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31 The Status of the Desert Pupfish, Cyprinodon macularius, at the Salton Sea, California. by Glenn Black California Department of Fish & Game The desert pupfish, Cyprinodon macularius, is the only species native to the Salton Sea area and has been reported as "abundant" as recently as 1958 by Barlow. However, incidental collections made in the last 15 years indicate that their distribution and numbers may have been severely reduced. This seems to have;coircided with the introductions of several exotic species into the irrigation drains leading to the Salton Sea and to their movement into habitats utilized by desert pupfish. The above- mentioned exotic species include the sailfin molly, Poecilia latapinna, the shortfin molly, P. mexicana, the red shiner, Notropis lutrensis and Zill's cichlid, Tilapia zillii. In order to determine the extent of the immigration of these exotic species into desert pupfish habitats, the California Department of Fith and Game has conducted three quarterly surveys at the Salton Sea. Live minnow traps and seines were used to sample fish populations in irrigation drains and tributaries to the Salton Sea as well as in shoreline pools (pools of Salton Sea water separated from the Sea by sand bars) and the Salton Sea proper. Results from the three surveys have shown that 14 species of fish have been collected from the various habitats and that the most abundant and widely distributed of all species is the sailfin molly. The sailfin molly has made up 73%, 85% and 86% of the fish captured from the irrigation drains; 86%, 69% and 69% of the fish from the tributaries; 89%, 93% and 93% of the fish from the shoreline pools; and 74%, 90% and 97% of the fish from the Salton Sea proper during the three surveys. In contrast to this, the desert pupfish has contributed to less than 1%, 9% and 2% of the fish sampled from the irrigation drains during the three surveys; to less than 1% of the fish sampled in all three surveys of the tributaries; to 5%, 2% and less than 1% of the fish sampled in the surveys of the shoreline pools; and to 1% or less in the surveys of the Salton Sea proper. Despite the fact that pupfish have been found in all four types of habitats sampled, they appear to be very restricted within each habitat, especially in irrigation drains. They prefer areas of irrigation drains that have a sand substrate, a water depth of less than 3 feet (0.9 m), turbidity of less than 100 JTU's and aquatic vegetation. The three surveys clearly show that the desert pupfish is in serious trouble at the Salton Sea due to the introduction of exotic species. In addition to this, another serious threat exists in the form of possible permanent alteration of irrigation drain habitat through the concrete lining or pip- ing of these drains by the irrigation districts surrounding the Salton Sea.