|Scientific Name:||Plectropomus areolatus|
|Species Authority:||(Rűppell, 1830)|
Plectropoma areolatum Rűppell, 1830
Plectropoma areolatum Rűppell, 1830
Plectropomus areolatum (Rűppell, 1830)
Plectropomus areolatum (Rűppell, 1830)
Plectropomus areolatus (Rűppell, 1830)
Plectropomus trancatus Fowler and Bean, 1930
Plectropomus truncatus Fowler and Bean, 1930
|Red List Category & Criteria:||Vulnerable A4d ver 3.1|
|Assessor/s:||Thierry, C., Sadovy, Y. & Yeeting, B.|
|Reviewer/s:||Sadovy, Y. & Moss, K. (Grouper and Wrasse Red List Authority)|
Although this species has a wide range, it is heavily fished and is hence declining at a rate of at least 30% over the last 20 to 30 years, and this decline in the number of mature individuals is predicted to continue in the future as fishery pressure is predicted to increase. The species is particularly vulnerable and targeted at spawning aggregations both for the live reef fish trade as well as for dead fish, by spearing. There is very little management of the species for most of its range and effective management is unlikely to come into place soon.
Plectropomus areolatus is an Indo-Pacific species, known from the Red Sea, with a population in the Maldives and Chagos Island, disjunct at the coast of Southeast Asia (Myanmar and Thailand), and then from the Philippines, north to Ryukyu Islands (Japan); south to Indonesia, east and west Australia, Papua New Guinea, Solomon Islands and most of Micronesia.
Spawning aggregations are known from the Solomon Islands; in Palau, it aggregates in Ebiil, Western Entrance and Ngerumekaol; Pohnpei, Micronesia (Kehpara Marine Sanctuary, Palikir Pass, Ant Channel), Chagos Archipelago; Mundoo Channel, Maldive; Kiribati; aggregates outside and around passages in Abaiang atoll , Fiji. Other Pacific countries where they have been reported include Marshall Islands, Tuvalu, and Samoa. Occasional individuals are sighted in Milne Bay Province (Papua New Guinea) (Allen 1998).
Native:American Samoa (American Samoa); Australia; British Indian Ocean Territory; China; Cocos (Keeling) Islands; Djibouti; Egypt; Eritrea; Fiji; India; Indonesia; Israel; Japan; Jordan; Kiribati; Malaysia; Maldives; Marshall Islands; Micronesia, Federated States of; Myanmar; Nauru; New Caledonia; Palau; Papua New Guinea; Philippines; Samoa; Saudi Arabia; Solomon Islands; Somalia; Sudan; Taiwan, Province of China; Thailand; Timor-Leste; Tokelau; Tonga; Tuvalu; United States Minor Outlying Islands; Vanuatu; Wallis and Futuna; Yemen
|FAO Marine Fishing Areas:||
Indian Ocean – eastern; Indian Ocean – western; Pacific – northwest; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
Possibly the most abundant Plectropomus species in the central Western Pacific. However, there have been severe declines regionally, probably due in part to targeting spawning aggregations by local and foreign commercial fishers and the species is highly valued in the international live reef fish trade centered in Hong Kong (Sadovy and Vincent 2002). Although spawning can be induced in this species, it is not commercially raised in hatcheries (Tucker and Fitzgerald 1994; Sadovy, Y., pers. obs.).
In the Maldives, P. areolatus abundance is lower in the more heavily fished outer reef channels than in less intensely fished channels in the western side of Laamu Atoll (Sluka 2000). Stocks of P. areolatus was estimated at 1600 tonnes.
Kiribati and other Pacific locales
In Abaiang Atoll of the Gilberts Group, Kiribati, fishing targeting spawning aggregations was traditionally practiced but became very intensive in the 1980s when an Outer Island Fisheries Project was started. The Project buys fish from the outer islands to sell in the capital, Tarawa. During peak fishing season, daily catch of P. areolatus was estimated at two tonnes (about 1,200 individuals). A concurrent underwater visual survey showed a mean density of 0.13 individuals per 100 sq. m, with a mean individual length of 40 cm TL (Yeeting, unpublished data-1999). In 2004, a subsequent survey showed that mean density had declined to 0.04 individuals per 100 sq. m, with associated declines in mean size to 33 cm TL (ProcFish 2005). Other densities (per 100 sq. m) and mean length (cm TL) estimates are: Abemama, Kiribati: 0.19, 37; Chuuk, FSM: 0.0057, 50; Salelavalu, Samoa: 0.0072, 38; Funafuti, Tuvalu: 0.074, 44; Nukufetau, Tuvalu: 0.081, 37 (ProcFish 2005).
The species is apparently the most abundant live reef food fish species in the Fijian Islands (Yeeting et al. 2001).
