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<br />Proper understanding of the razorback sucker's unique niche and <br />reproductive strategy are paramount in directing recovery efforts toward <br />providing for its habitat needs. <br />The striking form of the razorback's bony, inverted "boat-like" keel <br />has evoked varied interpretations as to its function (Figure 3). Many interpret <br />the keel as an adaptation to fast-water environments. However, this fish's <br />preference for feeding in quiet nutrient-rich waters suggests a function related <br />more, to lentic habitat. The "boat-like" keel and large extended pectoral fins <br />more likely provide great lateral and vertical stability for feeding in lake-like <br />floodplain environments, while its highly efficient gill rakers sieve the water <br />of zooplankton. Razorback specimens from Lake Mohave had intestinal tracts <br />entirely filled with planktonic crustaceans in May (Minckley 1973). Plankton <br />was also utilized as food for razorback sucker in riverine environments of the <br />northern part of its range and the length and "fuzziness" of razorback sucker <br />gill rakers "approach those of the presumably plankton-eating suckers <br />comprising the genus (Chasmimistes) ..." (Hubbs and Miller 1953) <br />Minckley (1973 p 155) described razorback sucker's feeding as being <br />rather whale-like: <br />"The fish moved with their mouths projecting forward and <br />with a "bouncing", up and down pattern produced by slow, <br />alternating sweeps of the caudal fin. The pectoral fins were held <br />stiffly extended, producing a plane effect, and, little lateral <br />movement of the head was evident, perhaps as a result of the keel- <br />like, anterodorsal surface which may act as a lateral stabilizer." <br />This feeding behavior described by Minckley suggests that access during <br />spring runoff to extensive "food-rich" floodplain habitats, such as those <br />described by Powell on the middle Green River, is important in providing <br />opportunity to use their special feeding adaptations. If confined to fast water, <br />lotic habitat, razorback sucker are forced to compete within primary niches of <br />9