Geology topics

Anthony R. DeGange

Publications and source records attributed to Anthony R. DeGange.

22 records · Page 2Linked to original sources

USGS1991

Mortality of seabirds in the Japanese land-based gillnet fishery for salmon

Mortality rates of seabirds in the Japanese land-based drift gillnet fishery for salmon were assessed from 413 gillnet sets made by Japanese research vessels in offshore areas used by the commercial fleet. Sixteen species of seabirds were recorded in nets. Shearwaters, primarily Short-tailed Shearwaters ( Puffinus tenuirostris ), and to a lesser extent Sooty Shearwaters ( P. griseus ), predominated in the catches, followed by lesser numbers of Tufted Puffins ( Fratercula cirrhata ) and Thick-billed Murres ( Uria lomvia ). Catch-rates of seabirds varied by oceanographic zone, with most being caught in oceanic waters north of the Subarctic Front. Approximately 151,000 seabirds were killed in the offshore component of the land-based fishery in 1977. Mortality was reduced to about 57,000 seabirds in 1987 because of a reduction in fishing effort. No estimates are available of seabird mortality in the nearshore component of the fishery. Mortality of seabirds in the land-based fishery is discussed with respect to other major drift gillnet fisheries in the North Pacific.

The Condor↗

USGS1990

Procedures and rationale for marking sea otters captured and treated during the T/V Exxon Valdez oil spill

Four methods were used for marking sea otters ( Enhydra lutris ) captured and treated during the response to the T/V Exxon Valdez oil spill. Colored and numbered flipper tags were placed on each sea otter that was brought to the otter treatment centers. These tags allowed individual recognition and permitted the tracking of individuals through the treatment and holding processes. Recovery of tagged carcasses may provide a crude measure of the fates of rehabilitated otters. Seven sea otters were instrumented with radio transmitters attached to flipper tags as part of a pilot release program. The results of that study were inconclusive. Forty-five sea otters were implanted with radio transmitters as part of a study to assess the fate of rehabilitated sea otters. Specific objectives of the study include estimating survived rates and monitoring the reproductive success of the sample of rehabilitated sea otters and comparing the results with similar variables in a control population. Transponder chips were injected in the perianal region of all but seven of the instrumented sea otters, and all were tagged with red flipper tags. The advantages and disadvantages of each type of tag are discussed.

Alaska↗

USGS1988

Interactions between seabirds and fisheries in the North Pacific Ocean

Interactions between commercial fisheries and seabirds in the northern Pacific Ocean are increasing with rising consumption of fishery products. As fishing expands into remote areas previously not fished, additional populations of seabirds may be affected. Some interactions such as introduction of fish processing wastes into the environment may be beneficial for seabirds, while others such as competition for fish prey and incidental take by fishing nets may have negatively affected seabird populations.

Book chapter↗

USGS1986

Marine birds

In this chapter we review existing knowledge of marine birds in the Gulf of Alaska. Three estuarine systems in the Gulf provide critical habitat for migratory shorebirds and waterfowl: 1) the Stikine River Delta, 2) Cook Inlet, and 3) the Copper River Delta. Over 20 million waterbirds are estimated to use the latter system during spring migration. Western sandpipers, dunlin, and northern pintails numerically dominate this migration. Breeding populations of shorebirds and waterfowl in the Gulf are small compared with those elsewhere in Alaska. Of those Gulf regions suitable for nesting waterfowl and shorebirds, the Copper River Delta is the most important. Species diversity and the number of shorebirds wintering in the Gulf are low; however, water- fowl wintering in the Gulf number at least in the low millions. These birds concentrated in sheltered, near-shore regions where their epibenthic and infaunal prey are accessible. Over nine million seabirds (twenty-six species) nest in the Gulf of Alaska at more than 800 sites. Seabird productivity varies markedly. Food availability seems to have a large influence on reproductive success, especially for surface-feeding species such as the black-legged kittiwake. Seabird densities are highest over shelf and shelf-break habitats during spring migration and in summer. Sooty and short-tailed shearwaters dominate the pelagic avifauna both numerically and in terms of biomass. Seabird densities are generally lower in winter than in summer as a result of both a southward migration of some species and offshore dispersal of others. A variety of prey species are used by seabirds in the Gulf; of these, capelin, sand lance, and euphausiids are of greatest importance. Trophically, seabirds in the Gulf range from near primary con- sumers to third-order carnivores, ingesting an estimated 1,120,000 mt during the 120-day summer period.

Alaska↗