涉禽對晒池魚塭之利用－－以七股地區虱目魚及文蛤養殖為例

Utilization of Aquaculture Ponds by Wading Birds during the Draining Period-A Case Study on Milkfish and Hard Clam Ponds in Qigu AreaUtilization of aquaculture ponds by wading birds during the draining period－a case study on milkfish and hard clam ponds in Qigu Area

在自然濕地不斷遭受破壞和喪失之下，人工濕地對於水鳥的保育功能日益重要。水產養殖魚塭是台灣主要的人工濕地之一。魚塭晒池時創造出類似泥灘濕地環境，提供水鳥理想的棲息與覓食場所。本研究針對七股常見的虱目魚吋苗及文蛤養殖池進行調查，以了解涉禽對晒池魚塭之利用。虱目魚吋苗池水鳥密度以8-11月較高；文蛤池則為11-1月。虱目魚吋苗養殖晒池時間主要於每年10-11月；而文蛤則主要於11-1月，但每池每2-3年只晒1次。晒池能吸引水鳥利用，兩種養殖池的水鳥密度於晒池中魚塭皆顯著大於養殖中者。而水鳥密度以晒池的第1-4天最高，並隨時間逐漸下降。此外兩種魚塭於晒池時的水鳥組成呈現顯著性差異。將涉禽依覓食行為與形態分為4個同功群：高視闊步覓食鷺鳥（stalking herons）、深水覓食鷸鴴類（pelagic foraging waders）、憑觸覺於灘地覓食鷸鴴類（tactile surface-foraging waders）、憑視覺於灘地覓食鷸鴴類（visual surface-foraging waders）。高視闊步覓食鷺鳥及深水覓食鷸鴴類聚集於晒池的第1-2天，另也利用收成或換水過程水位暫時下降的文蛤池。兩類灘地覓食型鷸鴴類則為晒池過程中利用魚塭的主要類群，另也聚集在冬季養藻中的虱目魚池。虱目魚吋苗及文蛤養殖的操作方式提供了水鳥利用機會，具有水鳥保育的功能。

With continuous loss and degradation of natural wetlands, artificial wetlands have become increasingly important for the conservation of waterbirds. Aquacultural ponds are ones of the main types of artificial wetlands in Taiwan. When the ponds are drained, they create mudflat environment that provide ideal feeding and resting habitat for waterbirds. We examined how wading birds used two types of aquacultural ponds, milkfish(＂chanos chanos＂) ponds and hard clam(＂Meretrix lusoria＂) ponds, both commonly found in Qigu. Waterbirds density of milkfish ponds was higher from August to November, while that of hard clam ponds occurred from November to January. Milkfish ponds were drained after the fish were harvested in October to November every year, while hard clam ponds were drained in November to January every two or three years. The drained ponds could attract waterbirds. The density of waterbirds was higher in ponds during the draining period than in the rearing period. The density of waterbirds was highest during the first four days after dewatering, and then, it gradually decreased with time. Waterbirds assemblages differed significantly between the two types ponds. According to morphological and feeding behavior, the wading birds were categorized into four guild groups: 1) stalking herons, 2) pelagic-foraging waders, 3) tactile surface-foraging waders, and 4) visual surface-foraging waders. Stalking herons and pelagic-foraging waders congregated on the first two days after dewatering, and also in hard clam ponds when the water level was temporarily reduced for harvesting or water changes. Tactile and visual surface-foraging waders were the main guilds during the draining period of the ponds. They also congregated in milkfish ponds during the period of algae cultivation in winter. The study suggests the importance of including waterbirds conservation in the operation tactics of milkfish and hard clam pond management.