all ichthyology stories

Teen diets can hurt their lungs

50443248 — Tue, 02 Oct 2007 09:27:34 -0400

For most teenagers in the United States and Canada, fish and fruit are not high on their delicious list. Also, many of them — about 20 percent of those under 18 — cough, wheeze, and suffer from asthma and bronchitis. Researchers at the Harvard School of Public Health (HSPH) have found a connection between these two situations.

A study of more than 2,100 high school seniors found that those who eat the least fruit and fish have the weakest lungs.

When fish first started biting

Tue, 10 Jul 2007 14:20:30 -0400

Before fish began to invade land, about 365 million years ago, they had some big problems to solve. They needed to come up with new ways to move, breathe, and eat.

Take the latter, for example. Fish usually pucker up and suck prey into their mouths. But air is 900 times less dense than water, so land-livers must bite into their food to get a meal. Researchers at Harvard University have just completed a study that gives a clear picture of how that change was made.

Study shows benefits of eating fish greatly outweigh risks

70652986 — Mon, 26 Mar 2007 05:46:48 -0400

Many studies have shown the nutritional benefits of eating fish (finfish or shellfish). Fish is high in protein and omega-3 fatty acids. But concerns have been raised in recent years about chemicals found in fish from environmental pollution, including mercury, PCBs and dioxins. That has led to confusion among the public - do the risks of eating fish outweigh the benefits?

Researchers from the Harvard School of Public Health (HSPH) tackled that question by undertaking the single most comprehensive analysis to date of fish and health. In the first review to combine the evidence for major health effects of omega-3 fatty acids, major health risks of mercury, and major health risks of PCBs and dioxins in both adults and infants/ young children, the results show that the benefits of eating a modest amount of fish per week - about 3 ounces of farmed salmon or 6 ounces of mackerel - reduced the risk of death from coronary heart disease (CHD) by 36 percent.

Notably, by combining results of randomized clinical trials, the investigators also demonstrated that intake of fish or fish oil reduces total mortality - deaths from any causes - by 17 percent.

Included with the paper, which appears in the Oct. 18, 2006, issue of The Journal of the American Medical Association (http:// jama.ama-assn.org/), is the first comprehensive summary of levels of omega-3 fatty acids, mercury, PCBs and dioxins in various species of fish and other foods, including chicken, beef, pork, butter and eggs.

The research was supported by the National Institutes of Health.

Newly found species fills evolutionary gap between fish and land animals

70652986 — Mon, 26 Mar 2007 06:26:14 -0400

Paleontologists have discovered fossils of a species that provides the missing evolutionary link between fish and the first animals that walked out of water onto land about 375 million years ago. The newly found species, Tiktaalik roseae, has a skull, a neck, ribs, and parts of the limbs that are similar to four- legged animals known as tetrapods, as well as fishlike features such as a primitive jaw, fins, and scales.

"This previously unknown, extinct animal represents the beginning of the emergence of fish onto land, and the evolutionary transformation of fins into limbs," says Farish A. Jenkins Jr., Alexander Agassiz Professor of Zoology at Harvard and curator of mammalogy and vertebrate paleontology at Harvard's Museum of Comparative Zoology.

These fossils, found on Ellesmere Island in Arctic Canada, are the most compelling examples yet of an animal that was at the cusp of the fish-tetrapod transition. The new find is described by scientists at Harvard University, the University of Chicago, and the Academy of Natural Sciences in Philadelphia in two related research articles highlighted on the cover of the April 6, 2006 issue of Nature.

"Tiktaalik blurs the boundary between fish and land-living animal both in terms of its anatomy and its way of life," says Neil Shubin, professor and chairman of organismal biology at the University of Chicago.

Warnings about fish consumption and mercury overstated

50443248 — Fri, 20 Jul 2007 12:24:16 -0400

A comparison of the risks and benefits of fish consumption suggests that government advisories warning women of childbearing age about mercury exposure should be issued with caution. The study warns that if advisories cause people to eat less fish out of fear about the effects of mercury, substantial nutritional benefits could be lost. The study will appear as a series of five articles in the November issue of the American Journal of Preventive Medicine.
"Fish are an excellent source of omega-3 fatty acids, which may protect against coronary heart disease and stroke, and are thought to aid in the neurological development of unborn babies," said Joshua Cohen, lead author and senior research associate at the Harvard Center for Risk Analysis at the Harvard School of Public Health (HSPH). "If that information gets lost in how the public perceives this issue, then people may inappropriately curtail fish consumption and increase their risk for adverse health outcomes."

Fish are a major source of mercury exposure, a neurotoxin that may cause subtle developmental effects in utero, like the loss of a fraction of an IQ point, even at the modest exposure levels typical of the American population. As a result, the U.S. Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) have issued advisories warning women of childbearing age about mercury in fish.

Because fish are also a good source of omega-3 fatty acids, the advisories have had to walk a fine line. The most recent U.S. government advisories emphasize that other adults need not worry about mercury in fish. They even advise women of childbearing age to keep eating fish, although they caution that group to keep away from some species (shark, swordfish, king mackerel, and tilefish) likely to contain more mercury and to limit total fish intake to about two meals a week.

