Aquaculture in Utah, July 1998
A Newsletter Produced by Utah Department of Agriculture & Food Fish Health Program
Fish Experts Gather In Colorado to Share Whirling Disease Research Findings
The annual whirling
disease symposium was held in Ft. Collins, Colorado in February 1998.
The theme this year was "Research in Progress" and most of the
presentations were reports of ongoing projects. Sponsors of the meeting
were the US Fish and Wildlife Service, Trout Unlimited, Colorado Division
of Wildlife, Federation of Fly Fishers, Montana Fish Wildlife and Parks,
the Orvis Company, and Utah Division of Wildlife Resources.
The first session covered the impacts of whirling disease, with presentations that discussed effects seen in fish from Colorado, Utah and New York. In some areas of the country very dramatic effects have been documented in fish populations, whereas, other areas show minimal or no adverse effects. Colorado biologists reported finding juvenile fish with signs such as "pop eye", blacktail, and whirling behavior in certain rivers. In preliminary work by UDWR at Porcupine Reservoir, cranial deformities and spore counts increased in infected kokanee salmon without an apparent decrease in redd numbers. New York workers are finding that populations of both brown trout and rainbow trout are maintaining even in whirling disease positive areas. A California biologist reported that at least in one steep gradient coastal river, the infection rate is decreasing after some positive earthen ponds were closed.
The second session discussed how the whirling disease parasite is related to Cnidarians, which are the jellyfish, hydras, sea anemones, and corals. The relatedness is based on genetic studies which compare the DNA of the organisms and determine how closely or distantly they are related.
The third session covered internal and external factors which influence the severity of the disease. Presentations covered the age and species differences with respect to susceptibility, the number of spores found in infected fish, the various water quality and stress factors that may increase susceptibility, and the immune response of the fish to infection. Research in Wyoming shows that the typical whirling behavior seen in infected fish is probably not due to damage to the inner ear structures, as previously thought, but is more likely due to damage in the base of the brain and spinal cord. Studies of immunity show a very weak immune response to the infective stage of the parasite.
The fourth session dealt with the alternate host of M. cerebralis, the oligochaete tubifex worm. Identification of the worm from samples which contain several species of worms is difficult. Studies are underway to find out if all tubifex worms are identical and if the parasite can be transmitted by other species of worms. The parasite has been found to invade other oligochaete worms, but apparently does not complete its life cycle. Molecular and genetic laboratory techniques are being used to complete many of these studies.
The topic of the fifth session was diagnostic methods. Talks covered the use of histology, PCR (polymerase chain reaction), and in situ hybridization for diagnosing the condition. Each method has value, but neither is completely foolproof. Inaccurate testing results are possible with any of them. PCR may eventually become a standardized test method after the procedure is validated and standardized across the country. Histology is the current "blue book" method for confirmation and is used by the Utah Department of Agriculture and Food for that purpose. Much controversy surrounds the selective use of PCR and how to deal with the results.
The last morning of the symposium was taken up by a panel discussion of how to apply the research to management of the disease. One presenter talked about public education and the need to keep the information positive and simple. The general public needs to understand basic scientific methods and principles, but also needs to have the answers to their most basic questions, which usually are along the lines of "How does this disease affect me?" Others talked about the need for a national database so projects aren't duplicated and funding is used in the most effective manner. Some discussed their ideas on research that still needs to be done and how best to survey wild and feral fish for the disease.
Next year's meeting will be in Missoula, Montana sometime in February.
Water Quality In Aquaculture
The use of probiotics in veterinary medicine goes back many years. The principle is to provide an animal with additional beneficial intestinal bacteria. These bacteria will colonize the gut and displace or destroy harmful bacteria. This method of treatment generally decreases the incidence of disease and reduces the need for using antibiotics.
This same idea has been applied to aquaculture with similar benefits. Probiotic products are now available that, when added to the water, will break down excess organic matter, neutralize ammonia and nitrite, reduce the concentrations of pathogenic bacteria, and may stimulate mucus production by the fish. All these functions reduce stress on the fish, increase resistance, and help establish a healthier aquatic environment. This lends itself to a more productive system and healthier fish.
