This document provides an overview of fish and shellfish, including their composition, market forms, handling, storage, and classification. It discusses that fish are divided into fin fish and shellfish, and describes the protein, fat, water and mineral content of fish flesh. Various ways of cutting, dressing, filleting and portioning fish are illustrated. Guidelines are provided for checking fish freshness and properly storing fresh, frozen and processed fish and shellfish. Mollusks and crustaceans are classified and examples are given.

1. Chapter 7
Understanding Fish and Shellfish
Copyright © 2011 by John Wiley & Sons, Inc. All Rights Reserved

2. Understanding Fish and Shellfish
Fish products are divided into two categories:
• Fin fish, or fish with fins and internal skeletons.
• Shellfish, or fish with external shells but no internal
bone structure.
2

3. Composition and Structure
The edible flesh of fish consists of:
• Water
• Proteins
• Fats
• Small amounts of minerals, vitamins, and other
substances
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4. Composition and Structure
Fish has very little connective tissue.
• This means that:
• Fish cooks very quickly.
• Fish is naturally tender.
• Moist-heat cooking methods are used not to create tenderness
but to preserve moistness.
• Cooked fish must be handled very carefully or it will fall apart.
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5. Special Problems in Cooking Fish
Cooking Fat Fish and Lean Fish
The fat content of fish ranges from 0.5% to 20%.
• Lean fish are those that are low in fat.
• Fat fish are those that are high in fat.
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6. Cutting Fish
Market Forms
Whole or round: completely Drawn: viscera removed.
intact, as caught.
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7. Cutting Fish
Market Forms
Dressed: viscera, scales, Steaks: cross-section slices,
head, tail and fins each containing a section of
removed. backbone.
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8. Cutting Fish
Market Forms
Fillets: boneless sides of Sticks or tranches: cross-
fish, with skin on or off. section slices of fillets.
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9. Cutting Fish
Market Forms
Butterflied Fillets: both sides of a fish still
joined.
9

10. Cutting Fish
Dressing a Fish
Scale the Fish. Cut off the tail and fins. Slit the belly and pull
Scissors are easiest to out the viscera. Rinse
use. the cavity.
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11. Cutting Fish
Dressing a Fish
Remove the head. Cut through The fish is dressed.
the flesh just behind gills. Cut
or break the backbone at the
cut and pull off the head.
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12. Cutting Fish
Filleting a Flatfish
Use a thin-bladed, flexible Make a cut from head to tail,
knife. Cut off the head just just to one side of the center
behind the gills (this step is line down to the backbone.
optional).
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13. Cutting Fish
Filleting a Flatfish
Turn the knife so it is almost Remove the fillet completely.
parallel to the table. Making
long, smooth cuts, cut
horizontally against the
backbone toward the outer edge
of the fish. Gently separate the
fillet from the bone. 13

14. Cutting Fish
Filleting a Round Fish
Cut into the top of the fish Cut under the flesh toward
along one side of the tail; the tail and detach the cut
detach the backbone from piece.
head to tail.
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15. Cutting Fish
Filleting a Round Fish
Cut along the curved rib bones and finish detaching the fillet
at the head. Turn the fish over and repeat to remove the
second fillet.
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16. Handling and Storage
Checklist for Fish Freshness
Overall appearance
• Good appearance
Clear slime
• Moist and pliable fins
Odor
• Fresh and mild with no off-odors
Eyes
• Clear, shiny and bulging
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17. Handling and Storage
Checklist for Fish Freshness
Gills
• Red or pink
Texture of flesh
• Firm; elastic
Scales
• Shiny; tight on skin
Belly cavity
• No belly burn; natural-colored flesh, pink or red along backbone
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18. Handling and Storage
Storing Fresh Fish
Objectives
2. To maintain temperature of 29° to 32°F (–2° to 0°C).
3. To keep the fish moist.
4. To prevent fish odors and flavors from transferring to
other foods.
5. To protect the delicate flesh from being bruised or
crushed.
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19. Handling and Storage
Storing Fresh Fish
Methods
• On crushed ice (preferred method):
• Use drip pans to allow for drainage of melted ice.
• Change ice daily.
• In refrigerated box at 29° to 32°F (–2° to 0°C):
• Use if crushed ice storage is not available or practical.
• Wrap all fish or leave in original moisture proof wrap.
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20. Handling and Storage
Storing Fresh Fish
Storage Time
• Fresh fish may be stored for 1 or 2 days. If it must be
kept longer, you may:
1. Wrap and freeze it immediately.
2. Cook and then refrigerate it for later use in recipes calling for
cooked fish.
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21. Handling and Storage
Frozen, Canned, and Other Processed Fish
Federal Inspection
In the United States, voluntary inspections are conducted
by:
3. The National Oceanic and Atmospheric Administration (NOAA).
4. The Department of Commerce.
• Promotes the safety of processed fish and shellfish.
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22. Handling and Storage
Frozen, Canned, and Other Processed Fish
Federal Inspection (cont’d)
3. Processors who wish to take part in the programs must
pay for the service.
4. They may then use official seals or marks on their
product packaging and in advertising.
• PUFI seal (Processed Under Federal Inspection)
• U.S. Grade A shield
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23. Handling and Storage
Frozen, Canned and Other Processed Fish
Thawing and Handling
• Frozen raw fish
• Thaw in refrigerator.
• Small pieces can be cooked from a frozen state.
• Fillets, or other portions to be breaded or prepared in some
other way before cooking, may be partially thawed.
• Handle thawed fish as you would fresh fish.
• Do not refreeze.
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24. Shellfish
Classification
There are two classifications of shellfish:
2. Mollusks: Soft sea animals that fall into three main
categories:
• Bivalves, which have a pair of hinged shells (such as clams
and oysters).
• Univalves, which have a single shell (such as abalone and
conch).
• Cephalopods (such as octopus, squid and cuttlefish).
3. Crustaceans: Animals with segmented shells and
jointed legs.
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25. Shellfish
Mollusks
Oysters Mussels
Clams Scallops
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26. Shellfish
Cephalapods
Squid
• Usually referred to on
menus by their Italian
name, calamari.
Octopus
• The name means “eight
feet.”
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27. Shellfish
Crustaceans
Lobster Shrimp
Crab 27