Bassam El-Najjar once made his living from the seas off Gaza's coast. For two decades he set out each morning to catch tuna, sardines and mackerel from the waters of the eastern Mediterranean.

Not any longer. Now El-Najjar drops his nets into a large fish pool dug in the earth of a 0.5 hectare farm near Khan Younis in the central Gaza Strip. "The sea is closed," he says, scooping a handful of pellets and scattering them across the water. Freshwater tilapia come to the surface, swallowing the feed.

Banished from the sea, El-Najjar and many other Gazans now look to fish farming instead. The 42-year-old father of four has traded his boat for a small holding several kilometres inland. He walks to the other side of the pool and turns on the sprinkler system that aerates the water. The pool, which he shares with his brother, produced 350 kilograms of fish this season. However, says El-Najjar, "if the sea was open in front of me, sometimes I could catch that in a day."

From the northern city of Akka near the Lebanese border to Rafah's port on the edge of Sinai, the sea has been a source of sustenance for Palestinians along this coast for centuries. Many Gazans are descendants of traditional fishing families. Some are originally from the Gaza Strip, but the majority are refugees pushed south from coastal cities like Jaffa and Ashkelon, now in Israel.

Ten years ago, Gaza's fishermen ventured 20 nautical miles (nm) from shore, as guaranteed under the Oslo Accords. That has dropped to a three-nm limit enforced by the Israeli navy, which fires on fishermen crossing the boundary. Israel says the restrictions are necessary to halt weapons smuggling and the infiltration of militants into the country. However, Gaza's prime fishing waters lie above an undersea crag six nm from the shore, where larger fish migrate in the shelter of the rocks. Confined to shallow waters where raw sewage flows into the Mediterranean from a war-damaged treatment plant, desperate fishermen pull young and spawning fish from the sea, critically damaging future stocks.

In the late 1990s, Gaza's fishing industry was worth US$10 million (Dh36.73m) per year, supporting about 10,000 fishermen, but only 3,000 fishermen remain at sea. Most now rely on food aid and rations provided by the UN or charitable organisations.

Once famed for its seafood restaurants, Gaza now imports fish from Israel and smuggles live and frozen fish underground from Egypt. But the price is beyond the reach of many. In Gaza City's fish market there are obvious signs of decline. Below a martyr-style poster of a young fisherman killed by the Israeli navy, disgruntled men tend stalls stocked with undersized fish and complain about the restrictions and small catches.

Millions of sardines will pass through Gazan waters in the summer months as they migrate north from the Nile Delta to Turkish seas. Indeed, sardines once accounted for 70 per cent of the annual catch. However, because of the recent escalation in violence, many fishermen are apprehensive about venturing even to the three-nm mark, saying that the Israeli navy shoots more quickly in times of tension.

It isn't just the sea that is blocked. Much of Gaza's agricultural land, where farmers once grew crops and herded animals, has been placed off-limits by an Israeli security-justified buffer zone. These restrictions are compounded by the blockade.

"Protein intake for Gazans has plummeted, partly due to the blockade of the land and partly due to the blockade of the sea," says Simon Boas, the UN Food and Agriculture Organization's coordinator for the Gaza Emergency Programme.

Dov Weissglas, then-adviser to the Israeli prime minister, was quoted in 2006 as saying: "We need to make them lose weight, but not to die." The policy seemed to be: make Gazans hungry enough to reconsider electing Hamas, but not starving to the point of a humanitarian - and therefore diplomatic - crisis.

Inspired by these years under siege, the Hamas-run government is working to make Gazans independent food producers. In agriculture, the government developed ways to grow vegetables without imported fertilisers and pesticides. For the fishing industry, this meant investing around $1m (Dh3.67m) in fish farming infrastructure and technology. For food security, aquaculture is an ideal solution: fish convert feed into human-consumable animal protein much more efficiently than either cows or sheep.

