SYNOPSIS OF BIOLOGICAL DATA ON THE COMMON SHRIMP
Crangon crangon (Linnaeus, 1758)

Exposé synoptique sur la biologie de la crevette
Crangon crangon (Linnaeus, 1758)

Sinopsis sobre la biología del camarón
Crangon crangon (Linnaeus, 1758) (Contd.)

4 POPULATION

4.1 Structure

4.11 Sex ratio of the catch

Ehrenbaum (1890), Havinga (1930) and Lloyd and Yonge (1947) found relatively more males in zones of high salinities than in those of low salinities (Table VII).

Tiews (1954a) determined the sex ratio in industrial catches in order to establish the percentage of male shrimps, as males hardly reach edible size. More than 50 percent of the catches of small shrimps (30 to 50 mm in size) made in Büsum during 1951 consisted of males, of which only less than 5 percent would have reached edible size. The relatively high percentage of male shrimps is attributable to the age composition of these catches as shrimps of 30 to 50 mm size are composed of two male age groups (0 and 1-group) but of only one female age group (0-group) (Table VIII).

The catch of edible shrimps above 55 mm in length is almost exclusively composed of female shrimps (Meyer-Waarden and Tiews, 1957).

4.12 Age composition

Age at first capture

In Germany and Netherlands, where small shrimps are fished for utilization in shrimp flour production, the age at first capture is approximately six months. In countries where larger shrimps of over 50 mm size are fished mainly for human consumption, their age at first capture is approximately 1 year.

See section 3.43.

Age at maturity

According to Havinga (1930) and Lloyd and Yonge (1947) maturity is reached at a little less than two years; but according to Ehrenbaum (1890), Meyer-Waarden (1935 b), Nouvel-Van Rysselberge (1937), and Tiews (1954a) at approximately one year.

Maximum age

The maximum age of female C. crangon is given by Havinga (1930) as four years, by Lloyd and Yonge (1947) as five years, and by Tiews (1954a) as three years. Such old shrimps were found to be extremely rare and their percentage in catches was only 0.3 percent (Tiews, 1954a).

The maximum age of male C. crangon is given by Lloyd and Yonge (1947) as four years, and by Tiews (1954a) as a little more than two years.

4.13 Size composition

Length composition of the population as a whole

Havinga (1930), Meyer-Waarden (1935b) Lloyd and Yonge (1947), and Tiews (1954a) have given length frequency distributions of female Crangon populations; while Lloyd and Yonge (1947) also give data on male C. crangon in the Bristol Channel.

Variations with depth, distance off the coast, density, time of day, season

During autumn, when industrial catches of small shrimps are largest, they are obtained mainly from the shallower fishing grounds near the coast.

Size at first capture

Havinga (1930) gives the size at first capture as 20 mm, Meyer-Waarden (1935b) 15 mm, Tiews (1954a) 18 mm, and Kurc, Faure and Laurent (1965) 30 mm.

Size at maturity

The smallest size at maturity according to the different authors is given in Table IX.

According to Havinga (1930), Tiews (1954a), and Kurc, Faure and Laurent (1965a, 1965b) the majority of female C. crangon reach maturity at a length of approximately 52 mm. The size at first maturity, however, appears to be lower in the Baltic than in the North Sea.

Maximum size

The maximum size of female C. crangon was recorded as 91 mm by Havinga (1930) and as 95 mm by Tiews (1954a) while the maximum size of male C. crangon is 75 mm according to Havinga (1930) and 68 mm (Tiews, 1954a) and 60 mm (Boddeke, 1966b).

TABLE VII

Percentage of male shrimps in zones of highest (Z.H.S.) and of lowest salinity (Z.L.S.) in the Dollart and in the Jade (Ehrenbaum, 1890), in Zuidersee and Westerschelde (Havinga, 1930) and in the Bristol Channel and Severn Estuary (Lloyd and Yonge, 1947)

TABLE VIII

Percentage of male shrimps in the 30 to 50 mm size group in the catches off Büsum during 1951/52 (Tiews, 1954a)

TABLE IX

Smallest size at maturity

4.2 Abundance and density of population

4.21 Average abundance

Estimates of population size have not yet been made but studies in this field are carried out at the Institut für Küsten - und Binnenfischerei, Hamburg.

4.22 Changes in abundance

Changes caused by hydrographic conditions, food competition, predation, fluctuations and fishing

Tiews (1954b) found a positive correlation between the average catch of shrimps per trip and the water temperature: the higher the temperature (above 16°C) during the fishing season, July to September, the greater the catch per trip. An average difference of 1°C in the temperature resulted in an average increase of 100 kg catch per net per trip. It is the water temperature during late summer that greatly influences the total catch of the year in this area. Unfavourable temperature conditions in summer may have been the cause of the low catches in the Büsum fisheries during the years 1949, 1951, and 1952 (Figs. 12 and 13). The influence of predation on the changes in abundance, as found by Tiews (1965) is described in section 3.34.

4.23 Average density

Annual mean density

According to Tiews (1954b) the annual average shrimp catch (of all groups) per trip of the fishing fleet of Büsum during the years 1930 to 1952 was as follows (each trip corresponds to a fishing time of approximately 5 h):

TABLE X

Annual average shrimp catch/trip of the Büsum fishing fleet

+) During these years fishing with two nets was introduced in Büsum, while earlier the boats fished with one net only. Figures refer to the catch of one net. The size of nets was then a little smaller than in the previous years.

++) Data incomplete, since catches of small shrimps are not included.

Fig. 12 Relationship between water temperature of 4 temperature ranges (a - d) and average catch of shrimps per trip (1930 to 1939) in the Büsum area (Tiews, 1954b).

Fig. 13 Water temperature (A) and yield of shrimps per trip (B) given as monthly mean for a = 1930–1939, b= 1937 and c=1930 in the Büsum area. The dotted curves (β = 1937 and γ = 1930) are based on the water temperature - catch relationship found (Tiews, 1954b).

Density of adult females

The annual average catch per trip of edible shrimps (the size of which corresponds to that of adult females) of the Büsum fishing fleet for the years 1936 to 1951 (Tiews, 1953a, 1953b) was as follows (each trip corresponds to a fishing time of approximately 5 h):

TABLE XI

Annual average catch/trip of edible shrimps of the Büsum fishing fleet

+) During the years 1940 to 1947 fishing effort was very much reduced (1/5 to 1/7) and probably the catches were much more carefully sorted for obtaining all edible shrimps. Consequently these figures cannot directly be compared with those collected in the other years.

++) During these years fishing with two nets was introduced in Büsum. Figures refer to the catch of one net.

