Marine fish accumulate methylmercury (MeHg) to elevated concentrations, often higher than in freshwater systems. As a neurotoxic compound, high MeHg tissue concentrations could affect fish behavior which in turn could affect their populations. We examined the sublethal effects of MeHg on larvae of the Sheepshead minnow (Cyprinodon variegatus), an estuarine fish, using artificial or natural diets with varying MeHg concentrations (0 - 4.8 ppm). Larvae were fed control and MeHg-contaminated diets at low or normal (10% of their body mass) daily food rations from 7 - 29 days when they reached juvenile stage. Growth, respiration, swimming activity and prey capture ability were assessed. Food ration affected Hg toxicity in our study. Natural diets containing 3.2 ppm MeHg had no impacts on growth and swimming in fish that were fed normal food rations but depressed growth and swimming at low food rations. MeHg toxicity did not differ between artificial and natural foods, however fish accumulated more MeHg from the former. Artificial food containing 4.8 ppm MeHg only affected prey capture after 21 days of exposure. Sheepshead minnows, a forage fish species occupying a low trophic level in coastal waters, can be MeHg tolerant, especially when food is abundant, and can serve as an enriched Hg source for higher trophic level predators.

海鱼积累的甲基汞（MeHg）浓度升高，通常高于淡水系统。作为一种神经毒性化合物，高浓度的甲基汞组织可能影响鱼类的行为，进而影响其种群。我们研究了甲基汞对羊头min鱼幼虫（Cyprinodon variegatus）的亚致死作用），一种河口鱼，使用人工或天然饮食，且甲基汞浓度（0-4.8 ppm）各不相同。幼虫在进入幼年期后的7-29天以低或正常（占其体重的10％）的日常食物定量饲喂对照和受MeHg污染的饮食。评估生长，呼吸，游泳活动和猎物捕获能力。在我们的研究中，食物定量影响了汞的毒性。含有3.2 ppm MeHg的天然饮食对以正常食物定量饲喂的鱼的生长和游泳没有影响，但是以低食物定量饲喂的鱼的生长和游泳抑制了。人造食品和天然食品的MeHg毒性没有区别，但是鱼类从前者中积累了更多的MeHg。含有4.8 ppm MeHg的人造食品仅会在暴露21天后影响猎物的捕获。羊头小鱼，