On board Sirena, fisherman Paolo Fanciulli gives travelers an ecotour, then grills lunch fresh from his net.

Most mornings, you won't find me scrambling out of bed to make it to an 8 a.m. ecology class. But when the teacher is Paolo Fanciulli, the classroom is a fishing boat off the Tuscan coast and the lesson plan involves an onboard lunch of freshly caught fish, I'm up as early as I need to be.

On a recent, sunny Tuesday morning, I arrived with some friends at the port in Talamone to spend a day with Fanciulli, an energetic 41-year-old fisherman who takes tourists for boat rides along the coast of the Parco Naturale della Maremma, a national park of umbrella pines and wild, scrub-covered hills on the Tuscan coast about 60 miles south of Siena. Fanciulli has been leading these trips for 10 years as one of the pioneers of the eco-conscious pescaturismo trend, which combines outdoor adventure with an up-close look at the local environment. The tours are Fanciulli's way of helping to protect the sea where his father taught him to fish, and of showing off the beauty of his native region. Besides having spent a lifetime as a fisherman, Fanciulli is an official park guide and a member of Greenpeace; his fishing boat, Sirena, flies World Wildlife Fund flags.

Our group met in front of Sirena, stowed our bags in the cabin and departed for Le Cannelle, an inlet where icy freshwater springs meet the sea. As we navigated along the mostly rocky shoreline, Fanciulli pointed out some rare dwarf palms, a peregrine falcon in her nest and an old Etruscan port that local fishermen call Grotta del Buco, where he found an amphora as a kid. We cruised over sea-grass meadows, patches of nutrient-rich vegetation that, Fanciulli said, have been partially destroyed by illegal dragnet fishing; without sea grass—which produces oxygen, protects the coast from erosion and serves as a habitat and food source for many young fish—the ecosystem is endangered.

Apart from their educational mission, trips like these help Fanciulli make a living without putting the environment at risk. Since he and his assistant cook their catch right on the boat instead of taking it to market, where the smaller and lesser-known varieties are often rejected, they need to set out only a quarter of the nets they'd normally use.

Fanciulli controlled the electric winch that cranked up the net, naming each fish then tossing it into a seawater-and-ice-filled Styrofoam chest. I consulted a 1913 Italian text about fish, Doni di Nettuno, which lists many varieties in Italian, French, German, English and regional Italian dialects. The nets yielded scorfano, or scorpion fish ("You have to watch out—they've got poison in their spines," Fanciulli warned), sorriso (thornback ray), passera (a type of flounder), dentice (dentex), salpa (goldline), as well as orata, occhiata, mormora and fragolino (all members of the bream family). Seppie (cuttlefish) looked decidedly extraterrestrial, and one had a big chunk missing, "bitten by a greedy moray eel," Fanciulli explained. The moray eel soon ended up in the net too and was extracted with great care.

Fanciulli put on bright orange rubber gloves that matched his overalls and cleaned the fish, using closed scissors to scrape away scales and all trace of organs, rinsing the fish carefully in seawater and putting it back in the ice chest. He whistled to seagulls and threw them scraps. Then he flung a round, weighted-on-the-edges cast net into the sea, pulled it back out of the water and harvested a few squirming handfuls of rossetti—tiny, see-through, boneless fishlets that can be eaten whole.

The boat pulled into a protected cove, Cala di Forno, where we transferred to a motorized raft. Fanciulli took some of us for a walk while the rest chose to hang out on the sandy, shallow beach. We searched, unsuccessfully, for wild boar and deer ("Too late in the morning to find them," Fanciulli explained) and looked at the vegetation ("Wild asparagus in the spring, wild mushrooms in the fall, to add to our menu").

By the time we returned to Sirena, it was 1 p.m.—lunchtime. Fanciulli's assistant, Carlo Ombroneschi, was toasting bread on a large rectangular charcoal grill attached to the stern and hanging over the sea. During our absence he'd prepared a sauce with the rossetti in the boat's tiny galley. We all took seats around two long oilcloth-covered outdoor tables, our plastic glasses filled with mineral water or Grattamacco Bianco. We began our lunch with bruschetta topped with roast peppers, artichokes and sun-dried tomatoes packed in olive oil, made by a local organic producer, La Selva. While we ate the pasta with rossetti, delicate and decidedly un-fishy, Fanciulli placed a two-sided, long-handled grill sandwiching most of the morning's catch over the charcoal embers, then flipped it after a few minutes. Some of the fish was served whole and was hard to bone with plastic forks and knives; we had better luck picking it apart with our fingers. The fish, especially the breams and sole, were superb, and even the small goldline ("No commercial value—we have to eat them ourselves or give them away," Fanciulli said) had a pleasingly subtle flavor. For dessert, we ate almond biscotti and fresh strawberries, lightly sugared and served from airtight containers. Ombroneschi made espresso. The feast now complete, Sirena slipped back to Talamone.

Back at home in Florence, I went seafood shopping with Fanciulli's voice in my ear. I bypassed anything I hadn't seen on his boat, asked for wild and local fish and bought sole to substitute for the totally unfindable rossettii. "Never clean fish with freshwater, only seawater," Fanciulli had instructed. So I mixed some makeshift seawater by combining filtered water and sea salt. The dishes I made from his and Ombroneschi's recipes tasted very much as they had on Sirena. The only missing ingredients were the swaying of the boat and the salty sea breeze.

(To reserve a place on Sirena, call Paolo Fanciulli at 011-39-328-202-67-59 or 011-39-333-284-61-99. The cost is $65 per person.)

Faith Heller Willinger is the author of Eating in Italy and Red, White & Greens.