2011-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/701490摘要：長久以來，過漁（overfishing）造成了商業標的魚種（commercial targeted species）的匱乏，乃至於使整個水域生態系的結構發生變化。然而，漁業捕撈是如何改變了魚類族群動態，以及這些漁業效應後續會為族群帶來怎樣的後果，至今仍不清楚。要達到健全的漁業管理，有必要調查漁業效應，尤其需要在氣候變遷的脈絡下探討此一問題。 本計畫旨在探討漁撈對商業標的魚種族群的年齡（體型）結構之影響。有越來越多的研究證據顯示體型大且具產卵經驗的母魚所產下的卵品質好且數量多，這就是所謂的「母系效應」（maternal effects），而且這些研究還發現不同年齡層的魚在產卵時會展現出時空異質性，即傾向在不同的時間、地點產卵。這些行為都是建構在一個健康的年齡結構上，有助於魚群「分散風險」（bet-hedging）的能力，此特性對緩衝短期環境變動的衝擊非常重要。此外，年齡（體型）結構容易測量，這類資料通常在魚群評估報告中就可以找到。 近來針對南加州漁群的分析中發現，由於漁撈選擇性地捕捉體型大的母魚，因而造成魚類族群「年齡截切」（age-truncation）效應，進而增加族群豐度的變異(Hsieh et al., Nature, 443: 859-862)。至於這樣的效應是否普遍出現在全球漁業中，還有待進一步調查。基於此，我們計畫調查全球漁業對商用魚種年齡（體型）結構的影響。本研究針對三大問題。第一個問題是全球漁業目前所造成的年齡（體型）截切效應有多嚴重。要回答這個問題，我們需要盡可能調查所有商業魚種年齡（體型）結構的長期變化。第二個問題是族群變異是否因為漁業的年齡（體型）截切效應而增加，我們將檢視各魚種的族群長期變異，以及這樣的變異和年齡截切效應嚴重性之間的關連。此外，其他相關因子，如漁獲死亡率與魚種的壽命、最大體型、成熟年齡、成熟體長（重）、抱卵數、食階等生活史特徵也會納入分析，探討年齡截切效應隨商業魚種生活史特徵差異的變化。第三個問題是如何建構出聯繫年齡截切效應與族群變異的理論，餵探討這個問題，我們將發展一套族群年齡結構模式。 本研究執行方法包含資料彙整、分析與理論模擬。資料主要是透過數值化軟體從科學文獻或評估報告的圖表取得。最後將建置一公開資料庫，預計這些資訊將會對世界漁業管理有所裨益。 <br> Abstract: Overfishing has caused dramatic changes in structures of exploited populations as well as ecosystems. However, the understandings as to how fishing alters population structures and the subsequent population consequences of these effects have been elusive. For sound fisheries managements, it is important to investigate fishing effects, particularly in the context of a changing climate. In this proposal, we focus on fishing effects on age (size) structures of exploited fishes. Accumulating evidence has shown that large and experienced spawning individuals are able to produce higher quality and quantity of eggs known as maternal effects and that individuals of different age classes tend to spawn in different locations and times. These behaviors are associated with a healthy age structure and contribute to bet-hedging capacity that is important in smoothing out short-term environmental variability. In addition, age (size) structures are easy to measure and have been often measured in exploited species for stock assessment purposes. Our recent analysis in Southern California fisheries indicates that population variability was elevated by age-truncation effects due to size-selective fishing mortality (Hsieh et al., Nature, 443: 859-862). However, how this result can be generalized to world fisheries remains to be investigated. Along this vein, we propose to investigate the consequences of fishing effects on age (size) structures of global fisheries. The first question is how serious the age-truncation is in the global fisheries. To answer this question, we will investigate age (size) structures of exploited populations through time for as many commercial species as possible in the world. The second question is whether the population variability has been elevated due to fishing-induced age truncation. To investigate this, we will estimate population variability through time and examine the relationship between population variability and severeness of age-truncation for each exploited species. In addition, fishing mortality and life history traits, such as longevity, maximal size, age-at-maturation, size-at-maturation, fecundity, trophic levels, will be included as accessory factors in analyses. We shall also investigate how age truncation effects vary according to life history traits of species. The third question is how to theoretically link age-truncation effects and population variability. To do this, we will device an age-structure population model with harvesting. This research will be done with combinations of data compiling, data analyses, and theoretical modeling. The data will be extracted from published literature or assessment reports by digitizing tables and figures. We will then construct a database and make it available to the public. The information gained here will be beneficial for world fisheries managements.年齡（體型）組成空間異質性母系效應漁業管理分散風險策略非線性災變Age (size) compositionspatial heterogeneitymaternal effectsbet-hedgingfisheries managementnonlinear catastrophic shifts