September 30, 2010
A study was conducted recently on smallmouth bass in the Mississippi River. The information gained may surprise you.
By Tim Lesmeister
I was excited. Lifting the 14-incher for my client to see, I proclaimed, "It's Homer again."
Though I don't usually name the smallmouth bass I catch, this one was special. This was the third time my guiding clients had caught this same fish from the same spot. I knew it was the same fish because of the foot-long wire antenna protruding from the smallie's belly. Implanted with a tiny radio transmitter, the fish was part of a major Department of Natural Resources study of Mississippi River smallmouths. In fact, the one I had nicknamed "Homer" was just one of 30 smallies carefully tracked by biologists for over a year. The surprising information gained from studying these fish should be of interest to every smallmouth bass fan.
WHY TRACK SMALLIES?
The 15-month-long study, which concluded last year, was conducted on the Upper Mississippi between the St. Cloud and the Coon Rapids dams. This 60-mile portion of the Mississippi is Minnesota's best smallmouth river and increasingly a popular destination for anglers. And because the Upper Miss is such an important smallmouth fishery, the DNR has been very interested in the river for over a decade. Years ago, the agency placed a 12- to 20-inch protected slot regulation on 47 miles of the Upper Miss, but biologists have wondered how many smallmouths swim out of the protected zone and become vulnerable to harvest.
Previously, some smallmouths were fin-tagged in an attempt to study their movements. However, river smallies often scrape or tear their tags off, so external tagging didn't allow biologists to gather much information. Another reason state fisheries personnel decided to use internal transmitters was to track the fish on a constant basis. Being able to monitor smallmouths year-round would offer valuable insights into their seasonal and even daily movements.
Photo by Ron Sinfelt
For this ambitious research project, 30 smallmouths ranging from 12 to 20 inches were captured, anesthetized and surgically implanted with miniature transmitters. Then the real work began. The DNR biologist in charge of the day-to-day efforts was Eric Altena. Young and enthusiastic, Altena spent hundreds of hours in a boat covering miles of river, recording the movements of the 30 fish.
One of the more surprising things he discovered was how variable the smallmouth's movements are on the Upper Mississippi. In some other northern rivers, research has indicated that in the fall all the smallmouths travel long distances downstream to deep-water wintering pools, then in the spring these fish head back upstream - sometimes over 40 miles - to their spawning habitat.
In contrast, on the mighty Mississippi it was found that movement is quite variable among different fish. All the tracked fish made seasonal movements, but for some it was only a few miles a year. In fact, one of the biggest homebodies was fish No. 611, the one I called "Homer," as in couch potato Homer Simpson. Not only did this 14-incher stay in one small area of the river all summer long, but even during the fall Homer moved barely a mile. On the other hand, the most nomadic fish in the study swam an impressive 30 miles annually.
Another surprising trait of the Mississippi smallies is the time they actually start their fall movements. Other river studies have indicated that fall movements are triggered by a specific temperature, so most smallmouths move at the same time. In contrast, some Mississippi River fish in this study started moving to their wintering areas as early as September, when the water was 60 degrees, while others didn't relocate until well into November, when water temperature had dropped to 52 degrees. This is a nearly two-month difference.
Ultimately, however, every tracked fish relocated to a slow-current area of the river. They remained in these slackwater "hibernaculas" the entire winter, moving very little. This behavior is similar to smallmouths in other northern rivers. The reason river smallies seek out slackwater areas for the winter months is to conserve energy. With water temperature barely above freezing, the fish's metabolism is extremely low and they eat very little. To survive over the winter they must avoid current and burn as few calories as possible - a form of semi-hibernation.
Another interesting aspect of the study was seeing how powerful the reproductive urge was in the spring. In the fall, the fish often moved only a few hundred yards daily, but in early April, once temperatures exceeded 50 degrees, many of these same individuals swam over a mile a day to reach their spawning areas. These sites were usually gravel-bottomed eddies along the riverbank or the slow water behind an island.
Though the study monitored fish only over one spring, biologist Altena believes that many, if not all, of the tracked smallmouths were spawning in the same places they had in previous years. Each fish traveled directly to a single site rather than randomly moving from place to place over a period of time. This is a strong indication that each individual Mississippi River smallmouth remembers its spawning site and uses that site year after year. This is similar to the behavior of the spawning smallmouths that have been studied in other states and provinces.
