Abstract. The effect of body size and salinity on the rate of digestion of young grey mullet,. Mu~l cephalus L., was studied using the "sacrifice" method. The rate of ...
Marine Biology 44, 383-387 (1978)
MARINE BIOLOGY 9 by Springer-Verlag 1978
Studies on the Biology of Young Grey Mullet (Mugil cephalus) Digestion P.A.B. Perera and S.S. De Silva Department of Zoology, Vidyalankara Campus, University of Sri Lanka; Kelaniya, Sri Lanka
Abstract
The e f f e c t
of b o d y size and s a l i n i t y on the rate of d i g e s t i o n of y o u n g grey mullet, L., was s t u d i e d u s i n g the " s a c r i f i c e " method. The rate of d i g e s t i o n was f o u n d to be s a l i n i t y - d e p e n d e n t , b e i n g s l o w e r at lower s a l i n i t i e s than at h i g h e r s a l i n i t i e s . This is c o r r e l a t e d to h i g h e r food i n t a k e at the lower s a l i n i t i e s . Rate of d i g e s t i o n was also found to be d e p e n d e n t on b o d y size, i n c r e a s i n g w i t h increasing body weight.
M u ~ l cephalus
I ntroduction
The d i g e s t i v e p h y s i o l o g y of t e l e o s t fish has b e e n r e v i e w e d by B e r n a r d (1952), B a r r i n g t o n (1957) and K a p o o r et al. (1975). It is g e n e r a l l y a c c e p t e d that p h y s i o l o g i c a l p r o c e s s e s of d i g e s t i o n are d e p e n d e n t on a n u m b e r of e n v i r o n m e n t a l and e n d o g e n o u s factors and also on the q u a l i t y and q u a n t i t y of food ingested. A l t h o u g h studies on aspects of food and f e e d i n g on c e r t a i n m u g i l i d s , and Mugil cephalus L. in p a r t i c u l a r , h a v e b e e n c a r r i e d out (Luther, 1962; Suzuki, 1965; Odum, 1968, 1970; De S i l v a and W i j e y a ratne, 1976), there is no i n f o r m a t i o n a v a i l a b l e on any a s p e c t of d i g e s t i o n of this e u r y h a l i n e species. This p a p e r is the fourth of a series of d e t a i l e d inv e s t i g a t i o n s into the b i o l o g y of y o u n g grey m u l l e t and f e a s i b i l i t y of its culture in the c o a s t a l e s t u a r i n e w a t e r s of Sri L a n k a (see De S i l v a and Perera, 1976; De S i l v a and W i j e y a r a t n e , 1976; P e r e r a and De Silva, in p r e p a r a t i o n ) , and h e r e r e s u l t s on g a s t r i c d i g e s t i o n are p r e s e n t e d .
Materials and Methods
Mugil cephalus L.,
r a n g i n g in total length from 10 to 50 mm, w e r e c o l l e c t e d from the s h a l l o w areas of a c o a s t a l lagoon, the N e g o m b o L a g o o n (7~ ' N; 79o50 ' E), u s i n g a cast net of I cm s t r e t c h e d mesh. L a b o r a t o r y e x p e r i m e n t s w e r e c a r r i e d out at the F i s h e r i e s R e s e a r c h S t a t i o n situ-
ated close to the m o u t h of the lagoon. The fish w e r e g r o u p e d a c c o r d i n g to size, and k e p t in glass a q u a r i a u n t i l the start of the e x p e r i m e n t s (see Perera, 1976). Experiments were performed with g r o u p s of fish at s a l i n i t i e s of
