|Scientific Name:||Metanephrops australiensis (Bruce, 1966)|
Nephrops australiensis Bruce, 1966
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Wahle, R., Butler, M., Chan, T.Y., Cockcroft, A. & MacDiarmid, A.|
|Reviewer(s):||Collen, B., Livingstone, S. & Richman, N.|
|Contributor(s):||Batchelor, A., De Silva, R., Dyer, E., Kasthala, G., Lutz, M.L., McGuinness, S., Milligan, H.T., Soulsby, A.-M. & Whitton, F.|
Metanephrops australiensis has been assessed as Least Concern. Although this species is harvested commercially and it is thought that there is a decline in abundance, this is complicated by the apparent recent decline in fishing effort. At present the fishery is thought to be 'stable' as there is no evidence of it being 'mined', or of growth over-fishing. However, it is recommended that populations off the northwest coast of Australia continue to be monitored, with the possibility of stricter controls on the fishery in the future.
|Range Description:||This species occurs off the northwest coast of Western Australia, near Port Hedland (Holthuis 1991). Its distribution may extend northwards to Indonesia and the Philippines, although records outside Australia are patchy (Chan 1997).|
Native:Australia (Western Australia)
|FAO Marine Fishing Areas:|
Indian Ocean – eastern; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||This species is abundant off the northwest coast of Australia, but spread unevenly across this part of its range (Poore 2004). It is rarely found in the Philippines and Indonesia (Chan 1997). Measures of population abundance (e.g., catch per unit effort) show fluctuations both annually and seasonally, but a steady decline since 1985 is apparent (Lynch and Garvey 2005).|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||This species occurs on Globigerina at depths of 418 m to 500 m (Holthuis 1991, Australian Faunal Directory 2008). It commonly feeds on other crustaceans, but also fish and squid (Wassenberg and Hill 1989). Females are thought to mature at 4+ years (~ 40 mm carapace length), and maximum lifespan is 10-12 years (Rainer 1992). Clutch size is approximately 1,200 eggs (R. Wahle pers. comm. 2009).|
|Generation Length (years):||4|
|Use and Trade:||
This species is trawled off northwest Australia and sold as luxury food (Poore 2004). A commercial fishery is being developed, for which CSIRO Division of Fisheries is collecting biological data (Poore 2004). The annual catch (in tonnes) of Metanephrops spp. in the North West Slope Trawl Fishery (NWSTF) between 1985 and 2003 is as follows (data from Lynch and Garvey 2005):
1985 - 27.6; 1986 - 26.2; 1987 - 31.0; 1988 - 24.9; 1989 - 24.5; 1990 - 15.9; 1991 - 8.9; 1992 - 13.9; 1993 - 0.6; 1994 - 12.4; 1995 - 7.3; 1996 - 9.1; 1997 - 16.4; 1998 - 6.0; 1999 - 11.5; 2000 - 20.5; 2001 - 21.4; 2002 - 6.1; 2003 - 22.8
Catches of this species as a proportion of all three Metanephrops spp. ranged from 12% to 43%, with a mean of 23.6%.
This species is fished commercially by trawlers off the northwest coast of Australia. It was the most abundant lobster off the northwest Australian coast, making up 38% of the Metanephrops catch in the 1980s (Wallner and Phillips 1988). In 1984 this species made up 32.5% of the total trawl catch by weight, compared to 50% shrimps, 12.1% M. velutinus, and 5.4% M. boschmai (Davis and Ward 1984).
Since 1985, when the commercial fishery began in earnest, annual catches have fluctuated (see "Use and Trade") but there has been an overall steady decline in catch volume of around 44 % over three generations (for calculations see below; data from Lynch and Garvey 2005). However, this has coincided with a decrease in fishing effort (hours trawled) which complicates interpretations of decreasing catch volume (Lynch and Garvey 2005).
Data for catch per unit effort (CPUE) for all three commercial Australian lobster species shows an overall decline from around 14 kg/hr in 1985 to 9 kg/hr in 2003 (assuming an increase in fishing power of 1% per annum), with the lowest levels recorded in 2002 (Lynch and Garvey 2005). CPUE data is available for this species at one fishing ground (Rowley Shoals); this shows a linear decline over three generations from approx. 11 kg/hr in 1991 to 9 kg/hr in 2003. This amounts to an approx. 18 % decline over the period (Lynch and Garvey 2005).
Despite this, it is not believed that this species is being significantly impacted by commercial trawling (Lynch and Garvey 2005). This is due to several factors: firstly, there is no evidence that the fishery is being "mined" (vessels continuously find new areas of high abundance which are exploited until depletion, gradually fishing down the entire stock until a sudden and unanticipated collapse occurs), as most of the fishing grounds have been in constant use since 1985; secondly, a comparison of length frequencies between the early years of the fishery and 2004 shows no significant change in the size range of scampi being caught, giving evidence that CPUE's are not being distorted by "growth overfishing" (the practice of targeting greater numbers of smaller scampi to sustain total catch volumes) (Lynch and Garvey 2005).
* Calculations for catch volume decline:
Age at maturity = 4 years. Longevity = 12 years (Rainer 1992).
Generation length = longevity - maturity / 2 = (12 - 4 )/ 2 = 4 years.
Three generations = 1991 to 2003: volume in 1991 = 18 tonnes; 2003 = 10 tonnes. Decline = 44%.
|Conservation Actions:||There are no species-specific conservation measures in place for this species. It is recommended that populations and harvest levels off the northwest coast of Australia continue to be monitored, with the possibility of stricter controls on the fishery in the future.|
|Citation:||Wahle, R., Butler, M., Chan, T.Y., Cockcroft, A. & MacDiarmid, A. 2011. Metanephrops australiensis. The IUCN Red List of Threatened Species 2011: e.T169965A6694390.Downloaded on 25 September 2017.|
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