678 



Fishery Bulletin 101(3) 



A Townsvllle 



n = 347 



B Mackay 



10 12 14 16 18 20 



n = 370 



0) 40 



2 4 6 8 10 12 14 16 18 20 



C Storm Cay 



n = 298 



2 4 b b 10 12 14 16 18 20 



Age (years) 



Figure 4 



Age structures for L. miniatus from 

 three regions of the Great Barrier 

 Reef: (A) Townsvllle, (B) Mackay, and 

 (C) Storm Cay. Age structures were 

 pooled from four closed reefs within 

 each region. 



Somatic growth 



Estimates of VBGF parameters varied considerably among 

 reefs within the Townsvllle and Mackay regions but in the 

 Storm Cay region, estimates of L^ and particularly K' were 

 very similar (Table 1). Examination of BS^f confidence 

 regions for VBCJF parameters for individual reefs (Fig. 6) 

 indicated considerable uncertainty in the estimates of both 

 K and L.^ and no clear differentiation among reefs within 

 regions. The similarity in VBGF parameters for individual 

 reefs within the Storm Cay region was particularly evident 

 from the 95% confidence regions. In both the Townsvllle 

 and Mackay regions, three reefs showed overlap in 95% 



J= 2 



TownsvNIe 



Mackay 



2 4 6 8 10 12 14 16 18 

 Age (years) 



Figure 5 



Age-based catch curves fori, miniatus from 

 three regions of the Great Barrier Reef • = 

 Townsvllle; ■, Mackay; ▲ = Storm Cay. 

 Catch curves were derived from pooled age 

 structures from four closed reefs within each 

 region. Open data points were not used in 

 the regressions. 



confidence regions, whereas only a single reef in each 

 region appeared to have significantly different VBGF 

 parameters from the others (Fig. 6). 



Given the lack of differentiation in growth among reefs, 

 the data from individual reefs were pooled for each region 

 to examine regional patterns in growth. VBGF parameters 

 varied significantly among regions (Table 1) with no over- 

 lap in the 95% confidence regions (Fig. 7). It appeared that 

 L. miniatus in the Mackay region attained a larger average 

 asymptotic size (L^=472.21 mm FL) than in the Storm Cay 

 region (L^=462.83 mm FL), where in turn these fish grew 

 larger than fish in the Townsvllle region (L^=453.36 mm 

 FL). It should be noted that the constrained fitting of the 

 VBGF itg set to zero) provided a conservative estimate of 

 regional variation in growth, and regional differences were 

 considerably larger when the VBGF parameter <q was not 

 constrained to zero. 



Discussion 



The scale of spatial variation in demography of a large, 

 potentially more mobile reef fish was found to be larger 

 than that reported for smaller site-attached reef-fish spe- 

 cies on the GBR. Estimates of otolith and somatic growth, 

 age structure, and mortality of//, miniatus all varied more 

 among regions than among reefs within regions. Further- 

 more, with the exception of mortality estimates, which 

 differed only between the Townsvllle and Mackay regions, 

 all estimated parameters were significantly different 

 among all three regions. Despite their relative proximity, 

 the Townsvllle and Mackay regions consistently showed 

 the greatest difference for each demographic param- 

 eter. This indicates that the observed differences did not 

 relate simply to a linear latitudinal gradient among the 

 regions. 



