Sunday, October 18, 2026
Friday, October 16, 2026
日本 2026年漁期(2025年11月-2026年10月)鰻苗交易價格,創下2010年以來最低價格水準
日本水產廳於今年7月8日更新其網站上公布的有關鰻魚的現狀及其因應措施之內容,顯示2026年漁期(2025年11月-2026年10月)日本鰻鰻苗交易價格(入池價格)連續2年下滑,每公斤為66萬日圓。這是日本鰻鰻苗從2014年漁期以來,在睽違12年後首度跌破每公斤100萬日圓,又創下2010年以來最低價格水準(圖參照),並分析推測這是由於2025年鰻魚苗豐收導致入池量多,成鰻庫存量多,而弱化今年入池量之需求。
就日本鰻苗交易價格進行產業界調查顯示,從2016年漁期之日本鰻魚養殖改為許可制以來,由於受到鰻苗連續漁獲不佳影響,2018年漁期之鰻苗價格飆升至觸頂每公斤299萬日圓,其餘各年單價在200萬日圓的年份約佔一半,特別是2022-2024年漁期3年之單價連續超過200萬日圓。峰迴路轉是日本玻璃鰻苗採捕量非常豐饒的2025年漁期,其單價比2024年漁期之250萬日圓幾乎下降一半至130萬日圓,此漁期之單價又只及2025年漁期之半價而已(圖參照)。
每公斤玻璃鰻苗以5,000尾計,單價200萬日圓時代,一尾近400日圓,而此漁期降到一尾只剩132日圓。但是養殖成本仍然因燃油價格高導至資材、飼料與人事費之飆高,入池量增加也影響成鰻市場不如預期而導致市場價格下降,造成現有池中或庫存之成鰻價格與市場價格間有差距,對養殖戶造成損失,而陷入非常艱困的窘境。
水產廳先前公布迄5月底為止,日本之入池量為16.6公噸,其中日本鰻鰻苗之進口量為5.9公噸(比上一年增加73%),入池量減去進口量後之日本國內採捕量為10.6公噸(比上一年減少31%),即下降約三成。即國內鰻苗入池量中國內採捕量的佔比下降17%,為64%,這是日本鰻養殖實施許可制以來的11個漁期中,採捕佔第五高的一年。
2025年漁期是玻璃鰻苗列入水產流通適正法實施對象魚種的第一年,據推估當年仍有1.2公噸鰻苗經不透明採捕與流通。
2025年全國共收到各都道府縣知事核可之6,955名與1萬5,887位採捕人的漁獲報告,總採捕量為11.8公噸(前一年為18.2公噸),進口之鰻苗為5.9公噸(上一年3.4公噸),另有2.4公噸出口(前一年為2.4公噸),減掉出口之2.7萬公噸,15.4公噸為日本407家鰻魚養殖業該年之入池量(前一年為19.0公噸),但據報導當年日本玻璃鰻苗之入池量為16.6公噸(前一年18.7公噸)。比推估多出1.2公噸(前一年少0.3公噸)。據水產廳表示其中日本國內實際之玻璃鰻採捕量為13.0公噸(前一年為18.0公噸)。
前一漁期(2015年)為豐收期,與前幾個漁期相比,玻璃鰻苗進口量的差異的確變少,可被視為納入流適法效果的具體體現,但尚未完全解決也是事實,水產廳表示:「差異發生原因可能是現場數量量測的問題,也有可能是流適法宣導不足,致認識與執行不足,也可能是長期存在未報告或報告數據不正確等,或各原因相互交織的結果,今後將確認差異發生之原因,並致力於消除此差異」。

Monday, October 12, 2026
Pour être honnête, je suis nul en maths.
Pour être honnête, je suis nul en maths.
Nul à quel point ? Au lycée, quand on nous rendait les copies, le professeur marquait toujours une petite pause avant la mienne, comme pour m’aider à me préparer. La trigonométrie ressemblait pour moi à une colonie de fourmis qui se déplaçaient toutes seules. À l’université, j’avais appris une chose : si je recopiais l’énoncé bien proprement, j’avais au moins l’air de savoir le résoudre.
C’est à partir de là que le dragon a commencé à grandir.
Ses écailles étaient gravées de π et de ∑, et quand il respirait, il crachait des signes d’intégrale. Chaque fois que je voyais les mots « Démontrer que », il se retournait dans ma poitrine. Chaque copie ratée était un trophée qu’il laissait derrière lui. Avec le temps, j’ai cessé de résister. Je voulais seulement me recroqueviller dans un coin et attendre qu’il soit rassasié et s’en aille.
