There is a well-established tradition of studying mathematical abilities in mammals and birds; however it is only in the last half-decade that different studies have proposed that some species of fish possess similar capacities. Data collected by spontaneous choice tests and training procedures indeed support the existence of rudimentary quantity abilities in teleost fish.

In this talk we will review the current state of knowledge on numerical competence in guppies and mosquitofish, with particular regard to three main issues surrounding numerical abilities in nonhuman animals: the existence of a single vs. multiple systems of numerical representation, the relation between numerical and continuous quantity, and the ontogeny of numerical abilities. The evidence reported in literature is suggestive of similar numerical systems in fish and mammals, raising the intriguing possibility to use fish in the near future as species model to investigate the roots of our non-symbolic numerical abilities.