Publications

The 1991-93 El Nino-Southern Oscillation (ENSO) event first appeared in the northern Gulf of Alaska in autumn 1991 with warm sea-surface temperatures. In winter 1992, there were pulses of increased sea level and anomalous circulation. El Nino conditions persisted at least through summer 1993. The effects of this ENSO event on major groundfish species and Pacific herring in the northern...

Survival models assume that fates of individuals are independent, yet the robustness of this assumption has been poorly quantified. We examine how empirically derived estimates of the variance of survival rates are affected by dependency in survival probability among individuals. We used Monte Carlo simulations to generate known amounts of dependency among pairs of individuals and...

Estimates of the relative effects of demographic parameters on population rates of change, and of the level of natural variation in these parameters, are necessary to address potential effects of perturbations on populations. We used a stochastic model, based on survival and reproduction estimates of the Porcupine Caribou (Rangifer tarandus granti) Herd (PCH), during 1983-89 and 1989-92...

Twenty-two Golden Eagle (Aquila chrysaetos) nesting territories and 31 occupied eagle nests were documented on the north slope of the Brooks Range in northeastern Alaska, 1988-1990, in an area previously thought to be marginal breeding habitat for eagles. The mean number of young/successful nest was 1.25 in 1988, 1.27 in 1989, and 1.13 in 1990; means did not differ significantly among...

40Ar/39Ar geochronology reveals that turbidite-hosted gold deposits in the southern Alaska accretionary prism are the same age as nearby near-trench plutons. These early Tertiary plutons and gold lodes formed above a slab window during subduction of an oceanic spreading center. Ridge subduction is a previously unrecognized tectonic process for the generation of lode gold.

Nesting success was studied at Canvasback Lake and Mallard Lake on the Yukon Flats in interior Alaska in 1989–1991. Simple estimates of nesting success were computed using two techniques that assume a constant daily survival rate (DSR). Maximum-likelihood estimates of nesting success for all ducks, assuming constant DSR, ranged among years and sites from near zero to 12%. However, DSRs...

Most change-in-ratio (CIR) methods for estimating fish and wildlife population sizes have been based only on assumptions about how encounter probabilities vary among population subclasses. When information on sampling effort is available, it is also possible to derive CIR estimators based on assumptions about how encounter probabilities vary over time. This paper presents a...

Stomach contents were collected from sport-caught halibut in Glacier Bay National Park. Stomach samples containing a combination of fish and invertebrate species were observed less frequently than expected. Small, subtidal, noncommercial crab and cod-like fish (Gadidae) appear to be the most important prey items. In thc dict of Pacific halibut. Preliminary findings suggested that dict...

Calf mortality is a major component of caribou (Rangifer tarandus) population dynamics, but little is known about the timing or causes of calf losses, or of characteristics that predispose calves to mortality. During 1984-87, we radiocollared 226 calves (≤3 days old) in the Denali Caribou Herd (DCH), an unhunted population utilized by a natural complement of predators, to determine the...

Over the past decade, the Marbled Murrelet has become a focus of much controversy. It was listed as threatened in Washington, Oregon, and California by the U.S. Fish and Wildlife Service in February 1993. In order to aid the various agencies with management, the Marbled Murrelet Conservation Assessment was formed to bring together scientists, managers, and others to gather all the...

We began a three year study in 1987 to test the feasibility of using sonar in the Togiak River to estimate salmon escapements. Current methods rely on periodic aerial surveys and a counting tower at river kilometer 97. Escapement estimates are not available until 10 to 14 days after the salmon enter the river. Water depth and turbidity preclude relocating the tower to the lower river and...

We examined gut contents of 1799 seabirds comprising 24 species collected in 1988-1990 to assess the types and quantities of plastic particles ingested by seabirds in the subarctic waters of Alaska. Of the 15 species found to ingest plastic, most were surface-feeders (shearwaters, petrels, gulls) or plankton-feeding divers (auklets, puffins). Of 4417 plastic particles examined, 76% were...