[Reprinted from Publications of the INSTITUTE OF MARINE SCIENCE, Vol. 8, 1962. Institute of Marine Science, Port Aransas, Texas.] Fishes of the Rio Tamesi and Related Coastal Lagoons in East-Central Mexicol REZNEAT M. DARNELL Department of Biology, Marquette University Milwaukee, Wisconsin Contents Page INTRODUCTION 300 HISTORY 302 GEOGRAPHY AND GEOLOGY 304 PRECIPITATION 304 DRAINAGE 306 COLLECTING STATIONS IN THE Rio TAMES1 SYSTEM 309 ANNOTATED LIST OF SPECIES 319 ZOOGEOGRAPHIC DISCUSSION 351 PROVISIONAL CLASSIFICATION OF Rio TAmEsi FISHES BASED ON APPARENT SALINITY TOLERANCE 354 SUMMARY 359 ACKNOWLEDGMENTS 360 LITERATURE CITED 361 Abstract A total of 11,043 specimens of fishes was obtained in 66 collections from the tributaries of the Rio Tamesi and from a coastal lagoon near Tampico. Sixty species of fishes are now recognized from the area, 23 of which are fresh-water forms and 37 of which are considered to be euryhaline. For each species information is given, if available, regarding the following: nomenclature, distribution, salinity relations, general ecology, food habits, and reproduction. The 23 fresh-water species include strictly fresh-water forms (15), sporadic invaders of low salinity water (4), and frequent invaders of low salinity water (4). The 37 euryhaline species include anadromous forms (4), catadromous forms (2), frequent invaders of fresh-water (5), sporadic invaders of fresh-water (9), and marine species which are facultative invaders of low salinity water (17). Twelve of the species are considered to be endemic in the Panuco-Tamesi system, all of which are strictly fresh-water forms. For both the fresh-water fishes and the littoral marine fishes, eastern Mexico represents a zone of transition between the temperate and tropical faunas. Among the fresh-water species of the Tamesi, representatives of southern families slightly outnumber representatives of northern families (13:10). Among the euryhaline species, representatives of southern families greatly predominate over those of northern families (35:2). Analysis of habitat distribution of the fresh-water fishes of the Tamesi reveals that those of southern derivation inhabit primarily the small upstream waters, whereas those of northern affinity are chiefly inhabitants of larger and downstream waters. These phenomena are discussed in terms of faunal centers and barriers to dispersal. 1 Contribution No. 6 from the Laboratory of Hydrobiology, Department of Biology, Marquette University. 300 Fishes of the Rio Tamesi Introduction In 1950 the writer initiated a series of studies on the ecology of aquatic communities in the headwaters of the Rio Tamesi drainage in east-central Mexico. A portion of this material was incorporated into his doctoral dissertation presented to the faculty of the University of Minnesota (Darnell, 1953). Although the studies were primarily con- cerned with the composition and trophic structure of the subtropical aquatic communi- ties, problems of taxonomy in the various aquatic groups inhabiting this poorly known area have delayed the appearance of the general ecological treatise. This delay has been occasioned, in part also, by the hope that the manuscript of Hubbs and Gordon on the fishes of northeastern Mexico, imminent for over twenty years, would finally make its appearance. With the recent death of Dr. Gordon the present writer is hesitant to delay further the publication of his ecological work and so has prepared this paper as a back- ground for the ecological study already accomplished, but still unpublished. It was originally intended that the present article should include only the strictly fresh-water fishes of the Tamesi system. This was rendered impossible by the following circumstances, the lack of detailed habitat data for most of the species in the important coastal collections of Jordan and Dickerson (1908), the fact that the writer's Laguna de Chairel collections contained a number of typically brackish water or marine species, and also by the fact that many of the headwater species probably or definitely do not honor the bounds of strictly fresh water. Thus, in the absence of any sharp dividing line, it was decided to include the work of Jordan and Dickerson (1908) and to summarize the present status of our incomplete knowledge of these forms as a point of departure for future work. Several species, so far not recorded from the drainage, are expected to be found when the larger streams and the lagoons around Tampico are adequately sampled. None are included in the present work, however, unless specimens have been reported directly from the drainage (or from coastal areas near the drainage in the case of Fundulus similis and certain forms included in Jordan and Dickerson's collections) . This ex- cludes a number of fresh-water, brackish-water, and marine species whose known dis- tributional ranges extend on both sides of the Tamesi, as well as certain