Description and Distribution
Epinephelus fuscoguttatus (brown marbled grouper) is a large-bodied grouper in the family Serranidae, reaching approximately 1 m in total length (TL). The species is widespread throughout the Indo-Pacific, including the Red Sea, and is often confused with the similar-looking, co-occurring but smaller, E. polyphekadion (camouflage grouper) (6).
E. fuscoguttatus is reef-associated, occurs in lagoon pinnacles, channels, and outer reef slopes, in coral-rich areas with clear waters at depths ranging from 1 to 60 m. Juveniles occur in seagrass beds (3,6,12).
The above diagram shows the range of brown marbled grouper (highlighted in green)
and reported spawning aggregation sites (highlighted in red)
Brown marbled grouper is naturally uncommon, and is relatively long-lived (lifespan can exceed 40 years) and attains about 100 cm (TL). Estimates of size and age at effective maturity, where 50 percent of females are sexually active during the spawning season, are 57 cm (TL) and 9-10 years of age (11,12).
The sexual pattern appears to be monandric protogyny in which juveniles mature and then function first as adult females before changing sex, although confirmation of sex change is still required. The postulated life history strategy is one in which energy is primarily invested in body growth for 9-10 years; afterwards growth slows and energy is invested in reproduction. Large females make important reproductive contributions during their 30+ year reproductive lifespan. Estimates of 50% effective maturity calculated from the percentage of females that were sexually active during the spawning season were approximately 56 cm (TL) and 9 years. The high fecundity female breeders do not occur until almost 60 cm TL. There are females up to at least 85 cm (TL) with the smallest mature female recorded as 42 cm (TL). No males smaller than about 70 cm (TL) are known (8,11,12).
Brown marbled grouper is only known to spawn in aggregations. Large, old females may also have additional roles in the social system. Younger and inexperienced individuals may learn the way to traditional spawning sites by migrating with experienced fish. It will be important to maintain the natural size and age structures, and enough individuals of both sexes to ensure spawning aggregations continue to function (2,19,21,25).
While reported spawning duration each year for E. fuscoguttatus is relatively short for a coral reef fish (e.g. three months), timing of spawning each year and its and lunar periodicity variy widely across the Indo-Pacific. It has been reported to aggregate in relatively large numbers to spawn, with over 350 individuals being counted at spawning aggregation sites in Palau, and a total aggregation abundance of between two and five thousand individuals being estimated in the Seychelles. Spawning aggregations are known from Australia, British Indian Ocean Territory, Federated States of Micronesia, Fiji, Indonesia, Malaysia, New Caledonia, Palau, Seychelles and Solomon Islands. Aggregation sites of E. fuscoguttatus are often found close to those of E. polyphekadion and other sympatric groupers especially as Plectropomus areolatus (squaretail coral grouper), P. laevis (blacksaddled coralgrouper) or P. punctatus (marbled coral grouper) (3,8,11,12,14,15,16).
Several studies provide important insights into reproductive activity of brown marbled coral grouper. On the Great Barrier Reef, Australia, one detailed study identified the spawning period for E. fuscoguttatus to be November to January. The prolonged period of male inactivity each year corroborates the finding of a relatively narrow spawning period for the species in other areas. In the Seychelles, transient (short term and away from the species home range) aggregations related to spawning activity may form for over just 2 weeks for each of 2 to 3 months per year (November to January). Female E. fuscoguttatus may spawn more than once during an particular aggregation period. Three or four significant spawning aggregations formed annually in Palau, with the peak between 1 and 7 days before the new moon and duration of around 5 days (May to September). Results also indicated that spawning may occur at other times of the month based on the finding of near-ripe females. Recent work on E. fuscoguttatus in Komodo National Park, Indonesia, reported that aggregations were most distinct during full moon periods between September and February. In Pohnpei, 1,085 individuals were recorded during monitoring over three days of March 2001 around the full moon period (8,11,12,14,15,16,17).
Photo: Randy Thaman
E. fuscoguttatus is heavily sought for the live reef food fish trade. It can be cultured by hatcheries but is still extensively taken from the wild, including from spawning aggregations. It is ciguatoxic in some areas which probably means reduced pressure, as in New Caledonia. The species is caught by hook and line, traps, spears, gillnets, traps, trawls, hook and line, speargun (3,6).
Brown marbled grouper is one of the most important species in Palau fishery. At least five grouper spawning aggregations have disappeared since the 1970s in Palau, maybe due to overfishing: one mostly of E. polyphekadion and E. fuscoguttatus lost in the 1990s, and one mostly of Plectropomus areolatus and E. fuscoguttatus was virtually eliminated in the late 1980s by a live grouper export fishing enterprise In Maldives, the species is heavily targeted and overfished. Declines due to fishing have also been indicated from interviews of fishers in Fiji (Y. Sadovy, pers. comm.) (8,24).