These products can be used in ponds, raceways, tanks, and recirculation systems. They are most valuable in those situations where the water moves slowly or is reused. Newly built ponds and tanks can be treated with these products to decrease the time before fish are stocked. They are available from most aquaculture supply companies and go by various brand names.
Zebra Mussel Task Force Organized
In two previous issues of Aquaculture In Utah, we presented information on the zebra mussel and its potential to spread to this state. Other groups have also been thinking of the risks and are beginning to prepare. On April 7 and 8, 1998, a symposium was held in Salt Lake City at the Department of Natural Resources building. The objective of the meeting was to learn more about this exotic nuisance and to organize a task force that will monitor state waters and attempt to prevent any introduction.
Representatives of many state and federal agencies were present for the training session. Some of those present were US Fish and Wildlife Service, US Park Service, US Forest Service, Division of Wildlife Resources, Utah Dept. of Agriculture and Food, Bureau of Reclamation, and others.
The first day covered the history of the zebra mussel, its spread through Europe and into North America, some common myths about the mussel, its biology and environmental requirements, the impacts it has had on recreation, power generation, water treatment and ecosystems, control methods, potential risks of spread by aquaculture, boating, shipping, and fishing, and how and why we should organize an effort to prevent its spread.
The second day involved a smaller working group from various agencies that set up a purpose statement, objectives, plans for monitoring and reporting, a list of all stakeholders who need to be included in the future, contact lists, ideas for information and educational leaflets, and decided on a next meeting in July. Some individuals were assigned tasks to complete within the next two months. A draft of the meeting will be sent to all who participated.
It is anticipated that this group will, in the future, work on other aquatic nuisance species. The zebra mussel is currently at the top of the list of those exotic species that are causing severe damage to the environment and several industries. The Department of Agriculture and Food and the aquaculture industry have a stake in this issue and will be represented on the task force.
If you would like further information, especially concerning the impacts on aquaculture, call the Fish Health Program office at (801) 538-7029.
Visual Sound Bytes
Ten fish health inspections have been conducted this spring with no listed pathogens detected. Three or four more sites may be inspected during the summer. Our hats are off to you producers for the efforts to prevent the introduction and spread of fish diseases. Questionnaires have been sent to all the aquaculture and fee fishing operators. Our intent is to find ways to improve and expand our services to the industry. We appreciate the approximately 20 responses we've received and would encourage those of you who haven't yet answered to do so soon. The results of the questionnaire will be available for anyone interested.
The bad news of this edition is that the Division of Wildlife Resources reports the finding of whirling disease in the upper Provo River above Jordanelle Reservoir. The source of the pathogen apparently is the Weber drainage via the irrigation diversion just west of Francis. Testing will be done at Jordanelle to monitor spread.
Sanitary inspections of brine shrimp processors have been conducted. These are performed on a quarterly basis for issuance of veterinary health certificates on the product. These certificates are required by certain foreign countries prior to import.
The National Aquaculture Association has circulated a document which can be used by producers or other interested parties to solicit support from their national legislators for increasing the availability of approved drugs for minor species and minor uses (MUMS), ie. fish. A copy of the letter is included for your use. We encourage anyone affected to send the letter to their Senators and Congressmen.
Aquaculture Bill Passes
I'm pleased to spread the word on the passage of HB 407 with aquaculture amendments and to correct some misconceptions.1,2 HB 407, supported by Utah's aquaculture industry, Departments of Agriculture and Natural Resources, passed; HB 459, supported by special interest groups, did not. The new HB 407 will engender more cooperation and communication between agencies involved in fish disease issues. Agency responsibilities are more specifically defined, and the new fish health policy board will have increased responsibilities for control of fish diseases. Thanks go to all in the aquaculture industry, to the Division of Wildlife Resources, and to many individuals and associations for your participation and assistance in the passage of this important legislation. We look forward to a continued good relationship with the aquaculture industry and to continuing aspirations to serve all parties and the state of Utah in the fish disease control arena.
1 The Landing
Net, April 1998 News and notes from the Stonefly Society of the
2 Trout Unlimited, Utah Council, June 1998 newsletter, pp 1, 2, 11.
Utah Aquaculture articles written by Kent Hauck, Division of Animal Industry, Fish Pathologist and Dr. Russell Lee, Division of Animal Industry, Fish Health Specialist.