[MUSIC] Organisms living in mountain lakes experience different environmental conditions relative to those living on land. For example, water has a high specific heat capacity relative to air, which means that aquatic environments lose and gain heat less rapidly. As a result, temperature extremes are less pronounced in aquatic, compared with adjacent terrestrial habitats. However, cold water and sediment that originates from glaciers, as well as extended seasonal ice cover ultimately limit the primary productivity in many mountain lakes. Mountain lakes are also different from lower elevation systems because most are naturally fish-less. In the absence of large fish predators, mountain lake ecosystems are dominated by large, often endemic, zooplankton. Many of these zooplankton species have bright red or black pigments that protect them from high ultraviolet radiation. Most of the lakes in the mountain national parks in Canada were fish-less before 1900. A survey of 1,464 lakes in Jasper, Banff, Yoho, Waterton, Revelstoke and Glacier National Parks found that over 95% of the lakes did not contain fish until they were stocked in the 20th century. The few that did support natural fish populations contained simple communities of only one to four species. Depending on the size, altitude and exposure of the lake. Bull trout was once the most widespread native trout in the mountain parks. They were part of the char family, which includes brook trout and lake trout. Bull trout require water temperatures generally below 13 degrees Celsius, as well as clean gravel beds, deep pools, and large systems of interconnected water ways to accommodate spawning migrations. So bull trout favor the deep pools of cold lakes and large rivers as well as high cold mountain headwaters. In recent times, bull trout has disappeared from much of its former range. This decline is the result of damaged habitat, overfishing, and the introduction of fish species, which have displaced it. During the last century, Rocky Mountain lakes were extensively stocked with sport fish to promote recreational fishing. Fish that were introduced into previously fish-less lakes had large effects on their ecosystems. These introduced fish rapidly consumed large, conspicuous zooplankton and tadpoles contributing to the loss of over 90% of mountain yellow-legged frog populations. And they also had a large impact on native fish populations. Let's talk about Lake Minnewanka and how Parks Canada manages fish and freshwater ecosystems in mountain national parks. The park's ecologists are world leaders in monitoring and protecting water quality in the headwaters of many of Alberta's mountain rivers. And continue to pioneer the science of aquatic non-native species management. The park is also home to some of the last remaining native populations of pure bull trout. Lake Minnewanka was stocked with fish from 1901 to 1972. It's estimated that over 17 million eggs and fry of lake trout, Atlantic salmon, cisco, brook trout, cutthroat trout, smallmouth bass, lake whitefish, and rainbow trout were introduced into the lake. Studies are now being conducted on the long-term effect that stocking and angling had on the overall health of these aquatic ecosystems. So I'm here again with Mark Taylor, an aquatic ecologist in Banff National Park. Where are we, Mark? >> Well we're on the marsh boardwalk at the lower Cave and Basin. And what I want to show you today, David, over here, is just one example of one of the non-native species that we've got here in the national park. >> Okay, let's go take a look. So Mark, which species of fish have been introduced into Banff National Park? >> Well, there's been a number of fish introduced to Banff National Park, David. Some of them being non-native, and also some native species. One of the examples of a non-native species is actually the mosquito fish, which you can see here in this warm marsh. They were introduced a long time ago deliberately for the purpose of mosquito control. And again, that was occurring all over the world. What we know now is they're really not that effective at mosquito control, and they do have an impact on the ecosystem. For example, one of the, mosquito fish are partially responsible for the extinction of the Banff longnose dace. >> And of course there is larger species that have been introduced as well, for anglers, in the past. >> Yeah, also going back to the turn of the century, there was an interest in really providing those recreational angling experiences for the park visitors. Less, obviously, thought was put into conservation. A lot of the species that were introduced were things that were familiar to people from back home in eastern Canada. So the eastern brook trout, for example, was introduced widely across the park, and also rainbow trout. Those are the two predominant non-native species. >> Right, and which species are of greatest conservation concern in Banff right now? >> Well, as far as native species, there's a lot of management focus put on to westslope cutthroat trout. They were legally listed by Canada's National Species At Risk Act. And Parks Canada is legally mandated to develop a recovery strategy and action plan. And we are currently working through those actions that will hopefully take us to a point where we can recover the westslope cutthroat trout, and actually take it right off of the Species At Risk Act. >> How soon do you think that can happen? >> It's not going to happen overnight, so we're inching way towards our goal. Part of that is going in and actively removing some of these non-native species from lakes where they threaten a downstream population of native species. We want to basically prevent the propagation of the non-native genes downstream, and stop hybridization with our native species. >> Mark, I want to thank you very much for coming and telling us about this. >> No problem, David. I enjoy it. >> Okay, thank you. And that brings us to the end of this lesson. Up next, Matt Peter is back with some useful tips on cooking in the back country. Good luck on your end of lesson quiz. And we'll see you next time, when we'll examine the various ways that mountains are both used and protected.
