Managing the world’s wild fish stocks
Seafood consumption in Australia has steadily risen in recent years, with consumers also expecting retailers to hold supply chains accountable for delivering responsibly sourced, sustainable seafood.
Since the Commonwealth Harvest Strategy Policy was introduced in 2007, Australia’s wild capture fisheries have operated under national management objectives that set “best practice” targets.
Dr Richard Hillary is a Principal Research Scientist with CSIRO Oceans & Atmosphere. He says that CSIRO’s role is to analyse data from fishery experts around the nation, and to then advise how to practically implement the national best practice policy objectives.
Sustainable fishing relies on a strong understanding of how much seafood can be taken, while still allowing fish populations to be maintained. This relies on scientific stock assessments, which combine information from commercial and recreational fishers and on-the-water scientific observations.
Fish populations naturally rise and fall, somewhat unpredictably. Stock assessments are done by research scientists who specialise in particular fish species.
The scientists compare the past and current details of the age, size, reproductive and growth rates for a fish population, how many fish have been observed and information about catch volumes.
Then they predict how a fishery will respond to management measures which can include rules around catch limits, fishing seasons, and fishing area restrictions.
CSIRO’s research helps ensures ecological modelling and stock assessments give fisheries and consumers across Australia clear information about good seafood choices.
The key data underlying stock assessments now involves intricate biology and ecosystem information, from baseline data (how fast a stock grows, size and ages of the current population, when the fish matures and reproduces) to migratory behaviour and even genetic linkages.
Dr Hillary is part of a CSIRO team using a method called close-kin genetics to identify genetic matches between juveniles and adults in the spawning stock to measure species abundance. Lower matches indicate a bigger adult population.
“This combines some serious genetic analysis that wasn’t possible even five years ago, with some high-end statistics,” he says.
Reducing the uncertainty around stock levels has been the practical tool that’s helped harvest strategies bring back over-exploited stocks towards sustainable levels.
“For example, sardine populations are heavily influenced by environmental change because they are very short-lived, so there’s a lot of variation year-to-year. They are very productive fish, so the take size relative to population size is quite large, but it’s also quite variable.”
There are very different quota assessments for the Patagonian toothfish, a long-lived species centred around Macquarie Island, he says.
“This fish is not nearly as productive, and matures far more slowly so it has a much lower sustainable rate. Fishery harvest guidelines are designed so they don’t generally take too many of the fish when they’re younger, as they haven’t had a chance to reproduce.”
How stock management recovered the Southern Bluefin Fishery
Hillary works primarily on stock assessments for the Southern Bluefin Tuna fishery. The species was in severe decline during the 1970s and 1980s, severely overfished by several international fishing fleets, and has remained at a low level ever since. But it’s now a fishery with a good news story.
The stock began to recover thanks to a careful management program, implemented under Regional Fisheries Management Organisations that report to the UN Food and Agriculture Organisation, which is scientifically designed to have a high probability of recovering the stock.
CSIRO scientists have led research into this species for decades, and Hillary, who is a mathematician specialising in fish stocks, says that the turning point has been agreement on a formula that sets catch quotas based on verifiable data on population abundance.
Obviously, assessors don’t go out and count every fish. “The raw data often takes the form of fishery’s log books and observer reports and other information coming direct from industry.”
Standardised data for each fishery is evaluated by various resource assessment groups in each jurisdiction resulting in jurisdictional stock assessments that informs management decisions.
Big issues like climate-proofing various fisheries are addressed through wider networks that combine industry, scientists, government and community representatives. The strategies are eventually incorporated into the statistical models that drive stock assessments.
One-off events can also seriously impact fisheries, for example the recent large-scale mangrove die back in northern Australia, or this year’s Cyclone Debbie; these require wider thinking to assess the impact on fisheries, Hillary says.
“CSIRO can bring in biologists, ecosystem specialists and statistical people to figure out the linkage between, for example, mangrove forest and the affected stocks,” he says.
The journey to a national fish stocks report
Over the last decade, improved data collection and reporting methods on fish stocks have also introduced significant improvements in Australia’s fisheries harvest management.
For the first time in Australian fisheries management, a relatively new reporting tool, the Status of Australian Fish Stocks (SAFS) reports, brings together the best available biological, catch and effort information to determine the status of Australia’s wild catch fish stocks against a nationally agreed reporting framework. The stocks can be reported as negligible, undefined, sustainable, transitional-depleting, transitional-recovering, environmentally limited or overfished.
Each new issue of the reports has broadened its scope, starting with some 49 species and 150 discrete biological stocks of fish which accounted for 89 per cent of the total wild-caught fish in 2012. The latest report, issued in 2016, covers 83 species across 294 stocks.
Dr Carolyn Stewardson is the Projects Manager–Research for Fisheries Research and Development Corporation (FRDC), who co-ordinated the delivery of the SAFS 2016 reports, says the report is designed to be “a simple but scientifically robust tool informing fishers, consumers, managers and policy makers and the broader community about the sustainability of Australia’s wild-caught fish stocks”.
The SAFS reports “combine information across all jurisdictions”, she says, and “seek to become the most widely recognised and respected source of information on the status of Australia’s fish stocks”.
“Approximately 100 scientists have contributed to the work, while a further 50 scientists have been involved in an independent reviewing capacity to ensure the robustness of the analysis,” says Stewardson.
FRDC communications manager Peter Horvat says that while reports incorporate data about by-catch, habitat and fisheries management, the focus is largely on the status of the stock. The key to the SAFS report success is the verifiable quantitative data provided through fisheries stock assessments.
“Making the source data available adds to the robustness of the report,” Horvat says.
SAFS is now also found on the fish.gov.au website. Publicly available data tools let anyone report on different variables, such as by jurisdiction, and other information about various species over the past decade.
Into the future, the goal is to be consistent with the Global Sustainable Seafood Initiative (GSSI).
Cohesion with world standards makes the data even more robust and useful, and fisheries data is now also used by Atlantis – CSIRO’s ground breaking marine ecosystem modelling tool.
“A significant benefit of SAFS is that it informs stakeholders where to concentrate resources to address stocks that need rebuilding,” says Horvat.