Spring Iowa Trout Fishing, Good and Bad Runoff

It’s definitely Spring! Heavy runoff started on many creeks yesterday and some on Sunday. This is a challenging time for many trout but luckily most of them are quite capable of acclimating to these sudden changes; though, prolonged periods of high muddy water can be quite dangerous for trout and other fishes.

Relevantly, it is important to be conscious of what kind of ‘dirty’ water we are observing as we spend time in relationship with the streams. Stained water with a blue tint is a GOOD kind of ‘dirty’ water! If it is creamy colored then we would call that a calcareous stain. It is caused by the calcium that makes up the beautiful limestone bluffs (as calcium carbonate) of NE Iowa, and many of them line the banks and border the streams that we fish. Stain often means that there is a healthy amount of nutrient influx into the streams. This nutrient influx is called ‘allochthonous organic matter’ because it is organic matter that has moved into its current location from a distal one [1]. Moderate amounts of allochthonous organic matter are healthy for a stream because an influx of nutrients triggers what is called ‘autochthonous production’ usually in the form of microbes processing and converting these nutrients. This conversion makes the allochthonous organic matter into bioaccessible compounds for aquatic autotrophic organisms to be able to use, which are often photosynthesizing organisms as well. As you likely learned in school, photosynthesis is what creates oxygen, which allows oxidative respiration as a gas exchange process to occur in aquatic and terrestrial organisms like fishes and humans. Many of those microbes that process and convert the nutrients coming into aquatic environments also use oxygen in this process, so this is why BALANCE is so crucial to any topic of ecological health. All this to say that these moderate levels of nutrient influx are actually quite healthy for aquatic and terrestrial environments alike. Important fact: historically, 70% of the Earth’s atmospheric and aquatic oxygen is produced by aquatic phytoplankton, also known as microalgae [2]; however, scientists suspect through research that the number today is more like 50-80% because of a 40% decrease in phytoplantokic communities (mostly in the ocean) having been killed by the warming of aquatic environments since 1950 [3]. With these increases in seasonal algae die-offs comes more autotrophic production which uses up oxygen so when there is an overloading of nutrients, or in this case, it’d be in the form of an algae die-off as detritus (dead organic matter) there is an immense decrease in DO (dissolved oxygen). Simply, a large algal die-off leads to large oxygen consumption which leads to the suffocation of fishes and any other oxidative respiring organism downstream called dead zones. This is what happened at Bloody Run Creek last year as a result of nutrient overloading (see references to read another informative article about the cost of trout and the catastrophic situation of Bloody Run last year) [4].

So, I’ve already laid out the bad processes that can lead to bad ecological conditions of aquatic environments through (1) terrestrial (allochthonous) nutrient overloading exemplified by Bloody Run with “colossal” amounts of fecal waste produced and mismanaged by large cattle operations, (2) through warming aquatic environments leading to larger than normal seasonal die-offs of algae leading to dead zoning, (3) as a response to nutrient overloading increasing the level of autotrophic production leading to dead zoning and larger algal die-offs at the end of the season, and (4) is what I will elaborate on in the following. Consequently, the BAD kind of dirty water is when the streams get muddy or brown colored because it means that a lot of loose sediment (and fecal waste, as we know from the above scenarios) eroded/carried into the water by melting snow and/or rain. Erosion along streams in Iowa is often caused by unsustainable farming and cattle operations (small or large). There are a number of ways to address this, one of which is by farming cover crops after the seasonal harvest of corn, soy, and various other crops. The roots of these cover crops hold the soil down so that less of it gets carried into streams and rivers. Cover crops are immensely important because the topsoil (the surface soil that is often eroded away) is extremely rich in nutrients and microbial communities that make up the fertile soil matrix for future generations of plants to grow (including corn and soy). As many Iowans already know, the erosion of topsoil is such a big problem that topsoil is actually commodified (sold), yet often these same consumers of topsoil do not take further precautions to ensure the reduction of future erosion, which leads me to my next point about native prairie. Additionally, native prairie buffers can be strategically used to also hold down topsoil and actually hold water as well which is good for increased terrestrial microbial respiration and obviously for the access of mono crops to a water source during the late Summer heat. Similarly, terraces are the last point I will make here about reduction of erosion/sediment loading into streams. The construction of terraces are an ancient technique engineered by the Indigenous peoples of the Andean mountains in South America [5], which in their Quechua-language are originally called “patas” [6], and in Spanish called “andén”, which means platform. Terraces hold many benefits and within an Indigenous context could potentially be used more dynamically in Iowa as well. Some of these benefits include, “utilizing steep slopes for agriculture, reducing the threat of freezes, increasing exposure to sunlight, controlling erosion, improving absorption of water, and better aeration of the soil” [7].

