Fish Fry Lake: Origin of Bounty and the Value of the Harvest

image of the original article about the value of harvesting fish from a wild pond to improve pond conditions

This post on the value of the harvest originally appeared as an article in the Jan-Feb issue of PondBoss Magazine in a slightly different form as, “Harvesting—Bounty Beyond the Shoreline”

Pondmeisters love fish. We want clean, healthy water, but fish are a main target—particularly big, sporty fish and all the fun that comes with them. But, here’s a “what if…” What if we could have crystal clear water you could drink out of hand, and nice fish with nearly every cast? What if we could have both? Wouldn’t that be just AWESOME?!

2005:

What had been a seasonal pond is dug out. The pond receives about 60-80 gallons per minute of ground water. It doesn’t leak! So 6.5 acre Fish Fry Lake is born. Tons of pit run gravel is screened, and ninety percent of the pond’s bottom is lined with cobble or gravel. Average harvest of nearly 300 pounds of bullfrogs from Fish Fry Lake translates to another 1.5 pounds of phosphorus coming out of the lake annually. Over the next couple years the pond is filled and flushed three times. Residue fertilizer, think phosphorus, had accumulated in the draw that became the pond, and more comes in intermittently with ground water. So, water quality is bad—shore to shore carpet of algae and cyanobacteria. In between the blooms the water is turbid. (Fourteen inches on a Secchi disk.)

2016:

Fish Fry Lake is keeping up with inflow nutrients. The catch rate on fish is off the charts.  Water clarity is good—sometimes as much as twenty feet. Dissolved oxygen (DO) levels allow for fish to live, eat, and grow top to bottom in 95% of the lake. And, for the scientists out there, note that even though dissolved oxygen levels in the lake typically are above 5 mil/liter, biofilm present on the massive surface area provided by floating islands, which are made of a filter-like matrix, includes an aerobic (outer), anoxic (middle) and anaerobic (bottom) layer. This means the complete nitrogen cycle, which requires some anoxic and anaerobic conditions, happens in the floating islands. This also means we do not lose most of the bottom of the lake to anaerobic conditions that fish can’t live in.

I’m sitting here on the computer. It’s 4 a.m., and it’s raining outside. Blessed rain! It’s October, and September was totally dry. This rain means my farm’s winter wheat will actually germinate! But also, during this quiet time, I can think back on the process of stewardship and harvest. I know that now that we’ve started this transition strategy on Fish Fry Lake, I won’t stop it. I’m sure the lake would return to its original poor condition in a few short years. On the other hand, as noted earlier, I’m not sure how long we have to continue harvesting more than the inflow nutrients. There is merit in the harvest.

I do know that nature is helping us. Two summers ago we found fresh water sponge colonizing plant roots below a floating island. It’s a very basic form of animal life, and it’s a filter feeder, helping us towards even greater water clarity, allowing sunlight to reach even deeper into the lake. I also see the fishery evolving. Largemouth spawned here this year, and with the large forage base are likely to become another serious factor connected with the value of the harvest component of managing nutrient loads.

bounty of harvested fish is a visual example of the removal of phosphorus from the lake

STEWARDSHIP: Fish Fry Lake will likely become more like a sport fishery instead of a research pond oriented around nutrient removal to achieve health. The reason is that bass are a trophic level above bluegill. So where I could catch a thousand pounds of bluegill, now I will only be able to harvest 100 pounds of bass. Much of the phosphorus associated with bluegill will continue to circulate in the lake. An interesting challenge, and I really look forward to watching all this unfold. It won’t totally surprise me if the lake will yield the same 16 pounds of phosphorus, even with the largemouth bass factor.

I really don’t know of anywhere else in North America where such measurement happens, except in aquaculture settings, where even more rigorous attention to water quality is required. The average pondmeister doesn’t want to be harvesting canoe loads of aquatic weeds, much less measuring their phosphorus content! But if you do have mineral-based fertilizer getting into your pond, you have to do something. You have to harvest, or your fish will go away. My challenge, and maybe yours, is to figure out a way to make this harvest process fun!

For a waterway to be in ideal condition, nutrients coming in must match nutrients going out. In fact, lakes and ponds really never achieve this perfect balance, but as pondmeisters know, if your pond gets too unbalanced in favor of nutrients coming in, then disaster looms! This is especially true if the nutrients enter in the form of mineral-based fertilizer.

Remember that line from the good book? It goes something like “To them that have, more will be given.” Well, Matthew knew what he was talking about, and when your system is healthy and nutrients are cycling through at a ferocious rate, this miracle of abundance materializes.

How do you make sure the food web is functioning well? There are hundreds of internet pages dealing with pond management and stewardship. But for now, let’s look at this idea: we must harvest in order to have more harvest. It’s really that simple. We humans are a vital part of the food web, and if we don’t accept responsibility that comes with our place near the top of the food web—in other words, if we don’t steward and also harvest—the whole thing can come crashing down! This is absolutely what happens today, with fertilizer in such abundance. For right now, let’s look at the HARVEST side of this conundrum.

a person reeling in a fish from a wild fish habitat
My wife and I love to go out fishing and so do the dogs!

