Norway lobster is a medium to large sized crustacean decapod with well-calcified teguments, very pronounced rostrum, carapace and chelae, reduced pedunculated eyes and non-imbricated abdominal pleurae (Relini et al., 1999).

The body is long and more or less flat laterally. There are three to four bones on the dorsal side and one to two on the ventral side of cephalothorax. The abdomen is long and ends with a fan-shaped telson that enables the lobster to swim. However, when moving, Nephrops norvegicus walks more than it swims (Fisher et al., 1987; Relini et al., 1999).

The first pair of cephalic appendices has composite eyes, each with a mobile peduncule. The first pair of antennae is short and forked. Each of the second pair is long and simple. The telson is long, with two pronounced bones at its apex. The first pair of legs is well developed with strong chelae. The second and third are thinner and have chelae as well (Relini et al., 1999).

Norway lobster is orange coloured, with orange-red bands on chelae and on the anterior part of the cephalothorax.

World:
The species is distributed in the eastern Atlantic, from Morocco to Norway and Iceland, and in the Mediterranean (Fisher et al., 1987 and Relini et al., 1999).

Adriatic Sea:
The species was recorded at depths from about 30 meters in the northern Adriatic Sea to 400 meters in the southern part of the Sea (Karlovac, 1953; Froglia and Gramitto, 1988; Vrgoč, 1995; Marano et al., 1998a). In the northern part of the open Adriatic it can be found off Ancona. The most dense population is in the Pomo/Jabuka Pit region. There are rich fishing grounds in the Velebit Channel, Kvarner and Kvarnerić region along the Croatian coast (Karlovac, 1953; Crnković, 1964, Crnković, 1965). In the southern Adriatic, along the western (Italian) and eastern (Albanian) coasts, the settlements are not so dense (Karlovac, 1953; Marano et al., 1998a).

Because the range of this species in the Adriatic is a continuous one, particular Norway lobster settlements cannot be regarded as isolated (Karlovac, 1953). Nevertheless, some differences do exist, primarily in length frequencies among the settlements around Ancona and the Pomo/Jabuka Pit (Froglia and Gramitto, 1981, Froglia and Gramitto, 1988, IMBC et al., 1994), as well as among the settlements in the northern Adriatic channels and the Pomo/Jabuka Pit (Karlovac, 1953; Crnković, 1964, Crnković, 1965, Crnković, 1970; Jukić, 1974; Županović and Jardas, 1989). Froglia and Gramitto (1981) discussed these differences as the consequence of the difference in ecological factors that dramatically depress growth of N. norvegicus and other benthic decapods in the Pomo/Jabuka Pit. Similarly, Mantovani and Scali (1992), using genetic analysis, found that differences between Norway lobster off Ancona and the Pomo/Jabuka Pit did not surpass those at the population level. The differences were only a consequence of different environments.

Habitat:
N. norvegicus can be considered a “mud-loving” species, not restricted to a particular biocenosis or to a biocenotical zone (Froglia and Gramitto, 1981). This is certainly related to its habit of digging burrows for shelter (Crnković, 1965; Froglia 1972; IMBC et al., 1994).

Size:
Nephrops norvegicus is a species with separate sexes. Males are, on an average, larger than females. Although Fisher et al. (1987) stated that its maximal total length is 24 cm, larger specimens have been caught, primarily in the northern Adriatic. Crnković (1965), for example, found specimens up to 26,5 cm TL in northern Adriatic channels.

Length-weight relationship:
Because two different measures are used in fishery and biological research, total body length (TL) and carapace length (CL), the relationship between them is presented in the table, and the carapace length-weight relationship is given in the table.

Total Length (TL, mm)-Carapace Length (CL, mm) relationship.

Total Length (TL, mm)-Carapace Length (CL, mm) relationship.

The growth of Norway lobster, as in other crustaceans, is a discontinuous process with a succession of molts separated by the intermolt periods. During each molt, the old exoskeleton is shed and the animal grows very quickly before the new exoskeleton hardens. A well-defined molting periodicity was not found among juveniles, they seem to molt all year round. There is a molt synchronism in the adult population, it could be generally said that, in the Mediterranean, the females have one molting period a year (December-March), right after hatching the eggs (Gramitto, 1998).

