Gut ph and digestive strategies in estuarine grey mullet (Mugilidae) and tilapia (Cichlidae)

Tilapia guineensis , which feeds on leafy material, and Sarotherodon melanothron , which utilizes blue‐green algae, were both capable of producing a pH 2 or less in the stomach which could contribute to the lysis and digestion of blue‐green algae and bacteria. Of the grey mullets investigated, Liza falcipinnis had a gastric pH 3.3–4.5, which may not be low enough to cause cell lysis, whilst Liza dumerili, Mugil cephalus and Mugil curema all had stomach, caecal and intestinal pH's of 7–8.5. Grey mullet appear to have a different digestive strategy to tilapia and may rely upon the establishment of a ‘colloid mill’ in the stomach.