Aquatic Invertebrates of Montana

Recommendations

• Conduct further transmission experiments with other species of tubificids. Everything below assumes Tubifex tubifex is the only host. The most important species in our area for testing are probably Limnodrilus hoffmeisteri, Rhyacodrilus coccineus and Ilyodrilus templetoni

   

• Reduce habitat degradation of important trout streams, especially rearing streams (should I have to say this?). Metal and acid pollution from mines might be harder on the worms than the insects, but all other forms of habitat degradation are likely to favor Tubifex tubifex.
  1. Almost any reduction in the native community diversity favors Tubifex tubifex.
  2. Organic enrichment from humans or animals increases Tubifex densities.
  3. Sedimentation from forest cutting, roads and grazing reduces community diversity and improves Tubifex habitat. Overgrazed streams full of sediment and manure make very good Tubifex tubifex habitat.
  4. Dams simplify the insect community, encourage sedimentation, and they often release water that is rich with nutrients or organic material (algae, bacteria and crustaceans).
  5. Irrigation ditches can support incredible densities of tubificids, probably mostly Tubifex tubifex. These may also contain winter-killed fish as a source of disease spores.

      

   

• Forget general oligochaete elimination by chemical methods. Aquatic oligochaetes play an important role in converting bacteria sized food into sizes usable by other invertebrates and by fish. Oligochaetes are also concentrated in backwaters, deep in the sediment and in seepage areas which would make effective treatment difficult. Attempts at general elimination are likely to have major consequences on the community and increase the number of Tubifex tubifex in the long term!

   

• Forget predator and competitor introduction. Tubifex tubifex is a worldwide organism that deals with predators and competitors so poorly that it will not be abundant if the habitat is suitable the predators and competitors. Attempts to introduce these species will likely be a wasted effort with unpredictable impacts on other species.

   

• Tubifex tubifex reduction by way of a species specific disease organism might work, but caution is needed, as always, in this area. In addition to the normal bio-control risks, the loss of Tubifex tubifex, as one of the last macro-organism to occupy some badly degraded areas, might cause some expansion of these areas.

   

• Cure the worm- not the fish, where curing the worms means to prevent the development of fish infectivity. While everybody seems to consider finding or creating resistant fish stocks, I have not heard of anyone trying to block the disease cycle at the level of the worm. This might be practical and it has a great advantage. The worm is a single worldwide species so curing the worm could help the problem for all salmonid stocks that we so dearly love just the way they are. The worm is also well suited for small scale laboratory work and for mass production.

   

• Hope for (wild rivers) or produce (regulated rivers) favorable timing. Worms, fish and parasites can probably all live together as long as the parasite load on the very young fish is not too high. The good escapement of the Madison River young of the year to form a strong 1995 yearling class suggest that this must be so. The key elements are hard to predict, but they might include some sediment flushing just before the young fish emerge and then steady or slightly increasing flows afterward. During sediment flushing from high water or ice flows the worms suffer heavy mortality, but most of these will be eaten by something. Falling water levels may also bring worms to the young fish as both are often concentrated in shallow water near shore. Temperature is also important as the growth of the young fish is a race against major episodes of parasite release by the worms. This could be a productive area for research, but it is likely to be very difficult.