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Sunday
Apr192015

Largemouth Bass Chow Down on Bighead Carp in Lab Tests

Bighead carp grow large. But bass eat them when they're smalll and more vulnerable

“Asian carp” actually refers to two species of exotic fish, not one. As they spread throughout the nation’s rivers, both pose threats to native fisheries.

As it turns out, though, there seems to be a big difference in their vulnerability to predation. That’s bad news for bighead carp, which grow larger, feed more exclusively on zooplankton, and are less abundant. And good news for the smaller silver carp, which have become infamous for endangering boaters with their leaping antics.

Researchers at the Illinois Natural History Museum and University of Illinois put small samples of both into experimental pools, along with bluegill, gizzard shad, and golden shiners. Largemouth bass in those pools ate more bighead carp than any other species, including silver carp. Scientists hypothesized that this may mean that young silver carp are more “street smart” than their bighead cousins.

While it’s good to know that bass can and likely do eat these invaders, especially bighead carp, whether this predation will help control them remains to be seen.

“Although new research is confirming that native fish can and do consume Asian carp, this not mean that all is well,” cautioned the Michigan State University Extension (MSUE). “In the LaGrange Reach of the Illinois River, at least seven native fish are preying on Asian carp. Even so, this reach has one of the highest densities of silver carp recorded anywhere in the world.

“Native plankton-eating fish like gizzard shad and bigmouth buffalo have declined and the long-term effects on gamefish are still uncertain.”

In 2008, biologists estimated more than 5,000 silver carp per mile in that nearly 80-mile stretch of the river, with a biomass of 705 metric tons.

“In the Great Lakes, we already know that native fish are adapting to non-prey items like quagga mussels and round gobies,” MSUE continued. “We also know that predation has not been enough to eliminate these species or prevent their negative effects. The same is likely true for Asian carp.”

(This article appeared originally in B.A.S.S. Times.) 

Friday
Apr172015

The Best Time to Fish . . . 

"Angling is extremely time-consuming. That's sort of the whole point." Thomas McGuane

“The two best times to fish is when it’s rainin’ and when it ain’t.” Patrick F. McManus

Why We Fish--- Reel Wisdom From Real Fishermen

“Nothing grows faster than a fish from when it bites until it gets away.” Anonymous

“Catch and Release fishing is a lot like golf. You don’t have to eat the ball to have a good time.” Anonymous

“If fishing is interfering with your business, give up your business.” Alfred W. Miller

Thursday
Apr162015

Human Drugs Harming Fish Fertility

Prescription drugs intended for humans are affecting our fisheries in frightening ways. That's because they or their residues are flushed down toilets and into our waterways. Birth control pills are among the most concerning because they affect fertility in bass and other species.

For example, a recent study by the U.S. Geological Survey found that fish exposed to a synthetic hormone called 17a-ethinylestradiol, or EE2, produced offspring that struggled to fertilize eggs. The grandchildren of the originally exposed fish suffered a 30 percent decrease in their fertilization rate. The authors mulled the impact of what they discovered and decided it wasn't good.

"If those trends continued, the potential for declines in overall population numbers might be expected in future generations," said Ramji Bhandari, a University of Missouri assistant research professor and a visiting scientist at USGS. "These adverse outcomes, if shown in natural populations, could have negative impacts on fish inhabiting contaminated aquatic environments."

Read more here.

Additionally, check out this previous post at Activist Angler about minnows exhibiting bizarre behavior because of drugs.

Wednesday
Apr152015

Oil Spill's Impacts to Gulf Fish, Wildlife Revealed in NWF Report

Photos by Robert Montgomery

Five years following the Deepwater Horizon oil spill, National Wildlife Federation  (NWF) scientists have compiled a report detailing how 20 types of fish and wildlife were impacted by the pollution that continued for 87 days.

NWF said, “The full extent of the spill’s impact may take years or even decades to unfold , but Five Years & Counting: Gulf Wildlife in the Aftermath of the Deepwater Horizon Disaster examines what the science tells us so far.”

