Benthic Communities at Horns Rev Before, During and After Con

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Horns Rev. Benthic communities Page 68 Even though the edible crab (Cancer pagurus) only constituted less than 1% of the total abundance, this species showed some interesting characteristics. In March, Cancer pagurus generally showed a very scattered distribution; although juveniles were registered in relatively low numbers at all depth zones at the monopiles, larger individuals were less frequently observed by divers along the transect surveys than in the September surveys. In September large numbers of juveniles were found in all depth zones at the monopiles (Figure 3.27). The highest mean abundance of 950 ind./m 2 was found in depth zone 1-3 m in September 2004 and abundances over 1,900 ind./m 2 were registered at turbine site 55. From 2003 to 2005, a considerable increase in total biomass was found for Cancer pagurus, which was a result of increasing abundance and an increase in average individual body weight from 1.52 mg(dw) in September 2003 to 44.16 mg(dw) in September 2005. The average individual body weight of the initial population of Cancer pagurus at the monopiles in March 2003 was 17.52 mg(dw). In March 2005, three size classes of juvenile crabs were found. One probably representing the 0 group from 5-11 mm, the second representing the 1+ group from 20-23 mm and the third probably representing the 2+ group from approximately 40 mm. 0 m 0-1 m 1-3 m 3-5 m 5-7 m >7 m Cancer pagurus March 03 Sept. 03 March 04 Sept. 04 March 05 Sept. 05 0 100 200 300 400 500 600 700 800 No/m² Figure 3.28.Depth distribution of Cancer pagurus at the monopiles. Photo 16. Adult Cancer pagurus at the scour protection.. Juveniles of other crab species like the masked crab (Corystes cassivelaunus), the long clawed porcelain crab (Pisidia longicornis) and the bristly crab (Pilumnus hirtellus) were occasionally found on the monopiles. Also juveniles of the northern sea urchin (Strongylocentrotus droebachiensis) were found in low numbers. Only an insignificant contribution to the total biomass of less than 0.5% was made by the sea anemones Metridium senile, Sargartia elegans, Sargartiogeton laceratus and Urticina feline, although they all were found on the monopiles. They were locally found in a combined coverage up to 45% with a biomass (dw) contribution of more than 50%. The most common was Metridium senile and the combined coverage of the sea anemones increased at the monopiles with increasing depth. Relatively high coverage in all depth zones at the monopiles, locally up to 50%, were also found for the oaten pipes hydroid (Tubularia indivisa). The predator of this species, the sea slug (Facelina bostoniensis), together with other sea slugs Polycera quadrilineata, Aeolidiae papillosa and Onchidoris muricata were relatively abundant and frequently recorded. Doc. No. 2572-03-005 rev. 4
Horns Rev. Benthic communities Page 69 3.3.3. Fish Table 3.17. Fish species observed during the surveys in 2003-2005. Common name Scientific name 2003 2004 2005 Number of sites Max. Abundance Number of sites Max. Abundance Number of sites Max. Abundance European sprat Sprattus sprattus 1 O Atlantic cod Gadus morhua 6 R 2 R 5 R Bib (Pouting) Trisopterus luscus 4 R 3 R 3 R Whiting Merlangus merlangus 2 O Pollock (Saithe) Pollachius virens 1 O 1 O 3 R Broad-nosed pipefish Syngnathus typhle 1 O Shorthorn sculpin Myoxocephalus scorpius 5 R 4 R 4 R Hooknose Agonus cataphractus 5 R 4 O 1 O Longspined bullhead Taurulus bubaris 2 O 1 O Horse mackerel Trachurus trachurus 2 R Stribed red mullet Mullus surmuletus 1 O Ballan wrasse Labrus bergylta 1 O Corkwing wrasse Symphodus melops 6 R Goldsinny-wrasse Ctenolabrus rupestris 1 R 6 ∞ 6 ∞ Lumpsucker Cyclopteus lumpus 1 O Viviparous blenny Zoarces viviparous 2 R 1 O Small sandeel Ammodytes tobianus 2 O 1 ∞ Rock gunnel Pholis gunnellus 6 R 6 R 6 ∞ Dragonet Callionymus lyra 5 O 3 R Sand goby Pomatoschistus minutus 4 ∞ 6 ∞ 2 O Painted goby Pomatoschistus pictus 2 R A total of 22 species have been registered during the surveys on the hard bottom substrate at the Horns Rev Offshore Wind Farm since the erection of the wind turbines in 2002. Besides the fish observed in the area close to the turbine structures inclusive of the scour protections, as presented in Table 3.17, Atlantic mackerel (Scomber scombrus) were observed in the area between the turbines in 2004. Whiting was only caught during in the test fishing in 2003 and not observed by the divers. Photo 17. Bib (pouting) Trisopterus luscus. Photo 18. Atlantic cod Gadus morhua. Photo 19. Goldsinny-wrasse Ctenolabrus rupestris. Photo 20. Goldsinny-wrasse Ctenolabrus rupestris and the edible crab Cancer pagurus. Doc. No. 2572-03-005 rev. 4
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Benthic Communities at Horns Rev Before, During and After Con

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