Let’s focus on forage, on how best to manage water so that it is spectacularly productive. One of the best outcomes of good management is that your water ends up being clear and healthy too. Safe for the kids to play in.
Here’s a few of the systems we’ve gone with at our place. There’s never enough space or time for all the details, but I bet there’s enough here to help you come up with your own variations.
In a 5,400 square foot pond just above Fish Fry Lake, our research lake, we use a floating streambed. The system is similar to that described in Wes Neal’s recent article and circulates aerated water through aged, deciduous brush. It is a practiced variation of Brush Park polyculture. In the process we grow and harvest on average 400 pounds of fathead minnow, five prong stickleback cyprinids, and crawfish annually. The nonpoint nutrients present in inflow water is the only feed associated with this system.
We typically use three cloverleaf minnow traps for the harvest. Setting and checking of traps occur daily in May, September and October. Fatheads make up 250 pounds of the total, stickleback about 90, and crawfish about 60 pounds. We are going into our fourth year of hitting this level of harvest.
Beds of aquatic vegetation, rock, cobble, deadheads and other structures are passive but highly effective forms of surface area. Especially when combined with circulation, growth of periphyton is amplified. Nutrients contained within periphyton will cycle through a waterway’s food web at least four times faster within the aerobic zone than within anoxic or anaerobic zones, which argues for added aeration/circulation, especially in nutrient rich water like Fish Fry Lake.
Enhancing for Fatheads and Yellow Perch Forage
Certain fish represent a primary forage base. In the northern half of the U.S., yellow perch and fathead minnows exemplify this. The northern yellow perch are also considered a hyper-accumulator relative to phosphorus. Compared to the fathead minnow, of which 205 pounds are required to be harvested to remove one pound of phosphorus from the water, only 105 pounds of yellow perch is needed. However, fatheads are a trophic level below perch however, so the net impact associated with nutrient cycling probably favors the fathead.
Enhancing for spawning habitat, security habitat, aeration/circulation, and forage for perch and fatheads, represents another in-waterbody management tactic. Deciduous brush is stacked underwater as perch spawning habitat structure. Water depth is 9-15 feet at these points. The brush provides spawning structure in an aerated setting with moderate circulation. We are also considering zoning off specific inlets as we attempt to provide fatheads with secure spawning habitat. We incorporate underside surface area for fathead spawning structure too.
Enhancing for Other Biota
A plant-like form of phytoplankton, Chara, naturally occurs in Fish Fry Lake and is used heavily by perch, probably as security habitat. We occasionally harvest other forms of aquatic vegetation to bias in favor of Chara.
Fish Harvest…A Primary Strategy
In combination, these actions contribute to maintenance of a healthy yellow perch forage base in the lake. At Fish Fry, we employ a slot limit harvest program, with a focus on non-harvest of large female perch. These female perch can generate as many as 65,000 eggs each, when compared to one-tenth that number associated with two- or three-year-old fish. Most of the fatheads, stickleback and crawfish from Minnow Pond also go into Fish Fry, but the fatheads are such a vulnerable prey, so easy to catch, we aren’t certain they sustain and breed in the lake…yet. We do know the crawfish sustain and now contribute nicely to the lake’s forage base.
The bluegill is an extremely effective fish in northern waters. There are a range of theories about why this fish can quickly overpopulate a waterway, and the theories are currently evolving. What we have learned on Fish Fry is that bluegill represent an effective opportunity to cycle phosphorus out of the lake, while providing a valuable resource, and while concurrently improving the lake’s sport fishery characteristics.
In one season we harvested nearly 9,000 bluegill on a slot limit basis. We kept all fish caught up to five inches in length. We returned the larger ones to the lake and gutted and air dried the rest. This harvest has provided over four years of canine treats for our resident Labrador retrievers. Note that when air dried, fish bones become extremely brittle and therefore safe for consumption. There have been no negative issues with these fish as canine food. In fact, five years later, we still have fish from that original harvest which our canines consume regularly!
