3. Results
3.1. Overall catch summary
Between 2007 and 2010, 306 valid tows were conducted with
scyphozoan jellyfish present in 95.4% of tows (Table 2, Fig. 2). The
mean volume filtered (X ± SD) was 4671 ± 1789 m3 (range
1412e11 720 m3
). Depth in the sampling area was between 16 and
130 m (mean ¼ 61.5 ± 30.7 m). The summary of catches for the
entire survey (leg 1 and 2) each year is presented in Table 2. Only
data from stations sampled from the eastern region and the second
sampling of the western region were analysed.
Between 2007 and 2010 the annual median (±IQR, inter-quartile
range) total jellyfish volume-standardised catch biomass were:
0.37 ± 0.86; 0.19 ± 0.63; 0.52 ± 2.57; 0.92 ± 0.98 g m3 (Table 2);
leading to median biomass densities of: 18.6 ± 34.87; 8.16 ± 50.18;
23.5 ± 128.36; and 42.4 ± 75.79 g m2 (or t km2
). Overall (4 years
combined), Aurelia aurita represented 77.7% of the catches (wet
mass) and Cyanea spp. (Cyanea lamarckii and Cyanea capillata)
21.5%, but the contribution of each species varied greatly between
regions and between years (Table 2). The long term overall median
biomass densities of A. aurita and Cyanea spp. were 5.7 g m2
(range of annual median 0.75e12.0) and 5.0 g m2 (range 2.6e13.2)
respectively. The only other scyphozoan caught was the compass
jellyfish (Chrysaora hysoscella), but it was only marginally present
(16 individuals in 2007; 1 in 2009, and 1 in 2010), except in 2008
when 131 individuals were caught (but at only 2 stations).
3.2
3. Results3.1. Overall catch summaryBetween 2007 and 2010, 306 valid tows were conducted withscyphozoan jellyfish present in 95.4% of tows (Table 2, Fig. 2). Themean volume filtered (X ± SD) was 4671 ± 1789 m3 (range1412e11 720 m3). Depth in the sampling area was between 16 and130 m (mean ¼ 61.5 ± 30.7 m). The summary of catches for theentire survey (leg 1 and 2) each year is presented in Table 2. Onlydata from stations sampled from the eastern region and the secondsampling of the western region were analysed.Between 2007 and 2010 the annual median (±IQR, inter-quartilerange) total jellyfish volume-standardised catch biomass were:0.37 ± 0.86; 0.19 ± 0.63; 0.52 ± 2.57; 0.92 ± 0.98 g m3 (Table 2);leading to median biomass densities of: 18.6 ± 34.87; 8.16 ± 50.18;23.5 ± 128.36; and 42.4 ± 75.79 g m2 (or t km2). Overall (4 yearscombined), Aurelia aurita represented 77.7% of the catches (wetmass) and Cyanea spp. (Cyanea lamarckii and Cyanea capillata)21.5%, but the contribution of each species varied greatly betweenregions and between years (Table 2). The long term overall medianbiomass densities of A. aurita and Cyanea spp. were 5.7 g m2(range of annual median 0.75e12.0) and 5.0 g m2 (range 2.6e13.2)respectively. The only other scyphozoan caught was the compassjellyfish (Chrysaora hysoscella), but it was only marginally present(16 individuals in 2007; 1 in 2009, and 1 in 2010), except in 2008when 131 individuals were caught (but at only 2 stations).3.2
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