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Bits & Pieces: Asian Carp, North with Doc, and Fish Shrinkage

Blending fishery science with everyday fishing.

Bits & Pieces: Asian Carp, North with Doc, and Fish Shrinkage

The Illinois DNR reports that Asian carp (rebranded as Copi) are mild fish with healthy omega-3s and low levels of mercury, and increased harvest could help reduce Asian carp abundance and their ecological disruptions. 

This article originally appeared in the October-December 2022 issue of In-Fisherman.


Copi: Carp with a New Name

The Illinois Department of Natural Resources (DNR) announced that after more than two years of consumer research and planning, the State of Illinois has come up with a new name for Asian carp (silver, bighead, and grass carp).* According to the DNR, the new name, Copi, is designed to address public misconceptions about these fishes that many find as fine table fare, and which are overpopulating in many midwestern waterways.

The DNR reports that Copi are mild fish with healthy omega-3s and low levels of mercury, a heavy metal typically in higher concentrations in predator fish species. Increased harvest could help reduce Asian carp abundance and their ecological disruptions.

The name Copi reflects their “copius” abundance in many waterways. The DNR reports that 20 million to 50 million pounds of Copi could be harvested from the Illinois River each year, with hundreds of millions more in waters from the Midwest to the Gulf Coast.

Other fish species have undergone name changes to make them more marketable, the DNR says. Orange roughy was originally called slimehead and Chilean sea bass was known as Patagonian toothfish.

A sub sandwich.
A Copi Po’ Boy prepared by Chef Brian Jupiter. (Alex Garcia photo)

More chefs and retailers have committed to putting Copi on their menus or in their stores, and processors, manufacturers, and distributors are making Copi products more available, the DNR reports.

“Copi is more savory than tilapia, cleaner tasting than catfish, and firmer than cod,” says “Chopped” champion and chef Brian Jupiter, who revealed the new name and will serve Copi at his Ina Mae Tavern in Chicago. “It’s the perfect canvas for creativity—pan fried, steamed, broiled, baked, roasted or grilled. Copi can be ground for burgers, fish cakes, dumplings, and tacos.” [Recipes using Copi can be found at choosecopi.com.]

The DNR says Illinois officials will apply to formally change the name with the U.S. Food and Drug Administration by the end of the year. When sold in grocery stores, the packaging will list the fish as carp and Copi until the name change is approved.  

Asian carp, native to Southeast Asia, were introduced into to the United States to help improve water quality in fish farm ponds. Flooding in the 1970s allowed them to escape and establish populations in the Mississippi River drainage.




-In-Fisherman

*Illinois Department of Natural Resources news release. June 2022. Choose Copi: Eat Well and Do Good. dnr.illinois.gov.

Doc at the Drawing Board

Cartoon illustrations by Peter Kohlsaat .
Peter Kohlsaat has been the longtime illustrator for the North with Doc column, bringing Doc and the other characters to life and capturing the essence of each episode. (Peter Kohlsaat illustrations)

In this issue we celebrate columnist Greg Knowles’ achievement of 200 episodes of North With Doc. Peter Kohlsaat has been the longtime illustrator for the column, bringing Doc and the other characters to life and capturing the essence of each episode.

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Kohlsaat: “When the latest North With Doc arrives in my email from the magazine’s art director, Amy Jackson, I print it out, grab a pen, and make myself comfortable. I do an initial read-through, keeping alert for visual images. Some are obvious like Doc falling out of a boat or being attacked by bees while stepping ashore to heed nature’s calling. Sometimes Doc is mostly dialog and I’ve got to dig deeper. Potential image material is circled, underlined, or marked with arrows.

“During subsequent read-throughs, I make quick sketches in the margins or on the back side of the print-out. I’m looking for a lead illustration that depicts the gist of the piece, plus a little hint of what kind of mischief is to be encountered. I’m also on the lookout for spot illustrations that are to be sprinkled throughout the piece. Doc’s putrid cigar or super-sized cocktails are reliable go-tos.