Females and males behave quite differently in the spring. Female smallies only stayed a week or so at their spawning sites before leaving for their summer range. Males, on the other hand, remained in the same bank eddy for several weeks guarding their offspring. Then after their parenting chores were completed, the males also moved to areas where they would feed throughout the summer. However, these post-spawn movements ranged from just a few hundred yards to a few miles, much shorter than spring and fall journeys.
And while the smallmouths' summer ranges were often only a short stretch of river, some tracked individuals occasionally ventured into odd areas. During high flows of midsummer, Altena tracked one fish into a flooded pasture and another all the way to a golf course pond temporarily connected to the Mississippi. He hypothesizes that these fish were looking for minnows or perhaps trying to escape the strong currents present at that time. Both of these individuals returned to the main channel as river levels dropped.
Some good news for anglers is the fact that few of the 30 studied specimens ever moved out of the catch-and-release zone into the unprotected portion of the river. This stands in contrast to the situation on southern Minnesota's Zumbro River. In the 1980s, two miles of the Zumbro received catch-and-re
lease protection, but studies found that many smallmouths regularly left this short section and were susceptible to harvest. Fortunately, the Mississippi's 47 miles of special regulations water is a long enough section to ensure that the great majority of its smallmouths stay in the protected zone.
Interestingly, the tagged fish were regularly caught by anglers during the study. While on the river, Altena got 15 different reports of the monitored fish being caught, including the one my clients caught three times and another eager biter that was released four times. It's also quite likely other tracked fish were caught and released but not reported to the DNR.
As a testimonial to anglers' good compliance with the Mississippi's catch-and-release regulations, none of the 30 fish were poached, even though some were over 18 inches long. However, five of the implanted smallies died during the study period. Three were lost during the winter, with blood on shoreline ice suggesting natural predators, perhaps otters, as the cause. Two others died of unknown causes during the summer, with the transmitters continuing to give off stationary signals from the river bottom. These two may have died from being hooked. Deep hooking from live-bait use is still a worrisome cause of smallmouth mortality.
In clear waters, many anglers assume smallies are shallow during morning and evenings, and move deeper during the bright light of midday. On the Mississippi, Altena didn't find this scenario. While many individual fish made daily movements, there was no common pattern. One individual may have been located along a bank in the morning, then during the midday moved to a midriver run 75 yards away. At the same time, another individual might have moved in the opposite direction, from midriver to the bank. I believe that the river's size and clarity is why Mississippi bronzebacks don't follow common movement patterns. Because it's a relatively deep and low-visibility river, smallmouths feel secure in most areas.
At the end of the study, as many tagged fish as possible were recaptured and measured. Annual growth ranged from as little as 1/4 inch to slightly over 1 inch per year, with an average growth of just 3/4 inches. This confirms other DNR studies showing that once they're adults, Mississippi River smallmouths grow extremely slowly but can live long. On average, it takes the fish six years to reach 13 inches and almost 10 years to make 16 inches. Those highly prized 20- to 21-inchers are positively ancient, as in 14 years old! This also highlights just how easily a smallmouth fishery can be ruined by catch-and-keep angling. Because smallmouths are so slow-growing, if there is significant harvest of midsized fish (12- to 15-inchers), very few will ever reach the larger sizes.
The positive side to smallies' slow growth is how much sport a single smallmouth can provide. Because a foot-long specimen can live eight more years, if it's caught and released even only twice a season, this single fish can provide angling enjoyment 16 different times! And of course this same fish will also be able to spawn at least eight different times over its lifespan.
A number of important pieces to the smallmouth lifecycle puzzle were gathered during the study. The piece that surprised Altena the most was how shallow the fish remain during winter. Many biologists had believed that winter smallmouths invariably locate in the deepest water they can find. However, many Mississippi River fish remained shallow in just 3 to 4 feet of water all winter. It may also surprise some to learn that the rock-loving smallies often choose wintering sites with soft bottoms, sand or silt, rather than rocky substrates. So while fish always seek out slow-flow areas, depth and bottom composition aren't key concerns in winter.
