Allometric Growth and Trophic Indices of Ethmalosa fimbriata (Bodwich) (Clupeidae) in Cross River Estuary, Nigeria

Abstract

Allometry and feeding habits of Ethmalosa fimbriata from Cross River estuary were studied. Total length of the fish ranged from 57 to 62 mm for males and 58 to 65 mm for females. The weight varied between 8.0 and 17.0g for males and 4.0 and 20.0g for females. Females had greater weights than males at 58, 59 and 60 mm total lengths. Growth gradients of weight, stomach length and standard length indicate allometric growth with growth centers at 60 mm total length. The main food items observed were detritus, phytoplankton and sand grains. Detritus and phytoplankton were considered the primary items. Sand grains were considered incidental items. Males had more empty stomachs than females and were considered having less feeding intensity than females. Small sized individuals had higher index of food preponderance in detritus while large sized individuals had higher index of food preponderance in phytoplankton. Ontogenetic diet shifts sustained co-existence of various age groups. Females had higher condition factor than males. Condition factors also increased with increasing total lengths. Ethmalosa fimbriata in Cross River estuary was concluded to exhibit isometric and allometric growths, and were considered to be feeding primarily on detritus and phytoplankton.


Key words: Allometric growth, trophic indices, Ethmalosa fimbriata, Cross River Estuary, Nigeria


Journal of Aquatic Sciences Vol.18(1) 2003: 9-14