Before a key to any group can be developed, it is necessary to determine the species or taxa that might be encountered in the geographical area. For this reason, the CPIE website includes a listing of freshwater and estuarine species for Hawai‘i:
These lists form the basis for the keys; that is, the keys are an attempt to differentiate betweeen all of the species listed.
The identification of a plant or animal is an undertaking that should not be approached casually. Differences between closely related species are often quite subtle, and proper identification usually requires some or all of the following:
Many people who may be only amateur naturalists, do train themselves to make accurate field identifications of plants and animals, based on a combination of anatomical structures (field charateristics), knowledge of habitat requirements, and familiarity with what could be present in a given situation. This is not the same as making a careful identification in the laboratory with a series of specimens, access to the literature, and perhaps preserved specimens identified by an expert for comparison. Yet for both teaching and environmental surveying, it is important to make accurate and informed identifications of plants and animals, sometimes in the field without later reference to collected specimens. Without making a collection, or at least conducting a close examination, it is often impossible to determine the exact species at hand in some groups. A knowledge of the potential choices is then necessary to determine what the observed organism might well be, and whether the identification can proceed further than the genus, or the family group, or only to some higher taxon. These keys are being developed to provide the user with a sense of the mimimum amount of information that might be necessary to make an accurate identification. Where determinations can utilize basic characteristics such as size, or shape, or color, these are incorporated. Where accurate identification requires close examination of minute anatomical structures to separate taxa, this information is included in the key.
The greatest advantage to providing these keys on the Internet as opposed to printing them, is that their utility can be continuously improved. We hope to expand the keys and alter the descriptions as we and others experience using them. Any coments would be greatly appreciated and should be emailed to Eric Guinther at AECOS, Inc., 45-939 Kamehameha Highway, Suite 104, Kane‘ohe 96744.
These keys are limited to aquatic organisms found in non-marine environments, usually fresh or brackish waters. However, the latter can present special problems because many species thought of as marine organisms enter estuaries or confined saline environments (e.g., anchialine pools and hyperhaline waters). Because the number of marine species in some groups is large, the key cannot include all these possibilities. A similar dilemna exists with respect to terrestrial organisms, many of which visit aquatic environments or are aquatic for only part of their life-cycle. Other terrestrial species are regular inhabitants along shorelines or wet areas, but are not aquatic in any other sense (grouse locust, for example). The fact that aquatic ecosystems and associated organisms are not always clearly distinct from terrestrial ones (or marine waters are not always distinct from freshwaters) may lead to uncertainty when trying to use the keys for organisms collected in environments transitional between water and land, or between ocean and stream. Eventually, most of these "associated" species will be included in the keys if regularly encountered around aquatic environments as defined above.
Identification of organisms always rests heavily on a past body of information contained in published (and some cases, unpublished) reports and documents usually prepared by experts in specific groups of organisms. Rather than burden each part of our key with a listing of the references consulted, outside sources consulted in developing the keys is provided in the BIBLIOGRAPHY page at the end of the document.
You may already be familiar with how a dichotomous key works. For those students or others who are not, I can offer the following orientation. Otherwise, you may skip ahead to information on the specific format adopted for the dichotomous keys presented here—or start at the key's INDEX Page (most useful to focus on a key to a specific group of organisms) or at COUPLET 1 following (page ii).