The Dollars and Sense of Growing and Harvesting Minnows in Your Lake or Pond
If you work with nutrient impaired water, you could do a few things and turn your smelly, green, algae-filled pond into a clear, nutrient cycling, minnow producer. By growing and harvesting minnows, you’re being a water steward. The minnows would thank you, and then you would thank the minnows!
Before You Can Harvest Minnows: Integrate Surface Area and Circulation
To maximize for cycling of nutrients that otherwise result in polluted water, integrate surface area and circulation into your waterway. The surface area can, and should, take many forms. Here’s some examples…cobble, gravel, sand, three dimensional structure underwater and at the water’s surface, like deadheads and boulders, perennial native aquatic vegetation, seasoned brush, floating islands. Circulation also comes in several forms. Think about and take advantage of gravity flow, wind and fetch, vertical and horizontal aeration, floating stream beds. Surface area and circulation are primary steps. Your water must have these two factors in abundance.
Stay Low in the Circle of Life to Maximize Minnows
The surface area and circulation you have designed for will grow biofilm, food for minnows and invertebrates. This is a primary way to avoid monoculture of algae. Native minnows are usually best. I don’t know of any that do not feed on biofilm in its periphyton form. Likewise, the incredibly diverse repertoire of invertebrates that inevitably colonize periphyton add to the health of your water. Nature lends a hand at these levels of life. They also serve to maximize the growth, volume, and health of your minnows.
Biofilm itself is stratified, and will include layers of aerobic, anoxic and anaerobic microbes. So the water in your waterway should not be anoxic or anaerobic. It should not disallow for the primary aerobic life forms, like fish. The nitrogen cycle is complete within the biofilm.
Recognize the Importance of Biomass Transfer
Every time your nutrients are eaten, only one tenth moves forward. Think of your dog: It eats ten pounds of kibbles, and only one pound becomes dog. The rest becomes manure, biogas and ultimately, other life forms. In practical terms, this means you can grow many more pounds of minnows from the same water that would only produce a couple pounds of big, game fish. I know it is hard to exclude game fish from your waterway, but dedicate at least one water setting to minnows exclusively in order to maximize production. And your job, as water steward, is to insure that inflow nutrients are cycling through your water. In other words, harvest. If your nutrients are not cycling out of your waterway at the same rate or a higher rate than they cycle in, your water will die.
Reap in the Benefits of a Bountiful Minnow Population
The key to this strategy are these two primary factors—surface area and circulation. Nature is insidious, it can not be stopped, and when given these two factors biodiversity is all but insured, short of some form of extreme environmental insult.
The minnows are a terrific resource. They are valuable and can be marketed. They can be an excellent form of biological control of mosquito and midge larvae.
A productive water body grows, somewhere over 1,000 pounds of minnows per acre foot of water. The minnows are a terrific resource. They are valuable and can be marketed. They can be an excellent form of biological control of mosquito and midge larvae. Now you can improve quality of life on a landscape basis, without carcinogenic chemicals. You can limit disease vector insects, and correspondingly reduce risk of diseases like West Nile, Blue Tongue, in this region, and dengue fever, malaria, yellow fever and Zika virus elsewhere.
Today at Shepherd we market high volumes of minnows commercially. We disperse others to minimize mosquito and midge. The rest are introduced into Fish Fry Lake. Minnows have a wealth of habitat in Fish Fry, but there are also a wealth of game fish present. Today, Minnow Pond produces 1080 pounds of minnows on an acre/foot basis, while Fish Fry Lake produces between 26-28 pounds of game fish per acre foot of water. While the numbers are strikingly different, Fish Fry Lake is the most productive wild fishery in Montana that we know of. In fact, given waterways of over 50 acre feet, we know of no others that exceed ten pounds of fish per acre foot.
So the benefits are experienced all around: in our pocketbook, our quality of life during mosquito season, our sport fishery, and finally, our water quality.
A Sound Investment
Here’s how it shakes out in terms of return on investment:
A. Costs of floating streambed in Minnow Pond: $5,600. Operating costs, and related time/travel: $645. Minnow sales in year one: 2,255 dozen at $3.50/dozen….$7,892.
B. Mosquito reduction is difficult to quantify, but today, unlike the past, we can function in the evening in June without layers of chemical spray. We’ve had no known incidence of West Nile disease or Blue Tongue mortality in the last three years, compared to as many as 19 whitetail mortality per season via Blue Tongue in the past, from this 340 acre property. We see minnow over-winter survival in at least eight of nineteen perennial and ephemeral water features across the property.
C. Nitrogen levels in outflow water are down to non detect, where in the past they could be dangerously high. Phosphorus levels average .02 parts per million.
Over at Fish Fry Lake, a separate water body from our Minnow Pond, the catch rate of game fish on Fish Fry Lake is less than two minutes to catch one fish when fishing from shore. Boat fishing is typically even faster. Some aquatic vegetation harvest is still required on Fish Fry, but has reduced by ten fold compared to five years ago. Today, about 25 pounds of phosphorus is harvested, primarily in the form of fish from Fish Fry, against 11 to 14 pounds coming in. The lake is in transition, and is reducing inventory of phosphorus built up since the inception of agricultural fertilizer. Dissolved oxygen levels are consistently mid range stable, 5 mil/liter to saturated.
A largemouth bass population has developed in Fish Fry Lake. This is likely to reduce our harvest of yellow perch, black crappie, bluegill and red ear sunfish. However, corresponding size of pan fish should increase, although that has been our trend in any case, with perch up to two pounds. We see this as a natural progression for Fish Fry, and plan to enjoy the process! However, keeping game fish out of Minnow Pond is fundamental to our strategy.