Consider these situations:
1) You are shopping in King Soopers and you see a nice cut of salmon in the seafood department. Are you allowed to buy it for dinner? If so, is there anything you need to do before eating it?
2) Also at King Soopers is a cut of fish that the man behind the counter tells you is white fish, but the fins and scales have been removed. Are you allowed to buy it for dinner?
3) Why are fish and meat not allowed to be eaten together? Does the same apply to fish and milk?
Cooking and Eating Fish with Meat
הָהִיא בִּינִיתָא,
דְּאִיטְּווֹא בַּהֲדֵי בִּישְׂרָא.
אַסְרַהּ רָבָא מִפַּרְזִיקְיָא לְמֵיכְלַיהּ בְּכוּתָּחָא. מָר בַּר רַב אָשֵׁי אָמַר,
אֲפִילּוּ בְּמִילְחָא נָמֵי אֲסוּרָה,
מִשּׁוּם דְּקַשְׁיָא לְרֵיחָא
וּלְדָבָר אַחֵר.
צָרִיךְ לִזָּהֵר שֶׁלֹּא לֶאֱכֹל בָּשָׂר וְדָג בְּיַחַד, מִפְּנֵי שֶׁקָּשֶׁה לְצָרַעַת:
הָגָה:
וְכֵן, אֵין לִצְלוֹת בָּשָׂר עִם דָּג,
מִשּׁוּם רֵיחָא.
מִיהוּ, בְּדִיעֲבַד, אֵינוֹ אָסוּר
(ארוך כלל ל"ט דִּין כ"ה):
Star-K Website: (See link below)
"FISH AND MEAT ISSUES
One may not bake uncovered fish at the same time as uncovered meat or in a fleishig oven that is not clean. However, one may bake fish (even if uncovered, with or without liquid) in a clean meat oven or with covered meat. If one reheated uncovered challos in an oven at the same time as uncovered meat or chicken that has liquid (e.g. with gravy) then one may not, l’chatchila (initially), eat the challos with fish. However, one may re-heat challos in the same oven as a meat dish that is “dry” (e.g. baked chicken without sauce) and then l’chatchila eat the challos with fish. One should be extra cautious on Erev Shabbos, when there is a rush before lighting candles, not to heat uncovered items that may not be heated together."
https://www.star-k.org/articles/kashrus-kurrents/3704/oven-kashrus-101-using-the-same-oven-for-meat-dairy-fish-pareve/#:~:text=FISH%20AND%20MEAT%20ISSUES,oven%20or%20with%20covered%20meat
| Fish | Meat | Oven | Result |
| Uncovered | Uncovered | Not allowed | |
| Uncovered | Unclean | Not allowed | |
| Uncovered | Covered | Allowed | |
| Uncovered | Clean | Allowed |
Eating Meat After Fish
בֵּין בָּשָׂר לְדָגִים,
חוֹבָה לִטֹּל,
מִשּׁוּם דְּקָשָׁה לְדָבָר אַחֵר,
וַחֲמִירָא סַכַּנְתָּא מֵאִסּוּרָא
(ועי' י"ד סִי' קי"ז):
יִרְחֹץ יָדָיו בֵּין בָּשָׂר לְדָג,
וְיֹאכַל פַּת שָׁרוּי בֵּנְתַיִם,
כְּדֵי לִרְחֹץ פִּיו.
הָגָה:
וְיֵשׁ אוֹמְרִים דְאֵין לָחוּשׁ לָזֶה,
רַק כְּשֶׁמְּבַשְּׁלָם יַחַד, וַאֲכָלָן.
אֲבָל לְאָכְלָן זֶה אַחַר זֶה, אֵין לָחוּשׁ (הַגָּהוֹת מָרְדְּכַי).
וְכֵן נוֹהֲגִין, שֶׁלֹּא לִרְחֹץ הַפֶּה, וְלֹא הַיָּדַיִם, בֵּינֵיהֶם.
וּמִכָּל מָקוֹם, יֵשׁ לֶאֱכֹל דָּבָר בֵּינֵיהֶם, וְלִשְׁתּוֹת,
דְהֶוֵי קִנּוּחַ וְהַדָּחָה.
(הגהות ש"ד סי' ע"ה ומביאו בגליון או"ה שם)
דְּקָשָׁה לְדָבָר אַחֵר.
וְאֶפְשָׁר דְּבִזְמָן הַזֶּה אֵין סַכָּנָה כָּל כָּךְ,
דְּחָזֵינַן כַּמָּה דְּבָרִים הַמֻּזְכָּרִים בִּגְמָרָא
שֶׁהֵם סַכָּנָה לְרוּחַ רָעָה וּשְׁאָר דְּבָרִים,
וְהָאִדָּנָא אֵינוֹ מַזִּיק,
דְּנִשְׁתַּנּוּ הַטִּבְעִיּוֹת,
וְגַם הַכֹּל לְפִי טֶבַע הָאֲרָצוֹת.
