RESOURCE ASSESSMENT & CONSERVATION ENGINEERING
(RACE) DIVISION (cont.)

Midwater Assessment & Conservation Engineering (MACE) Program

Members of the Midwater Assessment and Conservation Engineering (MACE) Program participated in a Simrad EK/ER60 acoustic system user meeting with Simrad representatives Lars Andersen and Jeff Condiotty at the Center on 19 November 2004. Scientists from the Northwest Fisheries Science Center, University of Alaska, University of Washington, Canada Department of Fisheries and Oceans, and Sonardata Ltd. (Australia) also participated. Lars Andersen summarized features of the latest Simrad ER60 software and responded to questions submitted earlier by EK/ER60 users.

Participants discussed: 1) potential improvements to the software;  2) results of comparisons between the older EK500 acoustic system and the new EK60;  3) test results from users that suggested an EK60 performance instability;  4) relative merits of different single target detection algorithms in scientific fisheries acoustic systems; and  5) other emerging technologies that Simrad is developing for fisheries acoustics applications. A summary report of the meeting is available to subscribers of a NMFS-sponsored EK60 user list server.

Alex De Robertis and Dan Twohig of the MACE Program participated in acoustic testing of the new NOAA fisheries research vessel, Oscar Dyson from 9 to 17 December. The Oscar Dyson has been designed and built to conform to international standards for underwater-radiated noise to minimize fish avoidance reactions to the vessel.

As part of acceptance testing prior to delivery, the Oscar Dyson underwent acoustic testing conducted by the U.S. Navy to confirm that the underwater-radiated vessel noise levels meet the design requirements. During the Navy noise tests, De Robertis took measurements from hull-mounted hydrophones to identify sounds produced by the vessel. These baseline hydrophone measurements were compared to vibration and far-field noise measurements made simultaneously at the noise range. They will be compared with future measurements to identify changes in the underwater-radiated noise signature produced by the Oscar Dyson over its service life.

By Taina Honkalehto

Recruitment Processes Program

In response to reports of extremely high numbers of age-0 juvenile walleye pollock caught during RACE summer acoustic surveys in the Chiniak Bay area of Alaska, scientists from the Recruitment Processes Program collaborated with the Shellfish Assessment Program to collect data from several fall 2004 cruises to look at the extent of the age-0 pollock distribution and collected samples to examine condition of these fish. The samples were obtained opportunistically because no fieldwork targeting juvenile pollock had been planned.

The first set of samples were obtained during a September cruise on the NOAA ship Miller Freeman from the inner continental shelf bordering the southern shore of Kodiak Island (5 tows) and in the vicinity of Sutwik Island (4 tows). The sample size was small, but there was no indication that the abundance of fish near Sutwik Island was large relative to catches at the same locations during September 2000, 2001, and 2003. The samples off Kodiak were collected by targeting echo-layers,which complicates comparisons with other data. However, there was no indication of anomalous fish size (mean standard length = 87 mm, range = 50117 mm).

The second set of samples were collected during the autumn shrimp survey conducted by the ADF&G. Ninety-two hauls were set in stations in Chiniak and Marmot Bays, Shelikof Strait, and bays along the Alaska Peninsula from Wide Bay to Sand Point. Approximately 300 fishes from 20 stations were collected, and 2,832 fishes from 73 stations were measured. Two large concentrations of age-0 pollock were found, one in Wide Bay and the other in Marmot Bay (Fig. 10 below). However, there was no indication that high abundances of age-0 pollock were widespread.

By Kevin Bailey, Matthew Wilson, and Michael Litzow

Figure 10.  CPUE of all juvenile walleye pollock in ADF&G shrimp trawl surveys. Age-0 analysis is in progress, but not expected to look different.  Map courtesy of Dave Jackson, ADF&G Kodiak.

AFSC Quarterly Research Reports Oct-Dec 2004