4.24 Changes in density

Seasonal variations in available stock

Tiews (1954b) gives the following seasonal variation of the average catch per trip of shrimps of all size groups of the entire fishing fleet of Büsum for the years 1930 to 1939 as follows (each trip corresponds to a fishing time of approximately 5 h).

Table XII

Seasonal variation of average catch/trip of shrimps of the Büsum fishing fleet

4.3 Natality and recruitment

4.31 Reproduction rates

Annual egg production rates

See section 3.15.

No calculations for whole population available.

4.32 Factors affecting reproduction

See sections 3.34 and 2.21.

4.33 Recruitment

Factors determining recruitment (growth, transformation, movements)

Since growth is related to temperature (Tiews, 1954a), the temperature conditions may influence the time and magnitude of recruitment to the fishery. Temperature appears also to have some influence on the displacement of year-classes over the fishing grounds (Tiews, 1954b).

Seasonal pattern of recruitment

The seasonal pattern of landings of small-sized shrimps on the German coast shows a major peak in August to September and a minor peak in April to May.

4.4 Mortality and morbidity

4.41 Mortality rates

Tiews (1965) found that loss caused by predation was several times greater than by fishing mortality.

Meixner (1967) found that during a total observation period of 1½ years only one out of 129 Crangon died during the various ecdyses, when individuals were kept separate, i.e. one of 1,028 recorded moultings failed to be successful. This indicates a moulting mortality of less than 1 percent and less than 1 per thousand if referred to the total number of moults.

High mortality due to cannibalism has been observed in C. crangon immediately after moulting, when individuals were kept together in aquaria (Tiews, 1954a).

4.42 Factors causing or affecting mortality

Predators

See section 3.34.

Direct effects of fishing

Intensity of fishing is known to be high, but fishing mortality rates have not been assessed.

4.6 The population in the community and the ecosystem

Species composition of the community and relative sizes of their population

Heidrich (1930), Wulff and Bückmann (1932) as well as Meyer-Waarden and Tiews (1965a, 1965b) have studied the catch composition of the German shrimp fishery. According to Meyer-Waarden and Tiews (1965a, 1965b) the most abundant fish species caught along with shrimps was the goby, with a total average catch amounting to 732 million individuals per annum during the years 1954 to 1960, followed by the plaice with 215 million. Herring, pipe fishes, common sole, smelt and dab were caught in the order of 80 to 50 million individuals; armed bullhead, whiting, sea snails, flounder and sprat in the order of 30 to 10 million, and finally the three-spined stickleback, eel-pout, eel, short-spined sea scorpion, cod, sand-eels, dragonet, solenette, gunell, anchovy, rocklings, gurnards and horse mackerel amounting to less than 10 million. Shore crab and swimming crab were found to range between 120 and 100 million individuals. All the fish and crustaceans caught along with the shrimp show distinct fluctuations in their abundance from year to year.

The industrial catches of the German shrimp fishery during the years under observation contained less than 10 percent of undersized protected fish mentioned in Annex II of the Fisheries Convention (1946).

In the years when the industrial catches were large, as in 1954, 1955 and 1957, the percentage of fish was low (about 5 percent), whereas when the shrimp catches were poor, as in 1960, the percentage of undersized fish was close to 10. In 1959, also the industrial shrimp catches included nearly 10 percent of fish, but this is attributable to the strong 1959 year-class of whiting that had immigrated to the German coastal waters increasing the normal catch of undersized protected fish (some 2,000 tons per annum) by about 50 percent.

Although the fishing effort in the German shrimp fishery has increased 3.5 to 4 times since 1930, no decrease in the density of population of young fish could be observed in the case of plaice and sole (Meyer-Waarden and Tiews, 1965a, 1965b).

Interrelations of the population of the species in the community and ecosystem; place in the food chain; trophic level, etc

C. crangon is the most important food of several fish species in the community (Tiews, 1965).

See section 3.34.

Type of fluctuations (cyclic and non-cyclic)

Fluctuations seem to be non-cyclic (Tiews, 1954b, 1965).

Changes in environmental factors and their effect on the population

See section 3.32 and 3.34.

5 EXPLOITATION

5.1 Fishing equipment

5.11 Gears

Present gear (type and size of twine, webbing, shape, assembly, size, mesh size)

The most common gear now used in the Crangon fishery is a pair of beam trawls.

The German shrimp trawl has been described fully by Meyer-Waarden and Tiews (1957) and von Brandt (1959).

The length of the iron tubular beams varies between 6 and 9 m, and the shoes have a height of 50 to 60 cm. The ground rope is armed with 32 to 36 wooden bobbins. The design of the net varies greatly. The total length of the net is 10 to 12 m, of which the cod end is 2.5 to 3 m.

Von Brandt (1959) described in detail a number of typical nets used in Husum, Tönning, Büsum, Friedrichskoog and Neuharlingersiel.

Formerly the nets were made of cotton, but at present synthetic materials are used. Twin beam trawls were introduced on the coast of Ostfriesland after 1930, and in Schleswig-Holstein in 1948 (Tiews, 1952). At present shrimp fishing in Germany is nearly exclusively carried out with two beam trawls.

The fishermen of Ostfriesland use small trial nets before setting the main gear. A description of a try-net is given by von Brandt (1959).

The Dutch shrimp fishery also used beam trawls of a similar type (Tesch and de Veen, 1938). This was also the case in the French fishery (Belloc, 1938) until recently, but now otter trawls yield the larger part of the catches. Only smaller boats with small engines of 20 to 25 hp are still using beam trawls. In Belgium beam trawls were in use (Verbrugghe, 1932), but were later replaced in most cases by the otter trawl. During recent years, however the Belgian fishermen changed over to beam trawls again, as they consider them more effective in the tidal areas where the shrimp fishery is carried out. The French shrimp otter trawl is described by Kurc, Faure, and Laurent (1965a) (Fig.14).

Kurc (1964), Kurc, Faure, and Laurent (1965b) described a new otter-trawl developed for shrimp fishing in the Gulf of Gascoyne, the so-called “Devismes modifié” type (Fig.14). The net is divided in two sections and has two cod ends with different mesh sizes. The small mesh of the upper section catches the shrimps which jump through the netting that separates the lower from the upper section. The lower cod end has larger mesh to allow any small fish caught to escape easily. Catches of undersized fish are thus considerably reduced.

The design of the two-section shrimp trawl has been modified and used recently in a Dutch model of a beam-trawl (Boddeke, 1965a, 1965b) (Fig. 15). According to Boddeke (1965a) by-catches can be reduced by one sixth by using this new type of beam trawl. But Tiews (1966), experimenting with the same net, did not obtain the same results when used over the German fishing grounds.

