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Fishery Bulletin 99(1) 
piscivorous. Thus, unlike other less piscivorous coral reef 
serranids (Hobson, 1965; Randall, 1965; Harmelin-Vivien 
and Bouchon, 1976; Shpigel and Fishelson, 1989), adult P 
leopard us rely almost entirely on one general type of food 
(but juveniles consume crustaceans, St John, 1999). Also, 
nearly half of their diet (IRI=48.4%) comprised just two 
families of fishes, Pomacentridae and Labridae, but this 
finding does not suggest that the food supply of P. leop- 
ardus was limited. Plectropomus leopardus have been re- 
ported to consume more than 20 species in each of these 
two families (St John, 1995), which are highly diverse and 
abundant on coral reefs. On the GBR, Pomacentridae, with 
some 120 species, is the most numerically abundant fam- 
ily, and Labridae represents the second most speciose fam- 
ily (Randall et al., 1990). Therefore, the diet of P. leopardus 
was not dependent on a few species. 
The variety of prey fishes in the diet of P. leopardus 
reflects the groupers large home range (Samoilys, 1997; 
Zeller, 1997) that includes several habitats (Goeden, 1978; 
Kingsford, 1992; Samoilys, 1997). Plectropomus leopardus 
consumed fishes in families that lived in all four broad 
habitats on coral reefs; adjacent sands, midwater, benthic 
reef substrata, and demersal reef substrata. Yet, prey from 
the demersal reef environment and the midwaters were 
six times more important than prey in the other two habi- 
tats. The diverse and abundant families of fishes that live 
on or over adjacent sands, or dwell among the benthic reef 
substrata (e.g. Gobiidae and Blenniidae) were not impor- 
tant food for adult P. leopardus. Similarly, piscivores re- 
ported from coral reefs elsewhere have usually focused on 
prey in reef habitats. In the Caribbean, tethered prey con- 
sistently disappeared from sites close to areas of natural 
reef rather than from areas of adjacent sediment (Shul- 
man, 1985), and rates of encounter with predators for sur- 
geonfishes in bottles were highest at reef edges compared 
with other sediment habitats (Sweatman and Robertson, 
1994). 
Lastly, the results of our study suggest several differenc- 
es in the catch and diet of P. leopardus caught by the two 
fishing methods. Such information is useful for managers 
when considering the impacts of different types of fishing 
methods on the fish population. Line fishing catches larg- 
er fish than nonselective spear fishing; however nonse- 
lective spear fishing probably never occurs in the real 
fishery. Based on the comparison of line catch and spear 
catch, baited lines appear to attract a higher proportion 
of hungry P. leopardus to common fishing sites, but preda- 
tors may leave the site after they have eaten bait. There- 
fore, line fishing can affect the trophic ecology of P. leop- 
ardus reef-wide, even when it is concentrated at just a 
few sites on reefs. Also, line fishing may alter patterns 
of movement of P. leopardus temporarily, and such op- 
portunistic behavior will be difficult to detect in move- 
ment studies on this species (e.g. Samoilys, 1997; Zeller, 
1997). Thus, when reefs are partitioned into different fish- 
ing zones, line fishing could facilitate the movement of 
P. leopardus across reserve boundaries from protected ar- 
eas. In one study on the GBR, P. leopardus had low flux 
rates across reserve boundaries (Zeller and Russ, 1998). 
Another, more tentative, result of our study is that line- 
caught fish appear to eat more midwater pelagic fishes, 
which suggests that line fishermen or the methods used in 
line fishing target P. leopardus hunting this prey. Whether 
line fishermen chose sites where pelagic schooling fishes 
congregate (e.g. near the reef edge) or whether pelagic 
prey are attracted to a fishing site after fishermen hurley 
the waters, is uncertain. 
In conclusion, eight years after reefs have been closed to 
fishing, no differences that could be linked to zoning were 
detected in size structure of populations and diets of P. 
leopardus. Results of this dietary study, however, can offer 
some insights for the management of the P. leopardus fish- 
ery. Even though fish are the dominant food of this preda- 
tor, and the main fish prey are associated with the coral 
reef substrata, P. leopardus are not dependent on a narrow 
range of species for food. A diverse mixture of Pomacentri- 
dae and Labridae species represents nearly half of their di- 
et, and overall, the diet of P. leopardus is sufficiently broad 
to be resilient to the depletion of several species of prey. 
Acknowledgments 
We acknowledge and thank two anonymous referees for 
pertinent comments about the manuscript, Tony Ayling 
for providing his visual census data, the Squire family 
for accommodating J. St John, and the staff of the North- 
ern Fisheries Center for the use of their facilities. This 
research was supported by the Great Barrier Reef Marine 
Park Authority, a Freda Bage Fellowship (Australian Fed- 
eration of University Women, Queensland) to J. St John, 
and Australian Research Council funds to G. R. Russ. 
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