Fisheries Acoustics Research

Members of the FAR Lab work on a variety of topics. Often, we are working on more than one project at a time. Here are just a few of the topics that we have conducted research on previously.

Julian Burgos

My project consists on describing and simulating walleye pollock spatial and temporal patterns. Walleye pollock is a fish from the Gadidae family. It has a large role in food webs in the Bering Sea and Gulf of Alaska, and sustains a very large commercial fishery. Although large scale (>100km) distribution patterns are relatively well known from bottom trawl and acoustic surveys, patterns at smaller spatial (and temporal) have not received much attention. Quantifying mesoscale (0.1 - 10 km) patterns is important because many ecological processes, including predator-prey interactions, occur at these scales.

Acoustic surveys are conducted regularly by the Alaska Fishery Science Center (NOAA) to estimate the biomass of walleye pollock. The data collected during these surveys provide a synoptic view of the distribution of pelagic and semi-demersal species at a fairly high resolution (i.e. 20 m horizontal and 0.2 m vertical). If these data are displayed in echograms, different distributions patterns are evident, including schools, large pelagic shoals and benthic shoals or 'carpets'. I use echo-trace classification and landscape ecology indices to obtain quantitative metrics of spatial pattern and to develop a classification typology for spatial patterns. I also use statistical methods like geostatistics and generalized additive models to explore the relationship among spatial patterns and between pattern and environmental variables.

I am also developing an individual based simulation of walleye pollock. In this simulation individual fish behave socially, gathering with other individuals to form aggregations, and reacting to environmental cues (temperature, light, bottom topography and food “patchiness”). The objective of this simulation is to generate realistic walleye pollock spatial and temporal patterns. This will help us understand how these patterns are generated. In addition, the simulation will generate prey fields to be used as input in marine mammals predation models.

This research has been sponsored by the Alaska Fisheries Science Center.

---

Sandy Parker Stetter

Forage species such as myctophids, bathylagids, and squid are important in apex predator diets in the Bering Sea. Lack of information on nekton species composition, density distribution, and movement reduces our ability to understand the role these species play in the ecosystem. In the Bering Sea, many of these important species are not assessed.

This project surveyed nekton in the shelf and slope region of the Bering Sea near Unalaska and Akutan Islands using multiple gear types (acoustics, midwater trawl, MultiNet, LIDAR). Researchers from University of Washington, NOAA, University of Alaska Fairbanks, and Louisiana State University are collaborating on this study. Acoustic analyses from this survey will allow us to characterize nekton spatial and temporal distribution and species composition. Our work will identify strengths and weaknesses of an integrated survey approach.

You may also look at a PDF of a poster(4MB) from this project.

This research has been sponsored by the North Pacific Research Board

---

Doojin Hwang

I am Doojin Hwang and come from Korea, the College of Fisheries and Ocean Science in Yosu National University in Korea. I am a visiting scholar until August 2006 at the University of Washington.

Bottom trawl and acoustic surveys were conducted around the south sea of Korea and East China Sea, to investigate distribution of fish and zooplankton. We know that many jellyfish lived in the area and are increasing every summer. It is necessary to know their density distribution, habitats and movement patterns, and to observe changes.

We measured in situ target strength of jellyfish in a seawater tank and obtained ex situ target strength data in the ocean. We will now compare empirical measurements and backscatter model predictions of jellyfish target strengths.

This research has been sponsored by the Yosu National University, University Visiting Program.

---

Patrick Adam

I am interested in the time and scale dependent patterns of abundance for both nekton and plankton species. Current methods for evaluation of abundance and dispersion include trawl and acoustic surveys. Problems inherent in acoustic analyses include the slow speed with which the survey is conducted resulting in a poor estimate of the temporal variation of these animals. Ship avoidance behavior of nekton species will also affect abundance estimates. Acoustic surveys typically miss the upper 10 meters of the water column, or less if using a towed-body transducer, which potentially eliminates a significant portion of the biomass depending on species of interest. Incorporating the use of an aircraft mounted Light Distance And Ranging (LIDAR) sampling platform may minimize these limitations and provide key insight into movements of fish schools and plankton over hourly time series. Unlike acoustics, LIDAR is capable of detecting fish and plankton in the surface waters.

Laser light is used much like sound from a sonar device and can detect the presence and distance of objects in the water, but is limited to about 50 meters depth. Because this instrument is mounted on an aircraft instead of a ship it can survey considerably more area in the same span of time as ship based surveys. My research will compare both sampling techniques to understand the effects of survey speed on abundance estimates and also the extent of ship avoidance of fish using coincident spatial and temporal surveys.

