SS1.09 Fisheries Population Linkage Spatial and Temporal Variation in Zooplankton
Date: Wednesday, June 12, 2002
Time: 11:15:00 AM
Location: Carson C
LinkJS, National Marine Fisheries Service, Northeast Fisheries Science Center, Woods Hole, MA 02543, USA,
Kane, J, M, NMFS, NEFSC, Narragansett, RI 02882, USA,
Griswold, C, A, NMFS, NEFSC, Narragansett, RI 02882, USA,
Garrison, L, P, NMFS, SEFSC, Miami, FL 33149, USA,
Taylor, M, H, NMFS, NEFSC, Woods Hole, MA 02543, USA,
Mountain, D, G, NMFS, NEFSC, Woods Hole, MA 02543, USA,
Jossi, J, , NMFS, NEFSC, Narragansett, RI 02882, USA,
We compared trends in abundance of major planktivores on Georges Bank, the Atlantic herring (Clupea harengus) and the Atlantic mackerel (Scomber scombrus), with zooplankton abundance from the 1970s to present. Pelagic fish abundance declined in the late 1960s and early 1970s due to overfishing and did not begin to recover until the mid 1980s. In the 1990s Atlantic herring abundance exceeded abundance in any of the past thirty-five years. Total zooplankton numbers and biomass on Georges Bank declined from the 1970s to a low in the 1980s, and have subsequently increased in the 1990s. Examining zooplankton species composition revealed that the abundance of three major copepods, Calanus finmarchicus, Centropages hamatus, and Centropages typicus, similarly increased in abundance during the 1990s concurrent with the recovery of pelagic fish. There have also been long term changes in temperature on the Bank. Atlantic herring and mackerel food habits demonstrated an increase in the amount of copepods in the diet during the 1990s. Annual variations in oceanic conditions modulate the strength of spatial overlap (and hence predation) between zooplankton and these pelagic fish. We conclude that it is unlikely that Atlantic herring or mackerel regulate zooplankton populations or have altered the Georges Bank zooplankton community. Alternatively, it is probable that the increase in copepod abundance, in addition to less directed fishing pressure, may have helped pelagic fish recruitment, ultimately contributing to the currently historical high abundance of Atlantic herring and mackerel.