Question sent by NURIA MARCO (Valencia). ESTER DESFILIS answers:
Although it may seem strange, fish can smell and, actually, they have a very good sense of smell. Many people think that the sense of smell only detects volatile molecules and, therefore, it is not possible to smell inside water. However, smell has more to do with the sensory system involved (in this case, the olfactory system with the olfactory epithelium and their brain connections) than with the properties of the stimulus. Terrestrial animals detect volatile chemical substances with their olfactory system (or the vomerolfactory system, although that is another story) and dissolved chemicals using the sense of taste, but fish detect dissolved substances with both the taste and the smell senses. That is why, historically, fish were believed not to be able to smell. This was so until 1924, when Fritz Strieck demonstrated the olfactory capacities of the Common minnow, a species belonging to the same family of the fish in the picture. Ever since, many studies have been carried out which show the extraordinary olfactory sensitivity of fish.
Fish have one or two pairs of nostrils through which water flows into the nasal cavity. Inside the nasal cavity we find the olfactory epithelium with the sensory cells that detect the molecules dissolved in water. Most fish species have very sensitive olfactory receptors, capable of detecting the presence of molecules in very low concentrations.
Fish have one or two pairs of nostrils through which water flows into the nasal cavity. Inside the nasal cavity we find the olfactory epithelium with the sensory cells that detect the molecules dissolved in water. Most fish species have very sensitive olfactory receptors, capable of detecting the presence of molecules in very low concentrations.
What do fish use the sense of smell for? It depends on every species, but it has been proved that they use it for finding food (fact which fishermen take advantage of), finding a mate, recognising other fish of the same species, detecting predators, or for orientation (it seems that salmons recognise their birth river by smell). Recently, it has been proved that young fish from many coral reef species, if carried away by the currents, are capable of finding their way back to their birth reef by using their sense of smell. In this page you can learn a bit more about this.
Carps, like the one in the picture, have a very good sight, but also a good sense of smell. You can try and hide their food inside an opaque fabric bag and you will see by yourself how quickly they find it… only using their sense of smell.
Ester Desfilis. Professor at the Department of Psicobiology at The Complutense University (Madrid).