The report does not suggest that fishing is not good or that it will not continue to be so.

Following are updates on two species:

The mahi-mahi, also known as dorado, is an economically important species in the northern Gulf.

Like many fish, mahi-mahi produce fertilized eggs that float in the upper layers of the water column. Mahi-mahi were spawning at the time of the oil spill and it is therefore likely that their eggs and larvae were exposed to oil during 2010.

Larval or juvenile exposure to a chemical in oil from the Deepwater Horizon has been shown to cause significant developmental impacts in a number of fish species. Similar research in mahi-mahi corroborates these findings. Embryonic or juvenile mahi-mahi briefly exposed to Deepwater Horizon oil were later unable to swim as fast as unexposed fish. The concentrations of oil in the study were designed to mimic conditions in affected areas of the Gulf.

This could translate into increased mortality, as slower fish would likely be less able to catch prey or avoid predators.

These studies could help explain “crude oil toxicity syndrome,” which has been observed in a number of fish species, across both fresh and saltwater habitats.

Additional research has recently been funded that will look further into impacts in redfish and mahi-mahi.

White and brown pelicans in Texas' Galveston Bay

American white pelicans nest in colonies of several hundred pairs on islands in remote inland lakes in North America, and they winter on the Pacific and Gulf Coasts.

Most white pelicans were in their northern breeding grounds at the time of the spill.

Two years after the spill, however, researchers found evidence of oil and dispersant in the eggs of white pelicans nesting in Minnesota. Scientists made this discovery at Marsh Lake, which is home to the largest colony of white pelicans in North America.

Petroleum compounds were present in 90 percent of the first batch of eggs tested. Nearly 80 percent contained the chemical dispersant used during the Gulf oil spill. White pelicans could have been contaminated while wintering in the Gulf, either through direct contact with remaining oil and dispersant or by eating contaminated fish.

Long-term increases in breeding pairs in Minnesota have occurred since 2004, but from 2011-2012 the breeding population has essentially stabilized.

Scientists from the Minnesota Department of Natural Resources are continuing to investigate the impacts of these compounds, which have been known to cause cancer and birth defects and to disrupt embryo development in other species.

Contaminated eggs have been found in two other states as well. In 2012, staff at the Upper Mississippi National Wildlife Refuge collected eggs that failed to hatch from pelican colonies in the Iowa and Illinois portions of the refuge.

Population declines in migratory shorebirds and reduced breeding productivity may have an impact on ecosystems outside the Gulf region. Therefore it is important to link wintering and breeding locations for migrant species in order to fully understand the impacts of the Gulf oil disaster.

Tuesday
Apr142015

Chasing Rainbows

We got up at 4:15 a.m. to be on the water at 5. Unfortunately, the fish didn’t seem to care that we were there.

Then the rain started. It wasn’t all over. Mostly it was to the west and a little bit overhead.

In the east, where the sun hadn’t yet moved above the horizon, the sky was mostly clear.

And then came the magic. With the sun beaming up from below the skyline, my friend Norm Klayman and I watched the formation of the most spectacular rainbow that either of us had ever seen. 

Normally, I don’t bother taking photos of rainbows. Even with digital, I’ve learned that cameras just can’t do them justice. But with this one, I had to try, even though it was far too large for me to photograph in its entirety. The picture (above) turned out better than I expected. Still, it doesn’t compare to what we saw with our own eyes. 

If someone had asked me to get up at 4:15 to go see a rainbow, I might have said, “No, thank you. I’ve seen plenty of them.”

Yet I’m always ready to get up at such hours to go fishing. And if I hadn’t gone fishing on this morning, I would have missed a sight that I will treasure for the rest of my life.

Of course, that rainbow isn’t the only example of how nature has provided collateral enrichment during my time on the water. I could tell you about hundreds more. Probably you could do the same.

Here are a few more of my favorite nature-inspired memories:

From "Chasing Rainbows" in Why We Fish