University of Cape Town
MARAM_Tristan_2015_JUN_08.pdf (718.42 kB)

Recommendations on rock lobster TACs for the Tristan group of islands for the 2015/16 season.

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posted on 2022-02-28, 05:10 authored by Doug ButterworthDoug Butterworth, Susan HollowaySusan Holloway
OMPs have recently been accepted as the basis to recommend TACs for Inaccessible and Gough islands. Given that for Inaccessible and Gough the recent catch rates have been above the associated OMP’s target catch rate, the OMPs indicate increases to the TACs for both islands for the 2015 season:

Inaccessible: 73 MT to 77 MT
Gough: 100 MT to 105 MT

High catch rates continue at Nightingale, with the reasons for these remaining unclear. However, the possible negative impact on recruitment of the OLIVA oil spill is still to be felt in the fishery as those recruits have still to reach catchable size. Nevertheless projections are very positive in the longer term even with a future TAC of 75 MT, so that an increased TAC for the 2015 season is recommended:

Nightingale: 65 MT to 75 MT

A possible alternative and more precautionary approach would be to set the TAC at 65 MT when this season starts, with an increase to be considered in November based on decision rules (which would need to be developed) which will take the 2015 biomass survey and initial CPUE results into account.

The Tristan CPUE for 2014 is below the range anticipated in the testing of the OMP for that island, which leads to the recommendation to augment that OMP by an Exceptional Circumstances metarule, for which a specific suggestion is made. Under these provisions the extended OMP leads to a decrease in the TAC recommendation for the 2015 season: Tristan 161 MT to 153 MT. This reduction follows given the value for the standardized powerboat CPUE for 2014; this reflects a drop compared to 2013, but in contrast both the Edinburgh CPUE and the biomass survey show increases from 2013 to 2014. However, unless powerboat CPUE increases dramatically in the near future, substantial reductions in the Tristan TAC recommendations are to be expected for the 2016 and 2017 seasons.

As with Nightingale, a possibility if a more conservative approach is desired would be to set the TAC at a lower value than 153 MT when the season starts, with a review to be considered in November in the light both of further consideration of pertinent analyses, and/or of the further biomass survey and initial CPUE data available at that time. This would, however, require more substantial revision of the Tristan OMP in the interim.



Department of Mathematics and Applied Mathematics, University of Cape Town