The sex and death pondered in this delightful collection of essays on fly-fishing is that of the mayfly (Ephemeridae). Mayflies and other insects valorously offer themselves up in swarms to hungry trout. Figuring out where and when, and precisely duplicating their tiny bodies and imitating their movements, are key elements in the sport-cum-passion that is fly-fishing. ""Those who don't fish,"" writes Gierach, ""see those of us who do as harmlessly strange and sort of amusing. . .[that] might be a fair assessment."" His pursuit of rainbows, browns, Dolly Vardens, graylings, cutthroats and bass takes him from the St. Vrain River near his home in Colorado to Utah, Wyoming, Montana, Idaho, and British Columbia. He's not really after trophies and only rarely keeps any of the Fish to eat. He calls the sport a ""profound relaxation"" that is most meaningful because it ""has no practical reasons attached to it,"" somewhat like ""sex with careful birth control."" Chapters such as ""Guiding and Being Guided,"" ""The Less-Loved Fishes,"" and ""Bass Fishing by the Numbers"" are so wonderfully infused with Gierach's wry humor that the nuts-and, bolts technical matters go down quite smoothly. Another, his admiring pastiche of Garrison Keillor (""It has been 'A Quiet Week' in East Big Fish""), is a charming piece of work. In these smooth and often personal essays, Gierach brings to the old-fashioned fish story something that borders on art.