Once, tuna fishing thrived on the Pacific coast of the United States. Pioneered by adventurers straight out of the novels of Herman Melville and “Papa” Hemingway, it blossomed into a major industry, employing thousands and filling countless American lunchboxes.

Then came the dolphins.

Tuna and dolphins, it seems, travel together-the dolphins on the water’s surface and the tuna below. Inevitably, the nets used for tuna caught dolphins, as well. Could we allow Flipper such a painful demise? Soon, most tuna production had shifted to the Asian Pacific, and the American tuna industry was no more. Whatever the environmental and quality standards, the world’s tuna production was now in the hands of fishing industrialists in Thailand and the Philippines.

Enter the Rabbis.

In Vayikra (Leviticus) 11:9, the Torah says: “This may you eat of all that is in the waters: everything that has fins and scales.” The Talmud (Chulin 66b) states that, in fact, every fish with scales has fins, making scales the sole determining sign. But what exactly are kosher fish scales? After all, some reptiles also have scales.

Biologists identify four types of scales, two of which, cycloid and ctenoid, are found on kosher fish, such as tuna.

In the pre-industrial world, fish fresh from the monger were not skinned, and their species could be identified. Even absent the actual signs, as with an immature fish of a type that grows scales late in life, the fish’s kosher status would depend on its species. Only fish with the skin removed, and arriving with no clear sign of their species, demanded special measures such as constant supervision or an untouched seal with two separate Hebrew signs, indicating that it had been sent by a person trustworthy in Jewish law.

The Debate:

In 1962, prominent authority Rabbi Yosef Eliyahu Henkin wrote that without supervision from the beginning of production, consumers could not trust a can’s assertion that it contained tuna. However, many tuna brands were already certified kosher without such supervision.

In place of constant supervision, the best-known supervising agency arranged intermittent visits to factories abroad to check that production was according to kosher standards. As is the case with other areas of kosher supervision, it was assumed that fear of the supervisor’s appearance at any moment would motivate management and workers to prevent non-kosher fish from entering the production line. Despite these less-than-ideal conditions, widespread distribution of the tuna continued.

In the years following, Torah authorities from around the world, both Sefardi and Ashkenazi, in Israel and the Diaspora, joined in demanding constant supervision. In 1977 and 1984, the highly respected Rabbi Moshe Feinstein entered the discussion, outlining the reasons for this exceptional vigilance.

Finding it unfeasible to identify a fish as kosher without overt signs, Rabbi Feinstein insisted that a reliable kosher supervisor examine every fish before skinning. The large volume of industrial fishing, he said, makes it certain that non-kosher fish will be present in the nets. Intermittent visits, even if sufficiently frequent and surprising, would not serve their traditional purpose. At the speeds of a mechanized cannery, workers could expect any non-kosher fish to be gone before anyone would notice.

The function of supervision, Rabbi Feinstein wrote, is not to make life difficult for the producer in order to reduce the percentage of non-kosher fish to an acceptably insignificant level. Supervision, he explained, is testimony; it indicates that a reliable witness has seen production and can testify that the contents are kosher.

While certain agencies (including OK Kosher Certification) followed Rabbi Feinstein’s guidelines, in most tuna supervision, upgrades were slow in coming.

In 1988, the controversy bubbled over in rabbinic journals. Arguments for and against constant supervision were passionately presented. Most leading rabbinic authorities favored constant supervision. However, invoking the classic talmudic principle that a tradesman will not jeopardize his reputation, Rabbi Tzvi Schacter asserted that since it is in the fisherman’s business interest to deliver albacore tuna, for example, to the factory, he would surely allow only albacore to remain among his catch. And in the name of “quality control,” the factory would check again before skinning the fish.

Have we reached a stalemate? Perhaps. Yet, by his own admission, Rabbi Schacter’s position rests on the assumption that virtually no non-kosher fish slip through quality control. Kosher supervisors tell another story, and undeniable gaffes in the intervening years, such as octopus and clams in tuna cans, cast doubt on his premise. Much more problematic (as the Talmud cautions and ichthyologists corroborate), appearance and taste do not always reveal the identity of a fish fillet. Without our eyes wide open, we cannot know what we have received.

The market may take care of itself, but does it take care of kashrut? How deep is a producer’s commitment to quality control? I once heard the following anecdote: A supervisor arrived late to a Philippine factory for a kosher production run. Discarding the fish processed prior to the supervisor’s arrival, the plant manager remarked: “Really, rabbi…would it be so terrible if someone ate a bit of catfish?”