Strabo Geography 3.2.7

[7] Such is the wealth of the inland part of Turdetania, and its maritime portions are found fully to equal it in the richness of their sea-productions. In fact, oysters and every variety of shell-fish, remarkable both for their number and size, are found along the whole of the exterior sea, but here in particular. It is probable that the flow and ebb tides, which are particularly strong here, contribute both to their quantity and size, on count of the great number of pools and standing waters which they form. ¹ The same is the case with regard to all kinds of cetacea, narwhals, whales, and physeteri, ² which when they blow [up the water from their snouts] appear to observers from a distance to resemble a cloud shaped like a column. The congers are quite monstrous, far surpassing in size those of our [sea]; ³ so are the lampreys, and many other fish of the same kind. It is said that in Carteia there are kerukae ⁴ and cuttle-fish which would contain as much as ten cotylae. ⁵ In the parts more exterior there are lampreys and congers weighing 80 minae, ⁶ and polypesa talent, ⁷ also teuthidae ⁸ two cubits in length, with other fish in proportion. Shoals of rich fat thunny are driven hither from the sea-coast beyond. They feed on the fruit of a species of stunted oak, which grows at the bottom of the sea, and produces very large acorns. The same oaks grow in large numbers throughout the land of Iberia, their roots are of the same size as those of the full-grown oak, although the tree itself never attains the height of a low shrub. So great is the quantity of fruit which it produces, that at the season when they are ripe, the whole coast on either side of the Pillars is covered with acorns which have been thrown up by the tides: the quantity however is always less on this side the Pillars [than on the other]. Polybius states that these acorns are ejected [by the sea] as far as [the shores of] Latium, unless, he adds, Sardo ⁹ and the neighbouring districts also produce them. The thunny-fish become gradually thinner, owing to the failure of their food, as they approach the Pillars from the outer sea. This fish, in fact, may be regarded as a kind of sea-hog, being fond of the acorn, and growing marvellously fat upon it; and whenever acorns are abundant, thunny-fish are abundant likewise.