花胶又称鱼肚，一种由大海鱼的鱼鳔制炼成的大块白色胶状物体，中国传统的名贵食品之一，属于海味的一种，「鲍参翅肚」中的「肚」所指的正是花胶。

在一些亚洲国家包括中国菜中被用作烹饪材料，一般品质的主要是用来加入炖汤，加强口感和黏稠度，品质高者亦可用来做成菜肴。

花胶跟鱼肚都是鱼鳔，因鱼的品种不同而分「鸭泡肚」〔淡水鲈鱼〕、「紥胶」〔海鲈鱼〕、「鳝肚」〔鳗及鳝类〕、「黄花胶」〔黄花鱼〕、「白花胶」〔白花鱼〕、「广肚」〔鳘鱼〕等，身价也有很大差别。

蝶胶为花胶的一种，是深海鳕鱼的鱼肚，因貌似蝴蝶而得名。蝶胶质感较其它花胶黏口，胶质也比一般花胶丰富。深海鳕鱼蝶胶每年产量不多，因此有人视其为花胶中之珍品。

The swim bladder, gas bladder, fish maw or air bladder is an internal gas-filled organ that contributes to the ability of many bony fish (but not cartilaginous fish) to control their buoyancy, and thus to stay at their current water depth without having to waste energy in swimming. Also, the dorsal position of the swim bladder means the center of mass is below the center of volume, allowing it to act as a stabilizing agent. Additionally, the swim bladder functions as a resonating chamber, to produce or receive sound.