Shorthead sculpin (Cottus confusus Bailey and Bond, 1963) in Birch Creek, Idaho, were infected with the trematode Euryhelmis cotti (Simon, 1972). Our objective was to determine if intensity of infection had an influence on growth, reproduction, and mortality of shorthead sculpin at two sites in Birch Creek. Prevalence of trematode infection was 100 % at the upstream site compared to 32 % prevalence at the downstream site; intensity of infection was at least 15 times greater in shorthead sculpin at the upstream site. von Bertalanffy growth models differed significantly between sites; the growth coefficient (K) was higher for sculpin at the upstream site. Gonadosomatic index for both males and females was significantly higher for sculpin found upstream. Females at the upstream site also had significantly more eggs per clutch compared to females at the downstream site. Annual mortality was significantly higher upstream (A = 57 %; 95 % CI = 52–62 %) compared to downstream (A = 42 %; 95 % CI = 38–46 %). Consequently, the density of sculpin was lower at the upstream site (13 fish/100 m²) compared to the downstream site (54 fish/100 m²). We did not find evidence to suggest that growth and reproduction of shorthead sculpin were influenced by infection of E. cotti, but rather were influenced primarily by density dependent factors. Mortality was higher for shorthead sculpin at the upstream site with high prevalence and intensity of infection. However, we do not know if higher mortality was a direct consequence of trematode infection or merely correlated with trematode infection.

爱达荷州伯奇克里克的短头s（Cottus confusus Bailey and Bond，1963年）感染了吸虫Euryhelmis cotti吸虫（Simon，1972年）。我们的目标是确定感染强度是否对桦木溪两个地方的短头的生长，繁殖和死亡率产生影响。吸虫感染的发生率在上游部位为100％，而下游部位为32％。在上游部位，短头s的感染强度至少高出15倍。von Bertalanffy的生长模型在不同地点之间存在显着差异。sculpin在上游部位的生长系数（K）较高。雄性和雌性的性腺体能指数明显高于上游发现的杜鹃。与下游站点的雌性相比，上游站点的雌性每个离合器的卵也明显多。上游的年死亡率显着更高（A = 57％；95％CI = 52–62％），而下游（A = 42％； 95％CI = 38–46％）。因此，在上游位置的cul鱼密度较低（13条鱼/ 100 m²）与下游站点相比（54条鱼/ 100 m ²）。我们没有发现证据表明短头s的生长和繁殖受大肠杆菌感染的影响，而主要受密度依赖性因素的影响。上游部位的短头鱼的死亡率较高，感染率和感染强度都很高。但是，我们不知道更高的死亡率是吸虫感染的直接结果还是仅与吸虫感染有关。