Small size, big role
Understanding the place of small pelagic fish within the larger food chain is a crucial part of managing these highly variable fish stocks
Photo: Paul Watson
By Karin Derkley
New research being undertaken along the east coast of Australia is helping to assess the adult biomass of commercially and recreationally targeted pelagic fish species to better estimate future sustainable harvest levels.
Small pelagics, also known as forage fish, are the species on which other, larger pelagic fish such as tuna and barracuda like to dine. Small pelagic species are also a major part of the diets of many other predators, including sea birds, sharks, seals and dolphins.
Given their role in the food chain, supporting a host of higher-order predators and as part of developing commercial fishery, accurate assessments of fish stocks are crucial. The FRDC is supporting a suite of projects to develop and refine assessment techniques.
This work is being led by Tim Ward, who is the research leader for finfish at the South Australian Research and Development Institute (SARDI). He says that many small pelagic species share Australian waters, but only a few are fished commercially. Most of Australia’s fisheries targeting these species are relatively new or have been fished inconsistently.
Many small pelagic fish move in huge schools, which make them easy picking for predators, be they fish, bird or beast. But there is evidence that some species are also subject to significant natural population fluctuations, as the fledgling South Australian sardine fishery discovered in 1995 when large numbers of sardines were found dead off the coast of southern Australia.
A similar event occurred in 1998. As much as 70 per cent of SA’s sardine stock was estimated to have died in each event, although the populations have since recovered off south-eastern Australia.
Commercially, Australian Sardines are highly sought-after to feed the burgeoning tuna ranching industry, and markets for human consumption have been developing since 1994 at least. In SA, the sardine fishery was established in 1991 and has since grown to replace most baitfish imports used to feed farmed tuna in the Spencer Gulf.
From the first annual catch of just 10 tonnes, the harvest in SA has grown to about 34,000 tonnes a year, worth about $22 million.
Tim Ward says there has been significant work undertaken in SA to develop stock assessment techniques. These techniques are now being expanded to the east coast of Australia, and to other species, as part of a range of FRDC-funded projects. This includes benchmarking current practices to ensure Australian approaches reflect international best practice.
Many Australian fisheries use the catch per unit effort (CPUE) method, where a measure of the effort needed to catch a certain amount of fish is used to monitor the abundance of the stock
in a particular area.
However, Tim Ward says that the CPUE method is misleading for schooling fish such as sardines and mackerel. One shot or haul could catch hundreds, if not thousands, of fish – whereas others might deliver none. Catch rates can stay high even if overall abundance is low, because modern equipment is very effective in finding schools.
In Australia and internationally, the daily egg production method (DEPM) is widely accepted as the most effective way to assess stocks of schooling pelagic fish. When the average number of eggs produced by a female adult is known, the number of eggs found in a sample area can be used to determine the breeding biomass of adults.
The age and size frequency curve for the population can then be used to calculate an estimate for the target stock biomass.
“We’ve done a lot of work with sardines in SA, but we’re not sure yet if the sardine stocks along the east coast have the same reproductive parameters,” Tim Ward says.
He expects this information will emerge from surveys undertaken in January and September 2014.
The summer survey of the New South Wales, Victorian and Tasmanian coast was the first dedicated DEPM survey of Jack Mackerel conducted in Australia and involved concurrent sampling of eggs and adults.
“We sampled the key spawning sites during the peak spawning season and collected 2700 adults during the survey, so we are expecting to generate robust estimates
of adult biomass.”
Below: South Australia’s Tim Ward is leading efforts to improve assessment of small pelagic fish stocks around Australia. Photo: SARDI
The DEPM surveys completed in September 2014 targeted eggs and adults of Blue Mackerel (Scomber australasicus), Australian Sardine and Tailor (Pomatomus saltatrix) along the NSW and Queensland coast. The University of Tasmania, the NSW Department of Primary Industries and the Queensland Department of Agriculture, Fisheries and Forestry participated in the project.
While state and commonwealth fisheries are often managed independently, the multi-jurisdictional approach in this research recognises that fish populations move between management zones.
Tim Ward says an analysis of the survey data is still being completed and will be discussed at a meeting of small pelagic fishery researchers and stakeholders scheduled for March 2015.
Information from a review of the Commonwealth small pelagic fishery harvest strategy being undertaken by Tony Smith, who leads CSIRO’s fisheries ecosystem-based management research and assessment group, will also be taken into account.
As part of the work to benchmark Australian practices against international best practice a Small Pelagic Fisheries Workshop and Forum was held in Adelaide in August.
Among those attending was Paul Watson, executive officer of the South Australian Sardine Industry Association. He says as Australia’s small pelagic fisheries, such as the sardines, are relatively new, they have been able to avoid mistakes that led to overfishing of these species in other parts of the world.
“We’ve had the luxury of coming into it with the benefit of seeing what had been done elsewhere.”
He says it was reassuring from an industry perspective to find that the DEPM is used worldwide as a stock-assessment tool. “It is clearly the global standard,” he says.
The conference heard from a range of speakers who gave a global perspective on the status of their respective fisheries – size, value, funding models, management systems – and provided an overview of the developments in the research being undertaken.
