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Fishery Bulletin 104(4) 



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130«00 E 140=00 E 



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South Direction 

 ' Rocky Islets A ~^ 

 Rocky Islets B 



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Figure 1 



Great Barrier Reef, Australia. Study regions and reefs (1- 

 trout tPlectropomus leopardus) were collected are shown. 1 = 

 3 = Mackay; 4 = Storm Cay. 



•4) from which common coral 

 Lizard Island; 2 = Townsville; 



ment, four reefs in each region had been closed to fish- 

 ing for 10-12 years under GBR Marine Park Zoning 

 Plans (zoned Marine National Park B, MNP-B) and two 

 reefs in each region had been open to fishing (zoned as 

 General Use, GU). Two of the reefs closed to fishing 

 remained closed during the experiment, other than to 

 the annual research line fishing surveys. The other two 

 closed reefs were each subjected to one year of fishing, in 

 1997 and 1999, after which they were closed again. The 

 two reefs in each region that had historically been open 

 to fishing were subjected to increased fishing pressure 

 for one year (i.e., were temporarily opened). These reefs 

 were then closed for five years before reverting to their 

 original zoning status (GU). 



All reefs were sampled each year in the austral spring 

 (October-December) to coincide with the peak spawn- 

 ing period of the main target species, P. leopardus. 

 Each reef was divided into six approximately equal- 

 size, contiguous blocks, and sampled on a single day 

 on each sampling occasion. Standardized commercial 

 reef line fishing effort was distributed uniformly across 

 two depth strata within each block. All fish caught were 



measured, tagged for later identification, and kept for 

 weighing and for extraction of gonads and otoliths. For 

 further sampling details of the ELF experiment see 

 Davies et al.^ and Mapstone et al. (2004). Samples of P. 

 leopardus were aged by CRC Reef staff using standard- 

 ized methods developed by Ferreira and Russ (1994). 



Sample collection 



Otolith morphological variables were analyzed from 

 four-year-old P. leopardus collected in 1995 and 1999 

 from three reefs within each of the four regions (Fig. 1; 

 Table 1). Four years is the youngest age at which P. 

 leopardus in all regions are fully recruited to the fishing 

 gear used in the ELF Experiment. Although the zoning 

 status of a reef and the level of fishing pressure on it 

 were unlikely to have affected otolith structure, one reef 

 from each treatment regime in the ELF experiment was 

 included from each region to avoid potential biases in 

 spatial variation related to particular fishing histories. 

 Thus, within each region, samples were analyzed from 

 one MNP-B reef that was closed to fishing, one MNP- 