On the east coast of England the beam trawl is exclusively used for fishing brown and pink shrimps (Mistakidis, 1958). In the Thames area the otter trawl has been introduced recently. On the northwest coast in addition to the beam trawl, fishing of brown shrimps is done by push and shank nets, the latter being small trawls pulled by horse carts. In the Bristol Channel small quantities of brown and pink shrimps are taken in salmon putts and stall nets. However, approximately 90 percent, if not more, of the total landings are fished by the beam trawl. The length of the beam varies between 5.5 m and 7.3 m, depending on the overall length of the boat and the length of the shrimp net is usually one and a half times the length of the beam, their mesh size varying from 19 to 25 mm full mesh.

Changes in types of gear during the development of the fishery

On the German coast push nets and the shrimp basket used to be the common gear for catching shrimps, but today the latter has all but completely disappeared (Meyer-Waarden and Tiews, 1957).

A description of the shrimp basket and of another primitive shrimp fishing gear, the fyke net with wings (Fig. 16), is given by Meyer-Waarden (1931).

A more modern, but also disappearing gear in the German shrimp fishery is the shrimp stow net. While the shrimp basket is a fishing gear for the shallow and more sheltered fishing waters, the shrimp stow net is for the deeper creeks with more rapid currents. This net has been described by Meyer-Waarden (1931) and von Brandt (1959).

These stow nets can fish only either in the ebb or flood tide.

Fig. 14 French otter board shrimp trawl made of nylon, knotless, as used in Vendée, 12.20/16.60 m: (a) = classical type, (b) = the same net, but with second selection bag of the “Devismes”-type, as demonstrated on top (c) (Kurc, Faure and Laurent 1965b).

Fig. 15 New Dutch beam shrimp trawl with two bags (Boddeke, 1965b).

Fig. 16 German shrimp fyke net with wings (Meyer-Waarden, 1931).

Fig. 17 Modern German shrimp fishing vessel from Cuxhaven (Meyer-Waarden and Tiews, 1957). (Photo: Dr. Nolte)

This type of stow not has been modified to facilitate operation during both the tides, with a special hanging design that permits considerable increase of catching power. Nevertheless the modified gear is not widely used for shrimp fishing (Meyer-Waarden, 1931).

Henking (1927) described some beam trawls which are used in the Baltic Sea for fishing C. crangon. Shrimps are caught there only as bait for the cod fishery, since large shrimps are not abundant enough to sustain a large-scale shrimp fishery.

A description of the original “shrimp net” used in the neighbourhood of the Thames Estuary, prior to 1930–40, its modification in early 1850, and the introduction of the “four beam trawl” at the same period is given by Mistakidis (1960).

In early days horses were used for towing shrimp nets in Belgium (Verbrugghe, 1932) and England (Davis, cited by Schnakenbek, 1942). The Belgian shrimp trawl was kept open by a ground beam in the middle of which a stick was attached to keep the mouth of the net open.

Use of echosounding or fish detectors

Echosounding is used now in the German shrimp fishery, but Crangon cannot be detected on fish finders (sonar).

5.12 Boats

Type, Size, Power, Changes in types of boats during the development of the fishery

In the early days in Germany small wooden, open or covered, sailing boats were used for shrimp fishing. Motorization started around 1900 and by 1927 all shrimp fishing boats were powered (Tiews, 1953a).

Today the type of boat remains the same except in size, the length varying from 12 to 17 m and equipped with engines between 50 and 75 hp (Tiews 1965) (Fig. 17).

All boats are equipped with 50 litre oilfired boilers to cook the catch of edible shrimp immediately after hauling, sorting and cleaning the catch. Nearly all vessels are equipped with mechanical sieves for sieving the catches. Most of the vessels do not possess fish rooms. Only the larger ones have refrigerated fish rooms.

In the Netherlands shrimp vessels are larger than in Germany, up to 21 m long and having engines up to 150 hp. These boats fish shrimps during the winter also and much farther away from their home ports than the German fishing boats do. The average engine power has steadily increased from 45 hp in 1951 to 93 hp in 1962 (Boddeke, 1962a, 1962b, 1966a).

In France, small fishing vessels having engines from 40 to 80 hp are used for shrimp fishing (Kurc, Faure, and Laurent, 1965a).

5.2 Fishing areas

5.21 General geographic distribution

Geographic distribution

Crangon fishing, on commercial scale, is carried out along the entire coasts of Germany (North Sea coast), the Netherlands and Belgium, as well as on the east and west coasts of England, and in several areas on the French coast. There appears to be some prospects for Crangon fishing on the Danish North Sea coast, at least in the southern area. However, this is not exploited by the Danish fishing industry.

5.22 Geographic ranges

Distances from coast

Crangon fishing is pursued close to the coast, the fishing areas varying in distance from half to 20 n mi (37 km), depending on their location.

Drainage basins

The fishing areas are usually within or close to estuaries.

Areas of greatest abundance (political or geographical designations or degrees of latitude and longitude)

Areas of greatest abundance are the entire coasts of Germany and the Netherlands.

Meyer-Waarden and Tiews (1957) state that the brown shrimp is caught along the entire German North Sea coast. The fishing grounds are in the estuaries and in the region of the large and small creek systems of the Wadden Sea. They are limited, in the sea, by the 15 to 20 m line which runs along the coast of Schleswig-Holstein, in the Elbe/Weser estuary up to 20 to 25 n mi (46 km), off the coast and along the coast of East Friesland up to 10 to 15 nautical miles. During spring and late autumn the fishing is carried out more seaward than during the months July to October, when fishing is almost exclusively confined to areas close to the coast. There are good shrimp fishing grounds near the estuaries of the rivers Eider, Elbe, Weser and Ems. Hydrographically the entire fishing area is characterized by strong tidal currents of strength up to 3 m/sec, and by continuous discharge of fresh water into this area by the rivers mentioned. Because of the marked annual and seasonal fluctuations in the quantity of fresh water discharges, the salinity on the fishing grounds is subject to great fluctuations.

Mistakidis (1960) stated that in England the three main centres of the shrimp fishery are the Wash, the Thames estuary, and the Lancashire coast. Landings of pink and brown shrimps in these areas amount approximately to 80 percent of the total landings.

Kurc, Faure and Laurent (1965b) stated that along the French coast there are areas in the Atlantic as well as on the Channel, which are rich in sand shrimps, especially those close to the estuaries of the rivers Gironde, Loire, and in the Bight of the Seine (Fig. 18). In each of these areas about one third of the total annual production (which is between 1,400 and 1,800 t) is produced. There is also a small shrimp fishery along the coast of Vendée, in the Bight of Mont Saint Michel and on the east coast of Contentin.

