The Fish Merchant may be the painting Selling Fish, exhibited at the Scottish Academy in 1829. 

Walter Geikie RSA, 1795-1837

Born in Edinburgh, Geikie trained at the city's Trustee's Academy under John Graham. His reputation rests on his etchings, powerful in their simplicity. He was an accomplished draughtsman and an acute observer of character. Geikie was struck deaf and dumb at the age of two, and no doubt the affliction heightened his awareness and sensitivity. His portrayals of life in Edinburgh and at country markers and fairs, drawn on the spot, are full of humour but without an sentimentality or satire. He drew inspiration from Rembrandt, the Scottish artist David Deuchar and especially the early paintings of David Wilkie, although he was no imitator.Geikie was less happy working in oil, probably owing to an eye defect that may have been a form of colour blindness.