Sunday, August 29, 2021

Stimulatory Effects of Androgens on Eel Primary Ovarian Development - from Phenotypes to Genotypes

https://www.intechopen.com/online-first/78202

Stimulatory Effects of Androgens on Eel Primary Ovarian Development - from Phenotypes to Genotypes

Abstract

Androgens stimulate primary ovarian development in Vertebrate. Japanese eels underwent operation to sample the pre- and post-treated ovarian tissues from the same individual. Ovarian phenotypic or genotypic data were mined in a pair. A correlation between the initial ovarian status (determined by kernel density estimation (KDE), presented as a probability density of oocyte size) and the consequence of androgen (17MT) treatment (change in ovary) has been showed. The initial ovarian status appeared to be important to influence ovarian androgenic sensitivity. The initial ovary was important to the outcomes of androgen treatments, and ePAV (expression presence-absence variation) is existing in Japanese eel by analyze DEGs; core, unique, or accessory genes were identified, the sensitivities of initial ovaries were correlated with their gene expression profiles. We speculated the importance of genetic differential expression on the variations of phenotypes by 17MT, and transcriptomic approach seems to allow extracting multiple layers of genomic data.

Friday, August 13, 2021

鰻苗捕撈漁期管制規定簡介

保護棲地的配套管理

  因鰻苗之人工繁殖培育上有諸多瓶頸,所以目前市面鰻魚養殖戶之鰻苗均取自天然苗,也因為僅需簡單手抄網即可捕撈高單價鰻苗,所以也吸引許多民眾亦趁此短暫漁汛期間,與漁民爭相捕撈,造成來游的鰻苗資源遭受到極大的漁獲壓力。依據本會漁業署委託學者辦理研究計畫,顯示近年臺灣河川的鰻魚數量有普遍減少的現象,其原因仍不確定,但與全球氣候變遷以及大量捕撈鰻苗等因素,都有很大的關連,而為因應鰻魚資源日漸減少,保育工作則是刻不容緩。

  爰除了管制鰻苗捕撈,讓部分鰻苗得以溯河洄游成長,增裕鰻魚資源外,為了讓鰻苗成長為性成熟之成鰻,並使成鰻得以降河產卵,本會漁業署同時輔導 13 直轄市及縣(市)政府依漁業法規定公告轄屬至少一條河川之中下游流域,全年禁止以任何方式捕撈鰻魚 (禁捕鰻魚河川彙整如附圖) ,尤其宜蘭縣更公告全縣境內河川全流域禁止捕撈鰻魚,以進行鰻魚棲地保護工作。




Tuesday, August 10, 2021

「鯰魚效應」讓鰻魚0死亡?胡說八道

https://www.mirrormedia.mg/story/20170823bus004/?fbclid=IwAR1m2VaNr2bMm8KI0juZUEMnXp7OjV64CoW-9f8i__2MbydXwHvbLF-GMkM

活鰻搭飛機出口日本,如何保持0死亡率?江湖傳說指「在魚群中放幾條鯰魚,魚群為躲避鯰魚會不停游動,到埠時仍保持活跳跳狀態。」對此,「鰻魚女王」旺生企業董事長郭瓊英直言:「胡說八道!」在本刊追問下,她不藏私傳授活鰻運輸0死亡率的商業祕訣。

午夜12點,一輛載滿冰磚的卡車駛入旺生位在桃園市大園區的鰻魚包裝廠,司機掀開蓋住冰塊的帆布,用超大型鐵夾將大型冰磚卸貨至預備位置,空氣中頓時飄出一股寒意,這就是準備用來強迫鰻魚進入冬眠狀態的祕密武器。

當工人完成選別工作,正在休息室吃麵喝茶聊天,唯獨郭瓊英一人來回巡視選別池,只見大型水柱持續沖水,池中鰻魚像著了魔似地不停游竄,「鰻魚運輸能存活的訣竅就是空腹,透過沖水刺激,讓鰻魚一直處於運動狀態,把肚子裡飼料消耗掉或把髒東西吐出來,才能降低運輸的耗損率。」

清晨4點,工人即使睡眼迷濛,卻1分鐘也不敢多耽擱,趕緊將冰塊投入池中,為了增加和魚群接觸的表面積,還得持起超重木槌將冰塊擊碎,待8座選別池皆投入冰塊後,活鰻從不斷扭動身軀到呈半麻痺狀態;此時,眾人分工合作,有人折妥紙箱、有人搬來氧氣筒、有人持電鋸將冰磚切成15公分大小立方體。

被冰塊凍暈的鰻魚,暫時失去活力。
工人持電鋸將大型冰磚切成適當大小備用。
撈起的鰻魚持續使用冰塊冰鎮。
被冰塊凍暈的鰻魚,暫時失去活力。
工人持電鋸將大型冰磚切成適當大小備用。

一切準備工作就緒後,包裝產線正式啟動,2位工人進入激「凍」池,將呈現半暈麻痺的鰻魚撈進大水桶,接著磅重、裝入大型透明塑膠袋,郭瓊英站在最核心位置,拿著勺子舀起一杓預切冰塊磚水放入裝滿鰻魚的塑膠袋,才交給員工打入氧氣,最後封口裝箱。

「鰻魚在進入冬眠狀態時,所需的氧氣最少,冰塊的量要維持到運輸至國外,當冰磚化掉後鰻魚也剛好甦醒。」突然有員工貪圖方便,將還未裝入紙箱的鰻魚袋暫放地面,郭瓊英急得大聲制止,「地板溫度較高,會加速袋內冰塊融化速度,這樣是撐不到日本的,要講幾次?怎麼可以這麼不小心!」

