Flying Carp and the fun of a sensational news story

January 5, 2008

A few years ago I wrote a novel for young adults in which a few mutant fish grew to enormous size and terrorized guides and their clients around Chaffey’s Locks. The villain of the piece was an eco-terrorist with an electron microscope and a tray of smallmouth bass eggs. The idea had come when a colleague explained to me how at the University of Guelph they routinely disabled the DNA strand which stopped the growth process in salmon embryos, then sat back to see how big the hatchlings could get. She showed me pictures of healthy salmon fry which weighed thirty times those in the control group. I had also found a newspaper article which recounted a similar experiment in New Zealand where researchers eventually became afraid of their salmon when they surpassed 750 kg, took on an ugly green hue and sprouted hugely distorted lumps on their skulls. The researchers destroyed them all when an autopsy on one revealed that the creatures were fertile. The kids and parents who read the book thought it was fun, if a bit far-fetched, but it turns out I couldn’t make up anything half as wild as the stories which have appeared in prominent Canadian newspapers, Maclean’s Magazine, on CBC news and even the Internet about the latest threat sweeping up the Mississippi watershed and lurking in the fish markets of Toronto and Ottawa.

The monsters of the hour are silver and big-head carp, imported to the United States from Asia in the 1970’s to clear catfish ponds and sewage lagoons of algae. The myth holds that flooding of the Mississippi in the ‘90s released many of the voracious fish from captivity. This summer The Toronto Star’s Peter Gorrie reported that the silver and bighead carp “now make up more than 95 per cent, by weight, of all the animal matter in parts of the Mississippi system (Toronto Star, May 20, 2007).” Becky Cudmore, research biologist with Fisheries and Oceans Canada, reported that nine out of ten fish they sampled in the Illinois River were Asian carp (London Free Press, July 27, 2007).

A counterpoint came immediately from Duane C. Chapman, USGS Fisheries Biologist, when he saw my blog entry and sent along a much more sensible perspective on the carp infestation. He told me that an individual net may very well haul out all carp, but that doesn’t mean that the river is full of them. He sent me some census statistics that showed very few carp in the system even though the commercial harvest of silver and bighead carp was expanding exponentially at the time. He explained that a lot depends upon where you look and the type of net you use. Chapman made it clear that the 95% statistic is a wild exaggeration.

No one questions, however, the silver carp’s reputation for bizarre behaviour: when startled by an outboard motor the fish leap up to eight feet out of the water, often landing in the boat. YouTube has a number of videos of this spectacular activity. Internet clips of tourists getting shelled by large silver fish are fun to watch, but I certainly wouldn’t want it to happen on Newboro Lake. In one of the USGS publications which I read the author commented that the leaping fish have made it prohibitively dangerous to water ski on the Illinois River. He likened impact from leaping fish to getting hit by bowling balls at random intervals. The Lacey Act (2006) itself refers to the tremendous leaping power of the silver carp creating a hazard for boaters and fishermen.

At some point in Chicago’s checkered past engineers dug a canal to divert sewage south to the Mississippi in an attempt to lessen pollution levels in Lake Michigan. Thus the Great Lakes and the Mississippi Watershed are connected by the Illinois River. For years the untreated runoff from meat processing plants and heavy industries protected Lake Michigan from the carp invasion through the Chicago canal, but now the EPA has forced polluters to clean up their act, allowing the carp a non-toxic route north.

At the moment all that stands in the way of a fully-blown invasion is a system of electrodes rigged across the canal to deter the fish. Imagine one of those invisible fences for your dog. Commercial tugs still move barges through this canal, so the water carried in the vessels’ bilges is a major threat to the the Great Lakes. You may recall that zebra mussels hitched a ride from the Adriatic in the bilges of freighters a few years ago.

Even scarier are older news stories still current on the Internet. One reports an Asian carp caught in the St. Clair River by a commercial fisherman, but spookiest of all is the report that bighead carp are available live in fish markets in Ottawa and Toronto. (Zev Singer, The Ottawa Citizen, Thursday, March 13, 2003). The Ontario Government quickly banned the live sale of carp in 2004, and required that only sterile carp be allowed live into the country.

Duane Chapman explained that The Lacey Act in 2006 added the silver carp and the large-scaled silver carp to its list of injurious wildlife species, thus banning the transportation of the fish across state lines or out of the country. The act bans both diploid and triploid versions of the fish, but Chapman pointed out that there is no such thing as a triploid (genetically sterile) silver or bighead carp. Only for the very different grass carp have scientists developed a sterile variant. Still, with the ban stopping the traffic from Arkansas to Ontario, the odds of a live adult silver carp hopping out of a tank and into the Rideau River are very low.

