臺灣周遭海域頭足類群聚結構與兩種槍魷生活史特徵之探討

Community structure of cephalopods on the continental shelf and upper slope of Taiwan and life-traits of two loligos

彭彥菱(Yen-Ling Peng)

指導教授 ： 魏志潾

共同指導教授 ： 何瓊紋(Chuan-Wen Ho)

國立臺灣大學/理學院/海洋研究所/碩士(2019年)

https://doi.org/10.6342/NTU201903251

摘要

頭足類（Cephalopod）為臺灣重要的漁業資源之一，但過去國內多半是針對少數經濟物種進行詳細的資源解析或生物學等研究範疇，較少從整體頭足類生物多樣性及群聚結構去整合資料，本研究目的為探討臺灣周遭海域頭足類在不同空間尺度下群聚組成與多樣性變化。頭足類資料來自研究計畫「台灣地區底拖漁業資源之調查評估及其資料庫之建立」，以單船板拖網（otter trawl）作業為主，自西元2000年至2004年間在臺灣周圍海域，以分年分區之方式進行底棲漁業資源生態調查，範圍涵蓋臺灣東北部（北宜）、西南部（高屏）、澎湖群島及西北部（竹苗、彰化）海域，總共有131個測站，深度範圍從10 m至800 m，共發現15科36屬71種的頭足類，並測量物種多樣性（Taxonomic diversity）：單一群落的α-多樣性與整體區域的γ多樣性，群落間物種組成差異的β-多樣性：物種置換（Turnover）及物種嵌套（Nestedness）的群聚變化機制，以探討不同層面生物多樣性在空間尺度下的變化，而生物群聚分布與環境因子之關係，則透過多維空間尺度分析（MDS）及冗餘分析（RDA）來解釋。結果顯示頭足類群聚主要可分為三群，分別為東北－西南海域、西北部－澎湖群島及四個海域混合組合（SIMPROF test, p < 0.05）且四個區域頭足類的組成皆有顯著差異（PERMANOVA test, region, p < 0.05）。在陸棚上（淺於100 m）頭足類從西北至澎湖的組成變異則與初級生產力逐漸下降有關。西北海域的高γ多樣性應為常見種及優勢種組成變異（β - diversity）較高所致；而在陸棚及陸坡的交界（深於100 m），除了深度的影響，西南部的地形崎嶇度高於東北部則是造成頭足類組成具有區域性差異的主因，西南海域多維的空間變化提供物種更多棲位，使稀有物種得以與常見和優勢物種共存。而物種置換是影響頭足類β-多樣性在各海域及深度區間的主要機制，此結果可歸因於食物來源在空間梯度分布不均，進而產生強烈的環境過濾作用，使得適應能力較差之種類被取代。綜合來看，臺灣周遭海域頭足類的分布主要受到深度、地形歧異度及表層平均初級生產力的影響。而RDA模式無法解釋的變因可能代表其他環境因子如水團、生物特性或種內(或種間)生物交互作用的影響。本研究以科學調查資料區分臺灣周遭海域底棲頭足類群聚，供未來漁政單位作為頭足類資源管理之參考。

關鍵字

頭足類群聚組成 ； α多樣性 ； β多樣性 ； 物種多樣性 ； 物種置換 ； 物種嵌套

並列摘要

Cephalopods are among the most important fishery resources in Taiwan. Previous studies have largely focused on the biology or stock assessment of commercially important species; however, little is known about the biodiversity and community structure of demersal cephalopods, as well as the environmental factors controlling their distributions. Therefore, we analyzed 131 samples, covering depth ranges from 10 to 800 m from the research project, “Investigation, Evaluation and Database Establishment of Bottom-Trawl Fishery Resources in Taiwan”. The sampling design was to separate the coastal and offshore waters around Taiwan into four regions (the Northeast, Southwest, and Northwest off Taiwan and around the Penghu Islands) with surveys covering one region each year during 2000–2004. The comprehensive database generated by the project encompasses a total of 15 families, 36 genera and 71 species of cephalopods. In this study, we compared the biodiversity at different spatial scales (i.e., α, β and γ- diversity), and examine the relationship between community structure and environmental factors using the multi-dimensional scale (MDS) and redundancy analysis (RDA). The results showed that the cephalopods around Taiwan can be divided into northeastern (NE) - southwestern (SW), northwestern (NW) - Penghu Islands (PW), and mix-region assemblages (SIMPROF test, p < 0.05). Cephalopod species composition was significantly different among the four geographic regions (PERMANOVA test, region, p < 0.05). On the continental shelf (shallower than 100 m), the compositional variation of cephalopods from NW to PW is related to the decline of primary productivity. The high γ diversity in the NW may be caused by the high dissimilarity among common and dominant species (β- diversity). On the upper slope (deeper than 100 m), water depth and topographic roughness are the main factors causing the compositional difference of the cephalopods between NE and SW region. The more complex topography in the SW comparing to the NE region probably provides more ecological niches, allowing different species to coexist. Species replacement dominated the beta-diversity across regions and depth strata, which can be attributed to the uneven distribution of food sources, resulting in strong environmental filtering, making the poorly adapted species being replaced by species with better fitness. Overall, the community structure of cephalopods was mainly affected by depth, seafloor roughness, and primary productivity. The unexplained variability in the RDA model may represent the effects of other factors such as water mass, biological traits, or biological interactions. Our study provides a historical baseline of demersal cephalopod assemblages against future ecosystem changes and a reference for the fishery resource management and conservation planning around Taiwan’s EEZ.

並列關鍵字

Community structure of cephalopod ； α-diversity ； β-diversity ； Taxonomic diversity ； Turnover ； Nestedness

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