Differential abundance associated with hydrographical features

See section 4.11

Changes in ranges during development of the fishery

When only push nets, baskets and stow nets were used, the fishery was fairly close to the shore. When trawling was introduced, the range depended on the action radius of the boat. Sailing boats operated along the coast, while powered boats could fish further out to sea.

5.23 Depth ranges

Bathymetric contour

The fishery along the German coast is limited by the 15 to 20 m depth line (Meyer-Waarden and Tiews, 1957).

Variations of density with depth

During spring and late autumn the density of shrimp stocks is greater in the deeper areas than in the shallow. The contrary is the case during the months of July to October (Tiews, 1953a, 1953b).

5.24 Conditions of the grounds

The fishing grounds have sandy or muddy bottoms with usually rich food supply.

5.3 Fishing seasons

5.31 General pattern of seasons(s)

The main fishing season extends from spring to late autumn depending on the migration of Crangon in the fishing grounds (see section 3.51).

In the Netherlands there is a regular winter fishery. In the other countries the shrimp fishing boats are too small to permit a winter fishery. In Germany a winter fishery is of no interest to the fishermen, since prices are fixed upon agreement between the fishermen and the industry for the whole year, and so the lower winter catches do not yield a profit.

For small fishing boats bad weather prevailing during winter would greatly hamper fishing operation. Another factor hampering the conduct of a successful winter fishery in the German waters is that heavy winter storms usually destroy the markings of the numerous creeks making navigation extremely difficult (Meyer-Waarden and Tiews, 1963b).

5.32 Dates of beginning, peak and end of season(s)

Approximate dates in various fishing areas

The German shrimp fishery usually starts at the end of March or the beginning of April when water temperatures are generally above 5°C, and terminates at the end of November. Maximum catches of small sized shrimps are obtained during July to October, when 70 to 80 percent of the annual catches are taken. The catches of large sized shrimps, i.e. those for human consumption, are much more balanced with peaks in April to May and in October (Fig. 19) (Meyer-Waarden and Tiews, 1957, 1965a). Also the Belgian shrimp fishery lasts from March to November (Gilis, 1952).

The Dutch fishery for large sized shrimps operates through the year.

In 1963 and 1965 maximum production was recorded during September to October (Boddeke, 1966b).

5.33 Variation in date or duration of season

Severe and prolonged winters retard the beginning of the fishery, just as early winters cause its earlier termination. In warm years German fishermen may extend the fishing season until Christmas.

Fig. 18 German (Meyer-Waarden and Tiews, 1965a) and French shrimp fishing areas (Kurc, Faure and Laurent, 1965b)

Fig. 19 Seasonal distribution of German shrimp landings 1954–1960 (Meyer-Waarden and Tiews, 1965a).

During the years 1930 to 1939 the peak of the fishing season was usually in August. Since 1949, quite likely due to climatological changes and consequent cooler August temperatures, the peak has shifted to September/October (Tiews, 1954b).

5.4 Fishing operations and results

5.41 Effort and intensity

Type of unit of effort

Since most of the fishing trips in the German shrimp fishery do not exceed 16 h, one fishing trip can be considered a unit of effort. Since 1958 nearly all shrimp cutters fish with two nets, while before 1930 they fished with one net only. Two-net fishing was introduced on the coast of Niedersachsen during the years 1930 to 1939, and on the coast of Schleswig-Holstein from 1948 to 1958.

Tiews (1954b) designated catch per unit effort for the fishing fleet of Büsum, as the catch per net per 10 h trip taking into consideration the seasonal variations in fishing time.

The fishing trips of the large Dutch shrimp fishing vessels last five days. The catch per trip of these boats cannot, therefore, be compared with that of the smaller boats which go fishing, as the German boats do, from early morning until the afternoon (Boddeke, 1962a, 1962b). Gilis (1960) expressed the catch per unit of effort of the Belgian fleet, as the catch per 100 h fishing, multiplied by the hp of the engine.

Landings per unit of fishing effort

Tiews (1954b) has given the average landings of small and edible shrimps per trip for the period 1930 to 1952 for the shrimp fishing vessels stationed in Büsum.

Bartling (1964, 1965) found that a fishing boat of 14 to 16 m length fished nearly twice as many shrimps as one of 10 to 12 m length.

The fluctuations in landings per unit of fishing effort of the Belgian shrimp fishery for the period 1935 to 1959 are given by Gilis (1960) (Table XIII).

Catches per unit of fishing effort

In the Thames estuary the catch per hour is usually 32 to 68 kg, the quantity depending on the fishing ground and on the season of the year. Catches of 225 to 270 kg are not unusual. However, there are also records of only 9 or 13 kg of shrimps caught in two hours trawling (Mistakidis, 1960).

French shrimp catches during winter generally do not exceed 3 kg of edible shrimps per h. During June to July the catches per h are between 2 and 15 kg while in December they are often below 1 kg (Kurc, Faure and Laurent, 1965b).

Fishing effort per unit area

No information.

Total fishing intensity

The German shrimp fishery carried out 51,715 fishing trips (of less than one day each) in 1964. Of these, 30,58Y were on the coast of Niedersachsen. This showed a decline in fishing effort as compared to the period 1958–63, when on an average 32,958 fishing trips were made. The changes in fishing effort on the German coast during 1954 to 1964 have been traced by Tiews (1965).

The number of Belgian shrimp fishing boats has declined steadily since before the second World war. In 1936 it was 285 and in 1959 only 149. However, the size of angine has increased from 33.2 hp during the years 1935 to 1939, to 62.7 hp during 1956 to 1959 (Table XIII) (Gilis, 1960).

The sizes of the Dutch shrimp fishing fleet in the years 1951, 1954, 1957, 1960 and 1961 are given by Boddeke (1962b).

Causes of variation in fishing effort and intensity

The German shrimp fishing fleet amounting to 690 fishing boats in 1937, decreased to 674 boats in 1955 (Meyer-Waarden and Tiews, 1957). In 1964 only 489 boats were operating as a result of a special scheme sponsored by the government under which certain fees were paid to the fishermen upon retirement on condition that their old boats were destroyed for thinning out the fleet in order to make it more profitable (Tiews, 1965).

5.42 Selectivity

The cod end, as well as the anterior parts of the net contribute to selective fishing (Bohl, 1963a, 1963b).

The absolute catches of edible shrimps are largest when mesh sizes of 11 to 12 mm (from knot to knot) in the cod end are used. Smaller mesh sizes yield smaller catches of edible shrimps but considerably larger catches of smaller shrimps (Gilis, 1952; Mistakidis, 1958; Bohl and Koura, 1962; Kurc, Faure and Laurent, 1965b). The relation between the 50 percent retention length and the value of catch sizes times selection factor is given by Bohl and Koura (1962) (Fig. 20).

