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USE OF KEYS <br />Many readers may not be familiar with <br />the use of identification keys. The keys in <br />this book are arranged in a series of coup- <br />lets. Each couplet is composed of two <br />statements. For example, the first couplet <br />has two parts La. and Lb. When identify- <br />ing an unknown fish, begin with the first <br />couplet. Read the statements and decide <br />which of the two best describes the fish <br />in question. Follow the instruction follow- <br />ing the statement which best describes <br />the fish. The instruction will direct the <br />reader to another couplet. Read that <br />couplet and decide again which statement <br />describes the fish. Follow the instructions <br />from couplet to couplet until the name of <br />a family of fish is listed after the statement <br />describing the unknown fish. This tells <br />KEY TO THE FAMILIES OF FISH IN COLORADO <br />What follows is a taxonomic key. To use <br />this key, take the fish in question and read <br />the first two descriptive phrases, couplet <br />La. and Lb. One of these two phrases will <br />describe a character which fits the fish <br />you are trying to identify. Decide which <br />character fits the fish in question and read <br />the instruction which follows the descrip- <br />tive phrase. The instruction will either tell <br />you what family the fish is or tell you to <br />go to another couplet. If the key is fol- <br />lowed correctly, matching the fish to vari- <br />ous characters, the reader will eventually <br />reach a "Dead-end" which identifies the <br />fish. Occasionally an unfamiliar term may <br />be encountered when using this key. The <br />preceeding section explains fish anatomy, <br />defines terms and should provide proper <br />explanation for all unfamiliarities. Read- <br />ing a detailed description of each species <br />and examining the various drawings and <br />photographs will allow the reader to deter- <br />mine if a correct identification has been <br />made. <br />1. a. Pectoral fins are absent. <br />Family ANGUILLIDAE <br />Freshwater eels <br />Not described in this book <br />(See Beckman 1952) <br />b. Pectoral Fins present. <br />Go to Number 2. <br />2. a. Adipose fin present. <br />Go to Number 3. <br />b. Adipose fin absent <br />Go to Number 5. <br />3. a. Barbels present on chin and above <br />dorsal lip. <br />Family ICTALURIDAE <br />Catfish. See page 13. <br />b. No barbels present on chin or <br />above dorsal lip. <br />Go to Number 4. <br />4. a. Pyloric caeca numerous and well <br />developed. Pelvic axillary process <br />present. If there are more than 100 <br />lateral line scales teeth are well <br />developed. If there are less than <br />100 lateral line scales the mouth <br />is small with the maxillary not ex- <br />tending past middle of the eye and <br />teeth are weak or absent. <br />Family SALMONIDAE <br />Trout, grayling and whitefish <br />Not covered in this book. <br />(See Woodling 1980). <br />b. Pyloric caeca absent or few in <br />number and not well developed. <br />No pelvic axillary process. Less <br />than 80 lateral line scales, while <br />mouth is large, with maxillary ex- <br />tending past middle of eye and <br />well developed teeth. <br />Family OSMERIDAE <br />Rainbow smelt. See page 14. <br />you to which family the fish belongs. For <br />minnows, suckers and some other fami- <br />lies, an instruction will direct you to <br />another key in the book dealing with that <br />family. Follow this process until the fish <br />is described to species. Before ending the <br />identification process, examine the photo- <br />graphs, distribution map and description <br />to make sure your identification is correct. <br />5. a. Front portion of dorsal fin has four <br />to six stiff dorsal spines not con- <br />nected by a continuous mem- <br />brane. Each spine has a small in- <br />dividual membrane. No scales on <br />body. <br />Family GASTEROSTEIDAE <br />Brook stickleback. <br />See page 15. <br />b. Dorsal fin may or may not have <br />stiff spines. If spines are present a <br />continuous membrane connects <br />the spines. <br />Go to Number 6. <br />6. a. One dorsal fin, usually without <br />spines, though there may be one <br />(and only one) stout spine at the <br />anterior (head) edge of dorsal fin. <br />This single spine, if present, ser- <br />rated along posterior edge. <br />Go to Number 7. <br />b. Two dorsal fins either well- <br />separated, or united into one dor- <br />sal fin. If one dorsal fin then there <br />are more than four spines at <br />anterior edge of dorsal fin. <br />Go to Number 13. <br />a. Single dorsal fin with one spine. <br />Goldfish and Carp. <br />Family CYPRINIDAE (in part). <br />Minnows. See page 17. <br />b. Single dorsal fin without any <br />spines. <br />Go to Number 8. <br />11 Colorado's Little Fish