Mar 10, 2014

Return of Bigger Northern Brook Trout

By: Bob Obma

At a recent Oconto Trout Unlimited meeting, better fishing came up for discussion (again.) We have many small fish, but big brook trout are scarce. In an honest moment, someone admitted that a twelve-inch brookie is rare, and probably the best catch of the year.

We fish hard and are blessed with 112 trout streams in the county. Most of these streams have enough natural reproduction to make stocking unnecessary. Why only smaller fish?

There were once many bigger fish here. Historic records include Shattuck’s 1892 fishing trip to the north branch of the Oconto River, yielding over 400 brook trout ranging from a quarter to two and a half pounds. The anglers mentioned that they were staying at a lumber camp, so the “cutover” was going on. Timber was clear cut, tops left to fuel future forest fires, and logs floated downstream to saw mills. The river was too shallow to float logs, so “flush dams” were built to create floods as needed. Boulders were dynamited and brush cut to clear the way. Thousands of logs went downriver in these log drives, battering fishable stream banks out of existence. The Oconto, like other logged rivers, became wide, shallow and devoid of cover or habitat for older fish.

The logged landscape was called a “slashing;” old photos look bleak and bare. Pine and hardwoods were followed by pioneer species, sedge meadows with speckled alder on wetlands, and aspen on the highlands. The alder thicket inhibits growth of grasses on the banks, leading to further bank erosion. Beaver thrive on a poplar diet (beaver candy) to build dams that heat up the water. Coldwater trout are replaced by chubs in the warm-water ponds.

Imported brown trout were stocked in the warmer rivers before it became apparent that they crowd out larger brook trout for choice feeding lies. Trophy brook trout retreated to northern headwaters. Since these upstream cold refuges have little habitat for older fish, the population became skewed toward small native trout.    

Today when you fish a stretch of our north branch, it is still wide and shallow with few midstream rocks and a lot of flat sandy bottom. Your eye sees the truth: few fish will be there, and none of interesting size. The fish agree with you; older fish are scarce here. Still, trout survived there; young-of-the-year trout can survive to spawn in degraded habitat, and some of them spawn at five inches. This left anglers with a sizable remnant population of young-of-the-year fish. The rare sixteen-inch fish is now taken every five years from the Oconto, where they were once common.

The fishery biologists are well aware that the population became skewed toward young-of-the-year fish, so many remedies have been tried over the years. Anglers initially wondered whether spawning was inadequate, so hatchery fish were stocked. That didn’t work because hatchery fish rarely last long enough to spawn and grow to a desirable size. Perhaps fishermen were too successful. Daily bag limits were set, but few big fish were caught. The stream was fully occupied by enough small fish to consume all of the available food, but they don’t live long enough to grow. How to allow more fish to grow for two or three years has been debated for a hundred years.

Since hatchery fish and bag limits didn’t work, the changes in the river from the log drives were questioned. Did they wipe out the habitat needed by older fish? Were all the choice feeding lies filled up with big aggressive brown trout? You have learned where the few remaining brook trout are through your own experience, talking with other anglers and the fish shocking crews.

Older brook trout favor deeper water, just over the top of your hip boots. Prime feeding lies have abundant food from the fertile rocky bottoms, with current breaks to protect from oncoming current. Autumn spawning riffles, prime summer feeding lies and winter shelter areas can be miles apart. Streams fragmented by dams, beavers or perched culverts have few older fish. Competing exotic brown trout hog the best feeding lies and crowd out bigger brookies. The trophy native trout are found in cold brook-trout-only water that is more common in the North where they evolved.

When the limited results of stocking and bag limits became apparent, efforts to restore the pre-log-drive habitat were begun; streams are narrowed, which makes them run faster to dig out the sediment and restore productive stone bottoms for food organisms. Current breaks from replaced midstream boulders, logs and root wads hold older fish in the deeper pools. These techniques have been refined over the years, but a fishery with both numbers and older, bigger brookies remained elusive until the last several years.

Across Northern Wisconsin, from Dunn County to Langlade County, areas that held only 4”-6” trout are now showing more 8”-12” fish in rehabilitated areas. Natural or created large woody habitat hold better fish on the stream surveys. Control of beaver and alder overgrowth remains necessary. Once brown trout are present, shocking and transplanting them to more welcoming areas has not worked. Recall that they are both edible and delicious, but they spawn faster than one catches them.

There are several ways you can get in on the fun. Since the stream rehab is a lot of work, the areas are done in segments of longer streams. Make friends with someone who has worked on these projects and is familiar with the structures. These are not the familiar lunker structures of Timber Coulee, so help put one in to understand what is underwater; it saves a large quantity of nymphs. Fish holding in large woody habitat are notoriously hard to draw out. One of my favorite stream rebuilders told me that big brookies are notoriously hard to get out of the root wads. I said her job description was to get fish in there whereas mine is to get them out!

These streams don’t have many dense hatches, so fish feed opportunistically. If it looks buggy, it’s edible, and the last fish to bite goes hungry. That said, these fish are not pushovers.

Gastric lavage on these fish shows scuds, terrestrials and some caddis, which is about what shows up on in stream samples. Parachute Adams # 12, crickets appropriate for the season and carpenter ants float high enough to be practical. When that doesn’t work, red squirrel nymphs and # 12 soft hackle wooly warms floated, perhaps with a Liesenring lift, just before they become as one with a root, can tease out these fish.

Have fun. These are lovely places.

Bob Obma