Tropical tuna are one of the few wild animals we still hunt in large numbers, but finding them in the vast Pacific ocean can be tremendously difficult. However, fishers have long known that tuna are attracted to, and will aggregate around, floating objects such as logs.
In the past, people used bamboo rafts to attract tuna, fishing them while they were gathered underneath. Today, the modern equivalent – called fish aggregating devices, or FADs – usually contain high-tech equipment that tell fishers where they are and how many fish have accumulated nearby.
It’s estimated that between 30,000 and 65,000 man-made FADs are deployed annually and drift through the Western and Central Pacific Ocean to be fished on by industrial fishers. Pacific island countries are reporting a growing number of FADs washing up on their beaches, damaging coral reefs and potentially altering the distribution of tuna.
Our research in two papers, one of which was published today in Scientific Reports, looks for the first time at where ocean currents take these FADs and where they wash up on coastlines in the Pacific.
We do not fully understand why some fish and other marine creatures aggregate around floating objects, but they are a source of attraction for many species. FADs are commonly made of a raft with 30-80m of old ropes or nets hanging below. Modern FADs are attached to high-tech buoys with solar-powered electronics.
The buoys record a FAD’s position as it drifts slowly across the Pacific, scanning the water below to measure tuna numbers with echo-sounders and transmitting this valuable information to fishing vessels by satellite.
Throughout their lifetimes FADs may be exchanged between vessels, recovered and redeployed, or fished and simply left to drift with their buoy to further aggregate tuna. Fishers may then abandon them and remotely deactivate the buoys’ satellite transmission when the FAD leaves the fishing area.
The Western and Pacific Ocean provides around 55% of the worlds’ 5 million tonne catch of tropical tuna, and is the main source of skipjack, yellowfin and bigeye tuna worth some US$6 billion annually.
Fishing licence fees can provide up to 98% of government revenue for some Pacific Island countries and territories. These countries balance the need to sustainably manage and harvest one of the only renewable resources they have, while often having a limited capacity to fish at an industrial scale themselves.
FADs help stabilise catch rates and make fishing fleets more profitable, which in turn generate revenue for these nations.
However, they are not without problems. Catches around FADs tend to include more bycatch species, such as sharks and turtles, as well as smaller immature tuna.
The abandonment or loss of FADs adds to the growing mass of marine debris floating in the ocean, and they increasingly damage coral as they are dragged and get caught on reefs.
Perhaps most importantly, we don’t know how the distribution of FADs affects fishing effort in the region. Given that each fleet and fishing company has their own strategy for using FADs, understanding how the total number of FADs drifting in one area increases the catch of tuna is crucial for sustainably managing these valuable species.
Our research, published in Environmental Research Communications and Scientific Reports, used a regional FAD tracking program and fishing data submitted by Pacific countries, in combination with numerical ocean models and simulations of virtual FADs, to work out how FADs travel on ocean currents during and after their use.
In general, FADs are first deployed by fishers in the eastern and central Pacific. They then drift west with the prevailing currents into the core industrial tropical tuna fishing zones along the equator.
We found equatorial countries such as Kiribati have a high number of FADs moving through their waters, with a significant amount washing up on their shores. Our research showed these high numbers are primarily due to the locations in which FADs are deployed by fishing companies.
In contrast, Tuvalu, which is situated on the edge of the equatorial current divergence zone, also sees a high density of FADs and beaching. But this appears to be an area that generally aggregates FADs regardless of where they are deployed.
Unsurprisingly, many FADs end up beaching in countries at the western edge of the core fishing grounds, having drifted from different areas of the Pacific as far away as Ecuador. This concentration in the west means reefs along the edge of the Solomon Islands and Papua New Guinea are particularly vulnerable, with currents apparently forcing FADs towards these coasts more than other countries in the region.
Overall, our studies estimate that between 1,500 and 2,200 FADs drifting through the Western and Central Pacific Ocean wash up on beaches each year. This is likely to be an underestimate, as the tracking devices on many FADs are remotely deactivated as they leave fishing zones.
Using computer simulations, we also found that a significant number of FADs are deployed in the eastern Pacific Ocean, left to drift so they have time to aggregate tuna, and subsequently fished on in the Western and Central Pacific Ocean. This complicates matters as the eastern Pacific is managed by an entirely different fishery Commission with its own set of fisheries management strategies and programmes.
Growing human populations and climate change are increasing pressure on small island nations. FAD fishing is very important to their economic and food security, allowing access to the wealth of the ocean’s abundance.
We need to safeguard these resources, with effective management around the number and location of FAD deployments, more research on their impact on tuna and bycatch populations, the use of biodegradable FADs, or effective recovery programs to remove old FADs from the ocean at the end of their slow journeys across the Pacific.
Joe Scutt Phillips, Senior Fisheries Scientists (Tuna Behavioural Ecology), Secretariat of the Pacific Community; Alex Sen Gupta, Senior Lecturer, School of Biological, Earth and Environmental Sciences, UNSW; Graham Pilling, Principal Fisheries Scientist, Secretariat of the Pacific Community, and Lauriane Escalle, Fisheries Scientist, Secretariat of the Pacific Community
Shopping can be confusing at the best of times, and trying to find environmentally friendly options makes it even more difficult. Welcome to our Sustainable Shopping series, in which we ask experts to provide easy eco-friendly guides to purchases big and small.
Tuna is a massive industry and most of this catch ends up in cans. But while each can of tuna might look similar, the environmental impacts of different brands vary. So, with a sea of “eco-friendly” labels and choices, how do you know which is the most sustainable?
