Photo: John E. Randall
Description and Distribution
Camouflage grouper, Epinephelus polyphekadion, is widely distributed in the Indo-Pacific. It preys on portunid crabs, other crustaceans, fishes, and molluscs. The species ranges from the eastern coast of Africa through the Red Sea to the islands of the eastern Pacific, south to Lord Howe Island and north to the Ryuku Islands of Japan (7,13).
Adult camouflage groupers are commonly associated with coral reefs in clear water and are solitary during non-reproductive periods. Details on habitat use are unknown, but fisheries-dependent data suggest that the adults prefer inshore reef areas (7,9,16).
The above diagram shows the range of camouflage grouper (highlighted in green)
and reported spawning aggregation sites (highlighted in red)
Several studies have investigated the early life history of camouflage grouper under hatchery conditions. Fertilised eggs ranged from 0.73-0.85 mm in diameter and were transparent, positively buoyant. Hatching occurred within 18-19 hours at 28-30°C in Saudi Arabia and 20-21 hour at 27°C in Palau. Newly hatched larvae ranged from 1.55 to 1.71 mm (TL). Larvae have elongated fin spines and head spines. Larval transformation occurred at 40 days, and after 15 months juveniles reportedly grew to 800 g. The habitats, fate and behaviour of pre-settlement individuals in the wild are unknown, although recent evidence shows post-settlement camouflage grouper as generalists with no specific nursery habitat defined (1, 2, 8, 25).
In Palau, post-settlement camouflage grouper were observed in low branching corals with associated macroalgae, bushy macroalgae, massive coral heads and coral rubble. Post-settlement individuals appeared to become more cryptic as they grew and seemed to prefer more turbid waters in deeper rubble areas and coral heads. In Pohnpei (Micronesia), post-settlement individuals were taken by hook and line from rubble patches in turbid waters near mangroves. No information is available on ontogenetic habitat shifts in the species, but individuals are presumed to move from shallower inshore areas into deeper water habitats with increasing size (1, 2, 8, 25).
Sexual Pattern & Spawning Aggregations
Sexual pattern in the camouflage grouper has been described as protogynous, based on combined tag and recapture, histochemical and histological techniques. However, no conclusive histological evidence is yet available to confirm protogyny for the species. In studies to date, adult males are (significantly) larger than adult females and juveniles, although there is often substantial size overlap between sexes, suggesting that should sex change occur, it is likely to do so over a relatively wide size range. The strongest evidence for sex change is provided from tag and recapture data from Palau, where at least two individuals tagged as females were later recaptured as males. Three other individuals tagged during the same study were recaptured with both male and female tissues. Based on samples from a study of marketed and reproductively active camouflage grouper in Pohnpei, both males and females can develop directly from juveniles. If protogyny is later confirmed for the species, the male development pathway would then be considered diandric, whereby males develop from juveniles as well as from adult females through sex change (2,4,5,11,13).
Camouflage groupers aggregate to spawn and their spawning aggregations (FSA) have been reported from many areas within its distributional range, including Fiji, Indonesia, Malaysia, Micronesia, Palau and the Seychelles. In some locations such as the Seychelles, almost 2,000 individuals have been reported within a single FSA, while other areas may consist of less than 100 individuals. Based on casual observations, estimates of up to 20,000 individuals have been reported from a single spawning aggregation in Pohnpei, although more recent estimates found only a few hundred individuals following intense fishing at some sites. Estimates from three separate camouflage grouper FSAs in Palau ranged from a few hundred to more than 2,000 individuals (6,10,14,15).
The timing of aggregation formation and spawning varies across the region, with aggregations forming approximately two weeks prior to either new moon or full moon, depending on location. For example, aggregation formation and spawning occurs prior to new moon in Palau and the Seychelles, while pre-full moon aggregation formation and spawning occur in Pohnpei. In most places, aggregations typically form over a period of 2 to 3 months, with peaks in abundance during one month of the seasonal spawning period. FSA vary in depth across their range (ca. 5-40 m), although they are typically found on seaward-facing portions of reefs or channels (10,15).
