Oceanographic Conditions and Surface Layer Biomass Distribution Characteristics in the Waters of Northeastern Taiwan

Abstract

研究所用的黃鰭鮪卵巢係由在台灣南部沿近海作業的鮪釣漁船漁獲物中採集而得；並配合組織學、顯微鏡觀察及肉眼觀察以期瞭解本魚種卵巢的成熟過程。本魚種卵巢的成熟過程分爲五期。由於在採樣過程中未曾發現未成熟的個體，顯示我國沿近海鮪釣漁業足以成魚爲主要漁獲對象。在成熟魚體的卵巢中卵原母細胞的卵徑組成呈多峰分布且同時並存各種不同發育階段的卵原母細胞，顯示本魚種爲多次、分批產卵。黃鰭鮪的卵發生和多數的硬骨魚類相似，可劃分爲13個成熟期。在各個不同成熟階段的卵巢和其中的卵原母細胞最前進的發育階段關係爲：在卵巢之發育階段，卵原母細胞的發育階段處於周邊核仁前期與後期。在卵巢之成熟階段，卵原母細胞的發育階段處於卵黃球的初期、次期和第三期。在卵巢完全成熟階段，卵原母細胞的發育階段處於核移動期與卵粒成熟期。在已完成排卵的排卵期卵巢則可見卵原母細胞退化爲卵黃泡期與卵黃球的初期、次期和第三期。To understand the maturation process,histological,microscopic,and macroscopic observations were conducted on the ovaries of yellowfin tuna(Thunnusalbacares)collected from the landings of Taiwanese inshore longliners operating inthe southern waters of Taiwan.The development of ovaries during maturation can be grouped into fivephases.In the study,no immature ones were found,an indication that the maincatches of yellowfin tuna by the inshore longliners were adults.Based on the polymodal frequency distribution and the different developingstages of the oocytes simultaneously existing in the ovary of matured fish,thespecies was considered to be a multiple and asynchronous spawner.Oogenesis of yellowfin tuna is similar to most of teleostei.It can be broadlydivided into 13 growth stages.A correlation between the maturity phase and themost advanced oocytes stages showed that the developing phase corresponds to theearly and late peri-nucleolus stage;the maturing phase to the primary andsecondary yolk globule stage;the full maturity phase to the migratory nucleusstage and ripe egg stage;the spent phase to the degenerated oocytes at the yolkvesicle stage,primary yolk globule stage,secondary yolk globule stage,andtertiary yolk globule stage.