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174 MINNOW FAMILY, CYPRINIDAE 1962). However, their habitat requirements need to be carefully reevaluated since _ , Vanicek and Kramer (1969) did not capture any in swift water but found them only in pools and eddies. It is possible that, although they spend most of their time in quiet water, they forage for food in swift water. There they presumably would have a competitive advantage over roundtail chubs, with which they often occur. The streamlined shape would also be advantageous during times of flood (Minckley, 1973). - The water in which they are generally found is muddy and the bottom is of clay, mud , silt, and/or boulders, with few aquatic plants. The feeding habits of bonytails have been studied extensively only by Vanicek and Kramer (1969). They found large bonytails (over 20 cm TL) to be omnivorous surface ~,~.~ feeders, taking terrestrial insects, filamentous algae, and plant debris such as leaves , stems, seeds, and horsetail stems. They do not seem to be selective in their feeding , taking every variety of food that falls on the water. Small fish (less than 3 cm TL) feed `` mostly on aquatic insect larvae and become more dependent on surface food as they grow larger. Growth in small bonytails is similar to that of small roundtail chubs, from which they are difficult to distinguish: 55 mm TL and 1 gm at age I, 100 mm TL and 8 gm at L age II, and 158 mm TL and 31 gm at age III (Vanicek and Kramer, 1969). However as , they grow larger, they increase in length faster than roundtail chubs, but the weight increase is smaller in proportion to length, a consequence of their more elongate, streamlined form. The largest and oldest fish encountered by Vanicek and Kramer ' ~ (1969) was seven years old, measured 39 cm TL, and weighed 422 gm. Spawning apparently takes place in May and June, once the water temperatures ° exceed 18 C, over gravel riffles or rubble-bottomed eddies (Vanicek and Kramer , 1969, Sigler and Miller, 1963). Breeding behavior was observed in Lake Mojave, Nevada, in May by Jonez and Sumner (1954). About 500 bonytails had congregated over agravel-covered shelf, 9 m deep. As is typical of such cyprinid spawning groups, the males outnumbered the females by two to one, and each spawning female was attended by three to five males. The eggs were broadcast over the gravel, to which they adhered. The spawning areas were not defended by any of the fish. The spawners were 28 to 36 cm TL. A 31 cm TL female contained 10,000 eggs. 1 Young fish are apparently planktonic for a short time after they hatch but they are soon found in the quiet, shallow waters of the river's edge. Status. At one time, bonytails were one of the commonest fish on the lower _ Colorado River but, by 1942, they were quite rare (Dill, 1944). They now seem to be extinct in the California portion of the Color d Ri a o ver because the swift muddy water they require has been impounded and changed in character. They stilt seem to be fairly ~ common in the upper reaches of the Colorado River but even there the populations are declining (Miller, 1961a; Vanicek and Kramer, 1969). The take possession and sale of `;~ , , , bonytails is currently forbidden by California state law but their preservation is really in the hands of the states upstream from California. $onytails are likely to be around for future generations to study and enjoy onl if lar e t t h f y g re s c es o the Colorado River are left with substantial natural flows. References. Dill, 1944; Holden and Stalnaker, 1970; Jonez and Sumner, 1954; La Rivers, 1962; Leach and Fisk, 1972; R. R. Miller, 1946, 1961a; Minckley 1973; , Minckley and Deacon, 1968; Sigler and Miller, 1963; Vanicek and Kramer,~1969.