Introduction
Scientific names
Common names
Distinguishing features
Life history
The fishery
Handling and stowage
Processing
Composition and yield
Products from squid

Introduction

This note summarizes information on the biology of squids in UK waters, their distribution, capture and economic importance. Advice is given on the handling and processing of squid, its chilled and frozen storage life, and on the composition and yield of edible flesh. Much of the information also applies to species of squid imported from other parts of the world.

Scientific names

Squids are molluscs and belong to a class called cephalopods which also includes the octopus and cuttlefish. Molluscs such as cockles and whelks have shells, but in the squid the shell is modified and consists of a strip of cartilage, known as the pen, buried in the flesh. Two species, Loligo forbesi and Loligo vulgaris, constitute the bulk of the UK commercial catch, together with small numbers of Alloteuthis subulata. Other species sometimes encountered in UK waters are the Newfoundland squid, Illex illecebrosus, the hard squid, Todarodes sagittatus, and the soft squid, Todaropsis eblanae. The cuttlefish. Sepia officinalis, when it occurs in the UK catch, is included in squid landings for statistical purposes, although it is not a true squid.

Common names

The preferred name in the UK is squid; other names occasionally met with include inkfish, ink, sea arrow and calamari.

Foreign names

Danish	blaeksprutte	Japanese	ika
Dutch	inktvis	Norwegian	blekksprut
French	calmar, encornet	Portugese	lula
German	Kalmar	Spanish	calamare
Icelandic	smokkfisk, kolkrabbi	Swedish	bläckfisk, kalmar
Italian	calamaro	Turkish	lübje
		Yugoslav	lignja

Distinguishing features

Squid of the Loligo species have a blunt tail, and the fins or wings together form roughly a diamond shape. The length of the mantle can be up to 60 cm. Loligo forbesi cannot readily be distinguished from Loligo vulgaris; the only noticeable difference is in the arrangement of suckers on the tentacles.

The Alloteuthis species are generally smaller; they have a slender body and finely pointed tail, and the two fins together are roughly heart shaped. The length of the mantle is up to about 10 cm.

Todarodes sagittatus is a fleshy squid growing up to 2 kg in weight, and has a - broader fin outline than Alloleuthis as shown in the illustration; Todaropsis are smaller and softer to the touch than Todarodes, and are somewhat redder in colour than other squids, but are otherwise similar in appearance to Todarodes. The cuttlefish, Sepia officinalis, is rounded in shape, and has an internal strip of calcified bonelike material instead of the strip of cartilage found in the squids.

Loligo, Alloleuthis, Illex, Todaropsis, Todarodes, Sepia

Life history

The life history of squid in UK waters is not fully known. They are thought to live mainly in deep water on the Atlantic edge of the continental shelf, and to move inshore seasonally, probably in association with the breeding cycle. Squid grow fast; Loligo reach sexual maturity 1 year after hatching. The females spawn in then-second year, when the mantle reaches a length of up to 18 cm, and then die. The males reach a length of about 30 cm at the end of the first year, and can be 50 cm long when 2 years old. The life span of squid is seldom more than 2-3 years.

Squid feed on plankton after hatching, but the adults are active predators which feed on crustaceans, fish and other squid. Although some species drift with the ocean currents, the commercially important species are active swimmers and move rapidly through the water by jet propulsion; they contract the thick muscular wall of the mantle and expel water forcibly through the syphon.

The fishery

The potential sustainable world catch of all cephalopods from all continental shelves is estimated to be 8-12 million tonnes a year; if oceanic cephalopods are included, this figure is increased somewhere between 8 and 60 times. Much of this resource is unlikely to be fished commercially, because it is thinly scattered throughout the oceans, but nevertheless the cephalopods are believed to be a major and largely untapped source of marine protein.

Squid are found in waters all round the UK, and are landed in small amounts at most ports. The most prolific catching areas are south west Scotland, the Moray Firth, Rockall and Faroe. The squid fishery fluctuates from year to year, since in such a short lived species it is so much dependent on the success or failure of a particular breeding season. The squid fishery tends to be seasonal, coincident with the movement from deep water to inshore grounds. The fishing seasons are as follows.

