Stories tagged fish

Oct
15
2010

Tasty fish & tomatoes
Tasty fish & tomatoesCourtesy Robert and Mihaela Vicol
Fish and tomatoes compete for resources.

Yep, they do, and that resource is water.

The authors of a new report out in this week's issue of the journal Science are reminding folks of that fact.

John Sabo, a biologist at Arizona State University and lead author of the report told NSF News that "Humans may need to make hard decisions about how to allocate water so that we grow the right food, but still leave enough in rivers to sustain fish populations."

His comments stem from the report's findings that human actions--agricultural irrigation, dam construction, and the collective activities that lead to climate change--alter the natural variability of river flows and in the process shorten river food chains, particularly eliminating top predators like many large-bodied fish.
A now dry Colorado River delta branches into the Baja/Sonoran Desert near the Sea of Cortez
A now dry Colorado River delta branches into the Baja/Sonoran Desert near the Sea of CortezCourtesy Pete McBride

"Floods and droughts shorten the food chain, but they do it in different ways," Sabo explained. "Floods simplify the food web by taking out some of the intermediate players so the big fish begin to eat lower on the chain," Sabo said. "With droughts, it's completely different: droughts eliminate the top predator altogether because many fish can't tolerate the low oxygen and high temperatures that result when a stream starts drying out."

Sabo and co-authors--Jacques Finlay, from the University of Minnesota, Theodore Kennedy from the U.S. Geological Survey Southwest Biological Science Center, and David Post from Yale University--suggest that the fate of large-bodied fishes should be more carefully factored into the management of water use, especially as growing human populations and climate change affect water availability.

According to Sabo, "The question becomes: can you have fish and tomatoes on the same table?"

The Role of Discharge Variation in Scaling of Drainage Area and Food Chain Length in Rivers
John L. Sabo, Jacques. C. Finlay, Theodore Kennedy, and David M. Post (14 October 2010)
Science [DOI: 10.1126/science.1196005]

[It's Blog Action Day 2010, and this year's theme is water.]

It's Friday, so it's time for a new Science Friday video. (I know, I've missed a few weeks. Sorry about that.) Science Friday
Science Friday
Courtesy Science Friday
"Based on mathematical models of the movement of fish, Maurizio Porfiri, an engineering professor at Polytechnic Institute of NYU, designed a robotic fish. When Porfiri puts the robofish in the lab pool with real fish, the minnows (golden shiners and giant danios) will mill about the robot and even follow it around.
Jul
05
2010

Much attention and debate is focused on the role of human releases of carbon dioxide (CO2) in global warming and climate change but there is another facet of CO2 that deserves much more attention. Increasing concentrations of CO2 in the atmosphere lead to more and more CO2 dissolving into the oceans where it turns into carbonic acid. A story in the June 18 issue of Science reports that there is no doubt whatsoever that human releases of CO2 are acidifying the oceans at a scale unprecedented in the geologic record.

The closest analogue to present day appears to be the Paleocene-Eocene Thermal Maximum (PETM) of 55.8 million years ago. Over the course of several thousand years, huge amounts of methane and CO2 entered the atmosphere (where the methane was quickly converted to CO2). Much of this CO2 dissolved into the oceans, causing a drop in ocean pH. The difference between the present and the PETM is that human releases of CO2 are occurring at a rate at least ten times faster. At takes about 1,000 years for CO2 dissolved in surface waters to reach the deep sea where sediments eventually neutralize the acid. Human releases of CO2 currently far exceed the rate at which the oceans are able to remove it and so the result is a rapid drop in the pH of surface waters.

Many ocean organisms make their shells from carbonate. Acidification changes carbonate into bicarbonate and hydrogen ions, making the mineral much less available to tropical corals, echinoderms, mollusks, and foraminifera. The danger if ocean acidification continues unabated is potentially dramatic and unpredictable changes in marine life everywhere.

Some policymakers and scientists increasingly are raising the idea of perhaps mitigating the effects of climate change through large-scale geoengineering projects intended to reduce the amount of solar energy reaching the Earth’s surface as a last ditch effort to counteract the effects of greenhouse gas warming. Such projects would do nothing to mitigate the growing problem of our acidifying oceans. The only way to reduce ocean acidification is to reduce globally the quantities of CO2 that humans release into the atmosphere.

