Ma. Cartwright et al., QUANTIFYING CUTTHROAT TROUT (ONCORHYNCHUS-CLARKI) PREDATION ON SOCKEYE-SALMON (ONCORHYNCHUS-NERKA) FRY USING A BIOENERGETICS APPROACH, Canadian journal of fisheries and aquatic sciences, 55(5), 1998, pp. 1285-1295
Although some sockeye salmon (Oncorhynchus nerka)enhancement programs
achieve production goals in Alaskan lakes, others like the Margaret La
ke project fall well below expected levels. We used bioenergetics mode
l simulations, coupled with field sampling of predator diet and distri
bution, to quantify the intensity of cutthroat trout (Oncorhynchus cla
rki) predation on stocked sockeye salmon fry in Margaret Lake during 1
993 and 1994. Model results indicated that, by September, cutthroat tr
out consumed an estimated 34-51 and 32-100% of the 200 000 and 100 000
sockeye salmon fry stocked in May 1993 and 1994, respectively. Septem
ber hydroacoustic survey results estimated a 82-87% decline of fry in
1993 and 90-93% in 1994. Stomach fullness and evacuation estimates of
total consumption were 59% of model estimates after the first fry rele
ase in 1994 and 120% of the model estimates after the second release.
All approaches to estimating cutthroat trout predation on stocked fry
suggested that piscivores played a substantial role in the decline of
sockeye salmon fry in Margaret Lake. The ability to estimate consumpti
on is valuable in isolating predator influence on food web dynamics, e
specially in manipulated systems.