Immediate effect of bottom trawling on nutrient concentration was studied by conducting experimental trawling operations along Cochin -Munambam area (Long. 75" 56'00 to 76'10' 94" and lat. 9O58' to 10°10') (southwest coast of India) at depth ranging from 0-50m during December 2000- November 2001. The highest values of nutrients were obtained during monsoon and lowest in premonsoon. Higher values were recorded at bottom than at surface. Availability of nutrients was perceptibly high immediately after trawling when compared to  before it. Highest differences in phosphate concentration were noticed at 0-10m depth zone in December, where the values before and after trawling were 0.56 and 3.96 micromoles/litre respectively. Similar was the case with nitrite, the values were 0.66 and 2.88 micromoles/litre before and after trawling. Significant changes were noticed in samples collected from bottom,5m and 10 m above bottom before and after trawling while the variations in samples collected from surface were found to be less significant. 

Impact of bottom trawling, change in nutrients avaialability, phosphate and nitrite