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142 HAMILTON ET AL. TABLE 3 Selenium Concentrations in Control Fish from Laboratory Studies and Reference Fish from Field Studies Study type and selemum concentration Reference Species" Whole-body selenium (~ggl Laboratory Water (~g! liter) 20 ~O ~O 0.4 <0.4 0.2 0.3-l.4 <3 <3 Diet ().lg,g) 0.7 0.8 + 2.7' 0.07 0.6-0.7 2.0 l.0 0.4 Bluegill Bluegill Largemouth bass Rainbow trout Striped bass Chinook salmon Chinook salmon Razorback sucker Bony tail Bluegill Bluegill Rambow trout Rainbow trout Chinook salmon Chinook salmon Fathead minnow Water (~g; liter) <2 ~ 0.2 Fathead minnow S t ri ped bass < 1 Diet (~gjg) l.y Bluegill Striped bass Fish 2.4' Bluegill 7.6 1.0 0.4-0.8b 0.8b 0.7b 1.1-1.4 1.2 -1.4 1.1-2.0 1.2 1.1 Cleveland et al.. 1993 Lemly. 1982 Lemly. 1982 Hodson et al.. 1980 Saiki et al.. 1992 Saiki et al.. 1992 Hamilton and Wiedmeyer. 1990 Hamilton et al.. 2000 Hamilton et al.. 2000 1.0 3.3 0.3 0.2 1.2 0.8-1.0 2.7 Cleveland et al.. 1993 Coyle et al.. 1993 Hilton et al.. 1980 Hilton and Hodson. 1983 Hamilton et al.. 1986 Hamilton et al.. 1990 Ogle and Knight. 1989 Field I.2b 1.3-1.9 Schultz and Hermanutz. 1990 Saiki and Palawski. 1990 Culler. 1989 Hermanutz et al.. 1992 1.6b 4.4b 0.4-2.4b Couglan and Velte. 1989 Pakkala et al.. 1972 Pillay et al.. 1974 Finley, 1985 "Bluegill (Lepomis macrochirus). largemouth bass (Micropterus salmoides), rainbow trout (Oncorhynchus myklssl. chinook salmon (Oncorlnnclws tsha.....ytscha). fathead minnow (Pimephales promelas). striped bass (Morone saxatilis). razorback sucker (Xyrauchen texanus). bony tail (Gila elegans). b Reported as wet weight and converted to dry weight assuming 75% moisture. " Dry diet contained 0.8 ~g/g and brine shrimp nauplii contained 2.7 ).lgjg. d Golden shiner (,Votemigonus crysoleucas). , Meal worm (Tenebrlo molilOr). species. Similarly, Adams (1976) reported that selenium con- centrations in dead rainbow trout were 2.7 l-lg/g compared to those in live fish of3.2l-lg/g, which additionally shows the narrow range between lethal and sublethal residues. Ad- verse effects may have been occurring in the wild larvae; however, no measurements in the field were conducted to verify adverse effects. The wild larvae were collected from a demographically open population where loss of larvae due to predation and competition from nonnative fish, contaminant effects, or other stresses associated with a wild, free-flowing river could be masked by movement of larvae from one backwater area to another. Similarly, spawning of adult razorback sucker over several days (Tyus and Karp [1990] reported ripe females over a 2- to IS-day period; Valdez et al. [1982] reported ripe adults over a 2-week period) could have added larvae to the population at a time when losses might be occurring due to predation, competition, contaminants. or other stresses. Table 1 indicates that composite 4 from Cliff Creek, composite 4 from Sportsman's Drain. and composite 3 from Greasewood Corral were composed of smaller larvae than in earlier composite samples from the respective loca- tion. This occurrence of smaller larvae at later collection times suggests young larvae were being added to the cohort from successive spawns. Selenium concentrations in larvae from these three sites followed this pattern of larval size. i.e.. low selenium concentrations in smaller larvae. The wild larvae collected in the present study were surviv- ors from wild spawners in a free flowing river and. as such. had survived a variety of stresses before arriVIng at the