Geographic Scope

The geographic extent of the project is defined as the political area of Texas including the barrier islands and bays. Fish occurrence records from Texas and its boundary rivers were requested from donor institutions around the world. However the database also contains numerous other marine and freshwater species records from the Gulf of Mexico, inland Mexico, and neighboring US states (New Mexico, Oklahoma, Arkansas and Louisiana), which were received from donor institutions along with Texas records. However, there was no systematic attempt to acquire these extraneous data and since we did not georeference these non-Texas records and their fields are not all fully normalized, they are not available for mapping nor will they be retrieved in queries using fields derived from GIS. At this time these records can only be reliably retrieved by queries of verbatim donor fields. We are actively seeking support to allow us to normalize and georeference nearby non-Texas and marine records and we would eventually like to include records from all out-of-state areas of Texas' river basins (i.e. the Oklahoma portion of the Red and the Louisiana portion of the Sabine).

Taxonomic Scope

We limit the taxonomic scope of the project to fishes as defined by those taxa accepted by the American Fisheries Society (Nelson, 2004), which includes Leptocardii. See our Taxonomy page for a complete and current list of taxa included in the project.

Temporal Scope

We requested records from institutional donors regardless of date and include all records received including those without a date recorded. We do not maintain data on time of day of collection, but in some rare instances such data may be found in verbatim donor data.

Data Sources

All data in this project are "vouchered" by preserved specimens stored in museum collections. These data are the highest quality occurrence data available since they can be verified at any time by inspection of specimens that will persist indefinitely. Other data sources without vouchers are unverifiable. The ability to verify determinations is critical and our recent work towards correcting errors of determination in the Fishes of Texas Database illustrates the importance of museum specimens. Additionally, data backed by specimens are useful since those specimens can then be used for research in many fields of biological study.

Museum specimens are critically important for researching many aspects of ecology, evolution, biogeography, natural history, and biology in general. Specimens document a snapshot of the environment from which they came since they contain gut contents and parasites and their tissues hold chemical clues about many aspects of their environment. Museum specimens are also potentially very long-lived (many centuries at least) and signals of past environments preserved in them can be studied as long as the specimens persist. Specimens included in this database were collected as far back as the mid-1800s and are almost always in acceptable condition for identification.

The only way to verify anyone’s determination of a species’ identification is by examination of a specimen, and if one does not exist, questions will always remain. We thus chose to focus exclusively on museum specimen-vouchered data as a means to reconstructing the historic record. Our work on this project clearly demonstrates that fish identification errors are common. At the time of this writing, over half of our flagged (as geographic outliers) records had erroneous identifications, but we have found large error rates among species within their known ranges as well and believe all determinations should be seriously questioned.

In many cases specimens are identified incorrectly at the time of deposition in a museum, but in some instances errors are “created” by the progress of science since species are often divided by taxonomists into two or more new species. The original species names remain in museum databases and labels, but now with incorrect determinations. Museum curated specimens allow researchers to determine the historic distribution of newly split species, provided that determinations can be based on preserved morphology.

Many publications and reports, as well as a variety of other databases (e.g. Texas Parks and Wildlife Fisheries Surveys) provide occurrence records for freshwater fishes, which are certainly useful in some contexts. However, those records are often not supported by specimens that can be re-examined for independent verification of reported species determinations. Furthermore, such sources are often not spatially or temporally explicit regarding occurrences and omit details that are important for many types of analyses. Despite the limitations of unvouchered data, they are potentially valuable and we intend to include them in the database eventually.