Page 947 - The Toxicology of Fishes

Effects of the Exxon Valdez Oil Spill on Pacific Herring in Prince William Sound, Alaska 927

funds had to be used “for the purposes of restoring, replacing, enhancing, or acquiring the equivalent
of natural resources injured as a result of the Oil Spill and reduced or lost services provided by such
resources.” In addition to acquisition of sensitive habitat, restoration involves two types of research
projects: (1) recovery monitoring projects that track the rate and degree of recovery of resources and
services injured by the spill and that also may determine when recovery has occurred or detect reversals
or problems with recovery; and (2) research projects that provide information required to restore an
injured resource or service or information about ecosystem relationships. Detailed studies were under-
taken on a number of different species. The objective of this case report is to describe the response,
damage assessment, and early restoration studies with Pacific herring (Clupea pallasi).
The most recent detailed survey of lingering oil was conducted in the intertidal zone of PWS in the
summer of 2001 by the U.S. National Oceanic and Atmospheric Administration (NOAA) Auke Bay
Laboratory (Short et al., 2004). Approximately 11.3 ha of shoreline in PWS were still contaminated
with oil. Oil contaminated 86% of the 91 sites assessed and is estimated to have the linear equivalent
of 5.8 km of contaminated shoreline.

Life History and Background
Pacific herring are members of the family Clupeidae, which is abundant throughout the North Pacific.
Pacific herring in PWS first spawn when 3 to 5 years old. Although they spawn annually in April,
abundant year classes recruit into the fishery only sporadically (about every 4 years). Pacific herring in
PWS weigh up to 300 g and can live to be 15 years old, but few fish survive longer than 10 years. They
feed primarily on zooplankton, which is most abundant from May through October. Because Pacific
herring tissues have high lipid content, they are a very important high-energy food source for marine
mammals, birds, and other fish. Commercial fisheries harvest Pacific herring for roe (eggs) and for use
as bait, with a value of about $8 million/year in the 1980s. When the spill occurred in 1989, Pacific
herring populations in PWS were the highest in 20 years of reliable estimates (>1 billion adults). All
life stages were susceptible to damage from the spill. Spawning occurs in shallow bays, and eggs are
deposited and stick to kelp and rocks. Eggs hatch about 21 days after spawning. Resultant larvae are
planktonic (i.e., they drift with the currents) until they are large enough to maintain position against the
currents (about 2 months after hatch). Movements of juveniles were mostly unknown when the spill
occurred, but we have since learned that they congregate in small schools scattered in bays throughout
PWS year-round (Norcross et al., 2001). By comparison, adults aggregate in only a few areas from fall
until early spring. One of the largest fall-to-spring aggregations of adults during the 1990s was in the
bays of northern Montague Island. When adults were abundant, prespawning aggregates of fish in this
area were as large as several kilometers long and 2 to 3 km wide. Postspawning fish disperse throughout
the Sound during the spring and summer feeding season. The major concern for spill-related effects on
adults was that they were in spawning aggregations when the oil spill occurred. Other reviews have
provided detailed maps of the spill trajectory and described some of the impact of the oil spill on Pacific
herring (Brown et al., 1996; Carls et al., 2002; Kocan and Hose, 1997). The objective of this case report
is to demonstrate general principals of damage assessment after an oil spill using Pacific herring and
the Exxon Valdez oil spill as the model.

Post-Spill Damage Assessment
Three types of evidence must be documented for complete damage assessment:

• Potential for exposure—Quantify hydrocarbons in water and mussels.
• Actual exposure—Quantify hydrocarbons or their metabolites in tissues; this could also include
determination of cytochrome P450 levels (e.g., CYP1A).
• Effect—Describe and quantify alterations in behavior, reproduction, growth, tissue morphology
(e.g., gross or microscopic lesions), or mortality.