Stockhausen, W.1,2 and M. Fogarty1
1Northeast Fisheries Science Center, NOAA Fisheries,
Woods Hole, MA 02543
2Woods Hole Oceanographic Institution,
Woods Hole, MA 02543
The biomass of major nektonic species on Georges Bank has undergone
dramatic changes since the 1960's under the direct and indirect
effects of fishing. To characterize the effects of these changes in
community structure on production at tertiary and higher levels, as
well as to identify species interactions that may confound future
recovery of currently depressed populations, a set of multispecies
models of fish community dynamics on Georges Bank is being
developed. Model parameters will be estimated using
temporally-smoothed estimates of absolute species biomass based on
the 40-year dataset of semi-annual bottom trawl surveys conducted by
NOAA's Northeast Fisheries Science Center. Catchability
coefficients used to scale the "raw" trawl survey data to estimates
of absolute biomass were derived from previous studies and a new
analysis of the survey data. Using these coefficients, time series
of absolute biomass were calculated for nine ecologically and
commercially-important species. An ARIMA-based smoothing algorithm
was implemented to reduce effects of sampling variability on
individual time series. Details of this process are discussed and
the resulting time series of absolute biomass are presented. The
multispecies production models will provide a dynamic framework
complementing the static energy budget also being developed. In
addition, the biomass estimates will be useful for estimating
production of the nekton in the static energy budget.
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