Salmon movement in Western Brook part 1: adult transit through temperature extremes created by the coastal plain and fjord lake

Western Brook Pond (WBP) is a large ultra-oligotrophic lake. Western Brook became part of Gros Morne National Park in 1973 and a UNESCO World Heritage Site in 1987. Due to low numbers of fish, the Park closed it to angling in 1985. The Park counts the number of returning salmon once every 5 years, but much remains unknown about this special population.

The Western Brook watershed is one of extremes. At 165m deep, WBP contains a colossal amount of water that remains cold through the summer and has a residency time of  >15 yrs. Inflow primarily comes from cascading waterfalls that enter the gorge from the plateau 600m above (and are inaccessible to anadromous salmon), and two relatively small tributaries on the coastal lowlands (un-named and Stag Brook). The outflow (Western Brook) is atypical for a Newfoundland river as during its ~8.5km journey to the sea, it passes through several large and very shallow “steadies” that broil in the summer sun, and the water gets very warm very quickly as it flows.

How much of a thermal refuge WBP provides depends on when fish are in it. If they stay in the brook in summer, they may cook, despite the cold lake being just upstream. Whether increasing summer temperatures caused by climate change create acute problems in July/August thus depends on how quickly fish move into the lake and whether they stay there or enter tributaries.

Temperatures will be assessed in Western Brook, WBP and its two coastal plain tributaries. Fish passage from Western Brook into WBP, and the timing of when fish enter the tributaries will be determined. Movement data will provide information on the relative importance of the three potential spawning locations. Post-spawning movement of kelts will inform on where death occurs, where survivors spend the winter, and the timing of movement back to sea.

The backdrop provides a great stage to educate about Atlantic salmon, and the Park receives between 80,000-100,000 visitors per year. The capture and tagging of Atlantic salmon will occur adjacent to the Western Brook day-use picnic area. This will provide the opportunity to engage directly with the public while Dr. Purchase and his group are tagging salmon. This engagement will be further enhanced by advertising when the work will be occurring via a sandwich board at the entrance to the day-use area, direct communication with anglers who obtain salmon fishing licences at the Gros Morne Visitor centre, and a poster for communication with visitors (~20,000) to Memorial University’s Bonne Bay Aquarium and Research Station.