| dc.contributor.author | Hagen, Nils Thorstein. | en_US |
| dc.date.accessioned | 2014-10-21T12:34:48Z | |
| dc.date.available | 1990 | |
| dc.date.issued | 1990 | en_US |
| dc.identifier.other | AAINN64579 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55229 | |
| dc.description | Outbreak initiation, the formation of destructive feeding aggregations, was studied by quantifying the green sea urchins' patterns of feeding, aggregation, and microhabitat utilization in laboratory tanks. Maximum levels of aggregation, exposure and feeding were observed in treatments with a high density of starved, large urchins in the absence of refuges and predators. The formation of exposed feeding aggregations was inhibited by the presence of Atlantic wolffish, Anarhichas lupus, and to a lesser extent by increased spatial heterogeneity, a prehistory of plentiful food supply, winter conditions, and the presence of decapod predators, Homarus americanus and Cancer irroratus. | en_US |
| dc.description | Wolffish and decapods demonstrated functional predator responses, i.e. increased consumption of urchins, when prey density was experimentally inflated. The two kinds of predators had similar diurnal consumption rates of small urchins, but wolffish excelled at exploiting large urchins. | en_US |
| dc.description | Effects of predation, recruitment, and urchin behaviour on the outbreak dynamics of S. droebachiensis were explored in a simulation model. The model suggests that seasonally migratory visual predators (e.g. wolffish), which presumably are incapable of exploiting cryptic prey, have little effect on the urchins overall capacity to destroy seaweed and maintain barren grounds, whereas perpetually present predators (e.g. decapods) have a theoretical potential to prevent or terminate outbreaks, irrespective of their ability to exploit cryptic prey. However, the effects of a given level of predation could always be nullified by increasing the recruitment density of the urchins. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1990. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biology, Ecology. | en_US |
| dc.subject | Biology, Oceanography. | en_US |
| dc.title | Outbreak dynamics of the green sea urchin Strongylocentrotus droebachiensis O. F. Muller. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
