Shoal Density,Distribution and Fluctuation Rhythm of Swordtip Squid Influenced by Mackerel and Hairtail in the Illumination Zone During the Light Fishing Operation

Abstract

花身雞魚Thornfish(Terapon jarbua Forsskal)為本省沿岸的優勢魚種，其仔稚魚於每年4-10月間成群洄游於河口域。本研究的目的在比較正常與畸型花身雞魚耳石成長的差異性，並推測畸型魚發生時的日齡及其生活履歷。結果發現金山核二廠排水口正常與畸型魚耳石與體長的相對成長關係有顯著性的差異，但兩者的體長與體重關係並無顯著性差異。由耳石形態變化及日輪數，得知花身雞魚大約在孵化後21天進入排水口附近海域。受到高水溫的影響，畸型魚耳石的成長比正常者快，因此造成耳石與體長的相對成長的不偶合現象。Thornfish(Terapon jarbua Forsskal)is one of the dominant species of fish in thecoastal waters and estuaries of Taiwan.Its larvae and juveniles migrate to these areasduring April to October.This study compared the difference in the morphology of otolithbetween the normal and deformed thornfish collected in the waters around the thermaleffluent outfall of the Kin-Shan nuclear power plant and in the estuary of Gong-Shy-Tyan Creek in northern Taiwan.Also,the daily ages and early growth life history ofthe deformed thornfish were examined.Fish length and otolith length relationship wassignificantly different between the normal and the deformed,but not for the length-weight relationship.The thornfish migrated to the nearshore waters at the age of approximately21 days after hatching.The deformity was due to high temperature.Growthof otolith was faster in the deformed than the normal.This leads to uncoupling of somaticand otolith growths for the deformed fish.