Fishermen and farmers suffer the highest levels of food insecurity in the territory. "It's the only group whose food insecurity is rising," Boas says. El-Najjar's family is one of 50 vulnerable families assisted by the FAO project to supplement their diets and incomes. His family now has all the fish it can eat from their 120 cubic metre pool. The rest he sells for about 10 Israeli shekels (Dh11) per kilogram - a price that is affordable for many here but one that earns him no more than a few hundred shekels per month.

El-Najjar's fish farm produces both fish and homemade fertiliser. While commercial fish farming has been criticised in many developed countries, all of Gaza's fish farms are on land, greatly reducing pollution. El-Najjar also uses the fish-infused run-off water to fertilise a quarter-acre guava orchard - saving him near 1,000 shekels per year in expensive Israeli fertiliser.

"In so many other places, this is terribly trendy and green," Boas says. "But in Gaza, resources are so scarce this is actually a necessity."

Alas, Gaza's isolation prevents fish farmers from benefiting from their neighbour's knowledge and technology. Both Egypt and Israel have advanced aquaculture industries, which in theory puts Gaza in a geographically ideal position to foster its own production. Many of those working in Gaza's industry today were trained in Israel, but few Gazans are now granted permission to enter the country.

Instead, most farms now rely on Iyad Deeb al Attar, who runs a hatchery near Beit Lahia in the northern Gaza Strip. Al Attar is something of an expert - he worked for 15 years in the Israeli cities of Haifa, Ashkelon and Ashdod as well as Dugit, an Israeli settlement that once stood not far from his current farm. When Israel pulled its army and settlers out of Gaza in 2005, it took the fish farms with them. Al Attar decided to start his own.

"The market needs 18,000 tonnes each year," estimates al Attar. The tonnage of farmed fish produced in the Gaza Strip has doubled each year since 2007. This year, the output from Gaza's fish farms is predicted to top 200 tonnes and is expected to continue to grow rapidly.

Most of the fish farmed in Gaza are tilapia - either silver tilapia from the Nile or red tilapia brought in from Israel. In his eight-pool greenhouse, al Attar spawns six species of fingerlings, baby fish, which he sells to farms across the Gaza Strip, including the project run by FOA and a dozen commercial farms. He also provides training to Gazans who want to start production. He now gets supplies - food as well as breedable mother fish - from Israel. "Before that, we were bringing what we needed from Egypt, through the tunnels," says al Attar, pulling a net-full of baby red tilapia to the surface. Bags of Israeli fish feed lie stacked on the side of the greenhouse.

"What we need is to produce our own fish food," says Adel Jamel Atallah, director general of the fisheries department. Almost all the fish feed in Gaza comes from Israel, leaving the industry reliant on high-priced imports subject to Israel's whim.

A basic machine to produce fish food pellets costs about $75,000. It requires expertise to make a pellet that has the right quantity of protein and still floats.

"But electricity is the main problem - it's off about eight hours per day," says Atallah.

Gaza suffers a massive power deficit and electricity is essential to run machines that pump oxygen into the water. Farmed fish can die in few hours without it. Some fish farms have human-powered systems using pedals to keep the water moving. Others simply throw their children in the pools as splashing around is enough to oxygenate the water, although those who can afford it use generators.

Behind the fisheries department near Gaza City's main port, lies a mostly empty,0.8-hectare plot of land. The government is looking for funds to develop a hatchery, research facility and aquarium for children. Despite the challenges Atallah is optimistic. He unrolls the blueprint for a new pool model that will allow farmers to grow more fish per cubic metre, pointing to the rounded bottom and Gazan-designed drain system. Raising more fish per pool will be necessary if the industry is to develop, particularly considering the high cost of running electric aerators.

Even if Gazans can increase production, Boas says there is one more challenge. "The battle is getting people used to eating freshwater fish. For many people here, fish still come from the sea."

Rebecca Collard is a Canadian journalist and photographer based in Jerusalem.