A 3 × 4 factorial design experiment was conducted to determine digestibility coefficients (DC) of dry matter (DM), crude protein (CP), crude fat (CF), gross energy (GE) and amino acids (AA) in raw ground silver hake (RGSH), acid (ASHS) and fermented (FSHS) silver hake silages for mink. The ASHS was prepared with the addition of 2.5% (wt:wt) formic acid (85% concentration) and 200 ppm antioxidant (ethoxyquin) to the raw ground fish. The FSHS was produced with the addition of 1% Marisil® (Finn Sugar), 15% extruded wheat and 1% (wt:wt) formic acid (conc. 85%) to the raw ground fish. Twelve mature standard type male mink were confined to metabolism cages during the digestibility trial, which consisted of three experimental periods comprised of a 6-d adjustment period, followed by a 5-d collection period. Based on the total collection (TC) method and with graded levels (0, 15, 30 and 45%) of the test feedstuffs in the experimental diets, nutrient digestibilities in the pure feedstuffs were determined using a mathematical regression technique. The apparent digestibility (AD) of DM, CP, CF and GE were RGSH: 88.4, 93.6, 99.2 and 94.7%; ASHS: 90.6, 85.8, 96.1 and 87.2% and FSHS: 77.7, 84.5, 99.2 and 86.1%, respectively. The AD of all the AAs, except proline, in the RGSH was significantly higher (P < 0.05) than that in the ASHS and FSHS. A quality evaluation of the silages was conducted in a completely randomized design with two replications to determine storage stability of the silages, on 10 different sampling days, (3 sampling days for AAs), over the storage period. Quality of the silages was stable up to 90 days for the ASHS and 180 days FSHS based on increases in pH and total volatile nitrogen (TVN) content and decreases in N and AA content. The silver hake feedstuffs would provide a good source of highly digestible nutrients for mink and should be considered as opportunity feeds for these animals. Key words: Apparent digestibility, fish by-products, mink, silage, silage quality, silver hake