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relieved to be
<br />e are pelagic
<br />taken m gill
<br />ore. This ]ake
<br />1-size rainbow
<br />anglers also
<br />dolly Varden
<br />end bass.
<br />~rthern Idaho
<br />-sal and fairly
<br />It as 60 feet,
<br />~itat as trout.
<br />Forester and
<br />uawfish from
<br />ess when gill
<br />the spawning
<br />poor catches
<br />id-September,
<br />1~~ taken off-
<br />:OMPETITION
<br />fish taken by
<br />d from the
<br />items in the
<br />~asured volu-
<br />Ia all, the
<br />9 species of
<br />?reille Lake,
<br />°s in Hayden,
<br />ue stretch
<br />. _.5-inch
<br />w gill net
<br />y- Coco-) Pend
<br />a~ lalla Oreille
<br />9 51 20
<br />11.1 1.3
<br />~ i o.oo o.oo
<br />o.oo o.oo
<br />~ o.oo o.oo
<br />Kl o.oo o.oo
<br />~ o.oo o.oo
<br />~l 0.00 0.00
<br />ro o.oo o.oo
<br />.n o.oo o.oo
<br />ro o.oo o.oo
<br />9 0.00 0.15
<br />o.oo o.oa
<br />o.oo o.oo
<br />o.oo o.oo
<br />- o.oo
<br />- o.oo
<br />- o.oo
<br />1-hour period.
<br />~asure).
<br />i
<br />ECOLOGY AND CONTROL Or THE COLli3?~iA SQ1JA~`F1SH 1~9
<br />148 stomachs from 6 species from Hayden Feeding habits of squawfish and the three
<br />Lake, and 100 stomachs from 5 species from species of trout were also examined in relation
<br />Cocolalla Lake. These data are presented in to fish size. Table 3 shows feeding habits for
<br />Table 2. these four species by 4-inch length intervals.
<br />It mill be observed from Table 2 that the It will be obser~-ed that all ate predominantly
<br />lnsett feeders when shorter than 12 inches
<br />food of squawfish in all three Lakes was more with the exception of cutthroat, are pri-
<br />and
<br />than 58 percent fish, being of mixed species ,
<br />marily fish-eating when longer than 16 inches.
<br />in Hayden Lake, yellow perch in Cocolalla
<br />and kokanee in Pend Oreille Lake. Rain-
<br />Lake At the 8- to 12-inch interval, squawfish utilized
<br />,
<br />bow trout, which occurred in all three lakes, mote crustaceans and mollusks than did trout
<br />shifted more rapidly to a
<br />with growth
<br />and
<br />also fed on fish (29 to 79 percent of the food ,
<br />,
<br />fish diet than did either rainbow or cutthroat
<br />was identified as such) but utilized insects trout but less abruptly than Dolly Varden.
<br />(12 to 56 percent). Perch in the three lakes It is apparent from the food habits of these
<br />fed mostly on crayfish and insects. Cutthroat fishes that the squawfish is an important com-
<br />trout fed almost entirely oa insects and moun- petitor for food with rainbow and Dolly Var-
<br />tain whitefish on insects and scuds. Lake white- den trout and to a lesser extent, competes with
<br />fish, taken only from Pend C)reitte Lake, had the cutthroat, crappie, bullhead, and perch.
<br />fed on insects, mollusks, and plant material; .
<br />Dolly Varden trout mostly on kokanee; brown .AGE AND GROWTH OF SQUAwFISH
<br />bullheads on fish, plant material, crayfish, earth-
<br />worms, and scuds; black crappie oa fish, in- In 1957 scales were taken for aging from 40
<br />sects, crayfish, plant material, and Daphnia; squawfish in Pend Oreille and 83 in Cocolal-
<br />and Columbia River chub on mollusks, insects, la Lakes. Using a projector, scale measurements
<br />and plant material. were made and growth calculated to the time
<br />TABLE 3. Food habits of squau~fish, rainbow trout, Dolly Yardetr trout, and cutthroat trout from three
<br />'
<br />northern Idaho lakes by 4-inch length intervals, expressed as percentages of total volume.
<br />Range in total length (inches)
<br />Item 0.1-4.0 4.1-8.0 8.1-12.0 l2.1-1b.0 16.1-20.0 over 20
<br />Squawfish
<br />Stomachs containing food . _._ ...............
<br />Total volume (milliliters) ..................
<br />Fish _.._..._ .........:..........................._..__................,...
<br />Insects .., ........__........_._ ................__...........,...-
<br />Crayfish ..................................................................
<br />....Scuds _..,__._ ......................._..:...:........_T.....----
<br />Moltusks _ _. _.._ ................__._..__...._..........
<br />Plant material _..._...._.....__._............__._
<br />Rainbow trout
<br />Stomachs containing food .....__.._._._..
<br />Total volume (milliliters) .............__.
<br />Fish .,..,..._._._..... _,__...__._......_..-___..._ ..............
<br />Insects ..._..,..._._....,,._ ..............._........_................
<br />Plant material ._ .............................................
<br />Dolly Varden trout
<br />13 7 9 18 35 1
<br />tr. 0.6 3.3 36.7 353.2 32.0
<br />12 50 ]8 94 86 100
<br />88 50 43 3 tr. 0
<br />0 0 30 0 6 0
<br />p 0 3 tr. tr. 0
<br />0 p 3 0 tr. 0
<br />0 0 3 2 7 0
<br />0 3 3? 32 18 6
<br /> 1.4 ]07.9 296.6 195.3 236.0
<br />_... 0 0 22 90 100
<br /> 100 96 75 9 0
<br /> 0 4 2 1 0
<br />Stomachs containing food ..................... 0
<br />Tota! volume (milliliters) ....._._ ........ ......
<br />Fish _........._....._.,..._._......_........_........----.......... ..
<br />Insects _ ................_..._.........._._......................_..... ......
<br />Earthworms __.._....._..._....._..._.........._ ........... .._..
<br />Scuds ._......._ ......................_.........._.........-............ ......
<br />Fish eggs ....._ . _ ........................_......_....._....... ._...
<br />1 1 5 4 14
<br />0.1 0.4 98.1 25.4 1048.0
<br />0 0 75 ]00 100
<br />loo ]oo tr. o 0
<br />0 tr. 16 0 0
<br />0 0 tr. 0 0
<br />0 0 8 0 0
<br />Cutthroat trout
<br />Stomachs cOntainin); food .........__.
<br />....... 0 3
<br />1G
<br />17
<br />2 0
<br />Total volume (milliners) ............. ........ ...... 2.5 50.2 103.9 7.3 ••
<br />Fish _........._._ ............... ... 0 6 tr. 13 .-....
<br />Insects __.- ]00 93 93 85 --
<br />Earthworms 0 0 6 0 ......
<br />Plant material ..... .-.... 0 1 tr. 0 .~.~.~
<br />'Food of squawfisii less than 4 inches in length is expressed as percentages of occurrence rather than volume.
<br />r
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<br />1
<br />t
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