The connection between limestone and trout

How Missouri geology helps to make a great trout stream

You may know that Missouri has been blessed with an abundant amount limestone. Missouri produces more than 18% of the U.S. lime production and has the largest cement kiln in the world.  Due to its unique characteristics limestone can be used for many different purposes ranging from the manufacturing of paper, plastics and steel to the treating of air emissions. It is even used in several food products and as a stomach antacid. However, did you know Missouri’s underlying limestone bedrock and highly weathered karst landscape has produced some of the largest springs and best trout stream habitat in the Midwest?

Yelton Spring, Phelps County, Missouri

One of the characteristics of limestone chemistry is its ability naturally buffer acids, including acidic rainwater. This is important to fish and aquatic life because it helps protect against rapid changes in pH. As rainwater infiltrates into the ground and becomes groundwater, the limestone and slightly acidic rainwater react. The result is an increase in the alkalinity of the water while at the same time small amounts of limestone are dissolved away. This results in the karst landscape and large springs of which Missouri is famous. In addition to the benefits of the buffered water, springs and the spring creeks below them have a much more consistent year-round water temperature ranging from 58 to 61 degrees. This temperature consistency allows for a steady growing cycle of vegetation as well as the trout’s food species such as macro invertebrates and other smaller fish.

Small Wild Rainbow Trout

The relatively consistent discharge/flow rates of the springs and temperature consistencies make Missouri a great place to fish for trout during the winter months. Most spring creeks seldom freeze so they are accessible to fishermen year round and since it is winter the crowd of paddlers, swimmers and other fair weather fishermen seem to stay away. During the winter months it is not uncommon to fish all day and never see another fisherman.

To read more about Missouri limestone, Missouri caves or Missouri karst landscapes check out a Geologic Column of Missouri at http://dnr.mo.gov/geology/geocolumn.htm.  For more information on spring discharges and spring locations visit http://dnr.mo.gov/env/wrc/springsandcaves.htm#Springs.