Here at Shepherd, Montana, we are performing a long-term test. We measure a lot of stuff, including our harvest. Our water is heavily influenced by phosphorus due to nearby corn farming practices and irrigation. Water migrates through our property from nearby agricultural interests. We get their excess fertilizer. Floating islands are developed and launched on Fish Fry Lake. They filter the water, improving clarity.

Fertilizer from past years still present on the lake’s bottom combine with sunlight, which due to clear water, now extends far deeper into the lake, resulting in explosive growth of aquatic vegetation. This is part of the lake’s transition to health, as long as vegetation is harvested. Grass carp or manatees are not an option here! So it’s up to our ducks, some kind of micro-harvester system scaled for a 6.5-acre pond, or the backs of our helpers to rake it up to use for a different purpose. In our most ambitious year we harvested 43,700 pounds of aquatic weeds by hand and rake. All this work only translates to 6.8 pounds of phosphorus! Aquatic weeds are mostly water.

We bump up aeration/circulation in the lake with two floating streambed embodiments of floating islands. This allows for optimal cycling of nutrients through the islands, and it also allows for sufficient dissolved oxygen to keep warm water fish, like yellow perch, black crappie, bluegill, and redear sunfish alive. We average harvest of 1,400 pounds of fish a year. We initially focused on yellow perch, which translates to one pound of phosphorus per 105 pounds of perch. This translates to fish being our best means by which to harvest phosphorus, at about 12 pounds per year.

biomass that grows on floating islands and other harvested offal can be upcycled into garden fertilizer
In 2016, we fed worms and our vegetables from the pond too!

I can say from direct experience that hand/ rake harvest of 43,700 pounds of aquatic vegetation over the course of one summer in 101 canoe loads is NOT a preferred method to harvest phosphorus! Our backs still ache. On the other hand, feeding that aquatic vegetation into nightcrawlers has been a great hit! The worms provide bait and end up back in the lake, while the resulting worm castings are blended with fish residue and end up in the garden.

FISH: For us, healthy and vigorous fish are the ultimate marker of success. While we know of no other waterway in Montana that approaches our harvest per acre- foot of water, we’d like to keep pushing the envelope. Northern yellow perch, black crappie, bluegill, and redear sunfish dominate today, but largemouth bass are coming on strong. They are helping us put size on the prolific bluegill too.

When we aren’t fishing for a meal, we slot limit harvest one and two year old fish, which make up most of the phosphorus removal on Fish Fry. Now however, we are considering cycling some of them back into the lake. They would be returned to the lake in the form of fish meal, blended with fermented grain and some organic flour from the property. We dry the fishmeal at low temperature to preserve food value, and form it into feedable pellets aimed particularly at bluegill and other sunfish. This is quite a departure from our wild, non-fed, fish strategy though, so we are still scratching our heads. A question that comes up for example: Is there a risk associated with feeding fish from fish that derive from the same place? Perch eat their own fry, but bluegill are less carnivorous. So far, there are no contraindications in the literature, and several prominent fisheries experts agree this is a reasonable idea!

While we recognize if we start feeding fish, our wild fish status will change, we also know the quality of the fishery, particularly growth rates of bluegill and redear sunfish, could be enhanced.  All the feed, except a small fraction of fish oil, will derive from the property and will be trackable in terms of nutrients. Our goal is not to replace a natural diet, but to supplement and enhance fish diet, and thus enhance fish growth rate, especially of bluegill and sunfish. Growth rate of yellow perch is already off the charts, and we do not currently have growth rates of any kind on the black crappie.

AQUATIC VEGETATION: We view aquatic vegetation as an opportunity. It represents another way, if done efficiently, to cycle nutrients out of water. Weed harvest is expensive compared to fish. On the other hand, worms eat this material, and the resulting worm castings are truly a remarkable organic supplement to our gardens.

harvest fathead minnows grown to manage pond nutrients
Minnows uptake phosphorus, eat mosquito and midge larvae, and are fiscally prudent.

MINNOWS: Today we have a 5,000 square foot pond above Fish Fry (aptly named MINNOW POND) that generates between seventy and ninety thousand minnows per year. This translates to nearly three additional pounds of phosphorus prevented from entering Fish Fry, unless the minnows are released into the lake. These guys make life bearable here in mosquito season, as they are terrific mosquito larvae predators. They also consume larvae of the midge that spreads Blue Tongue, a devastating whitetail deer disease. Although it took what felt like a special Papal Dispensation, Montana FWP did grant us a permit allowing dispersal of these native minnows into nineteen different mosquito generating water features across the property.  So the fraction of minnows that don’t end up back in Fish Fry Lake contribute to our nutrient uptake quota. We also have visions of portions of Fish Fry Lake being developed into secure minnow production habitat so as to cycle nutrients into forage fish, and from there into the big guys we love to catch!