This research has been sponsored by the National Oceanographic Partnership Program (NOPP).

---

Patrick Nealson

The Alaska Department of Fish and Game (ADF&G) has used split-beam acoustic techniques to estimate adult salmon returns on the Kenai River since 1986.  Chinook salmon are of primary management concern, but acoustic counts are confounded during periods when large numbers of smaller sockeye salmon are present.  Controlled acoustic measurements of known tethered chinook and sockeye were collected in 2002.  Echo data were digitally-sampled and processed to determine if unique acoustic metrics existed that were correlated with salmon species, length or morphology.  Individual echo returns from known fish were measured and described using echo envelope width, phase variability, correlation coefficient and fractal dimension descriptors to assess their relative information content, as determined by the percentage of salmon correctly identified as to species.

The width and ping-to-ping variability in width of echo returns from chinook salmon were both observed to be significantly greater for chinook salmon than for sockeye. Presumably this was due to the physical width of the chinook exceeding half of the broadcast echo pulse width at certain orientations. Other observed echo characteristics indicative of chinook salmon included greater variability in range between successive ensonifications and multiple echo returns from a single transmitted pulse. Echo envelope width measurements within individual fish were determined to be least variable at the -3 dB power point, closer to peak amplitude than traditionally measured. These attributes will be considered during future annual acoustic assessments of Kenai River salmon passage, with the goal of accurately estimating species-specific (chinook) returns using exclusively acoustic sampling methods.

This research has been sponsored by the Alaska Department of Fish and Game

---

Steve Barbeaux

Commercial fishing vessels have long been used as sampling platforms for scientific studies and many national, state, and provincial agencies contract fishing vessels to conduct scientific research to support fisheries management objectives.

Echosounders capable of collecting scientific quality acoustic data have recently become available to the commercial fishing industry and researchers around the world have begun to use acoustic data collected from commercial fishing vessels in a broad range of fisheries research applications (Stanley 2000; Dorn et al 2002; Barbeaux et al 2005; O’Driscoll and Macaulay 2005). In the North Pacific the use of scientific quality echosounders by the Alaska pollock (Theragra chalcogramma) fishing fleet has provided an opportunity to collect acoustic data opportunistically during normal fishing operations. Collecting opportunistic acoustic data from commercial fishing vessels allows researchers to inexpensively obtain data from multiple platforms during a single time period.

The costs of collecting acoustic data opportunistically is restricted to the price of the digital media used to record the data (~$220 US for 120GB), and the staff time to install and collect media from the vessels. A multiple platform approach potentially offers a more synoptic view of a population than a survey conducted on a single vessel. Although opportunistic data are not collected on a systematic grid and may not be used to obtain population abundance estimates directly, the broad temporal extent and high spatial resolution of the opportunistic data may facilitate investigations on the distribution and behavior of fished aggregations. Due to the unstructured “sampling design” and the multiple platforms from which these data are collected there are significant challenges to its use as a quantitative tool for fisheries managers. The project I am working on will investigate the appropriate use of these data and develop methods for over-coming obstacles intrinsic to this potentially valuable data source.

This research has been sponsored by the Alaska Fisheries Science Center.

This research has been sponsored by the Alaska Department of Fish and Game

---

Karl Gjelland

My connection to fisheries acoustics research is through the study of ecological interactions in freshwater pelagic food webs. I’m using acoustics to reveal fish density, distribution and activity throughout the day and season. Mobile downlooking and sidelooking echosounding provide larger-scale distributional patterns, and stationary uplooking sounding provide information about the activity patterns of undisturbed fish. In addition, acoustic tags attached to piscivore fish give information about predator distribution and activity. When combining these data with data from biological sampling, we are able to evaluate models of planktivore foraging and predator avoidance models.

Ecological interactions are often highlighted when disturbances to a system changes the equilibrium, such as during a species invasion. Working in a freshwater pelagic community recently disturbed by an invading vendace population, my research is focused on the behavioural interactions between zooplankton, planktivorous fish and piscivorous fish in this system. By combining mechanistic foraging and predator avoidance models, I want to provide tools for simulating realistic individual behavioral decisions. The ultimate goal is to elucidate coexistence/exclusion between competing species, incorporating both predator effects and exploitative competition effects. The location at 69 °N implies a large change in light regime throughout the summer, providing a possibility to distinguish between the effects of light, circadian rhythms, and species interactions.

I’m currently staying at the FAR Lab and the University of Washington as a visiting scholar from the University of Tromsø, Norway.