25 



Abstract.— Rock lobster, Jasus ver- 

 reauxi, have been fished off New South 

 Wales, Australia, since the late nine- 

 teenth century. Since 1994—95 (1 July 

 1994 to 30 June 1995) the fishery has 

 been managed under an output-control 

 scheme with an annual total allowable 

 catch (TAC) of 106 metric tons (tl. Es- 

 timates of catch and catch per unit of 

 effort (CPUEi have been developed 

 from data collected from the commer- 

 cial fishery for the period 1903-1936 

 and the period from 1969-70 to 1993- 

 94. A production model was fitted to 

 these data by using a robust observa- 

 tion-error estimator that minimizes the 

 median of squared differences between 

 log-observed and predicted CPUEs. A 

 bootstrap resampling procedure was 

 incorporated into this robust estimation 

 method to estimate stock parameters 

 and their uncertainties. The virgin bio- 

 mass of the rock lobster was 4084 t (its 

 5* and 95"^ percentiles being 2553 and 

 6400 t). The stock biomass decreased 

 substantially until 1990-91. Since 

 1992-93, it has stabilized and has prob- 

 ably increased owing to the large de- 

 crease in the allowable catch after 

 1988-89. The stock biomass in year 

 1995-96 was likely to have been be- 

 tween 15% and 30% of the virgin biom- 

 ass (75% confidence interval). The im- 

 plications from using different estima- 

 tion methods on assessing this lobster 

 stock are discussed. 



Modeling the dynamics of eastern tx>ck lobster, 

 Jasus verreauxi, stock in New South Wales, 

 Australia 



Yong Chen 



Steve S. Montgomery 



Fisheries Research Institute 



NSW Fisheries 



PO Box 21, Cronulia 



New South Wales 2230, Australia 



Present address (lor Y Chen): Fisheries and Marine Institute 



Memonal University of Newfoundland 



St. John's, Newfoundland, Canada A1C 5R3 



E-mail address (for Y Chen) ychen a caribou ifmt nf ca 



Manuscript accepted 30 April 1998. 

 Fish. Bull. 97:25-38(1999). 



The eastern rock lobster, Jasus ver- 

 reauxi, reportedly is the largest 

 spiny rock lobster in the world 

 (Philips et al., 1980). It occurs in 

 waters off the coast of New South 

 Wales (NSW), Australia, around the 

 coast of Tasmania, and as far west 

 as South Australia (Montgomery, 

 1995). It is also found off New 

 Zealand, predominantly around the 

 North Island (Kensler, 1967a). 



Limited information on the life 

 history of J. verreauxi in waters off 

 NSW is available (McWilham and 

 Philips, 1987; Montgomery, 1992, 

 1995; Montgomery and Kittaka, 

 1994; Montgomery^ ). Most informa- 

 tion comes from studies of the spe- 

 cies in waters off New Zealand 

 (Kensler 1967a, 1967b, 1967c; 

 Booth, 1984a, 1984b, 1986). How- 

 ever, comparisons of mitochondrial 

 DNA from juvenile rock lobsters 

 from NSW and New Zealand waters 

 have suggested that the populations 

 are genetically distinct (Brasher et 

 al., 1992). 



The distribution of rock lobsters 

 across habitat is patchy. From the 

 puerulus to early juvenile stages of 

 their life cycle, lobsters are probably 

 asocial and thought to occur princi- 

 pally within the complex structure 

 of forests of macroalgae or within 

 beds of seagrass in waters from the 

 intertidal zone to 30 m. During the 

 older stages of the juvenile phase, 



the animal may begin to aggregate 

 and migrate en masse to the habi- 

 tat of adults. Adult rock lobsters live 

 in aggregations from depths of 

 around 10 m to those of the conti- 

 nental slope (Montgomery, 1995; 

 Montgomery^). From the older ju- 

 venile stage onward, lobsters aggre- 

 gate by day, and at night they roam 

 alone. Information on the move- 

 ments of tagged rock lobsters off 

 New Zealand (Booth, 1984b) and 

 spatial patterns in the length com- 

 position of rock lobsters in waters 

 off NSW (Montgomery^) suggest 

 that for management purposes the 

 entire NSW population of rock lob- 

 sters should be considered as a unit 

 stock. These studies indicate that 

 older juveniles and adults move in 

 an inshore-offshore direction and 

 along the coast. The movement 

 along the coast is thought to be as- 

 sociated with breeding (Booth, 

 1984b). 



Rock lobsters have been fished off 

 the east coast of Australia since the 

 late nineteenth century. It is an 

 important fishery in NSW, with an 

 annual output of over 5 million US 

 dollars. Since the 1994-95 fishing 



' Montgomery, S. S. 1990. Preliminary 

 study of the fishery for rock lobsters off the 

 coast of New South Wales. Final Report, 

 grant no. 86/64. Fisheries Research and 

 Development Corporation, Canberra, Aus- 

 tralia, 166 p. 