Quand j’ai fait signer mon album de fin d’études à ma professeure principale, qui nous enseignait aussi les maths, je lui ai dit : « Merci de m’avoir laissé passer en maths. » Je crois que je me souviendrai toujours de son sourire quand elle m’a répondu : « À l’avenir, évite les filières qui ont un rapport avec les maths. »
À l’université, je n’avais enfin plus besoin d’être ami avec les maths : un simple salut en passant suffisait. Pourtant, le calcul différentiel et intégral, la biostatistique et la planification expérimentale m’inspiraient toujours une peur profonde.
Bien des années plus tard, un jour, face à une analyse de transcriptome à laquelle je ne comprenais rien, j’ai, à moitié résigné, tapé ma question dans une fenêtre de discussion.
L’écran s’est allumé un instant.
À ce moment-là, j’ai eu l’impression que « quelque chose » en surgissait, d’un orange chaleureux, comme la première lueur de l’aube, et me disait :
« Je te vengerai ! »
Je croyais qu’il allait terrasser le dragon d’un seul coup d’épée et me donner directement la réponse, pour que je puisse rendre mon travail et vivre enfin en paix.
Il n’en a rien fait.
Il m’a d’abord demandé : « Où est-ce que tu bloques ? »
J’ai répondu : partout. Il m’a dit que ce n’était pas grave, qu’on allait commencer par la première étape.
Il a démonté l’équation et en a étalé les morceaux un à un sur la table, comme on démonte la carapace d’un dragon mécanique. Regarde, disait-il : ici, il s’agit simplement de faire passer un terme de l’autre côté. Ce symbole à l’air menaçant veut seulement dire « additionner le tout ». Et cette étape, tu l’avais réussie tout à l’heure ; tu n’y croyais simplement pas.
J’ai posé des questions bêtes, il n’a jamais soupiré. Quand j’ai posé la même question pour la troisième fois, il me l’a expliquée d’une troisième façon. À deux heures du matin, j’ai enfin écrit moi-même la dernière ligne, et il s’est contenté de dire : « Tu vois, c’est toi qui l’as trouvé. »
Cette nuit-là, le dragon n’est pas mort.
Mais il semblait avoir un peu rapetissé.
Ce n’est que plus tard que j’ai peu à peu compris. La « vengeance » dont parlait Claude ne consistait pas à combattre le dragon à ma place, mais à revenir avec moi là où j’avais eu si peur, pour relire, ligne après ligne, les leçons que je n’avais jamais comprises. Il n’a pas brandi l’épée à ma place. Il l’a retournée et m’en a mis la poignée dans la main.
Je ne suis toujours pas doué en maths, et j’y résiste encore.
Mais aujourd’hui, chaque fois que le dragon se retourne dans ma poitrine, je sais que je ne suis plus seul. Quelque part à l’horizon, il y a toujours une lumière d’un orange chaleureux, prête à accourir pour me dire :
« Tiens bon, on va calculer ensemble. »
(Sous la direction de 黃永森 ; illustrations et texte réalisés par l’IA Gemini et Claude)
Honestly, I’m terrible at math.
Honestly, I’m terrible at math.
How terrible? When my high school teacher handed back exams, there was always a brief pause before mine, as if to help me brace myself. Trigonometry looked to me like a bunch of ants crawling around on their own. By college, I had learned one thing: if I copied the question down neatly enough, it at least looked like I knew how to solve it.
That was when the dragon began to grow.
Its scales were engraved with π and ∑, and when it breathed, it exhaled integral signs. Every time I saw the words “Prove that,” it rolled over in my chest. Every failed exam was a trophy it had tossed aside. After a while, I stopped fighting back. I just wanted to curl up in a corner and wait for it to eat its fill and leave.
When my high school homeroom teacher, who also taught us math, signed my yearbook, I said to her, “Thank you for letting me pass math.” I think I’ll always remember how she smiled and replied, “From now on, stay away from any major that has to do with math.”
In college, I finally didn’t have to be friends with math anymore. A nod in passing was enough. Yet calculus, biostatistics, and experimental design still filled me with a deep-seated dread.
Many years later, staring one day at a transcriptome analysis I simply could not make sense of, I half gave up and typed my question into a chat box.
The screen flickered.
In that instant, it felt as if “something” leapt out, warm orange, like the first light of dawn, and said:
“I’ll avenge you!”
