Ecology of Galaxias platei in a depauperate lake

Abstract

Galaxias platei is widespread and common in southern South America, but its ecology is poorly documented relative to other native species, especially those of commercial importance. Galaxias platei occurs across a large range of environmental conditions, including hydrologically isolated, high‐elevation lakes. Consequently, there were several lakes in the Patagonian region where it was the only native fish species. Introduction of salmonids into almost all lakes in Patagonia where G. platei occurs has potentially resulted in changes in its ecology and behaviour. Thompson Lake is a small, high‐elevation lake located in the Aysen River basin (Chile) where G. platei still occurs essentially in isolation. We collected G. platei from this lake to characterise the ecology of the species in the absence of other native and introduced fishes. We documented age and growth patterns from otolith analysis and characterised size‐ and age‐specific habitat use, diet and trophic niche. In Thompson Lake, G. platei is long‐lived and grows to comparatively large size (max. age = 18 years; max. TL = 348 mm). As it grows, it exhibits an ontogenetic niche shift in habitat use, diet and trophic niche. Large adults are piscivorous, and they occupy deep benthic habitats. Preservation of the last few remaining lakes where G. platei is found in isolation is an important priority for maintaining the full expression of ontogenetic niche variation in this species.

Trophic scaling of Percichthys trucha (Percichthyidae) in monospecific and multispecific lakes in western Patagonia

“…This suggests that adults of P. trucha do not recognise conspecific juveniles as potential prey. This finding is contrasting with recent studies from other monospecific lake in Patagonia inhabited by galaxiid G. platei (Thompson lake, Aysen River Basin), where rapid ontogenetic trophic scaling was found in early developmental stages due to cannibalism (Belk et al, 2014). Populations of P. trucha inhabiting these small lakes (Silvia and Maldonado) seem to represent a different dynamic, more similar to stunted populations (sensu Ylikarjula et al, 1999).…”

“…Trophic ecology of P. trucha is still less understood in lakes of western Patagonia. In many of these lakes, G. platei has been described as the native top predator Belk et al, 2014) and its trophic scaling was reported as it shifts from zooplanktivory at small sizes to cannibalistic piscivory at larger sizes (Belk et al, 2014).…”

Echoes of a distant time: effects of historical processes on contemporary genetic patterns in Galaxias platei in Patagonia

“…Eggs are thus unlikely to be dispersed across lakes. Larvae generally reside in the limnetic zones, and adults are generally found most abundantly near the benthos from where they move into shallow areas to feed on macroinvertebrates, eggs and small fish, including G. platei individuals (Barriga et al 2002;Belk et al 2014). The IBD pattern we have observed in G. platei is thus most likely explained by a process of isolation by dispersal limitation (IBDL, Orsini et al 2013).…”

“…; Belk et al . ). The IBD pattern we have observed in G. platei is thus most likely explained by a process of isolation by dispersal limitation (IBDL, Orsini et al .…”

“…Fish were collected with seine nets and gill nets and by electrofishing and stored in 95% ethanol. The combination of collection methods ensured representation from a range of sizes and thus presumably cohorts (Belk et al 2014). A total of 363 individuals were collected from five lakes in the San Pedro system ( Table 1), two of these lakes were located above a dam (Pullinque and Pellaifa; Fig.…”