Numéro du document:
WG-EMM-09/25
Point(s) de l'ordre du jour
Résumé
- CCAMLR International Scientific Observer data collected from conventional trawl vessels fishing for krill in Subarea 48.3 were analysed using Variance Components Analysis. Krill mean and median length and larval fish bycatch were analysed.
- In Subarea 48.3, a partial coverage sampling programme has been implemented since 2002. Observers have been placed on approximately 50% of vessels fishing in any one season, and have been present on board for about 30% of the fishing season. They have achieved a rate of sampling equivalent to 18% of total hauls taken in a season being sampled for krill and 11% for larval fish.
- For both krill and larval fish between vessel variance was slightly lower than between haul variance, the between vessel variance being about 45% of total variance. However, the ratio is sufficiently close to 50% that sampling needs to be efficient at both vessel and haul level.
- We propose that an efficient sampling proportion, at least for 48.3, should be >50% of vessels sampled each season, 20% of total season hauls sampled for krill and an equivalent or higher sampling proportion for larval fish.
- The Scientific Committee’s method of systematic partial coverage appears to have been sufficient in subarea 48.3 to determine appropriate coverage levels in that fishery. The 48.3 data suggest that such strategies should be pursued for at least 4 years before the Scientific Committee will have sufficient data to determine appropriate sampling strategies.