TABLE XIII

Fishing effort and shrimp landings in Belgium from 1935 to 1959 (Gilis, 1960)

According to Bohl (1963a, 1963b), since the anterior parts of the net have selective properties, the following mesh sizes obtain the best catches of edible shrimps:

TABLE XIV

Mesh sizes

The change in mesh sizes is claimed to yield the following advantages:

1. A larger quantity of edible shrimps is caught for no extra expenditure or work.

2. Because of the large mesh size the quantity of small shrimps caught is reduced and better and larger catches of large-sized edible shrimps are obtained.

3. The larger mesh of the cod end (10 to 11 mm) allows an immense number of juvenile shrimps to escape, thus helping in the protection of shrimp stocks.

In the German shrimp fishery the mesh sizes of the cod ends have been increased since 1962 because of the difficulty in marketing small sized shrimps consequent to the abolition of the law that guaranteed the selling of small sized shrimps (Meyer-Waarden and Tiews, 1957).

5.43 Catches

Total annual yields

The Yearbook of Fishery Statistics published by FAO gives the total annual yields in various countries (FAO, 1965) (Table XV).

Total annual yields from different fishing grounds

Mistakidis (1960) reported that the landings of pink and common shrimps in England and Wales during the past 48 years showed fluctuations between 890 t and 3,700 t. Certain distinct falls in landings may have been due to the reduced effort during the war years and immediately after, and to the severe winters of 1928 to 1929, 1939 to 1940, and 1946 to 1947. Even if these exceptionally poor years are not taken into consideration, on the whole, landings during the past 25 years were smaller than for the period 1910 to 1930. Whether reductions in landings was the result of a decline in the stock, or of reduced fishing effort, it is difficult to determine as there are no available data with regard to the number of boats and men engaged in the shrimp fishery.

Meyer-Waarden and Tiews (1965a) have described the development of the German shrimp fishery during 1928 to 1960 and furnished the yearly landing figures (Table XVI). The yields showed considerable fluctuations during this period. The German shrimp landings by areas as given in Table XVII indicate however that the development was different from area to area. During the period 1949 to 1959 catches of edible shrimps increased in Oldenburg, Ostfriesland and Schleswig-Holstein, and decreased in the Elbe/Weser area. During the same period catches of small industrial shrimps decreased in Oldenburg and Elbe/Weser, but showed an increase in Ostfriesland and in Schleswig-Holstein.

Catch statistics of the Belgian shrimp fishery have been collected since 1935. During the years 1935 to 1939 the annual catches fluctuated between 2,671 and 4,059 t and amounted, on an average, to 3,181 t. From 1946 to 1950 the catches varied between 1,289 and 2,034 t and were on an average 1,664 t. During 1951 to 1953 the annual average catch amounted to 2,051 t and decreased during the period 1956 to 1959 to 1,509 t (Table XIII) (Gilis, 1960). In Belgium there is no fishery for small shrimps for industrial use, as is also the case in France (Personal communications).

The Dutch landings of edible and small shrimps for 1951 to 1961 are given by Boddeke (1962a, 1962b, 1966).

Maximum equilibrium yield

No information.

Fig. 20 Relation between the 50% retention length and the value of catch size times selection factor (Bohl and Koura, 1962).

TABLE XV

Landings (in t) of common shrimp by countries according to Yearbook of Fishery Statistics

¹ The landings given for Algeria are considered doubtful by the author
² Figures include also landings of pink shrimp (Pandalus montagui)
³ FAO estimate

TABLE XVI

German common shrimp landings in tons

TABLE XVII

German mean landings on common edible shrimps (a) and small shrimps (b) by districts in tons

6 PROTECTION AND MANAGEMENT

6.1 Regulatory (legislative) measures

6.11 Limitation or reduction of total catch

Limitation on the efficiency of fishing units

There are no limitations at all in the Belgian shrimp fishery. The Dutch “Produktschap voor Vis en Visprodukten” has prescribed that fishing boats landing shrimps are not allowed to have a dragging power above 2,000 kg.

In England the different Fisheries Districts have exercised various legislative restrictions on the sizes of fishing boats, length of beam of trawls and push nets, diameter of nets, duration of operation of trawls and obligatory release of undersized fish.

Limitation on the number of fishing units, fishermen

In Germany credit facilities for replacement of old shrimp fishing boats are given only on condition that the old boats are destroyed in order to limit the number of fishing boats. However, so far a number has not been fixed by the law.

Limitation on total catches (quota): daily, seasonal, annual

When catches are large the processing firms in Germany that have contracts with fishermen for supply of edible shrimps for processing fix a ceiling for the daily quota to be delivered. Such restrictions do not normally exist for small sized fodder shrimps.

According to the Fisheries Convention for the NE Atlantic (24 June 1959), the industrial by-catches of the shrimp fishery are not allowed to contain more than 10 percent of undersized protected fish. Meyer-Waarden and Tiews (1965a) have calculated that the industrial catches of the German shrimp fishery during the years 1954 to 1960 contained less than 10 percent of undersized protected fish.

6.12 Protection of portions of population

Closed areas such as spawning or nursery grounds

In France the shrimp fishery is prohibited in certain areas, mostly in bays, in order to prevent catches of undersized commercial fish.

Closed seasons

In England, a closed season for shrimps and prawns (December through April), is imposed in the Lancashire and Western Sea Fisheries District.

Limitations on size or efficiency of gear or craft

The State of Schleswig-Holstein in Germany has regulations prohibiting mesh sizes below 7 mm (from knot to knot). There are no other governmental limitations in the German shrimp fishery, except some marketing ordinances (Meyer-Waarden and Tiews, 1957).

In France the minimum mesh size in the cod end of nets made of synthetic fibres has been fixed at 21 mm (stretched).

In the Netherlands coastal fishery the lower limit of mesh size of shrimp trawls is fixed at 17 mm.

In England, the Dee Fishery District, the Kent and Essex Sea Fisheries District, the Cumberland Sea Fisheries District, the South Wales Sea Fisheries District and the Lancashire and Western Sea Fisheries Joint Committee, all exercise limits on mesh size of shrimp and prawn nets. The last two agencies also impose obligatory release of undersized shrimps. The Cumberland Sea Fisheries District have restrictions on the size of fishing boats as well.