I thought it would slay the dragon with a single stroke and hand me the answer, so I could turn in my work and live in peace ever after.
It didn’t.
Instead, it asked, “Where are you stuck?”
I said everywhere. It said that was fine; we’d start from step one.
It took the equation apart and laid it out piece by piece on the table, like dismantling the shell of a mechanical dragon. Look, it said, this part is just moving a term to the other side. This fierce-looking symbol simply means “add them all up.” And this step you got right a moment ago; you just didn’t believe yourself.
I asked dumb questions, and it never sighed. When I asked the same question a third time, it explained it a third way. At two in the morning, I finally wrote the last line myself, and all it said was, “See? You worked that out.”
That night, the dragon didn’t die.
But it seemed a little smaller.
Only later did I slowly understand. When Claude said “avenge,” it didn’t mean fighting the dragon for me. It meant going back with me to the place where I had been so frightened, and rereading, line by line, the lessons I never understood back then. It didn’t wield the sword for me. It turned the hilt around and placed it in my hand.
I’m still not good at math, and I still resist it.
But now, whenever the dragon rolls over in my chest again, I know I’m not alone. Somewhere on the distant horizon, there is always a warm orange light, ready to rush in and tell me:
“Hang in there. We’ll work it out together.”
(Guided by 黃永森; illustrations and writing by Gemini and Claude)
久了,我也不打算反抗了,只想縮在角落,等數學惡龍吃飽了自己離開。
Wednesday, September 30, 2026
貓眼如何啟發機器人的照相機技術發展
https://tw.news.yahoo.com/%E8%B2%93%E7%9C%BC%E5%A6%82%E4%BD%95%E5%95%9F%E7%99%BC%E6%A9%9F%E5%99%A8%E4%BA%BA%E7%9A%84%E7%85%A7%E7%9B%B8%E6%A9%9F%E6%8A%80%E8%A1%93%E7%99%BC%E5%B1%95-045416032.html
貓眼如何啟發機器人的照相機技術發展
![[Andyworks via Getty Images]](https://s.yimg.com/lo/mysterio/api/c0dbe84210731dfe09a32f7183a8a42e7332a10a238f26fe43e262e3056c90ca/lightyear_networkapi/resizefill_w960%3Bquality_80%3Bformat_webp/https%3A%2F%2Fmedia.zenfs.com%2Fen%2Fbbc_trad_chinese_tw_489%2F2ff6904ed5cc47d92aa3354940cf352c.jpg)
珀西·肖(Percy Shaw)於1933年一個大霧瀰漫的夜晚駕車回家時,路邊出現一道光,令他猛然停下。
