Appendix C. Fish Working Group Report

Chair: George Boehlert

Rapporteur: Charlie Miller

Participants: Johannes Kinzer, Don Olson, David Stein, Bernie Zahuranec

The group dealing with fish discussed the general lack of information available on pertinent species at higher trophic levels in the Arabian Sea. It is imperative that all literature and unpublished studies be drawn together to better refine any proposed research. Questions were raised about the source of prey, distribution and abundance, and ultimate fate of the most important species (assumed here to be Benthosema pterotum and Diaphus spp.).

General Themes and Specific Scientific Questions

Specific hypotheses were posed to serve as a focus of discussion, as follows:

General Hypothesis: The large stocks of myctophid fish and their high growth rates in the Arabian Sea are a function of regional physical conditions.

Specific Hypotheses:

Tests of these hypotheses will require sampling both the water column and the benthos using a variety of sampling gear. Water column sampling should be done with acoustics for biomass estimation, discrete depth midwater trawling for specimen collection and identification, and larval fish and plankton sampling. Bottom cores should be collected to examine present and historical myctophid abundance as reflected in otolith and/or scale deposits. To examine a wide range of physical conditions, stations should be located on the shelf, slope and in offshore waters. Sampling should be conducted monthly for at least one full year.

Several questions should be answered, including:

Equipment and Approach Recommendations

The working group discussed how to approach and undertake an extensive and thorough study of the midwater myctophids of the Arabian Sea. We agreed that more than one sampling technique should be applied to the estimation of stock size. For acquisition of specimens and data for the micronekton component, we recommend the following gear:

The ideal platform for deployment of these varied gear is a specially equipped dragger/processor ship, possibly chartered from the commercial fishing industry. Suitable ships are not fast, but have high power. In the U.S. suitable ships are mostly in service in the Bering Sea fishery.

The sampling schedule should include the following:

A central goal of ichthyological studies in the Arabian Sea U.S. GLOBEC work is full understanding of myctophid biology and basic ecology. To this end U.S. GLOBEC should support a number of biological studies. We recommend the following minimum list of program components:

The working group discussed the possibility that all expeditions to the Arabian Sea in the mid-1990's could be equipped with a sophisticated, recording echo integrator system for low frequency (ca. 38 kHz) records of fish abundance. Possibly data could be gathered in a nearly automated fashion and analyzed by U.S. GLOBEC fish program investigators. The WOCE representative present at the meeting emphasized the "not to interfere" basis that would be enforced by investigators from other programs. It was also suggested that calibrated ADCP instruments might make useful records. In general the frequency of these is too high to be useful for evaluation of fish abundance and distribution, but the records of zooplankton abundance would be useful for the overall U.S. GLOBEC research program.


We recommend that a dedicated ship be requested by U.S. GLOBEC for nekton and plankton research. A dedicated ship is needed in order to ensure adequate sampling (e.g., number, duration and location of stations). A Bering Sea type trawler-processor (135-150 ft) could be chartered for reasonable costs for 6-12 months to enable seasonal sampling along an inshore-offshore transect and geographic surveys. Such a vessel would be capable of working in high wind, rough sea states typical of the region for much of the year. It would be able to accommodate 12-15 scientists and provide ample laboratory space. The ship would include state-of-the-art acoustics and it would have the ability to tow large midwater trawls double warp. It would include a deck crane suitable for moving and deploying small gear, and it would be fitted with a third wire or an acoustic net monitor.

Modifications to the vessel would be installation of a hydrowinch (and A-Frame?), an echo integrator, and a running sea water system. Meteorological deck sensors, modern communications and satellite downlinks, and SAIL systems would be desirable. It would have to be airconditioned.