George E. Howe

Toxicity of Erythromycin, Oxytetracycline, and Tetracycline Administered to Lake Trout in Water Baths, by Injection, or by Feeding

Abstract The toxicities of three antibiotics, each administered by three routes at doses up to five times the recommended concentrations, were determined in lake trout (Salvelinus namaycush). In water bath exposures, erythromycin phosphate was considerably less toxic than oxytetracycline hydrochloride (OTC) or tetracycline hydrochloride (TC); however, the toxicity of all three antibiotics was low. Injections of erythromycin produced no deleterious effects, even at concentrations four times the standard dose rate. Injections of OTC produced adverse effects and mortality at high treatment rates. A water-soluble form of TC was judged unsatisfactory for injections because of its low pH (2.5). In feeding studies, the palatability of erythromycin-treated feed was poor, but that of OTC- and TC-treated feeds was acceptable. Weight gains (as percent of original weight) for fish offered the erythromycin-treated diet ranged from 144.7% at the recommended therapeutic concentration to 111.6% at five times the recommen...

Efficacy and Toxicity of Formalin Solutions Containing Paraformaldehyde for Fish and Egg Treatments

Abstract Formalin used for fish and egg treatments at hatcheries often develops a white precipitate called paraformaldehyde when stored at low temperatures. This presents a problem for hatchery managers because most of the literature and treatment procedures claim that formalin containing paraformaldehyde is more toxic than pure formalin and is not safe for fish or egg treatments. Acute toxicity tests with rainbow trout (Oncorhynchus mykiss) and channel catfish (Ictalurus punctatus) showed that the toxicity of formalin solutions containing a moderate amount of fine paraformaldehyde was similar to that of pure formalin. In efficacy tests on fish eggs, the bottom fraction of a formalin solution containing paraformaldehyde and a sample from the clear top fraction were equally effective in controlling fungal infection on rainbow trout eggs and caused no treatment-related mortality. Chemical assays found on average a 3% difference in formaldehyde concentration between top and bottom fractions of a formalin sol...

Communications: Removal of Benzocaine from Water by Filtration with Activated Carbon

Abstract Benzocaine is a promising candidate for registration with the U.S. Food and Drug Administration for use as an anesthetic in fish culture, management, and research. A method for the removal of benzocaine from hatchery effluents could speed registration of this drug by eliminating requirements for data on its residues, tolerances, detoxification, and environmental hazards. Carbon filtration effectively removes many organic compounds from water. This study tested the effectiveness of three types of activated carbon for removing benzocaine from water by column filtration under controlled laboratory conditions. An adsorptive capacity was calculated for each type of activated carbon. Filtrasorb 400 (12 × 40 mesh; U.S. standard sieve series) showed the greatest capacity for benzocaine adsorption (76.12 mg benzocaine/g carbon); Filtrasorb 300 (8 × 30 mesh) ranked next (31.93 mg/g); and Filtrasorb 816 (8 × 16 mesh) adsorbed the least (1.0 mg/g). Increased adsorptive capacity was associated with smaller ca...