It was working: until my 'stache fell off. AGAIN!
It was working: until my 'stache fell off. AGAIN!Courtesy JGordon
Male Mexican molly fish grow "sexy mustaches" to attract female fish. Me too.

I hate to lead the fish on, but sometimes I can't help myself.

Feb
08
2010

Viral hemorrhagic septicemia: a fish infected with the virus
Viral hemorrhagic septicemia: a fish infected with the virusCourtesy Dr. Mohamed Faisal
No… not a rock bass (even though it has a red iris). Nor any normal walleye you might be lucky enough to snag. This fish you might not even need to actually catch. It could be floating next to the boat along with most of the other fish in your favorite river, lake, or reservoir. That is if the dreaded VHS continues to spread and strike us deep in the land of 10,000 lakes. Move over zebra mussel, Eurasian milfoil, and the Asian carp, VHS is viral hemorrhagic septicemia and the latest migrant in the spread of invasive species.

Viral hemorrhagic septicemia (VHS) is a virus. It is a small invading critter that can be quite infectious. Not all fish will show obvious signs. Those that do can exhibit hemorrhaging in the eyes, around the fins, or on the gills. Bloating, erratic behavior, bulging eyes, or even lesions could also be present. On the inside, the disease will attack the liver, kidneys, spleen or swim bladder. Those fish that do survive can still be infected and spread the disease. Blood, urine and even the reproductive fluids of infected fish can pass on the virus. Larger fish can get it from eating smaller infected fish.
Fish kill: sights like this are all the more possible with the new viral invader
Fish kill: sights like this are all the more possible with the new viral invaderCourtesy JoelDeluxe

The disease can be wide spread and is known to affect up to 28 different species of fish. Some of the fish kills have numbered in the tens of thousands. Many of our popular game fish are susceptible. Walleye, Northern Pike, Muskellunge, Smallmouth Bass, Perch, Crappies, Bluegills, Sheepshead and many others are on the list. Even some species of shiner bait fish have been found to carry the disease. While deadly for many fish, the disease is of no harm to humans. The warmth of our bodies is too hot for the virus to survive.

The virus has been known for many decades, but until recently was mainly a scourge of European fish farms. Viral hemorrhagic septicemia was first detected in American coastal waters in 1988, among the salmon populations of the Pacific Northwest. Then in 2005, tested fish showed up positive between Lake Huron and Lake Erie, and were confirmed in samples harvested two years earlier. Now, local news just recently reported on a Cornell study that found VHS diseased fish in the bay waters of the Duluth-Superior harbor on the western edges of Lake Superior. Make no mistake… the ‘bleeding fish’ disease is here at our doorstep.

Guests of the inland waterways will be reminded to be vigilant in safe boating and fishing practices by local resource managers. Be mindful not to transport fish, plants, or bait from one water body to another. Keep those live-wells empty, and dry or rinse that boat! It will fall upon all of us to remain vigilant. Let’s not allow this disease to become a crippling blow to our native fisheries. If we do, it is possible that we’ll witness many seasons of massive fish kills.

More good VHS information:
Wisconsin Dept. of Natural Resources

Univ. of Wisconsin Sea Grant

Too cold
Too coldCourtesy Petruha
Millions of fancy fish are dying because of the cold snap in Florida. Florida businesses that raise fancy fish to sell in pet stores are getting devastated.
Learn more about the 2010 Florida fish kill here.

Named the Kuroshio Sea, this enormous tank at the Churaumi Aquarium in Okinawa, Japan is over 30 feet deep, 110 feet wide, and nearly 90 feet long. It holds more than 8000 tons of water, equal to about three Olympic-sized swimming pools. Eighty local species of fish are on display here including manta rays, and the world's largest fish, the whale shark.

You have to admit, this is some of the best reality television you've seen lately.

A new study has found that about 20 percent of all male black bass in U.S. waters have female sexual characteristics. Here's more than you probably want to know about this. The only U.S. waters without any feminized black bass are in the manly waters of the Yukon River basin of Alaska.

Otoliths are from fish ears
Otoliths are from fish earsCourtesy Edgewise

I know what the "Object of the month" is for June 09 but I guessed wrong for the one in June 01. I thought it was an otolith.
Boing Boing just did a post on otoliths. You might want to check it out and learn tidbits like:

By properly counting the annuli or growth rings you can tell how old a fish is.