The Tunisian trawler radioed in for help as it passed the migrant boat in distress out at sea. But with the packed craft still adrift two days later, captain Chamseddine Bourassine took direct action.
Fishermen from the North African country are spending more and more time pulling in stranded migrants after a sharp decline in humanitarian and European naval patrols along the stretch of water between war-wracked Libya and Italy.
Mr Bourassine, his crew and three other fishing boats ferried the 69 migrants back to shore on May 11, five days after their boat pushed off from Zuwara on the western Libyan coast.
"The area where we fish is a crossing point" between Zuwara and the Italian island of Lampedusa, said Badreddine Mecherek, a Tunisian fisherman from Zarzis near the border with Libya.
Fisherman from Zarzis have saved the lives of hundreds of migrants in recent years, and as the number of boats leaving western Libya for Europe spikes with the return of calmer summer seas, they will probably have to save even more.
"First we warn the authorities, but in the end we end up saving them ourselves," Mr Mecherek grumbled as he tinkered with his rusting sardine boat.
European countries in the northern Mediterranean are trying to stem the number of migrants landing on their shores, and the Tunisian navy with its limited resources only rescues boats inside the country's territorial waters.
Since May 31, Tunisia itself has barred 75 migrants from coming ashore after they were saved in international waters by a Tunisian-Egyptian tug boat.
Tunisian authorities have refused to comment.
"Everyone has disengaged" from the issue, said Mr Mecherek, adding it was hampering his work.
Fishermen who run across migrants on their second day out at sea are at least able to have done a day's work, he added, "but if we find them on the first night, we have to go back".
"It's very complicated to finish the job with people on board."
The complexity of the rescues grows when fishermen find migrants adrift closer to Italy.
When Mr Bourassine and his crew last year tugged a boat towards Lampedusa which was adrift without a motor, they were jailed in Sicily for four weeks for helping the migrants. It took months to recover their boat.
Humanitarian boats and those of the European Union's "Operation Sophia" anti-piracy force had scooped up most stranded migrants in recent years, but rescue operations dropped in 2019.
"Now most often we are the first to arrive... if we aren't there, the migrants die," Mr Mecherek said.
On May 10, a Tunisian trawler just barely saved the lives of 16 migrants after they had spent eight hours in the water. Sixty others drowned before the ship arrived.
Survivor Ahmed Sijur said the boat's appearance at dawn was like that of "an angel".
"I was loosing hope myself, but God sent us the fishermen to save us," the 30-year-old from Bangladesh said.
Mr Mecherek is more worried than proud.
"We don't want to see all these corpses anymore. We want to catch fish, not people," he said, adding his crew was growing uneasy.
"I have 20 seamen on board asking, 'Who will feed our families?'" he added.
"But local fishermen will never let people die at sea."
For Tunisian Red Crescent official Mongi Slim, the fishermen "are practically the police of the sea", adding that many migrants say large ships won't stop to help.
Under pressure to catch their quota during a short annual season, big tuna boats out of Zarzis often call the coast guard instead of stopping themselves to help.
"We report the migrants, but we can't bring them back to shore... We only have a few weeks to fish," said one crew member.
For Mr Chamseddine, the summer months look difficult.
"With fighting having resumed in Libya, traffickers are free to work again. There's a risk of many shipwrecks."