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    Proposal for a CCAMLR sponsored research survey to monitor abundance of pre-recruit Antarctic toothfish in the southern Ross Sea

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    S.M. Hanchet, S. Mormede, S.J. Parker and A. Dunn (New Zealand)

    The exploratory fishery for Dissostichus spp. has now been operating for 14 years in Subarea 88.1 and for nine years in Subarea 88.2. Associated research has led to an assessment of the fisheries potential yield, but a source of ongoing uncertainty in the stock assessment concerns recruitment dynamics. Although pre-recruit Antarctic toothfish fish are caught in various locations during fishing operations, different vessels catch different length classes in different locations and in different years, making it impossible to develop a consistent time series that would monitor trends in recruitment over time from the fishery. At its 2010 meeting, the Scientific Committee agreed that a time series of recruitments from a well designed survey could be a useful input into a stock assessment model and requested members develop a pre-recruit survey design. This paper develops a proposal for a CCAMLR sponsored research survey in response to the Scientific Committee request.
    We consider here the objectives of the survey, the target fish age and length classes to be monitored, appropriate survey strata size and location, the number of sets in each stratum required to achieve target c.v.s, and associated sampling methodologies. Further, we propose that the first survey be a pilot, with two main objectives:  

    (i)    To establish the feasibility of developing a time series of longline surveys to monitor 80–100 cm TL toothfish in parts of SSRUs 881.J and 881.L in the southern Ross Sea using standardised gear in a standardised manner; and
    (ii)    To carry out experimental depth stratified fishing in 500–600 m depth adjacent to the survey boundaries to establish the most appropriate depth strata for future surveys.

    We are submitting this proposal to WG-SAM for further evaluation as requested by the Scientific Committee (SC-CAMLR-XXIX, para 3.185). We are particularly interested in ways to improve the survey design, as well as additional work that could be undertaken to demonstrate the use of the results of such a survey in the provision of advice to the Scientific Committee.