And then, as the offal and trimmings are dumped overboard, they swoop and dive, screeching as they go, a shrill frenzy of feeding seabirds.
Mollymawks and petrels have been doing it for more than a 100 years.
But not for much longer.
Regulations due to come into effect in September will outlaw the practice of dumping fish processing waste at sea, and some fear it could spell death by starvation for the birds. Taieri Mouth fisherman Tony Edmonds said his 12m trawler, Lady Ann, was regularly surrounded by seabirds, including mollymawks, petrels and, recently, royal albatrosses.
The birds had been fed by the boats for 100 years and cutting off their food supply overnight could lead to them starving, he said.
Fisheries Minister Jim Anderton proposed new measures in February that required fishing vessels to retain fish, offal and trimmings on board and to use devices to scare seabirds away from danger areas.
The measures come into effect on September 1 for trawlers and are already in place for surface and bottom longline vessels.
Those vessels were estimated to cause 3500-10,000 seabird deaths a year.
Albatrosses, including the smaller mollymawk, and petrels are attracted to fishing vessels by the bait that is put on longlines and also by waste discharged from the vessels as they process their catch.
The birds can dive under the water and take longline baits, become hooked and drown, or can be distracted by feeding on offal and fish discharge and get hit by the heavy steel cables that tow trawl nets.
Mr Edmonds said the regulations should be scrapped and instead the industry and Ministry of Fisheries could work together to find other ways to reduce the deaths.
"No-one wants to kill them."
He had already seen signs of starvation, with more birds following the boat right up to the mouth of the Taieri or coming up to the back of the boat to attack the net.
"We keep more alive in winter than die from fishing."
Department of Conservation Coastal Otago biodiversity assets programme manager David Agnew said waste from fishing vessels was not the seabirds' natural food source.
Any reduction in access to the waste would mean the birds had to seek out their natural food source - squid and surface fish.
"They have evolved over millions of years adapting to roam the vast area of the ocean and have a very efficient way of processing and utilising food."