Speakers included leading US pelagic scientist Nancy Lo, who has more than 40 years’ experience working as a biometrician in marine fishery science and who has helped to develop and validate many of the most-used fishery statistical models. Together with her colleague Kevin Hill, she provided an overview of the latest work in the US and for the North American Sardine in particular.
Cindy van Damme provided an overview of Atlantic Horse Mackerel. She has spent the past decade working on small pelagic fisheries in the northern hemisphere (North Sea). She is widely recognised as a leading researcher in small pelagic fisheries, in particular for egg, larvae and fish surveys.
Leire Ibaibarriaga, a senior researcher in the Pelagic Fish and Fisheries area in the Marine Research Division of Spain’s AZTI Tecnalia, provided an overview of work related to the Spanish Anchovy and also of the International Council for the Exploration of the Sea Working Groups.
At the forum, Australian scientists discussed the different statistical methodologies employed to analyse data collected for application of the DEPM with international researchers.
At present, fisheries around the world use a variety of statistical methods to estimate egg production. During the workshop, SARDI’s Jonathan Carroll demonstrated that no one technique suits all situations. As part of the research for the FRDC he is developing guidelines on what procedures should be used in different circumstances, depending on the species, location and time.
Addressing another part of the DEPM project, SARDI oceanographer John Middleton discussed the simulation model being developed that will help the factors that affect the capacity to estimate egg production to be understood with accuracy and precision.
“At the moment, there is significant uncertainty around estimates of egg production,” Tim Ward says. “This project will help us provide more precise estimates of fish abundance, which will enable managers to set total allowable catches with even greater confidence.”
This is important, he says, because fisheries managers are starting to use the DEPM to assess the abundance of a range of new species, including snapper and Tailor.
Forum participants were impressed by Australia’s management approach, particularly a study of SA’s sardine fishery that showed that the precautionary approach to management is achieving its goal of ensuring ecological sustainability.
This long-term study was conducted by Simon Goldsworthy’s team at SARDI in conjunction with the pelagic fish team and a large group of students.
It found that, even while the number of sardines harvested in the state had increased, there was no detectable negative impact on birds and animals that forage on the sardines.
Chair of the Small Pelagics Forum Colin Buxton, from the Institute for Marine and Antarctic Studies, says the ecosystem study was described as one of the best global examples of studies of the roles of fisheries species in the ecosystem.
There is also support for robust science-based stock-assessment methods for small pelagic species from Australia’s recreational fishers who target larger species.
“Small pelagics are an important resource in terms of their ecological role within the environment,” says Andrew Rowland, chief executive officer of Recfishwest.
“It is very important we have a clear understanding of this role as well as their biomass and stock structure. It is critical that we invest in research to attain the level of knowledge we require to effectively manage this fishery.”
Brett Cleary, president of the Game Fishing Association of Australia, also supports the research into stock structure and biomass. However, he believes more work still needs to be done on understanding stock movements and the impact of localised depletion.
“We need a better understanding on how long it takes for fish stocks to be replaced in a particular area. Because even while the percentage of fish taken by commercial fishers may be small overall, the impact of taking them from a particular area may be significant for those such as recreational fishers and the communities that depend on them economically, and also ecologically for the birds
and seals that feed on them.”
Small pelagic species
Species being assessed as part of the FRDC-funded research include Australian Sardines, Jack Mackerel, Blue Mackerel (Scomber australasicus), Redbait (Emmelichthys nitidus) and Tailor (Pomatomus saltatrix). Some, such as Jack Mackerel, are not so small, growing to more than 60 centimetres. Other well-known non-target species include Australian Herring (Arripis georgianus) and Yellowtail Scad (Trachurus novaezelandiae). In the Northern Territory development licences have recently been issued to assess the commercial potential of several species, including Smallspotted Herring (Herklotsichthys lippa), Goldstripe Sardinella (Sardinella gibbosa) and Indian Anchovy (Stolephorus indicus).
New market opportunities
Photo: Peter Cunningham
Most small pelagic fish harvested in Australia are used as baitfish for the tuna ranching industries. A small amount is used in petfood, and less than two per cent are for human consumption. This is because small pelagics are oily fish that require immediate processing to avoid spoilage. On-vessel processing and freezing is expensive and requires large-scale operations.
One company that has managed to overcome these obstacles is Western Australia’s Cape Le Grande. In conjunction with Curtin University’s Centre for Excellence for Seafood, Science and Health, Cape Le Grande, under managing director Tim Rowe, has developed a strict supply-chain protocol to harvest Australian Sardines for human consumption.
The fish are stored in ice slurries immediately after being caught off the Western Australian coast and filleted as soon as they are landed.
The company has had positive responses from chefs who have tried their product, and is hoping that more Australian chefs and consumers will follow the lead of countries such as Spain, Italy and Greece, where sardines are a staple on restaurant menus.
The South Australian Sardine fishery is also expanding into higher-value, human consumption markets.
FRDC Research Codes: 2013-028, 2013-063, 2014-026, 2014-053
Tim Ward, 08 8207 5433