Assessments of Coral Trout take into account a species complex in the Commonwealth and Queensland jurisdictions. This complex comprises Common Coral Trout (Plectropomus leopardus), Barcheek Coral Trout (P. maculatus), Bluespotted Coral Trout (P. laevis), Passionfruit Coral Trout (P. areolatus), Yellow-edge Coronation Trout (Variola louti) and White-edge Coronation Trout (V. albimarginata). The biological stock structure of Coral Trout is spatially complex and remains uncertain; hence, status is reported at the management unit level rather than individual biological stocks.
Torres Strait Finfish Fishery (Commonwealth) management unit
No formal stock assessment has been conducted in the Torres Strait Finfish Fishery (Commonwealth), but a management strategy evaluation1 tested four model simulations. All models estimated that biomass in 2004 was greater than 60 per cent of the unfished level (in 1965), and it was estimated that biomass would be greater than 70 per cent of the unfished level by 2025 at 2007 fishing levels. The management unit is not considered to be recruitment overfished.
Catch in recent years has been below historical catch levels and well below the lowest catch level simulated in the management strategy evaluation (80 tonnes [t] per year). A catch simulation at 80 t suggested that Coral Trout biomass in the fishery would increase to greater than 80 per cent of the unfished biomass within 20 years1. The current level of fishing mortality is unlikely to cause the management unit to become recruitment overfished.
On the basis of the evidence provided above, the Torres Strait Finfish Fishery (Commonwealth) management unit is classified as a sustainable stock.
Fishing Tour Operators (Northern Territory) management unit
The status of Coral Trout is unknown in the Northern Territory. Only small catches are reported from the Fishing Tour Operator sector, and no catch is reported from the commercial sector2.
Insufficient information is available to confidently determine status; as a result, the Fishing Tour Operators (Northern Territory) management unit is classified as an undefined stock.
Coral Reef Fin Fish Fishery (Queensland) management unit
The spatially complex nature of Coral Trout means that it has not been possible to conduct a traditional stock assessment on the east coast of Queensland. However, other assessments, such as the Effects of Line Fishing project3, have enabled simulation of Coral Trout populations based on varying management arrangements.
Approximately 33 per cent of the Great Barrier Reef Marine Park is closed to fishing, protecting fish in these areas from fishing. As well, from 2006 to 2010, Fisheries Queensland conducted annual fishery-independent line surveys to monitor catch rates and gather information on biological stock structure. Data collected during this time have contributed to the development of standardised catch-rate performance measures for the fishery. The annual standardised catch rate in 2009–10 did not fall below 90 per cent of the average standardised catch rate for all preceding quota years4. Data in 2009–10 indicated a good recruitment of 2-year-old fish to the fishery. These results indicate that the biomass in 2010 was at a level not considered to be recruitment overfished.
The performance measure relating to total mortality (total mortality [Z] exceeding two times the estimate of natural mortality [M]) calculated from age composition was not triggered in 2009–10 (2M = 0.90 and Z = 0.59 ± 0.06), and only 80 per cent of the available quota (1350 t) was taken4.
This indicates that the level of fishing mortality is unlikely to cause the management unit to become recruitment overfished.
On the basis of the evidence provided above, the Coral Reef Fin Fish Fishery (Queensland) management unit is classified as a sustainable stock.
Figure 2: Commercial catch of Coral Trout in Australian waters, 2000–10 (calendar year)
Note: Queensland catch estimates are based on financial years (i.e. 2010 refers to 2009–10 data).
Catch of Coral Trout in the Coral Reef Fin Fish Fishery (Queensland) decreased following the introduction of quota (1350 t annually) in the 2004–05 fishing season. Since then, almost all this quota has been used each year. However, in the 2009–10 fishing season, only 80 per cent was used. Cyclonic conditions during the season are believed to be responsible for damage to fishing grounds and subsequent reductions in fishing effort. Commercial fishers also reported reduced catch rates in the affected areas. Coral Trout catch in the Torres Strait Finfish Fishery (Commonwealth) increased to 36 t in 2010, compared with the previous year's catch of 27 t. However, this is still well below the historical high of 174 t in 2004. Factors that have caused this reduction include fewer active fishers and increased costs of fishing12. In the Northern Territory, Fishing Tour Operator catch has been steady over the past 10 years at around 30–40 t. However, in 2010 the catch decreased to approximately 16 t. The reasons for this are unknown.
- The 2009 Coral Reef Fin Fish Fishery (Queensland) annual status report noted that effort shifted away from areas affected by Tropical Cyclone Hamish in March 20094. Tobin et al.13 reported on the effects of three tropical cyclones on the Coral Reef Fin Fish Fishery industry, including a decrease in Coral Trout catch rates of around one-third in regions with the most structural reef damage. The destruction, scouring and displacement of reef habitat were significant and widespread across large areas of the reef. In addition to the structural reef damage, commercial fishers reported reduced catch rates of all species throughout the directly impacted areas13. The analysis identifies depressed catch rates in affected areas following cyclones for a duration of 12–24 months.
- Climate change impacts are a concern for coral reef ecosystems. Climate change has been linked to increases in the number and extent of coral bleaching events14 and changes in ocean chemistry. These events also have the potential to impact on the replenishment rates of coral reef fin fish populations15, individual growth rates and spawning output16, and may influence the geographic distribution of coral reef species (e.g. latitudinal shifts in distribution).
a Department of Agriculture, Fisheries and Forestry, Queensland
b Australian Bureau of Agricultural and Resource Economics and Sciences
c Department of Primary Industry and Fisheries, Northern Territory
d There have been declines in catch and catch rates in 2011, which need to be monitored in coming years to ensure sustainability.