2002 Rum River fish population assessment summary

Sampling dates

9/4/02-9/19/02

Sampling method

boat electrofishing

Station 1

River mile 30, approximately 2 miles downstream from County Road 5 access in Isanti.

Station 2

River mile 48, near County Road 14 access northwest of Cambridge.

Station 3

River mile 57, approximately 1.5 miles upstream from Walbo Ferry boat access west of Cambridge on Highway 95.

Station 4

River mile 69.5, approximately 0.5 miles upstream from County Road 7 access west and north of Isanti.

Summary

A total of 18 species were caught by boat electrofishing on the Rum River. The most abundant fish were the redhorse species (silver, greater, shorthead, and river), making up 56% of the total catch. The most abundant game fish was smallmouth bass, at 15% of the total catch. Northern pike made up 9% of the total catch, while 4% of the catch was walleye. Common carp made up 10% of the total catch. Other species sampled less frequently were white sucker, rock bass, largemouth bass, yellow perch, bluegill, hybrid sunfish, and black bullhead. Three minnow species were also observed: spotfin shiner, common shiner, and golden shiner.

Smallmouth bass

The total catch of smallmouth bass in 4 sampling stations was 45 fish, with an electrofishing catch rate of 6.9 fish per hour. This was slightly lower than the 1997 catch rate of 10.2 fish/hour (63 fish). All of the smallmouth bass sampled were age 1 or older. Lengths of smallmouth bass were evenly distributed from 5 to 19 inches, indicating consistent reproduction over the past several years. With good body condition factors, consistent reproduction, and fairly consistent catch rate among stations, the smallmouth bass population was in very good condition in 2002.

Walleye

The total adult walleye catch was 11 fish, with an electrofishing catch rate of 1.9 fish per hour. This was slightly higher than the 1997 catch rate of 1.4 fish/hour. Most of the walleye were from 16.9-22.9 inches in length. Only one young-of-year walleye was caught. The walleye in the 2002 population were in relatively good condition the size structure of the population was good. The consistent catch rate from 1997 to 2002 indicated that the walleye population was maintaining itself in the river through natural reproduction. The only concern was the lack of smaller size classes of fish and low young-of-year catch in 2002 compared with the 1997 survey; this might affect angler catch of walleye in the next few years.

Northern pike

The total northern pike catch was 30 fish, 25 of which were adults and 5 young-of-year. The catch rate of adult northern pike, 3.7 fish/hour, was lower than the rate of 4.8 fish/hour in 1997. There was a large group of northern pike in the 21 inch length group, with the rest of the fish distributed evenly among length groups. The largest northern pike was 31.2 inches. With consistent catch rates and fish evenly distributed throughout all length groups, the northern pike population appeared to be in good condition in 2002.

Redhorse

As in the 1997 survey, in 2002 the greatest numbers of fish caught were the redhorse species. 78 silver redhorse, 63 greater redhorse, 19 shorthead redhorse, and 5 river redhorse were sampled. Based on comparisons with electrofishing catch rates from 1997, greater and river redhorse abundance increased, while silver and shorthead redhorse abundance decreased.