Different Factors that Disrupt a Trout’s Ecosystem

Freshwater trout are one of the most sensitive fish that humans come into regular contact with. This is why it is so important to know how to handle fish when you fly fish. However, humans are not the only factors that impact freshwater trout. In this post, I will address both abiotic (nonliving) factors and Biotic (living) factors that impact freshwater trout.

Let’s start with abiotic factors. An abiotic factor is a chemical or physical component of an ecosystem that affects organisms within that ecosystem. Many abiotic factors impact trout in their ecosystem. One of the most critical factors for a healthy ecosystem is water temperature. Trout thrive in colder water ranging from 45 to 65 degrees Fahrenheit, which is also rich in oxygen. This means cold moving water, such as a mountain stream, is the ideal habitat for freshwater trout. The next most important factor is likely the pH level of water.  The pH level, or scale, indicates how acidic or basic the water is.  Trout, unsurprisingly, thrive in neutral water with a pH around 7. The final critical abiotic factor that is worth highlighting is water flow. A strong water flow is important for fish because strong currents bring oxygen and food. However, if a current is too strong, it has a negative impact on trout reproduction, as eggs wash away. The best water flow for fly fishing is around 100-400 cfs (cubic feet per second).

Now, let’s address Biotic factors. A biotic factor is any living component of an ecosystem. In a trout ecosystem, one of the most essential Biotic factors is the hatches of the insects around the water. A hatch is a mass emergence of small aquatic insects that are transforming from their nymph stage into the winged stage, i.e., flies.  These hatches are critical as they provide an essential food source for trout.  Understanding hatches is critical to success as a fly fisherman because, most of the time, they determine what fish are eating, and when they eat. Below is an example of a hatch, which I recorded on my phone. 

Human activities are also a very important biotic factor. Urban development is a significant threat to freshwater trout as it destroys habitat and when it does not destroy the habitat it often impacts the ecosystem around the river, resulting in hatches not being as abundant.  This leads to not only less healthy fish, but also fewer fish in general.