by Hannah Pennebaker , January 05, 2020

While driving past the Puyallup River on my way to Sportco to pick up Christmas presents, I noticed the water level was higher than I'd ever seen it. The murky water overflowed the banks and at times almost reached the roadway. Entire trees were almost underwater and previously exposed sand bars were submerged. I knew my fishing spots would be changing for next season, and I couldn't help but wonder how the flooding impacts fish. Do they get washed downstream? Do they seek shelter in slower moving currents and small tributaries? I worried about the eggs of recently spawned salmon, and if they would get swept downstream or actually be safer from predators due to the higher water levels. Flooding is usually good for river ecosystems, but I wanted to see how flooding effects fishing. With increased water levels, it seems like it would be harder to locate fish. Certainly water level impacts our fishing strategies. Old holes get washed out and new holes appear as water takes a different path downstream. Rivers change every year. They say knowledge is power, and understanding how water conditions such as flooding effect fish can help fishermen develop strategies to catch more fish.

First off, it's important to understand the effects of flooding on riparian ecosystems. Floods are usually good for a river's health. Sediment gets lifted and deposited downstream. These nutrients support plant and animal life wherever they settle, replenishing top soil and creating a barrier against erosion. Trees and debris get uprooted and get stuck, creating major fish habitats. However, floods aren't all good news for salmon. Major floods can uproot and wash away salmon eggs, particularly for species such as pink and chum salmon which deposit their eggs in shallow areas. If a flood causes erosion, the settling sediment can kill and bury eggs. Floods have been a naturally occurring phenomenon for thousands of years, so fish have also evolved certain strategies to combat this. Salmon lay their eggs in nests called redds. Coho have a long spawning period and they tend to spread their redds out. Chum salmon deposit their eggs in small tributaries and areas with less flooding. Chinook salmon are larger and can move larger rocks to place their redds within, creating better shelters. Salmon eggs are most vulnerable before they develop eyes, and are more susceptible to sediment damage. Floods can cause problems for humans as well as fish. Going back to our Puyallup River example, flooding there may cause damage to levees and wastewater treatment plants. Even residential areas and roads may flood, potentially causing injuries or deaths.

Floods are a mixed blessing for people and ecosystems, but let's examine how they effect fishing. As we discussed earlier, flooding carves out new channels and deposits rocks and logs to create different structures. Access points along the rivers will be different each year as well. We've all gone to our favorite hole for the first time in a season and discovered new shore access points or covered up old ones. In a flooded river, fish cling to the bottom, avoiding the faster moving surface water. Bass and trout are hardy, and most likely won't get pushed around too much. They'll take cover behind rocks and logs to rest. Watch out for new snags you may be unfamiliar with. Try new spots to see how they've changed, as the fish May be holding in different places. But above all else, be careful. Fishing a flooded river is extremely dangerous. Bank access will likely have changed, and the water will be moving faster.

Now you know how floods effect rivers, fish, people, and fishing. They have both positive and negative effects on fish, particularly on fragile salmon eggs and fry. Floods change the river every year, creating new habitat and structure, but also potentially washing away and smothering salmon eggs. Floods deposit sediments and nutrients in farmlands, but also damage levies and buildings. They are a powerful natural process, and all fishermen should familiarize themselves with their effects on our fisheries.

Hannah Pennebaker graduated from Pacific Lutheran University with a degree in Environmental Studies. She enjoys both freshwater and saltwater fishing adventures in the Puget Sound area with her fishing group, the Straw Hat Fishermen.