Fishermen have always had a relationship with seabirds. For thousands of years, fishermen benefited from seabirds. In China and Japan, fishermen worked with cormorants to catch fish. Fishermen in the South Pacific would watch for seabirds on the horizon to guide where they should fish. The sight of birds was always a good omen for a good fishing day. However, with modern technologies and industrial fishing practices, that relationship has changed. Where once seabirds were seen as a benefit, seabirds are now often viewed as a problem.
With modern fishing practices, fishermen have been throwing baits and fish waste over the side. Seabirds cue in immediately on this easy meal and have learnt to target and follow fishing boats. Fishermen have been inadvertently training seabirds to follow boats. In the case of longline fishing, this means less fish for the fishermen per unit effort because seabirds remove baits from the hook, which means fewer baits per set, less fish caught per set and more fuel, wages and ship time to make up for the lost fish.
The reality is that birds are much better at finding fish than we are. Millions of years of evolution have provided seabirds with an acute sense of smell and fantastic vision. They can detect fishing vessels from up to 30km away[1]. Add the ability to fly vast distances in strong winds and severe conditions, and you have the consummate airborne predator/scavenger. Seabirds have learned that fishing boats mean a free feed!
[1]Julien Collet, Samantha C. Patrick, and Henri Weimerskirch (2017) A comparative analysis of the behavioural response to fishing boats in two albatross species. Behavioural Ecology (2017), 28(5), 1337–1347.