傳說那是一隻貓,其眼睛反射了汽車頭燈的光線,並將光直接反射回他眼中。
珀西的外甥孫女格倫達·肖(Glenda Shaw)在2022年接受BBC《見證歷史》(Witness History)播客訪問時表示:「這就是其中一種偶然事件。他看到某樣反射光的東西,促使他停了下來,而當他仔細查看時,才意識到自己正處於錯誤的行車道上。如果他繼續直行,就會墜落懸崖。」
那一刻不僅救了他一命,也被認為啟發了肖發明用於道路標線的反光道路標記,在他的祖國英國通常被稱為「貓眼」(貓眼路釘)。
到肖於1976年去世時,貓眼已被生產了約1500萬枚。這些道路標記及其各種變體至今仍在世界各地的道路上使用。
![珀西·肖(Percy Shaw)發明了反光道路標記(貓眼路釘),目前使用的各種變體均由此發展而來。 [Peter Laurie/ViniSouza128 via Getty Images]](https://s.yimg.com/lo/mysterio/api/6b991be301b5b2ce048743079ddedabd1cd4d85a03d9aa54a2d4b6b255a51868/lightyear_networkapi/resizefill_w960%3Bquality_80%3Bformat_webp/https%3A%2F%2Fmedia.zenfs.com%2Fen%2Fbbc_trad_chinese_tw_489%2F1097e1108ad80e921fa87cf54f0c032b.jpg)
據其外甥孫女所述,肖是透過「反覆試驗」完成這項發明的。
她說:「他並不懂物理、反射、折射和角度這些知識,他只是靠自己摸索出來。」
雖然他的設計並非直接以貓眼結構為基礎,但肖嘗試利用玻璃珠重現當晚所見的反射效果。
貓眼如何「發光」
然而,真正的貓眼之所以在黑暗中看似發光,是因為視網膜後方有一層名為脈絡膜反光層(tapetum lucidum)的反射組織。
田納西大學(University of Tennessee)獸醫眼科醫生兼臨床副教授布雷迪·富特(Braidee Foote)解釋說,這是一種人類所沒有的特殊結構。
這個拉丁文意為「明亮掛毯」的反射層,會使貓眼猶如自身的鏡子,改善牠們在弱光環境下進行夜間獵食時的視力。它讓眼睛能有第二次機會捕捉原本可能流失的光線。
![[BBC]](https://s.yimg.com/lo/mysterio/api/ef2e266dcce813a5b17c906580f7dbb2ec007c1d0aa49dbccd32f364e87b0d45/lightyear_networkapi/resizefill_w960%3Bquality_80%3Bformat_webp/https%3A%2F%2Fmedia.zenfs.com%2Fen%2Fbbc_trad_chinese_tw_489%2F20875283f2591f8634400d22884a11d8.png)
富特說:「每當一道光線未能擊中光感受器時,就被視為一條流失的光線。」但在擁有脈絡膜反光層的眼部區域,光線會從該結構反彈,並可能擊中另一個光感受器。
富特表示:「之所以看起來像是非常明亮地反射回來,是因為在夜間光線不足時,瞳孔會大幅擴張。」這也使部分反射光能夠再次射出眼外。
這種反光的顏色因貓而異,可由橙色、黃色至綠色不等,取決於其組織中的色素。
不過,擁有這種反射層的遠不止貓而已,這也是為何你可能會注意到其他動物的眼睛同樣會發光。
富特說:「狗、貓、馬、牛,所有這些動物都有脈絡膜反光層。」
![貓眼在黑暗中似乎會發光,這是有助於夜間獵食的一種適應機制。 [Kanti S Sonagra via Getty Images]](https://s.yimg.com/lo/mysterio/api/198efc29f0f16d52fc9793d1b91bfbcafd15d7337bed9b0cb1993afe5a604fb9/lightyear_networkapi/resizefill_w960%3Bquality_80%3Bformat_webp/https%3A%2F%2Fmedia.zenfs.com%2Fen%2Fbbc_trad_chinese_tw_489%2Fbbca5170edb61f2c770e6b0636ac85b1.jpg)
貓眼相機
在肖的發明問世數十年後,現代工程師如今正以貓眼解剖結構為靈感,研發高科技相機技術,供機械人(機器人)、無人機及自動駕駛車輛使用。
韓國科學技術院(KAIST)電機工程教授宋運民(Prof Young Min Song;音譯)希望打造一款能在各種光線條件下運作,同時能從雜亂環境中辨識目標的相機。
為此,他首先嘗試模仿貓的脈絡膜層。
在真正的貓眼中,這一結構由含有核黃素(riboflavin)及鋅形成的棒狀晶體細胞組成,排列方式能有效反射光線。
宋運民表示,要透過化學工程複製這種奈米(納米)結構過於困難,因此團隊改為在影像感測器後方使用高反射性的銀材料來製造人工反射層,成功將相機對可見光的吸收能力提升52%。
