The initial total bacteria count was around 2.5 log CFU/g (Fig. 2a). Similarly, López-Caballero, Gonçalves, and Nunes (2002) reported counts on Iron Agar of around 2-3 log CFU/g in good quality pink shrimp (P. longirostris). All the batches evolved in a similar way except S-Ch-PCc, where counts were 1.5 log cycles lower than the rest between day 5 and 7 of storage. From that day onwards, the counts increased, reaching 8–9 log CFU/g at the end of the storage trial (p > 0.05). Similar behavior was observed in mesophilic microorganisms, pseudomonas and lactic acid bacteria ( Fig. 2d–f respectively). Batch S-Ch-PCc presented an increase in the lag phase of up to 5 days in mesophilic and lactic acid bacteria counts, which were also the lowest counts. The differences in total mesophilics (p ≤ 0.05) reached as high as 3 log units at 5 day. On chitosan coated cod patties (López-Caballero et al., 2005a) and culture prawns (Marsupeanaeus tiger) treated with chitosan as an antimelanosic formula ( López-Caballero et al., 2006), the presence of the chitosan coating seemed to stimulate slight growth of the lactic acid bacteria, probably because the pH on the patty surface pH was reduced by the acid (acetic acid) solution in which the chitosan was dissolved. In this respect, chitosan oligosaccharides have been reported to have a bifidogenic effect at concentrations between 0.1 and 0.5% and to stimulate growth of Lactobacillus casei and Lactobacillus brevis at 0.1% ( Lee, Park, Jung, & Shin, 2002). In the present study, the increase in lactic acid bacteria counts with the chitosan coating solution (in lactic acid) was not significant (p > 0.05).