A statistical method for analysing the extent of IUU fishing in CCAMLR waters: application to Subarea 48.3

1. This paper describes a new method for estimating IUU catch of fish and birds. It utilises high quality, well-documented FPV (fisheries protection vessel) cruise data. It takes explicit account of both “seen” and “unseen” IUU fishing through a simulation model to arrive statistically rigorous estimates and confidence intervals of fish and bird catch by IUU vessels. This method has not been used previously to estimate IUU activity in CCAMLR. We recommend its continued use in Subarea 48.3 and extension to other regions of the Antarctic.
2. Of the sources of information on IUU fishing, Fishery Protection Vessel (FPV) cruises are the most consistent and reliable. The track of the FPVs on their cruises to South Georgia covers all possible areas of fishing for toothfish in Subarea 48.3. The method uses data from FPV cruises in Subarea 48.3, and the encounters between FPVs and IUU fishing activity, to estimate the total number of days of IUU fishing that could occur during each year. For each IUU incident detected by the FPV, we calculated a theoretical maximum time over which this IUU activity could have occurred. This was the time that elapsed between the FPV cruises that were immediately prior to and immediately subsequent to the incident, where these prior and subsequent cruises had not detected that same IUU activity (i.e. the same vessel). In other words, for each IUU incident we know when it was seen, and the closest adjacent times in which it was not seen – the difference being the theoretical maximum time that the vessel can have been present.
3. This theoretical maximum time was converted to actual IUU fishing time using a simulation model. For each year, the model simulated 1000 IUU fishing incidents during the year, and from the known FPV cruise pattern calculated both the observed IUU activity and the known real IUU activity. We considered IUU activity to have been observed when the IUU vessel and the FPV vessel were in the same place at the same time. When this occurred, the FPV was assumed to detect IUU activity according to an “encounter probability”. The encounter probability was estimated from the known encounters of FPV with licensed vessels. Thus for each encounter between an IUU vessel and an FPV we obtained an estimate of total IUU fishing time.
4. The total annual IUU catch of toothfish and birds was calculated using a second simulation model. Subarea 48.3 was divided into 6 Areas for the purposes of calculation of fish and bird catch associated with IUU fishing. The catch rate of fish was calculated for each Area and each year using reported catch and effort data. The catch rate of birds was calculated separately for summer and winter using previously published CCAMLR observer data obtained in the early licensed fishery (1997) when few vessels used mitigation measures. For each of 10,000 simulations fish and bird catch rates were obtained randomly from parent distributions, for each IUU-FPV incident.
5. Three years were analysed, 1998/99, 1999/00 and 2000/01. Each year covered fully the period 1 October – 30 September, thus including one summer and one winter period. The estimated total toothfish catch attributable to IUU fishing was 667 t, 1015 t and 196 t in 1998/99, 1999/00 and 2000/01 respectively (a total over the three years of 1879 t). The estimated total bird catch was 574 birds, 2200 birds and 544 birds respectively. 95% confidence limits were calculated to be 41-1778, 472-1744 and 23-481 respectively for fish and 122-1823, 825-5422 and 110-1813 respectively for birds... [Please contact the Secretariat for the full abstract.]