Australia produces large amounts of high-end seafood such as rock lobster, abalone and fresh tuna, but most of this doesn’t end up in our supermarkets – it is exported to countries willing to pay more. Instead, roughly 70% of all seafood eaten in Australia is imported. Most of this includes lower-value products such as frozen fish, frozen prawns and canned tuna.
Australia is a major market for canned tuna. Almost all of the canned tuna sold here comes from Thailand, which processes about half of the world’s tuna supply. It is now almost impossible to buy Australian-produced canned tuna since large-scale production in Australia ended in May 2010.
While it is not unusual for a developed country to import large amounts of seafood, Australia is failing to meet international standards for sustainable seafood trade. Australia has strict requirements for seafood exports, but seafood imports are largely unregulated. This means it can be difficult to know if the imported seafood you buy was caught sustainably or even legally.
High global demand drives unsustainable fishing practices. These practices include overfishing, issues related to bycatch (which is the accidental catch of other marine animals like dolphins, turtles and seabirds), and “illegal, unregulated and unreported” (IUU) fishing. Now, 77% of the world’s fisheries are fished at their limit or beyond.
Unsustainable fishing practices have devastating effects on the health of the marine ecosystem and the livelihoods of fishers. With this in mind, it is more important than ever to know about the origin of your fish.
Some species of tuna are fished at sustainable rates, whereas others are overfished. The most common species that end up in cans are skipjack and yellowfin tuna. Both of these species have sustainable stocks in the Western and Central Pacific Ocean (WCPO). Skipjack also has sustainable stocks in the Indian Ocean. Higher-value species such as bigeye and bluefin varieties are usually reserved for sushi and sashimi markets. Southern bluefin tuna is overfished and is listed as critically endangered by the IUCN.
The most sustainable fishing methods for tuna are “pole-and-line” and “FAD-free purse seine”. However, each method has a catch.
Pole-and-line fishing is the traditional method of using a pole, line and hook to catch fish. The rate of bycatch is small because fishers can catch and release non-tuna species. However, bait fish are used to attract the tuna, which can have a large impact if the bait fish is not caught in a sustainable way. Due to the labour-intensive nature of pole-and-line fishing and dependence on bait fish, this method makes up only a small proportion of the total tuna caught and is unable to supply tuna in large amounts.
Purse seine fisheries use a large net to surround a school of fish. In recent years purse seiners have increasingly used fish aggregating devices (FAD) to attract tuna and increase their efficiency. However, FADs also attract bycatch and juvenile tuna and are poorly regulated. Therefore, only purse seine fisheries that set on free-swimming schools of tuna are considered sustainable.
1. Read the label
Examine the details on the back of the can for tuna species, fishing method and catch location. There are sustainable options for each of these categories.
The best approach is to opt for skipjack before yellowfin or other tuna varieties. Next, choose tuna caught using “pole-and-line” or “FAD-free purse seine” before “longline” or “purse seine”. Then, check for tuna caught in the Western Central Pacific Ocean – this may appear on the can as FAO Nr. 71. If the can doesn’t at least identify the species or fishing method, it’s probably not worth your time.
2. Consider eco-labels over unverified self-claims
Eco-labels and eco-claims often feature prominently on tuna cans. Eco-labels are market-based tools used to promote sustainable practices. Decoding them can seem challenging, but it doesn’t have to be.
First, it is important to recognise that a dolphin-safe label is not a sustainability label. It focuses only on the impacts of fishing on dolphins. Dolphin-safe doesn’t consider tuna catch levels or other socio-environmental impacts. Most importantly, it doesn’t require independent third-party verification.
In contrast, some newer eco-labels consider a wider set of impacts including target species stock levels, impact on other species and even the social impact on fishers – such as fair pay and work conditions.
In recent months, the MSC-certified Pasifical brand has been criticised because its FAD-free purse seine sourced tuna are transported on vessels that can also catch FAD-caught purse seine tuna. Some commentators argue that this enables unsustainable FAD-caught fisheries to continue operating.
On the other hand, MSC has the strongest chain of custody. It can trace every can of tuna from the supermarket shelf all the way back to the fishery. It’s not clear whether the original criticism was driven by competition for supermarket shelf space, as some industry insiders have claimed.
3. Download seafood guides
Various online guides are also available to help consumers choose sustainable seafood options. These guides rank and recommend seafood using a stoplight system. The recommendations are based on available scientific research or a defined set of criteria.
4. Future technologies, supply chains and transparency
While the steps above assist with making sustainable seafood choices, it doesn’t help if the fish you’re buying has been mislabelled. There is still uncertainty related to transparency and traceability in the supply chain.
To help combat this problem, Coles has partnered with WWF to ensure the seafood it sells is sustainably sourced. Aldi has also introduced an initiative called “Trace Your Tuna” to link tuna to its catch location.
New applications that use tracking data are also developing. Apps are available that scan QR codes and barcodes to provide consumers with extra information about the origins of lots of different products including seafood. These include Oziris in Australia, ThisFish in Canada and the Seafood Traceability System offered by the Korean government.
Simultaneously, new initiatives such as Global Fishing Watch are providing open access to vessel movement data, providing tremendous opportunities for transparency and traceability.
In short, the easiest way to make a sustainable choice when buying canned tuna is to check the contents label and look for a credible eco-label. If you have a little more time, it might be worthwhile to check out seafood recommendation guides or to download a product tracking app on your smartphone.
Shark numbers appear to be growing off the east coast of Australia. In recent days large numbers of sharks, including Tiger Sharks have been spotted of the southeastern coast of Queensland at Teewah, feasting on large schools of baitfish and tuna.
For more information on sharks visit: