Table 1: Stock status determination for Eastern King Prawn
Jurisdiction |
New South Wales, Queensland |
Stock |
Eastern Australian
(ECOTF, EGF, EPTF, OTF-PS) |
Stock status |
|
Sustainable |
Indicators |
Proportion of unfished biomass, CPUE, yield-per-recruit analyses |
CPUE = catch per unit effort; ECOTF = East Coast Otter Trawl Fishery (Queensland); EGF = Estuary General Fishery (New South Wales); EPTF = Estuary Prawn Trawl Fishery (New South Wales); OTF-PS = Ocean Trawl Fishery–Prawn Sector (New South Wales)
Eastern King Prawn is one of two Australian species (the other being Western King Prawn) recognised by the standard fish name 'King Prawn'1. Eastern King Prawns are harvested in Queensland and New South Wales fisheries and are considered a single multi-jurisdictional biological stock2–3. There are two contiguous management units for the stock: one from 22 to 28ºS in Queensland, and another along the whole New South Wales coast (28–37.5ºS). A comprehensive assessment of recruitment dynamics and optimal yield of the whole Eastern King Prawn fishery biological stock is under way. Status determination is made on the basis of the single multi-jurisdictional biological stock.
Eastern Australian biological stock
The most recent quantitative stock assessment undertaken on the biological stock3 estimated maximum sustainable yield (MSY) at 2612 tonnes (t) (90 per cent confidence interval 1694–4065 t) and effort at MSY (EMSY), standardised to the number of boat nights in 2001, as 25 664 boat nights (90 per cent confidence interval 15 477–67 447 boat nights). Although the overall trend in nominal trawl effort in both Queensland and New South Wales has declined in recent years, from around 30 000 boat days in 2000 to less than 20 000 boat days in 2009–10, the fishing power of vessels has increased by around 50 per cent over the past two decades4. The decline in nominal effort has been offset by the increase in fishing power, leading to higher catch rates and record harvests in Queensland in recent years5.
Population modelling6 indicated that the New South Wales part of the biological stock was very resilient under the assumption of stable levels of recruitment from Queensland. From 2008 to 2010, total landings from Queensland and New South Wales exceeded 3000 t. Although this catch exceeds the MSY estimate, it is within the 90 per cent confidence intervals of the mean. Given that catch and standardised catch per unit effort have been fairly stable over the past 20 years, it is unlikely that the biological stock is recruitment overfished.
It is unlikely that fishing effort will increase in this fishery, given the increasing costs of production (fuel, labour, etc.). The catch of prawns in 2010, although higher than in 2009, was within the range observed in the past 10 years. The current level of fishing mortality is unlikely to cause the biological stock to become recruitment overfished.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
Table 2: Eastern King Prawn biology7
Longevity and maximum size |
3 years; males 4.7 cm CL, females 6.1 cm CL |
Maturity (50%) |
Females 4 cm CL |
CL = carapace length
Figure 1: Distribution of reported commercial catch of Eastern King Prawn in Australian waters, 2010
Note: There is very little catch and effort of Eastern King Prawn north of 20°S.
- Commercial fishing is undertaken using demersal prawn otter trawl gear, set pocket and seine nets. Recreational fishing is predominantly undertaken using hand-held nets.
- A range of input controls are applied to the Eastern King Prawn biological stock. These include restrictions on gear, restrictions on the number of licensed vessels entitled to access the stock, spatial and temporal closures, and mandatory use of bycatch reduction devices. Queensland has effort limits that apply across the entire East Coast Otter Trawl Fishery (Queensland) and the area specific to the Eastern King Prawn component of the fishery.
- The number of commercial vessels that caught Eastern King Prawns in 2010 was 241 in Queensland and 200 in New South Wales.
- The total amount of Eastern King Prawn caught commercially in Australia in 2010 was 3513 t, comprising 2812 t in Queensland and 701 t in New South Wales. There is a recreational fishery for Eastern King Prawns in New South Wales, but not in Queensland. The recreational catch in New South Wales was estimated to be below 110 t8. There is no recognised Indigenous fishery for this species. Indigenous catch is unknown, but likely to be negligible.
a)
b)
Figure 2: a) Commercial catch of Eastern King Prawn in Australian waters, 2000–10 (calendar year);
b) standardised catch per unit effort throughout eastern Australian marine areas, 1988–2010
Total catch of Eastern King Prawn was 3513 t in 2010, with around 80 per cent taken in Queensland. Combined catches in 2008–10 were higher than the most recent MSY estimate; however, there are wide confidence intervals associated with this estimate3. This pattern is against a background of declining fishing effort and rising standardised catch rates (Figure 2b) over the same period.
- Species caught incidentally by trawl nets are discarded, either because they have low market value or are not permitted to be retained. Bycatch consists mainly of small fish, crabs, other penaeid prawns and numerous other bottom-dwelling invertebrate species, including sponges, sea stars and gastropod shellfish.
- The mandatory use of bycatch reduction devices has been shown to reduce bycatch in the trawl fisheries9–11.
- Interactions known to occur between the fishing gear used to target Eastern King Prawn and protected species, such as sea turtles and sea snakes, are partly mitigated by mandatory use of turtle excluder and other bycatch reduction devices.
- Climate change is likely to have a significant long-term effect on the distribution of this species. Under a scenario of increasing sea surface temperatures, a strengthening East Australian Current and changing freshwater flows, the distribution of Eastern King Prawn may shift southwards, potentially impacting recruitment and the timing of migration2,12.
- An analysis of 23 years of daily logbook catches of Eastern King Prawns in Moreton Bay13 suggests that, under a climate change scenario of increasing coastal water temperatures, the abundance of Eastern King Prawn recruits in spring and early summer is likely to decline, resulting in a slight long-term reduction in abundance in south-east Queensland.
- Destruction of seagrass beds and alteration of water flows in estuaries could affect the area of nursery grounds available to recruiting prawns. This may affect the size of the biological stock available for capture.
a Department of Agriculture, Fisheries and Forestry, Queensland
b Department of Primary Industries, New South Wales