Offshore distances of gray whales migrating along the Oregon and Washington coasts, 1990

Abstract

Acrialsur\eyswefeconductedduringJuuaryandNlarch.|990.todererminethewidthoithcgraysh^lc(Eul]itlttiusrobunu')southbound and nofihbound migralion corridor\ along Oregon and \\ra\hirgtor.Nligralirg gray t!hales occurred significantly farther offshore during ihe southbound migraljon co pared to the nofthbound migralion.Al!r'.whalcs occuned significantl) iarlhcr ofihore Whshingtm th.rn Oregon duing bo$ migration l)eriods.which we attribute to ,t poflion fic $halcs tbllo\\ing a more direcl oi\horc roule between approxinately &e Clolurnbia River mouth and centfal\'rLncouver Island fttlher than a longcr neafshore route pen Capc Flattery.When conrpared \t ith pre!ious sludies.rhe migration coffidor along the co.rslsLrf Oregon and \\h\hingt(nl appean |tl bc botl seilsonall) and rnnu.rllyelastic.and in solnc locations expanding x\ frr offshore s .13kln.These results question lhc lcasibilily of conducting rccufrte shore b.rsed gra) whalc censuses along these coasts becruse of the high propofiion ol wh,rlcs trarcling he,vond a shore-based observcr's rangc of vje$'.Ihese results.Ll\o suggest that the nigration coffidor is sullicicnlly wide.especiall] durhg the sourhbound nrigrarion.drat it might olerlap potemtial oftshore oil dcvcloprncnl arers 0n rhc conrincntal shelf.