Food and Feeding Biology of a Stream dwelling Ornamental Loach Acanthocobitis botia (Hamilton, 1822) from Upper Brahmaputra Basin, North East India

Abstract

The food and feeding habit of a prominent freshwater ornamental loach species Acanthocobitis botia (Hamilton, 1822) was studied based on 462 individual specimens collected from upper Brahmaputra valley region in Assam, north-east India. The mean relative length of the gut (RLG) for the species was 0.94 ± 0.02 (range 0.85 - 1.15), indicating carni-omnivorous nature of its feeding. The gastrosomatic index (GaSI) value ranged between 2.15 and 2.71with variations between different length or size groups, sexes as well as seasons. Seasonal rise and fall in the feeding intensity was also observed where pre-monsoon being the active feeding period for the species in their natural habitat. Eight different categories of food items, viz., zooplankton, small fishes, insects, crustaceans, annelids, molluscs, plant matters as well as unidentified matters were identified during gut content analysis. Of these, decaying plant matters (27.65%), insects (13.25%), small fishes (12.8%) and zooplankton (9.75%), crustaceans (6.75%) were the most important food items encountered in the guts while occurrence of molluscs (3.5%) and annelids (3.15%) were relatively low in the gut.  Considerable seasonal variation in occurrence and percent composition of food items in the diet was also observed. Calculation of index of pre-ponderance (I_i) reveals decayed plant matters, small fishes, insects, crustaceans and zooplankton are the major food items for this species.  A considerable variation of feeding intensity was also observed for the individuals in different maturity stages where 40% of individuals in maturing stage exhibit highest active feeding while most individuals in ripe and spent stages were with empty gut thus showed  poor feeding. Short and uncoiled alimentary canal and possession of a fleshy sub-terminal (inferior) mouth also suggests towards the carni-omnivorous feeding and bottom dwelling nature of the species.