In Pohnpei, the species forms aggregations from January to May within the Kehpara Marine Sanctuary, an enforced marine protected area (Rhodes et al. 2005). Aggregations also form at Palikir Pass (Pohnpei) and Ant Channel (Ant Atoll) that overlap temporally with those at KMS, although the size and temporal duration of Ant and Palikir aggregations are unknown; the latter sites are open to fishing and smaller in abundance to those of Kehpara (Rhodes and Tupper unpublished data). The species was the 6th most abundant serranid in marketed catches, contributing 12% to the Pohnpei spear and line serranid fishery over five months in 2006; the size range of marketed individuals was 211 to 513 mm TL, with a mean size of 352.0 +/- 55.4 cm TL (Rhodes and Tupper 2007). Individuals were captured predominantly by spear in inner reef locales, with immature individuals accounting for the majority of catch: 75.6% and 97.2% of marketed catch of females and males, respectively, below the mean size at sexual maturity (Rhodes and Tupper 2007).
In Komodo National Park, the species formed spawning aggregations during full moon periods from September to February and occasionally during new moon periods (Pet et al. 2005). During the 5-year monitoring program (1995-2000) at two sites within the Park, mean size declined by 8 cm, with heavy fishing continuing even following protection of the sites in 2001 (Pet et al. 2005); fish numbers at aggregations were low, less than 100 per aggregation site and period.
Solomon Islands and Papua New Guinea
At Roviana Lagoon (Solomon Islands), Hamilton and Kama (2004) identified seven spawning sites for P. areolatus through fisher interviews, with a reported peak in spawning activity between October and January during third quarter to new moon lunar phases. Hamilton and Smith (2005) report that 2 to 3 Manus fishers (Papua New Guinea) can remove an estimated 100 individuals per night from spawning sites using night-time spearfishing techniques, with associated declines in abundance and catch (Hamilton 2003). Catch-per-unit-effort records from Roviana estimate a catch rate of 16.8 kg/hr per fisher (41 fishing trips) (Hamilton et al. 2005). In Kavieng (Papua New Guinea), the live reef food fish trade (LRFFT) has operated on and off during the past decade and traditionally used traps and handlines to target spawning aggregations and reproductive migratory pathways, although trap fishing is now banned. A number of Kavieng sites have been systematically fished, with associated declines in abundance often severe. In Roviana, at least one P. areolatus aggregation was fished to economic extinction from the LRFFT (Hamilton et al. 2005) and coral reef damage was observed in association with this type of fishing at the same site (Rhodes pers. obs.). In Roviana, LRFFT operations between 1996 and 1997 removed an estimated 3 to 4 tonnes of the serranids, including P. areolatus (Hamilton and Kama 2004) during 24-hour daily fishing operations.
|Habitat and Ecology:||
P. areolatus inhabits lagoon and seaward reefs, in areas with rich coral growth. Most frequently encountered in channels along the reef front. Often a shy fish, but will take bait during reproductive periods. Feeds exclusively on fishes. May be ciguatoxic in some areas. Forms spawning aggregations in association with specific lunar phases, with variable seasonality and lunar cycle associated with spawning by locale. The species commonly co-aggregates with the camouflage grouper, Epinephelus polyphekadion, and brown-marbled grouper, E. fuscoguttatus throughout its range. Aggregation-associated abundances can number in the 1,000s of individuals (Conservation Society of Pohnpei unpublished data), although in many area, spawning aggregations may be naturally small, composed of 10s to 100s of individuals (Hamilton pers. Comm.). A total of 5781 individuals were recorded at the Kehpara Marine Sanctuary spawning site during monitoring in three days during peak aggregation periods in 2001 (Pet et al. pers. Comm.). Natural variations in mean size may occur between locales, but this phenomenon has not yet been confirmed and may be attributed to fisheries-induced changes in population structure.
Initial data suggests that some aggregations that appear within the presumed reproductive season, including some of substantial size, may not be reproductive and composed entirely, or nearly so, of a single sex, as demonstrated by fisheries data collected in January 2005 over a 5-day period leading up to the 'normal' full moon spawning time associated with the species in Pohnpei (Rhodes and Tupper unpublished data). Although there was no fisheries-independent data to support all-male aggregations, fishing over similar periods in subsequent aggregation months (February-May) resulted in a minimum of 1:4 female-to-male sex ratio to suggest that several females would have been captured in January of present. If confirmed, fishing on large, same-sex aggregations could impact sex ratios during subsequent reproductive periods in a manner similar to that shown for other aggregating serranids (Koenig et al. 1996).
In Abaiang Atoll of the Gilberts Group, Kiribati, local knowledge indicates a September to February spawning season, with spawning peak in early December. Occasional individuals sighted at 2 to 30 m, in coral reefs of Milne Bay Province, Papua New Guinea (Allen 1998).
Mature females ranged between 347 and 510 mm FL, mature males between 390 and 557 mm. Immature fish ranged from 300 to 345 mm, so sexual maturation was attained at about 346 mm, but size distribution varied significantly between study aggregations. In 1996, no recruitment was observed within the smallest size category of females moving into Ebiil and Western Entrance spawning aggregations and negligible recruitment occurred at Ngerumekaol, suggesting larval settlement of P. areolatus 2 to 3 years earlier may have been very low. About 5-10 times as many females as males were counted in the most lightly fished area (Western Entrance), while spawning aggregations in more heavily fished areas Ngerumekaol (highest female: male (f:m) ratio recorded was 1:5 during peak aggregation) and Ebiil sites, f:m ratio exceeds one only at Western Entrance and Solomon Island (Johannes et al. 1999).This sex ratio may be responsible for the aggressive behavior observed between sexes and may have prevented spawning. Sex and size structure in spawning aggregation should be monitored where fishing on spawning aggregations occurs.
