The captain of a Spanish fishing vessel Thursday described "Dante-esque" scenes of horror on board a boat transporting would-be migrants from Africa to Europe, which had been adrift for 20 days after running out of fuel at open sea, according to dpa. More than 50 migrants were believed to have died. The fishermen first thought the boat was empty when they spotted it, silent like a ghost ship, Wednesday evening at more than 500 kilometres off Mauritania on the West African coast, captain Jose Maria Abreu said. But when they approached, they saw the only survivor feebly lift his hand among seven decomposing bodies. The vessel, which had set sail in Mauritania, was thought to have carried a total of at least 54 immigrants seeking to enter Europe. Survivors kept throwing bodies into the sea until there was only one of them left. "He was in a very serious condition," Abreu said. "We took him on board and helped him as we could, giving him food and water." "I am broken, I feel bad. Before being a captain, I am a human being," Abreu said, fighting back tears. A Spanish hospital ship went to meet the fishing vessel, taking the survivor and the bodies on board. Interior Minister Alfredo Perez Rubalcaba, the first to make the tragedy public, said about 13,000 undocumented immigrants had reached Spanish coasts so far this year, down from 35,000 in 2006. The drop is attributed largely to increased efforts to prevent illegal immigration, such as maritime patrols and repatriations, in cooperation with the European Union and African countries. Increased surveillance has prompted migrant smugglers to choose longer routes to the Canary Islands. Instead of Western Sahara, Mauritania or Senegal, boats now leave increasingly from Guinea-Conakry and Guinea-Bissau further down the West African coast. The boat whose only survivor was rescued on Wednesday had ventured out to the open sea precisely to steer clear of police patrols, captain Abreu said. The Spanish Interior Ministry was watching 50 boats moored in Conakry, which were suspected of trafficking with migrants, the daily El Pais reported. Thousands of Africans are believed to have lost their lives when attempting to reach Spain.