Investigating the link between Nephrops norvegicus burrow density and sediment composition in Scottish waters

Abstract

Campbell, N., Allan, L., Weetman, A., and Dobby, H. 2009. Investigating the link between Nephrops norvegicus burrow density and sediment composition in Scottish waters. – ICES Journal of Marine Science, 66: 2052–2059. Nephrops norvegicus is a burrowing decapod, found in the North Atlantic and Mediterranean Sea at depths of 10–1200 m, and currently the most valuable species taken by the commercial fishing industry in Scotland. It constructs and inhabits extensive burrow complexes in suitable muddy sediments. Owing to its variable emergence patterns, catch rates from traditional trawl surveys are not considered a good indicator of population size. Nephrops populations around Scotland are assessed using an underwater television (UWTV) survey method. Sediment samples are collected at the end of each UWTV deployment. This study focuses on two areas off the coast of Scotland and investigates the accuracy of the sediment maps used for assessment purposes, and the relationship between Nephrops burrow density and sediment composition, over the period 2002–2007. Nephrops have a stock-specific relationship with the sediment they inhabit, which retains the same form through fluctuations in population size.

Spatiotemporal abundance pattern of deep-water rose shrimp, <em>Parapenaeus longirostris</em>, and Norway lobster, <em>Nephrops norvegicus</em>, in European Mediterranean waters

“…In the Mediterranean Sea, the highest densities are found between 200 and 500 m, although high catch rates are also reported between 500 and 800 m depth (Abelló et al 2002). In areas with a wide continental shelf, such as the Adriatic Sea or close to the Ebro Delta, the Norway lobster can be found in shallow waters (Abelló et al 2002, Morello et al 2009, as in the eastern Atlantic and the North Sea (Campbell et al 2009). The Norway lobster is a sedentary species inhabiting burrows built in muddy bottoms at the shelf break and on the upper slope of the northeastern Atlantic and Mediterranean (Aguzzi and Sardà 2008).…”

Seasonal nutritional status in Norway lobsters,Nephrops norvegicus(L.): are females nutritionally compromised over the winter?

“…In high density areas competition for food may limit scope for growth. Moreover, increased aggressive social behaviour in high density areas could drive up the metabolic rate and thus energy requirements (Tuck et al 1997b;Chapman & Bailey 1987;Parslow-Williams 1998;Tuck et al 1999;Bell et al 2006;Campbell et al 2009). …”

Habitat and Ecology of Nephrops norvegicus

“…Year-to-year variations in density may account for some of this, but when sampling year was taken into account, the percentage of silt-clay explained at best 42% of the variation in the data (see Figure 2.3), which was of a similar order to the model fit of Campbell et al (2009a). Year-to-year variations in density may account for some of this, but when sampling year was taken into account, the percentage of silt-clay explained at best 42% of the variation in the data (see Figure 2.3), which was of a similar order to the model fit of Campbell et al (2009a).…”

“…In a comparison of Nephrops fishing grounds, the North Minch conformed to the dome-shaped density-sediment response although the relationship at the Fladen grounds was more linear (Campbell et al, 2009a). The sediments at the Fladen grounds were slightly coarser and less well sorted than at North Minch; accordingly, neither extremely high silt-clay sediments nor densities were observed there.…”

“…The sediments at the Fladen grounds were slightly coarser and less well sorted than at North Minch; accordingly, neither extremely high silt-clay sediments nor densities were observed there. But maximum density was higher in the Aran grounds ($1.25 burrows m À2 ) compared with $0.75 burrows m À2 at North Minch and only $0.4 burrows m À2 in the Fladen grounds (Campbell et al, 2009a). Consulting the plot of the Aran grounds in the west of Ireland (Figure 2.3), the Nephrops density slope may have an inflexion in sediments with $60% silt plus clay, which was a similar range as at North Minch and Fladen grounds (Campbell et al, 2009a).…”