The spatial extent of the NPF has changed over time and now concentrates on relatively small hotspots. This means that the only index of biomass, CPUE (derived from fishery log book returns), is providing little information on the areas no longer fished (including inshore areas that generally have been closed to fishing). However, stock assessment estimates for banana and tiger prawns need to take into account the abundance of prawns in all areas, including those not fished.

Although recent research has suggested that inshore waters are probably the most important spawning areas in the NPF, this conclusion is based on laboratory research on the behaviour of postlarval prawns, combined with models of the currents in different regions of the NPF. To validate this conclusion we need to confirm that substantial populations of spawners do occur in the inshore waters at the appropriate times of year by targeted field sampling.

The movement patterns of prawn populations over the season and between inshore and offshore areas are highly relevant as they all have a general offshore migration as they increase in size from pre-recruits to recruits and spawners and an inshore migration as larvae. These issues need to be more explicitly investigated with regard to the assumption of the relationship between catch rates and biomass over time.

This project will fill essential gaps in our knowledge and also develop a scientific basis for long-term investments in fieldwork. Although this project will concentrate on the less assessed white banana prawn (Penaeus merguiensis) and the tiger prawns (P. semisulcatus, P. esculentus), the fieldwork, design and research concepts would probably also apply to endeavour prawns (Metapenaeus endeavouri, M. ensis).

Related projects
Die D, Loneragan N, Haywood M, Vance D, Manson F, Taylor B, Bishop J. (2001). Indices for recruitment and effective spawning for tiger prawns stocks in the Northern Prawn Fishery. Final Report toFRDC for Project 1995/014. 82 pages with 8 appendices.