Nearshore marine habitats provide critical nursery grounds for juvenile fishes, but
their functional role requires the consideration of the impacts of spatial connectivity. This
thesis examines nursery function in seagrass habitats through a marine landscape
(“seascape”) lens, focusing on the spatial interactions between habitats, and their effects
on population and trophic dynamics associated with nursery function to rockfish
(Sebastes spp.). In the temperate Pacific Ocean, rockfish depend on nearshore habitats
after an open-ocean, pelagic larval period. I investigate the role of two important spatial
attributes, habitat adjacency and complexity, on rockfish recruitment to seagrass
meadows, and the provision of subsidies to rockfish food webs. To test for these effects,
underwater visual surveys and collections of young-of-the-year (YOY) Copper Rockfish
recruitment (summer 2015) were compared across adjacent seagrass, kelp forest, and
sand habitats within a nearshore seascape on the Central Coast of British Columbia.
Recruitment was positively influenced by the structural complexity of seagrass and
adjacency to kelp forest sites, however a negative interaction between seagrass
complexity and kelp forest adjacency suggests that predation modifies Copper Rockfish
recruitment densities. In addition, using δ13C and δ15N isotopes to determine the basal
contributions to seagrass food webs, kelp-derived nutrients were on average 47% ± 0.4 of
YOY Copper Rockfish diets, which was 3x and 67x greater than the contribution of
autochthonous seagrass production (seagrass epiphyte and seagrass blades, respectively).
YOY Copper Rockfish diets in seagrass adjacent to sand habitats had the greatest
amounts of kelp-derived nutrients and harpacticoid copepods, and concurrently had lower
body condition compared to rockfish in the seagrass kelp edges and interior, feeding
predominantly on seagrass epiphytes and calanoid copepods. This thesis provides further
evidence that temperate seagrasses are nurseries for rockfish and that spatial elements of
seascapes, including connectivity via habitat adjacency and variability in habitat
structure, alter the recruitment and diets of rockfish in seagrass habitats. These seascape
nursery effects are important considerations for marine planning, especially given the
global decline of nearshore habitats. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/7943 |
| Date | 24 April 2017 |
| Creators | Olson, Angeleen |
| Contributors | Juanes, Francis, Hessing-Lewis, Margot |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | Available to the World Wide Web, http://creativecommons.org/licenses/by-sa/2.5/ca/ |
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