Introduction
Measures of weight and volume
Densities and stowage rates
Physical composition of cod
Yields

Introduction

This leaflet includes such miscellaneous information as definitions of some common units of measurement in the fishing industry, densities and stowage factors for a number of forms of fish, fish products and ice, and some conversion factors for yields of fish products from raw material.

Many of the figures given are approximate, since stowage rates and yields, for instance, depend upon, among other things, size and condition of the fish and the method of processing. In addition, information on many species and products is missing from this leaflet, either because Torry has no figures, or because the figures available are so unreliable that to record them would be misleading.

Measures of weight and volume

Units of measurement peculiar to the fishing industry are given in detail on the next page, but first it is necessary to set out the tables of British weights and measures that form the basis of commercial transactions:

Avoirdupois Weight
16 ounces	=	1 pound
14 pounds	=	1 stone
28 pounds	=	1 quarter
112 pounds	=	1 hundredweight (cwt)
20 cwts	=	1 ton

Capacity - Dry Measure
20 ounces	=	1 pint
2 pints	=	1 quart
4 quarts	=	1 gallon
2 gallons	=	1 peck
4 pecks	=	1 bushel
8 bushels	=	1 quarter

The following are some of the more common units of weight and volume in general use in the fish trade:

Kit: (measure of weight) -

1 kit = 10 stones = 140 pounds
16 kits = 1 ton

The term ‘kit’ is also applied to other measures of weight ranging from 60 pounds to 12 stones that are used occasionally for certain species at some smaller ports, particularly in the West of England.

Cran: (measure of volume) -

1 cran = 37 gallons = 6·03 cubic feet

Basket: (measure of volume) -

As used at ports for the landing of herring.
4 baskets = 1 cran (1 basket holds approx. 7 stones herring)

The box is used both as a measure of weight and as a measure of volume: at quayside sale it may contain anything from 5 to 10 stones of white fish at different ports. Aberdeen, for example, weighs its fish into 8-stone lots in boxes, whereas Granton lands fish unweighed in boxes said to contain approximately 6 stones. Most British ports now define the amount of fish being sold in boxes by declaring the contents either as a measured or as an estimated weight in stones and pounds.

Herring are often sold in boxes that reputedly contain a declared fraction of the cran unit of measurement. Any such sale must, however, be a sale by weight. Usual sizes of box are those that reputedly contain one-quarter or one-sixth of a cran; less common are boxes reputedly holding one-third or one-fifth of a cran.

Barrel: (measure of volume) -

Statutory obligation to make barrels in Scotland to a prescribed size was removed in 1963, and herring barrels can now be of any size: it is likely however that barrels of the following size will continue to be used for some time:

1 herring barrel = 26 gallons
herring barrel = 13 gallons

The usual size of foreign barrel that is sometimes used in Britain holds about 100 kilos.

Bag: (measure of weight) -

For the sale of cockles and mussels in shell, a bag usually contains about 1 cwt of shellfish at most ports, but the contents can range from 7 to 10 stones depending upon the port and on whether or not the contents are weighed.

Bushel: (measure of volume) -

When used as a measure for the sale of sprats, a bushel contains about 56 pounds of fish.

Peck: (measure of volume) -

When used as a measure for shrimps, a peck contains about 10 to 14 pounds.

