These keys have been reproduced from the book Fishes in Kansas, Second Edition, Revised by Frank B. Cross & Joseph T. Collins. Original artwork from the book has been included thanks to Joseph R. Tomelleri.

HOW TO USE THE KEYS

A key consists of a sequence of numbered couplets (paired, contrasting statements). Both parts of each couplet should be read carefully before deciding which of the two statements better describes the fish at hand. Use of these keys starts with couplet number 1 under the Key to the Families of Fishes in Kansas. Before you begin, read the next three numbered paragraphs, which explain how a key is used:

1. If your fish lacks jaws, has a mouth that resembles a suction cup, and has a line of seven gill-pits rather than a single slotlike gill-opening, you are fortunate to have found a Chestnut Lamprey (Family Petromyzontidae), and you may turn to the species account for further information about it. If, on the other hand, your specimen does have jaws and a single gill-opening, continue your use of the key by proceeding to couplet number 2.

2. Read both alternatives in couplet 2. If you conclude that the caudal fin of your fish is symmetrical and has a vertical base (homocercal; Fig. 2), go to couplet number 6 (otherwise, go to couplet 3).

3. In couplet 6, if the first statement accurately describes your specimen, it is an American Eel. If the second statement better fits the fish at hand, proceed to couplet number 7, and continue as before until a specific (or family) identification can be obtained. Often, identification requires use of a second set of keys, to the kinds of fishes within families that are represented by more than one species in Kansas.

It is essential, when using these keys, to have a minimum number of instruments and tools available. Most important is the need for a dissecting (binocular) microscope. Also have at hand a pair of small dissecting scissors, a fine probe, a pair of forceps, a ruler, and a pair of calipers or engineer's dividers. In addition, be sure to consult the figures and glossary to ensure that you understand the language used in the keys.

As a precautionary measure, you should check the characteristics of several individual fish that you believe to be alike, while utilizing these keys (and specifically Figures 1 to 45) to identify them. Most kinds offish have a wide range of individual variation, as is implied by the range in scale count or fin ray count that is cited in each half of many couplets. The range of variation given is inclusive of most (but not necessarily all) individuals of a species; therefore, failure of a specimen to "fit the key," or misidentification of the specimen, may result from unusual features of that specimen relative to others of its kind. Examination of several specimens (if available) will minimize this problem. Users of this key may encounter particular difficulty in identifying minnows (Family Cyprinidae), suckers (Family Catostomidae), and darters (Family Percidae).

Some difficulties encountered in identifying particular fish reflect unusual but still "normal" characteristics of the species. Nevertheless, users of this book should remember that knowledge of our fish fauna is incomplete. Additional species are likely to be found within the state, and extensions of the known distributions of other species are certain. Therefore, "unidentifiable" specimens command real interest, as do specimens caught outside the areas of known occurrence as given in the species accounts. Such specimens should be taken to the University of Kansas Ichthyology Division, or regional office of the Kansas Department of Wildlife and Parks for verification.