在袋中打入氧氣,延續鰻魚生命。
郭瓊英親自掌杓,將裝袋鰻魚額外放入一杓冰塊水。
在袋中打入氧氣,延續鰻魚生命。
郭瓊英親自掌杓,將裝袋鰻魚額外放入一杓冰塊水。

正因為霎那間的功夫就能決定鰻魚「活」與「死」,為保護鰻魚,郭瓊英的焦急全寫在臉上,事後她忍不住自嘲:「在現場我就像個瘋子,但畢竟鰻魚是活的,稍有不慎牠們就會死亡,員工不一定這麼細心,每次看到危險的時候我就會很急,出貨就好像在打戰。」

早晨7點送抵桃園機場,準備搭第一班飛機出口日本。
一望無際準備放入包裝鰻魚的紙箱。
早晨7點送抵桃園機場,準備搭第一班飛機出口日本。
一望無際準備放入包裝鰻魚的紙箱。

包裝廠多是現場工作,郭瓊英投入鰻魚出口產業逾40年,至今仍堅持到廠坐鎮,「鰻魚一死亡就沒有價值了,沒價值就會虧錢,日本人相信我們(旺生),因為我們是有品牌的,不容許失誤,只要把這個態度傳達下去,所有人都戰戰兢兢。」、「我是巨蟹座的人,非常謹慎,交給別人我不放心,寧願親力親為。」鰻魚女王以身作則,也是旺生立足日本商界的關鍵原因。

European eel population at risk of collapse

https://science.sciencemag.org/content/372/6548/1271.1

European eel population at risk of collapse

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Science  18 Jun 2021:
Vol. 372, Issue 6548, pp. 1271
DOI: 10.1126/science.abj3359

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Animal Reproduction. Open access peer-reviewed Edited Volume

Animal Reproduction
Open access peer-reviewed Edited Volume
ISBN: 978-1-83969-515-5
eBook (PDF) ISBN: 978-1-83969-516-2




A good deal for healthy eels

Belgium (Brussels)

The Sustainable Eel Group (SEG) not only ensures that European eel populations stay healthy and able to fulfil their role in the aquatic environment, but they also support sustainable use for the benefit of local economies.

 

How do they do this? Through collaboration. As we know, most good things are accomplished not by single heroes, but by diverse stakeholders working together. In this case, it’s the scientific, conservation, and commercial sectors holding hands.

We might not typically spend a lot of time talking or thinking about eels and their troubles, so luckily, the SEG and many other stakeholders are taking on the three main challenges for the healthy survival of the European eel population – which like many other migratory fish, is critically endangered or locally extinct. And one of SEG’s goals is to get them off the endangered list.

Illegal trade, and more specifically, towards East Asia, has been on the rise in the past decades and even though this species has been listed in the Annex II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), under-reporting, poaching, and illegal trade have continued. It’s been said that illegal eel smuggling is more lucrative than trafficking cocaine because of the profit being determined by weight. 

Another big challenge for the eel population are man-made barriers. You might know of the great wildebeest migration across the Serengeti/Mara ecosystem, or the lake-to-lake flamingo migration in Tanzania. Similar to these and other migrations, where animals move in large numbers to new places to feed or breed, fish use rivers as natural highways for their migrations. The European eels use them to move from the rivers to the wetlands – that is, if they can. Unfortunately, they more often than not find man-made barriers, such as hydropower and water pumping stations, blocking their way. 

Sustainable Eel Group

Thanks to the EU-funded Project Amber, a comprehensive atlas of river barriers across Europe has been mapped, and over one million obstructions have been identified already. Apart from blocking their way, these barriers are also deadly – millions of fish are killed each year. Not only is this terrible news for the eel population, but also for us: the health of European rivers depends on these eels performing their vital tasks to keep our river ecosystems healthy. Among other roles, eels help to regulate the populations of other animals and they also play an important part in the food chain of larger fish and birds.

One of the many positive things Andrew Kerr and his team at SEG are up to is rewilding the eels. This normally involves the local fishermen and Andrew explains in a recent video that “the thing about fishing for them is you can assist the migration over the barrier, so you’re giving them a human-assisted 10-, 20-, 30-mile ride and then releasing them. We’re rewilding them above these barriers. This assistance will reduce the mortality substantially.” Andrew also explains that wetlands are the most important habitat for eels, because that is where they undergo their big transformation from a saltwater fish swimming in the sea to a freshwater fish swimming in rivers. He compares this process to the caterpillar-to-butterfly-metamorphosis we probably are more familiar with.

You might feel powerless if you don’t have influence to decrease trafficking or prevent more barriers from being built, but there is a way in which we can all be part of the solution rather than the problem. If you’ve ever tried to figure out the labelling on a product, you’ll know the complexity of standardisation, and the eel sector is no different. So the Sustainable Eel Group set out to provide a standard for a responsible eel sector that includes traceability from source to market. The SEG standard describes the standards to which those who trade in the European eel must comply if they wish to claim to be doing so responsibly, and we can be responsible consumers by only buying eel or eel products from sustainable producers.

In addition to the initiation and support of scientific research and conservation projects, SEG also coordinates the different players across the ecosystem. According to Andrew, collaboration is key. “Collaborative leadership – we’re trying to build links for a joined-up agenda.”

AtlasAction: Consume eel or eel products responsibly by informing yourself on the SEG standards and not supporting any producer or seller who doesn’t comply with these standards.

Written by

Zanri Kritzinger (16 July 2021)

    Bio

    Book-lover, sustainability-seeker, plant-eater, and curious learner. Manager of social impact projects and author of children’s books