COUNTING TROUT AND SALMON FRY

THERE CURRENTLY IS NO AVAILABLE MECHANICAL METHOD FOR COUNTING EMERGING COLDWATER SPECIES FISH FRY UNDER 15 GRAMS. OFTEN THE FRY COUNTED IN THE EYED EGG STATE APPROXIMATELY THREE WEEKS AFTER THEY ARE COLLECTED. INCUBATION PERIODS ARE DEPENDENT ON WATER TEMPERATURES AND SPECIES AND VARY FROM FOUR TO SIX WEEKS. AS THE BLANKS (UNFERTILIZED EGGS) AND WEAKER EGGS DIE, THE MORTALITIES ARE COUNTED AND SUBTRACTED FROMTHE ORIGINAL NUMBER. THE RESULTING DIFFERENCE IS THE CALCULATED NUMBER OF FRY. SAMPLING TECHNIQUES ARE ALSO COMMON, SUCH AS COUNTING THE NUMBER OF FRY IN A GIVEN WEIGHT, SUCH AS A POUND OR OUNCE, THEN MULTIPLYING THIS NUMBER BY THE NUMBER OF POUNDS. THIS RESULTS IN A REASONABLY ACCURATE COUNT BUT IS VERY LABOR INTENSIVE. CANNIBALISM, HOLES IN SCREENS, PREDATORS AND REPORTING INCONSISTENCIES COMBINE TO PRODUCE INACCURATE FRY COUNTS. AN ACCURATE, EASY TO OPERATE, ELECTRO-MECHANICAL DEVICE WOULD BE AN ASSET TO HATCHERIES THAT NEED PRECISE COUNTS OF FISH FRY TO MANAGE THEIR OPERATIONS.