|Scientific Name:||Hyporthodus quernus|
|Species Authority:||(Seale, 1901)|
Epinephelus quernus Seale, 1901
Hyporthodus quernus (Seale, 1901)
|Taxonomic Notes:||A recent publication changed the generic name of this species to Hyporthodus (Craig and Hastings 2007) and a change of family name to Epinephelidae (Smith and Craig 2007).|
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Assessor/s:||Cornish, A. (Grouper & Wrasse Specialist Group)|
|Reviewer/s:||Sadovy, Y. & Eklund, A.-M. (Grouper & Wrasse Red List Authority)|
Hyporthodus quernus shows several characteristics that make it susceptible to overexploitation, and potentially, extinction:
i). It has a small global distribution.
ii). Like many other groupers it appears to be sex-changing (see Habitat and Ecology), with males not changing from females until large size (around 75 cm) and probably relatively old age.
iii). Sex ratios in one study in 1978–1981 were heavily skewed towards females (see Habitat and Ecology), and may become more so, if fishing is targeted towards the largest individuals (males). Heavily skewed sex ratios may lead to reductions in reproductive output.
Populations of H. quernus have evidently been overexploited over the past 10 years as demonstrated by:
i). A 53% decline landings data of Hawaiian Grouper per trip in the Ho'omalu zone and a 33% decline in the Mau zone from 1992–2001.
ii). A decline in the spawning potential ratio throughout all of the Hawaiian archipelago from 70–48 from 1989–2001 and the Main Hawaiian islands alone of 58–28.
iii). Smaller individuals caught in the more heavily exploited MHI (5 to 10 pounds) versus those from the NWHI (10 to 30 pounds).
iv). A general trend of decreasing catch per unit effort (CPUE) (pounds per trip) of this fish in the Main Hawaiian Island (MHI). In early 90's it was about 100–150 while became stable at about 50–100 from 1995 to 2000.
Follow the link below for more detailed catch data.
All indications are that stocks have been most seriously depleted in the Main Hawaiian Islands (MHI). However, there does appear to have been a slight recovery, or at least a stabilization, in stocks, (possibly due to increased regulations on fishing bottomfishes in 1998), as evidenced by increasing Spawning Potential Ratio (SPR) figures from 1998 to 2001.
Although, fishing pressure on H. quernus has undoubtedly reduced the global population of this susceptible species, changes in fisheries management for this species in 1998 make it impossible at this time to determine whether decreases in landings, and catch per trip are due to declining populations or changes in management. CPUE data would be most useful in resolving this but this information does not appear to have been released in recent years. Due to these substantial data gaps, it is not possible to estimate, infer or suspect whether the size of population reductions over the last 10 years, or three generations, is more than 30% (i.e., VU A2d) and H. quernus is, therefore, classified as Near Threatened.
Despite clear local depletions of H. quernus stocks, there is no evidence for a genetic bottleneck or loss of genetic diversity due to overfishing, indicating stocks are genetically healthy enough to recover over time given continual monitoring and revision of the boundaries of the three main management zones to reflect actual patterns of genetic diversity (Rivera 2002).
In particular, the limited geographic distribution of this species makes it intrinsically vulnerable to fishing and further data should be integrated into species assessments as the former become available. Close attention should be paid to landings of this species.
|Range Description:||Found in the Central Pacific and limited to the Hawaiian Islands and Johnston Atoll (Heemstra and Randall 1993).|
Native:United States (Hawaiian Is.); United States Minor Outlying Islands (Johnston I.)
|FAO Marine Fishing Areas:||
Pacific – eastern central
|Range Map:||Click here to open the map viewer and explore range.|
A study of the population genetic structure in the Hawaiian archipelago indicates "populations of H. quernus may be in the order of at least ¾ of a million individuals" but inaccuracies in the model could result in large changes to this estimate and it should, therefore, be viewed with caution (Rivera et al. 2004).
Population doubling time is 1.4–4.5 years (FishBase 2003).
302 individuals of H. quernus were taken from ten sites throughout the Hawaiian archipelago in 1999–2001 at depths of 140–381 m. Examination of genetic diversity showed that that Gardner Island, situated about mid-way along the island chain had the greatest genetic diversity, and the second highest proportion on unique alleles. The northern-western (Mar/ N. Hampton through Pear and Hemes islands) and southern-eastern (Hawaii through Nihoa) extreme ends of the archipelago had genetic composition that was largely similar which may suggest the more diverse middle islands served as an ancestral source to the rest of the archipelago. As such, additional consideration should be given to preserving H. quernus stocks in the middle islands (Rivera et al. 2004).
|Habitat and Ecology:||
Hyporthodus quernus is a demersal fish occurring from 20–380 m. It occurs in coral reef and rocky areas.
Hyporthodus quernus appear to be a protogynous hermaphrodite, changing sex from female to male at a large size. A study examining 133 individuals in 1978–1981 found 50% of females had reached sexual maturity by 57.5–62.5 cm while the smallest male was 75 cm and 100% of individuals above 95 cm were male (Everson 1992). The same survey found a skewed sex ratio as 120 of the samples were female and only 10 (8%) were male. H. quernus has a protracted spawning season that extends from January through June. Spawning reached a peak in April, and again in June (Everson 1992).
|Major Threat(s):||Overfishing is the most serious actual or potential threat.|
The Fishery Management Plan for Bottomfish and Seamount Groundfish Fisheries in the western Pacific Region (FMP) became effective on 27 August 1986. The FMP prohibits destructive fishing techniques, establishes a moratorium and implements a permit system for fishing for bottomfish in the Exclusive Economic Zone (EEZ) around the NWHI; it also establishes a limited access permit program for the Mau Zone, a management area in the NWHI with effect from 28 May 1999 (Western Pacific Regional Fishery Management Council 2003).
Hawaii Administrative Rule established June 1998 prohibits use or possession of nets, traps, trawls, or bottomfish longline in fishing for bottomfish including H. quernus; it establishes restricted fishing areas which prohibits fishing of this fish within such areas; and it also requires vessels to register with Department of Aquatic Resources (DLNR) to legally take and possess bottomfish species (DAR 2002).
|Citation:||Cornish, A. (Grouper & Wrasse Specialist Group) 2004. Hyporthodus quernus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 07 March 2014.|
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