Estimating krill recruitment and its variabiliity

A maximum likelihood method is developed for the decomposition of krill density at length data into the proportion of recruits in population sampled in a net haul survey. Preliminary results from a series of 5 net haul surveys in the South Atlantic and the Indian Ocean sectors of the Southern Ocean give a mean recruitment rate for one year old krill of 0.339 with a standard deviation of 0.100. The corresponding results for two year old krill from 9 surveys are 0.552 and standard deviation 0.074. A number of the assumptions needed for reliable results are discussed.