Meise Report

### Life History Patterns of Calanus finmarchicus and Pseudocalanus spp. in the Gulf of Maine: Effects of temperature and water column structure.

    INVESTIGATORS:

    C. Meise
    NOAA/NMFS
    28 Tarzwell Dr.
    Narragansett, RI 02882
    (401)782-3278
    cmeise@whsun1.wh.whoi.edu

    W. Morse
    Howard Marine Lab
    NOAA/NMFS
    Highlands, NJ.
    wmorse@wahoo.sh.nmfs.gov

    J. Green
    NOAA/NMFS
    28 Tarzwell Dr.
    Narragansett, RI 02882
    (401)782-3240
    jgreen@fish1.gso.uri.edu

    E. Durbin
    University of Rhode Island
    Graduate School of Oceanography
    Narragansett, RI
    (401)792-6807
    edurbin@gsosun1.gso.uri.edu

    GRANT PERIOD:  July 1993-October 1995

#### OBJECTIVES:

There are currently 10 years of archived small mesh (53 and 164 um ) zooplankton samples collected by NMFS during 1977-1987 under the Marine Monitoring and Prediction (MARMAP) program. These samples in conjunction with the already sorted larger mesh (333 um) samples provide an opportunity to:

1. establish a time series and reference points for the life history stages of Calanus finmarchicus and Pseudocalanus spp.

2. examine the results of (1) in the context of concurrent hydrographic conditions;

3. explore the interacting effects of hydrographic conditions, small mesh plankton abundance/production and larval fish abundance/production.

#### STATEMENT OF WORK:

In January 1995 sorting of a subset (300) of small mesh samples from two years (1979-1980) of MARMAP was completed. These samples provide almost monthly coverage of the younger life history (naupliar and copepodite 1-2) stages of Calanus finmarchicus and Pseudocalanus spp. on Georges Bank and in the Gulf of Maine. The zooplankton were collected with concurrent hydrographic and larval fish samples. These data will be analyzed together to establish any potential relationships between hydrography, larval fish and small mesh zooplankton. In addition these results are being related to the existing 10 year large mesh plankton dataset broadening their scope.

#### SUMMARY OF FINDINGS:

We have demonstrated the importance of the Gulf of Maine population of Calanus finmarchicus to the region both in terms of its overall higher abundance and its low variability. We have called into question certain geographic and temporal paradigms for this species and Pseudocalanus on Georges Bank. Particularly we have questioned the long held assumptions that C. finmarchicus and Pseudocalanus are as abundant on the center of Georges Bank as elsewhere in the region (they are lower) during spring production and our small mesh data have raised question to the long held belief that the regions C. finmarchicus population goes to resting stage in the late summer/fall. Our samples indicate that a small segment of this population does not. We have also demonstrated an increasingly negative relationship between C. finmarchicus and water column temperature as the hydrographic season progresses and life history stage moves toward adult.

We have also established the importance of major hydrographic currents and frontal areas on the distribution of these two species. Our small mesh data are not yet available on the GLOBEC database.

#### PUBLICATIONS/PRESENTATIONS:

Meise, C. J. and J. E. O'Reilly (accepted, Deep Sea Research). Spatial and seasonal patterns in abundance and age-composition of Calanus finmarchicus in the Gulf of Maine and on Georges Bank: 1977-1987.

Meise, C. J., J. E. O'Reilly and J. Kane. Spatial and seasonal patterns in abundance and age-composition of Calanus finmarchicus and Pseudocalanus spp. in the Gulf of Maine and on Georges Bank: 1977-1987. The Oceanography Society Meetings, Newport, RI. April 18-21,1995.