2021
Georgakakos, Philip B.
2021.
Abstract | Links | BibTeX | Tags: aquatic ecosystems, ERCZO, O. mykiss, pacific lamprey, Rana boylii, river communities, Sacramento pikeminnow, steelhead trout
@phdthesis{Georgakakos2021,
title = {Impacts of Native and Introduced Species on Native Vertebrates in a Salmon-Bearing River Under Contrasting Thermal and Hydrologic Regimes},
author = {Philip B. Georgakakos},
url = {https://media.proquest.com/media/hms/PFT/2/1qTlI?_s=%2Bx7JvOkubzD%2B%2Bv%2B6Qi79aySM%2FUc%3D},
year = {2021},
date = {2021-03-01},
abstract = {As organisms undergo life history transitions, track resources, avoid stress, and evade death, they distribute themselves across landscapes. Organismal co-occurrence sets the stage for biotic interactions, which can feedback to control the distribution and abundance of interacting species in ecological communities. Classically, competition and bottom-up forces have been thought to be the most important drivers of community structure, however, examples of predation, parasitism, mutualism, and facilitation highlight the ubiquity and importance of these other interactions. In freshwaters, anthropogenic impacts, especially species introductions and climate warming, have resulted in novel species assemblages, with altered webs of interactions compared to historic conditions. Human management often seeks to provide conditions that favor native species and inhibit non-natives. Success requires an understanding species interactions and their roles in community dynamics. In my first chapter, I describe the distributional dynamics of the assemblage of aquatic fishes, reptiles and amphibians in the South Fork Eel River. In Chapter 2, I describe the seasonal migration of an introduced predatory fish, Sacramento Pikeminnow (Ptychocheilus grandis), and how climate warming and water withdrawals could increase their negative impact on rearing native salmonids and other fauna.In Chapter 3, my colleagues and I explore the positive interactions between Pacific Lamprey(Entosphenus tridentatus), juvenile Steelhead trout (Oncorhynchus mykiss), and Foothill Yellow-legged Frogs(Rana boylii). These case studies emphasize the need to consider ecological interactions, and in general, community ecology thinking, as we try to restore and manage ecosystems},
keywords = {aquatic ecosystems, ERCZO, O. mykiss, pacific lamprey, Rana boylii, river communities, Sacramento pikeminnow, steelhead trout},
pubstate = {published},
tppubtype = {phdthesis}
}
As organisms undergo life history transitions, track resources, avoid stress, and evade death, they distribute themselves across landscapes. Organismal co-occurrence sets the stage for biotic interactions, which can feedback to control the distribution and abundance of interacting species in ecological communities. Classically, competition and bottom-up forces have been thought to be the most important drivers of community structure, however, examples of predation, parasitism, mutualism, and facilitation highlight the ubiquity and importance of these other interactions. In freshwaters, anthropogenic impacts, especially species introductions and climate warming, have resulted in novel species assemblages, with altered webs of interactions compared to historic conditions. Human management often seeks to provide conditions that favor native species and inhibit non-natives. Success requires an understanding species interactions and their roles in community dynamics. In my first chapter, I describe the distributional dynamics of the assemblage of aquatic fishes, reptiles and amphibians in the South Fork Eel River. In Chapter 2, I describe the seasonal migration of an introduced predatory fish, Sacramento Pikeminnow (Ptychocheilus grandis), and how climate warming and water withdrawals could increase their negative impact on rearing native salmonids and other fauna.In Chapter 3, my colleagues and I explore the positive interactions between Pacific Lamprey(Entosphenus tridentatus), juvenile Steelhead trout (Oncorhynchus mykiss), and Foothill Yellow-legged Frogs(Rana boylii). These case studies emphasize the need to consider ecological interactions, and in general, community ecology thinking, as we try to restore and manage ecosystems
1992
Power, M. E.; Marks, J. C.; Parker, Michael S.
Variation in the vulnerability of prey to different predators: Community-level consequences Journal Article
In: Ecology, vol. 73, no. 6, pp. 2218-2223, 1992.
