Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela

dc.contributor.advisorMoloney, Coleen L
dc.contributor.advisorvan der Lingen, Carl D
dc.contributor.authorGroenewald, Grea
dc.date.accessioned2022-01-21T10:21:24Z
dc.date.available2022-01-21T10:21:24Z
dc.date.issued2021
dc.date.updated2022-01-20T11:11:37Z
dc.description.abstractDynamic energy budget models are useful for describing energy flow in individual organisms as functions of their state (e.g., age, size, and energetic reserves) and environment (e.g., food and temperature). Anchovy (Engraulis encrasicolus), redeye round herring (Etrumeus whiteheadi) and sardine (Sardinops sagax) are short-lived fish species co-occurring in the Southern Benguela upwelling system, where they experience marked environmental variability. This study developed full life cycle dynamic energy budget models of these species in the Southern Benguela, which could be compared to the same or similar species in other ecosystems and investigated trade-offs between temperature and feeding conditions in influencing the growth and reproductive outputs of the three species. The key hypothesis was that there would be niche differences among bioenergetic factors for the three species that allow them to cooccur. Models were created and calibrated using published information and survey data (recruitment, biomass, weight-at-length) from 2012-2016. Best visual fit values were estimated for five parameters, using von Bertalanffy growth models and length-weight relationships of each species. Results indicated that redeye round herring invested less than anchovy and sardine in reproductive storage capacity (larger maintenance ratio) and had lower assimilation rates. Sardine had higher structural growth costs than anchovy and redeye round herring. Larval redeye round herring took longer to reach metamorphosis than anchovy and sardine. In all three species, decreased growth rates of larvae in cool waters were mitigated by increased growth from good food availability. Good feeding condition associated with cooler temperatures halved the time spent as recruits in all three species. Thus, increased growth rates from good food availability outweighed decreased growth rates from cool temperatures and resulted in higher egg batch production in adults. Comparisons of Southern Benguela anchovy and sardine to similar species in other ecosystems showed differences in core parameters between regions because of the influence of environmental inputs and species differences, indicating that model parameters may not be species-specific or transferable between ecosystems. Differential responses of small pelagic fish species to environmental factors help in understanding the variable population dynamics of these species and can help predict the impacts of climate change.
dc.identifier.apacitationGroenewald, G. (2021). <i>Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela</i>. (). ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/35555en_ZA
dc.identifier.chicagocitationGroenewald, Grea. <i>"Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela."</i> ., ,Faculty of Science ,Department of Biological Sciences, 2021. http://hdl.handle.net/11427/35555en_ZA
dc.identifier.citationGroenewald, G. 2021. Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela. . ,Faculty of Science ,Department of Biological Sciences. http://hdl.handle.net/11427/35555en_ZA
dc.identifier.ris TY - Doctoral Thesis AU - Groenewald, Grea AB - Dynamic energy budget models are useful for describing energy flow in individual organisms as functions of their state (e.g., age, size, and energetic reserves) and environment (e.g., food and temperature). Anchovy (Engraulis encrasicolus), redeye round herring (Etrumeus whiteheadi) and sardine (Sardinops sagax) are short-lived fish species co-occurring in the Southern Benguela upwelling system, where they experience marked environmental variability. This study developed full life cycle dynamic energy budget models of these species in the Southern Benguela, which could be compared to the same or similar species in other ecosystems and investigated trade-offs between temperature and feeding conditions in influencing the growth and reproductive outputs of the three species. The key hypothesis was that there would be niche differences among bioenergetic factors for the three species that allow them to cooccur. Models were created and calibrated using published information and survey data (recruitment, biomass, weight-at-length) from 2012-2016. Best visual fit values were estimated for five parameters, using von Bertalanffy growth models and length-weight relationships of each species. Results indicated that redeye round herring invested less than anchovy and sardine in reproductive storage capacity (larger maintenance ratio) and had lower assimilation rates. Sardine had higher structural growth costs than anchovy and redeye round herring. Larval redeye round herring took longer to reach metamorphosis than anchovy and sardine. In all three species, decreased growth rates of larvae in cool waters were mitigated by increased growth from good food availability. Good feeding condition associated with cooler temperatures halved the time spent as recruits in all three species. Thus, increased growth rates from good food availability outweighed decreased growth rates from cool temperatures and resulted in higher egg batch production in adults. Comparisons of Southern Benguela anchovy and sardine to similar species in other ecosystems showed differences in core parameters between regions because of the influence of environmental inputs and species differences, indicating that model parameters may not be species-specific or transferable between ecosystems. Differential responses of small pelagic fish species to environmental factors help in understanding the variable population dynamics of these species and can help predict the impacts of climate change. DA - 2021_ DB - OpenUCT DP - University of Cape Town KW - Biological Sciences LK - https://open.uct.ac.za PY - 2021 T1 - Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela TI - Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela UR - http://hdl.handle.net/11427/35555 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/35555
dc.identifier.vancouvercitationGroenewald G. Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela. []. ,Faculty of Science ,Department of Biological Sciences, 2021 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/35555en_ZA
dc.language.rfc3066eng
dc.publisher.departmentDepartment of Biological Sciences
dc.publisher.facultyFaculty of Science
dc.subjectBiological Sciences
dc.titleDeveloping dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationlevelPhD
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