4.6 Snow crab effect on benthos

Interactions, drivers and pressures 2016
Typography
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In most of the measured years, the benthos biomass in the northeast part of the Barents Sea (NE) was above the total Barents Sea mean (Figure 4.6.1). But from 2013 and ongoing, the mean biomass (see also black arrows in Figure 3.4.3 lower panel) was reducing, and was record low (<20 kg/n.ml) in 2016, and below the total Barents Sea mean.

Figure 4.6.1. The interannually mean benthos biomass fluctuation in the NE (blue, box is total mean biomass, diamonds is without the biomass of the snow crab). The dotted line is the total Barents Sea mean biomass.Figure 4.6.1. The interannually mean benthos biomass fluctuation in the NE (blue, box is total mean biomass, diamonds is without the biomass of the snow crab). The dotted line is the total Barents Sea mean biomass.

The area of reduced benthos biomass after 2013 are overlapping with the maximum distribution of the snow crab (Figure 3.4.3.), the period of maximum consumption/killing (Figure 4.6.2).

Figure 4.6.2. The mean annual consumption/killing of benthos (g/m2) by the snow crab population. The abundance of the snow crab population was given by the Ecosystem Survey in the Barents Sea (Manushin, 2016).Figure 4.6.2. The mean annual consumption/killing of benthos (g/m2) by the snow crab population. The abundance of the snow crab population was given by the Ecosystem Survey in the Barents Sea (Manushin, 2016).

The spatial impact on benthos biomass done by the snow crab predation (Manushin, 2016) shows that the highest impact is located west of Novaya Zemlya (4.6.3) and in an area dominated by the polychaete Spiochaetopterus typicus (deeper areas with adult snow crabs) and the bivalve Macoma calcarea (shallower areas with juvenile snow crabs) (Zacharot et al., 2016).

Figure 4.6.3. Total biomass (g/m2) of the benthos consumed/killed by the snow crab population during a nine-year period (2005–2014) (Manushin, 2016).Figure 4.6.3. Total biomass (g/m2) of the benthos consumed/killed by the snow crab population during a nine-year period (2005–2014) (Manushin, 2016).

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