Agricultural Work Committee official Abu Zakariya Baker alleged Israel has tortured, shot and killed Palestinian fishermen since the blockade was tightened seven years ago, Ma'an News Agency reported.
"Israel is practicing all kinds of psychological humiliation against fishermen, often stripping them of their clothes while arresting them, even in times of extreme cold," said Baker, who called on the international community to prosecute Israel for crimes against Palestinians.
Gaza fisherman Rami Abu Amira, who was among the protesters, said the fishermen want the blockade on Gaza ended and the fishing zone expanded.
"Israeli forces open fire at us on a daily basis, detain fishermen and confiscate their boats," Amira said. "We want to live in dignity and freedom and we ask the whole international community to stand by our side."
Baker said more than 50 fishermen were arrested and 11 fishing boats destroyed last year, with Israeli actions against fishing boats on the increase.
The Israeli government extended Gaza's fishing zone to 6 miles in May, after having reduced it in March following a rocket attack from the coastal territory.
In the Oslo Accords, Israel agreed to a 20-nautical-mile fishing zone off Gaza but allowed only a 3-mile limit for several years, Ma'an noted.
Israel has controlled Gaza waters since 1967.