The puerulus settlement in 2007/08 was the second lowest in 40 years and follows several years of below-average settlements. Previous studies have shown that environment factors such as the Leeuwin Current and storms affect the abundance and spatial distribution of puerulus settlement. However it is important to identify if there are some changes to these environmental factors contributing to the low recruitment. Initial monitoring indicates very low 2008/09 settlement despite the Leeuwin Current being above average this year. This event is unexpected based on previous settlements during years of strong Leeuwin Current and has serious implications for the management of the fishery. The breeding stock overall is believed to be within historic ranges and so is not expected to have contributed to the recent decline in settlement. However it is possible that the breeding stock in certain parts of the fishery may be more critical than others and this could have changed over the years due to climate change effects.
Advances in quality of satellite data in the 1990s measuring sea surface topography (altimeter satellites) have enabled significant improvements in our understanding of the environmental factors, with the assistance of oceanographic modelling. Previous oceanographic models were focussed on the open ocean circulation off the continental shelf. Recent advances enable the development of high-resolution models at 10 km spatial scale which resolve the dominant processes on the shelf. Understanding the causes of recruitment variability and their long-term trends has important implications in the stock assessment and management of the fishery. The management response would be significantly different if the cause of the series of low recruitment was due to egg production or environmental factors. An adjustment to the sustainable harvest rate may be required if there are long-term environmental trends that affect the average recruitment of the western rock lobster.