Age structured production model and Harvest Control Rules for New Zealand orange roughy

• Devise a new model for a management strategy evaluation
• Make an Exploratory Analysis of the initial Stock Assessment 
• Redesign responsive Harvest Control Rules (HCRs) based management procedure
  

Progressing towards recertification

Orange roughy are a long-lived deepwater species that mature later in their lives. Consequently, ensuring the stock’s sustainability requires comprehensive Harvest Control Rules (measures that require catch to be adjusted in response to stock changes). These rules are based on models that identify the age at which the fish reach sexual maturity and can replenish the population.

The New Zealand 3B East & South Chatham Rise orange roughy fishery has been making improvements, verified by the In-Transition to MSC Program, since 2023. The fishing operation is guided by scientists, policy makers and industry interests in the Deepwater Council, who had concerns around the limited number of age groups represented in previous stock assessment samples. To make more accurate models of abundance and inform total allowable catch levels further data on the size and maturity of the fish was needed.

The Transition Assistance Fund grant will enable the project to collate data on the age and size composition of the orange roughy stock from a wide timeseries: 1990s, 2000s, 2010s.

The project will last two years, and the fishery expects to enter assessment towards certification to the MSC Fisheries Standard by late October 2028.

What the project will do

Funds from the grant will be used to develop a range of age structure production models, incorporating the entire catch history as well as biomass data from acoustic surveys. These are considered the most reliable indicators of stock abundance. They will incorporate estimates including the age of reproductive maturity, numbers of individual fish that are spawning eggs, and the efficiency of the fishery.

The operating models would be used to further develop responsive Harvest Control Rules that would inform management direction for the fishery.

The models would be tested in simulation phases and adapt to the total allowable catch in accordance with the most recent survey’s results, and future patterns indicating the maturity of the stock.