Status of the stickleback species pair, Gasterosteus spp., in Paxton Lake, Texada Island, British Columbia

Abstract

A pair of threespine stickleback species (Gasterosteus spp.) coexists in Paxton Lake on Texada Island, British Columbia. One species (referred to as "limnetic") forages on pelagic zooplankton, and the other (referred to as "benthic") feeds on littoral zone benthic invertebrates. The morphology of each species reflects divergent resource use strategies. For example, benthics are larger, have wider mouths and fewer, shorter gill rakers than limnetics. Benthics also have considerably less armour than limnetics. Current data suggest Paxton Lake limnetics and benthics are unique biological species. Although both species are numerous, their entire distribution is restricted to this single lake. The immediate threat to these stickleback species is the unauthorized introduction of a non-native predator such as catfish (Ameirus nebulosus) or Pumpkinseed (Lepomis gibbosus).