748 
Abstract .—The Exxon Valdez oil 
spill occurred just prior to the spring 
migration of Pacific herring, Clupea 
pallasi, from offshore feeding grounds 
to nearshore spawning areas in Prince 
William Sound (PWS), Alaska. Most or 
all of the life stages of herring in PWS 
may have been exposed to oil after the 
March 1989 spill. Delayed impacts from 
the spill were suspected as one possible 
cause in the unprecedented crash of the 
adult herring population in 1993 and 
stimulated studies to assess reproduc- 
tive success. In spring 1995, mature 
herring were collected from four sites 
in PWS and from three uncontaminated 
sites in southeast Alaska (SE) to deter- 
mine if reproductive impairment was 
evident in PWS herring six years after 
the spill. Herring were artificially 
spawned and their eggs were reared in 
a laboratory until hatching. Observed 
response parameters included fertiliza- 
tion success, hatching times, hatching 
success, as well as larval viability, 
swimming ability, and spinal abnor- 
malities. Responses of all year classes 
combined or those restricted to the 
same year class did not differ signifi- 
cantly between regions (P>0.50); the 
best and worst responses generally oc- 
curred in the SE. Within each site, re- 
sponse of the 1989 year class (most 
likely impacted by the oil spill in PWS) 
generally did not differ significantly 
from any other year class. To verify 
macroscopic observations, a subset of 
larvae from the 1989 year class was also 
inspected microscopically for yolk and 
pericardial abnormalities, and yolk vol- 
ume was measured — but no significant 
regional differences were observed for 
any of these morphological categories. 
Based on the parameters examined in 
this study, evidence of reproductive im- 
pairment of Pacific herring in PWS by 
the spill was not detected in 1995, and 
the chances of detecting any oil-related 
effects against natural background 
variation appeared to be negligible. 
Manuscript accepted 28 May 1997. 
Fishery Bulletin 95:748-761 (1997). 
Reproductive success of Pacific herring, 
Clupea pallasi, in Prince William Sound, 
Alaska, six years after the 
Exxon Valdez oil spill 
Scott W. Johnson 
Mark G. Carls 
Robert P. Stone 
Christine C. Brodersen 
Stanley D. Rice 
Auke Bay Laboratory, Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
1 1 305 Glacier Highway 
Juneau, Alaska 99801-8626 
E-mail address (for S.W. Johnson): scott.johnson@noaa.gov 
The Exxon Valdez oil spill (EVOS) 
in Prince William Sound (PWS), 
Alaska, occurred just a few weeks 
prior to the Pacific herring, Clupea 
pallasi, spawning season. Most or 
all of the life stages of herring in 
PWS may have been exposed to oil 
after the March 1989 spill. Biologi- 
cally available hydrocarbons were 
present in the upper water column 
of PWS for several weeks following 
the spill (Short and Harris, 1996a), 
and residual oil may have persisted 
in some areas into 1990 (Short and 
Harris, 1996b). An estimated 40- 
50% of the egg biomass in PWS was 
deposited within the oil trajectory 
(Brown et al., 1996a). The failure of 
the 1989 year class to recruit to the 
fishery and the subsequent crash of 
the 1993 population (Meyers et al., 
1994) suggested that the early life 
stages of herring were impacted ei- 
ther from exposure of prespawning 
adults or from direct exposure of 
eggs and larvae. Thus, as fish ex- 
posed to oil were recruiting into the 
fishery (20% by age 3, 80% by age 
4, 100% by age 5; Funk 1 ), the her- 
ring population crashed, and recov- 
ery was minimal through the 1996 
season (Wilcock 2 ). Genetic damage, 
physical deformities, and small size 
were reported for newly hatched 
larvae following the spill (Brown et 
al., 1996a; Hose et al., 1996; Nor- 
cross et al., 1996; Marty et al., in 
press), but long-term effects remain 
unknown. In a preliminary study in 
1992, Kocan et al. (1996b) observed 
decreased reproductive success in 
herring from an oil-contaminated 
area in PWS compared with an un- 
contaminated area; results were 
inconclusive, however, because only 
two sites were compared. Delayed 
effects from the spill were suspected 
as one possible cause of the popula- 
tion decline and stimulated the 
1 Funk, F. In prep. Age-structured as- 
sessment of Pacific herring in Prince Wil- 
liam Sound, Alaska and forecast of abun- 
dance for 1994. Regional Information 
Report, Alaska Department of Fish and 
Game, Commercial Fisheries Management 
and Development Division, PO Box 25526, 
Juneau, AK 99802-5526. 
2 Wilcock, J. 1996. Alaska Department of 
Fish and Game. Commercial Fisheries 
Management and Development Division, 
PO Box 669, Cordova, AK 99574. Per- 
sonal commun. 
