Tr ansact i ons of t he Amer i can Fi sher i es Soci et y 123 : 841- 854, 1994 Amer i can Fi sher i es Soci et y Compar i son of Acoust i c and Tr awl Met hods f or Est i mat i ng Densi t y and Age Composi t i on of Kokanee ERI C A . PARKI NSON Br i t i sh Col umbi a M i ni st r y of Envi ronment , Fi sher i es Resear ch Sect i on 2204 Mai n Mal l , Uni ver si t y of Br i t i sh Col umbi a Vancouver , Br i t i sh Col umbi a V6T 1Z4, Canada BRUCE E . RI EMAN U .S. For est Ser vi ce, I nt ermount ai n Resear ch St at i on 316 East Myrt l e St r eet , Boi se, I daho 83702, USA LARS G . RUDSTAM Cor nel l Bi ol ogi cal Fi el d St at i on Depar t ment of Nat ur al Resour ces, Cor nel l Uni ver si t y 900 Shackel t on Poi nt Road, Br i dgepor t , New Yor k 13030- 9750, USA Abst r act . - Thr ee acoust i c and t hr ee t r awl met hods of est i mat i ng densi t y and age composi t i on of kokanee Oncor hynchus ner ka wer e compar ed. Densi t y est i mat es f r omt he t hr ee acoust i c met hods wer e si gni f i cant l y cor r el at ed with each ot her and with t he t r awl est i mat es . Age- cl asses 1- 3 wer e not di st i ngui shabl e f r omeach ot her in acoust i c r ecor ds, but t hei r combi ned peak coul d be separ at ed f r om t hat of age- 0 kokanees on t he t ar get st r engt h f r equency di st r i but i ons pr oduced by bot h t he dual - beam and t he deconvol ut i on anal yses . Dual - beamage composi t i on est i mat es wer e si gni f i - cant l y cor r el at ed with deconvol ut i on (r = 0 . 97) and t r awl (r =0. 70) est i mat es . Deconvol ut i on densi t y est i mat es f or age- 1- 3 f i sh wer e 34%hi gher t han t he dual - beamest i mat es, but nei t her of t he acoust i c densi t y est i mat es di f f er ed si gni f i cant l y f r om t he t rawl val ues due to hi gher var i ance associ at ed with t r awl est i mat es . Acoust i c est i mat es of t ot al densi t i es wer e l ess consi st ent t han t hose f or age- 1- 3 f i sh because of t he pr obl emof est abl i shi ng a consi st ent l ower t hr eshol d f or age- 0 f i sh . At t he ext reme, dur at i on- i n- beam, dual - beam, and deconvol ut i on est i mat es of t ot al densi t y wer e 3 . 3, 1 . 9, and 1 .8 t i mes t he t r awl est i mat es . Di f f er ences in t owi ng speed (1 .0 ver sus 1 .5 m/ s) f or t he sl ow and f ast ot t er t rawl s had little ef f ect on t he est i mat es of ei t her densi t y or age composi t i on, but t he beam t r awl was l ess ef f i ci ent t han t he ot t er t rawl s . Est i mat es of densi t i es f r om t he beam t r awl aver aged 54% , 35% , and 21%of ot t er t r awl est i mat es f or age- 0, age- 1, and age- 2- 3 kokanees ( whi ch aver aged 42, 130, and 198 mm in l engt h, r espect i vel y) , suggest i ng ser i ous si ze sel ect i vi t y f or one or bot h t r awl desi gns. We conduct ed a st udy to assess t he ef f ect i veness of m i dwat er t rawl s and acoust i c met hods in r ou- t i ne st ock assessment of kokanee Oncor hynchus ner ka . Kokanee, t he l and- l ocked f or m of sockeye sal mon, is t he dom i nant speci es in t he l i mnet i c zone of many l ar ge l akes in t he Paci f i c Nor t hwest . Pr obl ems t hat need to be addr essed i ncl ude t he st andar di zat i on of t r awl met hodol ogy and t he