Gascoyne biological stock
The Gascoyne biological stock is exploited as a component of the Gascoyne Demersal Scalefish Managed Fishery (Western Australia)1. The catch of Red Emperor in the Gascoyne Bioregion is very low (Table 3). In the Gascoyne Bioregion Red Emperor is assessed on the basis of the status of several indicator species (Snapper—Chrysophrys auratus, Goldband Snapper—Pristipomoides multidens, and Spangled Emperor— Lethrinus nebulosus) that represent the entire inshore demersal suite of species occurring at depths of 30–250 m. These species were selected using a risk-based approach, based on the relative vulnerability of the species to exploitation.
The major performance measures for these indicator species are either estimates of current spawning stock levels or fishing mortality–based assessments. The target level of spawning biomass is 40 per cent of the unfished level, and the limit level is 30 per cent of the unfished level. Data analysis using an integrated age-structured model estimated that the spawning biomass levels of Snapper were close to 40 per cent of the unfished level in the Gascoyne Demersal Scalefish Managed Fishery (Western Australia) in 20111. The Gascoyne biological stock is not considered to be recruitment overfished.
The indicator species Goldband Snapper and Spangled Emperor in the Gascoyne Bioregion were assessed using fishing mortality (F)–based assessments 1 (derived from catch-curve analysis of representative samples of the age structure). These assessments use reference levels that are based on ratios of natural mortality (M) for each species, such that Ftarget = 2/3M, Fthreshold = M and Flimit = 3/2 M. These assessments indicated that the fishing levels of Goldband Snapper were at or below the target level. Whereas, Spangled Emperor were below the target level in one area, and above the limit level in another area, suggesting spatial confinement of growth overfishing. On balance, the assessments indicate that indicator species are not recruitment overfished. Therefore, given catches of Red Emperor are low, 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.
Pilbara biological stock
The major performance measures for the Pilbara biological stock, for Red Emperor landed in the Pilbara Trap Managed Fishery and the Pilbara Fish Trawl Interim Managed Fishery, are based on estimates of current spawning stock levels of Red Emperor. The target level of spawning biomass is 40 per cent of the unfished (1972) biomass. The limit level is 30 per cent of the unfished spawning biomass. The spawning biomass level of Red Emperor overall (across all management areas of the Pilbara biological stock) was greater than 40 per cent in the Pilbara Demersal Scalefish Fisheries in 2007 (the year the last integrated assessment was undertaken), using an integrated age-structured model4. The stock is therefore not considered to be recruitment overfished.
An assessment of fishing mortality derived from representative samples of the age structure of Red Emperor was also undertaken for separate management areas in the Pilbara biological stock in 2007. These fishing mortality (F)–based assessments use the reference levels defined above for the Gascoyne biological stock. The assessments indicated that the fishing level on Red Emperor in 2007 was between the target and threshold levels, but above the limit level in some areas4. This indicates that fishing was having an impact on the age structure of the population in some management areas. Effort reductions since 2008 have resulted in decreasing catch levels. In 2007, the Red Emperor catch from the Pilbara biological stock was 187 tonnes (t). The catch decreased to 154 t in 2008, and remained at a similar level in 2009 (159 t) and 2010 (167 t). From 2008 to 2010, the catch-rate trends for Red Emperor in all trawl managed areas increased each year. This was considered to be a response to the effort reductions imposed on the trawl fishery since 2008. From 2010 to 2013, the catch-rate trends of Red Emperor have been stable in all trawl managed areas, except Area 2, where there has been a slight decline. The above evidence indicates that the current level of fishing mortality is unlikely to cause the stock to become recruitment overfished.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
Kimberley biological stock
The major performance measures for the Kimberley biological stock of Red Emperor relate to spawning stock levels. The target level of spawning biomass is 40 per cent of the unfished (1980) level. The limit level is 30 per cent of the unfished level. The spawning biomass level of Red Emperor was greater than 40 per cent in the Northern Demersal Scalefish Managed Fishery in 2007 (the year the last integrated assessment was undertaken), as derived by synthesising the available data in an integrated age-structured model4. Catch levels of Red Emperor in the Northern Demersal Scalefish Managed Fishery over the past 5 years (2009 to 2013) have been stable, ranging between 128 and 156 t, and are below the catch levels for the preceding 5‑year period (2004 to 2008) of sustainable fishing, when catches ranged between 164 and 192 t4. The stock is not considered to be recruitment overfished.