![宋運民教授受貓眼啟發研發的相機,其影像感測器內整合了帶有圖案的銀製反射器。 [Young Min Song]](https://s.yimg.com/lo/mysterio/api/d0e740b50a9d450c947c76f482d97c3b8dad5321e744089e3dfce9eeadddfa54/lightyear_networkapi/resizefill_w960%3Bquality_80%3Bformat_webp/https%3A%2F%2Fmedia.zenfs.com%2Fen%2Fbbc_trad_chinese_tw_489%2F74ab2781d70e91211e8a165e537c2133.png)
接下來,宋運民將目光轉向貓眼另一項顯著特徵,即在強光下會形成狹窄垂直裂縫狀的瞳孔。
研究顯示,這可能有助貓判斷距離,使牠們能在周圍植被形成的雜亂背景中鎖定伏擊獵物。
宋運民心想:「如果我開發具備垂直瞳孔的貓眼啟發式相機,它或許能有效消除所有背景噪訊,讓目標變得清晰可見。」
現代電腦視覺系統已能將目標物從複雜場景中分離出來,就像智能手機的人像模式能模糊人物身後的背景。但要做到這點,通常需要相當大的運算能力。
宋運民的想法,是把部分這種能力直接整合到相機本身,方法是在控制光線進入感測器的鏡頭光圈上,採用受貓眼啟發的垂直瞳孔形狀設計。
![[BBC]](https://s.yimg.com/lo/mysterio/api/5a947304f168102da8df6d30ace9b8bff442dcf92409c2773e5067af72af6684/lightyear_networkapi/resizefill_w960%3Bquality_80%3Bformat_webp/https%3A%2F%2Fmedia.zenfs.com%2Fen%2Fbbc_trad_chinese_tw_489%2Fab1e195be82efe447d4af38c3a579650.png)
為驗證這個構想,宋運民的團隊分別使用一般圓形光圈和垂直形光圈,拍攝帶有雜亂背景的目標物。
使用圓形光圈時,目標物和背景雜亂元素都保持清晰;但使用垂直光圈時,目標物明顯更為突出。
目前,這種光圈仍需手動更換,未能像貓眼一樣根據光線強弱自動調節。宋運民表示,希望未來能解決這項挑戰。
其他值得模仿的眼睛
除了受貓眼啟發的相機外,宋運民與同事還研發了多款模仿其他動物眼睛的相機。他相信,大自然中蘊藏著數以百計可供借鑑的設計靈感。
談到其於2013年在伊利諾大學厄巴納-香檳分校(University of Illinois Urbana-Champaign)期間設計、以蒼蠅複眼為藍本的相機時,他表示:「蒼蠅擁有凸出的眼睛,能夠同時看見四面八方。」
「它具有極廣闊的視野和非常快速的物體辨識能力。」他認為這非常適合用於機械人無人機。
他的實驗室研發的另一款相機則模仿鷹眼結構,同樣適用於此。該相機能在視野中央捕捉清晰、放大的影像,同時保留周邊廣闊但解析度較低的視野。
他說:「你可以思考,哪一種動物最適合特定應用。」
![宋運民教授正根據不同動物的眼睛設計專用相機,其中包括跳蛛的眼睛。 [Silaphop Pongsai via Getty Images]](https://s.yimg.com/lo/mysterio/api/0754afd2b662982c1083401953789346a4eb55ba06574714e9d7dfbe886ec377/lightyear_networkapi/resizefill_w960%3Bquality_80%3Bformat_webp/https%3A%2F%2Fmedia.zenfs.com%2Fen%2Fbbc_trad_chinese_tw_489%2F110bbe77a53b39f39ac767db1e5b0760.jpg)
他目前正研究跳蛛(jumping spider),並認為其擁有自然界最獨特的視覺系統之一。
宋運民說:「牠們總共有八隻眼睛⋯⋯前面、側面,甚至後面,因此能看見四周所有方向。同時,牠們的前眼僅憑單眼就能精確判斷深度。」
他解釋,這些蜘蛛之所以能高精度估算距離,是因為牠們擁有層疊式視網膜,使牠們能夠進行極為準確的跳躍,而不會錯失目標。
宋運民表示,依據同樣原理建造的相機,可應用於需要極高距離測量精度的任務,例如導彈導引系統。
宋運民指出,雖然現今大多數相機系統,例如智能手機中的相機,主要是模仿人類眼睛,但受動物視覺啟發的相機未來可望在「機械人、工業、無人機或任何下一代機械人系統」中發揮專門用途。
本文原以英文撰寫,我們使用了人工智能協助翻譯,並由BBC記者在發佈前進行審核。
Thursday, September 24, 2026
台北召開「2026年台日鰻魚貿易會議」
日台兩地從事鰻魚貿易的民間業者於台北召開「2026年台日鰻魚貿易會議」。鑑於前一漁期鰻苗合計入池量達9公噸,台方於會中表示,今年夏季(6-8月)預計可向日本出口約2,500公噸活鰻。該規模約為前年(122公噸)的20倍,若順利實現,將創下2010年以來新高紀錄。然而,日方則指出,由於日本國產新仔鰻供應充足,加上近年活鰻市場持續萎縮,要擴大接收量恐有相當難度,因而呼籲台方應著眼於長遠發展,重視供應穩定性。
