How big of a problem is trout entrainment in Montana and what are the ecological consequences?
JZ: The entrainment problem in Montana is both substantial and complicated. Very few diversions have been studied to quantify seasonal entrainment problems, but, of those that have, analysis indicates several thousand trout (and tens of thousands of other fish species) per season are entrained by each diversion, and there are almost 180 thousand known diversions in Montana. The math indicates that hundreds of thousands of trout (and much larger numbers of other fish species) are entrained each year and consequently lost to reproducing populations. The complications arise from having big introduced populations of trout (mostly rainbows, browns and brook trout) in Montana watersheds for over a century. These non-natives now are self-reproducing (as opposed to being regularly stocked), and apparently suffer little harm at the population level from entrainment, despite the large annual losses, as is indicated by regular population surveys. Many of the wild trout entrained annually in Monta
