Jack mackerel (Trachurus murphyi, Nichols 1920) is widespread throughout the South Pacific, chiefly along the shelf and oceanic waters adjacent to Ecuador, Peru and Chile, as well as the Subtropical Convergence Zone, in what has been described as the “jack mackerel belt”, stretching from the coasts of Chile to New Zealand within a 35º to 50º S variable band across the Pacific. In the mid-1980s, owing to large recruitment influxes, the jack mackerel stock size reached approximately 14 million tonnes of spawning biomass, one of the largest fish stocks in the world, sustaining catches up to 5 million tonnes per year until the mid-1990s. However, due to the large fishing fleets operating in the area in combination with low recruitment, the stock size began to diminish and, by the mid-2000s, the stocks were badly overfished and heading for collapse. A population once estimated to be reaching 14 million tonnes dropped to less than 2 million tonnes in just two decades.

 The first SPRFMO scientific committee meeting was held in 2013. Based on discussions and analyses conducted at SC meetings, a robust assessment of progress takes place annually. Data collected on the environment in relation to the fisheries serves a single purpose, that the conservation and management measures concerning jack mackerel are based on the best scientific information available, including:

• Specific catch data — length, length composition, age-length keys, length frequency, catch per unit of effort and standardization thereof, effort to account for changes in fleet behaviour, abundance index, and others

• Fisheries independent data — observers onboard fishing vessels, surveys using hydro-acoustics to estimate jack mackerel biomass, egg and larvae surveys

• Biological parameters — reproductive biology, maturity-at-age, ageing, and natural mortality

 Concerning the jack mackerel fishery, the Commission has always accepted and fulfilled the SC’s recommendations throughout the range of the stock, which has ensured its rebuilding.

Today, southeast Pacific jack mackerel shows a sustained recovery since the time-series low point in 2010. The population trend is estimated to be increasing. The indications of stock improvement are: a higher abundance observed in the acoustic survey in the northern part of Chile; better catch rates apparent in some fisheries; and an increase in average age in the Chilean fisheries. Assessment models show similar trends with an increasing overall biomass, high recruitment in recent years, and low fishing mortality. The estimated biomass has increased in all model configurations and is now well above BMSY (the biomass that enables a fish stock to deliver the maximum sustainable yield).

Jack mackerel has therefore been rebuilt to the third tier of the proposed harvest control rule. After eight years of sustainable fisheries management, the jack mackerel fishery in the South Pacific is returning to safe levels. The latest SPRFMO SC advice shows that stocks are improving significantly and, in 2019, the SC estimate was 55 per cent higher than in 2014, a testament to the importance of independent scientific advice. This demonstrates that transparent and proactive Regional Fisheries Management Organizations such as SPRFMO, capable of adopting binding conservation and management measures at the regional level, are a successful tool for fisheries regulation in the high seas.

Excerpt from: A Better World - Volume 6 (humandevelopmentforum.org)

Successful science-based fisheries management in the South Pacific

Dr. Sebastián Rodríguez Alfaro, Executive Secretary; Osvaldo Urrutia S., Chairperson,

South Pacific Regional Fisheries Management Organisation (SPRFMO)

A Better World Volume 6

Human Development Forum (2020)