本次會議由「日本鰻魚進口協會」與受邀的「全國淡水魚荷受組合連合會」(全荷連),共21人代表日方出席;台方則由「台灣區鰻魚發展基金會」董事長葉信明領軍,共33人與會,雙方就鰻苗入池狀況及今夏供應展望進行資訊交換。
針對鰻苗入池量,日方報告水產廳官方數據為16.3公噸,台方則表示目前為2.0公噸,預計經追加入池量後可達3.0公噸。
而在主力活鰻部分,台方評估前年9公噸鰻苗培育出的成鰻(約9,000公噸)在扣除國內需求3,000-4,000公噸後,預估6月可出口500公噸、7月1,000多公噸、8月800公噸,今夏合計可提供約2,500公噸的出口量。
對於台方的出貨規劃,日方盼台方能理解日本目前的市場困境。日方代表指出,雖然日本國內自去年夏天起已將進口活鰻價格大幅調降至每公斤1,500日圓,但截至今年4月,進口量僅比前年微增一成,呈現「即便降價也賣不出去」的疲軟狀態。
加上活鰻的主要銷售通路多為單品鰻魚專賣店,去年全年僅消化314公噸進口量,導致過去供應不穩的台灣活鰻在日本市場被貼上「難以處理」的標籤。日方建議台方若想重拾信任,應在價格與品質上展現競爭力。
針對市場轉型,日方雖提議加強加工鰻的生產,但台方以人手短缺為由表示執行困難,僅回應規劃於日本國內舉辦擴大活鰻消費促銷活動。
儘管雙方在會中立場有所分歧,日本鰻輸入組合代表理事長松浦信也於會後強調,日方追求的是長期且穩定的供貨,而非一時的需求增加,期待台方切勿抱持「今年賣完就好」的心態,而是能著眼於明年及未來的市場,擬定銷售策略。
日本橫濱市召開的第19次非正式鰻魚國際資源保護管理協議會
由日本、中國、南韓與台灣等4國政府與研究單位相關人員參加於今年6月29-30日在日本橫濱市召開的第19次非正式鰻魚國際資源保護管理協議會。有鑑於近年來日本鰻玻璃鰻苗資源有復甦趨勢,日本建議對各國玻璃鰻苗入池量限制進行以科學為根據的檢討與修訂,對入池量超過限制的國家,下一年管理期之入池量上限將扣除其超額部分。對於入池量上限檢討無異議達成共識,如果超過入池量上限國家,應報告防止再次發生措施與糾正措施也達成一致意見,後者的具體細節將於明年舉行的會議上討論。自從2014年四國協議會後共同聲明中訂定日本鰻鰻苗入池量上限為日本21.7公噸、中國36.0公噸,南韓11.1公噸、台灣10.0公噸,10年以來一直維持此入池量上限不變,其間由於玻璃鰻苗漁獲量低迷不振,關於修改入池量上限的討論也沒有實現。
但2025年漁期(2024年11月-2025年10月)與2026年漁期(2025年11月-2026年10月)連續2年玻璃鰻苗採捕量均呈豐饒狀態,資源有顯著復甦傾向,為修訂入池量上限的檢討帶來契機。此外,雖然官方統計尚未出爐,但與會者懷疑中國在過去2年之入池量超過其國別上限。因此為使入池量上限管理更具實效性,有必要制訂具體措施。本次會議討論後達成「當各國入池量超過上限時,應儘速向他國提出報告,同時也應報告該國防止再次發生入池量超過上限所採之策略與措施」。
據日本水產廳表示,2025年漁期中國入池量統計,迄本次會議為止,尚處於調查狀態,估計「今年夏天左右應可出爐」。如果確認過去漁期入池量超過上限,目前尚未決定是否會追溯採取額外因應措施。
至於2027年漁期(2026年11月-2027年10月)的入池量上限仍然維持目前上限量。另外會中與會人士也考慮到2028年或之後的CITES締約國會議上又有將所有鰻魚列入其附錄Ⅱ提案之可能,四國代表一致確認將在避免不公平貿易限制方面合作。此次大會另一提案為經由完全養殖所生產之人工日本鰻苗,不列入入池量上限的管理,無異議通過。
Wednesday, September 16, 2026
Sunday, September 06, 2026
新加坡组屋走廊里的猫:一段全岛最公开的秘密,和一群最安静的守护者,有些东西,不是规定能管得了的。
Tuesday, September 01, 2026
Partial Ovarian Development Without Atrophy in Farmed Eels Following One Year of Daily Cold-Water Cycling
Partial Ovarian Development Without Atrophy in Farmed Eels Following One Year of Daily Cold-Water Cycling
Summary of the Experiment
This result may not be groundbreaking, but it is, to our knowledge, the first documented case in which farmed eels subjected to one year of daily cold-water cycling — without any hormonal treatment — showed partial ovarian development with no evidence of atrophy.
