The grass goby is a common fish in shallow coastal waters, estuaries and brackish lagoons, on muddy bottoms hosting seagrass meadows, their ideal habitat. It does not tolerate water that is particularly low in salt content, while it is very resistant to cold temperatures. It is a highly territorial species that digs burrows in the mud between the roots of plants; the burrows have a different structure and function depending on the time of year. There is only one entrance and the depth seems to be inversely related to the temperature of the water. Each burrow has a single occupant. In the summer, after reproducing, adults make for deeper water, where they dig a different type of burrow to those where they spend the winter or use for reproductive purposes. It might consist of a short tunnel ending in a round chamber, or a horizontal tunnel with two entrances. The inner surfaces of the burrows are compact and covered with a mucous film. The goby is caught locally in a variety of ways, especially with traps baited with crab meat. Another particularly effective bait is the “moleca”, molting specimens of the crab Carcinus mediterraneus. The most specific form of fishing, now almost fallen into disuse, is carried out at low tide during the winter months. Fishermen walk through a lagoon, often for long distances, and when they find a burrow they simply reach down into it and pull out the goby.