The Arlong Pirates (アーロン海賊団, Āron Kaizokudan) or the Arlong crew (アーロン一味, Āron Ichimi) were led by Arlong. Every member of the crew was a mermen, except for Nami (who later left). They existed before the Sun Pirates, but joined with them when they were formed and after the death of Fisher Tiger, they split from Jimbei's crew, after he became a Warlord and became their own crew again. They believe they are above humans as the stronger species, looking down on them as an inferior species. After they were defeated, they were arrested. Momoo was never taken into custody and Hachi later escaped. The crew is no longer active. Their ship was Shark Superb.
They existed before the creation of the Sun Pirates, but gladly joined with them upon their creation. After the death of Fisher Tiger and when Jimbei became one of the Warlords of the Sea the crew split from the Sun Pirates and returned to being the Arlong Pirates, who then left the Grand Line for East Blue, which had much weaker prey. Arlong had also attempted to recruit both Hyouzou and Vander Decken IX, the first eventually turned down Arlong after he would fail to pay his hiring and the second refused to be the underling of another.
Eight years before the present storyline, the Arlong Pirates invaded an island and forced the residents to pay a large monthly tax for their own survival — 100,000 berries per adult, and 50,000 berries per child. Bellmère was only able to pay for her daughters, so Arlong killed her as an example, leaving her adopted daughters Nami and Nojiko. Seeing how skilled at map-making Nami was at such as early age, Arlong kidnapped her and forced her to become a member of his crew making maps for her. In order to convince her, he struck a deal—if she can somehow gather 100,000,000 berries and give it to him, he will free her village. Thus, Nami began her life as a thief. As a show of their power, the crew constructed their headquarters, Arlong Park, in clear sight. They struck deals with corrupt Navy officials like Captain Nezumi in order to prevent attacks and started to build up their forces to take over all of East Blue.
During the present day, Arlong had already conquered over 20 villages but Nami was getting dangerously close to her goal, and Arlong was getting worried. If Nami left, he would lose a valuable part of the team, as her maps were essential for coming up with strategies. Thus, he told Nezumi where Nami kept all of her money and had him confiscate all it, but Nami and the other villagers instantly realized that Arlong was behind it and finally decided to fight back.
After several long and difficult battles, the Arlong Pirates were defeated by Team Natsu and the Straw Hat Pirates, with Luffy defeating Arlong as well as destroying Arlong Park, freeing the entire island from Arlong's reign. He and his surviving crew were arrested, though Hatchan managed to escape and start a takoyaki restaurant..
Arlong's flag is that of a saw-nosed shark turned to the left with the tail curving inward. Around the shark is a semi-oval with three curves emitting from it. Behind the shark is a cross bone. This flag is tattooed onto all members of the crew. Several members of the New Mermen Pirates, Hordy Jones and Hammond in specific, also has this tattooed on to their bodies, out of respect for Arlong and his ideals.