Seabird bycatch mitigation measures

How are birds caught?

During the setting of longlines birds scavenge the baits attached to hooks before the bait can sink. Once hooked, birds are drawn underwater by the sinking longline and drown. Most of the birds that are vulnerable to being caught have learned to follow boats ever since commercial fishing began, feeding on the discards and bait.

What can be done?

There are two ways of keeping birds from being hooked. One is to keep the birds away from the hooks, by using a bird-scaring device such as a streamer line.

Figure 1. Streamer line designed by CCAMLR to discourage birds from scavenging baits during the deployment of longlines, showing the towing point (tp) and streamer line (sl). Designs should vary according to the fishery and the vessel. Redrawn from a diagram by John Cox.

Graham Robertson/Australian Antarctic Division A drowned Wandering Albatross – caught on a longline Zoom In

The second avenue is to keep the baited hooks away from the birds – most of the vulnerable birds predominantly feed during the day, so ensuring that fishermen only set their lines at night is very effective. Making sure that the bait sinks as quickly as possible means that the birds have less time to scavenge and are thus less likely to get hooked. Below is a list of measures aimed at reducing seabird bycatch – if you know of any other effective measures please email us with the details:

• Line should be set at night time
• An approved streamer line should be deployed during all line-setting operations. The streamer line should be deployed directly above the main line, unless two streamers are used in which case they must be deployed on either side of the main line
• The main line and branch lines must be properly weighted to ensure optimal sinking rates
• Dumping of offal should take place on the opposite side to where line hauling occurs
• A bait-throwing device which shoots the baited hooks clear of propeller turbulence may be effective (this has not been proven and may throw the bait out of the area covered by the streamer line)
• All bait should be properly thawed – frozen bait floats and is available to the birds for a longer time
• Whole fish with a swim bladder should not be used as bait (air in bladder causes bait to float)
• Deck lighting kept to the minimum (without compromising crew safety)
• All deck lights should be directed inboard
• Dumping of offal should not take place during line setting
• All hooks should be removed from offal and from the fish-bycatch before these are dumped; i.e. no hooks discarded

None of these measures alone will solve the problem. Implementing them all has been proven to bring bird catch rates down to biologically safe levels without seriously affecting the catching of fish.

It is essential that records be kept of fishing effort, fish catches and unwanted fish and seabird bycatches. Without these data there is no way of knowing how serious a problem birds are for a particular fishery. This means that the fishery may continue to catch birds unnecessarily, when some simple and inexpensive changes to fishing practices could bring about rapid changes for the birds.