North Sea, Moray Firth	September-November
Shetland	December-February
Rockall	June-August
Faroe, North west Scotland	All year, but most abundant in December
South west Scotland	October-December
English Channel	September-December

Squid are caught in UK waters mainly as a bycatch when trawling or seining for white fish; since squid tend to swim off the bottom, the best catches are obtained with midwater trawls or high headline bottom trawls. Nevertheless a high proportion of the smaller squids can readily escape through the meshes of a typical trawl.

Jigging is a method used for capturing squid in quantity in other parts of the world; the Japanese use a mechanical jigger with lights that attract the squid towards a number of lures moving ecccntrically through the water on a power driven belt. The squid attach themselves to the lures and are hauled from the water onto the deck of the fishing vessel. The method is unlikely to be readily adaptable to UK waters.

Handling and stowage

Squid are not normally gutted at sea: they are simply washed and packed in ice. They are more susceptible to damage than gutted white fish if not handled carefully; crushing, scuffing or tearing of the skin, and burst ink sacs are indicative of rough handling. Squid are left ungutted because many markets, particularly overseas, prefer them whole; the ink and the tentacles are often used along with the flesh of the mantle when preparing squid for eating. Stowage in boxes is generally better than bulk stowage because there is less risk of crushing and bursting the ink sac. There should be at least 1 part of ice to 3 parts of squid by weight.

Ungutted squid in ice keep in first class condition for up to 8 days; after that time the flesh begins to redden, musty odours develop, and the squid become inedible in 13-14 days. Ungutted squid stowed in chilled sea water keep in first class condition for 6 days, and become inedible after 9 days. The following scoring system can be used to assess the flavour of cooked squid after chilled storage of the raw material.

Score	Cooked flavour of squid	Days in ice
10	fresh, characteristic of shellfish, sweet, meaty	0-1
9	slight loss of freshness, creamy, sweet, meaty, metallic
8	slightly sweet, slightly meaty, creamy, milky	6-8
7	no sweetness, caramel
6	neutral	8-10
5	slightly sour
4	sour, musty, cabbage
3	slightly bitter, overripe cheese, oily, slight sulphide	13-14
2	bitter, sulphide
1	strongly bitter, putrid

Processing

Whole squid can be distributed chilled in ice or frozen. Squid for freezing should be of good quality, less than 7 days in ice and free from damage. They should be packed in cartons and frozen quickly. An air blast freezer is suitable; the cartons should be left open during freezing to keep freezing time short. Whole squid keep in good condition in cold storage at - 30°C for 9 months or more. More detailed information on the freezing and cold storage of fish is given in Advisory Notes 27 and 28.

The edible parts of squid are prepared in the following manner. The whole squid is washed, and the tentacles are cut off just in front of the eyes; these are retained, since they can be eaten once the suckers have been removed. The head is twisted and the mantle is squeezed whilst the head, pen and guts arc gently pulled out. The mantle can be left whole, with the gut cavity washed out, or it can be split and opened so that any remaining guts can be scraped or washed away.

The skin on the mantle can be peeled or scraped off; blanching in hot water at 25-30°C for about 15 seconds makes the skin easier to remove. Machinery for heading, gutting, skinning and cutting squid is available.

Composition and yield

The chemical composition of squid, Loligo vulgaris, is 78 per cent water, 15-19 per cent protein and 1-1-1-5 per cent fat. The energy value of the flesh is about 2 J/g. The yield of edible flesh from squid, 60-80 per cent including mantle, fins and tentacles, is higher than that from white fish. The only hard parts are the beak, the cartilaginous pen and the rings of cartilage in the suckers.

Products from squid

The main market for Loligo species landed in the UK is as whole squid for export; only a small amount is sold on the home market, together with some imported canned delicatessen products/Thus there is little incentive towards development of new squid products in the UK but outlets possibly worth pursuing include frozen packs of strips or rings of squid enrobed in batter, and paella or other seafood dishes containing pieces of squid meat. Todarodes sagittatus, at present discarded by UK fishermen when caught in the north east Atlantic, is probably an important underutilized species that could provide raw material for squid products.