The molting period of grown males is in late summer and autumn (August-October) (Gramitto, 1998). In the Adriatic, adult males have a molt peak between June and September. The frequency of gastroliths is always very low in adult females, little is known about their molt cycle, except that adult females do not molt between August and January, when they carry eggs externally (Gramitto, 1998).

Reproduction:
In the Adriatic, N. norvegicus spawns once a year (Froglia and Gramitto, 1981). The proportion of females with mature ovaries peaks in spring or at the beginning of summer (Froglia and Gramitto, 1981; Orsi Relini et al., 1998). Berried females were found in October and November (Orsi Relini et al., 1998), but some specimens can be present up to late spring (Froglia and Gramitto, 1981). According to Karlovac (1953), Norway lobster larvae are present in the Adriatic plankton in late winter, from January to April (Relini et al., 1999).

The sex ratio changes through the year. The proportion of females in the catch is lower when they carry external eggs because they are less active and more often hide in burrows. On the other hand, this proportion increases and is higher in the mating period (Crnković, 1965, Jukić, 1971; Froglia and Gramitto, 1981; Ungaro et al., 1999).

Data about the length at first sexual maturity at different localities are shown in the table. At the first maturity, the individuals are two (Froglia and Gramitto, 1981) or three years old (Orsi Relini et al., 1998).

Length at the first sexual maturity:

Carapage Length (CL, mm) at the first sexual maturity:

The relation between length of carapace and number of eggs in females in the Adriatic Sea, as found by different authors, is presented in the table. It can be seen that the number of eggs is correlated with the length (CL): i.e. bigger animals lay proportionally more eggs (Froglia and Gramitto, 1979). The relationship between the length of carapace and number of eggs is almost the same in different parts of the Adriatic (Pomo/Jabuka Pit and off Ancona), even though the size of mature females is quite different (Froglia and Gramitto, 1979). Ungaro et al. (1999) found smaller values in the southern Adriatic.

The number of eggs hatched is about one third of the numbers of oocytes (Froglia and Gramitto, 1981). Orsi Relini et al. (1998) found that, in the Adriatic, fecundity was about double that for embryos close to hatching, therefore meaning that the loss of embryos is about 50%.

Ratio between Carapace Length (CL, mm) and number of eggs.

Von Bertalanffy Growth Function (VBGF).
There are some differences in growth parameters between males and females. Males grow larger than females. Differences in growth dynamics among settlements in different parts of the Adriatic can also be observed. They are the result of differences in ecological conditions. However, the methods used in calculating the parameters might influence on the growth parameter estimates.

Parameters of the Von Bertalanffy Growth Function (VBGF).

* L_∞ of total lenght
** K/month, t_o/month

Feeding behaviour:
Norway lobster feed mainly on other decapod crustaceans and, to a lesser extent, on different crustaceans (euphausids and peracarids) and fish. Parts of carapace, shells and gastropoda scales, vertebra and fish otoliths and similar fragments were found in N. norvegicus stomachs (Cristo and Cartes, 1998). These surveys confirmed that the dominant prey-species in the alimentation were those usually found in demersal communities where Norway lobster lives. It was also determined that stomach was least full in summer, that is, in the period when gonads grow most intensively and occupy a great volume of the body cavity (Cristo and Cartes, 1998).

In the Adriatic the catch of Norway lobster fluctuates significantly in different times of day and night (circadian fluctuation), and during the year (seasonal fluctuation) (Crnković, 1970; Jukić, 1971, Froglia 1972; Froglia and Gramitto, 1981; Marano et al., 1998a; Županović and Jardas, 1989; Relini et al., 1999). Generally, the catch is highest at sunrise and sunset. This most probably due to the behaviour of this species; it spends most of its life buried in burrows in the sea sediment and goes out only in search for food before dawn and at dusk (Froglia 1972; Froglia and Gramitto, 1981). This kind of behaviour is more obvious in younger specimens and ovigerous females. As a result, different parts of the population are accessible to fishing gear at different times of day. Seasonal fluctuations exist for the same reason; the catch is biggest in spring, when the sex ratio is in favour of females (Froglia 1972; IMBC et al., 1994), in winter the catch is at a minimum. (IMBC et al., 1994; Marrs et al., 2000.)