Imports of E. fuscoguttatus into Hong Kong are around 150 t, and major source countries for this species were Indonesia, Maldives, and the Philippines. A survey of the imports of live fish in Hong Kong revealed that E. fuscoguttatus made up 7% (approx 1,700 t) of the total annual import volume (by weight) of fish imported in 1997. The fish comes from both wild-caught individuals as well as those produced by hatcheries. Common size ranges for consumption in the Hong Kong seafood trade are 33 - 48 and 70 - 118 cm (TL). Juveniles are commonly sold in Hong Kong reef fish food market because of the smaller preferred size range for restaurants and markets (9,10,20).
E. fuscoguttatus can be produced in hatcheries (i.e. full cycle culture) in many countries in Asia, including Indonesia, India, Malaysia, Philippines, Taiwan, Thailand, also Australia and the Middle East. Hatcheries in northern Bali (Indonesia) were estimated to produce 6,000,000 fingerlings per year in 2006 and 2007. In the Philippines and elsewhere, juveniles were sometimes caught inshore and then grown-out in floating cages to attain market size (3,7).
Much of the brown marbled grouper being provided to the live fish markets in Hong Kong and mainland China now appears to be from mariculture (Mike Rimmer, pers. comm. 2009).
E. fuscoguttatus is listed as ‘Near Threatened' on the IUCN Red List (assessed 2004). The species is inherently vulnerable to fishing due to its late maturation, aggregation-spawning (when aggregations are targeted) characteristics and high economic value in the live reef food fish trade. Spawning aggregations are sometimes targeted resulting in large catch volume consisting of large individuals. Such fishing practices have been implicated in the decline or disappearance of spawning aggregations of this and other related species (3,12,22).
The degree of protection afforded E. fuscoguttatus spawning aggregations varies widely, and typically is inadequate for preventing declines. For example, out of 34 records for E. fuscoguttatus in the global spawning aggregation database, 11 spawning aggregations (32%) are decreasing. Within multi-species reef fisheries, late maturing, aggregation-spawning groupers will be more vulnerable species to overfishing during both aggregation and non-aggregation periods (www.scrfa.org).
Conservation & Management
E. fuscoguttatus is relatively uncommon and its spawning aggregation sites appear to be scarce, making protection of these sites from overfishing a high priority. A better understanding of the area from which a particular aggregation site draws individuals would help in determining the scales of potential fishing effects and for designing locally appropriate management strategies. Similarly, it is important to determine biological characteristics, such as maturity and spawning periods, locally, to ensure management arrangements are appropriate to local conditions (1,4,16).
Beginning in the 1980s, the Pohnpei State Government began implementing measures to reduce fishing effort on groupers, including a partial sales ban during the spawning season. In 1995, the Kehpara Marine Sanctuary was established, but the northwest boundary fell short of covering brown marbled grouper aggregations, so fishing continued. No foreign fishing vessels are allowed and entry restrictions for divers at one site. However, one shortcoming of the current regulation is that aggregation extend at least one month beyond the protected period (5,15).
Similarly in Palau, the Marine Protection Act of 1994 prohibits sale or purchase of E. fuscoguttatus from April 1 through July 31 each year, intended to protect spawning aggregations. Local traditional ‘buls' reinforce this protection. In 1995 the Act was amended to prohibit any capture of these groupers even for subsistence purposes duringthe closed period. A four-month taboo (bul) was enforced in certain states, but was not completely effective in preventing fishing on the spawning aggregation, which was said by fishermen to be much smaller than they had been ten years ago; poaching is common. Exports are monitored, no foreign fishing vessels are allowed Aggregations extend at least one month beyond protection (8).
In Papua New Guinea, dynamiting and night-time spearfishing at a known spawning aggregation site is prohibited under customary law. In Komodo Marine Park, Indonesia, spawning aggregation protected zones with seasonal closure recommended for traditional use zones (13,14).
In Australia, a minimum capture size limit of 35 cm (TL) and a bag limit on this species apply across all sectors of the coral reef fin fish fishery including for commercial and recreational fishers and charter boat operators. Minimum size limits are set at a point which allows at least half of the fish in a population to reach reproductive maturity and spawn before they are available for harvest. In Great Barrier Reef (GBR), the seasonal closures for the three 9-day periods around the new moons in October to December offer limited protection to E. fuscoguttatus because aggregating behaviour is predicted to occur throughout much of the lunar cycle between November and January. Consideration should be given to a blanket catch ban for E. fuscoguttatus during reproductive months since mature-sized fish captured at any time within the spawning period are potentially reproductively active. Some of thespawning aggregations may be protected in no-take zones within the GBR network of marine protected areas (11,12,18).
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