Five nautical miles off the Cape of São Vicente, the warm night is not enough to lighten the focused expression of Fábio Mateus, a young fisherman and master of the trawler Flor de Burgau. Mateus and most of his fishing colleagues strongly believe that a turning point in the sardine fishing industry has already been reached. “It is true that we went through times of crisis, but now the sea is full of sardines,” he says while manoeuvring the boat. The absence of fish on board, however, seems to contradict his words.

A few minutes before the sun rises, the journey that began at 2am seems destined to fail. Suddenly, a red spot on the sonar monitor creates agitation on board. The blast of a loud horn awakens the crew of six sleeping under deck who quickly grab their nets. A cloud of loud seagulls and the water splashes of a group of bottlenose dolphins are my signals to enter the water. Holding my breath, with camera in hand, I dive into a duel between man and nature.

Below the surface, the scenario is one of war. The sound of the boat engines assaults my ears and makes my heart race. Meanwhile, great black-backed gulls rip through the water column like torpedoes. Terrified, thousands of sardines swim fast as bullets, in all directions during an increasingly tight and deadly encounter. Mateus and his team use purse seine nets to catch the sardines, the dominant fishing method off the Portuguese coast. The method utilises a long, high net wall that surrounds the targeted fish and reduces their escape routes. While the bottom edge is held down by weights, the top edge is usually buoyed by floats. When a large school of fish is surrounded, the bottom can be drawn together to enclose it.

After quickly drawing a circumference, leaving behind a gigantic 300-metre-long and 90-metre-high net, the trawler returns to its starting point where the chata, the support boat, waits to close the trap. It is a dance of precision and gestures that has been repeated a thousand times by generations of fishermen. At the water’s surface, bright yellow buoys mark its location. “Arreia,” shouts a man with rubber boots, as they throw cables from one vessel to the other. When pulling the retenida, a guide cable sewn to the bottom of the net, it closes the fishing device, sealing the fate of the fish inside.

In less than an hour, the wild capture ends and we make our way back to Sagres fish market. On board are smiles, good spirits and 3,000kg of fish. “So, was I right or was I wrong?” asks Mateus in a teasing, friendly tone. Despite the lucky catch for the crew, the team are concerned for the future. “With the low price of sardines nowadays, if the government does not considerably increase the quota [for allowed captures], I’m not sure how long we’ll be able to hold on,” says Mateus.