Biomass/Abundance Indexes:
Šarčević (1992) estimated the N. norvegicus standing stock size in the Pomo/Jabuka Pit at 11810 tonnes. He also calculated MSY in the fishing area of Blitvenica (the eastern part of the Jabuka Pit) to be 41 tonnes annually with f_opt = 800 fishing days

In researching the Norway lobster population density with underwater television (UWTV), IMBC et al. (1994) and Froglia et al. (1997) found that the burrow density in the Pomo/Jabuka Pit was 0,6566 - 0,7185 m^-2, and 0,1067 - 0,6255 m^-2 off Ancona. The frequency of occupancy of the burrow is not known, but it is considered to be high, because burrow openings collapse quickly if they are not continuously repaired.

The following biomass (tonnes) of N. norvegicus at various burrows occupancy levels were calculated:

Mortality:
The mortality rate estimates of the N. norvegicus population in the Adriatic are shown in the table. It can be seen that females are exposed to higher mortality than males. Froglia and Gramitto (1988) explained this with the fishing which is most intensive in late spring and summer, the mating period, when females are dominant in the population.

Although analyses of the stomach contents of demersal bony and cartiligineous fish did not reveal N. norvegicus preys in any significant quantity, it seems that fishing mortality is the main component of overall mortality after recruitment to the seabed when the species assumes benthic life (Froglia and Gramitto, 1988).

Mortality rate coefficients for Norway lobster in the Adriatic.

Gear:
In the Adriatic Sea, the N. norvegicus is caught primarily with two types of gear: the majority of the catch is by bottom trawl nets and the rest with traps (mainly in channel areas of the northern Adriatic).

Fisheries Statistics:
Adriatic Sea landing of Norway lobster increased from the 1980s until the first half of the 1990s when a marked negative trend was established (Mannini and Massa, 2000.

Norway lobster ranks first by value and second by weight among the crustacean resources exploited in the Adriatic Sea. For the Adriatic (Italy and Croatia), total landings are approximately 2000 tonnes per year (Marrs et al., 2000). Adriatic trawling grounds are considered to be fully exploited or even overexploited (Froglia and Gramitto, 1982; IMBC et al., 1994; Sardà, 1998a, Sardà, 1998b).

Nephrops norvegicus capture fishery production (Adriatic Sea*). Data: FAO-FISHSTAT (GFCM (Mediterranean and Black Sea) capture production 1970-2003 (Release date: May 2005) Regional dataset available at ftp://ftp.fao.org/fi/stat/windows/fishplus/gfcm.zip.

*According to GFCM definition of statistical sub-areas the Adriatic Sea falls within the area 2.1, thus including only the Northern and Central basins, while the Southern Adriatic basin and consequently the coast of South-eastern Italy and of Albania are included in the Ionian Sea (area 2.2). In order to have as comprehensive a picture as possible of all Adriatic Sea fishery production, Albanian data originally classified as from the Ionian Sea have been included in the Adriatic data set used. Unfortunately, this was not feasible for South-western Italy (Apulia Region).

Selectivity:
Data on bottom trawl selectivity for Norway lobster in the Adriatic are shown in the table.

 

Scientific name	Common name	Project framework	Sampling (Survey)	Development of genetic marker (type & number of markers)	Genetic structure (analysed samples, geographic areas)	Population units in the Adriatic shared stock	Reference associated
Nephrops norvegicus	Norway lobster	GenPopAdr, MiPAF	√ (MEDITS 2001)	√ (microsatellites, 5 optimised loci)	√ (4; NA,MA,SA)	√ Single panmictic unit	Final report of GenPopAdr project , MiPAF Guarniero, 2004.

Minimum size:

Species (local or common name)	Species (scientific name)	Minimum size in cm or minimum weight in kg
ALB: It is strictly prohibited to fish and sell any aquatic species less than the minimum regulatory size as set out in Article 48.1 of Fisheries Regulations No.1 of 1997.
Skampi	Nephrops norvegicus	30 cm
CRO: The Order of 1998 (145/98) and amended by the Order 101/02 on the Protection of Fish and Other Marine Organisms was adopted to determine the minimum sizes of certain species of fish.
Škamp	Nephrops norvegicus	7 cm
ITA: The self-executing rules of Reg. EC 1626/1994 establish the minimum size to protect juveniles
Scampo	Nephrops norvegicus	20 mm Carapage length 70 mm Total lenght
SCG: The minimum size is laid down as follows: 2. Decree on prohibition of capture and trade in fish juveniles, undersized fish and other marine organisms no. 10/2004.