For the most part, I think you have the proportions of the initial body down, but some of the minor details need some work. What I noticed most was the muzzle, legs/paws, and tail that needs some practice. If you cannot read the text, dont worry, I'll type it here.
Some subjects on the head. The muzzle is a little too long, and usually is shorter than that unless you have an original species dog/wolf or something. Where the forehead meets the muzzle isn't very steep, and the forehead isn't very round, so it would be wise to make some sharper edges. The muzzle also isn't completely strait, from the nose to the lower lip, it make steps down so the nose is the furthest out. The ears also tend to be rounder and meatier, and aren't exactly on the back of the neck (that would be uncomfortable)
With the legs/paws, I see the joints lack definition and are as well have alot of curve, when in reality they are alot more edgy when they are bent (the only time you see more curves is when they are standing exeedingly strait). About the joints, I would be best to try and define the elbow, wrist, and shouler more, and make the paws bigger.
You also need some fur, this gives it a nice look and also helps define the tail seperation when you draw the fur and scales meeting at that point. I also noticed your tail seems a bit thin. Fish tails don't get very thin and stay about the same width throughout it's length. They need alot of muscle to help propel themselves through the water. The fins are rather nice as they are, in fact, there are all kinds of fins, round, veil, split, crowntails, etc. But I find with these kind of tails it's more interesting to put deeper curves in them, it's more appealing to the eye.
Lastly, I started with a sketch, the circles I would note the most. They help me define where everything should go and how it is proportioned. Which needed very little tweeking, as you had pretty good body proportion. Sketches are important because they allow you to tweek everything as needed and you can change things easier when you are linearting ontop of it. I as well added some scales to the tail just to define what it was and made the fur lighter through the shoulder fins. I also drew part of the back shoulder fin, because it is there and we dont want to forget about it.
All in all, I hope this helps you somewhat. Feel free to pm me if you want to ask me anything.