Abstract | Links | BibTeX | Tags: anti-predator defenses, attached algae, chironomidae, Cladophora, fish, food webs, omnivory, predatory invertebrates, river communities, strong interactors, trophic cascades
@article{Power1992,
title = {Variation in the vulnerability of prey to different predators: Community-level consequences},
author = {M. E. Power and J. C. Marks and Michael S. Parker},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_1992_Eco3.pdf},
doi = {10.2307/1941469},
year = {1992},
date = {1992-12-00},
journal = {Ecology},
volume = {73},
number = {6},
pages = {2218-2223},
abstract = {Midge larvae (Diptera, Chironomidae) that weave filamentous algae into
retreats or tufts, are dominant primary consumers in a river food web. In a previous
study, densities of tuft-weaving midges increased in the presence of large fish. In the absence of large fish, midges decreased as densities of predatory invertebrates built up, and higher standing crops of algae were maintained. To examine the mechanisms underlying these dynamics, we compared the vulnerability of tuft-weaving midges (naked or in algal tufts) to fish and predatory invertebrates, in field and laboratory experiments. When midges were exposed for 1 h in the river to fish, 15 out of 15 midges in tufts survived, while 15 of 15 naked midges were consumed. Tufts afforded only partial protection to midges exposed to invertebrate predators, however. After 1 h, enhancement of survivorship by tufts was moderately significant for midges exposed to aeshnids, and insignificant for midges exposed to lestids and naucorids. We suggest that the vulnerability of tuft-weaving midges to invertebrate predators, and their relative invulnerability to fish, sets the stage for trophic cascades observed in this system. Fish, by consuming small predators, release midges, which graze down algae. The strong effects of fish as fourth-level consumers would not be predicted from their diets, in which algivorous mayflies dominate (>60% of the insect biomass found in each of the two most common fish species). Nevertheless, fish in this food web act as fourth-level, rather than third-level, consumers because of the differential vulnerability of one guild of primary consumers, which, when released from predation, can suppress plants.},
keywords = {anti-predator defenses, attached algae, chironomidae, Cladophora, fish, food webs, omnivory, predatory invertebrates, river communities, strong interactors, trophic cascades},
pubstate = {published},
tppubtype = {article}
}
Midge larvae (Diptera, Chironomidae) that weave filamentous algae into
retreats or tufts, are dominant primary consumers in a river food web. In a previous
study, densities of tuft-weaving midges increased in the presence of large fish. In the absence of large fish, midges decreased as densities of predatory invertebrates built up, and higher standing crops of algae were maintained. To examine the mechanisms underlying these dynamics, we compared the vulnerability of tuft-weaving midges (naked or in algal tufts) to fish and predatory invertebrates, in field and laboratory experiments. When midges were exposed for 1 h in the river to fish, 15 out of 15 midges in tufts survived, while 15 of 15 naked midges were consumed. Tufts afforded only partial protection to midges exposed to invertebrate predators, however. After 1 h, enhancement of survivorship by tufts was moderately significant for midges exposed to aeshnids, and insignificant for midges exposed to lestids and naucorids. We suggest that the vulnerability of tuft-weaving midges to invertebrate predators, and their relative invulnerability to fish, sets the stage for trophic cascades observed in this system. Fish, by consuming small predators, release midges, which graze down algae. The strong effects of fish as fourth-level consumers would not be predicted from their diets, in which algivorous mayflies dominate (>60% of the insect biomass found in each of the two most common fish species). Nevertheless, fish in this food web act as fourth-level, rather than third-level, consumers because of the differential vulnerability of one guild of primary consumers, which, when released from predation, can suppress plants.
