Jw. Testa et al., ESTIMATING POPULATIONS OF MARINE RIVER OTTERS IN PRINCE WILLIAM SOUND, ALASKA, USING RADIOTRACER IMPLANTS, Journal of mammalogy, 75(4), 1994, pp. 1021-1032
One year after the spillage of oil from the Exxon Valdez in spring 198
9, we used radiotransmitters and radiotracer labels to mark river otte
rs (Lutra canadensis) at Knight Island (oiled) and Esther Passage (uno
iled) in Prince William Sound, Alaska. Feces recovered from latrines o
f animals were used as ''recaptures'' in mark-recapture experiments to
estimate the density of river otters in the two coastal study areas.
Our methods were evaluated for sources of bias in estimating and compa
ring population sizes. There was no evidence that densities of river o
tters at Knight Island (oiled) were less than those at Esther Passage
(unoiled) in summer 1990 or that density of river otters at Knight Isl
and was declining. Estimates of river otters in Prince William Sound r
anged from 0.28 to 0.80 animals per km of coastline. Our estimates are
similar to those for marine river otters in southeastern Alaska, but
bias in the different methods should be considered.