The high level of mercury in pinebarrrens chain pickerel have significantly reduced my consumption of the fish. I used to always eat my sizable catches but I have since had to change my ways due to this health concern.
The fact is the bass and pickerel in the pine barrens have higher mercury levels than other parts of the state (as you mentioned) the reason is somewhat speculative. Mercury contamination can occur from a point source, like a factory or lawn pollutants, but can also be transmitted through the atmostphere. Atmostpheric transmission of mercury is most likely the cause behind pine barren contamination. Nothern, industrial NJ, is more likely a point source and atmostpheric combination.
The theory as to why mercury is higher in the pine barrens is based on two factors. 1) the chemistry of the water in the pine barrens is more condusive to store high levels of mercury. 2) the food source of the pickerel and bass contain higher levels of mercury...sunfish to the north (blue gill and pumkin seeds) grow larger than pinebarrens sunfish varieties (blackbanded, spahgum, blue spotted). The older the fish, the greater the levels of mercury since mercury levels are cumlative and don't degenerate. The northern variety of sunfish, by the time they reach, say, 3 years old are too large for many game fish. But in the pinebarren variety sunfish, at 3 years old they are still relatively small and prime fish for consumption by pickerel and bass. Not to mention, pinebarren chainsides are real bad asses and will eat fish nearly a 3rd their own size. So our game fish our consuming older fish, which contain more mercury due to their age. So consequently our game fish have higher mercury levels.
Hope this wasn't too boring.
Jeff