Back to FISH Vol 30 1
PUBLISHED 4 Mar 2022

Good science is the basis of credible assessment initiatives to help consumers choose sustainable seafood

By Ilaria Catizone

Consumers are increasingly demanding proof of their seafood’s sustainability and they are turning to a range of seafood certifications, rating programs and indices to inform their purchases.

Globally, there is a growing number of initiatives to guide consumers. But they do not all measure and report on the same parameters.

Reporting on stock sustainability is often cooperatively implemented by governments, either internationally (for example, Food and Agriculture Organization of the United Nations’s [FAO’s] Fishery Status Reporting Process), or nationally (for example, the Status of Australian Fish Stocks [SAFS] Reports). These programs typically focus on stock sustainability – the capacity of the fished stock to maintain itself at a given level of abundance – rather than on sustainability in a broader sense that may include considerations such as bycatch, carbon footprint or plastic use.

Some schemes provide endorsement for specific fisheries and species, such as the Marine Stewardship Council (MSC) certification, which is highly regarded internationally but comes with costs that not every fishery can afford.

Some programs attempt to provide a broader picture of sustainability, combining assessments of fish stocks with social and economic indicators, ecosystem assessments and management measures.

The scope, scientific rigour and transparency behind the many initiatives can be highly variable, although they all generally involve assessment against predetermined requirements, using fish biomass as a starting point.

To help users evaluate the different programs, the Global Sustainable Seafood Initiative (GSSI) has a Global Benchmark Tool that assesses the assessors. GSSI is a public–private partnership focused on seafood sustainability with more than 90 stakeholders industry-wide. GSSI aligns global efforts and resources to address seafood sustainability challenges.

To date, the GSSI has recognised nine sustainability certification schemes relating to aquaculture operations and fisheries, including the Marine Stewardship Council program mentioned above, which relates to fisheries internationally.


Image of a Southern Bluefin Tuna. Photo: Shutterstock
The effectiveness of fisheries management based on sound science was, once again, demonstrated recently when Southern Bluefin Tuna, a formerly overfished and depleted stock, was rated as sustainable. Photo: Shutterstock


Sustainability indices for management

Although gaining community support is essential, sustainability indices are also important management tools, because they shed light on the factors that influence stock levels. This understanding is crucial to ensure these levels are kept within (or returned to) the sustainable range.

The effectiveness of fisheries management based on sound science was, once again, demonstrated recently when Southern Bluefin Tuna (Thunnus maccoyii), a formerly overfished and depleted stock, was rated as sustainable. This result comes after decades of careful management to rebuild numbers while allowing controlled fishing to support jobs and communities.

Sustainability indices use reference points to determine what stock levels are sustainable in each case. These points are the operational or measurable benchmarks that identify targets to be achieved on average, limits to be avoided and triggers to initiate management responses. Reference points are usually set in relation to fish abundance (biomass), fishing mortality (removals from the population due to fishing)
or both. 

Best-practice management involves setting reference points for both biomass and fishing mortality. Estimating stock biomass as well as fishing mortality is important, because biomass varies in response to non-fishing variables (for example, environmental effects) as well as fishing pressure.

The three main reference points used are: 

  • Target reference point: the point around which biomass and fishing mortality would ideally fluctuate. 
  • Limit reference point: the lowest biomass or highest fishing mortality a stock can withstand without becoming depleted. Management should be such that there is a very low likelihood of dropping below a limit reference point. Immediate management intervention is required if a limit reference point is breached. 
  • Trigger reference point: typically, intermediate between target and limit points, this provides the cue to initiate management responses to bring the stock back towards the target reference point. 

Reference points should be set according to clearly defined management objectives for a stock. Common management objectives include maximising sustainable food production, maximising economic returns from fishing, or maintaining a stock that is important for broader ecosystem function, such as an important prey species, at a precautionary biomass level. While pursuing these objectives, there is the ongoing need to avoid breaching limit reference points. 

Limit reference points tend to be set where irreversible (or slowly reversible) recruitment impairment would occur. 

Within the FAO for status reporting framework, a stock is considered to be: 

  • overexploited if present biomass is found to be less than 40 per cent of unfished biomass;
  • fully exploited if present biomass is between 40 and 60 per cent of unfished biomass; and
  • underexploited if present biomass is more than 60 per cent of unfished biomass.

Customising reference points

When fisheries managers set reference points, they use species-specific information to account for a stock’s population parameters, where possible. These may include characteristics such as life span, growth rate and reproductive age. There is a delicate balancing act in management to account for the natural variability of a species over time, fishing activity and responses to other environmental factors.

A species with a short life span, fast growth rate and young reproductive age may have lower reference points for biomass (allowing greater fishing effort), than a species with a long life span, slow growth rate and older reproductive age.

However, species with a fast growth rate and short life span typically have large natural variations in their abundance and excessive fishing pressure that coincides with a period of naturally low abundance or poor recruitment can cause a stock to collapse. So, in some cases, dynamic reference points may be needed to better reflect current circumstances and adapt to changing ones.

In other cases, a stock’s reproductive potential (for example, egg production) may be estimated. Some fisheries scientists have argued that measuring egg production would capture changes in fecundity, egg viability and sex ratio within a stock. In a different context, the Daily Egg Production Method (DEPM) is generally the most practical method for estimating spawning biomass for small pelagic species (for example, Sardines).

The role of a stock within its ecosystem is also an important consideration when setting reference points. Key prey or forage species, for example, may require conservative reference points to maintain ecosystem integrity.


Every two years, the FRDC funds and manages the collation of the SAFS Reports. These bring together available biological, catch and effort information to determine the status of Australia’s key wildcatch fish stocks from state, territory and Commonwealth fishery jurisdictions using a framework as shown in Figure 1.

Figure 1. Diagrammatic representation of the framework used by the Status of Australian Fish Stocks Report

SAFS Reports are used by a range of stakeholders, including fisheries managers and scientists, consumers and the seafood sector (including retailers). The reports are available on the SAFS website ( and via a user-friendly app, so consumers can use the findings to inform their purchases.

SAFS Reports represent a composite consideration of biomass and fishing mortality; for example, a sustainable status requires evidence that both biomass and fishing mortality are above the limit reference point.

The SAFS framework does not define standardised levels of biomass or fishing mortality as limit reference points. Rather, the limit reference point for biomass is defined as the point at which recruitment (the process by which new generations of young fish join the population) is likely to be impaired. Similarly, the limit reference point for fishing mortality in SAFS is the level of fishing pressure likely to either drive the stock towards the point of recruitment impairment, or prevent its recovery if impairment has already occurred. Teams of authors from each jurisdiction work together to define these points for each stock.

Since July 2018, SAFS summary information has been used to inform Australia’s progress against UN Sustainable Development Goal 14.4.1 (the proportion of fish stocks within biologically sustainable levels). f