Before we get to cattle, a tangential topic in the intersectional conversation of sedimentation, farming practices, and eutrophication (nutrient overloading) is that an overwhelming proportion of agricultural nutrients being eroded into streams are nitrogen and phosphorus [11]. This is called nutrient pollution. We know that over “90% of stream nitrate is from agricultural sources in Iowa” [11]. Here are some facts about Iowan nitrate loading in recent years: “for the 2019 Water Year (10/1/18 to 9/30/19) Iowa stream nitrate load was 980 million pounds” & “since 2003, statewide stream nitrate loads have increased 100.4% (i.e. doubled), as measured by the 5-year Running Annual Average” [11][13]. Now for the kicker, Iowa contributes an average of 55% of the nitrate load to the Mississippi-Atchafalaya Basin [12][13], which has contributed to a 6,000-7,000 square mile dead zone (largest recorded thus far is the size of New Jersey!) [14]. Not to mention the human health impacts the these Nitrogen Pollution is having on drinking water in Iowan communities [15]. So, Iowan sedimentation and nutrient pollution doesn’t just impact Iowan trout streams...

Continuing with some basic solutions for cattle, implementation of fencing-off what is called the riparian stream corridor is very important. A riparian corridor is a zone of land that lines the banks of the streams and rivers (the land you stand on when you fish is the riparian corridor). These riparian environments are incredibly important ecological components to sustaining the integrity and health of terrestrial and aquatic ecosystems. Using the same concept as cover crops, roots of riparian vegetation are what hold the soil in place, but if cattle (which weigh ~1,400lbs.) are stomping on and laying on these areas, the soil will be loosened and fall or erode into the stream by precipitation. This trampling in combination with grazing of these riparian plants cause major problems for the streams by covering the gravel substrate with sediment and slit. Gravel exposure is another vital structural component of aquatic environments because the interstitial space between and under the gravel is where an overwhelming proportion of aquatic macroinvertebrates (that many of you like to tie and imitate) live. Mayflies, case-building caddis, and stoneflies are just a few famed critters that call these small living-quarters home [16]. Additionally, the silting/sedimentation of streams is the process by which the substrate is covered by silt and other fine sediments. This posses a major problem for aquatic environments.

Here are some of the ways it impacts trout fishing directly, and the future of trout fishing:

(1) no gravel exposure means less bugs (i.e. trout food)

(2) no gravel exposure means less or no aquatic macrophytes (such as watercress, although a non-native species, offers premium habitat for scuds and sow bugs, which are a primary food source for trout in the Driftless Region) which impacts dissolved oxygen levels in the water as well,

(3) a major reduction and sometimes even elimination of hydraulic conductivity as a groundwater source. Some of you may already know about the famed story of the rebirth of a spring on upper Waterloo Creek, see references for the link to this story [17]. There’s even a book called Creekfinding [18 ]. In the scientific literature we refer to “spring-fed streams” as “groundwater-dominant streams” because there these streams are actually mostly fed by groundwater influxes from the substrate of the creeks themselves, NOT always entirely from springs at the headwaters of streams. This does NOT mean that the springs should be disregarded and mismanaged, but there is a common misconception that is perpetuated by using the term “spring-fed”. There is nothing technically or semantically wrong with using “spring-fed”, but “groundwater-dominant” is a more inclusive term applied to the holistic geologic cycle of water. So, by allowing a groundwater stream in particular to fall victim to sedimentation is directly impacting the largest groundwater source for that stream. This will create much higher temperatures in late Summer and much colder temperatures in the Winter. These large swings in temperature have a direct impact on trout mortality during these marginal periods and growth rates [19].

