The quatrefoil frame at the bottom of the February calendar page contains the zodiacal emblem of Pisces, two fish arranged parallel to one another with their heads facing in opposite directions, as is usual in medieval astrological representations. In The Book of Fixed Stars, Alfonso X explains that one of the starry fish is in the north sky and one in the south (Teresa Pèrez-Higuera, Medieval Calendars, 1998).
In his Etymologiae, the encyclopedist Saint Isidore comments that the name Pisces is appropriate to February because it is such a rainy month. Although fishing was a common medieval activity, it is rarely represented in the medieval calendar tradition, and has no association with a given month or season (Pèrez-Higuera).
Timothy Husband conjectures that the two elongated objects roasting on the grate in the scene depicted at the top of the page may well be fish fillets, an ironic complement to the paired zodiacal fish shown here at the bottom (The Art of Illumination: The Limbourg Brothers and the Belles Heures of Jean de France, Duc de Berry, 2008). Fish would be likely to be eaten in February, as it is typical Lenten fare. Lent begins in February in any year in which Easter falls earlier than April 17 (The Oxford Companion to the Calendar Year).