This description relies on Birdlife International (2014) and ACAP (2023).
Traditionally with longline operations, hooks are deployed (set) from the stern of the vessel. As the name suggests, side-setting requires the setting operation to move to the side of the vessel. Birds are unable or unwilling to forage for bait close to the side of a vessel. Additionally, side-setting avoids setting baited hooks into the propeller wash, which slows the sink rate of stern set hooks. Deploying hooks from the side as far forward as possible enables the baited hook to sink to a certain depth before reaching the stern of the vessel.
Scientific evidence for effectiveness in pelagic fisheries
Side-setting has been shown to be more effective than other simultaneously tested mitigation measures, including setting chutes and blue dyed bait, on relatively small vessels in the Hawaiian pelagic longline tuna and swordfish fisheries (Gilman et al., 2003, Gilman et al 2016, ACAP 2023). Testing in the Hawaiian fisheries was conducted with an assemblage of surface-feeding seabirds. The effectiveness of the technique in southern hemisphere fisheries (with diving seabird species, larger vessels and over a larger spatial scale) has not been researched and consequently it is not recommended as a proven mitigation measures in these fisheries at this time (ACAP 2023).
Side-setting must be used in combination with ACAP best practice recommendations for line weighting in order to increase sink rates forward of the vessel’s stern, and hooks should be cast well forward of the setting position, but close to the hull of the vessel, to allow hooks time to sink as far as possible before they reach the stern. Bird curtains, a horizontal pole with vertical streamers, positioned aft of the setting station, may deter birds from flying close to the side of the vessel. The combined use of side-setting, line weighting and a bird curtain should be considered as a single measure.
Notes and Caveats
Hooks must be sufficiently below the surface and protected by a bird curtain by the time they reach the stern of the vessel. In Hawaii, side-setting trials were conducted with a bird curtain and 45-60 g weighted swivels placed within 0.5 m of hooks. Japanese research concludes it must be used in combination with other measures (Yokota & Kiyota 2006). The Hawaiian trial was conducted in an area with an assemblage of largely surface-feeding seabirds, and this measure requires testing in other fisheries and areas where seabird abundance is higher and secondary ingestion (hooks retrieved by diving birds and secondarily - subsequently - attacked by surface foragers) is more important. Hence, it cannot be recommended for use in other fisheries at this time.
Minimum standards
Clear definition of side setting is required. The Hawaiian definition is a minimum of only 1 m forward of the stern, which is likely to reduce effectiveness. The distance forward of the stern refers to the position from which baits are manually deployed. Baited hooks must be thrown by hand forward of the bait deployment location if they are to be afforded “protection” by being close to the side of the vessel.
Combinations of measures
Lines set from the side of vessels must be appropriately weighted in accordance with ACAP best practice advice and protected by an effective bird curtain (ACAP 2023).
Effect on Other Bycatch Species

None recorded.

Ease of Deployment and Safety
Fouled gear
Side-setting could increase the likelihood of gear becoming entangled in the propeller especially in rough seas, although, in the Hawaii trial deliberate attempts to entangle gear in the propeller were unsuccessful.
Operational efficiency
In Hawaii,  side setting has been found to deliver several operational advantages.
- By utilising a single work area for setting and hauling, more space may be available on deck for the crew to work in;
- The Captain is likely to have a better view of a side workstation, which has safety and efficiency implications; and
- Less bait may be lost in propeller turbulence and line tangles may be less common.
Cost Information
Conversion costs
A single one-off cost is incurred to refit the deck gear. In terms of overall running costs, this is a relatively minor expense.
Requires fisheries observers or electronic (e.g. video) surveillance.
Further Research
Further experimental trials are required to establish whether side-setting is feasible for all size classes of vessel*, under a range of sea conditions and across diverse seabird assemblages. Currently untested in Southern Hemisphere fisheries against assemblages of diving seabirds (e.g. Procellaria sp. Petrels and Puffinus sp. Shearwaters) and albatrosses - urgent need for research.
*Preliminary trials suggested that side-setting was operationally feasible on larger vessels (Yokota and Kiyota 2006).
  1. Birdlife International. 2014. Bycatch Mitigation Fact-sheet 9 (September 2014), Pelagic Longline: Side-setting.
  2. ACAP. 2023. ACAP Review of mitigation measures and Best Practice Advice for Reducing the Impact of Pelagic Longline Fisheries on Seabirds. In: ACAP - Thirteenth Meeting of the Advisory Committee. Edinburg, UK.
  3. Gilman E., Brothers, N., Kobayashi, D., Martin, S., Cook, J., Ray, J., Ching, G. and Woods, B. 2003. Performance Assessment of Underwater Setting Chutes, Side Setting, and Blue-Dyed Bait to Minimize Seabird Mortality in Hawaii Pelagic Longline Tuna and Swordfish Fisheries. Final Report. National Audubon Society, Hawaii Longline Association, US National Marine Fisheries Service Pacific Islands Science Center, US Western Pacific Regional Fishery Management Council. Honolulu, Hawaii.
  4. Gilman E, Chaloupka M, Peschon J, Ellgen S. 2016. Risk Factors for Seabird Bycatch in a Pelagic Longline Tuna Fishery. PLOS ONE 11:e0155477.
  5. NOAA. 2010. Summary of Hawaii Longline Fishing Regulations. National Oceanic and Atmospheric Administration, National Marine Fisheries Service Pacific Islands Regional Office. Honolulu, Hawaii.
  6. NOAA. 2014. 2013 Annual Report - Seabird Interactions and Mitigation Efforts in Hawaii Longline Fisheries. National Oceanic and Atmospheric Administration, National Marine Fisheries Service Pacific Islands Regional Office. Honolulu, Hawaii.
  7. Yokota, K. and Kiyota, M. 2006. Preliminary report of side-setting experiments in a large sized longline vessel. WCPFC-SC2-2006/EB WP-15. Paper submitted to the Second meeting of the WCPFC Ecosystem and Bycatch SWG. Manila, 10th August 2006.