Published: April 07, 2008 01:21 pm            

Eel-like fish makes rare appearance

Chestnut lampreys haven’t been found in Iowa interior rivers for more than 100 years

CENTERVILLE, Iowa — Serendipity is the effect by which one accidentally discovers something fortunate, especially while looking for something else entirely.

Mark Flammang , an Iowa Department of Natural Resources fisheries management biologist, had a first hand brush with serendipity as he and other DNR employees were shocking and netting walleye fish below the Rathbun Lake Dam. Walleyes seeking favorable spawning grounds near the dam have been finding themselves suddenly whisked into the Chariton River. The captured fish were being returned to the lake.

As the DNR boat navigated the churning waters near the spillway, the electrical shocks suddenly brought up more than stunned walleyes - a chestnut lamprey. Just the day before Flammang had finished a research paper called, “The Occurrence of Chestnut Lamprey in the Chariton River in South-Central Iowa.”

Catching the lamprey for Flammang meant staying up that night to include the latest find in his study.

Flammang calls the lampreys living fossils. Their fossil records go back 300 million years and are among the most primitive of living vertebrates.

Flammang admits the parasitical creature is not cute or cuddly, but finding the endangered animal is a “good indicator that something good is going on” with the water quality of the Chariton River. To date, no chestnut lampreys have been found in Iowa’s interior rivers for more than 100 years except the Chariton River. Though more numerous in the South, the eel-like fish are rare in the section of the Mississippi River bordering Iowa and they are rarely encountered in the Missouri River north of St. Joseph.

Flammang points out that the chestnut lamprey should not be confused with the larger, salt-water lamprey that invaded the Great Lakes in the 1920s. Those larger lamprey are destructive to fish populations, while there are seldom fatalities connected with the chestnut lamprey - and those usually are caused by infections at the bite site.

The chestnut lamprey - Ichthyomyzon castaneus (from the Greek "fish to suck", a reference to its feeding habits, and castaneus from the Greek "chestnut colored") is one of four lamprey species known to live in Iowa waters. Only two lampreys are parasitic - the silver and the chestnut.

The adult chestnut lamprey can reach a foot in length. The first five years of its life are rather non-eventful, spent as a larvae nestled in sand and dark mud while living off drifting plankton and detritus.

As an adult, the chestnut lamprey lives for only about 18 months. Spawning occurs among rocks in sand during late spring and early summer.

The most frequent host for the chestnut lamprey is the common carp, but they are also found on other scaled fish.

“From 1996 to 2002, several anglers in the Chariton River below Lake Rathbun described catching fish with lamprey attached,” wrote Flammang in his research paper. “Host species included common carp (Cyprinus carpio), bigmouth buffalo (Ictiobus cyprinellus), bighead carp (Hypophthalmichthys nobilis), and largemouth bass (Micropterus salmoides).

“However, none of these lampreys were collected and identified to species. On 17 April 2002, an angler fishing in the Chariton River just below the outlet of Rathbun Lake caught a common carp to which a lamprey was attached. The angler brought the lamprey to IDNR fisheries biologists who identified and preserved the specimen; this lamprey was 273 mm in total length. Another specimen was identified on 3 February 2003 from the same location. However no measurements were taken and this fish was released alive.”

These were the only two documented finds of the lamprey on the Chariton until Tuesday. That lamprey was preserved for the University of Iowa Hygienic Laboratory reference collection. Any other lamprey collected below the dam, said Flammang, would be released back into the river.

How did the chestnut lamprey population come to be at the site? Flammang believes they traveled on host fish up the Chariton from the Missouri River.

“The historic occurrence of chestnut lampreys in this river segment is doubtful,” writes Flammang. “None of the previous fish surveys of the Chariton River (for example, Jordan and Meek 1885, Harrison and Speaker 1954, and Harlan and Speaker 1956)—including a fish survey conducted on the Chariton River just prior to the 1969 impoundment of Lake Rathbun (Mayhew 1965)—produced records for this species.”

The DNR biologist based at the Rathbun Fish Hatchery says there are two likely possibilities.

“The lampreys moved up the Chariton River from the Missouri River attached to highly mobile host species, such as common carp, during recent high-flow events,” Flammang conjectured. “For example, the prolonged high river flows in the Chariton River and most other Iowa rivers in summer 1993, no doubt, induced more upstream movement than normal of fish such as common carp, and parasitic lampreys may have thus moved upriver in the Chariton as far as the barrier presented by Rathbun Dam.”

The second possibility he puts forward is, “The lampreys moved up the Chariton River from the Missouri River attached to the highly mobile bighead carp as the distribution of this non-native species rapidly expanded northward into Iowa waters during the 1990s.



Dan Ehl writes for Daily Iowegian in Centerville, Iowa.

        

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