Effects of age, growth, and diet on characteristics of salmon fingerlings
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Geology topics
Publications and source records attributed to Roger E. Burrows.
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Bacterial gill disease plagues salmon and trout in many hatcheries: some infections are sporadic, but others are continual. An inexpensive, easily applied, stable, safe chemical would be highly advantageous for treatment. The use of Roccal as a 1-hour treatment for bacterial gill disease (Fish 1947) was developed at the Leavenworth (Washington) Station of the Fish and Wildlife Service in 1942 and was quite successful. Since then, Roccal has been used extensively; but because of variability in composition, its efficacy is not consistent (Rucker et al. 1949). The objection to the variability of Roccal was overcome by using another compound, pyridylmercuric acetate, which was suggested by Van Horn and Katz (1946) as having some therapeutic therapy. Pyridylmercuric acetate was tested experimentally at the Leavenworth Station and was found to be very effective for bacterial gill disease. This compound had highly differential toxicities for bacteria and fish but was quite expensive (Rucker 1948, Burrows and Palmer 1949, Snieszko 1949). Another objection to pyridylmercuric acedate was its toxicity to rainbow trout—not to other species of trout or to salmon—at the concentration necessary to control the bacteria (Seaman 1950, Rodgers et al. 1951, Bryant 1951, Foster and Olson 1951).
In a search for more effective disinfectants to combat parasitic diseases of hatchery fish, the authors report results from a series of experiments designed to determine the toxicity of varying exposures to concentrations of formalin, sodium p‐phenolsulphonate, ammonium sulphate, and sodium benzoate. Non‐toxic concentrations of these disinfectants were tested, in addition to the usual hatchery methods of salt treatment and hand dipping in copper sulphate and acetic acid solutions, on No. 1 brook trout fingerlings which had been experimentally infected with the protozoan parasite Trichodina sp. (previously known as Cyclochaeta sp.). Of the disinfectants tested, only formalin completely removed all parasites. Salt treatment in a 5 per cent solution, by weight, as well as hand dipping in 1:500 acetic acid, failed to eradicate all parasites present, although a marked reduction in their numbers did occur. The hand dipping in a 1:2,000 copper sulphate solution was found to be without practical value for the removal of parasites. The authors recommend a prolonged treatment for sixty minutes by recirculating a 1:4,000 solution of formalin, or, where circumstances permit, a 120‐ to 150‐minute exposure to a 1:6,000 concentration of formalin, as the most effective, most economical, and least toxic treatments for combating infections of Trichodina sp., and presumably those of other external parasites as well, among hatchery fish.