RESOURCE ECOLOGY & FISHERIES MANAGEMENT (REFM) DIVISION

U.S. North Pacific Groundfish Observer Program

Training, Briefing, and Debriefing Statistics
During the third quarter of 2002, 194 observers were trained, briefed, and equipped for deployment to fishing and processing vessels and shoreside plants in the Gulf of Alaska, Bering Sea, and Aleutian Islands.  They sampled aboard 227 fishing and processing vessels and at 14 shoreside processing plants.  These observers were trained or briefed in various locations.  The University of Alaska Anchorage Observer Training Center trained 25 first time observers and briefed another 59 observers with prior experience.  The AFSC Observer Program in Seattle trained 20 first-time observers and briefed another 67 observers who had prior experience.  Twenty-three observers were excused from briefing because they had just completed a cruise successfully and were returning immediately to the field.  The third quarter 2002 observer workforce thus comprised 23% new observers and 77% experienced observers.

The Observer Program conducted a total of 110 debriefings during the second quarter of 2002. Thirty-three debriefings were held in Anchorage, 1 in Kodiak, and another 75 in Seattle.

Proposed Rule
NMFS issued a proposed rule on 16 September 2002 that would extend the Observer Program through 2007 and amend the current regulations implementing the Observer Program.  The existing regulations for the Observer Program would otherwise expire at the end of this year.  (See AFSC Quarterly Report, April-May-June 2002 issue, for details.) After the public comment period ends on 11 October 2002, staff will be working on the Final Rule to implement the proposed regulatory changes with a planned effective date of 1 January 2003.

Observer Advisory Committee
The Observer Advisory Committee (OAC) of the NPFMC  met 18-19 July 2002 at the AFSC to discuss ways of restructuring the Observer Program to better meet the needs of NMFS, the fishing industry, observer provider companies and observers themselves.  Conclusions drawn from the OAC discussion are as follows:

• The funding mechanism for the Observer Program dictates to a large degree, the overall structure of the Observer Program and its service delivery model (SDM).  Therefore, creating real change in the Observer Program must first involve changing the funding arrangements.
  
• Full Federal funding of the Observer Program should be sought by NMFS and the Council as their preferred plan with a blend of Federal funding and fee collections as a secondary option.
  
• The goal for restructuring the Observer Program should be collection of better scientific data to support fishery management rather than eliminating the conflict of interest inherent in the current Observer Program SDM.  To achieve this goal, changes need to be made to the observer coverage requirements with particular attention to the vessels requiring 30% observer coverage and those vessels that carry no observers.

By Bob Maier.

Age and Growth Program

Alexander Buslov, a fishery biologist from Kamchatka, Russia, (KamchatNIRO), visited the Age and Growth Program 11-25 September  to share knowledge concerning the ageing of teleost fish using vertebrae.  Because of the difficulty of acquiring known-age fish for age validation, the program is looking for other methods to corroborate otolith ages.  Preliminary results indicate that vertebrae can be useful in supplying corroborative evidence in some species.

By Dan Kimura.

Status of Stocks and
Multispecies Assessment Program

Atka Mackerel Tagging
The fishing vessel Pacific Explorer was chartered from 10 June to 9 July 2002 for tag and release studies of Atka mackerel in the Seguam Pass and Tanaga Pass areas of the Aleutian Islands, Alaska.  The cruise represents the third consecutive year of work by the AFSC on Atka mackerel in Seguam Pass and the first year of work in Tanaga Pass.  The objective of these studies is to determine the efficacy of trawl exclusion zones as a management tool to maintain prey abundance and availability for Steller sea lions at local scales.  The purpose of the Pacific Explorer cruise in June-July 2002 was to tag and release Atka mackerel inside and outside the trawl exclusion zones in Seguam and Tanaga Passes. Trawl exclusion zones were established around sea lion rookeries as a precautionary measure to protect critical sea lion habitat, including local populations of prey such as Atka mackerel. Localized fishing may affect Atka mackerel abundance and distribution near sea lion rookeries.  Tagging experiments are being used to estimate abundance and movement between areas open and closed to the Atka mackerel fishery.

A feasibility study was conducted in 1999 at Seguam Pass.  In summer 2000, approximately 8,000 tagged Atka mackerel were released in Seguam Pass, and in 2001 approximately 1,000 were released during a truncated cruise.  Recovery of tagged fish is supplied by the fishery in the open areas outside the trawl exclusion zone.  Recoveries in the closed areas are provided by chartered recovery cruises.

Approximately 28,000 fish were tagged with plastic T-bar (“spaghetti”) tags in the Seguam Pass area; 21,000 were released inside the trawl exclusion zone, and 7,000 were released outside.  Approximately 14,520 were tagged near Tanaga Pass – 8,520 were released inside the trawl exclusion zone and 6,000 were released outside.  In addition to T-bar tags, several Atka mackerel were tagged with electronic archival tags, which record depth and time continuously.  The data can be downloaded from tags recovered from fish caught by commercial vessels or AFSC charters.  A total of 200 Atka mackerel were tagged with archival tags in the Seguam Pass area – 60 inside and 140 outside the trawl exclusion zone.  A total of 200 fish were tagged with archival tags in the Tanaga Pass area – 120 inside and 80 outside the trawl exclusion zone.

