552 



Fishery Bulletin 88(3), 1990 



Figure 1 



A single raceway containing three artificial gravel-filled redds and respective upstream and downstream compartments. Entering water was 

 aerated and passed through a series of four baffles to reduce turbulence over the redds. Water exited through a standpipe at the opposite 

 end of each raceway. Emerging fish, after entering either the upstream or downstream compartment, were removed and scored 3-5 times daily. 



Eggs of a single female were fertilized with the pooled 

 sperm of 12 males. Following fertilization, eggs were 

 suspended in a continuous flow of lake water regulated 

 with dechlorinated city water to a constant tempera- 

 ture of 12°±1°C. One week prior to hatching (late 

 organogenesis), eggs were divided into three groups 

 of 150 eggs and each group was transferred to glass 

 petri dishes for a 24-hour exposure in a volume of 0.4 

 mL water per egg. B[a]P (Aldrich Chemical Co, Pro- 

 duct #B 1,008-0) was suspended in spectrophotometric 

 grade DMSO (Schwarz/Mann Biotech, Product 

 #820636) to make a stock solution of 10 mg/mL. This 

 solution was diluted in lake water to make the final ex- 

 posure concentrations of 25 /ig/mL. The control groups 

 were exposed to filtered lake water, the solvent con- 

 trol group was treated with 0.5% solution of dimethyl- 

 sulfoxide (DMSO) in filtered lake water, and the ex- 

 posure group was treated with 25 fjg/mL of B[a]P in 

 0.5% DMSO in lake water. 



Experimental apparatus 



Artificial redds were constructed in replicate raceways 

 by subdividing each raceway into ten compartments 

 (Fig. 1). The upstream compartment contained baffles 

 to reduce water turbulence in the redds. The remain- 

 ing nine compartments included three redds (30 cm 

 wide X 40 cm long) each occupying a single compart- 

 ment and centered between an open upstream and 

 downstream compartment (30 cm wide x 20 cm long). 

 The redds consisted of smooth rocks (2-4 cm diameter) 

 contained within perforated stainless steel plates. Ad- 

 jacent open compartments were separated by plastic 

 netting. The redd surface was within 8 cm of the water 

 surface and the open compartments were 20 cm deep. 



Mention of trade names does not imply endor.scment by the National 

 Marine Fisheries Service. NOAA. 



The water, filtered to remove large particulates, flowed 

 through each raceway at a velocity of 45 cm/second. 

 Following exposure, the eggs were rinsed with lake 

 water and buried 8-10 cm deep in artificial redds. The 

 position of the various groups in each raceway was 

 randomized. The redds were maintained in darkness 

 throughout embryonic development at a temperature 

 of 12.0° + 1°C. Beginning 60 days postspawning, the 

 raceways were checked daily for emerged fry, and, 

 following emergence of the first fry, the raceways were 

 checked three to five times daily. Alevins emerged and 

 held station above the redds while orienting against the 

 water flow. After several minutes they would (1) swim 

 into the upstream compartment, (2) swim into the 

 downstream compartment, or (3) drift backward into 

 the downstream compartment. 



Data collection 



The presence of an alevin in either the upstream or 

 downstream compartment provided a quantitative 

 measure of the ability of the fish to perform its typical 

 upstream swimming behavior. Fish in the upstream 

 and downstream compartments were counted and 

 removed. Furthermore, 20 fry from the upstream and 

 downstream compartments of each exposure group 

 were randomly selected for measurements of total 

 length, dorsal fin height, caudal fin height, pectoral fin 

 height, anal fin height, and dry weight. An analysis of 

 variance followed by a Student-Newman-Kuels multi- 

 ple range test was used to test for significant differ- 

 ences among the means of the various exposure groups. 



Results 



Rainbow trout were exposed to a sublethal 24-hour 

 pulse (25 /ig/mL) of B[a]P during late organogenesis. 

 The emergence success of rainbow trout treated with 



