Stock assessment of Australian east coast Spanish mackerel (Scomberomorus commerson)

Abstract

Spanish mackerel, Scomberomorus commerson, are large offshore pelagic fish. On the east coast of Australia, Spanish mackerel form a single genetic stock between Cape York Peninsula in north Queensland and Newcastle on the New South Wales mid-coast.

This stock assessment used an annual time-step, two-sex, age-structured population model. The model incorporated data from 1911 to 2020, including estimated commercial, charter and recreational harvest for Queensland and New South Wales, Queensland commercial standardised catch rates, fish age-length frequencies, and key long-term fishery information on fishing power changes and catch rates. Eight model scenarios were run, covering a range of modelling assumptions and fixed parameters. The stock assessment estimates the spawning biomass of east coast Spanish mackerel in 2020 was between 14 and 27% of unfished levels in 1911. The base case model estimate was most likely at 17% of unfished biomass in 2019–2020. This report provides estimates of sustainable harvests for all sectors—commercial, charter and recreational across Queensland and New South Wales—and supports the harvest strategy defined in the Queensland’s Sustainable Fisheries Strategy 2017–2027 (Department of Agriculture and Fisheries 2017).