Ward Darren M, Nislow Keith H, Chen Celia Y, Folt Carol L
Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA.
Trans Am Fish Soc. 2010 Jan 1;139(1):1-10. doi: 10.1577/T09-032.1.
Mercury (Hg) is a potent toxin that biomagnifies in aquatic food webs. Large fish generally have higher Hg concentrations than small fish of the same species. However, models predict that fish that grow large faster should have lower Hg concentrations than small, slow-growing fish due to somatic growth dilution (SGD). We examined the relationship between Hg concentrations and growth rate in fish using a large-scale field experiment. Atlantic salmon (Salmo salar) fry hatched under uniform initial conditions were released at eighteen sites in natural streams, collected after one growing season, and Hg concentration and growth measured. As expected for Hg accumulation from food, mercury concentrations in salmon tracked Hg concentrations in their prey. Nonetheless, large, fast-growing salmon had lower Hg concentrations than small, slow-growing salmon, consistent with SGD. While prey Hg concentration accounted for 59% of the explained variation in salmon Hg concentration across sites, salmon growth rate accounted for 38% of the explained variation independent of prey Hg concentration. A mass-balance Hg accumulation model shows that such SGD occurs when fast growth is associated with high growth efficiency. Fish growth is tremendously variable and sensitive to anthropogenic impacts, so SGD of Hg has important implications for fisheries management.
汞（Hg）是一种强效毒素，会在水生食物网中生物放大。同一种类的大鱼通常比小鱼汞含量更高。然而，模型预测，由于躯体生长稀释（SGD），生长速度较快的大鱼汞含量应低于生长缓慢的小鱼。我们通过一项大规模野外实验研究了鱼类汞含量与生长速度之间的关系。在统一初始条件下孵化的大西洋鲑（Salmo salar）鱼苗被放流于18条天然溪流中的不同地点，在一个生长季节后进行收集，并测量汞含量和生长情况。正如从食物中积累汞的预期那样，鲑鱼体内的汞含量与它们猎物中的汞含量相关。尽管如此，生长迅速的大鱼汞含量低于生长缓慢的小鱼，这与躯体生长稀释相符。虽然猎物汞含量占各地点鲑鱼汞含量可解释变异的59%，但鲑鱼生长速度独立于猎物汞含量之外，占可解释变异的38%。一个质量平衡汞积累模型表明，当快速生长与高生长效率相关时，就会出现这种躯体生长稀释现象。鱼类生长变化极大且对人为影响敏感，因此汞的躯体生长稀释对渔业管理具有重要意义。
