Total mercury concentrations of brook trout in Pennsylvania streams

Brook trout are widely distributed in Pennsylvania’s forested headwater streams where acidic conditions and wetlands can cause mercury to be more bioavailable.  The purpose of our study was to determine mercury concentrations in brook trout collected from small streams and identify relationships with a number of variables associated with mercury accumulation in fish tissue.  A sample of five brook trout of similar length was collected from 62 small streams located primarily in northcentral Pennsylvania.  Brook trout mean length varied by stream and ranged from 134 mm to 214 mm.  A composite fillet sample from each stream was analyzed for total mercury (tHg).  The tHg concentrations varied from 0.02 to 0.13 ug/g, with a mean of 0.06 ug/g.  Land cover assessment suggests that watersheds with a higher percentage of forested wetlands have the strongest relationship with brook trout tHg.  Streams with the highest tHg concentrations in brook trout were outside the targeted study area and the sample size was insufficient to determine whether there were regional differences in tHg concentrations.  Additional sampling will be necessary to determine if there are regional differences in tHg concentrations of brook trout in Pennsylvania.