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<br />EXPERIMENTAL USE OF A FRY SORTER <br />AT CLARK'S FORK HATCHERY <br />IN WYOMING <br /> <br />RAYMOND K. MESSAMER <br /> <br />CLARK'S FORK HATCHERY <br />WYOMING GAME AND FISH DEPARTMENT <br />STAR ROUTE, BOX 81 <br />BELFRY, MT 59008 <br /> <br />ABSTRACT <br /> <br />An experimental fry sorter was built at Clark's Fork Hatchery, <br />Wyoming Game and Fish Department, to test the usefulness of <br />this tool on large production lots of trout. It was used with <br />both brown trout (Salmo trutta) and fall-spawn rainbow trout <br />(Salmo gairdneri). The sorter was constructed of materials on <br />hand, and consists of a box-like frame with an inclined ramp of <br />woven brass wire and an open front. Theoretically, the sorter <br />allows healthy fish to swim out into the rearing tank proper, <br />but retains weak and crippled fish inside for easy disposal. <br />In practice, its effectiveness was somewhat less than that con- <br />sidered theoretically possible. However, at least two useful <br />observations resulted from this experiment; 1) traditional timing <br />of the dumping of fry was reaffirmed, and 2) delaying the first <br />cleaning of rearing tanks for three to four days seemed to reduce <br />early mortality significantly. <br /> <br />METHODS <br /> <br />In the early fall of 1982, a publication (Booker and Dingley, 1981) was <br />circulated among Wyoming hatcheries via the area hatchery supervisors. This <br />was done in hopes that some of the techniques described might prove to be <br />useful innovations for Wyoming's hatchery system. <br />When this publication arrived at Clark's Fork Hatchery it was scanned <br />by all personnel. One idea of interest concerned a device known as a fry <br />sorter. Eventually a prototype sorter was constructed in spare time with <br />materials on hand, and prepared for testing. Sorter dimensions (Fig. 1) <br />were adapted to the dimensions of Clark's Fork Hatchery's rearing tanks. <br />The screened interior was sloped at the recommended four inch raise in two <br />feet, as outlined in Booker and Dingley (1981). The sorter was wedged <br />in a rearing tank with the upper edge located just slightly above the water <br />line, and pointed into the current. Because Booker and Dingley mentioned <br /> <br />81 <br />