Grey mackerel monitoring east coast stock monitoring

Biology

Grey mackerel (Scomberomorus semifasciatus) are a pelagic fish found in tropical and sub-tropical inshore areas. Their distribution ranges from Shark Bay in Western Australia, across northern Australia, and down the east coast of Queensland to northern New South Wales.

On the east coast of Queensland, the best available research indicates there is a northern stock and a southern stock.  The exact boundary between the two stocks is unknown, but the separation could occur somewhere between Townsville and Mackay (Figure 1). Further research, such as sampling at a finer spatial resolution, would be beneficial in establishing the distribution of the two stocks.

Grey mackerel reach maturity at two years of age and can live to 12 years of age, reaching 120cm in length. They are found around headlands and in rocky reef habitats where they feed mainly on pelagic baitfish.

Grey mackerel can be confused with other mackerels –the identification features of grey mackerel and other commonly caught Queensland mackerel species are listed below.

The fishery

In Queensland, grey mackerel is an important commercial species. Together with Spanish, spotted and school mackerel, they are a source of fresh fish for seafood markets. Fisheries Queensland monitors the commercial catch of grey mackerel through commercial fishing logbooks.

On the east coast, more than 90% of grey mackerel are landed by net as part of the east coast inshore fin fish fishery . The remainder is landed by line as part of the pelagic line fishery (Figure 2). The harvest of grey mackerel in these fisheries peaked in 2008 at 390t. In 2009, a total allowable catch of 250t was introduced for the commercial fishery.

The recreational catch of grey mackerel is relatively low compared to commercial catch.

Biological monitoring

Fisheries Queensland monitors biological information for grey mackerel on Queensland’s east coast to assess the sustainability of these stocks.

Routine biological monitoring of grey mackerel on the east coast of Queensland occurred from 2008 until 2016, and recommenced in January 2020. This sampling program predominantly collects data on length, sex and age of fish caught by commercial fishers in the east coast inshore fin fish fishery.

Recreational fisher length and catch information is obtained through the statewide recreational boat ramp survey program and total catch and effort is estimated through the statewide recreational fishing survey .

Monitoring focuses on specific regions during certain times of the year where most grey mackerel catches occur. The main regions include Cairns, Townsville, Bowen, Mackay, Rockhampton and Hervey Bay which are most heavily sampled between May and October. Monitoring relies on the voluntary participation of the fishing industry to allow access to their catches for data collection. Confidential information is not shared.

Stock status

Fisheries Queensland combines biological monitoring information with commercial catch records and estimates of recreational harvest in a weight-of-evidence assessment every two years using the Status of Australian Fish Stocks framework . The most recent assessment for grey mackerel was completed in 2018 with both the north east and south east Queensland stocks assessed as sustainable.

Stock assessment

Stock assessments use statistical and mathematical methods to estimate the status and size of fished populations and predict how they are likely to respond to alternative management choices. It is important to consider the sources of uncertainty within a stock assessment model when interpreting the results. Read the latest stock assessment for grey mackerel  .

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