Morphology and Physiology


The word ‘morphology’ refers both to the branch of biology dealing with the form and structure of organs or other parts of organisms, and with the form and structure of organism as a whole.

Similarly, the MORPHOLOGY table of FishBase aims to fulfill two related goals:

  1. to provide standardized and thus comparable, concise descriptions of the fishes included in FishBase; and

  2. to allow for quick species identification based on characters used in (i).

In fish, the major characters used for description and identification are descriptive, referring to distinguishable characters (e.g., shape of caudal fin), morphometric, referring to continuous variables (e.g., head length as a fraction of body length) or meristic, referring to discontinuous variables (e.g., the number of rays and spines in a dorsal fin).

Meristic, morphometric and descriptive characters identify a species

The MORPHOLOGY table incorporates descriptive characters in multiple choice fields and morphometric and meristic characters in numeric fields. It is mainly the meristic characters that are used for quick identification, following the database identification scheme of Froese and Papasissi (1990). The structure of the MORPHOLOGY table and the choice of fields it includes are based on a close study of major texts in ichthyology (e.g., Lagler et al. 1977) and consultation with numerous colleagues. Some of the terms employed in the table are highly specialized; their definition may be found in the FishBase Glossary.


The MORPHOLOGY table contains 67 choice fields, 79 numeric fields and several remarks fields. Choice fields present the user with preprogrammed choices of descriptions for a body part or feature (e.g., Cross section - circular; oval; compressed; flattened; angular; others (see Remarks)). The choices included were kept to a minimum, including only general descriptions covering the most common shapes or forms. In most cases, an ‘Other (see Remarks)’ choice is included for those species which might have aberrant features or shape of a body part. When ‘Other’ is chosen for a field, a detailed description of the particular body part is included in the Remarks field.

Numeric fields on the other hand, were used for morphometrics and meristics. In most cases, ranges were entered in separate lower and upper limit fields. When a range or several values are given in the literature, but the field allows only a single number to be entered (as in the fields for body proportions), the mean of the available values was entered.

The Remarks field accommodates characters that are either not included in the choice fields or require more detailed descriptions. In these fields, distinctive features, and how these features might be found in closely related species, are highlighted. Notes on color variations (ontogenetic, sexual and geographic) are also entered in this field, when available.

As the number of species in FishBase increased, we found it too time-consuming to fill the more than 140 fields of the MORPHOLOGY table for all species. We decided to reduce the number of ‘active’ fields to those regularly covered in taxonomic books (standard meristics and diagnosis) and to fill these on a regular basis. This has meanwhile been completed for all bony fish of Japan and British Columbia, and for all marine fishes of Micronesia and of Southern Africa (Smith and Heemstra 1986). Also, all families covered by FAO catalogues or in Randall’s Indo-Pacific Fishes series are complete. We plan to complete and verify the MORPHOLOGY table by family (see Box 1, this vol.) and by using major faunal works such as Skelton’s (1993) Freshwater Fishes of Southern Africa.


One important use for the information contained in the MORPHOLOGY table is for quick fish identification (see ‘Quick Identification’, this vol.). The current preprogrammed routine requires a minimum amount of information as search criteria, viz.:

The data in the MORPHOLOGY table can be used for quick identification
  • FAO area from which the fish was collected;

  • habitat (freshwater, brackish, saltwater);

  • depth at which the fish was collected;

  • size of the specimen;

  • number of dorsal fin spines;

  • number of dorsal fin soft rays;

  • number of anal fin spines;

  • number of anal fin soft rays;

  • order or family (optional).

A search typically results in less than 10 possible species

The routine searches through the database and displays the list of species that matches the user-provided criteria. Typically, such a search results in less than 10 species of the same family. The user then can go through the pictures and through the full morphologic description to verify an identification. This search routine works also if one or more of the fields are left empty. In such cases, the list of species thus generated becomes longer. Note, however, that to date, the MORPHOLOGY table contains data for only about 8,000 species and is complete for only a few areas or families (see above). The information provided varies in degree of completeness, from very scanty, as in the case of Pellona castelnaeana, to almost complete, as in the case of Lutjanus biguttatus. Also, the data have not been thoroughly checked, and thus may contain errors.


