Kingklip - of course it is Kosher
summarised from this article

Is the South African Kingklip (Genypterus capensis) Kosher or not?
The head of the Cape Beth Din's Kashrut department, Rabbi Desmond Maizels made the following observations at CAJE (the Johannesburg College of Adult Jewish Education)

The requirement for a fish to be kosher is that 'everything that has a fin and scale in the water is kosher'. Fish with scales have fins, and so scales are the main determinant. Scales that are well attached so that their removal tears the skin, are not Kosher. The traditional test is to roll the fish about in a cloth and look for the scales' shiny reflections in the cloth. Halacha imposes no minimum size or thickness for Kosher scales as long as it can be seen with the unaided eye, the fish is kosher.

A fish need have only one scale to be Kosher.

Kingklip scales are very difficult to find: they are small and very thin; they are covered by a membrane; and the entire fish is covered with a thick slime which saves if from being shredded as it swims between rocks.

However it does have Kosher scales which can always be found on the Kingklip's cheeks. Samples examined by an expert, were found to be cycloid i.e. Kosher scales.

Some think that Kingklip is not kosher because its scales cannot be detected by running a fingernail over its skin. This test although traditional, is not a requirement in Shulchan Aruch.

Rabbi Bakshi Doron, former Israeli Sephardi chief rabbi, suggested that since Kingklip looks a bit like an eel and most eels are not kosher, it is best to avoid confusion.

However, eels and kingklips are scientifically categorised in separate groups. The eel is in the anguilliformes order, while the Kingklip is in the perciformes order. They are not at all "related".

According to the South African Beth Din, the Kingklip is kosher. However, since there are some who still view Kingklip as being "problematic", it has been classified as "not Mehadrin" For those who are mehadrin, the question of whether utensils that have been used for Kingklip are kosher or not, depends on their personal rabbi's opinion.

Rabbi Maizels listed several fish from around the world which had "traditionally" been known as treif, but on re-examination have been identified as kosher and is confident that in due course Kingklip too will enjoy universal acceptance. "The only treif thing about Kigklip", Rabbi Maizels concluded, "is its outrageous price!".