Asocial fish - Coming to a town near you!

A recent paper in the journal 'Proceedings of the Royal Society of London' by researchers at UCDavis have shown that asocial tendencies are crucial in the dispersal of biological invaders, and asocial individuals could lead the invasion front. Researchers investigated the mosquitofish, Gambusia affinis, a small freshwater fish that feeds on aquatic larvae and terrestrial insects trapped at the water surface. The Mosquitofish is identfied by the global invasive species database as one of the most invasive species worldwide invading over 40 countries.

In the study they measured the dispersal ability of different individuals within an artificial stream and compared this to the sociability of the individuals. Sociability was measured as the willingness to shoal. This study is unique in that it investigates within species variation in personality traits whereas most studies undertake comparisons between species.

Their results showed that the distance moved during a dispersal assay was strongly correlated with sociability. Asocial individuals were found to disperse further and more often. In addition, when these same trials were undertaken later the same fish showed similar behaviour indicating that these personality traits are consistent over time. This study highlights that differences in personality traits could have large implications in the invasive process.

This idea is not only restricted to fish. Bluebirds found at the invasion front were also shown to be the most aggressive among their peers. More surprisingly humans also show high dispersal characteristics when asocial personality traits are high. This doesn't bode well for our great discoverers such as Captain James Cook or Columbus. Or those people who colonised the British colonies or moved out west in the USA. Maybe thats why cowboys had such a chip on their shoulder. They really were asocial bastards!

Cote J, Fogarty S, Weinersmith K, Brodin T, Sih A (2010) Personality traits and dispersal tendency in the invasive mosquitofish (Gambusia affinis). Proceedings of the royal society of London: February 19.

Jokela M, Elovainio M, Kivima'ki M, Keltikangas-Ja"rvinen L (2008) Temperament and migration patterns in Finland. Psychological Science 19: 831-837