The complainers in the desert, the misonenim, were concerned over their meat.
Now the mixed multitude who were among them yielded to intense craving; so the children of Israel also wept again and said: "Who will give us meat to eat?" (Num. 11:4)But then, when reminiscing about the "good old days", their experience in Egypt, they said:
"We remember the fish which we ate freely in Egypt, the cucumbers, the melons, the leeks, the onions, and the garlic" (Num. 11:5).They demanded meat, but remembered being fed fish. Wouldn't you think that it is a bad argument to justify demanding meat by recalling how you once had something less than meat?
I did not see many commentators discuss this. (See the Divrei David and the "new" Pardes Yosef for their answers.) I thought that perhaps we can suggest that there is a hint here for the following halakhah. The Magen Avraham (249:6) quotes the Maharash from Lublin who holds that one should eat meat at the meal celebrating a circumcision (cf. Machatzis Ha-Shekel, ad loc.). Elsewhere, the Magen Avraham (552:2) rules that, at the final meal before Tisha B'Av where one may not eat meat, one may also not eat fish because sometimes fish is considered meat (cf. Yoreh De'ah 217:8). R. Matis Blum (Torah La-Da'as, vol. 4, pp. 35-36) suggests that this Magen Avraham is the source for people today eating fish (tuna, lox, etc.) at the meal for a circumcision rather than meat.
Perhaps a hint to this can be found in the above verses. When the misonenim complained that they wanted meat, and then recalled that they had eaten fish in Egypt, they were considering both fish and meat to be in the same category.