A Seadra's quills are often described as poisonous, and indeed the substance inside them does have toxic effects when it pierces the skin. What the quills actually contain, however, is ink – the same ink that is sprayed when one uses smokescreen, and the same ink that was once used to write all books, although in these days it is reserved for religious texts and other books intended to be of great importance.
In the days before the printing press and the quill-pressing machine, Seadra were as numerous as Tentacruel. Although occasionally killed for their ink even then, books were a rarity, a luxury for temples and the wealthy, and therefore the amount of Seadra killed in this manner was not especially high. Seadra, after all, possess a multitude of quills, and the length of a book in the old days was based not on the amount of paper available, but on the amount of ink a writer could get out of a single Seadra.
Although the printing press ended the era of quills being used in the traditional manner, as pens and pencils, it also created an enormous demand for ink. Seadra were hunted by the boatload, the survivors hiding themselves in islands or the deep sea or behind whirlpools or even in a certain cave in Blackthorn. They escaped the great hunt better than most pokemon who have faced overhunting, being powerful, majestic, and fairly popular in their own right, but their numbers did not begin to recover until other inks were developed from various berries and grass-type pokemon.
