The search for fishing gear that is both ecologically and economically sustainable is not easy, but continuing data collection is helping fishery managers make more informed decisions.
Finding fishing gear that optimises catches while reducing bycatch is a constant balancing act of ecological, social and economic factors. Two FRDC research projects were carried out in 2020 and 2021 to test the viability of alternative fishing gear that could minimise harm to endangered, threatened and protected species (ETPS) and other bycatch species.
Reducing bycatch can lower the amount of labour required of fishers, help avoid interactions with species important to other fishing groups and reduce harm to ETPS. But the gear that reduces bycatch must also provide a commercially viable catch.
A better way to fish
The ‘A Better Way to Fish’ project was conducted jointly by researchers from James Cook University and commercial fishers, to explore the feasibility of using tunnel net fish traps to replace N2 mesh nets in north Queensland (Project 2018-149).
Tunnel nets are large mobile fish traps that can be deployed and retrieved over a single tidal cycle. Their successful use in Moreton Bay in southeast Queensland for decades contributed to interest in this project.
A trial in Cardwell, Queensland, explored the effectiveness of tunnel nets to catch the target species of Barramundi and King Threadfin Salmon while having minimal impact on bycatch. Photo: Andrew Chin, JCU.
In 2020 researchers and commercial fishers in Moreton Bay, Cardwell and Mackay came together to exchange knowledge on the feasibility of using tunnel nets in northern fisheries and to identify potential sites where they could be used. A week-long pilot trial was run in Cardwell in July 2021 to begin exploring the effectiveness of these nets.
Lead researcher Dr Andrew Chin of James Cook University says the main goal was to investigate if tunnel nets could catch the target species of Barramundi and King Threadfin Salmon while having minimal impact on bycatch.
“Bycatch in the Great Barrier Reef World Heritage Area has been an issue for decades. We wanted to try something new,” he says.
The research boat used for the tunnel net fishing trial. Photo: Andrew Chin, JCU.
ETPS unharmed
“The idea was to see if there was a different type of fishing gear that could be used to catch the fish they need to make a living, but which would reduce the death of bycatch species. These often include undersized fish, turtles, dugongs, and particularly Hammerhead Sharks,” Andrew says.
“The beauty of a fish trap is that you can catch everything in the trap, but you only harvest what you need. Everything else swims away. Sometimes you don’t even need to handle the animals at all.”
The trial in Caldwell found that the tunnel nets did indeed successfully trap large quantities of fish with no injury or death of bycatch species. Of note, several Hammerhead Sharks, the primary species of concern, were released completely unharmed.
However, while tunnel nets were proven to be technically feasible, Andrew says there is still a question around whether tunnel nets are commercially viable as a replacement for N2 mesh nets.
Andrew notes there are many factors that need to be considered in real-world operations. Tunnel nets require very specific conditions including a sheltered coastal flat with the right substrate and beach profile, and in north Queensland should only be used in winter. They are also more labour-intensive than a normal N2 mesh net.
Commercial tunnel net fisher John Page was involved in the trials, and he cautioned that the gear should be considered as niche gear for specific situations. Unless the required conditions were met “it may be doable, but probably not advisable,” he says.
Andrew adds that there is a considerable financial outlay for equipment. “You also need two to four fishers to make it work, and you need enough fishable area so that you can rotate between spots.
“However, the product kept is also very fresh as it is put straight into an ice slurry, and it could potentially be marketed as ‘trap caught’ fish.”
While there is a lot more to learn, Andrew emphasises the importance of researchers and fishers working together as co-investigators in the project.
Longlines in Bass Strait
Another FRDC project that explored the costs and benefits of using automatic longlines for Gummy Shark fishing in Bass Strait as an alternative to the conventional gillnets. This followed on from a previous FRDC project completed in South Australia which primarily focussed on reducing the bycatch of Australian Sea Lions caught in shark gillnets (Project 2019-129). Potential transition of shark gillnet boats to longline fishing in Bass Strait – ecological, cross-sectoral and economic implications)
Lead researcher Dr Ian Knuckey of Fishwell Consulting says while Sea Lions do not occur in Bass Strait, there are other types of ETPS to be avoided such as dolphins and seals.
From an ecological perspective, populations of dolphins and seals are more robust than those of Australian Sea Lions, and bycatch numbers are very low, but as populations of seals increase the chance of interactions with gillnets will also rise.
Gummy Shark populations are very healthy and provide the bulk of the flake we eat in fish and chip shops.
“Fishers obviously don’t want to have interactions with protected or threatened species. What they’re looking for is options that can mitigate the risks and ensure they retain their social licence to operate,” Ian says.
A trial of auto-baited longlines was run over 30 days across key Gummy Shark fishing areas around King Island, Flinders Island and Lakes Entrance. The longlines were able to successfully target Gummy Sharks with very low catches of School Sharks and Snapper and no major impacts on ETPS.
While this was good news, the longlines did have a large bycatch of Draughtboard Sharks – a species that is common throughout Bass Strait. While Draughtboard Sharks are edible, they are difficult to process and produce very little yield, so are of limited commercial interest to fishers. Nevertheless, industry is exploring new market opportunities for this species.
Bird interactions
Bass Strait is known as a key region for seabirds in south-eastern Australia, with breeding colonies of shearwaters, penguins, petrels and prions. There are specific times and places when risks of seabird capture can be high, such as when they’re feeding their chicks.
“The need for longline fishers to avoid catching seabirds is a big issue,” says Ian. “We didn’t want to swap from one ETP issue to another in the potential move to longlines.”
To reduce the risk of capture, all longline vessels are required to operate under the Seabird Threat Abatement Plan (TAP2) which sets down very strict seabird bycatch triggers.
In line with the TAP2, seabird mitigation techniques were used during the longline trial and no birds were caught. However, Ian notes that the scope of a 30-day trial is limited and a more comprehensive trial of commercial longlines over greater spatial and temporal scales is warranted.
The trial also assessed the financial implications for a gillnet vessel moving across to a longline operation, but there were limitations on how well the trial could reflect normal commercial operations.
Fishers assisting with the trial had to fish in some areas where they did not expect to catch large numbers of Gummy Shark but were also not able to keep fishing as they normally would, where there was a good catch rate of Gummy Shark. Instead, they needed to move to new locations to meet the spatial and temporal coverage of Bass Strait required for the project.
“So, the economics of the trial didn't rule it out as a viable option, but it probably wasn't a good representation of what a fully commercial vessel might do,” Ian notes.
The potential change of fishing gear is a complicated task that projects such as these work to inform. “It's really about balancing the costs and benefits of changing fishing methods to reduce unwanted ecological interactions but ensuring fishing remains viable from both an economic and social point of view,” says Ian.
This reflects R&D Plan Outcomes 2 and 5
