In this study effects of acidification with an organic acid (3 %, formic acid - FA) and an organic-inorganic acid mixture (1.5 % FA + 1.5 % sulphuric acid - FASA) were evaluated on a non-target species (mantis shrimp - Erugosquilla massavensis). Nutritional composition (proximate analysis and fatty acid composition), chemical (biogenic amine concentrations, non-protein nitrogen -NPN and pH) and microbiological assessments (total viable counts -TVC and lactic acid bacteria counts -LAB) were conducted under 27-28 degrees C. The analysis conducted for a 60 day period at 1th, 7th, 14th, 30th, 42nd, and 60th day intervals. Moisture contents of acidified shrimp were significantly lower than the raw material. No changes in protein contents and an increase in lipid content only in FASA group were observed. Palmitic acid, stearic acid, palmitoleic acid, oleic acid and docosahexaenoic acid (DHA) were observed to be the dominant fatty acids in raw and acidified mantis shrimp. The initial pH value of mantis shrimp was 7.71 and became stable (4.14-3.97) throughout the storage period. An increase was observed in NPN contents and FA and FASA were 0.56 and 0.51 g 100 g(-1), respectively at the end of the storage. Putrescine (3.00 mg 100 g(-1)), tyramine (2.94 mg 100 g') and serotonin (2.71 mg 100 g(-1)) were found to be the dominant biogenic amines in raw mantis shrimp. No significant changes in biogenic amine concentrations were observed in general during the storage period. TVC was found as 4.16 log cfu g(-1) at the beginning of the storage period. Bacterial load was decreased after the addition of acids and stayed low throughout the storage period. Increases were observed in LAB and this value were 4.50 and 5.68 log cfu g(-1) for FA and FASA group, respectively at the end of the storage period. The results showed acid treated mantis shrimp could be considered potential feed component due to its high nutritional value and safe in regards of biogenic amines.