species pre- viously encountered in the Rio Panne° but for which specimens have not yet been taken from the Rio Tamesi. Bailey, Winn and Smith (1954) and Bailey (1956) have recently discussed the basic concept of subspecies in fishes with considerable clarity and reason, and they have cast doubt, not only upon the validity of a number of existing subspecies designations (some of the doubtfully subspecific forms being found in the Tamesi), but also upon the con- cepts on which many of the old subspecies were erected. For reasons best expressed by these authors no subspecies designations are given in the present paper. Future work is re- quired to determine the nature and extent of variation in the local populations, their divergence from other such populations, the clinal nature of such divergence, and the extent to which this may be due to environmental factors. Invalid manuscript designa- tions which have escaped into the literature with unfortunate frequency are, of course, not employed here. A number of the fish species listed herein were first described in the monumental work of Cuvier and Valenciennes (1828-49) . As noted by Bailey (1951) the authorship Fishes of the Rio Tamesi 301 of all such species can and should be determined. In the present work only the appro- priate single author is given for each of these species. MATERIALS AND METHODS Material for the present study was collected during three trips to Mexico in the period 1950-53. The first trip was accomplished April 1—June 7, 1950, the second March 13— June 16, 1951, and the third December 20, 1952—January 3, 1953. Thus, a total of six months was spent in Mexico during the spring, early summer, and winter seasons. Most of the fish collections were made with a 20 or 40 foot (I/4 inch mesh) minnow seine with native help and represent shallow upstream habitats. On the last trip a 150 foot (3/4 inch mesh) bag seine was taken and successfully employed in some of the larger waters. Additional specimens were taken by fyke net, hook, spear, minnow trap, gill net, and plastic window screening. Considerable time was spent observing the habitat dis- tribution and behavior of fishes, especially in the crystal clear waters of the upper stretches of the Rio Sabinas. Such observation was particularly important in relation to groups which normally inhabit the deeper waters and such wary species as the cichlids which make frequent use of shallow areas but which are difficult to capture by seine. Most of the preliminary identifications were carried out by the writer. Robert R. Mil- ler of The University of Michigan Museum of Zoology and the late Myron Gordon of the American Museum of Natural History checked the preliminary identifications on a number of the fishes, but final species determination on almost all specimens was accomplished by Carl L. Hubbs. Food analyses were carried out essentially in accordance with the procedure previously outlined by the writer (Darnell, 1958) . In order to pro- vide a generalized picture of the true food relations of each species, specimens for food analysis were picked from several size classes of both sexes taken at different localities in day and night collections. Where this was not possible it was approximated. COLLECTION AND DISPOSITION OF SPECIMENS During the field work a total of 11,043 specimens of fishes were taken from the Rio Tamesi drainage in seines, fyke nets, and minnow traps. About a dozen additional speci- mens were procured by other means. In all, 66 collections were made in the various por- tions of the drainage as follows: Rio Sabinas and tributaries 54 (reduced to 31) collec- tions (6,768 specimens), Rio Frio and its tributary, the Rio Boquilla, six collections (2,538 specimens) , Rio Mante and its tributaries, four collections (1,272 specimens), Rio Guayalejo, a single collection (221 specimens), and the Laguna de Chairel at Tampico, a single collection (244 specimens) . By far the greatest attention was paid to the fishes of the Rio Sabinas where the general ecological study was in progress, and in order to reduce the number of stations for presentation here the data for many ad- jacent collections were lumped. Due to lack of time, gear, and transportation facilities the fishes of the larger streams as well as the coastal lagoons around Tampico were very inadequately sampled. In addition to the collections mentioned above, the writer has examined most of the material taken by Meek in 1903 from the Rio Guayalejo, but specimens reported from the Tampico area by Jordan and other early workers have not been seen. Most of the 1950-51 material has been deposited in the Chicago Natural History Mu- 302 Fishes of the Rio Tamesi seum. Poorly preserved specimens of the common species were discarded. For the re- maining collections, specimens of a given species taken from the same stream during the same year have been lumped and have received a single (CNHM) catalog number.