A Revised List of Euryhalin Fishes of North and Middle America GORDON GUNTER Reprinted from THE AMERICAN MIDLAND NATURALIST Vol. 56, No. 2, pp. 345-354, October, 1956 University of Notre Dame Pre s Notre Dame, Ind. A Revised List of Euryhalin Fishes of North and Middle America Gordon Gunter Gulf Coast Research Laboratory Ocean Springs, Mississippi It has been long known that certain marine fishes enter fresh-water in addi- tion to anadromous species that run up rivers. to spawn. Gunther (1880, p. 202) said: "Almost every large river offers instances of truly marine fishes ... ascending for hundreds of miles of their course; and not periodically, or from any apparent physiological necessity, but sporadically throughout the year ..." Ordinary faunistic surveys, which are usually made without salinity determinations, indicate that this phenomenon is more common in the tropics than in temperate regions. Nevertheless, it is common in North America and several authors have mentioned it.. Marine fishes are found in the Atchafalaya River of Louisiana over 160 miles from the sea (Gunter, 1938b) and numerous marine species occur in fresh-water at Homasassa Springs, Florida (Gunter, 1942, Herald and Strickland, 1949) . Bailey, Winn and Smith (1954) questioned these records but furnished others for the Gulf Coast. Odum (1953) has shown that the fresh-waters of Florida generally, including Homosassa Springs are quite high in salt content. Crabs (Gunter, 1938b) and other marine animals also enter fresh-water, but the action is much more common to fishes and doubtless takes place at all coastal river mouths to some extent. Some fresh-water fishes also descend the rivers and spend a time at sea. Myers (1938, 1949) has proposed a six division classification of fishes with regard to salt tolerance, which is particularly useful in zoogeographic studies. In this paper we are not particularly concerned with those problems. Remarks and records in the literature on the salinity where fishes are captured are scattered, incomplete and hard to find because they are included as side issues in papers devoted to other subjects. The writer attempted to summarize the information for North and Middle America by compiling a list of the fishes of the continent which have been found in both fresh- water and sea water (Gunter, 1942). Due to the incompleteness of the literature, the help of a number of ichthyological workers was solicited. The response was gratifying and several unrecorded observations were brought to light. This paper is essentially a revision and extension of the former list. An animal which will withstand or tolerate gross salinity changes is said to be euryhalin. There are all degrees of euryhalinity, grading from animals which can withstand little or no salinity change to those which can change from sea water to fresh-water or vice versa and live in either environment indefinitely. There are aieo degrees of rapidity with which animals can undergo salinity changes, but little is known of this aspect of the subject. The term euryhalin has never been rigidly defined and any rigid definition is essentially arbitrary. The writer (Gunter, op. cit.) defined an euryhalin 345 346 THE AMERICAN MIDLAND NATURALIST 56(2) fish as one which had been recorded from both fresh-water and pure sea water by competent observers. Only fishes falling into that category were included in the former list and in this revised list. This definition excludes several fresh-water fishes and a greater number of marine fishes which enter bay waters of low salinities. The definition includes catadromous and anadromous species and both fresh-water and marine fishes which enter the other environ- ment occasionally and irregularly. Some fishes on the list may not be able to withstand fresh-water or pure sea water indefinitely, and for many species the matter can only be determined by experimentation. The list was made up conservatively and species were not included unless definite evidence was forthcoming that the fish belonged in the euryhalin cate- gory as defined. In several cases there was strong ancillary evidence that species belonged on the list, but such fishes were placed in a group called probably euryhalin. That group is not treated here and interested readers should consult my previous paper (Gunter, op. cit.). The above definition of euryhalinity depends, among other things, upon the definition of fresh-water. Probably no animal could live indefinitely in distilled water, and the term pure fresh-water is ambiguous. All land waters contain some salt and rain may range up to about 10 parts per million chloride, when it is near the sea. Soft fresh-water runs from about 0.05 to 0.07 per mille salt or 50 to 70 parts per million; hard fresh-water may be 0.30 parts per thousand salt. The fresh-waters of various coast lines differ considerably in salt content; on certain low lying coasts some of this salt