There is an urgent need to determine the relationship between pre-recruit stages from the different stocks of adult pilchards amongst regions of southern WA. In particular, whether pre-recruits which originate in each region largely remain separate or mix together needs to be determined. Following this, knowledge on the rates of mixing of pre-recruits should be investigated so that the relative contribution from any one region to any other region can be estimated.

The key issues which need to be addressed are:
1. Do specific pilchard nursery areas exist?
2. Do recruits to each region come from a common pool of pre-recruits (e.g. one year olds)?
3. Is there significant eastward and or westward movements of pre-recruits between zones?
4. Does each zone of the fishery contribute similar numbers of recruits or is one zone (or two) more important than other(s)?

Because of the extent of the gap in our knowledge of pre-recruit pilchards this proposal is only for a 15 month pilot study. If results from the pilot study are encouraging, once the initial questions have been addressed a second research proposal will be developed to investigate mixing rates in greater detail through a combination of further otolith analyses and tagging. Also, continuing advances in methods to compare mitachondrial DNA may also permit this method to be used to examine the question of origin of recruits.