Status of the stickleback species pair, Gasterosteus spp., in Hadley Lake, Lasqueti Island, British Columbia

Abstract

Two species of threespine stickleback (Gasterosteus spp.) formerly inhabited Hadley Lake on Lasqueti Island, British Columbia, and are described briefly in this report. One species (referred to as "limnetic") was a pelagic zooplankton feeder, and the other (referred to as "benthic") exploited littoral zone benthic invertebrates. The species were unique British Columbia endemics restricted to this single lake. The species were first discovered in the late 1980s, but have recently become extinct following the unauthorized introduction of catfish (Ameirus nebulosus) to the lake. Independently evolved yet morphologically similar species pairs exist elsewhere on nearby islands. Measures should be taken, such as transplanting to inaccessible fishless lakes, to protect the remaining species pairs.