may come from the sea and fresh-water records of marine fishes from such coasts are always suspect. On this continent Florida fresh-waters are a special case. Odum (1953) has shown that the lower peninsula and the east coast area, almost half of the peninsula, has waters with a chloride content of 100 parts per million and sometimes more. This is over twice the chloride content of hard fresh- water which is generally about 40 parts per million. Many of the records of marine fishes in the fresh-waters of Florida are from areas where the chlorinity is 570 to 900 parts per million (Odum, op. cit.), which lies in the oligohaline zone. Therefore,a number of the fishes from Florida fresh- waters are not included in the following lists, because their inclusion would be at variance with the basic conceptions of the list as applied to other areas. Nevertheless, these species are marine invaders in Florida waters, and Carr and Goin (1955) have recorded the following species from Florida, which have not been reported from fresh-water elsewhere: Dasyatis hastata (De Kay), Anchoa h. hepsetus Bonnaterre, Adinia xenica (Jordan and Gilbert), Diplo- dus holbrooki (Bean), Eucinostomus argenteus Baird and Girard, Diapterus olisthostomus (Goode and Bean), Eleotris abacurus Jordan and Gilbert, Bathygobius soporator (Cuvier and Valenciennes), Lophogobius cyprinoides (Pallas), Microgobius gulosus (Girard), Paralichthys albigutta Jordan and Gilbert and Symphurus plagiusa (Linnaeus). REVISIONS IN THE LIST OF EURYHALIN FISHES The Gulf shad, Alosa alabamae Jordan and Evermann, and the Mis- sissippi Valley or Gulf alewife, Pomolobus chrysochloris Rafinesque, are added 1956) GUNTER: EURYHALIN FISHES 347 to the list. The former is known to be anadromous and presumably the latter is, too. It has been recorded from widely scattered points in the Mississippi Valley and Central Texas and from sea water on the Texas coast (Gunter, 1945) . Brevoortia smithi Hildebrand, of the Atlantic coast, is added to the list on the authority of Carr and Goin (1955). Brevoortia patronus Goode is added on the authority of Gunter and Shell (in press). Brevoortia gunteri Hildebrand, was recorded from full salt water in Texas, under the name Brevoortia sp. (Gunter, 1945). I have since taken it in fresh-water in the Mission River, Refugio County, Texas, and the species is added to the list. The ariid catfish, Galeichthys guatemalensis (Gunther) is added to the list on the authority of Carr and Giovannoli (1950, p. 12) . The Gulf of Mexico cyprinodontid, Fundulus similis (Baird and Girard), is added to the list. It is a resident of salt and brackish waters, occasionally being found in pure fresh-water. Gambusia affinis (Baird and Girard) is also added to the list on the authority of Hildebrand (1917) . The Pacific cod, Gad us macrocephalus Tilesius, is added to the list on the authority of Dr. John T. Greenbank, who saw a specimen that had been caught by an angler in the Naknek River, Alaska about one mile below Naknek Lake, which is at least 25 miles by river to the sea. The water there is purely fresh. The fish was about 24 inches long. I am indebted to Dr. Carl L. Hubbs for the information. The Atlantic cod has been reported in fresh water by fishermen, but this statement remains to be verified by an ichthyologist. The rough silverside, Membras martinica (Cuvier and Valencienna), is added to the list on the authority of Gunter and Shell (in press) . The Pacific coast marine goby, Gillichthys miriabilis Cooper, is added to the list on the authority of A. S. Lockley (personal communication) . One eel and six gobies from the Gulf Coast are added on the authority of Bailey, Winn and Smith (1954), who carefully measured salinities at their stations. The species are: Myrophis punctatus (Liitken), Eleotris pisonis (Bloch), Gobionellus boleosoma (Jordan and Gilbert), G. hastatus Girard, G. shufeldti (Jordan and Evermann), and Gobiosoma robustum Ginsburg. The previous list of euryhalin fishes of North and Middle America was published in four parts, with northern Mexico as the dividing line on the West coast. On the east coast the northern division ran from the Arctic to southern Florida and the southern division ran from northern Mexico to southern Panama. This four part list was arranged to show certain results which a straight list would not bring out. The Gulf of Mexico was left out, but the Gulf species are included on the list given below. As previously published, the list was an annotated one giving the reasons for including a given species and a simplified notation showing whether the fish was catadromous, anadromous, a fresh-water fish of marine ancestry, a marine fish of fresh-water ancestry or a purely fresh-water or marine species. Besides the addition of a certain species, as enumerated above, the quadruple division of the list is abandoned here and the species are given as a straight list without comment.