Double-Observer Line Transect Methods: Levels of Independence

Double-observer line transect methods are becoming increasingly widespread, especially for the estimation of marine mammal abundance from aerial and shipboard surveys when detection of animals on the line is uncertain. The resulting data supplement conventional distance sampling data with two-sample mark–recapture data. Like conventional mark–recapture data, these have inherent problems for estimating abundance in the presence of heterogeneity. Unlike conventional mark–recapture methods, line transect methods use knowledge of the distribution of a covariate, which affects detection probability (namely, distance from the transect line) in inference. This knowledge can be used to diagnose unmodeled heterogeneity in the mark–recapture component of the data. By modeling the covariance in detection probabilities with distance, we show how the estimation problem can be formulated in terms of different levels of independence. At one extreme, full independence is assumed, as in the Petersen estimator (which does not use distance data); at the other extreme, independence only occurs in the limit as detection probability tends to one. Between the two extremes, there is a range of models, including those currently in common use, which have intermediate levels of independence. We show how this framework can be used to provide more reliable analysis of double-observer line transect data. We test the methods by simulation, and by analysis of a dataset for which true abundance is known. We illustrate the approach through analysis of minke whale sightings data from the North Sea and adjacent waters.

EC30-39 Swine Sanitation

From the very beginning of Nebraska's agricultural development its farmers have recognized that the production of swine must of necessity accompany the growing of corn. The latter, one of the state's most important staples, cannot be marketed in a more economical manner than after having been transformed into pork, bacon, and lard. As a result the state has for many years maintained a rather dense swine population mainly divided into large herds kept on relatively small areas of land. This density of population, as well as certain practices in management and selective breeding, has brought about conditions favorable for the propagation of a number of microbic or parasitic diseases which, in a costly manner, force themselves to our attention. The various factors which affect the incidence of swine diseases are numerous and in a given situtation may be so intricately interwoven as to baffle the observer. This extension circular discusses these factors and how to prevent the spread throughout the swine population.

Taking account of dependent species in management of the Southern Ocean krill fishery: estimating crabeater seal abundance off east Antarctica

1. The crabeater seal Lobodon carcinophaga is considered to be a key species in the krill-based food web of the Southern Ocean. Reliable estimates of the abundance of this species are necessary to allow the development of multispecies, predator–prey models as a basis for management of the krill fishery in the Southern Ocean. 2. A survey of crabeater seal abundance was undertaken in 1500 000 km2 of pack-ice off east Antarctica between longitudes 64–150° E during the austral summer of 1999/2000. Sighting surveys, using double observer line transect methods, were conducted from an icebreaker and two helicopters to estimate the density of seals hauled out on the ice in survey strips. Satellite-linked dive recorders were deployed on a sample of seals to estimate the probability of seals being hauled out on the ice at the times of day when sighting surveys were conducted. Model-based inference, involving fitting a density surface, was used to infer densities in the entire survey region from estimates in the surveyed areas. 3. Crabeater seal abundance was estimated to be between 0.7 and 1.4 million animals (with 95% confidence), with the most likely estimate slightly less than 1 million. 4. Synthesis and applications. The estimation of crabeater seal abundance in Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR) management areas off east Antarctic where krill biomass has also been estimated recently provides the data necessary to begin extending from single-species to multispecies management of the krill fishery. Incorporation of all major sources of uncertainty allows a precautionary interpretation of crabeater abundance and demand for krill in keeping with CCAMLR’s precautionary approach to management. While this study focuses on the crabeater seal and management of living resources in the Southern Ocean, it has also led to technical and theoretical developments in survey methodology that have widespread potential application in ecological and resource management studies, and will contribute to a more fundamental understanding of the structure and function of the Southern Ocean ecosystem.

Killer Whale Predation on Belugas in Cook Inlet, Alaska: Implications for a Depleted Population

Killer whale predation on belugas in Cook Inlet, Alaska, has become a concern since the decline of these belugas was documented during the 1990s. Accordingly, killer whale sightings were compiled from systematic surveys, observer databases, and anecdotal accounts. Killer whales have been relatively common in lower Cook Inlet (at least 100 sightings from 1975 to 2002), but in the upper Inlet, north of Kalgin Island, sightings were infrequent (18 in 27 yr), especially prior to the 1990s. Beach cast beluga carcasses with teeth marks and missing flesh also provided evidence of killer whale predation. Most observed killer whale/beluga interactions were in the upper Inlet. During 11 of 15 observed interactions, belugas were obviously injured or killed, either through direct attacks or indirectly as a result of stranding. Assuming at least one beluga mortality occurred during the other four encounters, we can account for 21 belugas killed between 1985 and 2002. This would suggest a minimum estimate of roughly l/yr and does not include at least three instances where beluga calves accompanied an adult that was attacked.

