stress exerted upon a diverse biological cotmiunity results in a reduction in 

 species diversity (Cairns 1969). 



Species-diversity indices (d) have been used by biologists to provide 

 insight into the structure of natural conmunities and as indicators of 

 qualitative aspects of their environments. A low diversity index indicates 

 a largely monotypic conmunity dominated by a few abundant species, and a high 

 diversity index suggests a heterogeneous community in which abundance is dis- 

 tributed more evenly among a number of species. Redundancy (R) (see Report 

 No. 5 in this series), also used as an index of the repetition of information 

 within a community, expresses the dominance of one or more species and is 

 inversely proportional to the abundance of the species (Wilhm and Dorris 1958). 



While species-diversity indices have been used extensively with benthic 

 macroinvertebrates to evaluate degradational environmental conditions, they 

 have only recently been applied to fish populations (Sheldon 1963, Jackson 

 and Harp 1973, and Harima and Mundy 1974). Shannon-Weaver diversity indices 

 were calculated for the fall 1975 sample and combined sample of fall 1974 

 and fall 1975 (figure 4). The fall 1974 sample diversities were also plotted 

 for comparison, but sections Ilia and Vb were omitted because they were not 

 sampled in 1975. With the inclusion of more data, the diversity indices 

 theoretically tend to the true population diversity, assuming no drastic change 

 over time. All fish under 152 mm (6 in) were excluded from the sample to 

 eliminate human sampling bias (the selection of the bigger fish when a choice 

 occurs in sampling). Figure 5 shows the linear regressions between diversity 

 indices (dependent variable) and the section (independent variable). Study 

 section diversity indices increased with proximity to the river's mouth. 

 In section Vc the index rise from 1974 to 1975 was attributed to a change in 

 the number of fish/km (143 to 181) and a gain in the number of species (11 to 

 15). The probable reasons for these gains are two-fold: 1) prolonged high 

 releases from the reservoir in 1975 are not characteristic of past flows and 

 favor those species better adopted to fast-water habitats (mountain sucker 

 and smallmouth bass); 2) inspections and drawdowns of the dam may have 

 influenced the distribution patterns. The remaining sections had little 

 change. 



Tongue River diversities are similar in magnitude to those calculated 

 for Rosebud Creek by Elser and Schreiber (1977). However, those on the 

 Tongue River tended to be higher, ranging from 1.8 to 2.9, as compared to a 

 range of 1.2 to 2.7 on Rosebud Creek. 



SHOVELNOSE STURGEON 



The shovel nose sturgeon (Scaphirhynchus platorynchus) is common in 

 portions of the Mississippi, Missouri, and Ohio river drainages. Its distri- 

 bution in the Missouri River has been limited by the construction of mainstem 

 reservoirs (Held 1969). In Montana, the shovelnose is abundant in the 

 mainstem of the Missouri below Great Falls and common in most of the larger 

 primary and some secondary tributaries of this river (Brown 1971). Shovel- 

 nose are abundant in the Yellowstone River downstream from the Carters ville 

 Diversion at Forsyth (Peterman and Haddix 1975). Anglers seek the 



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