RESPONSE OF TROPHIC GROUPS OF MACROBENTHIC FAUNA TO ENVIRONMENTAL DISTURBANCE CAUSED BY FISH FARMING

Abstract

Sediment dynamics and the hydrodynamics of the environment cause the complexity and variability in
animal-sediment relationship, both in spatial and temporal. This study is focused on the response of
macrobenthic fauna to environmental disturbance caused by fish farming using their trophic structure.
Their changes in trophic structure can be used as an indicator of disturbance. Eight control sites and eight
farm pontoon sites were samped in a full year period. Two stations at each site were sampled five times
throughout the year with four replicates. Macrobenthic abundance was categorised based on six major
trophic groups: carnivores (CAR), herbivores (HER), omnivores (OMN), suspension feeders (SF), surface
deposit feeders (SDF), and subsurface deposit feeders (SSDF). The Infaunal Trophic Index (ITI) and
Shanon-Wiener diversity index (H’) were used to assess the degree of environmental disturbance caused by
fish farming based on trophic structure. The relationship between ITI and H’ was assessed using
Spearman’s rank order correlation (rho). The result showed that the abundance of deposit feeders was
significantly higher at the farm sites than at the control sites, suggesting that food availability is more
varied and abundant at farm sites than those at control sites. The results of the ITI indicate that the entire
sampling sites have been moderately disturbed over the sampling period, with the exception for site BC8.
Variability of Shanon-Wiener diversity index (H’) spatially and temporally seems co-vary with ITI, owing to
the influence of taxa richness and evenness.