316 NOTES AND NEWS

RANGE EXTENSION OF PENAEUS () OCCIDENTALIS STREETS, 1871 (, ) INTO THE GOLFO DE TEHUANTEPEC

BY

ISABEL PÉREZ FARFANTE SystematicsLaboratory, National Marine Fisheries Service, NOAA, U. S. National Museum, Washington, D. C. 20560, U.S.A.

The three eastern Pacific members of the subgenus Litopenaeus, which com- prises the American Penaeils commonly known as white , are sympatric in the waters off northern Peru. Two of them, P. (L.) stylirostriJ Stimpson, 1871, and P. (L.) vannamei Boone, 1931, range northward to the Gulf of California, and the former is also found along the oceanic coast of the Territorio de Baja California as far north as Punta Abreojos. The third , P. (L.) occidentalis Streets, 1871, however, has not been reported north of El Salvador. During the course of a field trip to the Pacific coast of southern Mexico, in August of 1970, I had the opportunity to preserve a number of samples from the commercial catches in the Golfo de Tehuantepec. Among those samples, one consisted of a large female, 50.5 mm cl (= carapace length), P. occidentali.r together with four males (40.5 to 45.5 mm cl) and three females (50.5 to 59 mm cl) of P. styliro,ftris. This material had been caught off the coast of Chiapas, between San jos6 and Monte Alto, at 24 m, on August 8, by David Palacios. The discovery of P. occidentalis in Mexican waters represents an exten- sion of the range of the species of about 500 km northwest of the previously known limit which was in the western portion of the grounds off the mouth of Rio Lempa, El Salvador (Lindner, 1957). The present observation adds a new member to the list of commercial shrimps of Mexico. These three species are by far the most important commercial shrimps of the Pacific waters off Central America and northern South America, and P. occiden- talis is the most abundant of the three south of El Salvador. In the latter country, this species accounts for 23 percent of the catches of white shrimps; however, southward its contribution increases as follows: 66 percent of the production of Costa Rica (80 percent according to a personal communication by James Kale, co-manager of a large shrimp freezing plant in Puntarenas), 85 to 90 percent of that of Panama, and as much as 82 percent of the total catches of Colombia. The proportion of this species is lower in the landings of Ecuador, but still constitutes 60 percent of those of white shrimps which, in turn, make up the bulk of the production (statistical data from Gross, 1973). Apparently, P. occi- dentalis occurs in very small numbers north of El Salvador, its presence northward having been detected neither by two surveys of catches from Guatemala (Lindner, 1957; [U.S.] Bureau Comm. Fish., 1962) nor during the sampling program in the Golfo de Tehuantepec by members of the staff of the Instituto Nacional 317 de Investigaciones Biol6gico-Pesqueras, Mexico (Hector Romero and Hector Chapa Saldana, personal communication).

TAXONOMIC REMARKS

Penaeu.r (L.) occidentalis may be readily distinguished from P. vannamei by possessing more than two teeth (three to five) on the ventral margin of the rostrum (fig. lA), a characteristic it shares with P. stylirostris, in which there are usually three to eight. It differs from the latter in that the dorsal margin of the rostrum is generally unarmed for less (usually considerably less) than a third of its length, and the antennular flagella are subequal in length and both shorter than the peduncle. Furthermore, the petasmata and the thelyca of the three species exhibit features that are peculiar to each. In P. occidentalis the

Fig. 1. PenaellJ (Litopeyrc?ezs.r)occidentali.r Streets. A, anterior region, ? 45 mm cl, off Panama City, Panama; B, petasma (extended), dorsal view, $ 41.25 mm cl, off Playas, Ecuador; C, thelycum, lectotype, 19 mm cl, Isthmus of PanamA; D, thelycum, ? 51 mm cl, between San jos6 and Monte Alto, Chiapas, Mexico. Scales in mm.