>On 16 November, Jay Harlow wrote:
>
>> Does anyone know offhand the number of pin bones in each of the common
>> salmonids -- Atlantic, chinook, coho, chum, pink, rainbow
>trout/steelhead? Is
>> it a fixed number per species/genus? How is the number related to the
>number
>> of ribs? I am also assuming that the number of pin bones is fixed by the
>time
>> the fish reach adult shape, and that they grow in size but not in number
>as
>> the fish grows. If anyone has this information at their fingertips, or
>can
>> refer me to where to look it up, I'd appreciate the help.
>
>I can give you a somewhat incomplete answer. Pin bones, referred to as
>'inter-muscular bones' in zoology textbooks, are usually associated with
>the pleural ribs, those that enclose the belly cavity, of a fish, though in
>some species they are associated with the vertebrae to which the pleural
>ribs are attached. I write 'associated' because they do not appear to be
>fused with the ribs or vertebrae, but connected by fibrous tissue. They are
>connected to about the first half, by number, of the ribs. The general
>textbooks of zoology I have do not go into detail so I looked in on a
>natural history museum to see what it had. There were mounted skeletons of
>a few species of fish. Because pin bones are not fused to the skeleton you
>cannot be certain that the taxidermist has recovered all of them. The most
>convincing was that of a perch with 9 pin bones, on each side, attached to
>the pleural ribs. The skeletons of cod and haddock had the pin bones
>attached to the pleural ribs by wire and I can't be sure that all the pin
>bones were present, but there were 9 and 11 bones in the haddock and cod
>respectively. There was a skeleton of the Atlantic salmon, Salmo salar, and
>in that species the pin bones are attached to the vertebrae. There were 12
>on each side, and 26 pairs of pleural ribs.
>
Only so few in Atlantic salmon? I am a bit surprised but there may be
different kinds of so called 'pin bones' in salmon. I can recall literally
dozens of them in Pink or Chum reaching a good 2/3 of the fillet length
towards the posterior. Soft, but firmly embedded in the connective tissue in
the 'loin' section of the fillet they constitute a major technological and
economical problem in processing beneless salmon products.
Best regards,
Andrew Strak
>If you need exact numbers I think you will have to determine them yourself.
>I suggest 3 possible methods. You won't need adult specimens; juveniles
>will do unless you want to confirm that pin bones in an adult are
>sufficiently large to be a nuisance. (1) Get a friendly vet to x-ray some
>fish. This is a very good method to show the orientation as well as the
>number. (2) Cut off fillets and digest the flesh with papain or pepsin.
>Recover and count the bones. (3) Soak a fillet in dilute alkali and the dye
>alizarin. The alkali clears the flesh and makes it translucent, and the
>alizarin stains the bones red. This is a rather messy method as the excess
>dye has to be washed out by leaching the fillet in dilute alkali. The first
>is the most convenient and satisfactory. The second works quite well and
>can be done in the kitchen - some casserole dishes, a supply of meat
>tenderiser papain, and a hot plate to warm the mixture up to about 50C. It
>is no good feeling for the bones in a fillet; you will miss the smaller
>ones towards the posterior.
>
>Peter Howgate
>
>