Tagged fish were randomly selected and placed into tanks to assess mortality rate following capture, handling, and tagging.  Experiments were conducted over two different durations, 48 hours and 4 days (96 hours).  Sixteen experiments were conducted over the course of the cruise.  Of the 315 fish included in the experiments, a total of 13 died, for a mortality rate of 4%.

In addition to tagging and releasing Atka mackerel, AFSC scientists collected length-frequency data and took biological samples that will provide information on age, growth, reproductive condition and diet.  Otoliths, gonads, and stomachs were collected from 10 males and 10 females from every successful haul for a total of  210 fish of each sex.  In addition to these samples, approximately 30 whole fish of each sex were frozen for future proximate analysis (fat, protein, water, and ash content).  These data provide information on the caloric value of Atka mackerel as prey for Steller sea lions.

AFSC scientists also collected physical oceanographic data with the goal of examining the water column characteristics of Atka mackerel habitat.  Continuous temperature and salinity data were collected with a sensor plumbed to receive water from near the surface.  Temperature-depth data were also collected with a microbathythermograph (MBT) mounted on the net used to catch fish for tagging.

By Libby Logerwell.

Fishery Interaction Experiment
REFM scientists participated in a fishery interaction experiment which was completed between 14 August and 5 September off the east side of Kodiak Island in the Gulf of Alaska. The cruise was part of an ongoing collaborative effort between RACE and REFM scientists.  The work is part of a larger program designed to evaluate the effect of commercial fishing activity on the prey availability of walleye pollock  and other forage fish species to endangered Steller sea lions.  For more information on this cruise see the complete report in the RACE/MACE section.   

By Chris Wilson and Anne Hollowed.

Stock Assessment Modeling Changes: Atka Mackerel
An application of a NOAA Fisheries Toolbox stock assessment model to Aleutian Islands Atka mackerel was presented for review at the September Bering Sea/Aleutian Islands groundfish plan team meetings.  The Stock Assessment Toolbox is the result of an initiative by the NMFS Office of Science and Technology dating back to 1998 and has been adopted in a number of stock assessment settings on the U.S. East Coast.  The Toolbox provides a user-friendly interface which facilitates construction of stock assessment models with AD Model Builder software and provides many improvements.  The conceptual model is similar to the stock synthesis application first developed for Aleutian Islands Atka mackerel in 1991.  Motivation for changing the software is primarily to use improved algorithms for estimation and better evaluations of assessment uncertainty.  A key feature is that the Toolbox readily calculates standard errors for model output.  The change from the stock synthesis application to the Toolbox application provides more flexibility in the estimation of the survey catchability coefficient, selectivity, and natural mortality.  Previously, these model parameters were difficult to explore in stock synthesis.  The Bering Sea/Aleutian Islands Plan Team concurred with the development and recommendation to use the Toolbox stock assessment model for this year’s Atka mackerel stock assessment.

By Sandra Lowe and Jim Ianelli.

Stock Assessment Modeling Changes: Arrowtooth Flounder
The arrowtooth flounder stock assessment for the year 2003 fishing season in the eastern Bering Sea and Aleutian Islands region will be conducted with a change of implementation software.  The AD Model Builder language is used to rewrite the established population dynamics model (used since 1995) in C++ computer language.  The model is a length-based approach where survey and fishery length composition observations are used to calculate estimates of population numbers-at-age by the use of a length-age (growth) matrix.

Motivation for changing to the AD Model Builder language comes primarily from a past attempt at modeling the shelf and slope survey population estimates which indicate that females are consistently estimated to be in higher abundance than males.  Females were also found in higher proportions in the Gulf of Alaska from triennial surveys conducted from 1984 to 1996.  This information was incorporated into the synthesis model by adjusting the size composition data inputs by the sex ratio proportion observed in shelf and slope trawl surveys and fishery data.  Unsatisfactory low estimates of male selectivity were obtained from these model runs which had the undesirable effect of artificially increasing population estimates.  These results were due to the assumption of equal proportions of males and females implicit in the synthesis model.  The AD Model software allows more flexibility in modeling sex-specific natural mortality.  The stock assessment for the 2003 fishing season will attempt to provide separate estimates of natural mortality for males and females.

By Tom Wilderbuer.

Adak Island Rockfish Submersible Study

Figure 1. A shortraker rockfish photographed during the REFM Division’s Adak Island rockfish submersible study.

REFM scientists conducted a study of shortraker (Sebastes borealis )and rougheye (Sebastes aleutianus) rockfish near Adak Island, Alaska, with the submersible Delta during 27-30 July.  Moss Landing Marine Laboratory assisted with the data collection. The goal of the study was to use line transects to estimate shortraker and rougheye densities and characterize habitat. A total of 12 dives and 39 transects were completed during the 4 days of sampling.  Each dive consisted of approximately three 20-minute transects during which an observer collected data on species identification, distance of fish from submersible, habitat type, and size of specimen. The dive locations were identified as shortraker and rougheye habitat from historical bottom trawl research surveys.  Line transects were then conducted at depths of 300-350 m. The four sampling days were divided between the north and south side of the Aleutian Islands.  A variety of habitats were encountered, ranging from flat, sandy areas to steep rocky outcrops.  An example of the latter type of habitat was the eastern portion of Adak Canyon (Fig. 1 above), where three dives were conducted. Each dive was videotaped using two cameras, and these tapes will be analyzed in order to estimate rockfish densities within the different habitat types.

By Paul Spencer and Rebecca Reuter.

>>>continued

AFSC Quarterly
Research Reports
July-Sept 2002