BULLFROGS: are another nutrient cycling opportunity! As a recent invasive species here in Montana, these guys are a new addition to our wildlife mix. We harvest between 5-600 per year, averaging 9 ounces each, which translates to 1.5 pounds of phosphorus per year.

ROUEN AND ROUEN HYBRID MALLARDS: They enjoy and thrive on our aquatic vegetation, and we enjoy them! Their organic guano cycles directly into periphyton, which cycles into minnows as well as panfish fry, so our ducks seem to be a real fit. We learned organic nutrients are way easier to cycle into fish than mineral-based nutrients (fertilizer). Trying to balance a reasonable number of ducks with the aquatic vegetation growth, maximized by clear water, is challenging, but interesting. And, duck eggs are delicious!

Another idea being considered for testing involves hyper-accumulator plants. There are unique plant types that can pick up massive volumes of phosphorus. Growing these on our floating islands could be another strategic way to increase harvest of phosphorus, but then we have to harvest elephant grass. Another project on the horizon!

Between 2013-2016, our measurements indicated Fish Fry inflowing between 13 and 14 pounds of phosphorus per year. We averaged, between all the various harvests, 16 pounds coming out. Keep in mind, we have an unknown phosphorus inventory to work down from several decades of phosphorus accumulation in the soil around what is now Fish Fry lake, so without a lot more science, we don’t know how many years of this harvest program are in front of us. We do know that if we don’t harvest, aquatic vegetation and algae will take over, unless we choose to poison the lake. For me, that is not an option.

2020: Four years after that article was written for Pond Boss magazine, we’ve seen a lot of developments here in Shepherd Research Center.  Here are some of the highlights:

giant fish string shows harvest of fish grown at the floating island lake
George with his fat bass catch in 2020.
  • We’ve tested a wide range of nutrient harvest systems.  The best one, unequivocally, is FISH.  It helps if the fish are tasty!  Think crispy fillets of three pound largemouth bass grown up on crawfish!
  • Our aquatic vegetation challenge has dramatically diminished.  It seems that crawfish are the reason.  They consume the vegetation, and in turn are consumed by bass and yellow perch and large crappie.  Note that Minnow Pond, our fathead minnow factory, continues to contribute to the system.  Growth rates on our bass, and perch, are outrageous!
  • Since we no longer have to rake aquatic vegetation, we no longer propagate earthworms.  Likewise, our bullfrog population has moderated.  A gigging episode might net 30 frogs, compared to 140 just a few years ago.  Where in the past the water was lush with bullfrog tadpoles, now they are far less frequent.  
  • Water clarity has decreased somewhat.  It’s typically about six to eight feet now, compared to as much as 19 feet in the past.  I see this as a challenge, and continue to experiment.  In fact, our nanobubbler research appears very promising around this issue.
  • We still target harvest of bluegill and sunfish of less than five inches, and crappie less than six inches in length.  These guys are simply frozen processed into canine food.  Occasionally we harvest bigger panfish for our consumption.  Fly fishing for eight to ten inch bluegill and redear sunfish is hard to beat!  We normally will land nine small panfish prior to catching an eight to ten inch one, but the hook and line catch rate is terrific, especially between May and mid July.
  • Over the last two years largemouth bass fishing has exploded!  We primarily use plastics.  From early June through September, catching six or eight keeper bass, those less than sixteen inches, has been our standard.  The fish are thick and wide.  A twelve inch fish provides fillets sufficient to feed two adults.  Seriously, the bass are awesome to eat.  Below, you’ll find a link to a recipe for “Crispy Bass” fillets that is truly an exquisite dining experience!  Check out the short video too!
  • Our phosphorus harvest rate has reduced.  However, it seems nature has filled in the gap.  Freshwater sponge, the wide range of other predators, the bigger game fish, all contribute to the health of Fish Fry Lake.  We have evolved into a pleasurable harvest routine.  So the question of how much inventoried fertilizer we needed to contend with has answered itself.  Nature has stepped forward.  
  • This winter we are developing an off-grid nanobubbler system, called the NanoHaven.  This is a breakthrough development, as nano bubbles are neutral buoyant.  What this means is that they take fourteen days to transmit their oxygen, completely, into water.  And they disperse throughs the entire water column, including that intractable benthic zone of dense, stratified water that otherwise slips into anoxic status.
  • If the NanoHaven is successful, it means that even deep lakes can be productive from top to bottom.  It will also bump up water clarity, meaning that sunlight, the second “engine of life”, will be brought to bear on most, if not all, of the water column.
fish fillets caught in a wild pond were fed on crawfish and taste delicious
Delicious wild fish filleted for lunch.

Frost and snow have arrived in Montana, so it’s the end of regular fish season, and approaching the ice fishing variation. We have a trap door in our floating gazebo, so ice fishing is actually quite pleasant. Harvest continues!

Here’s a link to that Crispy Bass recipe I mentioned.

And below is a two-minute bass video I thought you might enjoy.