Grammar - Past Particicple一句

Killed for their fins, sharks are endangered. ~ 單從 grammar 角度看, 句子表面 structure 是無錯
sharks are endangered ~ main clause
Killed for their fins ~ past participle phrase, 個 subject 是 sharks

其實句子由下列兩個句子組成
(1) Sharks are killed for their fins.
(2) Sharks are endangered.

Killed for their fins, sharks are endangered. ~ 這個句子是錯, ”endangered” 不是這樣用.

endanger (transitive verb) = 危及; endangered 是 past tense and past participle.

Endangered 還可做形容詞, 有特別的解釋, “快要絕種的”, Most dictionaries list this adjective separately.

Endangered 作為 adjective 是用在 noun 前面, endangered species, endangered animals
例如. Shark is an endangered species.

只有少數英漢字典與上面兩位仁兄是用在 noun 後面
問題 endanger (verb) 不是解 “瀕於滅絕”, 解 “危及”
endangered 作 past participle 是解 “危及”, 但是你的句子意思是”瀕於滅絕”, 與 endangered species 有關.

Assume passive voice, “Sharks are endangered.”
轉回 active voice, “Something endangers the sharks.” ~ Usage 是錯
Many people ignore English collocations (i.e. acceptable objects of “endanger”)
endanger someone/some animals 純是 Chinese English. Sharks are endangered 也是.

endanger (危及) 後面的 object 多數是:~
life/health/security/environment/safety/wildlife/existence

例子: Smoking during pregnancy endangers your baby’s life.
不是 Smoking during pregnancy endangers your baby.

Another example:
Any raid or rescue operation would endanger lives of hostages.

你的老師說句子錯, 可能認為 sharks are killed, 何來 “危及” 或 變成 “endangered species”? It is only my wild guess. It is best in your interest to ask your teacher to elaborate on this issue.

假如你想問的是killed這past participle的phrase，基本上=
Being killed for their fins, sharks are endangered.
所以算沒有錯。
未知你老師所謂錯是否指沒有加being便算為句式上不完整(正規)的錯。
但是英語運用上，尤其是slogan(廣告或口號)都不會依足文法規則，有時寫法只需要讀的人(文化上)意會理解含意便可以了。因此你可在網上或一般的標題見到類同的句式。

求知就最好向老師查問錯在那裏，假如他也講不出實在的問題，或只是對比傳統英文文法或造句的規則而言，你自己也可以判斷一下他的英語造詣的有限或程度。

正常的英文句可能要寫成:
Sharks are endangered because they are being killed for their fins.
才算正確。
或者你把這句給老師看，他應該會覺得順眼很多，應該會讚你學識寫句子了。不過卻證明他不懂地道的英文phrasing。

Mis-related participles
Care should be taken in using this construction to make sure that the participles are correctly related. The word to which the participle relates should be the same as the subject of the verb. Thus in the following sentences the participles are correctly related:-
Being Japan Comics, we bought them all ! (Being=we bought.)
The Error and Correction should be:-eg:-
Being killed for their fins---(=as/because it was)
sharks (subject) were (verb) endangered.
Being=participle;
Hence :-Being killed for their fins, sharks were endangered.
(Since it was "sharks"who were "being killed", the participle is correctly related.)

Killing for their fins, sharks could be endangered.
(It was sharks who were being killed.)

Being cut&killed (for fins), the sharks were endangered to live as (a) species.
(It was the sharks who were being cut and killed.)
Compare the example with your given, in which the participle is wrongly related:-eg:-
We killed for their fins. Sharks are endangered !
These are two sentences.
However, they are cases where a participle may be found unattached and not logically related to the subject of the verb,when subject of the verb=sharks."We" is acting as another subject forming an independent sentence in construction of the second part of the second sentence.