Table 1: Stock status determination for Spanish Mackerel
Jurisdiction |
Commonwealth |
Northern
Territory |
Queensland |
Western
Australia |
Stock |
TSSMF |
Northern Territory
(FTF, ONLF, SMF) |
ECSMF |
Gulf of Carpentaria (GOCIFFF, GOCLF) |
MMF |
Stock status |
|
|
|
|
|
Sustainable |
Sustainable |
Sustainable |
Undefined |
Sustainable |
Indicators |
Biomass, fishing mortality, catch |
Catch rate, egg production |
Biomass, fishing mortality, catch, catch rate |
Catch, catch rate |
Catch, population dynamics, catch rate |
ECSMF = East Coast Spanish Mackerel Fishery (Queensland); FTF = Finfish Trawl Fishery (Northern Territory); GOCIFFF = Gulf of Carpentaria Inshore Fin Fish Fishery (Queensland); GOCLF = Gulf of Carpentaria Line Fishery (Queensland); MMF = Mackerel Managed Fishery (Western Australia); ONLF = Offshore Net and Line Fishery (Northern Territory); SMF = Spanish Mackerel Fishery (Northern Territory); TSSMF = Torres Strait Spanish Mackerel Fishery (Commonwealth)
Genetic evidence has indicated that there are three biological stocks of Spanish Mackerel across northern Australia;1 however, evidence from otolith microchemistry and parasite analysis, and the limited adult movement of the species (at scales greater than 100 km) indicate that there are likely to be a number of smaller biological stocks with limited interaction1. Each jurisdiction is likely to have multiple biological stocks within its boundaries, but it would be difficult to obtain relevant biological and catch-and-effort information to assess each one individually. Hence, rather than assessing the status of individual biological stocks, status is reported at the level of management units for the Torres Strait, Queensland east coast and Gulf of Carpentaria, and at the jurisdictional level for the Northern Territory and Western Australia. The status determination of these assessment units is based on the areas that receive the highest harvest rates; status can therefore be assumed to represent the highest level of exploitation that occurs within each management unit and jurisdiction.
Torres Strait Spanish Mackerel Fishery (Commonwealth) management unit
The most recent assessment2 uses a sex-specific age-structured population dynamics model to estimate biomass. The assessment provides an indication of the current level of exploitation and sustainability of the Torres Strait Spanish Mackerel Fishery (Commonwealth). The base-case model within the assessment estimates that biomass in 2006 was 37 per cent (range 26–67 per cent) of the unfished level. Based on this, the management unit was not considered to be recruitment overfished in 2006.
Additionally, catches from 2007 to 2010 have been below both the base-case and the lower risk estimates of maximum sustainable yield in the stock assessment2. This 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 Spanish Mackerel Fishery (Commonwealth) management unit is classified as a sustainable stock.
Northern Territory
Spanish Mackerel stocks have been assessed at a jurisdictional level for the Northern Territory, including information up to 2010. The results indicated that the Spanish Mackerel stocks in the Northern Territory declined substantially as a result of high Taiwanese catches in the 1970s and 1980s, but have since recovered, with the cessation of foreign fishing and more stringent management of the domestic fishery. In 2010, egg production was estimated at around 85 per cent of unfished levels, which is well within sustainability limits for a species such as Spanish Mackerel3– 4. Supporting this assessment is that catch per unit effort (CPUE) has increased substantially over the past 10 years, with the 2010 value being the highest recorded in the fishery5. Spanish Mackerel in the Northern Territory is not considered to be recruitment overfished, and the current level of fishing mortality is unlikely to cause the species to become recruitment overfished.
On the basis of the evidence provided above, Spanish Mackerel in the Northern Territory is classified as a sustainable stock.
East Coast Spanish Mackerel Fishery (Queensland) management unit
A recent stock assessment using data up to 2009 indicated that the stocks on the east coast are in good condition6. Estimates of egg production ranged from 37 to 51 per cent of unfished levels (biomass level in 1937), which are well within sustainability limits for a species such as Spanish Mackerel4. The management unit is not considered to be recruitment overfished.
Strong recruitment of 1-year-old fish in 2008–09 was still evident in 2009–10 (as 2-year-olds)7. The commercial catch in 2010 was 384 tonnes (t), which is less than the quota (544 t) for this management unit. In addition, the estimate of total mortality in 2009–10 was less than twice natural mortality. This level of fishing mortality is unlikely to cause this management unit to become recruitment overfished.
On the basis of the evidence provided above, the East Coast Spanish Mackerel Fishery (Queensland) management unit is classified as a sustainable stock.
Gulf of Carpentaria management unit
The status of this management unit has only been partially assessed because of a lack of data demonstrating temporal trends in length or age frequencies. Commercial catch and catch rates of Spanish Mackerel increased slightly in 2010 and remain within historical harvest levels. However, until biological data have been analysed and further consideration is given to the utility of catch rates as an index of abundance, it is unknown whether current catch levels are causing this management unit to become recruitment overfished.
On the basis of the evidence provided above, Spanish Mackerel in the Queensland Gulf of Carpentaria management unit is classified as an undefined stock.
