Effects of Invasive Tissue Collection on Rainbow Trout, Razorback Sucker, and Bonytail Chub

Abstract

Histological examination and biochemical assays of fish tissues are used for disease detection, genetic characterizations, contaminant analyses, and the detection of stable isotopes. However, tissue sampling usually requires invasive sampling procedures that may harm or kill an organism under investigation. For this reason, invasive procedures are rarely used with threatened, endangered, or other sensitive species. If invasive tissue sampling could be performed with little harm, a wide array of sophisticated techniques could be employed to assist in protection and management of species in decline. We subjected rainbow trout Oncorhynchus mykiss to nonlethal invasive sampling of fin, muscle, and liver tissue. Techniques first developed for trout were applied to two endangered fishes, razorback sucker Xyrauchen texanus and bonytail chub Gila elegans. Acute (mortality) and chronic (suppression of growth rate) effects of tissue removal were evaluated in a hatchery for control and treatment groups of experimental fishes. No mortality was attributable to tissue sampling in any of the three species, and there were no significant differences in growth rates between control and treatment groups in rainbow trout or razorback sucker. Bonytail chub experienced high mortality due to an outbreak of disease that precluded an evaluation of chronic effects, but there was no indication that survivorship was decreased due to tissue sampling. With recent advances in use of small tissue samples, these nonlethal invasive methods can make a variety of tissues available for histological evaluation, genetic characterization, or biochemical assay without sacrifice of valuable fish.