Observing a strict Kosher diet often involves avoiding foods that the non-religious person can enjoy. Kosher, which means 'fit', as in 'fit to eat', involves a series of rules concerning how food can be prepared, how it is cooked, and how it should be obtained. Some foods are prohibited, and this includes a number of seafood dishes, essentially food from the sea which does not have fins or scales. Shellfish, squid and mussels are not types of kosher seafood, for example, and neither is Monkfish, a type of fish that is without scales. In addition, the scales must be finger-nail like, and be removed without damaging the skin. Sturgeon, a scaled fish, will not be Kosher as its scales can't be removed in this way. Sharks, although covered in armour, also do not have scales. However, tuna, with its small number of scales, does qualify. This means that some fish which are widely available are restricted on the Kosher diet. http://www.aviglatt.com/Kosher-Seafood-Entrees-Dept/133/

1. http://www.aviglatt.com/Kosher-Seafood-Entrees-Dept/133/

2. Observing a strict Kosher diet often involves
avoiding foods that the non-religious person
can enjoy.
Kosher, which means 'fit', as in 'fit to eat',
involves a series of rules concerning how
food can be prepared, how it is cooked, and
how it should be obtained.

3. Some foods are prohibited, and this includes a
number of seafood dishes, essentially food from
the sea which does not have fins or scales.
Shellfish, squid and mussels are not Kosher, for
example, and neither is Monkfish, a type of fish
that is without scales.

4. In addition, the scales must be finger-nail
like, and be removed without damaging the
skin. Sturgeon, a scaled fish, will not be
Kosher as its scales can't be removed in
this way.
Sharks, although covered in armour, also
do not have scales. However, tuna, with its
small number of scales, does qualify.
This means that some fish which are
widely available are restricted on the
Kosher diet.

5. In addition to observing the strict rule about
scales and fins, Jewish cooks also have to
be cautious about using fish which is not
Kosher for other reasons, Even though fish
with scales can be eaten,
the way that the fish is caught,
prepared and cooked will all effect
whether it is Kosher or not.
It is important to be sure
that the fish are caught
in a certified way, or that
the customer buys
from a store which is
officially Kosher.
Recently, there have
been some scandals
concerning fish
substitution, that is
replacing Kosher fish
with cheaper versions
which have not been
handled correctly. This is
a serious issue, and so
therefore it is very
important that customers
know that they are
getting the Kosher
seafood that they have
ordered.

6. Despite the restrictions on Kosher seafood, there are still a
lot of fish varieties which can be eaten by those following
the Kosher diet.
For example, most online stores will sell Kosher tuna,
that is fish which has been prepared according to the rules
of the Torah.
Canned fish, which is cooked, has to have the
involvement of a Jewish cook in the process, and so most
tinned Kosher tuna will have a label stating that it has been
prepared according to the requirements listed.
Kosher sardines are another canned fish which should
also bear this label.

7. Cooks who want to enjoy a non-restrictive
diet may also want to consider foods such
as Kosher sushi, prepared according to the
rules which require Jewish participation in
every stage of the preparation, from
wrapping to cooking. It is not always easy
to find pre-prepared foods which are
Kosher,
and so someone looking for this type of
food may wish to buy from a specialist
Kosher retailer.