Reproductive Abnormalities in Trout from Western U.S. National Parks

Abstract

AbstractReproductive disruption is well documented in polluted areas, such as below sewage treatment plants, but not in ecologically protected environments, such as national parks. In a majority of subalpine lakes sampled in Rocky Mountain and Glacier National parks, we observed intersex male cutthroat trout Oncorhynchus clarkii and brook trout Salvelinus fontinalis at frequencies of 9‐33%. Intersexuality, one form of reproductive disruption, is the presence of both male and female reproductive structures in the same animal. Male cutthroat trout, rainbow trout O. mykiss, and brook trout from these parks also produced elevated levels of the estrogen‐responsive protein vitellogenin, another indicator of reproductive disruption. We did not find reproductive abnormalities in national parks of the Sierra Nevada, Cascades, Olympics, Brooks, or Alaska ranges. To determine whether gonad abnormalities were evident in mountain ecosystems before the production of organic pollutants, we sampled various species of the family Salmonidae collected from the preorganic pollutant era (pre‐1930s). In these museum collections, we observed intersex male greenback cutthroat trout O. clarkii stomias collected in the late 1800s from Twin Lakes, Colorado, in the Rocky Mountains. Our current results suggest that reproductive disruption is occurring in some national parks. The abnormalities were observed in remote, high‐elevation locations, suggesting that they might have resulted from airborne contaminants. Our observation of intersex greenback cutthroat trout from the late 1800s suggests that organic pollutants are not the only factors inducing reproductive disruption. The causes and population‐level consequences of reproductive disruption in these lakes remain to be determined.