(4) no gravel means nowhere for the fish to spawn/lay their eggs trout need gravel to create their redds (nests) to properly incubate their eggs [20], simple. So if the gravel is covered by silt, there is no chance of wild populations. There are innumerable examples of this across the country, which is needs to be addressed.

(5) no gravel = no groundwater dominance = no food = no wild fish = more stocked fish = WAYYY MORE MONEY FOR YOU... and if you look at reference [4] you’ll know how much stocked trout cost, and why that might not be such a great idea... just a thought...

So, fencing off cattle from getting to the riparian corridor is very very important, but of course cattle need water too, so usually the best option is to have an easement where cattle can access the stream in a safe way to drink and bathe. At this point, I think you understand where I’m coming from.

The bottom-line is that if you love or need trout fishing (this has nothing to do with the type of fishing) then we NEED to be having more of these conversations and pushing legislation to address these issues as a community. Being an intentional angler with a sustainable IMPACT is how we PROTECT what we love and need!

Tight Lines!

Marco Kamimura

REFERENCES

[1] https://www.ecologycenter.us/species-richness/autochthonous-and-allochthonous-production.html

[2] https://web.uri.edu/smile/files/Save-the-Plankton-Breathe-Freely1.pdf

[3] https://oceanservice.noaa.gov/facts/ocean-oxygen.html

[4] https://www.iihr.uiowa.edu/cjones/on-brothels-and-cathedrals/?doing_wp_cron=1615297290.5255949497222900390625

[5] https://en.m.wikipedia.org/wiki/And%C3%A9n

[6] https://www.tandfonline.com/doi/abs/10.1080/00043249.1982.10792793?journalCode=rcaj20

[7] https://web.archive.org/web/20101214103311/http://www.rlc.fao.org/es/tierra/pdf/capta/siste5.pdf

[8] https://www.google.com/search?q=Iowa+nutrient+pollution&oq=Iowa+nutrient+pollution&aqs=chrome..69i57j33i160.8642j0j7&sourceid=chrome&ie=UTF-8

[9] https://www.card.iastate.edu/ag_policy_review/article/?a=88

[10] https://cdn3.ewg.org/sites/default/files/u352/EWG_RacoonRiverReport_C02-min.pdf?_ga=2.169880036.592862072.1615306914-660576078.1615306914

[11] https://www.iihr.uiowa.edu/cjones/iowa-is-hemorrhaging-nitrogen/?doing_wp_cron=1615307060.0225551128387451171875

[12] https://www.researchgate.net/publication/324490117_Iowa_stream_nitrate_and_the_Gulf_of_Mexico/fulltext/5ad07b090f7e9b18965d5f68/Iowa-stream-nitrate-and-the-Gulf-of-Mexico.pdf?origin=publication_detail

[13] https://www.sierraclub.org/sites/www.sierraclub.org/files/sce/iowa-chapter/water/TheNutrientProblem.pdf

[14] https://serc.carleton.edu/microbelife/topics/deadzone/index.html

[15] https://e360.yale.edu/features/in-the-heart-of-the-corn-belt-an-uphill-battle-for-clean-water-iowa

[16] https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/macroinvertebrates

[17] https://www.google.com/amp/s/amp.desmoinesregister.com/amp/100388248

[18] https://www.upress.umn.edu/book-division/books/creekfinding

[19] https://www.tandfonline.com/doi/abs/10.1577/1548-8640%281995%29057%3C0231%3ATAGRCO%3E2.3.CO%3B2

[20] https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/93WR00402