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Vol. 53, 2014
Tidal variation in fish assemblages and trophic structures in
tropical Indo-Pacific seagrass beds
Chen-Lu
Lee1, Yen-Hsun Huang1, Chia-Yun Chung1
and Hsing-Juh Lin1,2*
1Department of Life Sciences and Research Center for Global Change Biology, National Chung Hsing University, Taichung 402, Taiwan
2Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan
Abstract
Background: Tidal cycle is an
important factor which regularly changes coastal fish assemblages in
shallow waters. However, the variations in fish assemblage and trophic
structure across tidal cycles in tropical seagrass beds are rarely
discussed. We used underwater visual censuses to quantify fish
abundance and diversity from the shallow intertidal to the subtidal
zone during both flood and ebb tides in seagrass beds surrounding the
Dongsha Island, South China Sea. We also recorded fish feeding habits
by analyzing stomach contents.
Results: At least 70 fish species were observed in
the seagrass beds during the study periods. Fish density and diversity
increased with increasing depths, as well as during flood tides. The
intertidal areas were characterized by more variation in both fish
assemblage and trophic structure than the subtidal areas. A cluster
analysis identified six principal feeding groups and
invertebrate-feeding carnivores contributed about 70% of the total fish
abundance. The density of herbivores, large-sized carnivores, and
piscivores, but not small-sized carnivores, increased during flood
tides. In contrast, detritivores decreased in density during flood
tides. A heatmap of habitat usage pattern revealed that most fish
showed a preference for deeper stations and flood tides. Only a
minority of fish showed a preference for shallower stations and ebb
tides.
Conclusions: We documented
differences in fish assemblage and trophic structure between tides in
tropical seagrass beds. Our results suggest that water depth may
account for a significant proportion of the variation. The deeper water
during flood tides support more space for herbivores and high trophic
level carnivores to forage in intertidal meadows. The remaining,
non-ebbed seawater columns in the intertidal meadows formed important
temporary refuges for fishes during ebb tides. This study offers new
information for fish movements over tidal
cycles in tropical seagrass beds.
Key words: Coral reef fish; Seagrass; South
China Sea; Stomach content analysis; Tidal cycles; Trophic guilds.
*Correspondence: E-mail: hjlin@dragon.nchu.edu.tw
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