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Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela
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 (Sar...
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2022
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| _version_ | 1867613164437241856 |
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| access_status_str | Open Access |
| author | Groenewald, Grea |
| author2 | Moloney, Coleen L |
| author_browse | Groenewald, Grea Moloney, Coleen L |
| author_facet | Moloney, Coleen L Groenewald, Grea |
| author_sort | Groenewald, Grea |
| collection | Thesis |
| description | 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. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/35555 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:31:47.142Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/35555 Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela Groenewald, Grea Moloney, Coleen L van der Lingen, Carl D Biological Sciences 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. 2022-01-21T10:21:24Z 2022-01-21T10:21:24Z 2021 2022-01-20T11:11:37Z Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/35555 eng application/pdf Department of Biological Sciences Faculty of Science |
| spellingShingle | Biological Sciences Groenewald, Grea Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela |
| thesis_degree_str | Doctoral |
| title | Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela |
| title_full | Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela |
| title_fullStr | Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela |
| title_full_unstemmed | Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela |
| title_short | Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela |
| title_sort | developing dynamic energy budget deb models for small pelagic fishes in the southern benguela |
| topic | Biological Sciences |
| url | http://hdl.handle.net/11427/35555 |
| work_keys_str_mv | AT groenewaldgrea developingdynamicenergybudgetdebmodelsforsmallpelagicfishesinthesouthernbenguela |