An isolated population of fourhorn sculpins (Myoxocephalus quadricornis, family Cottidae) in a hypersaline high arctic Canadian lake

✍ Scribed by Mike Dickman

• Publisher: Springer
• Year: 1995
• Tongue: English
• Weight: 806 KB
• Volume: 312
• Category: Article
• ISSN: 1573-5141
• DOI: 10.1007/bf00018884

✦ Synopsis

Freshwater sculpins probably evolved from marine ancestors which entered bodies of water such as proglacial lakes or lakes which were gradually isolated from the sea by isostatic rebound . Sculpins in fresh water lakes (Myoxocephalus thompsoni [Girard]) lack cephalic horns and live well below a depth of 10 m . Those in the sea (Myoxocephalus quadricornis [Linnaeus]) typically live above 10 m and possess a well developed set of four cephalic horns . The sculpins in Garrow Lake, North West Territories, are intermediate between the marine and fresh water forms with respect to their depth distributions and their cephalic horns (spines) . As a consequence, Garrow Lake, which separated from the sea some 3000 years ago, serves as an excellent `laboratory' for studying evolutionary changes in this sculpin . The age of the lake was based on carbon-14 dates of the fossil pelecypods from raised beaches around the lake and from observations of rates of isostatic rebound in the area as reported by Dickman &Ouellet 1983 andPage et al. 1984 . During the last 3000 years, the surface waters of Garrow Lake have freshened and its sculpins have apparently adapted to this top down freshening by occupying a depth where the salinity of the lake approaches that of sea water. As a result, the sculpin population in Garrow Lake lives deeper than the sculpin population in the nearby Garrow Bay . Thus, the deeper dwelling Garrow Lake sculpins appear to be less vulnerable to avian predation than their shallow water dwelling marine ancestors . It is hypothesized that reduced avian predation of the Garrow Lake sculpin population is associated with the observed reduction in their cephalic horns which impart a certain degree of disruptive colouration and disruptive pattern outline allowing the shallow dwelling marine species to blend in with its background in a manner which appears to make it less visible to avian predators .

It is unfortunate that the three thousand year old Garrow Lake sculpin population is now endangered by mine tailings entering the lake from the nearby Cominco Ltd . mine. The entire food chain of the lake appears to have been severely impacted by lead and zinc mine tailings entering Garrow Lake at a rate of 100 metric tonnes per hour .