Densities and stowage rates

1. Fresh Fish		Density	Stowage Rate
Chilled fresh fish muscle		65·8 lb/ft3
Whole fresh herring in bulk		58·2 “	38·5 ft3/ton
Whole fresh mackerel in bulk		50·0 “	45 “
Whole fresh sprats in bulk		53·2 “	42 “
Whole fresh capelin in bulk		62·5 lb/ft3	36 ft3/ton
Whole fresh cod in bulk gutted		57·5 “	39 “
		(variable - depends on size of fish)
Whole gutted fresh cod in bulk with ice ( fish to ice by weight)		49·5 lb mixture/ft3	45 ft3/ton mixture
		33 lb fish/ft3	68 ft3/ton fish = 4·25 ft3/kit
Whole gutted fresh cod in bulk in ice (ratio as above) but including allowance for fishroom structure		32 lb fish/ft3	70 ft3/ton fish = 4·37 ft3/kit
Whole gutted fresh cod stowed in single layers on ice on shelves 9 in. apart (including allowance for structure)		14 lb fish/ft3	160 ft3/ton fish = 10 ft3/kit
Whole gutted fresh cod boxed in ice ( fish to ice by weight, and including allowance for space occupied by boxes in block stowage)		23 lb fish/ft3	96 ft3/ton fish = 6 ft3/kit *
		* (figure varies from 5·3 to 6·4 ft3/kit depending on ratio of the effective volume to external volume of box)
Fresh fillets in bulk		60 lb/ft3	37 ft3/ton
Fresh fillets, boxed with ice (enough ice for normal inland journey, and including allowance for box)		30 lb fish/ft3	75 ft3/ton fish
Fresh fish livers, roes or milts in bulk		62·5 lb/ft3	36 ft3/ton
2. Frozen Fish
Frozen whole gutted cod in large blocks - weight of fish within dimensions of the block		40 lb/ft3 (fish very loosely packed in block)
		55 lb/ft3 (very compact block)
avg.		48 lb/ft3
Frozen whole gutted cod in large blocks, including allowance for supporting structure, access, etc.		31 lb/ft3	72 ft3/ton fish = 4·5 ft3/kit
Frozen fillets in large blocks		55 to 60 lb/ft3	37 to 40 ft3/ton
Frozen fillets in large blocks, including allowance for packaging, structure, access, etc.		40 to 50 lb/ft3	45 to 56 ft3/ton
Frozen fillets or steaks in catering packs in master carton		50 to 60 lb/ft3	37 to 45 ft3/ton
Frozen fillets in consumer packs in master carton, with allowance for pallets, access, etc.		25 lb/ft3	90 ft3/ton
Frozen fish sticks in retail packs		25 to 30 lb/ft3	75 to 90 ft3/ton
Frozen whole gutted cod, stowed as single fish		25 to 30 lb/ft3	75 to 90 ft3/ton
Frozen whole gutted halibut:
	in wooden boxes	30 to 35 lb/ft3	65 to 75 ft3/ton
	stowed loose	38 lb/ft3	59 ft3/ton
Frozen whole salmon:
	stowed loose	33 to 35 lb/ft3	65 to 68 ft3/ton
	in wooden boxes		90 to 95 ft3/ton
Frozen shelled shrimp in blocks		45 to 55 lb/ft3	40 to 50 ft3/ton
Frozen shelled shrimp in blocks, including allowance for packing structure, etc.		37 to 45 lb/ft3	50 to 60 ft3/ton
Frozen breaded shrimp in consumer packs in master carton		25 to 30 lb/ft3	75 to 90 ft3/ton
3. Other Fish Products
Fish liver oil		58 lb/ft3	39 ft3/ton
Fish meal, loose ground		39 lb/ft3	58 ft3/ton
Fish meal unground		30 lb/ft3	75 ft3/ton
Fish meal, bagged in 1 cwt bags stacked 10 high			70 ft3/ton
Crawfish, canned in cartons			approx. 100 ft3/ton
Dried cod in hundredweight bales		37·5 lb/ft3	60 ft3/ton
Dried fish in wooden boxes (181 lbs gross wt)			100 ft3/ton
Salmon salted in barrels			45 to 50 ft3/ton
Kippers in 1 stone wooden boxes		31 lb/ft3	72 ft3/ton
		(approx. 24 pairs of average kippers = 1 stone)
Salt fish:
	in bags (218 lbs gross wt)		125 ft3/ton
	in wooden boxes (185 lbs gross wt)		50 ft3/ton
	in casks (720 lbs gross wt)		45 ft3/ton
	in kegs (90 lbs gross wt)		55 ft3/ton
4. Ice
Solid ice at 32° F		57·24 lb/ft3
Crushed block ice		40 lb/ft3	56 ft3/ton
Flake ice		30 lb/ft3	75 ft3/ton
Tube ice		34 lb/ft3	66 ft3/ton

Physical composition of cod

Approximate weights of component parts of the body are given as percentages both of the whole ungutted fish and of the gutted fish. Weights of liver, guts, roe, etc., can fluctuate enormously with season, ground, condition of fish and so on; these figures can do no more than provide a very rough guide to yields after say heading, or heading and gutting, etc.

