Halakhah su Geremia 52:16

However, it seems clearly the case that what was understood based on the Talmudic source just quoted 'that it rises only once in seventy years,' implies that it is not found at all, only during the time that it surfaces, and afterwards it is not to be found at all. Yet, this is indeed doubtful, because we find in tractate Shabbat (26a) "'But Nevuzaradan, the captain of the guard, left of the poorest of the lad to be vinedressers (kormim) and husbandmen (yogbim)' (Jeremiah 52:16). Said Rav Yoseph; the vinedressers refer to those who harvest the Balsam from Ein Gedi until Ramah, and husbandmen refers to the netters of the Hillazon from the promontory of Tzur until Haifa." And Rashi, of blessed memory, explained that the word 'yogvim' (husbandmen) is etymologically related to the word 'yekavim', ie. large vats, wherein they spread out the Hillazon in order to extract its blood, as is mentioned in chapter 'Klal Gadol' (Shabbat 75a) "That Nevuzaradan left them be (ie. the vinedressers and husbandmen) for the sake of the garments of the King," see there. And if we go according to his understanding, of blessed memory, (of Rabbi David Pardo) that the Hillazon itself is only to be found at the time that it rises from the sea once in seventy years, and afterwards is not found at all, we would not be able to understand Nevuzaradan's having left them there for something that occurred only once in seventy years. Also, the expression 'the netters of the Hillazon' implies that that was always their occupation. Thus it seems clear that the Hillazon itself was also always available and was always able to be netted. And regarding what it says 'that it surfaces once in seventy years' the meaning of this is that once in seventy years it surfaces and multiplies, but afterwards, although it is also found, it is not found in such great abundance. And if so, Rav Yose's question 'is it to be found' needs explanation. For although it is not found in such great abundance so that everyone can acquire it easily, still, it should be acquirable by skilled netters who are expert in the art of netting to capture it.