Like Bailiwan, the start of your Larano map looks very sharp Robb75067. Are you sure your canals and basins are only meant to serve fishing and small coastal boats? Just looking at your map, it looks like Larano has a serious naval fleet going--because they have the infrastructure (canals, drydocks, etc.) for it.
Although it's not exactly in the medieval period, your canals and drydocks/basins are very reminiscent of the east end of 17th and 18th century London in the heyday of the Royal navy. A superb map to get an idea of what I'm talking about is the 1827 Greenwood map found at http://users.bathspa.ac.uk/greenwood/imagemap.html. You can zoom in to see the turning basins and drydocks on the east side of the city.
As for width, checking the old 'net' shows that John Cabot's boat (the one he sailed to America in in 1497) was about 20 feet wide and 64 feet long. Two centuries later, Peter the Great had a frigate constructed called the Standart, which was 22 feet wide and 108 feet long. Although not in the medieval period, the HMS Victory was 227 feet long and close to 52 feet wide. I'd say your canals should be about 50-60 feet wide, which would enable two of the larger vessels (like the Standart) to pass each other.
Unless you've got some kind of anachronistic Nelsonian "fighting sail" campaign going on, most of your ships will be smaller than either Cabot's or the Standart. Look up the dimensions for a cog if you can find one. That was a type of ship heavily used until the 14th century. Most of what we think of sailing ships were not developed until the 15th/16th through 19th centuries.
The housing density of your city is likely to be quite high. I do not know how dangerous the lands outside the walls around Larano are, but medieval cities used to be very thickly packed as the citizenry were trying to take advantage of the safety inside the city walls. Given the canals and the high density of your city, its possible that the citizens may have built up like residents did in medieval and Renaissance Amsterdam (you can see a picture of this kind of vertical construction at http://en.wikipedia.org/wiki/Image:K...tAmsterdam.jpg).
When it comes to designing your city, make sure you keep the market or markets near the docks. Although farmers will be bringing produce in, I suspect that a city as maritime oriented as Larano will have its main market near the docks to facilitate easy transport of fish and other goods. Also make sure that you have plenty of warehouses near the water. The kind of commerce needed to sustain a major city like yours would require some serious storage space.
Just out of curiousity, how large is your city? 30-50k was very large for the middle ages. If Larano is that size, it may have more than one market.
Also, make sure there are forts and towers to cover not only the wall on the land side, but also cover the sea approaches with ballistas and catapults. Given the importance of the sea to the city, the powers that be would want to protect it from pirate raids and attacks from hostile governments.
I don't know if your city is sophisticated enough to have a sewer system (many cities in the middle ages did not--one reason plagues and diseases would ravage them every so oftem). If it does, it will probably drain into the bay. I would make sure that there are iron grates to prevent sahaugin, thieves, and other nefarious characters from using them (which of course never works either to keep out said nefarious characters or adventurers in a fantasy campaign ).
Last, I don't know what the law level is in Larano, but unless it's some kind of draconian military dictatorship, there is likely to be some level of smuggling/illicit activity. Although not necessarily showing up on a map, that means there are likely to be houses and warehouses with secret passages/smuggling tunnels etc.
Hope I've given you some type of starting point Robb75067. You are off to a good start, I'm curious to see how your map turns out.