There are only 2 ramps in to the upper part of the Nashua river that i know can be used by the general public, There are some others , behind Jensons mobile park and the golf course area Hollis Lone Pine Hunting / Fishing club, but all is private from what i understand. you can see them from the water , but i have not looked into using them.
Mostly Largemouth but smallies too. and big pickerel in the upper part Lots of Horn pout night fishing, and big ones.
For the Nashua river there are a few spots.
For the upper part of the Nashua river --- Stellos Staduim also called Mines Falls up thru Hollis you can put in right at Stellos opposite the new YMCA, excellent paved launch for big or small with plenty of parking with less than a minute walk.
Also off Broad street to Tilton street, both excellent launch areas, If you are at the Tilton street ramp and looking into the water there is a pipe to the left that is under water, You an see it. Just dont drop a trailer tire over it. Plenty plenty of room except far left.
You could easily put an extra wide party boat in at either launch
1 ramp on each side of the river, as the crow flies or boats travel the ramps are very close to each other, Driving from on to the other is 15 - 20 minutes depending on traffic.
Smallmouth bass lower part some Largemouth , some big pickerel too.
For the lower part of the Nashua river Below the dam at Stellos or Mines Falls to the Jackson falls dam on Main street There are some places to put a canoe off of Franklin street , and an excellent ramp off Technology way, behind clock tower place. The ramp is posted , Written permission needed. I have a permit, basically it is a waiver. I used the ramp many times with out written permission before they left a note on my truck saying to please call the # so you can get permission. Then display it in your window. From that launch you can go left or right. right takes you to Main st area to above Margarittas, left takes you to the Nashua mall area under the highway and just keep going, it gets rocky way up past Home depot. Going left is against the current and will take you better than1/2 hour with a trolling to get to home depot area, Make sure you fish the bridge that goes over the highway well ,Fish is close to the bottom , i have had good luck with heavy weighted craws and jigs as well as heavy spinner. there are some good fish there. the current is strong , bring 2 anchors as the current will drag you.
After the Jackson falls dam i do not have a good launch area for even a canoe , from the Jackson falls area behind Margarittas it flows to the Merrimack river at the Hudson bridge. I fish this area where they meet. But get to it from the Merrimack or down a steep hill behind M/N Sports and way in back of those building.
Down that hill is a 2 person operation unless you have a wicked light canoe, kayak or winch type set up or are the size of Hulk to carry it back up,
The Merrimack river is flowing very fast and is real high right now, if i was going to fish this area with a canoe i would carry it down the hill behind the skate park way in back and fish this area where the 2 rivers come together, hard fighting smallies along this complete area. lots of rocks and very good shore cover. you will lose some jigs here. Hula popper to the edges.
Then there is the Merrimack river launch off Hillsferry road, they just pulled a truck / trailer / boat set from the water last week as the current is so fast right now, very steep ramp. I use it with my f-150 but i only have a small jon boat. Just be careful if you use it right now, After the water drops and slows it should not be a problem for most.