Dear  Helene: The very rapid growth in seal and sea lion populations in
many areas poses a serious threat to several endangered or threatened
salmon and steelhead stocks. Moreover, this excessive growth rate may
cause problems for the seal populations themselves. Therefore, many
scientists feel that research aimed at identifying a desirable control
level is badly needed. In a few areas, there is probably justification
for reduction in existing seal and sea lion populations now.

For more detailed info and a bibliography you might contact Professor
Mate at Oregon State University

Best wishes.

James A. Crutchfield