Component	Percentage		Percentage
	whole weight		gutted weight
	range	avg.	range	avg.
Head		21%		25%
Guts	5-8%	7%	6-9%	8%
Liver	2-7%	5%	3-8%	5%	- removed
Roe	1-7%	4%	1-8%	5%
Backbone, etc.		14%		17%
Fins and lugs		10%		12%
Skin		3%		4%
Fillet, skinned		36%		42%
		100%		100% + 18% guts and liver

Yields

The following tables give figures for converting weight of whole fish to weight of fish product. The weight of whole fish is taken to be the weight as landed from iced stowage, that is gutted and with heads on, except for the following species, which are normally landed whole ungutted: herring, sprat, mackerel, pilchard, redfish, salmon, dogfish. It is assumed that filleting and processing are carried out to a good commercial standard.

1. Wet fillets:

To convert net landed weight of whole fish to equivalent weight as fillets:

Species		Multiply landed weight by
		Fillets without skin	Fillets with skin
Cod		0·42	0·47
Codling		0·40	0·44
Haddock
	(large)	0·42	0·47
	(small)	0·40	0·43
Whiting		0·38	0·44 (block fillets)
Hake		0·50	0·55
Ling		0·48	0·55
Plaice		0·35	0·52
Lemon sole		0·42	0·58
Catfish		0·35
Redfish		0·30	0·35
White fish generally		0·43	0·47
Herring:
	immature		0·57
	spent		0·55
	up to ripe		0·58
	to ripe		0·54
	to + ripe		0·51
	ripe		0·47
Herring generally			0·53

2. Wet steaks:

To convert net landed weight of whole fish to equivalent as steaks:

Species	Multiply landed weight by
Salmon	0·60 to 0·65
Halibut	0·70 to 0·75

3. Smoked fish:

To convert net landed weight of whole fish to weight of smoked product:

Smoked product	Multiply landed weight by
Cod fillet	0·32 to 0·35
Finnan haddock	0·50 to 0·60
Golden cutlet	0·25 to 0·30
Smokie	0·45 to 0·50
Kipper	0·65 to 0·70
Bloater	0·68 to 0·80
Red herring	0·60 to 0·62
Salmon sides	0·45 to 0·60 (depends very much on weight of roe in whole fish, and condition of fish).
Mackerel, hot smoked whole gutted	0·60
Eel, ditto	0·65 to 0·75

4. Salt fish:

To convert net landed weight of whole fish to equivalent weight of salted product:

Salted product		Multiply landed weight by
Dried salted split cod:
	light cure	0·24
	medium cure	0·26
	heavy cure	0·34
Wet (Green) salted split cod:
	light cure	0·60
	medium cure	0·56
	heavy cure	0·50

Note. - Above figures are based on Canadian products; Norway quotes figures from 0·37 to 0·43 for salted split cod yield, but amount of drying not known.

Herring: pickle cured

0·79 to 0·88 (depends on ratio fish to salt in barrel).

5. Frozen fish:

To convert from net landed weight of whole fish to equivalent weight of frozen product:

Frozen product	Multiply landed weight by
Skinless cod fillet	0·42	(Note: loss of weight during cold storage or during thawing is ignored).
Headless gutted cod	0·75
Whole fish, all spp.	1·00
Salmon steaks	0·65

Typical yield from a frozen, headless, gutted halibut cut up for steaks is as follows:

Steaks	74·5%
Bellies	7·25%
Tail chunks	1·25%
	83%

Sawdust	4·5%
Trimmings	6·75% (nape, tail fin, etc.).
Unaccounted for	5·75%
	100%

Loss as sawdust during cutting up of frozen fillets of cod for fish sticks is about 8 to 12% of weight of fillet.

6. By-products:

To convert weight of white fish raw material to weight of fish meal, multiply by 0·21.

7. Edible portion of miscellaneous species:

For those species for which the equivalent weight as fillets is either not available or not appropriate, conversion factors are given for the weight of the edible portion from the landed weight of the fish.

Species		Multiply landed weight by
Salmon		0·64
Sea trout		0·63
Brown trout		0·68
Eel		0·50 to 0·60
Perch		0·33
Pike		0·43
Angler		0·20 to 0·25 (meat only)
		0·33 (skinned tail)
Gurnard		0·40
Skate, ray, as wings		0·45
Dogfish		0·35 to 0·45
Conger		0·50
Crab		0·27 to 0·36
Lobster		0·44
Norway lobster
	whole	0·20 to 0·27
	unshelled tails	0·54 to 0·61
Shrimp, brown		0·30 to 0·40
Prawn		0·4
Oyster		0·11 to 0·17
Cockle		0·08 to 0·15
Winkle		0·23
Scallop		0·10 to 0·18
Mussel		0·08 to 0·20
Whelk		0·42