Do you need a fishing license to fish? I know it's only necessary in fresh water, but I'm not clear on whether this is freshwater since it's connected to the Maurice River.

Yes, you need a current Freshwater Fishing license to fish there. The $ spent on licenses goes back to buying, maintaining and enforcement of areas like this. The annual Freshwater Fishing Digest (free w/ license purchase) lists every river and stream in the state that eventually flows into saltwater and clarifies what portion of the waterbody is freshwater and what is salt.

Yes you do need a fishing license. All rivers, lakes and ponds in NJ are freshwater. Only the ocean, and inlets along the coast do not need a freshwater license. But you do need to sign up with the saltwater registry, it's free but required.