While no studies have been undertaken to examine large-scale patterns of movement in adult camouflage grouper, small sub-groups of adult individuals have been observed moving along the reef toward the aggregation site during reproductive periods, suggesting the use of common reproductive migratory pathways for spawning. Recently, FSA site fidelity relative to spawning sites has been revealed from conventional tagging studies in the Seychelles and in Palau. In the Seychelles study, several tagged individuals returned over two consecutive reproductive months and at least one individual showed inter-annual site fidelity, returning to the FSA site 352 d after tagging. In Palau, Johannes et al. (1999) were able to demonstrate that (1) individuals may return to spawning sites over multiple (2-3) months within the spawning season, (2) at least some individuals return to the same site inter-annually, (3) individuals may travel as much as 5-10 km from spawning sites between reproductive and non-reproductive periods and, (4) individuals appear not to utilize more than one spawning site during reproduction, even though a number of aggregations may form in relatively close proximity (9,10).
E. polyphekadion is a highly prized fish throughout much of its distributional range and often contributes substantially to local catch. The species can be taken with a wide variety of gears, but is most often targeted by spear or hook and line, and often at spawning aggregation sites or along reproductive migratory pathways. Camouflage grouper are sought after by local subsistence and commercial fishers, as well as by foreign commercial fishing entities that include the Southeast Asia-based live reef food fish trade. Spawning aggregations are targeted within its range - in some areas such as the Cook Islands and Tuvalu, fishers exploit the fish at aggregations only for local consumption. In some areas, camouflage grouper are ciguatoxic (9,11,12,17,20,23).
Camouflage grouper together with Plectropomus areolatus and E. fuscoguttatus dominate the commercial catches of groupers in Palau. In Pohnpei, it contributes 20.7% to serranid catch and appeared in 11.1-30.2% of catches among all gear types (10,15,16).
Camouflage grouper is one of the most commonly consumed live reef food fishes in Hong Kong, where they are shipped from major countries such as the Philippines and Indonesia. A survey of the import companies concerned in the live fish trade in Hong Kong revealed that E. polyphekadion made up 5% (approx. 1,200 tonnes) of the total annual volume of live reef fish trade(12).
Camouflage grouper can be cultured in Asia and the Middle East. However, mariculture farmers think that this species has poor growth rates and preferred to culture E. fuscoguttatus which grows faster and brings similar market price. Cross breeding of the two species has occurred in Saudi Arabia with good grow-out potential for aquaculture (8, Rimmer M. pers comm).
E. polyphekadion is considered as near threatened in the IUCN Red List (assessed in 2006). Threats that the species is facing include commercial and recreational fishing and habitat degradation of coral reefs (20).
Although the species is widely distributed, it is susceptible to overfishing, especially at its spawning aggregations and to spearfishing, as it is easy to approach underwater, especially at night. Declines from aggregation-fishing have been reported in fisher interviews from a range of countries. Habitat degradation of coral reefs also has the potential to affect its numbers and a high proportion of coral reefs have been degraded in a significant part of its range in SE Asia. On the other hand, it remains one of the more common species of live fish imported into the Hong Kong restaurant market (12,20).
In Fiji, the species is intensively fished - its catch-per-unit-effort decreased significantly from four sites getting about 300 kg in the 1990s to 100 kg in 2002-3 per trip. The number of fish also dropped by about 50% from 1992 to 2002 in New Caledonia. In Tonga, reported abundance experienced a ten times decrease in 1996 to 2002-3. The species can no longer be seen in French Polynesia, where it was once a major component of commercial catch in the 1980s. Of the 34 spawning aggregations known for this species in the region, the status of 14 is unknown, 16 are in decline, 1 has gone and 3 are increasing in response to protection (20).
Conservation & Management
A number of management measures are in place to conserve camouflage groupers: 1) sales ban during spawning season implemented in Micronesia, Palau, and Solomon Islands; 2) spawning aggregation fishing ban is implemented in Micronesia, New Caledonia, Palau, and Solomon Islands; 3) Marine Protected Areas (MPA) in Micronesia and Palau, and 4) minimum size limits in Australia (10,14,18,23).
Despite the above mentioned measures, the effectiveness of camouflage grouper management is in doubt. Aggregations may not be fully protected and the effectiveness of MPAs is also in question. Some MPAs permit fishing and some are not large enough to incorporate spawning sites and reproductive migratory pathways for targeted species (17,20).
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