We build on previous research describing correlative links between changes in the abundance of the copepod Calanus finmarchicus, a foundational zooplankton species of the pelagic food web, and diminishing recruitment of young-of-year lobster to benthic nurseries in the Gulf of Maine.  First, we provide photographic evidence confirming that lobster larvae can handle and readily consume C. finmarchicus. Then, using parallel 31 year time series of lobster larvae and zooplankton collected on the New Hampshire coast between 1988 and 2018, we investigated how changes in phenology of stage I larval lobster and their putative copepod prey, Calanus finmarchicus, affects their temporal overlap and potential to interact.  We found that over the time series both lobster egg hatch and the first appearance of larvae trended earlier in the season, a trend significantly correlated with ocean warming. The last appearance of larvae in late summer has been delayed, however, thereby extending the larval season. Even with the longer larval lobster season, the C. finmarchicus season has increasingly been ending before the peak abundance of stage I lobster larvae. The net effect is a widening mismatch in phenology of the two species, an outcome consistent with the hypothesis that changes in abundance and phenology of C. finmarchicus have contributed to recent declines in lobster recruitment.

Primary Presenter: Joshua Carloni, NH Fish and Game (joshua.t.carloni@wildlife.nh.gov)

Authors:

Joshua Carloni, NH Fish and Game Department  (joshua.t.carloni@wildlife.nh.gov)

Richard Wahle, University of Maine  ()

David Fields, Bigelow Laboratory for Ocean Sciences  ()

Paul Geoghegan, Normandeau Associates, Inc.  ()

Burton Shank, NOAA National Marine Fisheries Service, Northeast Fisheries Science Center  ()