The slot-limit bluegill harvest strategy has been continued on Fish Fry Lake, but now the small bluegill are processed into cut bait and cycled back into the waterway. Small bluegill as a forage component is particularly popular in the southern half of the U.S. On Fish Fry Lake, small bluegill up to five inches in length are caught and cycled into cut bait, then fed into black crappie, red ear sunfish and yellow perch. This experiment appears to be working and could be expanded. Currently, an average of 25 of these small bluegill are processed into cut bait per day during the warmest six months of the year, from a single test location on the lake. Fish were conditioned to accept cut bait by blending it with fathead minnows, a preferred forage.
A similar strategy has been employed to enhance growth of largemouth bass in other settings and could possibly be applied on Fish Fry. Since our focus is more associated with yellow perch, due to its unique phosphorus-cycling characteristic, we are likely to stay focused on them. It’s noteworthy, however, that only a handful of fish species have been tested for phosphorus accumulation, and there could be other meritorious species to consider.
Today there are perch and crappie of trophy dimensions in Fish Fry. While some of these large fish are caught and consumed by us, most of the big ones are effective spawners and are left for fun on a fishing pole. The fathead in particular represent a primary forage base for perch, crappie, largemouth bass and channel catfish.
Today we are considering introducing other game fish, like rainbow trout, tiger musky, and smallmouth bass. But as is, current growth rates of our fish are excellent, as is quality of the fishery. While there are limited data tracking “quality” of fishery, we gauge our quality based on fish catch rate and range of age class of fish that are caught. Today’s catch rate on Fish Fry is one fish every two minutes. Between ten and 15% of fish caught are five years old, or older. Ten inch bluegill, perch pushing 15”s, and black crappie in the 17” range, and colorful, healthy, fish at the top of their game make for serious good fun!
Note that the bluegill could not function in this role except for our stewardship, our intervention. Without our hook and line harvest and processing of bluegill into cut bait, to the tune of an average of 5,200 per year now, they would not be cycling into black crappie, sunfish and perch. A fraction of young-of-year bluegill become food for the bass, catfish, perch and crappie in the lake, but the bluegill population is only vulnerable for a relatively short time…when the young-of-year bluegill are small enough to fit within the maw of these larger game fish. But once the bluegill achieves a size of three or four inches in length, only the channel catfish have large enough maws to consume them, with the possible exception of large northern bass…in the four pound or larger range. But with our intervention today we have very large perch, and their progeny represents a much more available forage for a far longer time frame, as young perch are harvestable by most of the game fish, and large perch themselves, for up to three or possibly four years. The relatively long, narrow shape of perch allows for this.
Crawfish also exemplify this. In early winter dense bottom water is still charged with dissolved oxygen, typically in the 7-9 mg/L range. At that point, numerous crawfish exist at depth. As winter progresses, dissolved oxygen levels shift downward, forcing the crawfish into shallower settings. The deeper was is actually warmer, at 39 degrees F, and thus preferential to the crawfish. However, the low dissolved oxygen levels trump temperature and force the crawfish upwards, into the colder 33 degree F water, in order to breathe.
Maintaining suitable DO levels top to bottom could resolve this and would also likely result in temperature homogenization. This is a stewardship strategy worthy of future research, but is particularly challenging in a highly variable depth-profile setting like Fish Fry Lake.
Crawfish are like bullfrog tadpoles in that they are a primary consumer of periphyton. Other advantages are that crawfish are versatile consumers and will also eat dead organic matter like fish. They are palatable to many game fish, including perch, black crappie, largemouth bass and channel catfish. Another benefit is that humans often consider fish that eat crawfish to be really tasty.
The system pictured below provides crawfish with periphyton, and essentially a ladder allowing them to readily access both, a preferred dissolved oxygen level and potentially, a preferred temperature zone. The matrix contained within the net tube provides concentrated surface area upon which biofilm develops, which in turn is the base for periphyton which crawfish eat. It also provides countless apertures within which the crawfish achieve both security and passage. The plant roots are another crawfish food in and of themselves. We are exploring just what plant roots work best for crawfish.
Upon pulling such a unit onto a tarp on shore after it has been in position for several days, we have seen many multiple age-class crawfish exiting the matrix as they return to the lake.
Enhancing for crawfish may have some drawbacks, including a possible reduction in water clarity associated with silt disturbance on the bottom of a waterway. We are currently tracking the pros and cons associated with crawfish as a primary forage base.