674 



Fishery Bulletin 101(3) 



1991). However, the lack of information about the stock 

 structure of, and connectivity among, adult populations has 

 hindered MPA design (Walters and Bonfil, 1999). Conser- 

 vation management of the Great Barrier Reef (GBR) has 

 included the use of spatial closures of areas to activities, 

 including fishing, for more than 15 years. The majority of 

 spatial closures to line fishing are of individual coral reefs 

 or groups of reefs. This spatial management strategy is 

 underpinned by the assumption of the metapopulation 

 model of coral-reef fish described above. That is, closing 

 individual reefs to fishing will protect the adult popula- 

 tions on those reefs, and potentially provide a source of 

 larvae to areas open to fishing. Management of line fishing 

 on the GBR currently includes bag limits for recreational 

 fishermen and minimum-size restrictions that are uniform 

 for all fishermen and across the entire area of the fishery. 

 Such management regulations are based on the assump- 

 tion that the demography of target species does not vary 

 substantially over the species range and on the assump- 

 tion that that populations on the GBR represent a single, 

 homogeneous stock. 



The red throat emperor (Lethrinus miniatus) (also 

 known as the trumpet emperor) is a relatively long-lived 

 (>20 years) (Loubens, 1980: Brown and Sumpton, 1998) 

 member of the Lethrinidae and has a restricted distribu- 

 tion in the western Pacific and eastern Indian Oceans (Car- 

 penter and Allen, 1989). On the GBR it is the second most 

 important demersal species in a multispecies line fishery, 

 contributing up to 1000 metric tons annually to the com- 

 bined commercial and recreational catch (Mapstone et al.^; 

 Higgs-). As with many tropical lethrinids, information on 

 the biology and ecology of L. miniatus is scarce. The limited 

 data available indicate that L. miniatus is usually associ- 

 ated with coral reefs, but that it is also commonly caught 

 in deeper water, in sand, and rubble areas between reefs 

 (Carpenter and Allen, 1989; Newman and Williams. 1996; 

 Williams and Russ'^). The habitat of juvenile L. miniatus 

 is unknown, but Williams and Russ^ have suggested that 

 juveniles may occupy the deeper rubble areas adjacent to 

 reefs. Like some other coral-reef fish, L. miniatus is thought 

 to form large aggregations associated with spawning 



' Mapstone, B. D., J. P. McKinlay. and C. R. Davies. 1996. A 

 description of commercial reef line fishery logbook data held 

 by the Queensland Fisheries Management Authority. Report 

 to the Queensland Fisheries Management Authority from the 

 Cooperative Research Centre for the Ecologically Sustainable 

 Development of the Creat Barrier Reef, and the Department of 

 Tropical Environmental Studies and Geography. James Cook 

 University, Queensland. Australia, 480 p. lAvailable from 

 the Queensland Fisheries Service, G.P.O. Box 46, Brisbane. 

 Queensland, Australia 4001.1 



- Higgs, J. 2001. Experimental recreational catch estimates 

 for (Queensland residents. Results from tbi' 1999 diary round. 

 KFISH technical report no. .'!. Queensland Fisheries Sei-vice, Aus- 

 tralia, 62 p. lAvailable from the Queensland Fisheries Service, 

 G.RO. Box 46, Bri.sbane, Queensland, Australia 4001.1 



■' Williams, D. McB., and G. R. Russ. 1994. Review of data on 

 fishes of commercial and recreational fishing interest on the 

 Great Barrier Reef Report to the Great Barrier Reef Marine 

 Park Authority, 103 p. [Available from the Great Barrier Reef 

 Marine Park Authority, P.O. Box 1379, Townsville, Queensland, 

 Australia, 4810.1 



(RusselH). These available data suggest that L. miniatus 

 adults have the capacity to move among individual reefs on 

 the GBR. This movement pattern contrasts with informa- 

 tion on movement patterns of other large coral-reef spe- 

 cies such as the coral trout (Plectropomus leopardus) (also 

 known as the leopard coral grouper, Heemstra and Randall, 

 1993) where adults show limited movement within a single 

 reef and very restricted movements between reefs (Davies, 

 1995). It also contrasts with movement patterns of the ma- 

 jority of coral-reef fish, where adults are known to have 

 very restricted home ranges and display little, if any, move- 

 ment between reefs (Lewis 1997; Sale, 1998). Therefore the 

 relevant spatial scale affecting demographic parameters of 

 L. miniatus may be larger than an individual reef and thus 

 is different from that for most "typical" coral-reef fish. 



The central objective of this study was to determine how 

 the spatial patterns in demogi'aphy of large, more mobile 

 reef fish differ from smaller site-attached reef-fish species. 

 To achieve this we used validated age estimates to examine 

 spatial variation in demographic parameters of populations 

 of L. miniatus across two spatial scales most relevant to as- 

 sessing and managing the species on the GBR: 1 ) among 

 individual reefs within regions and, 2) among geographic 

 regions. Specifically, we estimated age structures, growth, 

 mortality, and otolith growth rates for among four reefs (all 

 closed to fishing) within each of three geographic regions 

 spanning over 500 km (over 3° of latitude) of the GBR. 



Materials and methods 



Collection methods 



Samples of L. miniatus were collected from three geo- 

 graphic regions of the GBR as part of a large-scale manip- 

 ulative experiment to examine the effects of line fishing 

 on the GBR (Davies et al.^; Mapstone et al.'^). The three 

 regions cover most of the distribution of L. miniatus on 

 the GBR (Fig. 1), which is restricted to the southern 50% 

 of the GBR. Within each region L. miniatus were collected 

 from six individual reefs. Four of these reefs were zoned 

 "Marine National Park B" and were closed to all forms of 

 fishing (referred to as "closed reefs" in this article) whereas 

 the other two reefs were zoned "General Use B" and were 



'' Russell, M. 2001. Spawningaggregationsof reef fishes on the 

 Great Barrier Reef: implications for management. Report from 

 the Great Barrier Reef Marine Park Authority. 37 p. [Available 

 from the Great Barrier Reef Marine Park Authority, P.O. Box 

 1379. Townsville, Queensland, Australia. 4810|. 



= Davies, C. R., B. D. Mapstone, A. Ayling, D. C. Lou, A. Punt, G. R. 

 Russ, M. A. Samoilys, A. D. M. Smith. D. J. Welch, and D. McB. 

 Williams. 1998. Effects of line fishing experiment 1995-1997: 

 project structure and operations. -Supplementary to progress 

 report. CRC Reef Research Centre, Townsville, Australia, 28 p. 

 lAvailable tioni the CRC Reef Research Centre. PO. Box 772, 

 Townsville, Queensland, Australia 4810). 



6 Mapstone, B. D.. C. R. Davies. I). C. Lou, A. E. Punt, G. R. Russ, D. 

 A. .1. Ryan. A. D. M. Smith, and D. McB. Williams. 1998. Effects 

 ofline fishing experiment 199.5-1997: progress report. CRC Reef 

 Research Centre, 86 p [Available from the CRC Reef Research 

 Centre, P.O. Box 772, Townsville, Queensland, Austraha 4810). 