8 REFERENCES

Balss, H., 1931 Uber die Chemorezeption bei Garnelen. Biol.Zbl., 33(8):508–11

Barber, S.B., 1961 Chemoreception and thermoreception. In The physiology of crustacea, edited by T.H. Waterman, New York Academic Press, vol.2:109–31

Bartling, G., 1964a Betriebswirtschaftliche Mitteilungen, 2. Bericht 1962. Betriebsaufwand und -ertrag in der “gemischten” Krabbenfischerei. Fischerblatt, 12(3):53–60

Bartling, G., 1964b Betriebswirtschaftliche Mitteilungen. 1. Bericht 1962. Betriebsaufwand und -ertrag in der “reinen” Krabbenfischerei. Fischerblatt, 12(2):29–35

Bartling, G., 1965 Betriebswirtschaftliche Mitteilungen, 1. Bericht 1963. Der Betriebserfolg in der “reinen” Krabbenfischerei. Fischerblatt, 13(2):25–31

Becker, E., 1941 Die Pigmente der Ommin- und Ommatingruppe, eine neue Klasse von Naturfarbstoffen. Naturwissenschaften, 29:237

Belloc, G., 1938 Die Fischerei auf Krebstiere. Hanb.Seefisch.Nordeurop., 7(1):83–7

Boddeke, R., 1961 ICES, C.M. Shellfish Committee, (50):1–2

Boddeke, R., 1962a Methods to improve the yield of the Dutch shrimp fisheries. ICES, C.M. Special Meeting on Crustacea, (33):1–5

Boddeke, R., 1962b Resultaten van drie jaar garnalenonderzoek. Visserijinieuws, 15(5):66–70

Boddeke, R., 1965a Een beter garnalennet. Visserijinieuws, 18(1):2–8

Boddeke, R., 1965b Een beter garnalennet. Visserijinieuws, 18(7):213–5

Boddeke, R., 1966a Is it possible to forecast the landings of brown shrimp? ICES, C.M., Shellfish Committee, M:7

Boddeke, R., 1966b, Sexual cycle and growth of brown shrimp (Crangon crangon). ICES, C.M., Shellfish Committee, M:6

Bohl, H., 1963a Further investigations on the selectivity of beam trawls in the German shrimp fishery. ICES, C.M., Shellfish Committee, (55):1–5

Bohl, H., 1963b Weitere Untersuchunger über die Selektivität der Garnelenkurren vor der nordfriesischen Küste. Protok.FischTech., 8(38):231–51

Bohl, H. and R. Koura, 1962 Selektionsversuche mit Garnelenkurren vor der nordfriesischen Küste. Protok.FischTech., 8(35):1–33

Broekema, M.M.M., 1942 Seasonal movements and the osmotic behaviour of the shrimp Crangon crangon L. Archs néerl.Zool., 6:1–100

Caudri, L.W.D., 1937 Einfluss der Temperatur und des Salzgehaltes auf die Sterblichkeit von Garnelen (Crangon crangon L.). Archs néerl.Zool., 3:179–96

Davis, F.M., 1927 An account of the fishing gear of England and Wales. Fishery Invest., Lond. (2), 9(6):122 p.

Ehrenbaum, E., 1890 Zur Naturgeschichte von Crangon vulgaris Fabr. Berlin, Dtsch.Seefisch.- Verein, Mittl.Sekt.Küsten- u.Hochseefisch., Sonderbeilage: 9–124

FAO 1965 Yb.Fish.Statist. (18)

Florey, E., 1952 Untersuchungen über die Natur der Farbwechsel-hormone der Crustaceen. Biol.Zbl., 71:499–511

Florkin, M., 1960 Ecology and metabolism. In The physiology of crustacea, edited by T.H. Waterman, New York, Academic Press, vol.1:395–406

Flügel, H., 1960 Über den Einfluss der Temperatur auf die osmotische Resistenz und die Osmo-regulation der decapoden Garnele Crangon crangon L. Kieler Meeresforsch., 16(2):186–200

Flügel, H., 1963 Elektrolytregulation und Temperatur bei Crangon crangon L. und Carcinus maenas L. Kieler Meeresforsch., 19(2):189–95

Gilis, C., 1952 La pêche crevettière sur la côte belge: son évolution au cours des années 1935–1951 et son influence sur le stock de la crevette. Mém.Inst.Etud marit.Belg., (8):1–55

Gilis, C., 1960 Grise Crevettière sur la côte belge. ICES, C.M., Comité des Mollusques et Crustacés, 18

Goodwin, T.W., 1960 Biochemistry of pigments. In The physiology of crustacea, edited by T.H. Waterman, New York, Academic Press, vol. 1:101–35

Havinga, B., 1929 Krebse und Weichtiere. Hanb.Seefisch.Nordeurop., 3(2):1–142

Havinga, B., 1930 Der Granat (Crangon vulgaris Fabr.) in den holländischen Gewässern., J.Cons.perm. int.Explor.Mer, 5:57–87

Heidrich, H., 1930 Untersuchungen über die sogenannte Gammelfischerei an der preussischen Nordseeküste. Z.Fisch., 28:13–82

Henking, H., 1927 Der Fang der Nordsee-Garnelen (Crangon vulgaris L.) in der Ostsee. Midd.dt.Seefish Ver., 43(1):1–14

Herdman, W.A. 1892 Report on the investigations carried on in 1892 in connection with the Lancashire sea-fisheries laboratory at University College, Liverpool. Rep.Lanc.Sea-fish.Lab., pp 1–48

Jensen, J.P., 1958 The relation between body size and the number of eggs in marine Malacostrakes. Medd.Danm.Fish.-og-Havunders., 2(19):1–25

Jorgensen, O.M., 1923 Crustacea. In Marine plankton, plankton investigations. Rep.Dove Mar.Lab., N.S., 12:112–33

Kingsley, J.S., 1886 The development of Crangon vulgaris. Bull.Essex Inst., 18(7–9):99–151

Kingsley, J.S., 1889 The development of Crangon vulgaris. Bull.Essex.Inst., 21(1–3):1–34

Kleinholz, L.H., 1961 Pigmentary effectors. In The physiology of crustacea, edited by T.H. Waterman, New York, Academic Press, vol.2:133–63

Koller, G., 1925 Über den Farbwechsel bei Crangon vulgaris. Verh.dt.zool.Ges., 30:128–32

Koller, G., 1927 Über Chromatophorensystem, Farbensinn und Farbwechsel bei Crangon vulgaris. Z.vergl.Physiol., 5:191–246

Koller, G., 1928 Versuche über die inkretorischen Vorgänge beim Garnelenfarbwechsel. Z.vergl. Physiol., 8:601–12

Kourist, W., E. Mauch und K. Tiews, 1964 Ergebnisse von im Jahre 1962 durchgeführten Garnelen-markierungsexperimenten. Arch.FischWiss., 15(1):16–22