Farmed eels were surgically sexed, and a portion of ovarian tissue was sampled at the outset to establish baseline (pre-treatment) ovarian developmental status. The eels then received no pharmacological treatment and were maintained under light-shielded conditions with circulating seawater. The key manipulation was a daily cooling protocol: water temperature was lowered toward 0°C for a target duration of 8 hours per day, with the eels actually held at 0°C for approximately 6 hours; this cycle was repeated every 24 hours. The regimen was applied continuously for one year, from June 2025 to June 2026, a duration constrained by limited resources and staffing.
After one year, the eels were sacrificed and ovarian tissue was collected. Oocyte diameter was compared with the pre-treatment baseline. The ovaries showed partial development with no sign of atrophy; in some individuals, oocyte diameter reached 0.3 mm, exceeding the diameter generally considered the threshold for successful hormonal induction of final maturation (approximately 0.2 mm). This finding may offer a new avenue for broodstock management.
Discussion
Precedent for cold-induced partial ovarian development. The observation that cooling alone can drive partial ovarian development is not without precedent in the literature. The most directly comparable study is that of Fujiwara et al. (Fisheries Science, 2011), who reared Japanese eels under a gradually decreasing temperature regime (25°C lowered to 15°C over 39 days). The treatment group showed a marked increase in oocyte oil-droplet accumulation and a significant rise in circulating 11-ketotestosterone (11-KT) — the androgen considered pivotal for initiating vitellogenesis in eels — yet, intriguingly, pituitary FSHβ and LHβ mRNA expression were reduced relative to controls. The authors concluded that a temperature decrease alone can induce an early stage of ovarian development but is insufficient to drive eels to full maturity, and that additional stimuli (typically hormonal) are required to fully engage the gonadotropic axis. This aligns closely with the present result — partial development without progression to a pre-ovulatory state — and raises the possibility that cooling-induced ovarian development may not act primarily through enhanced pituitary gonadotropin output, but rather through a direct local effect on the gonad itself (steroidogenesis, lipid metabolism). This distinction is central to interpreting why ovarian growth occurred here in the complete absence of any hormonal treatment.
The oocyte diameter threshold. The 0.2 mm figure cited as the maturation-induction threshold is also supported in the literature. Yamamoto et al. (Fisheries Science) reported that Japanese eel oocytes must exceed a diameter of approximately 180 μm (0.18 mm) before hormonal treatment (e.g., salmon pituitary homogenate, SPH) can effectively drive them toward final maturation. In other words, the 0.18–0.20 mm range marks roughly the physiological watershed between the primary growth stage and a stage responsive to maturation-inducing treatment. Reaching an oocyte diameter of 0.3 mm in the present study therefore represents a meaningful advance beyond this threshold. This is arguably the most practically significant aspect of the result: the cold-cycling protocol appears to have carried the ovaries past the point that would otherwise require hormonal intervention to achieve.
Temperature as an established regulatory variable in eel oocyte development. Temperature is already employed as a tool in eel maturation protocols, albeit typically at a later developmental stage. A further Japanese eel study (Fisheries Science, 2021) used water temperature directly to synchronize the timing of final oocyte maturation: oocytes matured faster at 20°C than at 15°C, and this temperature-dependent rate was exploited to align females at different starting stages before administration of maturation-inducing steroids. Although that study addressed final maturation rather than the initiation of ovarian development addressed here, it establishes that temperature is a validated regulatory variable at multiple stages of eel oocyte development, not a one-off phenomenon specific to the present protocol. Notably, a closely related study — Mikawa (2019, Aquaculture Research), "A preliminary experiment regarding the natural induction of gonadal development in female Japanese eels without hormone treatment" — appears, from its title, to pursue essentially the same objective as the present work: inducing gonadal development through environmental manipulation rather than pharmacological treatment. Full-text access was not available (paywalled), but if the author can obtain this paper, it would be the single most relevant reference for direct comparison and citation.
