Fishy Business 魚有雷同，實屬……

Once in a while, you are supposed to have bought a particular type of fish or ordered it from a restaurant, but what you get may be different in terms of taste, texture etc. Normally this is just a relatively minor nuisance …

But in one of these whacky stories from Hong Kong, about 14 people complained over the last 6 months or so having consumed some ‘cod fish’ from a supermarket. Some of them even complained about excreting oil! The authorities were pretty puzzled, until they discovered that the ‘cod fish’ was not what it said to be, but rather a totally different type of fish called ‘oil fish’. This oil fish is normally not recommended for human consumption, and its main use is for extracting oil for industrial purposes.

(One of my colleagues remarked that, since we all don’t have a mechanical stomach, little wonder we can’t digest the industrial-grade oil …)

How the oil fish made it to the supermarket shelves was indeed a most interesting question. The supermarket did eventually offer a refund for the product in question, but not after a series of brainless comments, roughly in this order over the last 2 weeks:
‘Cod fish is the same as oil fish!’ (As if all of us are as stupid as them …)
‘We have put this information on the packaging: "Cod Fish (also known as Oil Fish)"’ (That’s probably enough to get them prosecuted for false labelling!)
‘Oh, we didn’t know that cod fish and oil fish were not the same.’ (Finally backtracking, better late than never …)
‘Our purchasing team had no way to tell which fish is which.’ (What do you employ THEM for?)

The supermarket bought the fish from an Indonesian exporter. The Indonesian authorities admitted that the fish was indeed mislabelled; at first they thought it was a mistake, then they claimed that someone paid (bribes?) to put on the wrong information.

And while this blame game/wrangling continues, it was further uncovered that the oil fish had been sold to sushi shops in Hong Kong and the rest of China under another, much glorified name (in the fine Chinese tradition of naming somewhat exotic foodstuffs). Then it was the turn of seafood merchants to complain about the confusing nomenclature and call on the government to establish a standardised list of names, so that everyone knows what exactly they are dealing with.

This is indeed not an uncommon problem encountering scientists!

Those who have studied biology would be aware that there is a system to classify each organism into the correct species, but it is not perfect. Since the system mainly relies on the external appearance and features of the organism, it may be difficult to distinguish between two species that look much alike (you may agree that telling different fishes apart can be tricky sometimes), or to decide whether a newly discovered organism belong to an existing species or not. Following the classification step is the naming. Most branches of science have an established system of naming/describing that is well adhered to, but there are always exceptions. The example most familiar to me, and one of the most notorious, is in the naming of genes in fruit flies, a model organism studied by countless geneticists. Those fruit fly geneticists love to name the genes according to the context of their experiment and their own penchant, so many of the same genes are known by multiple names. Doesn’t that sound familiar to the seafood merchants’ problem?

Appearances can be deceptive, so can be names. There’s always a red herring lurking in the fishmongers, in the lab, or wherever you name it – beware!

Post scriptum - According to this article, the poor cod fish is dwindling, not only in stock but also in size! Scientists postulate that the smaller size has evolved because the larger ones have all been caught, leaving behind the smaller ones, while being small has an added advantage of 'slipping through the net'. Perhaps there'll be a day when there's no more cod fish and we can no longer complain about oil fish - only if we could ever evolve a mechanical stomach to digest the oil!

也許你以前買魚或用膳時點了一客魚，吃過後覺得口味有點不對勁，才發現貨不對辦，吃了另一種魚，平時也算不上是一個嚴重的問題。

香港過去6個月有14個人，吃了從超市購買的「鱈魚」後不適，嚴重者竟吃到「漏油」！當局也不明其所然，直至查出所謂的「鱈魚」原來是「油魚」。油魚通常不建議人類食用，其用途在於提煉工業用油。

（我有個同事說，我們沒有機械胃，自然消化不了油魚的油份……）

那些油魚怎樣走進超市及百姓家，的確耐人尋味。超市雖已對問題魚作保償，但之前的反應卻令人懷疑其是否知道出錯，且聽其近兩星期，由當初至今的言論：
「鱈魚跟油魚根本是一樣。」（你當我們也像你一樣無腦嗎？）
「我們已在包裝註明『鱈魚（即油魚）』。」（你當心被控告誤導消費者！）
「我們根本不知鱈魚和油魚原來有分別。」（誑言後知到不妥，找下台階吧？）
「採購部的同事根本無法分辦。」（那他們的職責是甚麼？）

由於油魚從印尼採購，印尼當局也介入調查，發現標籤的確有誤，起初說有人出錯，後來說有人付錢給出口商要求更改標籤，究竟真相如何，且看日後分解。

最新發現，除超市外，香港及國內好些壽司店購入的「白肉豚」，原來也是油魚，可見改名功夫多厲害！海鮮商販也不滿目前海鮮名稱名目繁多，連他們也會混淆，要求政府推出一個統一名冊作準。

這一點倒會吸引科學家注意——他們也面對類似的問題！

念過生物學的，都會知道物種分類有一個系統性的做法，但系統不臻完美，一大原因是分類是以生物的外觀及特徵為基礎，遇上外貌相似的生物便不容易（買魚往往也有同一問題！），而發現新生物時，也得確定其是否屬於現有的分類之下。分類後便要命名，大部分研究領域都確立了好些命名準則，通常都會嚴格遵守，但凡事總有例外，我最熟悉、又最惱人的例子，就是果蠅基因的命名。果蠅乃基因學中一種最常用的模型生物，研究果蠅的學者，給基因命名時會因當時實驗的性質和個人喜好而定，所以同一個基因，往往有數個不同命名——那亦不是海鮮商販的抱怨嗎？

人不可貌相，「顧名思義」也不一定準，做任何事都記緊要金睛火眼，提防被人魚目混珠！

後記：鱈魚不祇買少見少，還買小見小！有報導引述研究員謂，以往過度捕魚，令較多體形較大的魚被捕獲，而體形小有助「漏網」，體形較小的魚於是便較多繁殖，以至體形如此進化。也許有朝一日，我們再沒鱈魚可吃，祇有油魚，唯有寄望屆時人類也進化出一個機械胃來消化油魚的油吧。