Sandra L. Parker-Stetter

The diets of polar cod (Boreogadus saida) from August 2008 in the US Beaufort Sea

Polar cod (Boreogadus saida) play an integral part in the Arctic ecosystems linking the upper and lower trophic levels. Though their estimated biomass is considerable, recent knowledge of their diets in the US Beaufort Sea is sparse. Collections of polar cod from the US Beaufort Sea were made during August 2008 using demersal and pelagic trawls. Polar cod diet composition was quantified as percent prey weight, percent prey count, and frequency of occurrence of prey. The diet composition between the demersal- and pelagic-captured cod showed differences in all these categories. Polar cod captured in the demersal nets primarily fed on fish (by weight), and pelagic cod primarily fed on copepods (frequency of occurrence) and euphausiids (by weight). In general, these dominant preys are different than what has been reported in other studies describing polar cod diets.

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.

Vertical Distribution of Age-0 Walleye Pollock during Late Summer: Environment or Ontogeny?

Abstract Variability in the late-summer vertical distribution of age-0 Walleye Pollock Gadus chalcogrammus in the southeastern Bering Sea has been attributed to a range of physical and biological factors. Using acoustic data (38 and 120 kHz) collected during the 2010 Bering Aleutian Salmon International Survey (BASIS) and dedicated high-resolution surveys (HR1 and HR2), we evaluated whether late-summer distributions could be explained by water column properties (environment) or whether sampling was likely occurring during the ontogenetic shift of age-0 Walleye Pollock from near-surface habitat to demersal habitat (ontogeny). Neither water column attributes (temperature, relative temperature, salinity, dissolved oxygen, and density gradient) nor the acoustic density of zooplankton prey strongly predicted the acoustic estimates of age-0 Walleye Pollock vertical presence or density. At 6 of 10 paired BASIS—HR1 stations, age-0 Walleye Pollock shifted deeper in the water column between BASIS sampling and the HR1 sampling conducted 8–34 d later. There were no consistent differences in FL (P > 0.05 for 2 of 4 station pairs) or energy density (P > 0.05 for 3 station pairs) between age-0 Walleye Pollock caught in near-surface trawls and those caught in midwater trawls. Our data suggest that the observation of both near-surface and midwater age-0 Walleye Pollock during late summer is likely due to an ontogenetic habitat shift; however, the causative factor was not clear given the limited sample sizes and explanatory variables. The timing of the ontogenetic shift, which appears to have begun before August 18, 2010, can ultimately affect survey strategies, and knowledge of this timing can provide additional insight into factors affecting the overwinter survival of age-0 Walleye Pollock.

Development of a stereo camera system for monitoring hydrokinetic turbines

The implementation of a hybrid optical-acoustic imaging system is described and evaluated for environmental monitoring of a hydrokinetic turbine. This monitoring system is intended to provide real time stereographic imagery in the near field (≥10 m) of tidal turbines proposed for deployment in Admiralty Inlet, Puget Sound, Washington. Post deployment observations will provide valuable information about the frequency and character of interactions of marine animals with the turbine. Optical camera effectiveness is evaluated under realistic field conditions in order to determine the range within which it is able to detect, discriminate, and classify targets. These field evaluations serve to inform optimal system placement relative to the turbine. Preliminary assessment of image quality and measurements taken by the stereographic cameras show that it will likely be able to discriminate and classify targets at ranges up to 3.5 m and detect targets at ranges up to and potentially beyond 4.5 m.

Development of a stereo-optical camera system for monitoring tidal turbines

Abstract The development, implementation, and testing of a stereo-optical imaging system suitable for environmental monitoring of a tidal turbine is described. This monitoring system is intended to provide real-time stereographic imagery in the near-field ( < 10     m ) of tidal turbines proposed for deployment in Admiralty Inlet, Puget Sound, Washington. Postdeployment observations will provide the necessary information about the frequency and type of interactions between marine animals and the turbine. A method for optimizing the stereo camera arrangement is given, along with a quantitative assessment of the system’s ability to measure and track targets in three-dimensional space. Optical camera effectiveness is qualitatively evaluated under realistic field conditions to determine the range within which detection, discrimination, and classification of targets is possible. These field evaluations inform optimal system placement relative to the turbine rotor. Tests suggest that the stereographic cameras will likely be able to discriminate and classify targets at ranges up to 3.5 m and detect targets at ranges up to, and potentially beyond, 4.5 m. Future system testing will include the use of an imaging sonar (“acoustical camera”) to evaluate behavioral disturbances associated with artificial lighting.

Characterizing and monitoring marine nekton at Puget Sound’s renewable energy site.

Marine hydrokinetic energy sites have the potential to impact distributions, dynamics, and abundances of macroinvertebrates, fish, and marine mammals (i.e., nekton). Potential impacts include changes in aggregation, avoidance, and occurrences of strikes or impingements. Understanding potential impacts requires knowledge of species‐specific distributions over relevant spatial and temporal scales. Configurations and integration of technologies capable of providing images and data are not well‐established, and the application of monitoring technologies is complicated by extreme flows at marine hydrokinetic energy sites. An echosounder, multibeam sonar, and acoustic camera will be used to detect, categorize, and enumerate nekton at a proposed renewable energy site in northern Admiralty Inlet, Puget Sound, WA. This is the site selected by Snohomish Public Utility District for the deployment of two OpenHydro turbines. Data from stationary instrument deployments will be compared to data from a mobile acoustic an...

Influence of biophysical coupling on age‐0 pollock survey results.

Age‐0 walleye pollock relative abundance and distribution in the eastern Bering Sea has been characterized with data from a surface trawl survey [Bering Aleutian Salmon International Survey (BASIS)]. Based on surface trawl catches since 2003, age‐0 pollock abundances appeared to be highest during climatic warm years and lowest in cold years, with predictable distributions based on water column stratification. In 2008–2010, all cold years, acoustics, and midwater trawling were added to the BASIS survey. Acoustics confirmed that low numbers of age‐0 pollock were found in the surface waters, but revealed the presence of previously unsampled, large (over 50 m high, several km long) aggregations in deep (greater than 100‐m bottom depth) water. Acoustic and midwater trawling results suggest that the deep biomass may exceed that found in surface waters. Relationships are now being evaluated between oceanographic characteristics (water column stability, extent of the bottom cold pool) and biomass of age‐0 pollock...