Western Australia
A stock assessment model8 confirmed that the minimum legal size of 90 cm total length is similar to the size-at-maturity for this species. Catch-and-effort data, biological information, biomass and yield-per-recruit modelling were used in the assessment. The assessment showed this stock to be a sustainable stock. Spanish Mackerel are fast growing and have a young age (<2 years) at sexual maturity9, indicating some resilience to fishing pressure. The model determined a sustainable catch range of 246–410 t, and the 2010 catch of 284 t was well within this range10. Spanish Mackerel in Western Australia is not considered to be recruitment overfished, and the level of fishing mortality is unlikely to cause the species to become recruitment overfished.
On the basis of the evidence provided above, Spanish Mackerel in Western Australia is classified as a sustainable stock.
Table 2: Spanish Mackerel biology1–2,9,11–12
Longevity and maximum size |
22 years; 240 cm FL |
Maturity (50%) |
~2 years; 80 cm FL |
FL = fork length
Figure 1: Distribution of reported commercial catch of Spanish Mackerel in Australian waters, 2010
- Commercial catch of Spanish Mackerel is predominantly taken using trolled baits and lures, rod and reel, handlines and droplines. It is also taken in net and fish trawl fisheries in northern Australia.
- A range of input and output controls have been implemented to manage Spanish Mackerel stocks:
- Input controls include limited entry, vessel restrictions and area closures.
- Output controls include total allowable catches, and recreational bag limits and size limits.
- In 2010, commercial catch of Spanish Mackerel was reported from 35 vessels in the Torres Strait Spanish Mackerel Fishery (Commonwealth) (comprising Transferable Vessel Holder [non-Indigenous] and Traditional Inhabitant Boat sectors), 12 vessels in the Northern Territory, 14 vessels in Western Australia, 167 vessels in the East Coast Spanish Mackerel Fishery (Queensland) and 43 vessels in the Gulf of Carpentaria.
- In 2010, the total amount of Spanish Mackerel caught commercially in Australia was 961 t, comprising 88 t in the Torres Strait Spanish Mackerel Fishery (Commonwealth), 385 t in the East Coast Spanish Mackerel Fishery (Queensland), 231 t in the Gulf of Carpentaria Line Fishery (Queensland), 51 t in the Gulf of Carpentaria Inshore Fin Fish Fishery (Queensland), 254 t in the Northern Territory and 284 t in Western Australia.
- Recreational catch of Spanish Mackerel is substantial. Estimates include 415 t in Queensland for 200513 and the equivalent of 21–45 per cent of the commercial catch in Western Australia10. More recent survey results for recreational catch of Spanish Mackerel in Queensland, the Northern Territory and Western Australia are expected to be released later in 2012. Indigenous catch of Spanish Mackerel is unknown.
Figure 2: Commercial catch of Spanish Mackerel in Australian waters, 2000–10 (calendar year)
Note: Queensland catch is for the financial year, with data for 2009–10 plotted against 2010.
For the Torres Strait Spanish Mackerel Fishery (Commonwealth), total commercial catch decreased from 101 t in 2009 to 88 t in 2010. This follows a general pattern of decline in catch since 2006–07. These decreased catches are likely to be due to effort decreases as a result of increasing fuel and infrastructure costs, fewer fishers targeting Spanish Mackerel and a lack of availability of skilled crews. The Traditional Inhabitant Boat sector catch from this fishery rose from 2 t to 10 t, but it is unclear whether this is due to increased catch or increased reporting, given that reporting of catch in this sector is voluntary.
The Spanish Mackerel Fishery (Northern Territory) caught 254 t commercially, which was 48 per cent less than the peak catch of 409 t in 2006. Similar factors that led to the reduction of catch in the Torres Strait are likely to have caused the decline in the Spanish Mackerel Fishery (Northern Territory), as CPUE has increased substantially during this time5. Commercial catch from the Gulf of Carpentaria increased from 251 t in 2009 to 282 t in 2010. However, this was approximately 89 t less than the peak catch in 2008. Total catch for Western Australia in 2010 was 284 t, less than the 2009 catch of 323 t.
In 2004, new management arrangements, including a quota system, were introduced for Spanish Mackerel in the East Coast Spanish Mackerel Fishery (Queensland). Subsequently, in 2005, catches were reduced to around half of the previous commercial catch. In 2010, the catch increased to 385 t from 309 t in 2009, due to a strong recruitment of 2-year-olds to the fishery in 2009–10.
- All Spanish Mackerel in Western Australia and most in other jurisdictions are targeted using trolled lines, which have almost no impact on the habitats where they are used, and result in little bycatch, relative to the target species.
- Commercial gillnets interact with threatened, endangered and protected species. Although reported interactions are low, the impact on the populations of these species is unknown.
- An analysis of community structure of finfish in the bioregions in Western Australia14 where mackerel fishing has been undertaken has found no evidence of any significant shift over the past 30 years15.
- Warm coastal waters associated with El Niño events are believed to lead to increased primary production, with improvements in larval survival and recruitment (Tobin, unpublished report).
- Marine heatwave events in late 2010 – early 2011 in Western Australia appear to have temporarily shifted distribution of Spanish Mackerel southward16. It is currently unclear if this is a one-off event or a longer term shift in the system (i.e. regime shift).
a Department of Agriculture, Fisheries and Forestry, Queensland
b Department of Primary Industry and Fisheries, Northern Territory
c Australian Bureau of Agricultural and Resource Economics and Sciences
d Department of Fisheries, Western Australia