, backwater channels vital for native fish species. The sand bars also provide camping areas for river runners and hikers, and the beaches provide sand to the canyon that helps preserve archaeological resources.

Antarctic Fish “Hibernate” in Winter

This is the first time fish have been seen actively becoming torpid—a state similar to hibernation in land animals—as part of an annual cycle. “A lot of freshwater fish go [unexpectedly] dormant in winter because a drop in temperature lowers their metabolism,” said study co-author Hamish Campbell, a zoologist at the University of Queensland, Australia.

“By contrast, these Antarctic fish actively reduce their ‘cost of living,'” he said… “The fish became 20 times less active in winter compared to summer,”… About every week or so the cod wake up and swim around for a few hours, the team observed. “This is quite similar to ‘denning’ in bears, where the hibernation isn’t so deep and the animals can be disturbed, then spend some time awake before going back to bed,” Fraser said.

Full paper: Hibernation in an Antarctic Fish: On Ice for Winter – Arctic Sharks – Antarctic Robo-sub

Your Inner Fish

photo of Neil Shubin

Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body by Neil Shubin. A great piece from the University of Chicago, Fish out of Water, provides a good preview to the book:

What are the leading causes of death in humans? Four of the top ten causes—heart disease, diabetes, obesity, and stroke – have some sort of genetic basis and, likely, a historical one. Much of the difficulty is almost certainly due to our having a body built for an active animal but the lifestyle of a spud.
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The problem is that the brain stem originally controlled breathing in fish; it has been jerry-rigged to work in mammals… This works well in fish, but it is a lousy arrangement for mammals.
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The example from microbes is not unique. Judging by the Nobel Prizes awarded in medicine and physiology in the past 13 years, I should have called this book Your Inner Fly, Your Inner Worm, or Your Inner Yeast. Pioneering research on flies won the 1995 Nobel Prize in medicine for uncovering a set of genes that builds bodies in humans and other animals. Nobels in medicine in 2002 and 2006 went to people who made significant advances in human genetics and health by studying an insignificant-looking little worm (C. elegans). Similarly, in 2001, elegant analyses of yeast (including baker’s yeast) and sea urchins won the Nobel in medicine for increasing our understanding of some of the basic biology of all cells. These are not esoteric discoveries made on obscure and unimportant creatures. These discoveries on yeast, flies, worms, and, yes, fish tell us about how our own bodies work, the causes of many of the diseases we suffer, and ways we can develop tools to make our lives longer and healthier.

Two of my more controversial posts have been: Evolution is Fundamental to Science and Understanding the Evolution of Human Beings by Country. Evolution is not controversial scientifically. Just as gravity is not. Obviously this understanding is far from universal however.

But it is just a matter of time: similar to Galileo Galilei and heliocentric cosmology. See: Galileo’s Battle for the Heavens – Copernican System – Galileo). We now sit maybe 100 years after Galileo’s death (based on the evidence available in support of each scientific theory). At some point the evidence is accepted and life continues. Though I must admit it, I find it a bit disappointing how long it is taking for some people to accept the evidence of evolution. But I probably need to learn to be more patient – I have been told that more than once. All I can do is try to help present some small amount of the great work so many scientists have done to advance our knowledge. And here I am talking about evolution – for the 28% of those in the USA that couldn’t provide the answer that earth revolves around the sun, in 1998, well, they need much more help than I can provide.

SelFISHing

Until All the Fish Are Gone

Scientists have been warning for years that overfishing is degrading the health of the oceans and destroying the fish species on which much of humanity depends for jobs and food. Even so, it would be hard to frame the problem more dramatically than two recent articles in The Times detailing the disastrous environmental, economic and human consequences of often illegal industrial fishing.

Sharon LaFraniere showed how mechanized fishing fleets from the European Union and nations like China and Russia – usually with the complicity of local governments – have nearly picked clean the oceans off Senegal and other northwest African countries. This has ruined coastal economies and added to the surge of suddenly unemployed migrants who brave the high seas in wooden boats seeking a new life in Europe, where they are often not welcome.

The second article, by Elisabeth Rosenthal, focused on Europe’s insatiable appetite for fish – it is now the world’s largest consumer. Having overfished its own waters of popular species like tuna, swordfish and cod, Europe now imports 60 percent of what it consumes. Of that, up to half is contraband, fish caught and shipped in violation of government quotas and treaties.

I have mentioned the very serious problem of over-fishing the oceans:

The measured effects today should be enough for sensible people to realise the tragedy of the commons applies to fishing and obviously governments need to regulate the fishing to assure that fishing is sustainable. This is a serious problem exacerbated by scientific and economic illiteracy. The obvious scientific and economic solution is regulation. Determining the best regulation is tricky (and political and scientific and economic) but obviously regulation (and enforcement) is the answer.

Sadly this selfish consuming now and passing the problem to those who follow is common lately: Tax Our Children and Grandchildren Instead of Us. Remember when parents actually wanted to leave the world better off for children? What a quaint old idea.

Fishy Future?

Will seafood nets be empty? Grim outlook draws skeptics:

The researchers found that harvests of nearly 30 percent of commercial seafood species already have collapsed. Without major changes in fisheries management, they say, the trend will accelerate.

“It looks grim, and the projections into the future are even grimmer,” said Boris Worm, a marine biologist and a lead author in the peer-reviewed study, which was published today in the journal Science.

But other scientists question that forecast. “It’s just mind-boggling stupid,” said Ray Hilborn, a University of Washington professor of aquatic and fishery sciences.

The evidence seems pretty convincing overfishing has created serious problems and if unchecked those problems threaten to become even more serious. It also seems a stretch to claim those problems will be unchecked (that the checks will be less than they should be I think is a reasonable position). It seems to me the original stories talking about the end of fishing stocks in the next 40 years are alarmist to the point of being counterproductive.
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