TITLE:
Effects of Temperature upon Water Turnover in Fish Ponds in Northern Thailand
AUTHORS:
Patcharawalai Sriyasak, Chanagun Chitmanat, Niwooti Whangchai, Jongkon Promya, Louis Lebel
KEYWORDS:
Climate; Temperature; Oxygen; Turnover; Fish Culture
JOURNAL NAME:
International Journal of Geosciences,
Vol.4 No.5B,
October
11,
2013
ABSTRACT:
Fish culture in earthen ponds is an important source of
income for farmers in northern Thailand. Water quality in ponds has strong
impacts on fish production farmers’ return and is sensitive to weather and
climate. Low levels of dissolved oxygen in fish ponds are major cause of mass
mortality. Stratification with depth in ponds followed by rapid turnover or
exchange of surface and bottom water can expose fish to dangerously low
dissolved oxygen levels. The main purpose of this study was to observe the
effects of weather on stratification and subsequent water turnover in fish
ponds in northern Thailand, especially in the winter and rainy season, when
stratification was expected to be most severe. Temperature and water quality
measurements were made in fish ponds at 18 farms with depths ranged from 0.8-2.0 m
and size of 0.16-0.64 ha. Measurements were made during January and May 2013. Fish
farm pond sites were divided into two groups based on elevation above sea level:
low (400 masl) and categorized into 3 types of farming:
commercial, integrated and subsistence. In lower elevation sites, water
turnover occurred at night between 22.00 and 02.00 in winter and between 18.00
and 02.00 in rainy season. At higher elevation, turnover occurred in ponds between
20.00 and 22.00 in winter and between 14.00 and 18.00 in rainy season. Turnover
was slower in the lower elevation than in higher elevation zones and generally
occurred earlier during the rainy season than in the winter. Mean DO in winter
was significantly higher (p