Habitat and Ecology
Sexual maturation in the female occurs at about 23-24 cm SL, or about three years old (Tseng and Ho 1988). The oldest fish found by two studies was seven years (Tseng and Ho 1988, Hung 1994). The generation time is therefore assumed to lie between 3-7 years. Hung also provides figures for the percentage of the annual catch off Fujian province that falls in each age class. The mean age of adults was four years but the extremes of three and seven are still used as this subpopulation would have been fairly heavily exploited. Four years was, however, used as the point estimate in the species assessment. The growth in mariculture operations for valuable grouper species has prompted an interest in obtaining broodstock for spawning and hatchery rearing. Males of E. akaara (males are larger than females) are very difficult to obtain, another indication of the severe depletions indicated for this species (Patrick Chan, pers. comm. 2002).
There is no information in the (sparse) literature to suggest that Hong Kong grouper aggregate to spawn. However, a knowledgeable recreational diver who has dived in Hong Kong reported seeing up to 50 individuals close together on the reef on several occasions (Patrick Chan, pers. comm. 2001) during summer indicating spawning aggregations may have occurred in the past. None have been reported in the last few decades, however, and this species is no longer common in Hong Kong. Attains 35 cm SL (Masuda et al. 1984). The Japanese All-tackle record for Hong Kong grouper is 1.65 kg (Japanese Game Fishing Association 2001).
Water temperature and chemistry ranges based on 2 samples.
Depth range (m): 5 - 6.7
Temperature range (°C): 23.822 - 23.822
Nitrate (umol/L): 0.343 - 0.343
Salinity (PPS): 32.495 - 32.495
Oxygen (ml/l): 4.847 - 4.847
Phosphate (umol/l): 0.441 - 0.441
Silicate (umol/l): 15.721 - 15.721
Depth range (m): 5 - 6.7
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
IUCN Red List Assessment
Red List Category
Red List Criteria
Declines in landings are assumed to reflect declines in Hong Kong grouper stocks unless it is known that fishing effort has decreased or other factors are involved. The mean percentage decline of Hong Kong grouper (excluding Hong Kong and Taiwan which appear to have negligible populations of Hong Kong grouper) from China (90%), Japan (50%) and Republic of Korea (50%) is 63 %.
Ideally, the percentage decline would be applied to estimates of the original Hong Kong grouper population within each country for which the decline applies. This would be done for all countries and the overall decline would be the percentage difference between the original global population size and the current one. Unfortunately, estimates of country stock size are non-existent for this species. The declines were therefore weighted by rocky reef area (rather than by population size) to give an overall decline figure. This method assumes that pristine densities of Hong Kong grouper were the same at all localities. This is probably not likely to have been the case but it enables a single figure to be derived which is likely more representative of the global situation than the alternative, which is just to say the decline lies between 50 and 90% (the lowest and highest decline rates).
It is worth noting that simply taking the mean of all decline figures gave a very similar figure, 63% rather than 65%.
The Hong Kong grouper is the most expensive of all the Epinephelus groupers in Hong Kong. It is known from anecdotal accounts that the abundance of this fish has declined considerably from the 1960s to late 1990s in Hong Kong waters (see Sadovy and Cornish 2000).
Moreover, supply of Hong Kong grouper seed (i.e., the fry and fingerlings), which was the favoured species for mariculture in southern China, is known to have significantly decreased in abundance (the small fish are taken from the wild and then are grown up to market size in captivity). For example, the seed was abundant in Fujian (a province of mainland China) waters in the early 1980s but was very rare by 1994 (Sadovy 2000). In 1979, Hong Kong culturists purchased, for grow-out, at least 180,000 kg of this species (200,000-450,000 fish of 100-200 g) that had been wild-caught from southern China, today seed of this species from China is rare (Sadovy 2000). It was reported that Hong Kong grouper landings could not keep up with demand by the late 1970s and that prices had risen from HK$ 33-50/kg in 1978 to HK$ 50-70/kg in 1979 as a result (Tseng and Ho 1988). Juveniles are no longer readily available from Hong Kong either (Sadovy and Cornish 2000).
There is a serious lack of time-series data from annual landings, CPUE, underwater visual census from countries in the North-West Pacific where this species is distributed. Such data would greatly increase the accuracy of future assessments.
Ideally, each country would conduct a full stock assessment on this species, which would calculate population size as well as rates of decline. It would also be useful to know from genetic studies whether there are subpopulations within the range of this fish.
Knowledge of natural reproductive behaviour in the wild, particularly whether the species aggregates to spawn (and where and when), would be of use in managing stocks of this species in the wild.
Hong Kong grouper
The Hong Kong grouper (Epinephelus akaara) is a species of fish in the Serranidae family. It is found in China, Japan, North Korea, Taiwan, and possibly Vietnam. Its natural habitats are shallow seas and coral reefs.
- Cornish, A. 2003. Epinephelus akaara. 2006 IUCN Red List of Threatened Species. Downloaded on 4 August 2007.
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