Perhaps the larger lesson to be drawn from this shallow-water wintering is that there are significant differences between different smallmouth populations. It's clear that river smallmouths are highly variable in their habits, and strongly influenced by river size, type and geographical location.
BIGGER SMALLMOUTHS, BETTER SPAWNING
Because the Upper Mississippi has been regularly surveyed since 1990 when the slot limit was enacted, the DNR has a good record of the river's smallmouth populations. Not only is the average size of the fish better today than it was 15 years ago, but the overall number of smallies is also higher.
Fisheries personnel annually "shock" - electrofish - the river in 10 different locations between St. Cloud and Anoka. In recent years, total smallmouth numbers from all these locations have exceeded 600, significantly more fish than what many of the previous surveys recorded. Electrofishing results are measured by numbers of fish captured in an hour. Of the 10 different stretches of river surveyed, only the area around the Highway 24 bridge near Clearwater had low numbers of smallmouths. This survey recorded less than 20 fish per hour, undoubtedly because this is one of the few shallow, sandy areas of the Upper Miss. In most other survey locations, over 40 fish per hour were counted, and in a couple hotspots a whopping 100 smallies an hour were stunned and recorded.
Altena and other biologists believe this increased number of smallmouths is one of the benefits of the river's special regulations. Not only have protective regulations resulted in more big fish - 16- to 18-inchers - in the river, but reproductive success has improved, too. Bigger smallmouths actually reproduce better, because the larger smallmouths seem able to spawn more successfully in difficult conditions than 12-inchers can. Despite heavy flows causing poor spawning conditions through much of the 1990s, actual reproductive success was still quite good during this period. In the past, when the average size of the adult fish was smaller, there was very little successful reproduction during many years. So there were many missing year-classes in the smallmouth population. Today with more 16- and 17-inchers spawning, there is greater stability in the population because some young are produced almost every year.
There are several possible reasons why larger fish are better spawners. It may be because they produce more eggs. Or it might be that larger - older and more experienced - fish choose better nest sites. It could be that they are more effective nest-guarders. Or it may be a combination of reasons. The result clearly seems to be a healthier and more robust smallmouth fishery.
With all the data collected, nobody can deny that better regulations bring better fishing. When the Mississippi's protected slot limit was implemented in 1990, a handful of folks scoffed at it. They said new angling regulations wouldn't improve the fishing. One of my fellow fishing writers even said the regs would be so confusing that compliance would be poor and people would quit fishing the river. Boy, was he wrong. Not only are there more big fish and more total fish now, compliance with the regs is very good and angler satisfaction is high.
In all the many hours biologist Altena spent on the river he saw and spoke with many anglers, and
none expressed dislike of the protective regulations. Rather, some anglers voiced their desire to see the regs extended down to the Coon Rapids dam. And it's not just a few people taking advantage of this quality fishery. I've fished this section of the Mississippi for 27 years, and since the protective rules have been in place I've observed a steady increase in those seeking smallmouths. Knowing that the Miss offers excellent chances for lunkers, smallmouth fans are even coming from distant locales like Virginia and California to savor the fishing. And of course, being so close to the Twin Cities' 2.5 million people means nearby anglers are also flocking to the Upper Miss. In fact, during a recent fall day I counted 21 anglers in just two miles of river. To head off this type of crowding, it may be wise to start creating other "blue-ribbon" catch-and-release smallmouth waters to spread anglers around. The Taylors Falls to Stillwater section of the St. Croix River seems like an excellent candidate.
While the present status of the Upper Mississippi's smallmouths is good, I'd be remiss in not concluding with a cautionary note. DNR personnel are very concerned with the land use along the river. Because explosive sprawl is taking place in the St. Cloud to Minneapolis corridor, the river is being affected. Erosion and declining water quality will negatively impact the river's smallmouth fishery. In fact, this past summer the river suffered from enormous bank erosion in the Monticello/Elk River area during a period of heavy rain. Some of the worst erosion was where homeowners had previously removed the riverbank's protective tree-root systems. To protect the river's world-class smallmouth fisheries, better land-use practices and ordinances seem in order.
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