BIOTIC Species Information for Nephrops norvegicus
|Researched by||Lizzie Tyler||Data supplied by||University of Sheffield|
|Refereed by||This information is not refereed.|
|Scientific name||Nephrops norvegicus||Common name||Norway lobster|
|MCS Code||S1402||Recent Synonyms||None|
|Additional Information||Also known as the Dublin Bay prawn, scampi and langoustine.|
|Taxonomy References||Howson & Picton, 1997, Fish & Fish, 1996, Ingle, 1997, Sardà, 1995, Connor et al., 1997(a),|
|Typical food types||Nephrops is an opportunistic predator feeding on crustaceans, molluscs and to a lesser extent polychaetes and echinoderms.||Habit||Free living|
|Bioturbator||Flexibility||Low (10-45 degrees)|
|Height||Insufficient information||Growth Rate||See additional information|
|Adult dispersal potential||10-100m||Dependency||Independent|
|General Biology Additional Information||Typical abundance
Early fisheries investigations revealed marked geographical variability in the abundance and size of individual Nephrops in trawls (Cole, 1965; Thomas, 1965a). In Loch Torridon, Chapman & Rice (1971) reported densities of Nephrops of 1 ind. /7.8 m² in 1968, whereas in 1969 it was 1 ind. /5.5 m². The density of two populations of Nephrops norvegicus was reported for two sites on the west coast of Scotland in the Clyde and the Sound of Jura (Thomas, 1965a). In the Sound of Jura the population of Nephrops norvegicus consisted mainly of small Nephrops below 30 mm carapace length (CL) at an estimated density of approximately 1 ind. /m². The density of Nephrops in the Clyde was much lower (approximately 1 ind. /4m²). Reasons for such variability in density, size and growth rates, are listed below.
Although Nephrops norvegicus is capable of swimming, it is a crawler more than it is a swimmer.
Growth (and fecundity) in Nephrops norvegicus are known to vary geographically and have been shown to be negatively correlated with burrow density (Tuck et al., 1997). Thus, growth rate appears to be density-dependent, and is also thought to be related to food availability. For example, Tuck et al. (1997) found growth was correlated with infaunal biomass. This suggests that nutritional stress occurs in populations with slower growing individuals. Growth of Nephrops may also be influenced at high densities through social behaviour changes (Cobb et al., 1982). Parslow-Williams et al. (2001) found evidence that nutritional limitation was occurring in Nephrops norvegicus from a site in the Clyde Sea with a high population density, compared to another site with a low density of individuals.
Information on the growth rate of lobsters is very limited (Thomas,1965c). Despite being one of the most studied decapods, the area of age and growth estimation is still one for which there is no standard methodology (Castro, 1995). A number of studies have estimated the growth rate of Nephrops norvegicus:
Loo et al. (1993) suggested that Nephrops could filter feed, allowing Nephrops to extend the size range of its food items. Farmer (1974d) reported that the expodites of the various mouth parts of Nephrops in most cases bore plumose setae, which when waved continuously produced water currents. Farmer (1974d) suggested that this behaviour was for cleaning suspended food particles away from the mouth. During another study Nephrops norvegicus were kept in small tanks containing fluorescently-marked food particles comprised of the brine shrimp Artemia salina. These food particles were found in the gills, stomach and intestine of Nephrops. Loo et al. (1993) suggested that this provided effective evidence of filter-feeding. However, this feeding may be more 'micro-raptorial' rather than strictly filter-feeding (Parslow-Williams et al., 2002). During periods of food scarcity, females spend a prolonged period in their burrows and suspension feeding is thought to occur (Loo et al., 1993).
Diel variation in feeding rates have been observed indirectly in Nephrops norvegicus. Catch rates of lobsters has always varied depending on the time of day with peak catches at dawn and dusk. Only those lobsters that have emerged from their burrows are caught in the trawls and, since it is assumed that they emerge mostly to forage (Chapman, 1980), catch patterns indicate diel patterns of feeding behaviour. The stomach contents of animals sampled by Parslow-Williams et al., (2002) indicated a feeding peak around dawn but not around dusk, although animals were out of their burrows. Sampling is complicated by the fact that satiated animals will return to their burrows and be unavailable for capture.
