TransAtlantic Studies of Calanus

## TransAtlantic Studies of Calanus (TASC) Working Group

### by Charles Miller

GLOBEC International now has offspring. The baby was born on the 7th of April 1994 at Oslo, Norway. Its name is the TransAtlantic Study of Calanus Working Group. In October it was recognized by ICES, which included TASC activities as a function of the ICES Zooplankton Productivity Working Group under Heine Rune Skjoldal. Attending the birth in Oslo were 25 scientists from Norway, Sweden, Denmark, Germany, Scotland, England, The Faroes Islands, Iceland, France, Canada and the United States. We were hosted by Stein Kaartvedt of the University of Oslo for a GLOBEC/ICES workshop designed to foster cooperation in the study of Calanus finmarchicus all across its North Atlantic range from New England to Northern Norway. Convenors were Kurt Tande of the University of Tromso and myself. Funding for the workshop came from the Norwegian Research Council, the European Union, the U.S. GLOBEC Office, and from marine research programs of several nations. Everyone attending is actively working on the biology of C. finmarchicus.

In preparation for the workshop, most of the participants wrote manuscripts on a wide range of topics, including distribution, feeding, growth, reproductive rates, genetics, the resting stage and methods for mortality estimation. Everyone received those in advance so that we arrived prepacked with relevant information, not to mention points to argue with erring authors. Our first day was spent presenting and discussing those papers, then celebrating our new (or renewed) acquaintance in one of the world's most expensive restaurants (which cluster in Oslo). Many of the papers have been revised after the meeting and are in review for publication together as an issue of Ophelia. The second day we spent on both plenary and working party debates about the priorities for research on C. finmarchicus. An amorphous mass of prose was produced which was later hammered into a report to ICES by Kurt Tande. We divided the discussion and report into four themes, which I list here with precis of the conclusions about each.

### I. The Interplay between Generation Cycles and Large-Scale Circulation Patterns in Oceanic and Shelf Areas.

Calanus finmarchicus is a prominent component of shelf zooplankton during late winter and spring in sites like the Northern North Sea and Georges Bank. However, it seems to be entirely missing from those regions in summer and autumn. Thus, the abundant stocks of winter-spring must be imported by advection from oceanic areas where resting stocks at depth maintain the species existence through the late summer and autumn. It was recommended as a priority that we work out the population budgets for several of these exchanges. This will allow us to distinguish between several alternative population histories. Are the resting stocks in oceanic sectors strongly dependent upon production over the shelves? Or, are the resting stocks produced entirely in the oceanic sector and simply "feeding" the shelf production with no strong return.

For the North Sea shelf an interaction between late winter inflow in the Faroes-Shetland Channel and upward ontogenetic migration of maturing Calanus have been suggested by Jan Backhaus, Mike Heath, Katherine Richardson and others as a supply mechanism. That will be the subject of an European Union Marine Science and Technology study during early 1995. The U.S. GLOBEC Georges Bank program is tackling a similar problem on the west side of the Atlantic.

### II. Strategies of Diapause and Reproduction

The control of entry to and emergence from diapause are not well understood for any species of Calanidae. We produced several recommendations aimmed at producing clues about the control mechanims:

- TASC projects should select an indicator of diapause condition [gonad development, jaw facies, enzyme status] and trace its appearance in Calanus stocks as function of season, temperature history, depth and photoperiod.

- TASC projects should sample resting stocks for stage composition [which varies] over at least several years. Basic habitat data, particularly water column temperature patterns, should be recorded through the period prior to and during diapause phases.

Laboratory studies were also recommended. Reproduction in C. finmarchicus has been a very active area of research recently. The TASC recommendation was that this effort be sustained.

### III. Population Coherence and Latitudinal Impact on Growth Patterns

- We recommended evaluation of the diversity of the C. fimarchicus stock across its range by studies of its molecular genetics.

- A renewed study of the growth response to food, temperature and other habitat factors is needed. Sophisticated data are available for related species, but not C. finmarchicus.

### IV. Trophic Interactions and Mortality

From a practical standpoint (support for our studies) we need to establish whether interannual variability in fishery recruitment depends directly upon variations of Calanus productivity. It may be hard to believe that isn't established, but it's not.

Mortality rates are almost always unconstrained tuning variables in our models of Calanus population processes. It was recommended that TASC projects should invent and adopt strategies for determining the partitioning of mortality among the developmental stages of C. finmarchicus cohorts.

On our third and final day, we decided to appoint ourselves as a long-term working group to continue communication about research on Calanus finmarchicus all across its range. We also hope to promote cooperative studies among laboratories and scientists so that knowledge of Calanus biology can increase at the fastest possible rate. We warmly invite anyone not at the workshop to join in this effort. We are the TransAtlantic Studies of Calanus (TASC) Working Group. I am the initial chair for interchange of information, principally through a newsletter. Yes, another newsletter. Issues No. 1 and 2 have been distributed to members. Copies can be obtained by writing (use email) to me. We also have an internet mail list and internet reflector address so that members can communicate rapidly with the entire group. We hope that will be useful, not another source of electronic junk mail. (Charles Miller is Professor of Oceanography at the College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331-5503, Internet: cmiller@oce.orst.edu)