In Pohnpei, marketed fish were derived primarily from inner reef locales using spear (Rhodes and Tupper 2007). Individuals taken during a tagging exercise in Pohnpei had a mean size for mature females of 390+/-30 cm SL, with males averaging 462+/-28 cm SL. Mature females ranged from 318-469 cm SL, while males were found between 390-570 cm SL (Rhodes and Tupper unpublished data).
One of the earliest records of spawning aggregations of P. areolatus was in the Solomon Islands (Johannes 1988). Johannes noted aggregations in two outer reef passages and counted no more than 100 fish at any one time.
The major threat to Plectropomus areolatus is the commercial live reef food-fish trade. The species is taken for both live and fresh/dead for international and national trade using a combination of line, trap and possibly chemicals (sodium cyanide). It is sold in Hong Kong live reef fish food market, with the highest proportion at 35-45 cm length. Import to Hong Kong was 2319 tonnes in 1997, maturity size range is 31-35 cm TL, common consuming size is 38.24 –50.21 cm TL (Lau and Parry-Jones 1999). Much of the foreign commercial fishing targets spawning aggregations (Sadovy et al. 2003). In Pacific countries it is the most abundant and main target grouper species for the Live Reef Fish Food Trade.
Although subsistence use is not usually considered a main threat, a recent survey of serranids in Pohnpei showed that Plectropomus areolatus comprised >12% of serranids targeted by the spear and line fishery, with the majority of the catch composed of juveniles (Rhodes and Tupper 2007). Local commercial fishers are also responsible for targeting spawning aggregations and reproductive migratory pathways, resulting in reduced abundances following heavy fishing (Rhodes and Tupper unpublished data; Johannes et al. 1999; Hamilton and Kama 2004).
In the Solomon Islands (and likely elsewhere), P. areolatus moves to shallow reef habitats (e.g. reef flat) at night within spawning aggregation periods. These areas are easily accessible to fishers, who can obtain exceptionally high catches over short periods of time (Johannes 1988); mean night-time CPUE was significantly higher than during the daytime (Hamilton et al. 2005). Marovo (Solomon Islands) fishermen state that the average size of aggregations of P. areolatus has been diminishing since spearfishing became widely practiced in the area. Increasing human population in the Western Solomon Islands (doubling about every 17 years) is also exerting pressure on the species. Johannes suggests that aggregation fishing should be managed or banned in the Solomon Islands, where aggregations occur in multiple and often closely spaced (kms) locations, because heavy fishing pressure is likely to rapidly deplete them (Johannes and Kile 2001). Hamilton (unpublished manuscript) reports that night-time spear fishing poses a threat to spawning aggregations of the species because the high hourly catch rates possible using this method could rapidly deplete aggregations.
According to Noah Idechong, at least four spawning aggregations have disappeared since the 1970s in Palau, including one composed primarily of P. areolatus. Sites include Rebotel, Mesikm near German Channel and Uchul a Chei on the southern tip of Ngermediu reef (lost in the 1970s). An aggregation site of P. areolatus and E. fuscoguttatus was virtually eliminated at Denges in the late 1980s by a live grouper export fishing enterprise (Johannes et al. 1999). Possibly as a result of fishing pressure, the P. areolatus aggregation at Ebiil has been reduced to aggregating one only one of two sides of the channel (Johannes et al. 1999). Plectropomus areolatus, along with Epinephelus fuscoguttatus and Epinephelus polyphekedoin, dominate the commercial catch of groupers in Palau (Kitalong and Dalzell 1993).
P. areolatus occurs in several protected areas throughout its range, including some specifically designed to protect spawning aggregations (Rhodes et al. 2005). Seasonal closures associated with spawning times are also in place in some areas (Rhodes and Sadovy 2002). Size-limits and catch quotas have also been imposed in various sites in Australia.
The Marine Protection Act of 1994 prohibits sale or purchase of P. areolatus (and E. polyphekadion or E. fuscoguttatus) from April 1 through July 31 each year, intended to protect spawning aggregations. In 1995 the Act was amended to prohibit any capture of these groupers even for subsistence purpose in the closed period (Johannes et al. 1999). A four-month bul (taboo) was enforced in the state of Ngeremlengui, but not completely effective in preventing fishing on the spawning aggregation.
A sales ban is enforced on all groupers, including the squaretail coralgrouper, during March and April, which coincides with a portion of its January-May spawning season (Rhodes and Tupper 2007).
Size limit: minimum 38 cm TL and a total combined bag limited seven individuals (coralgrouper), applied across all sectors of the coral reef fin fish fishery that includes commercial and recreational fishers, and charter boat operators. The minimum size limits is designed to ensure that at least half of the fish in a population reach reproductive maturity and spawn before harvest.
|Citation:||Thierry, C., Sadovy, Y. & Yeeting, B. 2008. Plectropomus areolatus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 19 May 2013.|
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