Strains of five trout species used in the management of U.S. fisheries

Abstract

Surveys of trout broodstocks maintained by federal and state fisheries agencies during 1980, 1982, and 1984 identified broodstocks currently used in fishery management programs. Information obtained on each broodstock included broodstock origin, hatchery performance, field performance, disease resistance, management utilization, and breeding practices employed to maintain each broodstock. The number of trout broodstocks maintained in state and federal programs during 1984 were: rainbow trout (75 and 18), brook trout (36 and 4)) brown trout (35 and 6)) cutthroat trout (33 and 5)) and lake trout (16 and 7). Broodstock numbers have declined since 1980 in the rainbow trout ( 10.5%), brook trout ( -14.6%), brown trout ( -7.0%) and cutthroat trout ( 7.3% ) but have increased in the lake trout ( + 64.3%). This trend toward fewer broodstocks is partially attributed to an increased awareness by fisheries personnel of strain performance differences which has led to the discontinuance of poorer broodstocks. The impact of this increased “efficiency” on long-term reductions in species genetic diversity is discussed. General breeding practices followed to perpetuate broodstocks were similar in all five species and could be partitioned into three general types: random mating within year classes of a broodstock (33.8%)) random mating between different year classes of a broodstock (37.0%)) and mating according to a specialized selection system (29.2% ) . Traits included in selection programs for individual broodstocks were: body conformation (15)) growth rate (lo), egg quality (lo), color (7), disease resistance ( 6)) spawning time (4)) and longevity (2 ) . Implications of observed trends in management usage and breeding methods are discussed. Distribution of genetic variation within and among hatchery strains of lake trout (Salvelinus namaycush) J. ELLEN MARSDEN, CHARLES C. KRUEGER and BERNIE MAY Dept. of Natural Resources, Cornell University, Ithaca, NY 14853 (U.S.A.)