Supports which species
Barnes & Bagenal (1951) recorded large numbers of Balanus crenatus living on Nephrops norvegicus in the Clyde area. The following species have been observed on specimens of Nephrops norvegicus from the Irish Sea: Triticella koreni, Balanus crenatus, Electra pilosa, Eudendrium capillare, Sabella pavonina, Serpula vermicularis and a forminiferan probably Cyclogyra sp. (Farmer, 1972; cited in Farmer, 1975). The polychaete Histriobdella homari has been observed on the pleopods of two Nephrops norvegicus from the Irish Sea and Clyde Sea (Briggs et al., 1997).
|Biology References||Loo et al., 1993, Tuck et al., 1997, Parslow-Williams et al., 2002, Thomas & Davidson, 1962, Ennis, 1973, Chapman, 1980, Aréchiga et al., 1980, Simpson, 1965, Thomas, 1965a, Bailey & Chapman, 1983, Tully & Hillis, 1995, Cobb et al., 1982, Farmer, 1974b, Aréchiga & Atkinson, 1975, Anderson, 1962, Atkinson, 1989, Marine Institute, 2001, Thomas, 1965b, Cole, 1965, Conway Morris, 1995, Barnes & Bagenal, 1951, Farmer, 1975, Chapman & Rice, 1971, Farmer, 1974d, Castro, 1995, Marine Institute, 2003, Thomas, 1965c, Parslow-Williams et al., 2001, Briggs et al., 1997, Rice & Chapman, 1981, Hayward & Ryland, 1990, Julie Bremner, unpub data,|
|Distribution and Habitat|
|Distribution in Britain & Ireland||Common around most British coasts but not apparently recorded for the English Channel, the Bristol Channel or the Western Approaches. Populations also exist to the north east of Scotland on the Fladen Ground.|
|Global distribution||Nephrops norvegicus is widely distributed on muddy substrata throughout the north-east Atlantic from Iceland in the north to Morocco in the south. The species is found in the Mediterranean and is abundant in the Adriatic.|
|Biogeographic range||Not researched||Depth range||200 - 800 m|
|Migratory||Non-migratory / Resident|
|Distribution Additional Information||Migration
Tagging experiments have shown that Nephrops norvegicus do not migrate large distances (Marine Institute, 2001). In laboratory mesocosms individuals displayed very territorial behaviour, aggressively defending their burrows (Marine Institute, 2001).
|Physiographic preferences||Offshore seabed
|Biological zone||Lower Infralittoral
|Tidal stream strength/Water flow||Weak (<1 kn)
Very Weak (negligible)
|Salinity||Full (30-40 psu)
|Habitat Preferences Additional Information|
|Distribution References||Fish & Fish, 1996, Ingle, 1997, Sardà, 1995, Foster-Smith, 2000, Bruce et al., 1963, Connor et al., 1997(a), BODC, 1998, CEFAS, 2001, JNCC, 1999, Picton & Costello, 1998, Marine Institute, 2001, NBN, 2002, Hayward & Ryland, 1990, Julie Bremner, unpub data,|
|Reproductive Season||Summer to Autumn||Reproductive Location||As adult|
|Reproductive frequency||Annual episodic||Regeneration potential||No|
|Life span||6-10 years||Age at reproductive maturity|
|Generation time||See additional information||Fecundity|
|Egg/propagule size||Fertilization type||Internal|
|Reproduction Preferences Additional Information||Longevity
In the Irish Sea, Nephrops norvegicus individuals are not thought to live more than 8 or 9 years. In other areas, such as the Porcupine Bank, they may survive over 15 years (Marine Institute, 2001).
