CCAMLR

We reanalysed 16 groundfish surveys at South Georgia to determine whether recruitment data used by the Working Group for toothfish assessments in 1999 and later were correct. We found several unexplainable errors. A new, corrected, series of recruitment estimates was derived using new procedures and 6 strata (3 depth strata each at Shag Rocks and South Georgia). It is easy to spot, visually, the modal progression of peaks in the length densities corresponding to cohorts assessed by sequential surveys. Length based analysis of these confirms the growth rate expected from the CCAMLR growth equation for South Georgia. Although it is easy to spot cohorts, the size of individual cohorts can not be consistently determined from the survey data. The expected reduction in cohort density with time at a log-scale rate of -0.16 (natural mortality) was evident in only very few cohort plots, even those which were particularly obvious as visual modal progressions, and even when the data were trimmed to remove suspect surveys. We conclude that survey-based estimates of recruitment biomass are not reliable input data for assessment models using the GY approach at South Georgia.

These are the technical specifications of the software Fish Heaven: version 2.1.5. The specifications include a description of the object structure of the model, the process structure of the model and a mathematical description of the model.

At its 2003 meeting, WG-FSA recommended that investigations be undertaken to determine whether the method for estimating catches from illegal, unregulated or unreported (IUU) fishing developed by Agnew and Kirkwood (2002) for Subarea 48.3 could be applied to other CCAMLR areas (SC-CAMLR-XXII, Annex 5, paragraph 3.18).
The results of these simulations suggest that more information on IUU fleet dynamics, particularly evasion tactics, will be necessary to devise an observation strategy for estimating the number of IUU fishing days, particularly for areas where patrolling may be relatively infrequent or prone to evasion. Also, the assessment method may need to be refined to take these issues into account.
An important consideration for the future will be the inevitable tension for fishery patrol vessels between detecting IUU activity, thereby estimating the number of IUU fishing days, and deterring such activity. For assessment purposes, this highlights a general problem that the method of observation has a strong effect on the behaviour of the system (of the illegal fishing cruises). It may be necessary to develop other forms of observations to facilitate this task.