"Straw2" OMP-08 under alternative recruitment scenarios
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2007
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University of Cape Town
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Abstract
The OMP under development is tuned using an underlying operating model based on the updated assessments. Serial correlation in both sardine and anchovy recruitment is therefore taken into account (with a 1-year memory) in alignment with that seen historically. For sardine this serial correlation was estimated for the “non-peak” years of 1984-1999,2005-2006. Given concerns that sardine recruitment may remain low for the near future, two robustness tests have been run on “Straw2” OMP-08. In the first test the serial correlation in November 2007 (producing recruitment in May 2008) and November 2008 (producing recruitment in May 2009) is increased for sardine. Given a below average recruitment in May 2007, this increases the chance of poor recruitment in the coming two years. In the second, more pessimistic, case the recruitment in November 2007 and 2008 was set equal to that in November 2006.
Data from the FIMS surveys carried over the period 1993 to 2009 have been re-analysed here. This reanalysis was necessary because verification of the data resulted in several corrections. These corrections mainly involved differentiation of records that had a zero catch associated with them when in fact the trap had been lost or open or not set. The total area of each Zone as well as the area for each transect surveyed was also re-calculated (see van Zyl et al., 2009). The allocation of stations to hotspot areas changed in some cases from that in previous analyses. Changes in methodology in calculating abundance indices has also been changed slightly. It should be noted that the results presented here are still preliminary.
Data from the FIMS surveys carried over the period 1993 to 2009 have been re-analysed here. This reanalysis was necessary because verification of the data resulted in several corrections. These corrections mainly involved differentiation of records that had a zero catch associated with them when in fact the trap had been lost or open or not set. The total area of each Zone as well as the area for each transect surveyed was also re-calculated (see van Zyl et al., 2009). The allocation of stations to hotspot areas changed in some cases from that in previous analyses. Changes in methodology in calculating abundance indices has also been changed slightly. It should be noted that the results presented here are still preliminary.
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Reference:
Cunningham, C L., & Butterworth, D. S. (2007). "Straw2" OMP-08 under alternative recruitment scenarios. MARAM: University of Cape Town.