An assessment of fishing mortality derived from representative samples of the age structure of Red Emperor was also undertaken for the Northern Demersal Scalefish Managed Fishery in 2006 and 2008. These fishing mortality (F)–based assessments use the reference levels defined above for the Gascoyne biological stock. The assessments indicated that the fishing level on Red Emperor was lower than the target level in 2006 and 20084. This indicates that fishing is not having an unacceptable impact on the age structure of the population. The above evidence indicates that the current level of fishing mortality is unlikely to cause the stock to become recruitment overfished.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
Northern Territory
Red Emperor comprises around 2 per cent of the total catch in the Northern Territory offshore snapper fisheries. It is managed as part of the ‘group species’ quota category (species other than Goldband Snapper, Saddletail Snapper and Crimson Snapper) in the Timor Reef Fishery and the Demersal Fishery. The performance indicators and trigger points are based on significant changes in species composition of the catch, which are used to indicate whether significant catch increases warrant further management efforts. Since 1995, catches of Red Emperor have varied between 1.5 and 4.5 per cent of the total annual catch, and increased from 20 t in 1995 to 55 t in 2013. The trigger point of an increase of more than 15 per cent of the species’ previous year’s catch weight, or of a species becoming dominant relative to other species in the group, was not reached in 2013.
This evidence suggests that the current level of fishing mortality is unlikely to cause Red Emperor in the Northern Territory to become recruitment overfished. However, at present, insufficient information is available to determine the biomass of the species in the Northern Territory.
On the basis of the evidence provided above, Red Emperor in the Northern Territory is classified as an undefined stock.
Gulf of Carpentaria management unit
Red Emperor has historically been taken by demersal fish trawl (Gulf of Carpentaria Developmental Fin Fish Trawl Fishery [Queensland]) and by line (Gulf of Carpentaria Line Fishery [Queensland]). Participants in the Gulf of Carpentaria Line Fishery primarily target Spanish Mackerel ( Scomberomorus commerson) by trolling. Since 2010, catch of Red Emperor in this fishery has fallen to very low levels, primarily as a result of decline in fishing effort in the area. Harvest from the adjacent Northern Territory component of the stock has been low in recent years.
Commercial catches in the Gulf of Carpentaria Developmental Fin Fish Trawl Fishery have been historically variable. Fish trawl effort in the Gulf of Carpentaria declined markedly in 2012 and further in 2013, as a result of transfer of effort to Northern Territory regions outside the Gulf. There are limited data on the distribution and abundance of Red Emperor in the Gulf of Carpentaria5,6. Nominal commercial catch rates have been historically variable, although long-term standardised catch rates to 2009 showed significant declines7. Observer surveys from 2004 to 2006 showed that most Red Emperor caught in the Gulf of Carpentaria Developmental Fin Fish Trawl Fishery was discarded, the majority of which were immature (unpublished data).
Insufficient information is available to confidently classify the status of this stock.
On the basis of the evidence provided above, the management unit is classified as an undefined stock.
East coast Queensland management unit
There has been no stock assessment to determine biomass in the east coast Queensland management unit.
Red Emperor is mainly harvested by the recreational sector. Recreational catch estimates have fallen from approximately 200 t in 2000 to 150 t in 2010, despite the latest survey showing that recreational anglers are targeting Red Emperor more often. A harvest reduction of this magnitude was also reflected in charter catch over the same period (charter fishing is a subset of recreational fishing), mainly over the past 5 years.
Annual commercial catches have been 25–60 t since 2004–05, following several years of much higher catches (100–200 t per year) from 1997–98 to 2004–05. This decrease coincided with expansion of no-take marine reserves within the Great Barrier Reef Marine Park and the introduction of a quota management system for coral reef finfish species. Both factors are likely to have influenced commercial catch.
Commercial harvest is not effectively constrained by this species being part of the ‘other species’ quota category, which comprises many other coral reef finfish species, with no individual cap on any one species in this category.
Insufficient information is available to confidently classify the status of the stock.
On the basis of the evidence provided above, the management unit is classified as an undefined stock.
Figure 2: Commercial catch of Red Emperor in Australian waters, 1999 to 2013 (calendar years)
Note: Western Australian data are combined because of confidentiality issues for one or more stocks in one or more years.