But the Ontario Ministry of Natural Resources reports another disturbing trend: fully half of minnow buckets are dumped back into the lake at the end of fishing trips, and a carp fry looks very much like any of its cousins in the minnow family.

Chapman emphatically agrees on this point: “These fish are easy to transport in a bait bucket, as are many other undesirable fish, and diseases. Wild-caught bait should never, ever, be used in a body of water other than where it was captured, whether you release your bait afterward or not. Purchased bait should not be released alive.”

The reason for the alarm is that these species of carp have a reputation for eating their way through the entire ecosystem of a lake. The only disagreement has to do with how quickly they can do it. The papers this year have claimed that a female silver or bighead can lay one or two million eggs at a hatch. (The Lacey Act offers a more modest figure of 400,000 eggs for a large female.) They reach spawning maturity early, and they compete relentlessly with native species. Chapman’s current research concerns the analysis of how much damage the silver and bighead carp have done to the areas they have invaded.

“I have data … that shows that zooplankton populations in the low velocity habitats used by bighead and silver carps (together, known as the “bigheaded carps”) are MUCH lower than prior to the invasion. These things do not bode well for native fishes, especially fishes that require the same habitats as bigheaded carps and that are planktivorous throughout their life (like paddlefish, bigmouth buffalo, and the important preyfish gizzard shad). But we have not yet been totally overrun by these fish to the loss of all our native fish. Our primary sportfish here in the Missouri River is catfish, and the catfishing is still world class. Time will tell what we see in the future. Predictions are tough, although risk assessments on these fish are uniform in the opinion that it would be risky to have these fish invade.”

Perhaps Maclean’s writer Danylo Hawaleshka exceeded the mark last summer when he wrote “The barbarian is at the gate!” but the message is clear to the fishermen of Ontario: if you don’t want to get shelled by flying carp, take great care with your minnow bucket.

References:

Correspondence with Duane C. Chapman, Research Fisheries Biologist, United States Geological Service, Columbia Environmental Research Center, January, 2008.

Peter Gorrie, The Toronto Star, Gluttony, thy name is Asian Carp, May 20, 2007

http://ottawariverkeeper.ca/news/invasive_asian_carp_sold_alive_in_ottawa_fish_markets/

http://cnews.canoe.ca/CNEWS/Science/2007/0…373151-sun.html

http://www.dfo-mpo.gc.ca/csas/Csas/status/2005/SAR-AS2005_001_e.pdf

http://www.macleans.ca/article.jsp?content=20060417_125346_125346

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3 Responses to “Flying Carp and the fun of a sensational news story”

  1. Duane Chapman Says:

    These fish are a real problem, no doubt. But some of the information reported here, though it comes from other media sources, can be classified as hyperbole. Yes, when capturing Asian carp, it is easy to get a net with 95% of the fish in Asian carp – if you target them. Long term resource monitoring data http://www.umesc.usgs.gov/data_library/fisheries/fish_page.html on the Illinois River, however, using a variety of nets and capture styles, paint a very different picture. There is no evidence that the fish make up 95% of the biomass of any river section, though it is easy to catch a net that is well over 95% of the weight it Asian carp.
    Live bighead and silver carp have been banned from Ontario, regardless of their sterility, and there are not and never have been sterile triploid bighead or silver carp available on the market. I must say I am not sure about the legality of selling live grass carp – which are available triploid, but are a very different sort of fish from the bighead and silver carps. The referenced article was written prior to the ban on bighead and silver carp. Silver carp are now banned, by US law (Lacey Act) from being transported in or out of the country or over state lines.

    Nevertheless, I appreciate your spreading the word about these undesireable species, especially the bit about bait bucket transfer. These fish are easy to transport in a bait bucket, as are many other undesireable fish, and diseases. Wild-caught bait should never, ever, be used in a body of water other than where it was captured, whether you release your bait afterward or not. Purchased bait should not be released alive.

  2. Duane Chapman Says:

    Also, I wanted to add that these fish are among the invasive species for which we are beginning to show demonstrable harm to native fishes and enviroments. This is harder to do than you might imagine, from a scientific standpoint. We are seeing that competing fishes are growing slower and are not as fat, and that zooplankton resources which all fish feed on are down after the invasion of bighead and silver carps.

    Also, I did want to add that the oft-repeated statement, everywhere in the media, that the fish originally escaped in huge floods of the nineties is just not supportable with facts. The fish were present in the wild in the USA prior to the nineties. We don’t know how they escaped. Many people believed these fishes could not survive and reproduce in the rivers of the USA, so perhaps people just were not careful about keeping the fish from escaping.


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