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<br />THE EFFECT OF ARTIFICIAL INCUBATION <br />SUBSTRATES ON THE GROWTH AND SURVIVAL <br />OF BROWN TROUT FRY <br /> <br />JAMES L. VOELKER <br /> <br />RIFLE FALLS HATCHERY <br />COLORADO DIVISION OF WILDLIFE <br />11466 STATE HIGHWAY 325 <br />RIFLE, COLORADO 81650 <br /> <br />ABSTRACT <br /> <br />Brown trout (Salmo trutta) alevins were incubated in Heath <br />Tecna vertical tray incubators containing rugose plastic sub- <br />strates and compared to alevins incubated on smooth screen in <br />floating trays, and on smooth screen in deep baskets. Both <br />screen-substrate groups exhibited a much higher incidence of <br />yolk sac malformation and coagulation than did the plastic- <br />substrate group. After seven weeks of feeding, fry incubated <br />in plastic substrates were significantly heavier than fry incu- <br />bated on either of the smooth screens (p < .05). During the <br />seven weeks of feeding, cumulative mortality appeared to be <br />less in the plastic-substrate group (3.9% versus an average of <br />6.7% for both smooth-screen groups). <br /> <br />INTRODUCTION <br /> <br />Brown trout (Salmo trutta) are incubated and reared at several state <br />hatcheries in Colorado with varying degrees of success. Most of these fish <br />are stocked as fingerlings. Fish of high quality are essential in order to <br />maximize survival in the wild. Encouraged by results obtained with Atlantic <br />Salmon (Salmo salar) (Bonney and Leon 1979), we decided to try incubating <br />brown trout alevins with rugose plastic substrates in an effort to improve <br />the quality of fry and fingerlings. The study took place at the Rifle Falls <br />Hatchery near Rifle, Colorado. <br /> <br />METHODS AND MATERIALS <br /> <br />Eyed brown trout eggs of the Soda Lake Strain were obtained November 23, <br />1982 from the Dubois, Wyoming, State Fish Hatchery. A total of 279,625 eggs <br />were received and divided into three groups for hatching, incubation, and <br />rearing at a mean temperature of 520F. Groups one and two were held in 1) <br />floating trays or 2) deep baskets. Both the trays and baskets had a smooth <br />screened substrate and were floated in hatchery tanks ~easuring 29 x 2.7 x <br />2.2 ft. Water flow per tank was 120 gpm and was directed through bottom <br />manifold pipes to provide an even, upwelling flow. Initially, there were <br />17,020 eggs per floating tray and 28,367 eggs per deep basket. The third <br /> <br />87 <br />