“I sit at my desk, put on some music, and ink out the images, most often creating several different renditions until I feel it’s right. The black-and-white images are scanned into a computer and manipulated by a graphics program to render color. Then the illustrations are emailed back to In-Fisherman. Over the years the procedure has evolved. Early on there were no computers. It was colored pencils and the USPS.

“Throughout it all, I’ve felt honored to be part of the In-Fisherman family. And as long as Greg can amazingly, time after time, evoke the brotherhood of these characters in an annual Canadian fishing outpost, I will cherish being his wingman.”

From the Field­: Fish Shrinkage on Ice

Three crappies on the ice.
In a study done by Florida researchers, it was determined that there is significant evidence of postmortem shrinkage of several fish species stored on ice.

Accurate measurements of fish length are important in scientific assessments of the size structure of fish populations and for determining fish growth rates. Accurate measurements are also required of anglers who harvest fish, so that they’re in compliance with length-based regulations like minimum length limits. In addition to measurement errors and inconsistencies, how harvested fish are held (e.g., on ice) after capture and how long they’re stored also can affect fish length. Walleyes, for example, have been shown to shrink slightly when stored on ice.

To determine whether a variety of fish species experienced postmortem changes in length after being stored on ice, Florida researchers obtained black crappies, largemouth bass, sunfishes, and six species of catfishes from various fisheries projects.* They took initial measurements of total length (from the tip of the snout to the tip of the caudal fin, with the caudal fin compressed) immediately or within one hour of collection for fish held in livewells. After measurement, each fish was placed in an insulated cooler with cubed ice and kept for various time intervals. Fish were distributed in a single layer on a bed of ice, then each layer of fish was covered with a 3-inch layer of ice. Larger coolers held two layers of fish with top ice. Storage time intervals were 3 to 6 hours (Day 1), 24 hours (Day 2), and 36 hours (Day 3). At the end of each storage interval, fish were remeasured, using the same measuring board and same person who did the initial measurement as to avoid measurement bias.

A chart showing fish shrinkage when put on ice over time.
Average shrinkage among time intervals ranged from .76 to 1.22 percent for largemouth bass, .8 and 1.58 percent for catfishes, .43 to .96 percent for black crappies, and .83 to 1.29 percent for sunfishes.

A total of 595 fish were measured, including 144 largemouth bass (8.5 to 22.4 inches), 105 catfishes (7.5 to 34.4 inches), 212 black crappies (3.7 to 14.2 inches), and 134 sunfishes (0.5 to 11.6 inches). Average shrinkage among time intervals ranged from .76 to 1.22 percent for largemouth bass, .8 and 1.58 percent for catfishes, .43 to .96 percent for black crappies, and .83 to 1.29 percent for sunfishes. Largemouth bass and catfish had their lowest average shrinkage rates on Day 1, while percent shrinkage was similar on days 2 and 3. Sunfishes and crappies had the largest average shrinkages on Day 2. Not all fish shrunk, and the largest shrinkage for any fish never exceeded .71 inches.

The study confirms evidence of postmortem shrinkage of several fish species stored on ice. Although shrinkage appears minimal, it was as high as 0.71 inches for a catfish with an initial length of 25.4 inches. Based on these results, the authors of the study recommend law enforcement allow a shrinkage allowance of 0.25 inches for black crappies and sunfishes and 0.5 inches for largemouth bass and catfishes, when checking fish length for regulation compliance for fish stored in coolers. Anglers should be certain their initial measurements are accurate and meet regulation sizes. 

-Rob Neumann

*Dunn, K., Moran, J., Saxton, J., Lang, T., and K. Bonvechio. 2022. Quantifying and identifying factors influencing length changes in popular freshwater fishes preserved on ice. J. Southeast. Assn. Fish. Wild. Agencies. 9:54-60.

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