Comparison of Seaweed Growth, Fish Abundance and Diversity in Deep Water Floating Raft with Tubular Nets and Shallow Water Off-bottom lines Seaweed Farms

Abstract

This study compared the growth performance of Eucheuma denticulatum, fish abundance and
diversity between deep water (using tubular nets) versus shallow water (off-bottom) seaweed
farming methods. For each farming method, three plots were set and fish abundance, diversity and
seaweed growth rates were measured at intervals of 15 days. Belt transects measuring 10 m x 4 m
each, were established on seaweed farms for fish observations. Fish were identified to the lowest
possible taxonomic level by underwater census. The results showed that the growth rate of E.
denticulatum in deep water farms was slightly higher at an average daily growth rate (DGR) of
3.42 ± 0.18% day−1 compared with 3.01 ± 0.27% day−1 for shallow water farms but with no
significant differences (p = 0.079) likely due to higher herbivory in the deep water farms. Fish
abundance and diversity were higher in deep water farms but insignificant (t (34) = 0.69, p = 0.49
and t (34) = 0.424, p = 0.67, respectively). Habitat complexity and seaweed growth rate were almost
similar for both farming methods hence attracting comparable numbers of fish. Further studies are
recommended on fish community structures, differences between the two farming methods and
effects of herbivory.

Keywords: E. denticulatum; seaweed farming methods; growth; fish diversity and abundance