as Mr. Cobain was wont to moan, but it looks like that piece of sushi (or, maybe that fried thing getting in the way of the mushy peas and chips) could count:
Their numerical ability is on a par with that of monkeys, dolphins and children aged between six months and 12 months. “We have provided the first evidence that fish exhibit rudimentary mathematical abilities,” said experimental psychologist Christian Agrillo, of the University of Padova in Italy.
From the whole story on the BBC’s Love Earth(!) site:
… as Agrillo points out: ‘The most interesting thing is that fish performance is very similar to what is observed in adult humans who possess a very limited vocabulary for numbers.’ For example, speakers of the Amazonian language Mundurukú lack words for numbers beyond five. ‘Their limits in quantity tasks closely resemble what we found in pre-verbal organisms such as fish!’ says Agrillo.