Preprogrammed routines for printing Species Synopses and Summaries make use of information in the MORPHOLOGY table. The routine for printing a synopsis for one species, for example, extracts the Additional Characters field which gives distinctive descriptions, the dorsal and anal fin element counts, and other information from the SPECIES and STOCKS tables. It then prints out a comprehensive report of the information available for that species, plus all the references used (see ‘Reports’, this vol.).


Data in the MORPHOLOGY table stem from all FAO Species Catalogues published so far, other taxonomic revisions, faunal books and journal articles, e.g., Burgess (1978), Trewavas (1983), Allen (1985), Cohen et al. (1990), Lévêque (1990), Randall et al. (1990), Allen (1991), Myers (1991), and Heemstra and Randall (1993).

How to get there

You get to the MORPHOLOGY table by selecting a species, then clicking on the Biology button in the SPECIES window, the Morphology and Physiology button in the BIOLOGY window, and the Morphology button in the next window. You get to the Quick Identification routine by clicking on the Species button in the Main Menu window and the Quick Identification button in the SEARCH BY..... window. The internal name of this is MORPHDAT.


On the Internet, you get to the MORPHOLOGY table by clicking on the Morphology link in the ‘More information’ section of the ‘Species Summary’ page. You can create a list of species with available data by selecting the Morphology radio button in the ‘Information by Topic’ section of the ‘Search FishBase’ page.


Allen, G.R. 1985. FAO species catalogue. Vol. 6. Snappers of the world. An annotated and illustrated catalogue of lutjanid species known to date. FAO Fish. Synop. 6(125):208 p.

Allen, G.R. 1991. Damselfishes of the world. Mergus Publishers, Melle, Germany. 271 p.

Burgess, W.E. 1978. Butterflyfishes of the world. A monograph of the Family Chaetodontidae. T.F.H. Publications, Neptune City. 832 p.

Cohen, D.M., T. Inada, T. Iwamoto and N. Scialabba. 1990. FAO species catalogue. Gadiform fishes of the world (Order Gadiformes). An annotated and illustrated catalogue of cods, hakes, grenadiers and other gadiform fishes known to date. FAO Fish. Synop. 10(125):442 p.

Froese, R., and C. Papasissi. 1990. The use of modern relational databases for identification of fish larvae. J. Appl. Ichthyol. 6: 37-45.

Heemstra, P.C. and J.E. Randall. 1993. FAO species catalogue. Vol. 16. Groupers of the world. (Family Serranidae, Subfamily Epinephelinae). An annotated and illustrated catalogue of the grouper, rockcod, hind, coral grouper and lyretail species known to date. FAO Fisheries Synop. 16(125), 382 p.

Lagler, K.F., J.E. Bardach, R.R. Miller, and D.R. May-Passino. 1977. Ichthyology. 2nd ed. John Wiley and Sons, New York. 506 p.

Lévêque, C. 1990. Cyprinidae, p. 269-361. In C. Lévêque, D. Paugy and G.G. Teugels (eds.) Faune des poissons d'eaux douces et saumâtres d'Afrique de l'Ouest. Tome I. Coll. Faune Tropicale n° XXVIII. Musée Royal de l'Afrique Centrale, Tervuren, and O.R.S.T.O.M., Paris. 384 p.

Myers, R.F. 1991. Micronesian reef fishes. 2nd ed.. Coral Graphics, Barrigada, Guam. 298 p.

Randall, J.E., G.R. Allen and R.C. Steene. 1990. Fishes of the Great Barrier Reef and Coral Sea. University of Hawaii Press, Honolulu, Hawaii. 506 p.

Skelton, P.H. 1993. A complete guide to the freshwater fishes of Southern Africa. Southern Book Publishers, South Africa. 388 p.

Smith, M.M. and P.C. Heemstra, Editors. 1986. Smith’s sea fishes. Springer Verlag, Berlin. 1047 p.

Trewavas, E. 1983. Tilapiine fishes of the Genera Sarotherodon, Oreochromis and Danakilia. British Museum of Natural History, London. 583 p.

Rainer Froese and Rodolfo B. Reyes, Jr.