tailieunhanh - Lake Trout Ecosystems in a Changing Environment - Chapter 16

Giám sát nhà nước của các hồ cá hồi tài nguyên: một cách tiếp cận cảnh quan Hồ nghèo dinh dưỡng . nên được công nhận cho những gì họ đang có, hồ bơi chạm khắc đá granite, với các nhánh sông thấp chất dinh dưỡng và chế độ nhiệt lạnh hàng năm. | chapter sixteen Monitoring the state of the lake trout resource a landscape approach Nigel P. Lester Ontario Ministry of Natural Resources Warren I. Dunlop Ontario Ministry of Natural Resources Contents Introduction Evaluating the state of a lake trout population Criteria and indicators Lake trout abundance Angling CUE Mortality rate Angling effort Rapid assessment methods Mark-recapture estimates of lake trout abundance Index fishing CUE Angling CUE Mortality rate Angling effort Elements of a landscape-level monitoring program Selecting lakes Measuring state of the resource from a sample of lakes Selecting a sample of lakes Sampling through time Discussion Acknowledgments References 2004 by CRC Press LLC Introduction Oligotrophic lakes . should be recognized for what they are swimming pools carved out of granite with low nutrient tributaries and a cold annual thermal regime. They are capable of having their environment and their communities severely altered only too easily. Unless further increases of eutrophication and exploitation are brought to a halt the lakes will be altered within the next three decades and their demise as producers of salmonid stocks may be irrevocable. Ryder and Johnson 1972 p. 948 Thus spoke the prophets 30 years ago. Were they correct Have oligotrophic lakes been seriously eroded by human-induced stress The anecdotal evidence is overwhelming indicating that lake trout Salvelinus namaycush populations in many lakes have been seriously degraded Evans and Willox 1991 Evans et al. 1991a 1991b 1996 . The extent of the damage however cannot be assessed objectively because the required data are not available. Much of our lake trout data come from case studies instigated in response to a perceived problem. Such data have enhanced our understanding of the stressors that impact lake trout but they are not very useful in addressing questions about the overall condition of the lake trout resource. What is the current state of the resource How many .