A bit more rambling from me ...
That eBay item is of the same style as the eight massive examples I mentioned earlier, but is only half the size of those I saw. However, the size stated in the ebay listing is 4 inch x 4 inch but the images show that it is clearly taller than it is wide. The base is flat polished, whereas in a few examples I have seen, with the fish at the top of the weight and only viewable properly from the top view, the base had a deep concave polished central area. Some pople have suggested the deep concave basal area indicates Venini - but I can't confiorm or deny that. Unfortunately, I neglected to ask the owner of the eight massive ones to show me how the bases were finished!
The label on that eBay item is a generic Murano one (as far as I can make out the writing on it) and I believe it is the same label as
shown here in the GlassGallery - Murano Labels section. It was on
this paperweight that Lynne (Josordoni) showed, which has canes that I always get get confused about. Were those canes used in Fratelli Toso weights or AVEM or some other maker?.
The generic Murano label may well have been applied by an importer to items from several makers.
The eBay weight may be from Cenedese but I wonder whether lots of these are simply "based on a design by Licata" but not necessarily made by one of the 'greater masters'. The quality of the fish and the seaweed seems to differ widely across the ones I have seen.
So, in summary, I cannot attribute any of these types of fish weights accurately as I am still waiting to see or hear of any confirmed evidence of a specific maker for any of them.