臺灣沿岸海域共棲性雀鯛幼魚食性探討

Dietary study of cohabiting juveniles of different damselfishes (Pomacentridae) in coastal waters of Taiwan

吳庭光(Ting-Kuang Wu)

指導教授 ： 戴昌鳳

共同指導教授 ： 詹榮桂(Rong-Quen Jan)

國立臺灣大學/理學院/海洋研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.01491

摘要

被掠食者捕食是導致珊瑚礁魚類幼魚死亡的重要因素。在珊瑚礁常見多種幼魚因為游泳能力尚弱，共同生活在同一個庇護場所且不敢遠離，以避免被捕食。在學理上，當資源有限，生活在一起的物種會使用不同的資源以避免種間競爭的發生。在食物資源的分配方面，過去的研究多是以成魚為對象，對於共棲性幼魚是否會使用不同的食物資源則所知不多。臺灣東北角沿岸的霓虹雀鯛 (Pomacentrus coelestis)、燕尾光鰓雀鯛 (Chromis fumea) 和斑鰭光鰓雀鯛 (C. notatus) 的幼魚常形成魚群，數種共同生活在接近海底礁盤或大石塊上方處；而台灣南部墾丁的藍綠光鰓雀鯛 (C. viridis)、網紋圓雀鯛 (Dascyllus reticulatus) 和三帶圓雀鯛 (D. aruanus) 幼魚則會成群數種共同棲息於一叢枝狀珊瑚群體之間。本論文利用胃內容物分析和穩定同位素分析進行研究，試圖了解這些共棲性幼魚在相同的庇護場所中是否使用不同的食物資源。
經於2010年7月、8月在臺灣北部龍洞灣五個不同的礁盤上採集霓虹雀鯛幼魚、燕尾光鰓雀鯛幼魚及斑鰭光鰓雀鯛幼魚；2009年3月、2010年7月及2011年4月在臺灣南部墾丁9個不同珊瑚叢上採集藍綠光鰓雀鯛幼魚、網紋圓雀鯛幼魚及三帶圓雀鯛幼魚做分析，結果顯示臺灣北部的霓虹雀鯛幼魚、燕尾光鰓雀鯛幼魚及斑鰭光鰓雀鯛幼魚胃內含物皆主要為橈足類、介形蟲以及藻類。胃內含物組成在魚種之間常呈顯著差異，其主要差異在於霓虹雀鯛幼魚取食較多藻類。穩定同位素訊號方面，霓虹雀鯛幼魚、燕尾光鰓雀鯛幼魚及斑鰭光鰓雀鯛幼魚的δ13C值常有顯著差異，大體上是燕尾光鰓雀鯛幼魚的δ13C值最低，霓虹雀鯛幼魚的δ13C值居中，斑鰭光鰓雀鯛幼魚的δ13C值最高；三者的δ15N值亦常有顯著差異，大體上是霓虹雀鯛幼魚的δ15N值較低，其餘兩者接近，這可能是因為霓虹雀鯛幼魚取食一些藻類，而藻類的δ15N值較低。
臺灣南部的藍綠光鰓雀鯛幼魚、網紋圓雀鯛幼魚及三帶圓雀鯛幼魚胃內含物皆主要由橈足類所組成。魚種間有時候有顯著差異，有時候則無。穩定同位素訊號方面，δ13C值在種間常有顯著差異，通常是三種雀鯛幼魚彼此均互有差異或三帶圓雀鯛幼魚的δ13C值顯著高於其餘兩者。三種雀鯛幼魚的δ15N值亦常有顯著差異，通常是網紋圓雀鯛幼魚的δ15N值顯著高於其餘兩者。
在本研究中，臺灣北部共棲性的霓虹雀鯛幼魚、燕尾光鰓雀鯛幼魚和斑鰭光鰓雀鯛幼魚，以及臺灣南部共棲性的藍綠光鰓雀鯛幼魚、網紋圓雀鯛幼魚和三帶圓雀鯛幼魚，雖然數種幼魚一同使用庇護場所，然而不一定使用不同的食物資源。穩定同位素的資料常常與胃內含物分析結果有出入，證明穩定同位素分析可以彌補胃內含物分析為一瞬間紀錄的缺點。綜合胃內含物與穩定同位素的分析結果顯示，食物資源的分配可能是臺灣沿岸不同種雀鯛幼魚之間能夠共棲的一個重要因素。

關鍵字

共棲 ； 雀鯛 ； 幼魚 ； 胃內含物 ； 穩定同位素 ； 龍洞 ； 墾丁

並列摘要

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.

並列關鍵字

cohabiting ； damselfish ； juvenile ； stomach content analysis ； stable isotope analysis

參考文獻

傅以承 (2007) 台灣南部珊瑚礁海域兩種固曲齒雀鯛食性適應性之研究 – 利用 胃內含物和穩定同位素分析. 國立台灣大學海洋研究所碩士論文, 59 pp

Caley MJ (1993) Predation, recruitment, and the dynamics of communities of coral-reef fishes. Mar Biol 117: 33-43

Clarke RD, Finelli CM and Buskey EJ (2009) Water flow controls distribution and feeding behavior of two co-occurring coral reef fishes: II. Laboratory experiments. Coral Reefs 28: 475-488

Colwell RK and Fuentes ER (1975) Experimental studies of the niche. Ann Rev Ecol Syst 6: 281-310

DeNiro MJ and Epstein S (1978) Influence of diet on the distribution of carbon isotope in animals. Geochim Cosmochim Acta 42: 495-506