BIOTIC Species Information for Nephrops norvegicus
|Researched by||Lizzie Tyler||Data supplied by||University of Sheffield|
|Refereed by||This information is not refereed.|
|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,|