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There are a few otters in New Jersey. In fact, Fish & Wildlife has a season for trapping otters:
http://www.state.nj.us/dep/fgw/pdf/2...ott_regs16.pdf
I often see mink dashing about the shoreline of the South Branch, but I haven't seen any otters.
The only otter I ever saw in New Jersey was in the Great Swamp - which is the headwaters of the Passaic.
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