Kühl, H., 1949 Muscheln und Garnelen. Fischereiwelt, 1(1)

Kühl, H., 1956 Untersuchung der Nahrung von jungen Seehasen (Cyclopterus lumpus L.) im Mündungsgebiet der Elbe. Arch.FischWiss., 7(1):40–7

Kühl, H., 1961 Nahrungsuntersuchungen an einigen Fischen im Elbe-Mündungsgebiet. Ber.dt.wiss., Kommn.Meeresforsch., 16(2):90–104

Kühl, H., 1963 Über die Nahrung der Scharbe (Limanda limanda L.). Arch.FischWiss., 14(½):8–17

Kühl, H., 1964a Protokolle zu den Nahrungsuntersuchungen an einigen Fischen der Elbmündung. Veröff.Inst.Küst.-u.Binnenfisch., (32):1–30

Kühl, H., 1964b Protokolle zu den Nahrungsuntersuchungen an Scharben (Limanda limanda L). Veröff. Inst.Küst.-u.Binnenfisch., (33):1–27

Kühl, H. und H. Mann, 1963a On the distribution of shrimp larvae (Crangon crangon L) in the estuary of the Elbe. Veröff.Inst.Küst.-u.Binnenfisch., (27):50–2

Kühl, H., 1963b Das Vorkommen von Garnelenlarven (Crangon crangon L.) in der Elbemündung. Arch. FischWiss., 14(½):1–7

Kurc, G., 1964 Première série d'expériences sur la sélectivité du chalut à poissons. Sci.Pêche (123):1–6

Kurc, G., L. Faure et T. Laurent, 1965a La pêche des crevettes au chalut et les problèmes de sélectivité. Rev.Trav.Inst.(scient.tech.) Pêches marit., 29(2):137–61

Kurc, G., 1965b Essais d'un nouveau type de chalut équipé d'un dispositif de sélectivité pour la pêche des crevettes. Sci.Pêche, 136:1–7

Lloyd, A.J. and C.M. Yonge, 1947 The biology of Crangon vulgaris L. in the Bristol Channel and Severn estuary. J. mar.biol.Ass.U.K., 26:626–61

Luther, W. und H. Maier, 1963 Versuche über die Funktion der l. Antenne von dekapoden Kreasen als Strömungssinnesorgan. Helgoländer wiss.Meeresunters., 8(4):321–332

Lühmann, M., 1963 Bericht über die Struktur der Krabbenfischerei. (MS)

Mathias, P., 1938 Sur la résistance de Palaemon squilla L. et de Crangon vulgaris F. à la diminution de salure de l'eau. Bull.Soc.zool.Fr., 63:337–43

Maucher, W.-D., 1961 Statistische Untersuchungen über Unterschiede in den Körperproportionen zwischen der Nord-und Ostseeform von Crangon crangon L., Kieler Meeresforsch., 17(2):219–27

Meixner, R., 1966a The effects of food supply on moulting, growth and spawning of the shrimp Crangon crangon (L.). ICES, C.M., Shellfish Committee, M:5:1–7

Meixner, R., 1966b Eine Methode zur Aufzucht von Crangon crangon (L.). (Crust. Decap. Natantia). Arch.FischWiss., 17(1):1–4

Meixner, R., 1967 Experimentelle Untersuchungen zur Biologie der Nordseegarnele. Dissertation, Univ. Hamburg.

Meyer-Waarden, P.F., 1931 Die im Jadebusen gebräuchlichen Granatfanggeräte und ihre Eignung für den Fang. Mitt.dt.Seafish Ver., 47:3–30

Meyer-Waarden, P.F., 1934 Ein Beitrag zur Eiablage der Nordseekrabbe (Granat) Crangon vulgaris Fabr. Zool.Anz., 106(7/8):146–56

Meyer-Waarden, P.F., 1935a Ein Beitrag zur Frage der Laichperiodizität bei der Nordseekrabbe (Granat) Crangon vulgaris Fabr. Zool.Anz., 109(frac12;):23–32

Meyer-Waarden, P.F., 1935b Wachstums- und Altersuntersuchungen an der Nordseekrabbe (Granat) Crangon vulgaris Fabr. Zool.Anz., 111(5/6):145–52

Meyer-Waarden, P.F., 1937 Ein Beitrag zur Frage der Brutbiologie der Ostseekrabbe Leander adspersus (Rathke) var. fabricii Rathke in der Wismarchen Bucht. Zool.Anz., 117(7/8):161–8

Meyer-Waarden, P.F. und K. Tiews, 1957 Krebs- und Muscheltiere. l. Teil. Krebstiere by K. Tiews. Arb.dt.FischVerb., (8):1–56

Meyer-Waarden, P.F., 1963a Further results of the German shrimp research. Veröff Inst.Küst. -u.Binnenfisch., 27:24–38, also issued as ICES, C.M. Special meeting on Crustacea 1962(35):1–13

Meyer-Waarden, P.F., 1963b Catch composition of the German shrimp fishery in 1962. Veröff.Inst.Küst.-u. Binnenfisch., 27:39–41

Meyer-Waarden, P.F., 1965a Der Beifang in den Fängen der deutschen Garnelenfischerei in den Jahren 1954–1960. Ber.dt.wiss.Komm.Meeresforsch., 18(1):13–78

Meyer-Waarden, P.F., 1965b Grundlagenmaterial zu "Die Zusammensetzung der Fänge der deutschen Garnelen-fishcerei in den Jahren 1954–1960. Ber.dt.wiss.Komm.Meeresforsch., 18(1), also issued as Veröff.Inst.Küst.-u.Binnenfisch., 35:1–29

Mistakidis, M.N., 1958 Comparative fishing trials with shrimp nets. Fishery Invest., Lond. (2), 22(1):1–21

Mistakidis, M.N., 1960 The shrimp industry in Essex. Essex Nat., 30(4):228–44

Münzing, J., 1960 Färbungsversuche an Nordseegarnelen zur Markierung. Infn Fischw.Auslds, 7(5/6):151–2

Münzing, J., 1962 Farbmarkierungen an Nordseegarnelen. Infn Fischw.Auslds, 9(½):20–1

Nouvel, L., 1939 Observation de l'accouplement chez une espèce de crevette Crangon crangon. C.r.he bd. Séanc.Acad.Sci., Paris, 209:639–41

Nouvel-Van Rysselberge, L., 1937 Contribution à l'étude de la mue, de la croissance et de la régénération chez les Crustacés Natantia. Rec.Inst.zool.Torley-Rousseau, 6:5–161

