title: Combined effects of flow condition and parasitism on shoaling behaviour of female guppiesPoecilia reticulata.
abstract: Group living in fish can provide benefits of protection from predators and some parasites, more efficient foraging for food, increased mating opportunities and enhanced energetic benefit when swimming. For riverine species, shoaling behaviour can be influenced by various environmental stressors, yet little is known how flow rate might influence the shoaling of diseased fish shoals. In view of the increasingly unpredictable flow rates in streams and rivers, this study aimed to assess the combined effect of flow condition and parasitism on the shoaling behaviour of a model fish species. Shoal size, shoal cohesion and time spent shoaling of female guppiesPoecilia reticulatawere compared when infected with the directly transmitted ectoparasiteGyrodactylus turnbulliunder flow and static conditions. Flow condition was an important factor in influencing shoaling behaviour of guppies with the fish forming larger shoals in the absence of flow. When a shoal member was infected withG. turnbulli, shoal cohesion was reduced, but the magnitude of this effect was dependent on flow condition. In both flow and static conditions, bigger fish formed larger shoals than smaller counterparts. Future changes to stream hydrology with more frequent flooding and drought events will affect the shoaling tendency of fish. During high-flow events, diseased fish may not be able to keep up with shoal mates and therefore have a higher risk of predation. Additionally, these findings may be important for aquaria and farmed species where an increase in flow rate may reduce aggregation in fish.
authors.affiliation: School of Biosciences, Cardiff University, Cardiff, UK.
authors.forename: F A
authors.initials: FA
authors.lastname: Hockley
authors.affiliation: Hydro-environmental Research Centre, School of Engineering, Cardiff University, Cardiff, UK.
authors.forename: C A M E
authors.initials: CA
authors.lastname: Wilson
authors.affiliation: School of Biosciences, Cardiff University, Cardiff, UK.
authors.forename: N
authors.initials: N
authors.lastname: Graham
authors.affiliation: School of Biosciences, Cardiff University, Cardiff, UK.
authors.forename: J
authors.initials: J
authors.lastname: Cable
keywords: Cohesion; Flow rate; Flume; Nearest neighbour distance; Shoal size; Social groups