Water quality variation and algal succession in commercial hybrid catfish production ponds

This study on water quality variation and algal succession in commercial hybrid catfishproduction ponds was conducted in 2007 in Bang Pa-In district, Ayutthaya province, Thailand. Thestudy covered two fish crops, May-August and September-December. The physico-chemical waterquality in the catfish ponds changed dramatically over the study period due to the practices of waterchanging, lime application and the culture duration before harvesting. Samples of algae collectedduring the first crop period contained 83 species belonging to the following divisions: Chlorophyta(34 species), Cyanophyta (28 species), Euglenophyta (12 species), Bacillariophyta (6 species),Chrysophyta (1 species), Pyrrhophyta (1 species) and Cryptophyta (1 species). Samples collectedduring the second crop contained 60 species of the following divisions: Chlorophyta (28 species),Cyanophyta (16 species), Euglenophyta (10 species) and Bacillariophyta (6 species). Cyanophytawas the most abundant in both crops, followed by Chlorophyta, Euglenophyta, Bacillariophyta,Chrysophyta, Cryptophyta and Pyrrhophyta. The blue-green algae Microcystis increasinglydominated the algal population during the course of the culture period. Pseudanabaena spp. weresucceeded by Oscillatoria spp. and then Microcystis spp. in the first crop. Microcystis spp.dominated during the first two months of the second crop, and then was succeeded byPlanktolyngbya spp. and Nitzschia spp. in the third and fourth months. In summary, water qualitymay account for algal proliferation resulting in algal blooms and influence algal succession incommercial catfish production ponds.