retreats or tufts, are dominant primary consumers in a river food web. In a previous
study, densities of tuft-weaving midges increased in the presence of large fish. In the absence of large fish, midges decreased as densities of predatory invertebrates built up, and higher standing crops of algae were maintained. To examine the mechanisms underlying these dynamics, we compared the vulnerability of tuft-weaving midges (naked or in algal tufts) to fish and predatory invertebrates, in field and laboratory experiments. When midges were exposed for 1 h in the river to fish, 15 out of 15 midges in tufts survived, while 15 of 15 naked midges were consumed. Tufts afforded only partial protection to midges exposed to invertebrate predators, however. After 1 h, enhancement of survivorship by tufts was moderately significant for midges exposed to aeshnids, and insignificant for midges exposed to lestids and naucorids. We suggest that the vulnerability of tuft-weaving midges to invertebrate predators, and their relative invulnerability to fish, sets the stage for trophic cascades observed in this system. Fish, by consuming small predators, release midges, which graze down algae. The strong effects of fish as fourth-level consumers would not be predicted from their diets, in which algivorous mayflies dominate (>60% of the insect biomass found in each of the two most common fish species). Nevertheless, fish in this food web act as fourth-level, rather than third-level, consumers because of the differential vulnerability of one guild of primary consumers, which, when released from predation, can suppress plants.
Power, M. E.
Habitat heterogeneity and the functional significance of fish in river food webs Journal Article
In: Ecology, vol. 73, no. 5, pp. 1675-1688, 1992.
Abstract | Links | BibTeX | Tags: Benthos, fish; food webs, omnivore: refuges, river communities, strong interactions, substrate heterogeneity: trophic cascades.
@article{Power1992b,
title = {Habitat heterogeneity and the functional significance of fish in river food webs},
author = {M. E. Power},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_1992_Eco.pdf},
doi = {10.2307/1940019},
year = {1992},
date = {1992-10-00},
journal = {Ecology},
volume = {73},
number = {5},
pages = {1675-1688},
abstract = {Predation by fish (roach, Hesperoleucas symmetricus, and steelhead, Oncorhynchus mykiss) produced strong cascading effects on biota associated with boulder-bedrock substrates in pools of a northern California river, but not on gravel-dwelling biota. Enclosure-exclosure experiments in the South Fork Eel River of northern California (39044'N, 123039' W) showed that fish, by suppressing densities of damselfly nymphs and other small predators, released algivorous chironomids (Pseudochironomous richardsoni) from predation. Chironomids in turn dramatically reduced algal standing crops. In contrast, fish had little effect on algae or invertebrates associated with gravel. Gravel-dwelling heptageniid mayflies were behaviorally inhibited from using tops of stones in fish enclosures, and stone
surfaces had more chironomid tubes in fish enclosures than in fish exclosures. However, no effects on epilithic algae or densities of invertebrates comparable to those of biota on boulder-bedrock substrates were detected. These spatially varying predator effects in a river parallel results from marine benthic systems, where strong effects of large predators documented for rocky intertidal habitats and unvegetated soft bottoms are not conspicuous in seagrass beds.},
keywords = {Benthos, fish; food webs, omnivore: refuges, river communities, strong interactions, substrate heterogeneity: trophic cascades.},
pubstate = {published},
tppubtype = {article}
}
Predation by fish (roach, Hesperoleucas symmetricus, and steelhead, Oncorhynchus mykiss) produced strong cascading effects on biota associated with boulder-bedrock substrates in pools of a northern California river, but not on gravel-dwelling biota. Enclosure-exclosure experiments in the South Fork Eel River of northern California (39044’N, 123039′ W) showed that fish, by suppressing densities of damselfly nymphs and other small predators, released algivorous chironomids (Pseudochironomous richardsoni) from predation. Chironomids in turn dramatically reduced algal standing crops. In contrast, fish had little effect on algae or invertebrates associated with gravel. Gravel-dwelling heptageniid mayflies were behaviorally inhibited from using tops of stones in fish enclosures, and stone
surfaces had more chironomid tubes in fish enclosures than in fish exclosures. However, no effects on epilithic algae or densities of invertebrates comparable to those of biota on boulder-bedrock substrates were detected. These spatially varying predator effects in a river parallel results from marine benthic systems, where strong effects of large predators documented for rocky intertidal habitats and unvegetated soft bottoms are not conspicuous in seagrass beds.
surfaces had more chironomid tubes in fish enclosures than in fish exclosures. However, no effects on epilithic algae or densities of invertebrates comparable to those of biota on boulder-bedrock substrates were detected. These spatially varying predator effects in a river parallel results from marine benthic systems, where strong effects of large predators documented for rocky intertidal habitats and unvegetated soft bottoms are not conspicuous in seagrass beds.