Evelyn D. Brown

PREY RESOURCES, COMPETITION, AND GEOGRAPHIC STRUCTURE OF KITTIWAKE COLONIES IN PRINCE WILLIAM SOUND

Mostly indirect evidence has shown that the size of bird colonies is often related positively to the size of foraging areas, in turn an indirect measure of prey availability. We report here results of an unusual opportunity to directly investigate the relationships among the size and distribution of colonies of Black-legged Kittiwakes (Rissa tridactyla), the degree of overlap of colony-specific foraging areas, and the availability of kittiwake prey, principally Pacific herring (Clupea pallasi) and sand lance (Ammodytes hexapterus), in Prince William Sound, Alaska, 1995–1999. Aerial surveys to assess prevalence of prey schools visible at the surface (the kittiwake mode of prey search) allowed quantification of prey availability in foraging areas. Foraging areas and foraging ranges were determined by radio telemetry. Large colonies occurred as far apart as physically possible and not within foraging range (∼40 km) of one another; only small colonies occurred within the respective ranges of large colonies. F...

Communication in river otters: Creation of variable resource sheds for terrestrial communities

Movements and behavior of animals can result in transfer of nutrients between discrete spatial patches, leading to spatial and temporal variability in resource sheds, modification of nutrient cycling, changes in productivity and in community structure and function, and increases in landscape heterogeneity. In this study, we explored the function of scent-marking at latrines by coastal river otters (Lontra canadensis), through investigating spatial distributions of otters with respect to gender, sociality, and the distribution of their food resources. We then calculated the amounts of nitrogen (N) and phosphorus (P) transported to latrine sites based on otter foraging behavior and the function of scent-marking at latrines. Locations of 55 radio-tagged otters in Prince William Sound, Alaska, USA, were obtained through aerial telemetry over a period of four years. Data on fish densities and marine habitat features were concurrently obtained from scuba transects and aerial surveys. A plastic social organizati...

Field applications of the piscine anaphase aberration test: lessons from the Exxon Valdez oil spill

Several large-scale genotoxicity assessments have been performed in coastal marine areas that have demonstrated either localized or widespread genetic effects resulting from human activity. One common assessment method is the anaphase aberration test, a measurement of abnormal chromosome division, using embryolarval fishes. It can be used to detect the presence of mutagens within a poorly characterized complex mixture or monitor specific genotoxins and is easily adapted for laboratory screening. One comprehensive marine genotoxicity assessment was conducted using Pacific herring (Clupea pallasi) following the Exxon Valdez oil spill (EVOS) in Prince William Sound (PWS), AK in late March 1989. In early May, genetic damage was detected at many sites within the oil trajectory and was correlated with concentrations of polycyclic aromatic hydrocarbons characteristic of Exxon Valdez oil (EVO) in intertidal mussels. Effects were related spatially and temporally to oil exposure. Anaphase aberration rates decreased throughout May and June 1989, and by 1991, genotoxicity was undetectable. The abundance of the 1989 herring year class in PWS is significantly reduced; this is the first reported example linking genotoxicity to subsequent population level effects. This review describes the methodology for the anaphase aberration test using fish eggs, its applications for large-scale assessments and supportive laboratory studies, and its limitations for prediction of higher level effects on populations.

Airborne Remote Sensing of a Biological Hot Spot in the Southeastern Bering Sea

Intense, ephemeral foraging events within localized hot spots represent important trophic transfers to top predators in marine ecosystems, though the spatial extent and temporal overlap of predators and prey are difficult to observe using traditional methods. The southeastern Bering Sea has high marine productivity along the shelf break, especially near marine canyons. At a hot spot located near Bering Canyon, we observed three foraging events over a 12 day period in June 2005. These were located by aerial surveys, quantified by airborne lidar and visual counts, and characterized by ship-based acoustics and net catches. Because of the high density of seabirds, the events could be seen in images from space-based synthetic aperture radar. The events developed at the shelf slope, adjacent to passes between the Aleutian Islands, persisted for 1 to 8 days, then abruptly disappeared. Build-up and break down of the events occurred on 24 hr time scales, and diameters ranged from 10 to 20 km. These events comprised large concentrations of euphausiids, copepods, herring, other small pelagic fishes, humpback whales, Dall’s porpoise, short-tailed shearwaters, northern fulmars, and other pelagic seabirds. The lidar and acoustic remote sensing data demonstrated that prey densities inside the events were several times higher than those outside, indicating the importance of including events in forage fish surveys. This implies a need for either very intensive traditional surveys covering large expanses or for adaptive surveys guided by remote sensing. To our knowledge, this is the first time that an Alaskan hot spot was monitored with the combination of airborne and satellite remote sensing.

Combining Techniques for Remotely Assessing Pelagic Nekton: Getting the Whole Picture

A variety of observational techniques either have been developed or are under development for fisheries research. These techniques have greatly increased the quantity and quality of information that can be obtained from a research survey and it is anticipated that this trend will continue. Traditional ship-based surveys will be supplemented by data collected from fixed moorings, autonomous underwater vehicles, aircraft, and satellites. Each of these platforms is limited in the spatial and temporal scales that can be sampled. By combining data from multiple platforms and sensors, we will be able to obtain a more complete picture of the components of a particular ecosystem over a greater range of scales. This is particularly true for pelagic nekton, which can move independent of fluid motion. In many cases, the observational difficulties created by this mobility can be mitigated by the use of aircraft, which can cover large areas with optical instruments such as imagers and Light Detection and Ranging (lidar).