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Alaska Predator Ecosystem Experiment (APEX)
APEX Project:
Alaska Predator Ecosystem Experiment in Prince William Sound
and the Gulf of Alaska
Project Director: Bruce Wright
Project Leader: David Duffy
Study History: The research project APEX (the Alaska Predator Ecosystem Experiment) was initiated under Restoration Project 94163 entitled Forage Fish Influence on Recovery of Injured Species. This pilot project was designed to investigate prey (forage fish) distribution, abundance, and availability. The 1995 project, 95163 Seabird/Forage Fish Interactions, merged together a group of existing bird and forage fish investigations and proposals to provide an integrated research approach that examined the interactions of seabirds and their prey, the reasons that changes in prey might have occurred, and the consequences for seabirds. The primary hypothesis to be tested is that several seabird species have failed to recover from the Exxon Valdez oil spill because of shifts in food supply that may have occurred independently in the marine ecosystem of Prince William Sound and the northern Gulf of Alaska. In 1996 (96163) the project incorporated Cook Inlet study sites, modeling components, and broad ecosystem approach to addressing the projects objectives. The last year in the field for APEX was 1999, followed by a year of data analysis and production of publications.
Abstract: The Alaska Predator Ecosystem Experiment was a seven-year study of the effect of food resources on seabirds in Prince William Sound and Cook Inlet. The study examined historical data, forage fish resources, seabird reproduction and colony and population dynamics to address this issue. Research strongly suggested a basic shift in ecosystem structure occurred after the late 1970's, with a decrease in species nutritious to seabirds and an increase in species less rich in lipids. This resulted in population declines for several forage species and may help explain the subsequent failure of seabird species to recover from Exxon Valdez oil spill mortality.
Key Words: Ammodytes, Brachyramphus, Capelin, Clupea, Cook Inlet, Fratercula, Guillemot, Gulf of Alaska, Herring, Kittiwake, Mallotus, Murre, Murrelet, pollock, Prince William Sound, puffin, Rissa, sandlance.
Citation: Wright, B. A. and D. C. Duffy. 2000. APEX Project: Alaska Predator Ecosystem Experiment in Prince William Sound and the Gulf of Alaska. Exxon Valdez Oil Spill Restoration Project 00163, Auke Bay Fisheries Laboratory, 11305 Glacier Highway, Juneau, AK 99801.
David Duffy and Bruce Wright at the APEX project in Cook Inlet, Alaska.
INTRODUCTION:
The spill from the oil tanker Exxon Valdez in Prince William Sound in 1989 resulted in significant mortality of several seabirds and in acute massive damage to Prince William Sound and the Gulf of Alaska. Five years following the spill, several species had not recovered. This may be the result of lingering effects of the oil spill, predation, changes in habitat and ecosystem structure or in food quality, abundance and availability.
Seabird/fish researchers in the Prince William Sound/Gulf of Alaska complex have concluded that major changes in food have occurred resulting in a biological regime shift. The APEX project had its origin in 1994 when a suite of unrelated projects were funded by the Exxon Valdez Oil Spill Trustee Council. APEX investigators made the case that an integrated program was necessary, combining forage fish projects with bird studies of pigeon guillemots and black-legged kittiwakes. Bruce Wright was the APEX project director, and David Duffy was the APEX project leader.
General Hypothesis
A shift in the Prince William Sound marine trophic structure has prevented recovery of resources injured by the oil spill of the Exxon Valdez.
Working Hypotheses
1. The trophic structure of Prince William Sound has changed at the decadal scale.
2. Planktivory is the factor determining abundance of the preferred forage species of seabirds.
3. Forage fish species differ in their spatial responses to oceanographic processes.
4. Productivity and size of forage species change the energy potentially available for seabirds.
5. Forage fish characteristics and interactions among seabirds limit availability of seabird prey.
6. Seabird foraging group size and species composition reflect prey patch size.
7. Seabird diet composition and amount reflect changes in the relative abundance and
distribution of forage fish at relevant scales around colonies.
8. Changes in seabird productivity reflect differences in forage fish abundance, as measured in
adult seabird foraging trips, chick meal-size and chick provisioning-rates.
9. Seabird productivity is determined by differences in forage fish nutritional quality.
10. Seabird species within a community react predictably to different prey bases.
After a late November 1995 meeting to review the results of the first year of research, the Exxon Valdez Oil Spill Trustee Council made a decision to continue the project and APEX was underway, undertaking five years of field work (1994-1999) and two years of write-up and synthesis (2000-2001). APEX had 20 sub-projects, but its structure was highly dynamic, with projects beginning when they were identified as a critical need and ending when they had fulfilled their contribution to APEX.
List of Projects
Subproject Short Title (Principal Investigators)
A. Fish population sampling (Haldorson, Thedinga)
B. Seabird foraging (Ostrand)
C. Fish diet analysis (Sturdevant)
D. Puffin diet and productivity (Piatt)
E. Kittiwake foraging and reproduction (Irons/Suryan)
F. Guillemot foraging and reproduction (Golet)
G. Seabird reproduction and energetics (Roby)
H. Proximate analysis (Worthy)
I. Project leader (Duffy)
J. Barrens nesting study (Roseneau)
K. Predatory Fish Diets (Roseneau)
L. Historical analysis (Anderson, Piatt & Blackburn)
M. Cook Inlet studies (Piatt)
N. Captive rearing studies (Romano)
O. Statistical support (McDonald)
P. Sand lance oiling (Anderson)
Q. Modeling (Ainley, Ford & Schneider)
R. Marbled Murrelet (Kuletz)
S. Jellyfish (Purcell)
T. Aerial Survey (Brown/Norcross)
One of the APEX findings is that changes in the northeast Pacific marine ecosystem food web (see below, slide courtesy of Paul Anderson) can have dramatic impacts on all trophic levels, including declines in some predators (seals and marine birds), and increases in others (salmon, pollock, and sharks).
Historical data, from long-running sampling of the Gulf of Alaska show a major change in the marine ecosystem associated with increased water temperatures in the late 1970s. This led to a change from capelin and shrimp to flatfish and pollock. Seabird diets reflect this change; capelin and sand lance were replaced by pollock. At-sea studies during APEX show an abundance of pollock offshore, with schooling species such as herring and sand lance inshore. Most seabird foraging has been concentrated inshore on these species. Capelin have been rare and limited to certain areas.
APEX field studies of black-legged kittiwake, marbled murrelet, and pigeon guillemot show they have better reproductive success when consuming schooling species; forage fish availability and breeding success are positively linked. Laboratory studies show seabirds grow better and have heavier masses at fledging when fed schooling species. Nutritional studies show that schooling fish have higher lipid (and energy) levels than do pollock. Finally, models of populations and foraging show that certain colonies contribute disproportionately to the dynamics of a species.
The bottom line is that changes in the marine ecosystem of the Gulf of Alaska led to a low-fat lean cuisine on which seabirds had difficulty raising young. Scientists are still exploring why this shift occurred and the mechanism through which it affects seabirds.
The main implication for management is that recovery will continue to be inhibited as long as present ecological conditions exist. Our studies have identified key colonies and foraging areas that should be protected during future oil spills and during development of infrastructure in Prince William Sound and the Gulf of Alaska.
These are forage fish, herring, caught during an APEX survey.
For more information on APEX see: Ott, R. 2004. Sound Truths and Corporate Myths. Dragonfly Sisters Press. pages 317-342.
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