A REVISIONARY APPROACH TO CROSS-CURRICULAR LITERACY WORK

In this dissertation, I use qualitative research methods to study relationships between compositionists and faculty in other disciplines in the context of cross-curricular literacy (CCL) work. Drawing on a two-year CCL project in the biology department, for which I was a participant observer, I argue that compositionists need to attend more carefully to issues that influence day-to-day interactions with disciplinary faculty in order to develop more meaningful CCL relationships. Toward that end, I offer a revisionary approach to cross-curricular literacy work that cultivates complex relationships by delaying consensus and embracing disconnection and disorientation. More specifically, I employ revisionary stance as a discursive strategy to complicate three key concepts in CCL literature and scholarship—expertise, change, and outcomes. I re-vision three texts produced during my time in the biology department in order to illuminate the complexities of negotiating expertise, recognizing change, and pursuing outcomes in CCL contexts. Given the reciprocal relationship between discursive and material change (Lee), I maintain that revision of CCL discourse can inspire revision on a pedagogical level, shaping how compositionists and disciplinary faculty participate in CCL interactions. Thus, a revisionary approach leads me to conceptualize revisionary pedagogy for cross-curricular literacy work. I theorize revisionary pedagogy as a means of fostering pedagogical relationships in CCL contexts, complicating how relationships are framed in traditional Writing Across the Curriculum/Writing in the Disciplines scholarship. The literature advances three main conceptual models of CCL, each of which embraces expertise, change, and outcomes in ways that sponsor potentially problematic relationships between compositionists and disciplinary faculty. I draw on Composition scholars’ rich conceptualization of revision (Jung; Lee; Welch) and pedagogy (Kameen; Qualley; Stenberg) to challenge the litany of next-best models and imagine alternative possibilities for relationships in CCL contexts. Revisionary pedagogy is a means of approaching material circumstances that reconstitutes how compositionists and disciplinary faculty conceive of and participate in CCL relationships.

CONTROLLING YELLOW-BILLED MAGPIES (Pica nuttalli)

The yellow-billed magpie is a little smaller than the American or black-billed magpie, but the difference in size is very slight. The birds look exactly alike, except one has a black beak and the other has a yellow bill and a bit of yellow skin back of the eye.There are concentrated populations in the Los Banos area, Gustine area, and along the course of the Merced River comprising about 19,100 acres. They are occasionally seen in other areas of the County, but only infrequently observed in the southwestern portion of the County. The heaviest populations are in walnut orchards, dairy farms, almond orchards, turkey ranches and areas adjacent to river bottoms.The yellow-billed magpie may represent a dying ancient race. Since scientific interest has been directed toward its habits and distribution, its range has become more restricted. There are reports that 50 or 60 years ago it was common in many places close to the Coast, where the observer would now look for it in vain. It inhabits only the interior of California west of the Sierra Nevada, chiefly in the Sacramento and San Joaquin Valleys. It haunts stock ranches, because food to its liking is usually plentiful in such places. When cattle and sheep are butchered the refuse attracts magpies. They gather about any dead animal. They feed on grasshoppers, worms and grubs, and of course always look for a reasonable supply of eggs.

ECOLOGICAL CONTROL OF BIRD HAZARD TO AIRCRAFT

The Canadian Wildlife Service has had twenty-five years experience with the problem caused by bird contacts with aircraft. I experienced my first bird strike, while flying as an observer on a waterfowl survey in August, 1940. Officers of the Service investigated bird problems at airports at Yarmouth, Nova Scotia, and Cartierville, Quebec, in the late 1940's. Those incidents involving gulls and low speed piston-engined aircraft caused minor damage to the aircraft but considerable disturbance to the operators. As aircraft speeds increased and airports became more numerous and busier the problem increased in extent and complexity. By 1960 it was apparent that the problem would grow worse and that work should be directed toward reducing the number of incidents. In 1960 an electra aircraft crashed at Boston, Massachusetts, killing 61 passengers. Starlings were involved in the engine malfunction which preceded the crash. In November, 1962 a viscount aircraft was damaged by collision with two swans between Baltimore and Washington and crashed with a loss of 17 lives. Those incidents focused attention on the bird hazard problem in the United States.