Pheromone signalling in conservation

In freshwater ecosystems, non-indigenous species (NIS) are the most significant threat to biodiversity (Sala et al., 2000). Despite efforts to control the entry of invading species into countries (e.g. V! as! arhelyi and Thomas, 2003), there are relatively few practices in place to control established aquatic invasive species without affecting non-target species or causing environmental damage. Pheromones have been used successfully to control terrestrial insect pests that rely on chemical cues to synchronize behaviours without adverse changes to the environment (Payne et al., 1986). I suggest that this strategy used to control terrestrial insects be applied to protect aquatic indigenous species threatened by invaders. All animals are ‘leaky bags’ with odours being released from skin, gills, lungs, faeces and urine (Atema, 1996). Just as ornaments or elaborate displays are used by individuals to enhance their mating success, odours represent a strong signal to females and males in sexual selection (Wyatt, 2003). Odour as a cue for males to attract females was recognized by Darwin (1874), who described the strong odours of reproductive male elephants, goats and deer. Historically, commercial fishers often deployed caged reproductive male lampreys to attract females, resulting in abundant catches (Fontaine, 1938). This idea of using pheromones from one sex to attract members of the opposite sex during the breeding season could result in a shift in the operational sex ratio of a species, resulting in severe competition for mates. Since Doving (1976) suggested that fish may have evolved to release hormones as sex pheromones, researchers have shown that pheromones produced in the final stages of maturation function in the synchronization of mating in many fish. Examples include studies on Petromyzontiformes (sea lamprey, Petromyzon marinus (Li et al., 2002)), Cypriniformes (e.g. goldfish, Carassius auratus (Sorensen and Stacey, 1999)), Siluriformes (African catfish, Clarias gariepinus (Van den Hurk and Resink, 1992)), Salmoniformes (e.g. Atlantic salmon, Salmo salar (Waring and Moore, 1997); brook trout (Young et al., 2003)) and Perciformes (round gobies (Murphy et al., 2001; Belanger, 2002)). It is the application of pheromone signalling in the control of NIS to enhance the conservation of native freshwater species that I wish to address. I will provide examples of two NIS (P. marinus and round goby, Neogobius melanostomus) that exhibit detrimental effects on native fish in the Laurentian Great Lakes. The