A re-appraisal of feeding relationships of damselfishes
Date Issued
2007
Date
2007
Author(s)
Ho, Cheng-Tze
DOI
zh-TW
Abstract
A sheer number of fishes inhabit coral reefs, where they are also major consumers. Complex feeding interactions occur between fishes and their preys. Since these interactions involve fluxes of nutrients and energy, there is a need to learn their feeding relationships to elucidate the thermodynamics on coral reefs. Damselfishes (Pomacentridae) are common inhabitants on both coral reefs and sandstone reefs. Previously the dietary data of damselfishes was mostly based on conventional stomach content analysis. However, stomach content analysis reflects short-term diets of fishes, and food items that are digested quickly, such as detritus and invertebrates, are generally difficult to identify and enumerate. Because the stable isotopes in tissues of consumers are typically enriched relative to those of their prey, stable isotope analysis was used to study feeding ecology of fishes here. In this study, damselfishes were used as materials. Their dietary components and potential foods were examined by both stomach content and stable isotope analyses. Issues dealt with included temporal dietary changes of neon damsel, dietary comparisons between Stegastes spp., feeding interactions between a territorial damselfish and blennies, and the effect of anthropogenic enrichment on diets of damselfishes. Results revealed that in the neon damsel, the liver bore a higher isotope turnover rate compared with the white muscle, thus might reflect rapidly changes of δ13C and δ15N from the food source. In contrast, isotopic signature of the white muscle was steadier, reflecting a sign of long-term accumulation. The major organic source for algal-farming Stegastes damselfishes was likely to be the polychaetes hidden in the algal lawn. The algae farmed by the fish were possibly to secure polychaetes rather than to use as food source. Moreover, the widespread territory overlap between Pacific gregory and blennies was possibly a sign of mutualism. Fish feeds released by cage fish farms in Siaoliouciou Island were taken by resident damselfishes either by direct ingestion or by way of uptake by zooplankton. Thus the retention of nutrient enrichment had gotten through in a food chain not involving primary producers such as algae. These findings have unraveled insights into food webs on coral reefs and feeding relationships between reef fishes. Overall, it is suggested that the nutrient source of herbivorous fishes on coral reefs be re-examined for a better understanding of the feeding ecology of fishes.
Subjects
雀鯛
珊瑚礁
草食動物
領域性
穩定同位素
damselfish
coral reef
herbivore
territoriality
stable isotope
Type
thesis
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