Table 1: Stock status determination for Barramundi
Jurisdiction |
Northern Territory |
Queensland |
Western Australia |
Stock |
BF |
ECIFFF |
GOCIFFF |
KGBF |
Stock status |
|
|
|
|
Sustainable |
Sustainable |
Sustainable |
Undefined |
Indicators |
Catch, CPUE, length and age frequencies, harvest rate, recruitment |
Catch, CPUE, length and age frequencies |
Catch, CPUE, length and age frequencies |
Catch, CPUE |
BF = Barramundi Fishery (Northern Territory); CPUE = catch per unit effort; ECIFFF = East Coast Inshore Fin Fish Fishery (Queensland); GOCIFFF = Gulf of Carpentaria Inshore Fin Fish Fishery (Queensland); KGBF = Kimberley Gillnet and Barramundi Fishery (Western Australia)
Separate biological stocks of Barramundi have been found to exist at the scale of individual catchments across northern Australia1. However, difficulty in obtaining relevant biological and catch-and-effort information to assess each biological stock individually has meant that Barramundi has been assessed as four separate management units (Northern Territory, Queensland—east coast, Queensland—Gulf of Carpentaria, and Western Australia). The assessments of these units are based on the stocks that receive the highest harvest rates. The stock status can therefore be assumed to be representative of the highest level of exploitation that occurs on any stock within each management unit.
Barramundi Fishery (Northern Territory) management unit
Commercial catches are stable and well within historical levels, and monitored stocks all have a healthy size and age distribution2. Commercial catch rates have increased substantially in the past four years, with 2010 having the second highest rate ever recorded. Recaptures from tagging programs suggest that the annual harvest rate from all sectors combined is consistently below 5 per cent, and abundance surveys indicate high levels of recruitment during high-rainfall wet seasons2. This evidence indicates that the stocks are unlikely to be recruitment overfished and that current catch levels are unlikely to cause the stocks in this management unit to become recruitment overfished.
On the basis of the evidence provided above, the management unit is classified as a sustainable stock.
East Coast Inshore Fin Fish Fishery (Queensland) management unit
Commercial catches are stable and within historical levels, and catch rates have increased substantially over the past 10 years3. The Long Term Monitoring Program routinely collects fishery-dependent samples for ageing along the east coast4. Assessment of Barramundi age structures indicated strong recruitment into the fishery in the north-east region in 2009 and the central region in 2010, and a good range of fish lengths and ages across several years3. This evidence indicates that the biomass of these stocks is unlikely to be recruitment overfished and that current catch levels are unlikely to cause the stocks in this management unit to become recruitment overfished.
On the basis of the evidence provided above, the management unit is classified as a sustainable stock.
Gulf of Carpentaria Inshore Fin Fish Fishery (Queensland) management unit
Commercial catches are stable and within historical levels, and catch rates have increased substantially over the past 10 years5. Fishery-dependent samples that have been collected for ageing in the Gulf of Carpentaria in recent years indicate strong recruitment into the fishery during 2006–10 and a good range of fish lengths and ages across several years5– 6. This evidence indicates that the biomass of these stocks is unlikely to be recruitment overfished and that current catch levels are unlikely to cause the stocks in this management unit to become recruitment overfished.
On the basis of the evidence provided above, the management unit is classified as a sustainable stock.
Kimberley Gillnet and Barramundi Fishery (Western Australia) management unit
In Western Australia, the target catch range for Barramundi (25–40 tonnes [t]) is derived from a forecasting model of the annual Barramundi catches of the Kimberley Gillnet and Barramundi Fishery up to and including 1999 only7. For the five years from 1999 to 2003, the level of Barramundi catch was at the top end of the target catch range. The catch in 2004 exceeded the target range, although this was achieved at a catch per unit effort (CPUE) that suggested higher abundance levels than during the 1980s and 1990s7. The Barramundi catch in 2010 was above the target range. The catch rate for this species is now declining, and the overall catch rates for the fishery are also declining; however, it is unknown whether the current catch is likely to cause this management unit to be recruitment overfished, because catch rates have been variable in this fishery for the past 10 years. Until a consistent pattern of decline in CPUE occurs in this management unit, its status cannot be assessed.
On the basis of the evidence provided above, the management unit is classified as an undefined stock.
Table 2: Barramundi biology8
Longevity and maximum size |
20 years; 150 cm TL, 50 kg |
Maturity (50%) |
Northern Territory: males 73 cm TL (2–5 years); females 91 cm TL (5–7 years)
Queensland: males 64 cm TL (2–5 years); females 82 cm TL (5–7 years) |
Figure 1: Distribution of reported commercial catch of Barramundi in Australian waters, 2010
- Commercial catch of Barramundi is predominantly taken using monofilament gillnets, whereas recreational fishers use rod and reel with bait or artificial lures.
