Fish! didn't sell particularly well - not exactly due to the game's quality, but because of management troubles at Telecomsoft at that time (and it's label Rainbird on which Magnetic Scrolls published their games). Those troubles finally led to a sale of the publisher to Microprose UK. But during those final Telecomsoft months, no proper distribution was done according to Anita Sinclair, especially badly affecting Fish, and Magnetic Scrolls suffered some losses as a result.
All Magnetic Scrolls games (pre-Wonderland) are actually made up of a 68K CPU emulator and 68k data file. Their first game, The Pawn, was written for a Sinclair QL. Rather than re-write the game, they just wrote an interpreter (much like Infocoms famous Z-Machine) for each architecture (C64, Amiga, PC, Sinclair, etc).