Plagmann, J., 1939 Ernährungsbiologie der Garnele (Crangon vulgaris Fabr.). Helgoländer wiss. Meeresunters., 2(1):113–62

Plankemann, H., 1935 Beiträge zur Physiologie der Garnelenhäutung. Schr.naturw.Ver.Schlesw.Holst., 21(21):195–216

Plett, A., 1965a Further results on the distribution of shrimp larvae (Crangon crangon L.) on the German coast during 1964. ICES, C.M., Shellfish Committee (25)

Plett, A., 1965b Über das Vorkommen von Garnelenlarven (Crangon crangon L.) vor der deutschen Küste in den Jahren 1963 und 1964. Arch.FischWiss., 16(1):54–67

Rees, C. B., 1952 Continuous plankton records: The decapod larvae in the North Sea, 1947–1949. Hull Bull.mar.Ecol., 3(22):157–84

Schnakenbeck, W., 1942 Schleppnetze. Handl.Seefisch.Nordeur., 4(1–2):1–42

Schöne, H., 1952 Zur Funktion der Dekapodenstatocyste. Verh.dt.zool.Gas., pp. 89–96

Schöne, H., 1954 Statozystenfunktion und statische Lageorientierung bei dekapoden Krebsen. Z.vergl. Physiol., 36:241–60

Schöne, H., 1957 Kurssteuerung mittels der Statocysten (Messungen an Krebsen). Z.vergl.Physiol., 39:235–40

Schöne, H., 1959 Die Lageorientierung mit Statolithenorganen und Augen. Ergebn.Biol., 21:161–209

Schöne, H., 1961 Complex behaviour. In The physiology of crustacea, edited by T.H. Waterman, New York, Academic Press, vol.2:465–515

Schwarz, A., 1932 Spülsaum aus Exuvien von Garnelen (Crangon). Senckenbergiana, 14:1–428

Spiegel, A., 1927a Über die Chemorezeption der sogenannten Riechgeissel bei Crangon vulgaris Fabr. Zool.Anz., 71:43–52

Spiegel, A., 1927b Über die Chemorezeption von Crangon vulgaris Fabr. Z.vergl.Physiol., 6(3/4):688–730

Tesch, J.J. und J. de Veen, 1938 Die niederländische Seefisherei. Handb.Seefisch.Nordeurop., 7(2):1–99

Tiews, K., 1952 Zur Rentabilitätsfrage der Krabbenfischerei. Fischereiwelt, 4(3)

Tiews, K., 1953a Zur Biologie der Nordseegarnele. In 20 Jahre DEUKO. Hamburg DEUKO-Gesellsch. Förd.Küst.Fisch.. pp.12–6

Tiews, K., 1953b Studien zu der Büsumer Garnelenfischerei, ihren biologischen Grundlagen und ihrer wirtschaftlichen Struktur. Disseration, University of Kiel, 141 p.

Tiews, K., 1954a Die biologischen Grundlagen der Büsmer Garnelenfischerei. Ber.dt.Komm.Meeresforsch., 13(3):235–69

Tiews, K., 1954b Einfluss der Gezeiten und der Wassertemperatur auf die Garnelenfischerei. Ber.dt. Komm.Meeresforsch., 13(3):270–82

Tiews, K., 1963 On the use of plastic tags for tagging brown shrimp (Crangon vulgaris Fabr.). ICES, C.M., Shellfish Committee, (7):1–4, also issued as Veröff.Inst.Küst.-u. Binnenfisch., (27):42–9

Tiews, K., 1964 Further results of the German shrimp tagging experiments (Crangon vulgaris Fabr.). ICES, C.M., Shellfish Committee (11):1–2

Tiews, K., 1965 Lichtung des Nordseegarnelenbestandes (Crangon crangon L.) durch Wegfrass. Arch. FischWiss., 16(2):169–81

Tiews, K., 1966 Erprobung einer neuartigen holländischen Garnelen-kurre. Fischerblatt. (2):1–3

Tiews, K., 1967 The use of plastic tags for tagging small shrimps (brown shrimps, Crangon vulgaris Fabricius) and on the problems of tagging experiments of this species of shrimp. Symp.Ser.mar.biol.Ass.India, 2(4):1296–1300

Thorson, G., 1946 Reproduction and larval development of Danish marine bottom invertebrates, with special reference to the planktonic larvae in the Sound (Øresund). Medd.Danm.Fisk. Havundersøg, 4(1):1–523

Ubrig, H., 1952 Der Eifluss von Sauerstoff und Kohlenioxyd auf die taktischen Bewegungen einiger Wassertiere. Z.vergl.Physiol., 34:479–507

Verbrugghe, L., 1932 Die belgische Seefischerei. Handb.Seefisch.Nordeurop., 7(3):1–39

Verne, J., 1926 Les pigments dans l'organisme animal. Paris, Doin, 608 p.

Verwey, J., 1960 Über die Orientierung wandernder Meerestiere. Helgoländer wiss.Meeresunters., 7(2):51–8

von Brandt, A., 1959 Fanggeräte der Kutter- und Küstenfischerei. Schr-Reihe AID, (113):1–105

von Buddenbrock, W., 1952 Sinnesphysiologie. In Vergleichende Physiologie, Basel, Verl. Birkhäuser, vol.1:504

Watermann, T.H., 1961 Comparative physiology. In The physiology of crustacea. New York, Academic Press, vol.2:521–84

Williamson, H.C., 1901 On the larval stages of decapod Crustacea. The shrimp (Crangon vulgaris Fabr.). Rep.Fish.Bd Scot., 19(3):92–120

Williamson, H.C., 1915 Crustacea Decapoda. Larven. Nord.Plankt., 3(6):315–588

Wollebaek, A., 1908 Remarks on decapod crustaceans of the North Atlantic on the Norwegian fjords I and II. Bergens Mus.Årb., 12:1–74

Wulf, A. and A. Bückmann, 1932 Der “Gammelfang” der Garnelenfischer und die Bedeutung des Fortfanges junger Plattfische für den marktfähigen Plattfisch-Bestand in der Deutschen Bucht. Helgoländer wiss.Meersunters, 19(1):1–61

Yonge, C.M., 1937 The nature and significance of the membranes surrounding the developing eggs of Homarus vulgaris and other Decapoda. Proc.zool.Soc.Lond., 107:449–517

Yonge, C.M., 1955 Egg attachment in Crangon vulgaris and other Caridea. Glasgow, University of Glasgow, Department of Zoology, pp. 369–98

Zarenkov, N.A., 1965 Revision of families Crangon and Sclerocrangon (Decapoda, Crustacea). Zool.Zh., 44(12):1761–74