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r <br />Abstract <br />Three laboratory experiments demonstrated effects of absence, <br />delayed presentation, and quantity of food (Artemia salina nauplii) on <br />mortality and growth of larval razorback sucker, yrauchen texanus. <br />'Ilse majority of larvae died between 20 and 30 d post hatching when no <br />food was provided. If abundant food was presented from 7 d after <br />hatching, larvae experienced no mortality. Larvae starved for 11, 15, <br />and 19 d, then given abundant food, had respective mortalities of <br />10.0, 10.0, and 26.7%, which were not significantly different froaa <br />those of larvae receiving food from 7 d after hatching. Mortality was <br />significantly greater for larvae without food 27 (86.7%) and 31 d <br />(93.3%). Razorback sucker larvae fed frost 7 d after hatching, but at <br />variable food concentrations, experienced mortality in excess of 70% <br />at 5 and 10 nauplii 171. Larvae fed rations of 50 to 1000 nauplii L 1 <br />exhibited significantly lower mortality (<203%). At 50 nauplii L-1 a <br />threshold was reached, beyond which increases in prey density did not <br />result in significant decreases in mortality. <br />Larvae which did not receive food during the first 31 d after <br />hatching were smallest (15.8 mm TL) and similar in size to larvae fed <br />from 7 d after hatching at coricmntrations of 5 to 50 nauplii L71. <br />Larvae first presented with sufficient food up to 15 d after hatching <br />-grew largest (21.7 to 23.2 earn TL), and comparably to those larvae <br />first fed from d 7 at concentrations of 500 and 1000 nauplii 171. <br />The min? prey density resulting in <50% mortality was between <br />10 and 50 nauplii 171• Mortalities continued in 5 and 10 nauplii L'1 <br />treatments until the concentration of nauplii to fish was between 30