Big fish start small
| dc.contributor.author | Leach, Clinton, author | |
| dc.contributor.author | Webb, Colleen, advisor | |
| dc.contributor.author | Poff, LeRoy, committee member | |
| dc.contributor.author | Hooten, Mevin, committee member | |
| dc.contributor.author | Noon, Barry, committee member | |
| dc.date.accessioned | 2020-06-22T11:53:35Z | |
| dc.date.available | 2021-06-15T11:53:35Z | |
| dc.date.issued | 2020 | |
| dc.description.abstract | Individuals of the same species often participate in substantially different predator-prey interactions. In many species, these differences are driven by individual size and the ontogenetic niche shifts that occur as an individual grows. This intraspecific size-structure can have profound consequences for our understanding of food web structure and community dynamics. These consequences are particularly important in exploited marine ecosystems where fisheries often target the largest individuals and size-structured feedbacks have been implicated in preventing collapsed fisheries from recovering. In this dissertation, we explored the consequences of this size-structure for the Scotian Shelf and Gulf of Alaska ecosystems. To understand how the collapse of the cod stock on the Scotian Shelf may have fed back on the demographic landscape of cod, we developed a model to estimate how the length-dependent growth and survival of cod changed before and after the collapse. We found that forage fish, released from top-down control, likely played an important role in limiting cod access to food, with consequences for cod survival and the potential for long term recovery. To better understand the community context of these changes, we developed a multivariate autoregressive model to capture how shifts in species' size distributions may have driven changes in the interspecific interaction landscape on the Scotian Shelf. This study found further evidence for the role of forage fish in preventing cod recovery, and linked the corresponding changes in interaction structure to an increase in the overall instability of the system. Lastly, we explored the community structure of ontogenetic niche shifts in the Gulf of Alaska by developing a model to identify trophic groups — collections of individuals with similar interaction patterns — in an individual-level food web assembled from stomach contents data. The identified trophic groups revealed substantial overlap in the ontogenetic trajectories of Gulf of Alaska predator species and the low-dimensional structure of the individual-level food web. This work represents a step toward incorporating individual-level processes into modeling frameworks that can be used to both inform existing theory with data and to inform fisheries management. Specifically, this research highlights the different trophic roles that individuals of a species occupy as they grow, and the importance of growth in moving individuals up the food web and maintaining community structure and stability. Our findings suggest that disruptions to this flow and the resulting loss of large individuals can generate a cascade of effects through the system, leading to fundamental reorganization and increased instability. | |
| dc.format.medium | born digital | |
| dc.format.medium | doctoral dissertations | |
| dc.identifier | Leach_colostate_0053A_15876.pdf | |
| dc.identifier.uri | https://hdl.handle.net/10217/208523 | |
| dc.language | English | |
| dc.language.iso | eng | |
| dc.publisher | Colorado State University. Libraries | |
| dc.relation.ispartof | 2020- | |
| dc.rights | Copyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright. | |
| dc.subject | fisheries | |
| dc.subject | ontogenetic niche shifts | |
| dc.subject | species interactions | |
| dc.subject | food webs | |
| dc.subject | demography | |
| dc.subject | predator-prey interactions | |
| dc.title | Big fish start small | |
| dc.type | Text | |
| dcterms.embargo.expires | 2021-06-15 | |
| dcterms.embargo.terms | 2021-06-15 | |
| dcterms.rights.dpla | This Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). | |
| thesis.degree.discipline | Ecology | |
| thesis.degree.grantor | Colorado State University | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy (Ph.D.) |
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