Greenback horse mackerel

No DEPM survey or estimate of spawning biomass has been conducted for jack mackerel (west) (Ward and Grammer 2016).

There is a paucity of information on life history and productivity for jack mackerel (west). Data from jack mackerel (east) were used instead, which may compromise the model outputs for the stock (Ward and Grammer 2016).

Last updated on 24 Oct 2016

These models suggest that the current harvest strategy is appropriate, and its application would result in a low probability of the stock falling below 0.2B0 for more than 90 per cent of the time, in line with the HSP (Ward and Grammer 2016).

The peak total catch in 2006–07 was less than 1 per cent of the 1970s biomass estimate and 7 per cent of the RBC. There was no reported catch for 2014–15. Catch in 2015–16 increased to 631 t, which is 17 per cent of the RBC and TAC (Moore et al. 2010; Moore and Mazur 2016).

Catches in recent years have been low; the current catch is close to zero. The above evidence indicates that the stock is unlikely to be recruitment overfished and that the current level of fishing pressure 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 (Ward and Grammer 2016).

The peak harvest from this fishery was less than 1 per cent of the spawning biomass estimate, and catches have been low as a proportion of estimated biomass. Although this biomass estimate is quite dated, this level of fishing mortality is unlikely to have substantially reduced spawning biomass. As a result, jack mackerel (west) is classified as not overfished for both years assessed. Current fishing mortality remains a small proportion of biomass, and below the 2014–15 and 2015–16 RBCs. The stock is therefore classified as not subject to overfishing for both years assessed (Ward and Grammer 2016).

Last updated on 24 Oct 2016

No daily egg production method survey or estimate of spawning biomass has been conducted for the western Common Jack Mackerel stock. Aerial surveys in the 1970s suggested a biomass off western Tasmania of at least 80 000 t. Catches peaked in 2006–07, when they were less than 1 per cent of the biomass estimate and 9 per cent of the current TAC (5000 t) for the Small Pelagic Fishery (Commonwealth) (Moore et al. 2010; Moore and Mazur 2016). 

Total catch (state and Commonwealth) for jack mackerel (west) did not exceed 250 t before 2005–06. Commonwealth catch was zero or negligible from 2011–12 to 2014–15, and increased to 631 t in 2015–16. State catches have been negligible for the past decade (Moore et al. 2010; Moore and Mazur 2016).

Studies in the Northern Hemisphere have shown that, although interactions with dolphins (Bottlenose and Common dolphins occur in Australia) can be common, these species are rarely caught by purse seine and, when caught, usually survive. Mortalities of both seals and dolphins have been recorded during midwater trawl operations in this fishery. Dolphin encounters appear to be very rare; however, underwater cameras have revealed that seals commonly enter and forage in midwater trawl gear, with some mortalities. Seal excluder devices in the trawl nets have had some success in reducing, but not eliminating, lethal interactions (Pikitch et al. 2012).

Common Jack Mackerel play a role in the pelagic food chain as a link between primary and secondary producers and top predators, including tunas, sharks, marine mammals and seabirds. Recognising this important ecological role, the harvest strategy adopted in the Small Pelagic Fishery (Commonwealth) restricts catches to conservative levels of below 20 per cent of current spawning biomass estimates. These are consistent with levels internationally recommended for the sustainable management of forage fisheries (Pikitch et al. 2012).

Of the three main fishing methods used to target Common Jack Mackerel (purse seine, midwater trawl and beach seine), only beach seine interacts with the benthos. Studies in New South Wales have shown that purse-seine nets have a negligible impact on seagrass habitats. Both purse-seine and midwater trawl fisheries interact with marine mammals, including seals and dolphins. Purse-seine nets remain open to the surface (Pikitch et al. 2012).