וְעַיֵּן בְּיוֹרֶה דֵּעָה סִימַן שט"ז סְעִיף ג
וּבְאֶבֶן הַעֶזֶר סִימָן קנ"ו
וכ"כ הב"ח בְּשֵׁם הָרַמְבָּ"ם:
From the Star K Website: (See link below)
"If a person ate fish and would like to eat meat, or if he ate meat and would like to eat fish, he is required to take certain actions. The Shulchan Aruch states that he must wash his hands, but according to the Rema it is not Ashkenzai practice to do so. He must cleanse his palate by both eating another food and drinking something, or at the very least drinking something. If half an hour has passed since he ate the first food, it is not necessary to do so."
https://www.star-k.org/articles/kashrus-kurrents/5152/insights-from-the-institute-7/#4
Eating Fish and Milk
דָּגִים וַחֲגָבִים, מֻתָּר לְאָכְלָן בְּחָלָב,
רֵישׁ פֶּרֶק כָּל הַבָּשָׂר (קג:):
"אָסוּר לְבַשֵּׁל בְּחָלָב,
חוּץ מִבָּשָּׂר דָּגִים וַחֲגָבִים."
וְכָתַב הָרָ"ן, דְּכֵיוָן דִּלְבָשְׁלָן שָׂרִי,
מַשְׁמָע דִּלְאָכְלָן בְּחָלָב נָמֵי שָׂרִי,
דְּאִסּוּר בָּשָׂר בְּחָלָב,
בְּלָשׁוֹן "בִּשּׁוּל" אַפְּקִיהָ רַחֲמָנָא.
וְכֵן כָּתַב הָרַמְבָּ"ם וְהָרַשְׁבָּ"א,
דִּלְאָכְלָם בְּחָלָב נָמֵי שָׂרִי.
וּמִכָּל מָקוֹם, אֵין לֶאֱכֹל בְּחָלָב,
מִפְּנֵי הַסַּכָּנָה,
כְּמוֹ שֶׁנִתְבָּאֵר בְּאוֹרַח חַיִים סֵימָן קע"ג:
From HalachaYomit.co.il: (See link below)
"... There are also those Poskim, including Maran Ha’Chida, who writes that even Maran Ha’Bet Yosef did not intend to prohibit eating fish with milk; rather, he meant to prohibit eating fish with meat. The words “fish with milk” that are written in the Bet Yosef are a typographical error. Thus, although in general we rule in accordance with the opinion of Maran Ha’Bet Yosef, nevertheless, one may indeed act leniently in this case."
... "Nevertheless, regarding eating fish with butter (which is not considered like actual milk as opposed to other dairy products), several Poskim have ruled leniently on this matter, even according to the Sephardic custom. Indeed, Hagaon Harav Abdullah Somech zt”l of Baghdad writes in his Sefer Zivchei Tzedek that the custom in his city was to permit frying fish in butter. Thus, those who customarily eat fish with butter may continue to observe this custom. Ashkenazi Jews customarily rule leniently on all of the above (including eating fish with milk or cheese) and they may indeed continue with their custom as well."
http://halachayomit.co.il/en/default.aspx?HalachaID=2370
What Makes Fish Kosher?
(יב) כֹּל אֲשֶׁר אֵֽין לוֹ סְנַפִּיר וְקַשְׂקֶשֶׂת בַּמָּיִם שֶׁקֶץ הוּא לָכֶֽם:
דין סימגי דגים ודגים מלוחים. ובו י' סעיפים:
סימני דגים מפורשים בתורה כל שיש לו סנפיר וקשקשת טהור וסנפיר הוא ששט בו וקשקשת הן הקליפות הקבועות בו: הגה ודוקא שהם נקלפים ביד או בכלי אבל אם אי אפשר לקלפן מעור הדג לא מקרי קשקשת (המ"מ פ"א דמ"א): ואפילו אין לו אלא סנפיר אחד וקשקשת אחד מותר ואפילו אין לו עתה ועתיד לגדלם לאחר זמן או שהיה לו בעודו במים והשירן מיד בעלותו ליבשה מותר (רמב"ם ספ"א מהמ"א ורי"ף ור"ן וה"ה): הגה וי"א דאין להתיר בקשקשת אחת רק כשהיא עומדת תחת לחייו או זנבו או סנפירו (הטור והרא"ש לדעת ב"י ור"ן וה"ה בשם רמב"ן) וטוב להחמיר:
(ב) יש מיני דגים שקשקשיהם דקים מאד ואינם נכרים ואם כרכוהו בבגד או נתנו אותו בכלי מלא מים ונמצאו קשקשים מותר:
(ג) כל שיש לו קשקשת יש לו סנפיר ויש שיש לו סנפיר ואין לו קשקשת לפיכך מצא חתיכת דג שיש לו קשקשת אין צריך לחזור אחר סנפיר מצא לו סנפיר לא יאכלנו עד שידע שיש לו קשקשת:
... והנה אבותנו ספרו לנו שזה כנ' או ס' שנה שרצה גדול הדור אחד להתיר דג אחד שנקרא בלשון אשכנז קוואפפע, מחמת שראה במיקראסקאפ, והוא זכוכית המגדיל, שיש לו קשקשין. ואיוש עליה כולא עלמא, ונפק שופרא דידהו לאיסורא ונשתקע ההיתר ... נראה לי דכל שאין נראה בלי זכוכית לא נקרא קשקשת. דצריך שיהיה לבוש, וזה אינה רק נקודה קטנה שלטא בו העין
Buying Kosher Fish in a Non-Kosher Store
Q:May I purchase a kosher fish from a non-kosher fish store?
