Captain Silver serves as the main antagonist in the anime Animal Treasure Island. He is an anthropomorphic pig who captains his own pirate crew, having previously sailed under the notorious Captain Flint. His appearance is characterized by a standard pirate captain's attire adorned with a skull emblem on his hat, complemented by a mustache and a hook in place of one hand.

In terms of personality, Captain Silver is portrayed as a consistently unscrupulous and antagonistic figure. He is driven by greed and a ruthless determination to claim Captain Flint's hidden treasure for himself. Unlike more complex interpretations of the character, this version exhibits few redeeming qualities and does not form a paternal bond with the young protagonist, Jim. His primary motivation throughout the story is the acquisition of Flint's treasure, and he will resort to kidnapping, betrayal, and exploitation to achieve this goal.

Captain Silver's role in the story is that of the primary obstacle Jim and his friends must overcome. He is introduced when he orchestrates the capture of Jim and his companion, Gran, during their sea voyage. He transports them to Pirate Island, where he sells them into slavery. After obtaining the treasure map from his own crew member, the Baron, Silver presents it to a council of pirate captains to secure command of a ship for the treasure hunt, overruling the Baron's claim to lead the expedition. Throughout the subsequent voyage, he persistently attempts to steal the map back from Kathy, who is Captain Flint's granddaughter, though his efforts are consistently thwarted by Jim.

Key relationships include his dynamic with Jim, whom he views purely as an obstacle, and with his own helmsman, a monkey named Spider, who remains loyal to him. His relationship with his crew is one of authority and command, though his self-interest becomes apparent when he abandons them after a shipwreck to continue the treasure hunt alone with only Spider by his side. His relationship with Kathy is adversarial, defined by his attempts to exploit her connection to the treasure.

Regarding development, Captain Silver remains a static character. He does not experience a redemption arc or undergo a significant change in personality. His treachery and greed remain constant from his first appearance to his last. After a storm destroys his ship, he abandons his stranded crew to continue his solitary quest. His end comes when he is tricked by Jim and Kathy at the treasure's location inside a volcanic crater. Acting on misinformation from Kathy, Silver triggers a mechanism that he believes will unlock the treasure. Instead, it catastrophically drains the volcanic crater lake, creating a flood that sweeps him and Spider out to sea. In the aftermath, he is last seen futilely pursuing Jim and Kathy's departing ship on makeshift log boats, still arguing with Spider and showing no signs of reform.

Notable abilities include his cunning and strategic mind, which he uses to manipulate other pirates and plan the treasure hunt. He is also a capable combatant and leader, effectively commanding his crew through a combination of authority and intimidation. His use of a hook in place of a hand is a notable physical characteristic, though no specific fighting skills with it are detailed.