- A range of input and output controls are in place across jurisdictions:
- Input controls include limited entry to all commercial fisheries, gear restrictions, temporal closures (typically between October and February to protect spawning fish) and spatial closures.
- Output controls include size limits and possession limits.
- In 2010, Barramundi catch was reported from 20 vessels in the Barramundi Fishery (Northern Territory), 144 vessels in the East Coast Inshore Fin Fish Fishery (Queensland), 77 vessels in the Gulf of Carpentaria Inshore Fin Fish Fishery (Queensland) and 7 vessels in the Kimberley Gillnet and Barramundi Fishery (Western Australia).
- Total commercial catch of Barramundi across Australia in 2010 was 1676 t, comprising 635 t in the Northern Territory, 254 t in the East Coast Inshore Fin Fish Fishery (Queensland), 730 t in the Gulf of Carpentaria Inshore Fin Fish Fishery (Queensland) and 57 t in the Kimberley Gillnet and Barramundi Fishery (Western Australia)2–3,5,7.
- Recreational fishing surveys were not conducted across all jurisdictions in 2010, but historical surveys suggest that the harvest by this sector is approximately 303 t, comprising 251 t in the Northern Territory9, 51 t in Queensland10 and 1 t in Western Australia7. Charter operators caught 57 t in 20102–3,5,7. Surveys of Indigenous catch are rare; however, in 2000 this sector harvested approximately 110 t in the Northern Territory9.
a)
b)
Figure 2: a) Commercial catch of Barramundi in Australian waters, 2000–10 (calendar year);
b) catch per unit effort for all Barramundi fisheries, 2000–10 (calendar year)
In the Barramundi Fishery (Northern Territory), large catches of Barramundi were recorded in 2001 (1004 t), followed by a steady decline until 2007 (492 t). Since then, catches have increased substantially to 635 t (Figure 2a). In the Northern Territory, recent large wet seasons have promoted high recruitment, and high catches are forecast for the next 2–3 years2. Catch per unit effort (CPUE) has followed the same pattern as catch; the 2010 value of 31.2 kg/hundred metres of net/day (kg/HMD) is the second highest value recorded in the history of the fishery (Figure 2b).
Barramundi catch decreased from 301 t (in 2009) to 254 t (in 2010) in the East Coast Inshore Fin Fish Fishery (Queensland), and from 790 t (in 2009) to 730 t (in 2010) in the Gulf of Carpentaria Inshore Fin Fish Fishery (Queensland). In both fisheries, catches have been variable, with no consistent pattern (Figure 2a). Despite the variability in catches, CPUE steadily increased from 14.3 kg/HMD in 2002 to 21.8 kg/HMD in 2009 in the East Coast Inshore Fin Fish Fishery (Queensland), and from 17.9 kg/HMD in 2001 to 24.9 kg/HMD in 2009 in the Gulf of Carpentaria Inshore Fin Fish Fishery (Queensland). In 2010, CPUE declined slightly to 18 kg/HMD in the East Coast Inshore Fin Fish Fishery (Queensland) and to 21.7 kg/HMD in the Gulf of Carpentaria Inshore Fin Fish Fishery (Queensland; Figure 2b). In 2010, none of the trigger points were exceeded3,5.
The Barramundi catch in the Kimberley Gillnet and Barramundi Fishery (Western Australia) is small compared with other Australian fisheries and has varied from 27 t to 60 t over the past 10 years. CPUE has followed the same pattern as catch. Exceptions were in 2006, when low catches were associated with high CPUE (42.2 kg/km gillnet/hour), and in 2010, when high catches were associated with low CPUE (27.7 kg/km gillnet/hour). CPUE declined substantially from 38.8 kg/km gillnet/hour in 2009 to the 2010 level7.
- Commercial gillnets have almost no impact on coastal habitat and are quite selective, with bycatch making up only a small proportion of the catch. However, commercial gillnets do interact with threatened, endangered and protected (TEP) species. Although reported interactions are low, the impact on the populations of TEP species is unknown2–3,5,7.
- The duration and magnitude of the wet season strongly drives biomass of Barramundi stocks, with large wet seasons resulting in higher recruitment than smaller wet seasons6,11.
a Department of Primary Industry and Fisheries, Northern Territory
b Department of Fisheries, Western Australia
c Department of Agriculture, Fisheries and Forestry, Queensland