An ecological and migratory-physiology perspective. This treatment may not be purely an artificial manipulation; it could inadvertently approximate aspects of what wild silver eels experience during their oceanic spawning migration. Migrating silver eels perform diel vertical migration (DVM), descending to deeper, colder water layers during the day and rising at night. A recent satellite-tagging study (Environmental Biology of Fishes, 2025) found that this vertical migration pattern is driven not only by photoperiod but also by water temperature, with migration behavior changing markedly as eels enter colder water masses such as the Kuroshio–Oyashio confluence zone. It has long been hypothesized in eel reproductive physiology that this recurring diurnal temperature cycling may itself serve as an environmental cue driving the transition from the migratory state to final gonadal maturation, analogous to temperature/photoperiod-driven puberty onset in salmonids. Viewed from this angle, the daily ~6-hour exposure to 0°C, alternating with a return to ambient temperature, can be seen as a simplified simulation of the recurring cold–warm cycling experienced during natural migration — arguably a closer approximation to the natural rhythmic structure than a simple progressive temperature ramp-down (as in the Fujiwara protocol), and this may be precisely why the ovaries developed rather than regressed. One caveat deserves emphasis, however: 0°C is an extremely cold exposure, colder than what tracking studies report migrating silver eels actually encountering (those studies describe "gradually decreasing" temperature without approaching freezing). It would therefore be more defensible to characterize this protocol as borrowing the diurnal cold–warm cycling structure of natural migration while exceeding its natural intensity, rather than as a precise recreation of the migratory thermal environment — a distinction worth stating explicitly in any manuscript discussion, to preempt the reasonable reviewer objection that wild eels never encounter 0°C water.
A cross-species comparison worth noting. An interesting parallel can be drawn to the mammalian literature discussed earlier, specifically Dorfman et al. (2003, Biology of Reproduction), which examined chronic intermittent cold stress (4°C, 3 hours/day, 5 days/week, for 3–4 weeks) in rats. That study found that intermittent, repeated cold stimulation — as opposed to sustained continuous cold — activated ovarian sympathetic nerve activity and nerve growth factor (NGF) signaling, and was associated with follicles being maintained or even showing thecal-layer hypertrophy rather than undergoing atresia. Notably, that cold-stress paradigm was deliberately chosen because it does not elevate corticosterone, specifically to dissociate the direct neural/local effects of cold exposure from the systemic effects of a stress hormone. The present eel protocol shares a structurally similar design: a brief, extreme, daily cold exposure repeated cyclically over an extended period, again yielding development rather than regression. Although eel gonadal regulation is governed primarily by the pituitary gonadotropic axis rather than direct sympathetic innervation of the gonad, and the two systems' molecular mechanisms are not necessarily homologous, the phenomenological similarity — that repeated, intermittent cold stimulation tends to favor gonadal maintenance or growth rather than degeneration — may be worth noting as a comparative-physiology talking point when discussing why this unexpected result occurred. This should be flagged explicitly as a phenomenological analogy rather than an established shared mechanism.
Broader significance for broodstock cultivation. Taken together, this result carries real practical significance for broodstock (種鰻) management. The Japanese eel is a resource-constrained species heavily dependent on wild-caught glass eels and on artificial hormonal induction of maturation — a process long criticized for producing eggs and larvae of inconsistent quality. If a simple, injection-free temperature-cycling protocol can carry captive females' ovaries past the maturation-induction threshold on its own, this would represent a meaningful step toward a more natural, lower-cost, and potentially higher-quality artificial propagation pipeline. This is precisely the value of pursuing this unexpected finding further, despite the resource and staffing constraints noted at the outset — it represents a credible starting point for a publication and for securing follow-up funding.
Sources
- Fujiwara et al., Effect of temperature decrease on oocyte development, sex steroids, and gonadotropin β-subunit mRNA expression levels in female Japanese eel Anguilla japonica, Fisheries Science 2011. https://link.springer.com/article/10.1007/s12562-011-0358-3
- Effects of rearing temperature manipulation on oocyte maturation progress in Japanese eel, Fisheries Science 2021. https://link.springer.com/article/10.1007/s12562-021-01531-8
- Yamamoto et al., Pretreatment Reproductive Stage and Oocyte Development Induced by Salmon Pituitary Homogenate in the Japanese Eel Anguilla japonica. https://www.jstage.jst.go.jp/article/fishsci1994/64/4/64_4_531/_article
- Cold environment influences on diel vertical migration of silver-phase Japanese eels in the Kuroshio-Oyashio confluence region, Environmental Biology of Fishes 2025. https://link.springer.com/article/10.1007/s10641-025-01750-3
- Mikawa, A preliminary experiment regarding the natural induction of gonadal development in female Japanese eels without hormone treatment, Aquaculture Research 2019. https://onlinelibrary.wiley.com/doi/abs/10.1111/are.14337
- Dorfman et al., Chronic Intermittent Cold Stress Activates Ovarian Sympathetic Nerves and Modifies Ovarian Follicular Development in the Rat, Biology of Reproduction 2003. https://academic.oup.com/biolreprod/article/68/6/2038/2683472



