Meet Satincus Marinus...Your Favorite Poisonous Fish
When providing signs/simanim for kosher fish the Torah tells us twice that a fish has to have fins and scales. Why the repetition?
The Mishna says that any fish that has scales will always have fins. Why would the Mishna risk making such a statement - if we were to find such a fish the Mishna's would lose its credibility! If it's true, why does the Torah have to say a fish needs fins and scales, it would suffice to just say that any fish with scales is kosher! It's to make the Torah bigger and more glorious! What kind of answer is this?
However, The Tosafot Yom Tov (Maadanei Yom Tov to Rosh, Chullin 68:5) records that a Rav Aharon HaRofei brought him a poisonous fish - Stinkus Marinus - which has four legs and no scales - even if the legs are fins then that would mean a kosher fish is poisonous and we know - דרכיה דרכי נועם - the Torah wouldn't tell us a poisonous fish is kosher!
What is the status of the scientific information provided by the Gemara - is it information conveyed to Moshe at Sinai or based on the then-contemporary scientific knowledge? Ein Yaakov, Rav Sherira Gaon, R' Avraham ben haRambam, Rav S.R. Hirsch, the Rivash.
Shiur provided courtesy of Torah Anytime