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MANAGEMENT BRIEFS 851 \ jected to surgery, the tag was injected into the body cavity with a hypodermic syringe inserted about 5 mm posterior to the right pelvic fin, Thereafter, each individual was identified by reading the 10- character alphanumeric code with an electronic scanner. After the rainbow trout study began, it was de- cided that a muscle or muscle and fin sample would probably be selected by USFWS as the least in- vasive method that would provide adequate tissue samples for genetic analysis, In addition, liver samples, although obtained by the most invasive procedure, would be evaluated as the best tissue to facilitate sampling for contaminants or other assays. Because results from the pilot study with rainbow trout were so encouraging, treatments were altered somewhat for the endangered fishes, The T2 treatment, which was assessment of an- esthesia only in rainbow trout, was eliminated and replaced by incision and suturing but not tissue removal, which was T3 in rainbow trout The four remaining treatments involved removal of tissue in various combinations: liver only (T3), pelvic fin and dorsal musculature (T4), muscle only (T5), and muscle and liver (T6), Bony tail chub experiments were started on 9 August 1990; fish were inspected, weighed and measured on 10 December 1990, 22 March 1991, and 7 February 1992, Razorback sucker experi- ments were started on 4 and 5 September 1990; fish were inspected, weighed, and measured on 11 December 1990, 21 March 1991, and 7 February 1992, On the final date, 17 razorback suckers and 7 bony tail chub were sacrificed and preserved for further study, Data analyses,- The length and weight of each fish was measured at the beginning and end of the study, Because the absolute change in length or weight depends, in part, on the size of the fish, an instantaneous rate of growth was used to adjust for the effect of size. Instantaneous growth in length was calculated as follows: G = (lit) X 10geCfinal length/initial length), in which G = growth rate, t = time in years, and length is total length (mm). This equation has been reported previously as the instantaneous rate of increase of mean length (Ricker 1975) and the co- efficient of growth (Everhart and Youngs 1981), Growth rates were calculated for each razorback sucker because the fish were tagged uniquely, Mean growth rates were compared among the six treatments by using the Kruskal- Wallis test, a non- parametric analog of one-way analysis of variance, The null hypothesis was that there were no dif- ferences among groups, Growth rates could not be calculated for each trout because individual fish within treatments were not marked uniquely. Although growth rate could be calculated using the average initial length and the average final length in each treatment, there would be no basis for a statistical comparison of the rates because there would be no estimate of variance, This difficulty was overcome by apply- ing a Monte Carlo approach (Palisade Corporation 1997) that simulates the distribution of growth rate values, Normal distributions were constructed for fish lengths in each treatment at the beginning and the end of the experiment using measured values for means and standard deviations, Growth rate, G, was calculated repeatedly for each treatment by sampling the initial and final length distributions 2,000 times, The simulation creates a distribution for growth rate from which the mean and standard deviation are derived for each treatment Disease-related mortality of bony tail chub greatly reduced sample size for all treatments, and precluded significance tests for differences in growth rates, In this case, the Fisher exact test was used to compare survival in the control group (Tl) with survival in the remaining five treatments, Results Results for rainbow trout and razorback suckers are considered first in terms of acute effects (mor- tality) and then chronic effects (growth suppres- sion), However, an outbreak of the disease ich (Ichthyophthirius multifilis) in the bony tail chub resulted in 77% mortality, and the remaining small sample size precluded further testing for chronic effects, We detected no mortality as a result of tissue removal. One of 72 rainbow trout died after jump- ing out of the raceway, and 3 of 96 razorback suckers died (two in T1 and one in T2), No dif- ference in bony tail chub survivorship was detected between the number of individuals remaining in nonsurgical and surgical groups at the end of the study (Fisher exact test, P = 0,500); thus, there was no evidence to suggest that observed mortality was the result of tissue removal. Rainbow trout (initial means :!:: SD: standard length = 249.4 mm :!:: 18.28 and weight = 246.4 g :!:: 58.32; N = 72) were evaluated for chronic effects for 7 months, By 27 September, about 10 weeks after treatment, all fish subjected to tissue removal were demonstrating signs of rapid heal-