A: Assuming you confirmed the fish was kosher (by seeing a scale removed or by recognition of the species of fish), the remaining concern would be the knives, board and gloves with which it is handled. Assuming they are all washed properly, it is permitted to purchase the fish. If the fish was cut with a dirty, non-kosher knife, one would need to wash it and pass the sharp side of a knife over it (maavir alav chudo shel sakin) in order to remove the non-kosher residue. (see Pischei Teshuva 96:5, b’shem Teshuvos Chavos Yair 179)
https://oukosher.org/halacha-yomis/may-i-purchase-a-kosher-fish-from-a-non-kosher-fish-store/
Q: When it comes to fish, such as salmon, does that need to be purchased at a kosher supermarket or can salmon also be purchased at a general supermarket?
A: There are two issues when purchasing raw, fresh fish.
Firstly, one must be sure the fish is, in fact, a kosher species. As a rule one may not rely on the name of the fish to make that determination as (a) in some cases multiple fish are referred to by the same name and (b) there is considerable fraud in the fish industry with one fish being passed off as another. Therefore, the only reliable method of determining that a fish is from a kosher species is by inspecting its scales to be sure that they are the type that can be removed from the fish without ripping any flesh. If the fish has no scales or you are unsure how to determine if the scales are "kosher", there is no way to know that the fish is from a kosher species. ***One notable exception is salmon, where the flesh-color is unique and is considered a clear identifying mark of the kosher, salmon fish. (*** See next two sources below - RLZ)
Secondly, the knives used to scale, eviscerate, fillet and/or cut the fish may have been previously used for non-kosher fish. If that were true, it is possible that some residue of the non-kosher fish is still on the knife and will transfer to the kosher fish. To avoid this issue it would be best to purchase cut fish from a kosher fish store, or at least to ask the store employees to clean the knife and work on a clean piece of butcher-paper. If neither of those are possible, there is basis to permit the purchase of packaged, pre-cut fish with the assumption that the store employees used the knife to cut many slices from the same kosher fish, and the non-kosher residue is likely not on the piece you chose. The worst-case scenario would be if the store would use a dirty knife to cut just one piece of kosher fish for you; in that case, you would have to scrub clean any surfaces that had been cut.
Of course, the above only applies to raw fish; fish which is cooked, smoked or otherwise processed requires proper kosher certification.
*** Interestingly, even though the claim is made that salmon is unique, the claim is questionable. In fact, there is a known fish manufacturer who holds the patented method to color other less expensive fish to look exactly like salmon. Another method of coloring trout red is to feed the fish carrots. In Mexico, it is a practice to soak fish in red color. The great posek Hador, R’ Moshe Feinstein, tz”l, writes in his responsa that the proper way to given kosher certification to fish productions is for the mashgiach to see every fish. Therefore, Star-K certified salmon, as well as all other fish varieties, have a mashigiach t’midi who examines every fish during production.
https://www.star-k.org/articles/articles/1115/the-tell-tail-sign/
Q: What about salmon? Is it true that the OU endorses buying salmon without skin and without a hashgacha?
A: Yes, the OU has researched various questions which have been presented over the years about the kashrut of salmon, and we still endorse the idea of buying skinless salmon. So long as the consumer is familiar with what salmon is supposed to look like, we are not concerned that another fish will be substituted for salmon which is not kosher. There are other fish which look very similar to salmon (some types of trout, arctic charr, etc.), but they are all kosher. We are not aware of any non-kosher fish which looks like salmon, and OU policy assumes that the red color is considered an acceptable indentifying mark for kosher. As such, the OU allows for salmon to be purchased without skin.
https://www.ou.org/news/ask_ou_kosher_may_2011_nothing_fishy_about_ou_fish_standards/