Ichthyology is commonly defined as 'the study of fish' or 'that branch of zoology dealing with fish'. A fish is, literally, a vertebrate (i.e., animal with a backbone) that has gills, a body covered with scales, and lives in the water. However, some species are well known for their ability to leap clear of the sea surface and glide long distances using their fins as wings. In addition, other species can live out of the water for quite sometime, walk to migrate to other water bodies using auxiliary breathing organs, and some species do not have bodies covered with scales. Also, the word fish is sometime used more broadly to include any edible animal living in water. Here, we limit ourselves to fish in the narrow sense; note that the term 'fishes' refers to more than one type (or species) of fish; 'finfish' refers to sharks, some rays and bony fishes, and 'scalefish' refers to fish bearing scales (see Glossary).
Ichthyology has a long documented history, dating thousands of years back to the ancient Egyptians, Indians, Chinese, Greeks and Romans (Cuvier 1828). This long, sustained interest in fish is due to their double role as highly speciose denizens of a fascinating, yet alien world and as human food since many thousands of years ago. It has generated, over the centuries, highly heterogeneous information – mainly taxonomic, but also referring to zoogeography, behavior, food, predators, environmental tolerances, etc.
This huge amount of information, embodied in a widely scattered literature, has gradually forced ichthyologists to specialize. Thus accounts on fish are now either global, but highly specialized (e.g. Eschmeyer's Catalog of fishes (1998) or Pietsch and Grobecker's Frogfishes of the world (1987) to name two outstanding representatives), or local and deep (e.g. Fryer and Iles' Cichlid Fishes of the Great Lakes of Africa (1972) or Groot and Margolis' Pacific Salmon Life Histories (1991).
Thus, with a few exceptions such as the massive Diversity of fishes (Helfman et al. 1997), texts are lacking which bring together, on a global basis, all aspects of ichthyology, such that they can be used for a specialized course, and/or independent learning.
FishBase is an information system available on-line at www.fishbase.org, covering all fishes of the world in a fashion that is both global and deep. FishBase, whose accompanying book is available in English, French and Portuguese, covers over 30,600 species of fish, i.e., most of the extant species in the world, and addresses the needs of a vast array of potential users, ranging from ichthyologists, fisheries biologists, ecologists and managers to biology teachers, administrators and the public at large. The features of FishBase that enable it to meet such a wide range of needs reside in its architecture, which makes extensive use of modern relational database techniques.
Other features of FishBase are:
• all information on a given species in the database is accessible through a unique scientific or common name or through common names in many languages;
• the wide use of multiple choice field structures standardized qualitative information;
• numeric fields record quantitative information that has been previously standardized;
• numerous cross-relationships between data tables enable previously unknown relationships to be discovered; and
• complementary databases provided by colleagues and linked to FishBase proper contribute to making the combined package the most comprehensive data source of its kind.
For teachers of aquatic biology, or of specialized ichthyology courses, the uses of FishBase will range from practical solutions to theoretical issues:
• FishBase is directly useable as data source (i.e., as an electronic encyclopedia on fish), thus complementing classical sources of information on fish, e.g., the Zoological Record or Aquatic Science and Fisheries Abstracts, and thus helps overcome the lack of scientific literature, especially in developing countries;
• the many pictures in FishBase can be used, just as those in taxonomic books, to provide students with a visual impression of the morphological and color diversity of fish, and/or of specific features of various groups;
• students will be able to assess the state of knowledge on various groups of fish, and thus obtain some guidance in identifying worthwhile projects; and
• the synoptical view that FishBase produces by assembling and structuring all available information on one species will help students to obtain material for study (see above) and, perhaps more importantly, to develop a sense of how scattered bits of information can be used to 'reconstruct' species, and to show how these fit into their environments. In other words, FishBase transforms information to knowledge and thus encourages a holistic view, as now required for most of what we do in the biological sciences.
Thus, a series of lectures on ichthyology may be conceived, based on the following elements:
• show FishBase pictures through an introductory lecture, to highlight the diversity and colorfulness of fish and similarity of external morphology in related groups (this hopefully would serve to generate interest in the course as a whole, and introduce fish classification);
• compare the early classification schemes in Cuvier (1828) with a recent one, e.g., that in the Catalog of Fishes (Eschmeyer 1998), 'hosted' by FishBase and largely identical with the widely used classification in Nelson (1994);
• introduce the species concept and its requirements (a formal description with figures, a binomen, a holotype, a type locality, etc.) and implications (synonymies, sister species, etc.), using FishBase as source of examples, and its Glossary for definition of terms;
• define the characteristics (meristics, morphometrics) through which fish species are usually defined and hence identified, and compare identification through keys with computer-based identification using the appropriate FishBase routine (see 'Quick Identification');
• show how museum and other occurrence records, as included in FishBase, can be used to define distribution ranges and habitats, which can then be used for answering high-order ecological questions;
• show how the latitudinal ranges of fish species can be used to test various hypotheses, e.g., on the relationship between fish biodiversity and shelf area (for neritic species) or land area (for freshwater species);
• define and illustrate various life history strategies, and analyze their frequency distribution throughout the world. Show, e.g., that salmon-type anadromy is extremely rare in subtropical or tropical species (it is well documented only in hilsa, Tenualosa ilisha, ranging from Iraq to Myanmar). Show how students can identify the relative frequencies of different strategies and draw inferences from these;
• let each student select a species, print out the relevant FishBase summary page and try to complement missing (black) items in the 'More Information' section, based on a literature review (and send the result to the FishBase Team); and
• show or let students derive quantitative relationships between different expressions of fish physiology (e.g., respiration, growth) and temperature (and hence latitude) and identify modifying factors (salinity, gill size, food type, etc.).
In the context of higher education, FishBase may also serve as background for Bachelor's or Master's theses, where data coverage of certain topics would first be checked and completed, and then data-mining techniques would be used to test relevant hypotheses.