602 



Fishery Bulletin 89(4). 1991 



Catchability in the NSW fish- 

 ery is very high and suggests 

 a fishing mortality rate of ap- 

 proximately 0.8/year, reflect- 

 ing the high recapture rate 

 there (33% of experiment 2 

 releases recaptured within 1 

 year and 42% recaptured with- 

 in 2 years). Catchability is sub- 

 stantially lower in the SA and 

 Japanese fisheries, suggesting 

 rates of fishing mortality of 

 approximately 0.35/year and 

 0.03/year, respectively. The 

 catchability coefficients in- 

 crease steadily with decreas- 

 ing reporting rates, approx- 

 imately doubling with a reduction in assumed report- 

 ing rate from 1.0 to 0.5. Rates of movement are slightly 

 higher in the SA-*NSW direction (0.17/year) than in 

 the NSW-*SA direction (0.12/year). Apparent move- 

 ment into the Japanese fishery is substantially higher 

 from the SA fishery (0.57/year) than from the NSW 

 fishery (0.10/ year). The movement parameters are 

 relatively unaffected by changing the assumed report- 

 ing rate within the range 1.0-0.5. 



The standard errors of the parameters are large, par- 

 ticularly for M 1? M 2 , T 13 , and T 23 . The correlation 

 matrix for the parameters (Table 7) indicates several 

 cases of extreme confounding of estimates. The Ms are 

 very highly correlated with one another and individual- 

 ly with q 3 , T 13 , and T 23 . The latter three parameters 

 are also very highly correlated with one another. These 

 high correlations and standard errors suggest that the 

 model is overdetermined (too many parameters). 