Scientists show how fish save energy by swimming in schools

70652986 — Mon, 26 Mar 2007 05:32:59 -0400

Researchers at Harvard University and the Massachusetts Institute of Technology have provided new insights into the hydrodynamic benefits fish reap by swimming in schools. "The annual upstream voyage of fish to spawn has long been viewed as one of the classic struggles of the natural world, but our work suggests that this journey may not be nearly as exhausting and heroic as it appears," says author James C. Liao, a graduate student in Harvard's Department of Organismic and Evolutionary Biology. "Rather than swimming blindly upstream through turbulence, swimming fish use specific body motions to yield to natural eddy formations, using energy in the environment to direct their bodies upstream without much muscular investment." The results are reported in the Nov. 28, 2003 issue of the journal Science. Liao was joined in this research by George V. Lauder, professor of biology and Alexander Agassiz Professor of Zoology in the Museum of Comparative Zoology at Harvard, and by David N. Beal and Michael S. Triantafyllou at M.I.T. The work was supported by grants from Sigma Xi, the American Museum of Natural History, the Robert A. Chapman Memorial Scholarship at Harvard, and the National Science Foundation, as well as an M.I.T. Sea Grant.

Men can reduce stroke risk by eating fish

70652986 — Mon, 26 Mar 2007 05:27:27 -0400

Researchers tracked the diet and health outcomes of more than 43,000 male participants for 12 years. Using detailed food frequency questionnaires, participants were asked how often they ate fish, ranging from never or less than once per month to six or more times per week. The men in the study were also asked about four different fish items: canned tuna fish, dark meat fish such as mackerel, salmon sardines, bluefish and swordfish; other fish and shrimp, lobster, or scallops served as a main dish. The researchers assessed the effect of long-chain omega-3 polyunsaturated fatty acid, a constituent of fish believed to have healthful effects, on the risk of ischemic stroke (blood flow to a certain area of the brain is interrupted). They found that men who ate even a small amount of fish, one to three times per month from any of the fish categories, reduced their risk of ischemic stroke by 40 percent. There was no evidence of further risk reduction of stroke by consuming fish more often. The findings appeared in the Dec. 25, 2002, issue of the Journal of the American Medical Association.

Researchers regenerate zebrafish heart muscle

70652986 — Mon, 26 Mar 2007 05:28:39 -0400

A research team led by Mark T. Keating showed that zebrafish can regenerate heart muscle within two months after a severe injury. The team, from the Howard Hughes Medical Institute at Children's Hospital Boston, also identified a possible genetic and molecular model for regeneration in zebrafish that could help direct further research in humans. The findings, while still in an early stage, might someday benefit millions of people who suffer heart attacks or experience other forms of cardiac injury. The zebrafish is the subject of active study because of its ability to regenerate spinal cord, retina, and fins. This finding points to the study of zebrafish heart regeneration as a means to understand and reduce cardiac injury in humans. When a human heart is injured, it cannot "grow back" the damaged muscle, which is instead replaced by scar tissue. Too much scarring can impair the heart's ability to pump and can lead to life-threatening arrhythmias. Keating and his colleagues believe that zebrafish, unlike humans, have especially vigorous development of new heart-muscle cells, or cardiomyocytes. This proliferation of cells regenerates the heart muscle with little or no scarring. The research was reported in the Dec. 13, 2002 issue of Science.

Eating fish may reduce risk of sudden death

70652986 — Mon, 26 Mar 2007 05:20:40 -0400

Researchers at Harvard Medical School and Harvard School of Public Health have been following the health of more than 22,000 male doctors since 1982. They examined fatty acids from fish in the blood of 94 of these men who died suddenly and compared the results with 184 living men matched for age and how much they smoked. Those with the highest levels of fatty acids from fish in their blood had an 81 percent lower risk of sudden death than those with the lowest levels. "Overall, the higher the amounts of omega-3 fatty acids climbed in blood samples, the greater sudden-death-risk was reduced," said Christine Albert, leader of the study. The results were reported in the April 11, 2002, issue of The New England Journal of Medicine. Another study, conducted at the Harvard School of Public Health, followed 84,688 female nurses. "Our research suggests that women can reduce their risk of heart disease by more than 30 percent by eating fish two to four times a week," said Frank Hu, leader of the study and an associate professor of nutrition and cardiovascular disease. Hu's team reported their results in the April 2002 Journal of the American Medical Association.

Fish may reduce risk of stroke in women

70652986 — Mon, 26 Mar 2007 05:12:19 -0400

"Our research suggests that women can reduce their risk of thrombotic stroke by up to 48 percent by eating fish two to four times per week," said Kathryn M. Rexrode, Harvard Medical School instructor in medicine. "The findings also indicate that higher intake of omega-3 fatty acids may help women reduce their risk of stroke." Using data on nearly 80,000 women participating in the Brigham and Women's Hospital-based Nurses' Health Study, researchers found that women who ate fish once a week had a 22 percent lower risk of developing all kinds of stroke than people who ate fish less than once a month. Those who ate fish two to four times a week had a 27 percent lower risk.

Understanding how fish swim

70652986 — Mon, 26 Mar 2007 05:08:28 -0400

The pattern is hard to see at first because the movement seems to happen in the blink of an eye. The only thing that makes it visible at all is the fact that the bluegill sunfish in George Lauder's experiment is swimming through water that is awash with tiny silvery glass beads that catch the light and reveal the fluid's movement. "That's the fish's pectoral fin," Lauder says, pointing to the grainy, black-and-white-picture. "It's slowed down because the camera was taking 250 images per second. But do you see the way the water is moving in a sort of loop behind it?" Lauder is in the midst of conducting what may be the most thorough and technologically sophisticated study to date of how fish swim.