Download FAR 2026/07 Species proportions and ages of jack mackerels (Trachurus spp.) from JMA 7 catches during the 2023–24 fishing year

Jack mackerels (JMA) support significant commercial fisheries in New Zealand, with over 75% of the total jack mackerel catch taken by trawl fisheries off the west coasts of the North Island and South Island, in the JMA 7 Quota Management Area. Three jack mackerel species are caught in New Zealand waters, namely Trachurus declivis, T. murphyi, and T. novaezelandiae. However, T. murphyi are now caught in relatively low numbers and mainly in JMA 3 and due to the low catches are not aged in the current project (MID2024-01).

New Zealand commercial catches of jack mackerels have been recorded against the generic species code JMA. Therefore, species-specific catch information is not available from the fishery data. Estimates of proportions of the T. declivis and T. novaezelandiae in the catch, based on species code specific observer data are used to derive species-specific catch estimates from the JMA catch data.

This report updates the data collected by the New Zealand observer sampling programme from trawl landings of jack mackerels in JMA 7 with the data collected during the 2023–24 fishing year, including estimates of species proportions and sex ratios in the landings, corroboration of observer species identification via otolith shape analysis, catch-at-length (fork length, cm), and catch-at-age for both species.

Estimated proportions of catch by species based on observer data have historically shown that T. declivis comprises 61–80% of the catch for all statistical areas, and T. novaezelandiae at 20–33%. T. murphyi make up a small percentage of the catch (<10%, see above). In 2023–24, proportions of T. declivis, and T. novaezelandiae, were approximately 80%, and 19%, respectively.

In 2023–24, sampled sex ratios of T. declivis and T. novaezelandiae were close to a sex ratio of 1:1.

For T. declivis and T. novaezelandiae, observer data indicate decreasing proportions of larger and older fish in the commercial catch in recent years.