利用魚類行為－物理洋流耦合模式探討日本鯷於東海至台灣之產卵洄游途徑

Abstract

日本鯷的仔稚魚（吻仔魚）為台灣重要的經濟漁業物種，自1990年代以來捕獲量開始明顯減少。一般認為產卵成魚數量會直接影響其再添加過程，進而影響其漁獲量。然而，日本鯷屬於多次產卵、且有多個產卵場的物種，因此在野外進行產卵場與產卵洄游研究十分困難。故本研究中使用魚類行為－物理洋流耦合模式（Coupled fish behavior-hydrodynamic model）進行日本鯷產卵洄游模擬，試圖了解在洄游過程中環境對產卵洄游的影響。 本模式中的環境部份使用DUPOM（Dual-grid Pacific Ocean Model）海洋環流模式進行模擬。此模式以DieCAST環流模式為基礎，並在模擬中加入長江淡水輸入，以了解三峽大壩完工後，長江流量減少對周遭海域的影響。生物部份使用拉氏顆粒追蹤模式（Lagrangian particle traciking program）模擬日本鯷洄游，並加入初階魚類游泳行為以探討游泳在洄游過程中所扮演的角色。 結果發現，中國沿岸流（China Coastal Current）的強度受長江流量的多寡所影響，對日本鯷產卵洄游有很大的助益。此外，游泳行為也十分關鍵，將會影響洄游方向與抵達時間，使日本鯷能在產卵季開始前抵達近岸的產卵場。本研究也顯示，使用物理洋流模式與簡化生物模式耦合，可以更加了解海洋中環境因子與生物過程將如何影響其中的魚類族群。

The Japanese anchovy (Engraulis japonicus) larval fishery is one of the important fisheries in Taiwan, and the fishery catch has significantly decreased since the 1990s. The abundance of spawning adults likely influences the recruitment process and thus the fishery catches. However, Japanese anchovy is known as a multi-batch species with many different spawning grounds, which makes the field study of the onset of spawning migration and its possible migration routes difficult. Here, an approach based on a coupled fish behavior-hydrodynamic model is used to simulate spawning migration of Japanese anchovy. The physical part consists of an ocean circulation model - Dual-grid Pacific Ocean Model (DUPOM), which is based on the fourth-order accurate, collocated Arakawa-A grid DieCAST (Dietrich/Center for Air Sea Technology) model. The change of Changjiang discharge is also included for investigating the potential influence of reduction in discharge causing by Three Gorge Dam. The biological part uses the Lagrangian particle tracking program to simulating fish migration with a primarily approximation of fish swimming behavior. The simulation results suggest that the spawning migration of Japanese anchovy may be aided by the China Coastal Current (CCC). In addition, the Changjiang discharge has significant influence on the migration of Japanese anchovy. The swimming behavior of anchovies is crucial during spawning migration, as it provides extra velocity for fish moving farther and closer to the coastal area. Results in this research demonstrate that a physical model coupled with a simplified biological model can help us better understand how the biological processes and marine environment affecting the fish population.