Halophilic Vibrio spp. associated with hard clams (Mercenaria spp.) from the Calabar river estuary.

One hundred and ten hard clams (Mercenaria spp.) harvested from the Calabar river estuary were examined for total platable heterotrophic bacteria and Vibrio spp. in their mantle fluids using estuarine salts agar and thiosulphate citrate bile salts sucrose agar plates respectively. The mean counts of heterotrophic bacteria and vibrios were 7.9 x 10(6) organisms/ml and 2.5 x 10(2) vibrios/ml respectively. The rate of vibrio infection was 58.2%. Of the clams positive for vibrios, 54 (84%) harboured dual infections (V. alginolyticus and V. parahaemolyticus) of the moderate grade (greater than or equal to 10(3) to 10(5) vibrios/ml). Single infections due to V. alginolyticus or V. parahaemolyticus, found in 16% of clams, were either low (less than 10(3) vibrios/ml), moderate (greater than or equal to 10(3) to 10(5) vibrios/ml), or high (greater than 10(5) vibrios/ml). Dual infections only were detected in clams with mantle fluid volumes greater than 30 ml.