Summary

The eastern rock (spiny) lobster, Jasus verreauxi, is the target species of the $ 5 million per annum commercial rock lobster fishery in NSW.  It is considered a boutique seafood bringing high prices of on average around $45 per kg.  This species exhibits five major phases during its life cycle: adult, egg, larval, post-larval and juvenile.  Adults occur in waters between 10 m and 200 m and mainly in waters in the north of the state.  They aggregate during the day in crevices and dens and at night emerge to forage.  Egg masses are spawned and hatched over spring and summer.  It is thought that early larval stages are transported offshore by wind-driven surface currents.  After some time in the plankton, the last larval stage metamorphoses into a post-larva – a transparent, free-swimming stage – that actively swims and (most likely) uses ocean currents to reach vegetated reef area along the coastline.  Here, the animals grow as juveniles for around 4 years before moving into deeper and more northern waters to join the adult stock.

This paper deals with the distribution and abundance of eastern rock lobsters during the post-larval (puerulus) to early juvenile stages of the species’ life cycle, collectively referred to in the paper as “eastern rock lobster recruits”.  It tests the hypothesis that the distribution and abundance of eastern rock lobster recruits changes in space and time.  Such information about the distribution and abundance of recruits enhances our understanding about (i) the survival of individuals during the early stages of their life-cycle, (ii) when recruitment to the population occurs, (iii) the preferred habitat of recruits, (iv) stock-recruit processes and (v) the effects of managerial decisions on recruitment.  Devices known as collectors were developed and used at 4 locations (Coffs Harbour, Tuncurry, Port Hacking and Ulladulla) over eight years to collect data to test the hypothesis.  Results showed that eastern rock lobster recruit to coastal reefs only during spring and summer each year and that greater numbers are found in southern than northern waters.  It is concluded that the duration of the eastern rock lobster larval phase is around 8 to 12 months and that southern coastal reefs are important nursery grounds for the eastern rock lobster population.  The new management measures of entry criteria to the fishery, individual catch quotas and a legal maximum size were introduced in the mid 1990s to increase population size, but these seem to have not resulted in increasing levels of recruitment to date.  This may be because the size of the spawning stock in the mid 1990s was not as low as first thought or that the spawner/recruit relationship for J. verreauxi is such that small changes in spawning stock do not produce large changes in numbers of recruits.  Considering this, levels of recruitment to the population appear to be influenced mostly by variation in environmental factors (such as the strength and direction of the East Australian Current and currents generated by prevailing winds), rather than levels of egg production from the stock.