In fact, many aquatic creatures are adapted to both marine and river habitats. The Classic of Mountains and Seas, from the Warring States period (475--221 BC), records that pufferfish are poisonous, and Wang Chong (27--c. 97) of the Han dynasty further notes that the poison is in the fishes 'ovaries and liver.
再從生態角度來看，許多水產其實是迴游於海、河之間的「兩棲類」，既是河鮮，也是海鮮。戰國時代《山海經》就記載河豚具有毒性，漢朝王充進一步指出河豚毒性在卵巢與肝臟。