碩士 / 國立臺灣大學 / 海洋研究所 / 100 / Predation appears to be a major cause of mortality of reef-associated fishes, especially of new recruits. Many juveniles of coral reef fishes exhibited strong affinities for branching corals or other complex-structured shelter in order to avoid predation. Competition theory predicts that, when resources are limiting, interacting species should use different resources where they co-occur, namely, resource partitioning. Previous studies mostly focus on adult damselfishes, and little is known about whether resource-partitioning occurred between the cohabiting damselfish juveniles. On the northern coast of Taiwan, juveniles of Pomacentrus coelestis, Chromis fumea, and C. notatus often live together in groups near the rocky sea floor; by contrast, on the southern coastal coral reefs, juveniles of C. viridis, Dascyllus reticulatus and D. aruanus often live together in branching coral colonies. This study uses both stomach content analysis and stable isotope analysis to investigate whether these cohabiting damselfish juveniles use different food resources thereby to promote our understanding on fish interactions.
Juveniles of P. coelestis, C. fumea and C. notatus were collected from 5 different sites at Ludong Bay, north-eastern Taiwan during July 2010 and Auguest 2010, and juveniles of C. viridis, D. reticulatus and D. aruanus were collected from 9 different branching coral colonies at Kenting, south Taiwan during March 2009, July 2010 and April 2011. Those fishes were taken back to laboratory for both stomach content analysis and stable isotope analysis.
Despite that copepods served as the main food item of juveniles of P. coelestis, C. fumea and C. notatus, MANOVA shows significant differences of stomach content composition between these 3 species. P. coelestis differs from the other two by taking more algae. Stable isotope analysis shows significant differences of δ13C value between P. coelestis, C. fumea and C. notatus. The lowest δ13C value occurred in C. fumea, followed by P. coelestis, and C. notatus. Significant differences also occurred in the δ15N values. P. coelestis has the lowest δ15N value. This is probably due to that P. coelestis fed more on algae, and algae bore lower δ15N signatures contrasting to other food sources. Otherwise, the δ15N value of the other two damselfishes are about the same.
On coral reefs copepod is the main food item for C. viridis, D. reticulatus and D. aruanus. The stomach contents differed significantly only in some occasions between co-habiting damselfishes. Differences of δ13C value occurred frequently between the 3 species. The δ13C value of the 3 species might all differ from each other, or the δ13C value of D. aruanus is higher than those of the other two. Differences of δ15N value also occurred. The δ15N value of D. reticulates is often higher than those of the other two.
In this study, the supports for food partitioning were not consistent between samples. In some cases juveniles of different damselfishes which shared the same habitat or shelter, do not necessarily use different food resources. Food resources might not be a prime resource dimension governing the coexistence of different damselfish juveniles. Other factors, such as food abundance, predation pressure, and space, etc., may also play role in the community structuring.
| Identifer | oai:union.ndltd.org:TW/100NTU05279027 |
| Date | January 2012 |
| Creators | Ting-Kuang Wu, 吳庭光 |
| Contributors | Chang-Feng Dai, 戴昌鳳 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 61 |
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