Members of the South Dakota Game, Fish and Parks Department have been spending time on Rapid Creek investigating and documenting brown trout and other fish species to determine how they are faring since the detection of didymo (didymosphenia geminata). Didymo was discovered on the creek at least five years ago.

Some of the general things we have learned about didymo presence in our waters is it likes cool, clear, moving water. The algae essentially chokes out other life, invertebrates, that are essential to the healthy survival of fish species such as trout. If didymo continues to grow and expand, it can pretty much wipe out a fish species in those waters. Scientists are looking at ways to stop the growth and spread of the algae.

According to the Rapid City Journal, members of the Game, Fish and Parks Department have been monitoring the Rapid Creek for about 5 years. What they have learned is that the majority of brown trout found now in the creek are all of the 4-5 inch variety with very few mature adults and virtually a non existence of fish of the 6-9-12 inch range.

In the photo above, members are in the water shocking the fish. They collect them and take statistics while placing them in a holding area in part of the stream. Officials are reporting that this year the presence of didymo seems to have eased and they have found not only some larger trout but the 6-9-10-inch trout that have been missing.

In addition, scientists have been releasing nutrients, fertilizers, into parts of the stream that they think will help reduce the didymo. What they don’t know is if this apparent easing of the effects is the result of the nutrient release or a natural occurrence.

We also know that this algae in microscopic in nature and can cling to most any object. Most notably, anglers and officials have warned that felt-bottom waders or any object with a porous surface is more apt to collect and retain didymo, so it can live longer and be spread to other waters. Information has been passed around with advice and directions on how to help stop the spread.

Because of its microscopic nature, it can be spread in several ways, some of which I just mentioned. It can be spread by wind, by birds, by animals such as deer, moose or any animal that enters the water, exits and moves on to the next body of water. Another method authorities have warned about is activity within a body of water that loosens or dislodges the algae allowing it to more downstream and further spreading its devastation.

In short, once didymo takes root in a body of water, it’s nearly impossible to stop its spreading, not only in that body of water but also to other bodies nearby or anywhere in the world. Until a method to eradicate is found, our efforts are spent hoping to slow the spread.

I know that scientists are doing work in other places in the U.S. as well as in New Zealand where the algae is also prominent.

I do have one question that perhaps someone more enlightened than I can shed more light on. I’m not trying to be critical. My intention is to ask questions, learn and pass that on to others so that we can all learn more about this. Here’s my question.

If didymo can be spread further downstream by boats, animals or anything moving through and disturbing the algae, then what precautions have the biologists being shown in the photograph above taken to make sure that doesn’t happen?

Anyone can leave their comments below.

Tom Remington

Two men were ice fishing at Deerfield Lake, South Dakota. Both men hooked the same fish at the same time. The one with the 6-pound test line broke, leaving one fisherman, Ryan Rempfer, with his 3-pound test line to figure out how to get the fish up through the ice.

The fish weighed 11 pounds and 3 ounces and measured 30 inches breaking the old South Dakota record of 9 pounds and 3 ounces caught on the same lake.

Get all the details here. Good story.

Tom Remington