Download FAR 2024/55 Length and age structure of commercial landings of blue cod in BCO 5 (2022 and 2023), and characterisation of the fishery

Blue cod (Parapercis colias) is the main inshore finfish commercial fishery in Southland (fishstock BCO 5) with catches as far back as the 1930s. Historically blue cod were predominantly taken by line fishing, but in the mid-1980s a pot fishery rapidly developed, and this is now the prevalent commercial fishing method for targeting blue cod. The fishery operates mainly within Foveaux Strait, off the east and west of Stewart Island, and in southern Fiordland. Most of the catch is taken in 10 to 100 m depth but they are caught as deep as 150 m in some places. This report describes the results of a catch sampling programme carried out in 2021–22 and 2022–23 fishing years, together with a characterisation of the commercial fishery.

Historically, about half the commercial catch has been from Statistical Area 025 (Foveaux Strait) with about one fifth in each of area 027 (east of Stewart Island) and area 030 (southern Fiordland), but landings from area 025 have declined steadily with the contributions dropping to about one third of the catch in 2023. The cod potting fishing vessel fleet size has steadily declined from a peak of 75 vessels in 1994, to around 35 vessels in the last two years.

The results from the catch sampling programme showed that the three areas have different age structures with fish smaller and younger in area 025; which is indicative of high fishing pressure. Year-class strengths were not consistent among statistical areas suggesting that recruitment (i.e., the numbers of juvenile fish entering the fishery) may differ across BCO 5 stock areas. There was a strong trend of increasing proportions of male blue cod in commercial catches over the time series in area 025 with 96% of fish male in 2023; heavily fished populations tend to be male dominated.