Research plan for toothfish in Divisions 58.4.4a and b by Shinsei Maru No. 3 in 2011/12

A tagging survey in SSRUs B and C in Division 58.4.4 a & b was initiated in the 2010/11 fishing season with the aims of providing the data required for assessments of the population structure, size, movement and growth of Dissostichus spp. in the centered area of Division 58.4.4 a & b. In the 2010/11 a total of 189 D. eleginoides were tagged and released in SSRUs B and C. Four tagged D. eleginoides, of which two fish were tagged and released in SSRU C during the 2007/08 and 2009/10 preliminary survey, respectively, were recaptured in the same SSRU. One allocated point in the northwest of SSRU C was not conducted due to deeper area than 2,000 m where the vessel cannot operate safely.

We propose to continue the mark-recapture experiment in SSRUs B and C in the 2011/12 season, with nearly same survey design as in the 2010/11. A total of 71 research hauls will be allocated in the same locations on 7.5-minute latitude x 15-minute longitude grid points except one haul which are newly allocated in the northeast of SSRU B instead of an unconducted haul in the 2010/11. To apply mark-and recapture studies, tagging rate of 5 fish / ton will be conducted. The comparison test with the experimental gear, which consists of three segments of Trot line system and Spanish line system respectively, will be conducted at 14 hauls, due to understanding of differences in the physical conditions of tagged fish between those caught on Spanish lines and those caught on trotlines. We propose 53 tonnes of total allowable sample size for the 2011/12, as in the 2010/11, taking into account the need for completion of the survey, which would provide a time series of catch rate data using identical methods.