台灣北海岸變色雀鯛之產卵生態研究

Abstract

本文係以臺灣北部龜吼礁岩海域內的變色雀鯛為材料，調查雄魚的生殖成功量(reproductive success)與其形態、巢穴等特徹的相關性，以期找出影響雄性生殖的主要因數。 實驗中以雄魚獲得的卵塊面積作為其生殖成功量的指標。變色雀鯛的交配系統為一夫多妻制(Polygamy)，一個巢中通常包含一個或數個不同發育階段的卵塊，而一個卵塊通常是由一隻雄魚連續與數隻雌魚交配所產生，因此巢中的卵塊面積越大，表示有越多的雌魚與之交配。為了避免巢的材質、形狀對雄魚的生殖所可能造成的影響，另以薄木板製作了四種大小規格的人工巢，予雄魚生殖之用。在人工巢放置後不久，即有雄魚前來築巢並成功地生殖。人工巢的加入，使得實驗地區變色雀鯛的生殖巢數目最高增加至 180% ，顯示此地變色雀鯛產卵地點不足的現象相當嚴重。 結果顯示，人工巢的面積越大，所能容納的卵塊面積就越大，雄魚因而享有較高的生殖成功量，但雄魚本身（體長）與其生殖成功量並無明顯的正相關，同時較大的雄魚也不見得能獨佔較大的人工巢。卵塊的存活率與巢的大小、護巢雄魚的體長（尾叉長）以及生殖成功量無關，但巢中的卵塊面積愈大，卵塊的損失率就會愈小。從雄魚對這有限的產卵地點的競爭，以及巢的大小對雄魚生殖成功量的影響來看，空間資源應是雄性變色雀鯛生殖時最重要的影響因數之一。而雌性選擇的證據在此實驗中並不明顯，雌魚對體型較大的雄魚沒有偏好，同時亦無足夠的資料可支持雌魚對生殖巢的好壞進行主動的選譯。

In this thesis, correlations between male reproductive success and male phenotypic characteristics, nest characteristics were investigated in a natural population of neon damselfish, Pomacentrus coelestis, on the northern coast of Taiwan (124°41'E, 25°12'N). Reproductive success of the nesting male was quantified by measuring the area of egg patches in each nest during the study period. Neon damselfishes are polygamy during spawning. In a nest, multiple egg patches which were often deposited by multiple females were frequently found. Thus the larger the egg mass is in a nest demonstrates the more females the nesting male had mated. In this study, wood boards of four different sizes were provided at the spawning ground as artificial nests for the fish. These artificial nests, soon after being introduced, were occupied and defended by individual males. Egg patches were later found in most of these artificial nests. As a result, the males successful in spawning increased to 180% .This finding indicates that suitable spawning substrates for the neon damselfish were limited in this study area. Furthermore, the males defending larger artificial nests, which provided more surface for egg-laying, showed higher reproductive success. However, male reproductive success was not significantly correlated with the male size. Moreover, larger males did not monopolize larger artificial nests. Egg-survival rate was neither correlated with nest size, male size, nor with reproductive success. But egg-lost rate was negatively correlated with egg mass size. The male-male competition for the limited nesting substrates and the effect of nest size on male reproductive success suggest that space is one of the most important determinants of male reproductive success. The evidence of female-choice is not obvious in this study, females didn't prefer to larger males; and data were insufficient to support the notion females actively chose better spawning sites.