Potential growth of pelagic juvenile cod in relation to the 1978-2006 winter-spring zooplankton on the Northeast US continental shelf
Authored by Trond Kristiansen, R G Lough
Date Published: 2015
DOI: 10.1093/icesjms/fsv145
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Abstract
Environmental conditions during the pelagic juvenile cod period
determine their fitness to survive settlement as demersal juveniles
(0-group) and recruitment. This study examines the potential growth of
pelagic juvenile cod in five areas of the New England Shelf based on
time series of zooplankton and ocean temperature from surveys. An
individual-based model was used to estimate the temporal variation in
growth of juvenile cod at each survey station based on available prey of
appropriate sized copepods of Calanus finmarchicus, Pseudocalanus spp., Centropages typicus, and Centropages hamatus. Mean juvenile cod growth
was low(1-7\% d(-1)) during January-February and March-April time series
across all areas, Gulf of Maine (GOM), Eastern Georges Bank, Western
Georges Bank, southern New England to Middle Atlantic Bight (MAB).
Growth increased significantly in May-June with the seasonal increase in
copepod density and temperature generally from South to North. The
1990-1999 warm years had the highest growth of 12-14\% d(-1) compared
with the cooler 2000-2006 years and colder 1978-1989 years of similarly
lower growth of 8-11\% d(-1). Growth in the MAB stayed the same 13\%
d(-1) as in 1990-1999, whereas GOM growth decreased significantly to
similar to 6\% d(-1). High prey densities during May-June 1990-1999 for
Georges Bank and GOM, followed by a strong decrease in 2000-2006 may
explain the decrease in growth during the same periods. While all four
copepod species contributed to potential growth, C. typicus, a more
southern species, could be the more important prey for juveniles in the
coastal areas during all months in contrast to Pseudocalanus spp. for
the larvae. Centropages typicus also is the most adaptable and likely
species able to expand and thrive under warmer climatic conditions, which could be of significance to future recruitment. Age-1 recruitment
for Georges Bank cod was found to be related to juvenile growth.
Tags
Regime shifts
Habitat selection
Spatial-distribution
Georges-bank
Gadus-morhua
Haddock melanogrammus-aeglefinus
Copepod populations
Atlantic
cod
Centropages-typicus
Larval cod