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BULLETIN OF BUREAU OF FISHERIES 
under which headings a large percent of the pollution cases may be classified, the 
possibility of cumulative effects must be considered when determining remedial 
measures or dilutions. Cumulative effects from very low concentrations of some 
substances which seem harmless to fish life over a period of 10 to 14 days present 
difficult problems. Some of these are discussed in subsequent portions of this section. 
TEST ANIMALS 
In the course of the work on the lethality of stream pollutants 30 species of fresh- 
water animals (see table 6), including 17 species of fish, 6 species of crustaceans, and 
7 species of fresh-water mussels, have been used in one connection or another as test 
animals. 
Table 6. — Species of test animals 
Species 
Common name 
Species 
Common name 
FISH 
1. Perea flavescem 
2. Micropterus salmoides ... _ 
3. Lepomis incisor ... ... 
4. Lepomis humilis. . .. 
5. Ameiurus n ebviosas 
Yellow perch. 
Largemouth black bass. 
Blue gill. 
Orange-spotted sunfish. 
Common bullhead. 
Channel cat. 
AMPHIPOD8 
18. Gammarus fasciatus 
19. Eucrangonyx gracilis 
ENTOMOSTRACANS 
20. Daphnia magna 
21. Bosmina sp.- 
Gammarid. 
Do. 
Daphnia. 
Long-nosed dace. 
Dace minnow. 
22. Cypris sp _ _ _ 
8. Leuciscus balteatus 
23. Cyclops sp._ 
Copepod. 
9. Notemigonus chrysoleucas 
10. Notropis delicious ... . 
11. Hybognathus nuchalis 
Golden shiner. 
Straw-colored minnow. 
Silverv minnow. 
FRESH-WATER MUSSELS 
24. Tritogonia verrucosa 
Buckhorn. 
12. Pimephates promelas . . 
Fathead minnow. 
25. Megalonaias gigantae 
Washboard. 
13. Cyprinus carpio 
German carp. 
26. Quadrula trapezoides . 
Small washboard. 
Common goldfish. 
Rainbow trout. 
27. Fusconaia undata _ _ 
Pigtoe. 
River mucket. 
28. Actinonaias carinata ... 
Cut-throat trout. 
29. Lampsilis anodontoides . 
Yellow sand-shell 
17. Lepisosteus platostomus _ . . . 
Short-nosed gar. 
30. Lampsilis siliquoidea 
Fat mucket. 
From these studies and from the voluminous literature of bioassay methods 
and physiological and pharmacological experiments in which these and many other 
forms of aquatic life have been used as bioreagents, two animals — the common 
goldfish, Carassius auratus. and the entomostracan, Daphnia magna — were selected 
for the standard tests. This procedure, i. e., the use of standard test animals, is 
recognized in other fields of biological investigation in which the frog, the rat, and 
the guinea pig have established positions as assay animals, and makes possible 
direct comparisons of data on the actions of a variety of substances over a wide 
range of conditions. No single test animal combines all of the desirable qualities 
and in making a choice both availability and physiological suitability for the prob- 
lem in hand must be considered. As the variety of aquatic animals which may be 
affected by stream pollution is large, a lethality range for each pollutant and effluent 
must be established, as the specific sensitivities of various aquatic species are not 
the same, although they may live in the same aquatic complex. However, if the 
pollutant destroys any one of the major species in the complex, the entire fauna in 
that part of the stream may suffer as a result. The selection of goldfish and daphnia 
gave a combination by which the maximal and minimal limits of toxicity of any 
given pollutant for different stream complexes could be ascertained rapidly and with 
reasonable accuracy. 