Age and size at sexual maturity
Tuck et al. (2000) found that, in the Firth of Clyde, age at the onset of sexual maturity was relatively constant between different study sites but varied between sexes. In general, the age at onset of maturity was 4 - 4.5 years in males and 3 - 3.5 years in females. The size (carapace length) at sexual maturity was found to be positively correlated to asymptotic length and negatively correlated to adult density and ranged from 21 - 34 mm in females and 29 - 46 mm in males (Tuck et al., 2000). The authors suggested that there may exist a minimum size threshold under which males may be too small to reproduce.
A full description of reproduction can be found in Jorgensen (1925). Most Nephrops stocks in British waters have an annual reproductive cycle (Marine Institute, 2003). Sexually mature Nephrops of both sexes moult towards the end of spring and into the summer. Mating takes place while the female is still 'soft' (Farmer, 1975) directly after the female has moulted and before the hardening of the new exoskeleton (Marrs, pers. comm.). Once fertilized the eggs are then carried on the females abdomen for 8-9 months, during which time the females tend to remain in their burrows.
Egg loss is common in crabs, lobsters, shrimps and prawns (Tuck et al., 2000). Reasons for egg loss include failure of the eggs to attach to the pleopods at oviposition, predation, and loss of eggs from the pleopods during the long developmental period (Kuris, 1991). In the Moray Firth a comparison between females with recently spawned eggs and females where the eggs were about to hatch suggested that 32 - 51 % of the eggs are lost during development and that this proportion is larger in smaller individuals (Chapman & Ballantyne, 1980).
Ovary resorption has been attributed to a number of factors in other decapods, including lack of fertilization, starvation, hormone deprivation and incorrect photoperiod (Aiken & Waddy, 1980; Sastry, 1983; Adiyodi & Subramoniam, 1983). The timing of ovary resorption after the spawning period, suggests that it occurs in females whose ovaries were not sufficiently developed to spawn at the suitable time. Whatever the cause, resorption is thought to be a mechanism for conserving or recycling nutrients.
The fecundity of Nephrops norvegicus is variable and different methods have been used to estimate Nephrops fecundity (Abelló & Sardá, 1982) for example:
In all investigations, the number of eggs was found to be directly proportional to the size of the female. Farmer (1974c) suggested that it was more accurate to estimate the fecundity from the eggs that are carried by the females because very often the oocytes are reabsorbed during the process of sexual maturation. However, it must also be noted that the number of eggs on the abdomen diminishes during incubation mainly due to predation (Morizur, 1979; cited in Abelló & Sardá, 1982).
During incubation it is generally thought that ovigerous females tend to remain within their burrows (Farmer, 1975). Females Nephrops come out of their burrows to allow their eggs to hatch and the larvae to escape from April -June (Farmer, 1974c).
Hillis (1968) reported that larvae of Nephrops norvegicus in the Irish Sea were dispersed by the local hydrographical conditions but they generally remain in the hatching areas of adults without being transported long distances. The main concentration of larvae in the Irish Sea were found in and near deep water. Hillis (1968) also suggested that there was a more easterly distribution of older larvae.
In the Irish Sea a gyre (circulating water mass) forms during the spring and summer, which coincides with the period when Nephrops larvae are present in the plankton. The gyre retained the larvae in the vicinity of the parent population, rather than being carried off by currents into areas of unsuitable substratum (Hill et al., 1996, 1997). This phenomenon has also been observed in the Adriatic and Clyde Sea (Marrs, pers. comm.). In addition to gyres, muddy sediments have also been associated with high densities of Nephrops norvegicus (Marrs, pers. comm.).
|Reproduction References||Tuck et al., 1997, Aiken & Waddy, 1980, Adiyodi & Subramoniam, 1983, Sastry, 1983, Farmer, 1974a, Dickey-Collas et al., 2000a, Thompson et al., 1986, Nichols, 1987, Chapman & Ballantyne, 1980, Eiriksson, 1970, Abelló & Sardá, 1982, Thorson, 1946, Hillis, 1968, Hill et al., 1996b, Hill et al., 1997, Marine Institute, 2001, Dickey-Collas et al., 2000b, Farmer, 1975, Tuck et al., 2000, Kuris, 1991, Julie Bremner, unpub data, Relini & Relini, 1989,|