Bits & Pieces: Nipigon Brookies, Sonar Versus Catfish, Turnover Truth

Management in Action: Nipigon Brook Trout Comeback

Three decades ago, the speckled (brook) trout population in Ontario’s Nipigon River was in big trouble. The culprits included water-level drawdowns to generate hydroelectricity and angler overfishing. This historic waterway where Dan Galen created the muddler minnow in 1936 and Dr. J. W. Cook caught his massive 14 1/2-pound world record trout in 1915 was on its death bed.

Strict agreements were instituted to control the river’s water flow, but how to convince anglers to release the last few big female trout on which the river depended was the issue. It’s a biological principle known as “storage effect” in which mature females maximize their energy reserves, survive tough environmental conditions, and then lay large numbers of high-quality eggs, when conditions finally improve.  

“It’s hard to believe, but at the time, many people didn’t believe you could catch and successfully release a brook trout,” says retired Ontario Ministry of Natural Resources biologist Rob Swainson. “You can’t let these fish go; they’re too fragile. That’s what they believed.” So Swainson put fish-tagging guns in the hands of local anglers, with tags that carried unique tracking numbers and a simple message: Please Release Me.

“It was endless, the information we got,” he says. “Anglers could see how often fish were being caught, how small the population really was, and how far the trout moved. We tagged 16 brook trout on a spawning bed in South Bay, in Lake Nipigon, and six of those fish were caught and killed the next year. We tagged 14 the following season and five were caught and killed. It was mind-blowing that you could put 30 tagged fish in the largest inland lake in Ontario—the 32nd biggest lake in the world—and have 11 trout (likely more because of non-reporting) caught and killed.”

But it was the angler-driven catch-and-release tagging program that shocked everyone. It showed that between 15 and 35 percent of the brook trout were caught at least twice, by the same anglers who had originally tagged them. Between two of the hydro dams on the river, 10 percent of the tagged fish were caught three times by the same anglers who had tagged them.  

“On the lower Nipigon River, just under 50 percent of the fish in the river had been caught and released at least twice,” Swainson says. “Even on Lake Superior, the largest freshwater lake in the world, 15 percent of the brook trout were caught and released at least twice.”

Special regulations were subsequently put in place, including a one-trout limit over 22 inches and the fish showed once again, that given quality waters in which to live and adequate protection, they can sustain world-class fishing. Still, Swainson  worries that with today’s intelligent fishing pressure, if the regulations are ever relaxed “the fishery will quickly collapse.” A warning and ringing endorsement for wise management.

–Gord Pyzer

From the Field: Live Sonar and Blue Catfish

The increasing use of live-imaging sonar (a.k.a forward-facing sonar) has raised questions among anglers and fishery management agencies about whether the technology significantly improves catch rates and ultimately affects fish populations. Depending on the species and fishery, effects could be increased catch rates and harvest, and/or reduced catchability because of more frequent fish encounters and fish conditioning, which may lead to higher catch avoidance. Research on this subject is needed to establish scientific evidence to help guide management.

Researchers with the Kansas Department of Wildlife and Parks and Kansas State University investigated the effects of live-imaging sonar on blue catfish angler success.* Tests were performed at 16,000-acre Milford Reservoir, Kansas. Researchers also examined how live sonar affects perception and behavior of blue catfish anglers.

Tests consisted of using 16 two-person angling teams. On each team, one angler was familiar with blue catfish angling and the use of live-imaging sonar, while the second angler was randomly selected from a pool of anglers with varying levels of catfish angling skills and live-sonar experience. Teams were assigned to one of four fishing rounds, with four teams participating in each round. Two of the teams were allowed the use of live sonar, while the other two teams were not. Trials lasted 5 hours, and started either at sunrise or five hours before sunset. Anglers fished with cut carp and river carpsucker on suspended or bottom presentations.

During the study, anglers fished for 440 angler-hours and caught 373 blue catfish from a quarter pound up to about 40 pounds (average about 5 pounds). The average total weight caught during 5-hour angling trials was about 32 pounds. Results showed no difference in total weight of catfish caught per 5-hour angling period between anglers using live sonar and those that were not.

After the fishing portion of the study was completed, the anglers filled out a survey regarding their experience level, skill, perceptions of live sonar, and angler behavior during the experiments. Self-assessment of angling skill was positively related to fishing success but not strongly correlated. Behavior-wise, anglers using live sonar spent more time searching than did anglers not using live sonar. The survey indicated that for anglers using live sonar, their time spent searching and catch would have been similar if they didn’t use live sonar. Anglers that didn’t use live-sonar thought they would spend more time searching, and catch may have increased if using live sonar.

The researchers report that the angling teams, with varying backgrounds, were equally successful catching blue cats at Milford Lake, regardless of live-sonar use, and suggested that live-sonar may not increase harvest rates at Milford or similar fisheries. They concluded that the use of live sonar may influence blue catfish angler perception and behavior more than catch. As the use of live sonar becomes more prevalent and anglers become more skilled at using the technology, more research will be necessary to understand its biological effects on fisheries, to help guide fishery management. The authors also suggest that regardless of biological impacts, managers should consider social consequences of ever-changing angling behavior.

–In-Fisherman

*Neely, B. C., J. D. Koch, and K. B. Guido. 2003 Effects of live-imaging sonar on blue catfish angler success, perception, and behavior. N. Am. J. Fish. Mgmt. 43:1765-1771.

The Environment: The Truth About Turnover

The fall season ushers in profound changes in the aquatic world, especially in northern latitudes. Alteration of the status quo can throw anglers off the bite, and many find fall fishing unusually challenging as fish locations shift. One of the common excuses for a poor catch is that a lake has turned over. It’s a common refrain of fall anglers from early September to well into October. This phrase pertains to the limnological processes that occur as water temperature declines.

For turnover to occur, a lake or reservoir must have been stratified in summer, with three layers of water segregated by their temperature, which determines their density. Warm water is least dense, so it floats on cooler water below. In summer, the top layer is warm, gradually cooling from the surface to a depth range that can vary from 8 or 10 feet in shallow productive lakes and ponds to more than 30 feet in deep oligotrophic systems. Below the warm surface layer is a relatively narrow band of water that abruptly drops from the low 70s at its upper edge to around 50°F, the thermocline.

Below lies the coldest water in the lake, the hypolimnion. In more fertile waters, this layer typically lacks sufficient oxygen for fish during summer stratification, limiting their distribution. As surface water cools, it becomes denser and starts to sink and mix with water in the thermocline below. Wind encourages this mixing and eventually the thermocline thins, then disappears. As the chilled water sinks to the bottom, debris and bubbles may rise to the surface, sometimes accompanied by a gassy smell and leaf fragments. Fishing can indeed become more difficult in this flux, but it’s short-lived, often just a week or so in a particular system. Each lake is different in its features, so turnover times vary. Many large, wind-blown or shallower lakes don’t stratify, and reservoirs with substantial flow also aren’t affected.

–Steve Quinn

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