tailieunhanh - Lake Trout Ecosystems in a Changing Environment - Chapter 6

Hồ cá hồi (Salvelinus namaycush) khối lượng môi trường sống và ranh giới trong hồ Lá chắn Canada Hồ cá hồi Salvelinus namaycush dân số thường yêu cầu số lượng lớn của nước lạnh, welloxygenated để phát triển mạnh (Martin và Olver, 1980), do đó, ranh giới tối ưu môi trường sống của họ đã được xác định bởi nhiệt độ thấp hơn 10οC và nồng độ oxy lớn hơn 6 mg / L (Evans và cộng sự, 1991). Oxy và nhiệt độ tiêu chuẩn đã được sử dụng để xác định các lớp học khác của hồ cá hồi môi. | chapter six Lake trout Salvelinus namaycush habitat volumes and boundaries in Canadian Shield lakes Bev J. Clark Dorset Environmental Science Centre Ontario Ministry of the Environment Peter J. Dillon Environmental and Resource Studies Trent University Lewis A. Molot Faculty of Environmental Studies York University Contents Introduction Habitat volume Volume-weighted habitat Estimating habitat boundaries Effects of external stresses on habitat volume References Introduction Lake trout Salvelinus namaycush populations generally require large volumes of cold well-oxygenated water to thrive Martin and Olver 1980 thus their optimal habitat boundaries have been defined by temperatures of less than 10OC and by oxygen concentrations greater than 6 mg L Evans et al. 1991 . Oxygen and temperature criteria have been used to define other classes of lake trout habitat for example Evans et al. 1991 defined a usable habitat as one with O2 4 mg L and temperature 15OC. There is increasing evidence that some populations can be successful at higher temperatures under some circumstances Snucins and Gunn 1995 but in most cases examining the potential for success or failure of lake trout populations requires as a minimum a measurement of suitable habitat volumes for the lakes in question Christie and Regier 1988 MacLean et al. 1990 Evans et al. 1991 . Because these boundaries are measured easily using portable field equipment temperature oxygen meters they present a relatively simple means of assessing habitat suitability. 2004 by CRC Press LLC Habitat volume Lake trout habitat volumes are at their minimum each year immediately before the time when surface waters have cooled enough to 15OC to be usable. This occurs before thermal destratification in the fall. At this time oxygen concentrations in the hypolimnion will be at their minimum and the depth of the metalimnion as well as the depth of the 10OC isotherm Z10 will be at their greatest. These dates are determined each year by the .