Abstract. -The sublethal effects 

 induced by a model carcinogen and 

 environmental contaminant on salmo- 

 nid emergence behaviors have been 

 studied. Flainbow trout embryos were 

 exposed for 24 hours to 25 iJglmL of 

 benzo[a]pyrene 1 week prior to hatx-h- 

 ing. Exposures occurred during the 

 late organogenesis period of develop- 

 ment and allowed assessment of how 

 a single embryonic exposure might 

 affect emergence behaviors nearly 6 

 weeks later. Though no differences 

 in numbers of alevins successfully 

 emerging were observed, a signifi- 

 cant decrease was noted in perfor- 

 mance of the upstream orientation 

 behaviors characteristic of emergence 

 among wild individuals. These find- 

 ings are discussed in terms of a model 

 describing the role of upstream swim- 

 ming behavior after emergence. 



Decreased Performance of 

 Rainbow Trout Oncorhynchus 

 mykiss Emergence Behaviors 

 Following Embryonic Exposure 

 to Benzo[a]pyrene 



Gary K. Ostrander 



College of Ocean and Fishery Science. University of Washington U/H-IO 

 Seattle, U/ashington 98195 



Present address Department of Zoology. Oklahoma State University 

 Stillwater, Oklahoma 74078 



James J. Anderson 

 Jeffrey P. Fisher 

 Marsha L. Landolt 

 Richard M. Kocan 



College of Ocean and Fishery Science, University of Washington WH-10 

 Seattle, Washington 98195 



Manuscript accepted 16 April 1990. 

 Fishery Bulletin. U.S. 88:551-555. 



As aquatic ecosystems worldwide con- 

 tinue to function as ever-increasing 

 reservoirs of environmental pollu- 

 tants, the presence of many diverse 

 classes of compounds is being docu- 

 mented (Champ and Park 1982). One 

 class of compounds, the aromatic hy- 

 drocarbons, has been implicated in 

 carcinogenesis in feral fish popula- 

 tions (Baumann 1989). Previous stud- 

 ies (Ostrander et al. 1988, 1989) and 

 work presented here suggest that 

 aromatic hydrocarbons may also ex- 

 ert subtle, yet profound, behavioral 

 effects during early development. 



Benzo[a]pyrene (B[a]P) is an aro- 

 matic hydrocarbon that is combus- 

 tion product of organic materials 

 (e.g., forest fires). Furthermore, an- 

 thropogenic activities have introduced 

 significant amounts of B[a]P into the 

 aquatic environment both directly 

 (industrial emissions and oil spills) 

 and indirectly (automobile exhaust 

 and coal burning). This compound has 

 been well studied in mammalian sys- 

 tems (reviewed in Gelboin 1980), and 

 much is known of its mode of action. 

 Recently we have verified the sen- 



sitivity of coho salmon early-life- 

 history stages to a single embryonic 

 exposure to benzo[a]pyrene (Ostran- 

 der et al. 1988). Embryonic exposure 

 to B[a]P resulted in temporal differ- 

 ences in hatching, reduced and altered 

 emergence success, and decreased 

 foraging efficiency. 



We next studied emergence behav- 

 iors following embryonic B[a]P expo- 

 sure of the rainbow trout Oncorhyn- 

 chus mykiss. We describe the effect 

 of B[a]P exposure on the emergence 

 success and upstream swimming be- 

 havior. A qualitative model, utilizing 

 data from our rainbow trout and coho 

 salmon studies, is proposed to explain 

 the effects of toxicants on these early 

 life behaviors. 



Materials and methods 



Experimental animals 

 and exposures 



Two replicates of a single experiment 

 with rainbow trout were conducted 

 with eggs obtained fi-om the McCleary 

 Trout Lodge, Tacoma, Washington. 



551 



