Table 1: Stock status determination for Sea Mullet
Jurisdiction |
New South Wales, Queensland |
Western Australia |
Stock |
Eastern Australian
(ECIFFF, EGF, OHF) |
Western Australian
(SBBSMNMF, SCEMF, WCEMF) |
Stock status
Indicators |
|
|
Sustainable |
Sustainable |
Catch, CPUE, length and age frequencies |
Catch, CPUE |
CPUE = catch per unit effort; ECIFFF = East Coast Inshore Fin Fish Fishery (Queensland); EGF = Estuary General Fishery (New South Wales); OHF = Ocean Hauling Fishery (New South Wales); SBBSMNMF = Shark Bay Beach Seine and Mesh Net Managed Fishery (Western Australia); SCEMF = South Coast Estuarine Managed Fishery (Western Australia); WCEMF = West Coast Estuarine Managed Fishery (Western Australia)
Results of extensive tagging studies1 suggest a single east coast biological stock of Sea Mullet, extending from central Queensland to eastern Victoria. The biological stock structure of Sea Mullet off Western Australia is likely to be complex, although limited tagging and genetic studies2–3 suggest mixing of fish throughout the lower west coast region, where the majority of the catch is taken. Therefore, a single Western Australian biological stock is assumed here. Status for Sea Mullet is reported at the level of individual biological stocks.
Eastern Australian biological stock
The eastern Australian biological stock has a long history of relatively stable commercial landings and catch rates for estuary and ocean fisheries in both New South Wales and Queensland4–5. Length and age composition of catches is regularly monitored, and results suggest consistent recruitment and age composition during recent years4–5. Sea Mullet are relatively fast-growing fish, with the majority of landings comprising fish between 2 and 5 years of age. This evidence indicates that the biomass of this biological stock is unlikely to be recruitment overfished. Recent commercial landings have been close to the long-term average catch, since the 1940s, of 4957 tonnes (t)4–5. This evidence indicates that 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.
Western Australian biological stock
Sea Mullet occurs in all coastal regions of Western Australia, but commercial targeting of the species is mainly restricted to waters from Shark Bay southwards. Sea Mullet is managed separately in the four Western Australian bioregions, although the level of connectivity between the different populations is unknown6. The level of fishery assessment for Sea Mullet is determined by a risk assessment, based on trends in commercial catches and catch rates. Catch rates were relatively stable over the period 1980–2000, and have increased slightly since 20006. The available evidence indicates that this biological stock is unlikely to be recruitment overfished.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
Table 2: Sea Mullet biology7–8
Longevity and maximum size |
Eastern Australia: 10 years; 60 cm FL
Western Australia: males 8 years; females 12 years |
Maturity (50%) |
Eastern Australia: males 33 cm FL; females 37 cm FL Western Australia: both sexes 37 cm TL |
Figure 1: Distribution of reported commercial catch of Sea Mullet in Australian waters, 2010
- Fishing is primarily undertaken using mesh (gill) nets in estuarine waters and hauling (seine) nets on ocean beaches. Small quantities of recreational catch are taken by rod and line9–10.
- A range of input and output management controls are applied to the Sea Mullet biological stocks:
- Input controls include limited entry to the fisheries, gear restrictions, seasonal closures and area
- Output controls include size limits and recreational bag limits.
- In 2010, a total of 414 fishers reported catching Sea Mullet in New South Wales. In Queensland, 283 fishers reported landing ‘unspecified mullet’ (all species combined, but it is likely that Sea Mullet comprised the majority of the catch). A total of 65 commercial fishers reported catching Sea Mullet in Western Australia.
- The total commercial catch of Sea Mullet in Australia in 2010 was approximately 5604 t, comprising 3739 t in New South Wales, 1599 t in Queensland and 263 t in Western Australia. A small catch (3 t) was reported in Victoria. Recreational anglers also capture Sea Mullet in minor quantities throughout its range.
a)
b)
Figure 2: a) Commercial catch of Sea Mullet in Australian waters, 2000–10 (calendar year);
b) nominal catch rate of Sea Mullet, 1998–2009.
Note: New South Wales catch is for the financial year ending in the year shown; e.g. 2009–10 data are plotted against 2010.
A long history of stable commercial catches and catch rates is evident for both the estuarine and the ocean beach sectors of the commercial fisheries in New South Wales, giving no cause for concern about the current status of the biological stock5,8. The average annual commercial catch for the eastern biological stocks since 1988 is around 5980 t, with a range of around 3700 t to 7500 t. Very bad weather during the main beach fishing season of 2009 resulted in reduced landings for that year (1783 t), but landings recovered to previous levels during 2010 (NSW DPI, unpublished data). Sea Mullet comprise the largest catch, by weight, of species harvested by commercial net fisheries in Queensland. Catches and catch rates have been stable for many years.
In Western Australia, landings of Sea Mullet have recently been lower than historical levels, due to lower levels of targeted commercial fishing effort6. Sea Mullet is taken by ‘multispecies’ net fisheries, and the quantity caught can be influenced by the availability of higher value species and market demand, as well as Sea Mullet abundance. Annual catch declined from 500–700 t in the 1970s and 1980s to around 200–300 t in recent years, as a result of reduced fishing effort.
- No effects have been identified.
- Sea Mullet penetrate far up rivers, often into fresh water, and barriers to fish passage (such as weirs and dams) can reduce the amount of habitat available to the species.
- Being highly dependent on riverine and estuarine habitats, Sea Mullet populations are vulnerable to fluctuations in water quality—eutrophication and hypoxia can cause significant fish kills.
a Department of Primary Industries, New South Wales
b Department of Agriculture, Fisheries and Forestry, Queensland
c Department of Fisheries, Western Australia