DUltUfeU, I’ B“; VIwfARD, G. L. @.prrtmrofBidogi’ddprcgminErcros,., ElduttdrdccrotimBioiog,., ut{r6lrof}i6.d4Rs Nq

Year: 1995 (xxvii)

Abstract

Self-thinning implies that density dependent rates of birth, mortality and/or emigration adjustpopulation densif in response to resource limitation. Slopes of thinning lines in animal pip,rl“tio.,r’”.“often the reciprocal of the slope relating indh’idual metabolic requirementsL body mass. Ti-ris implies thattotal population ener$r requirements remain constant as average individual body mass changes (energeticequivalence)’ We investigated self-thinning by anaiprng body size and abundan.” art“ for salmonid fishesfrom the intermountain westem United States. negression of population density on average body massindicated slopes were consistent with the energeti. “qrri.r.l.r,“e Lypothesis in only about hali of the casesanalyzed’ Further analyses showed the use of..r”.ag. body size may bias body s-ize- abundance analysesh foY9f of energetic equivalence. Exceptions to self-ihinning and energetic “qirral”r,.e may be e4pljned !11 {ffelences among species and altemating periods of pf,ysical ““J uioti. control. IHUBBS sruDENr pApERcoMPETTTORI PnoceeorNcs oFTru. DEsERTFrsHgs CouNcrL, 1995 Syvposnnr VoulrdilOivfi - Rrru$m 1996 RESLIVfEN El auto’adelgazamiento implica que las tasas de nacimiento, mortalidad y/o migraci6n que son d:i:dtp:“dientes aiustan la densi’Jed de pobiaci6n en respuesta a los recursos limitadosl Las pendientesde lineas de adelgazamiento en pobiaciones animales son fiecuentemente el reciproco de la pend.iente querelaciona los requerimientos metab6licos y la masa del cuerpo- Esto implica qr. -1o, requerimientos totalesde energra de la poblaci6n permanecen constantes como cambios promed.io en la masa colporai individual(equivalencia energ6tica). Nosotros investigamos el auto-adelgazamiento analizando datos de tallas yabundancias para peces salm6nidos de las montaflas interiores del oeste de los Estados Unidos. I-aregresi6n de la densidad de la poblaci6n vs. la masa corporal promedro indic6 que las pendientes fueronconsistentes con la hip6tesis de la equivalencia energ6tica en tan s6lo la rnitad de ios casos anaJizados.Analisis adicionales mostraron que el uso de la masalromed,io puede sesgar los an6lisis talla-abund.ancia a favor de equivalencias energdticrs. las excepciones al auto-adelgazaniento y equivalencia energ6tica ffif.mm;nj#lnnla entre especiesyperiodos alternativos de control fisicoy bi6ticoipepEr DUXSITIOOR, L. 1nth Tdbo Nsuurr Rgrc, Groquin” oR) Predation by planarian flatworms and fathead minnows on embryos and lanzae of endangeredsuckers in Oregon KEYWORDS: predation; planarians; fathead minnorl recruitment; catostomid.s; l,ost River sucker: shortnose sucker Research into earlylife history of two endangered. catostomid.s (lost River sucker, Deltisas luxatus and.shortnose sucker, Chasmistcs brevirostris in the ,Ipp“, Klamath River basin, Oregon) has focused on theinflylce of predation on recruitment dlmamics. \Ato.k is not,vet complete, but several interesting resultsmerit immediate dissemination among other researchers and sranagers Survivat of l,ost River suckers toemergence in artificially placed substrate is being investigated in a shoreline spring entering Upper I(amath 3:, Ini-tial goals n’eie to assess incubation ,.r.“”“, reiative to degree of spring-,ater influence, butPlanarian flatworm (Platyhelmintltes, Order Triclad.ida) predators killed almost all experimental embryos. 35 L