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Predation on the Invasive Copepod, Pseudodiaptomus forbesi, and Native Zooplankton in the Lower Columbia River: An Experimental Approach to Quantify Differences in Prey-Specific Feeding Rates.

Adams JB, Bollens SM, Bishop JG - PLoS ONE (2015)

Bottom Line: In two-prey experiments, chinook salmon and northern pikeminnow both strongly selected native cladocerans (Daphnia retrocurva) over P. forbesi, and moreover, northern pikeminnow selected native Cyclopidae spp. over P. forbesi.On the other hand, in two-prey experiments, chinook salmon, three-spined stickleback and mysids were non- selective with respect to feeding on native cyclopoid copepods versus P. forbesi.Our results indicate that all four native predators in the Columbia River Estuary can consume the invasive copepod, P. forbesi, but that some predators select for native zooplankton over P. forbesi, most likely due to one (or both) of two possible underlying casual mechanisms: 1) differential taxon-specific prey motility and escape responses (calanoids > cyclopoids > daphnids) or 2) the invasive status of the zooplankton prey resulting in naivety, and thus lower feeding rates, of native predators feeding on invasive prey.

View Article: PubMed Central - PubMed

Affiliation: School of the Environment, Washington State University, Vancouver, Washington, United States of America.

ABSTRACT
Invasive planktonic crustaceans have become a prominent feature of aquatic communities worldwide, yet their effects on food webs are not well known. The Asian calanoid copepod, Pseudodiaptomus forbesi, introduced to the Columbia River Estuary approximately 15 years ago, now dominates the late-summer zooplankton community, but its use by native aquatic predators is unknown. We investigated whether three species of planktivorous fishes (chinook salmon, three-spined stickleback, and northern pikeminnow) and one species of mysid exhibited higher feeding rates on native copepods and cladocerans relative to P. forbesi by conducting `single-prey' feeding experiments and, additionally, examined selectivity for prey types with `two-prey' feeding experiments. In single-prey experiments individual predator species showed no difference in feeding rates on native cyclopoid copepods (Cyclopidae spp.) relative to invasive P. forbesi, though wild-collected predators exhibited higher feeding rates on cyclopoids when considered in aggregate. In two-prey experiments, chinook salmon and northern pikeminnow both strongly selected native cladocerans (Daphnia retrocurva) over P. forbesi, and moreover, northern pikeminnow selected native Cyclopidae spp. over P. forbesi. On the other hand, in two-prey experiments, chinook salmon, three-spined stickleback and mysids were non- selective with respect to feeding on native cyclopoid copepods versus P. forbesi. Our results indicate that all four native predators in the Columbia River Estuary can consume the invasive copepod, P. forbesi, but that some predators select for native zooplankton over P. forbesi, most likely due to one (or both) of two possible underlying casual mechanisms: 1) differential taxon-specific prey motility and escape responses (calanoids > cyclopoids > daphnids) or 2) the invasive status of the zooplankton prey resulting in naivety, and thus lower feeding rates, of native predators feeding on invasive prey.

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Mean and standard error of Pseudodiaptomus forbesi and native copepod prey consumed by four different predator types in single-prey experiments.Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray circles represent native copepods, Cyclopidae spp.
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pone.0144095.g001: Mean and standard error of Pseudodiaptomus forbesi and native copepod prey consumed by four different predator types in single-prey experiments.Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray circles represent native copepods, Cyclopidae spp.

Mentions: Two sample t- tests indicated no differences in the rates of consumption of native copepods vs. the invasive P. forbesi, suggesting that the predators did not consume prey types at different rates when offered only one kind of prey at a time (Fig 1; S3 and S4 Tables). However, the number of trials for each predator was modest (n = 5 per prey type) and all three wild-caught predator species trended toward higher feeding rates on native cyclopoid copepods (Fig 1 and S4 Table). When all four predators were analyzed in one model, there was still no evidence of feeding rate differences, nor any difference among predators (i.e. predator x prey interaction effects were non-significant). However when Chinook salmon were omitted and only the three wild-caught predators were considered, feeding rates were 7% higher on native cyclopoid copepods than on invasive P. forbesi (Effect of prey type: Fdf = 1,26 = 5.7, P = 0.02). While pikeminnows exhibited a higher overall feeding rate than other predators (Fdf = 2,26 = 25, P <0.0001), the lack of significant predator x prey interaction effects indicates similar decreases in feeding rates by all three wild predators on the invasive P. forbesi. In addition, there were no significant effects of predator length on total prey consumed or on prey-specific feeding rates, as expected given the relatively small differences in sizes between individual predators within a species (means + S.E.: chinook: 46.8 + 1.2mm; pikeminnow: 56.1 + 0.9 mm; stickleback: 40.8 + 0.9 mm; Neomysis: 14 + 0.5 mm) and our modest sample sizes.


Predation on the Invasive Copepod, Pseudodiaptomus forbesi, and Native Zooplankton in the Lower Columbia River: An Experimental Approach to Quantify Differences in Prey-Specific Feeding Rates.

Adams JB, Bollens SM, Bishop JG - PLoS ONE (2015)

Mean and standard error of Pseudodiaptomus forbesi and native copepod prey consumed by four different predator types in single-prey experiments.Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray circles represent native copepods, Cyclopidae spp.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664400&req=5

pone.0144095.g001: Mean and standard error of Pseudodiaptomus forbesi and native copepod prey consumed by four different predator types in single-prey experiments.Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray circles represent native copepods, Cyclopidae spp.
Mentions: Two sample t- tests indicated no differences in the rates of consumption of native copepods vs. the invasive P. forbesi, suggesting that the predators did not consume prey types at different rates when offered only one kind of prey at a time (Fig 1; S3 and S4 Tables). However, the number of trials for each predator was modest (n = 5 per prey type) and all three wild-caught predator species trended toward higher feeding rates on native cyclopoid copepods (Fig 1 and S4 Table). When all four predators were analyzed in one model, there was still no evidence of feeding rate differences, nor any difference among predators (i.e. predator x prey interaction effects were non-significant). However when Chinook salmon were omitted and only the three wild-caught predators were considered, feeding rates were 7% higher on native cyclopoid copepods than on invasive P. forbesi (Effect of prey type: Fdf = 1,26 = 5.7, P = 0.02). While pikeminnows exhibited a higher overall feeding rate than other predators (Fdf = 2,26 = 25, P <0.0001), the lack of significant predator x prey interaction effects indicates similar decreases in feeding rates by all three wild predators on the invasive P. forbesi. In addition, there were no significant effects of predator length on total prey consumed or on prey-specific feeding rates, as expected given the relatively small differences in sizes between individual predators within a species (means + S.E.: chinook: 46.8 + 1.2mm; pikeminnow: 56.1 + 0.9 mm; stickleback: 40.8 + 0.9 mm; Neomysis: 14 + 0.5 mm) and our modest sample sizes.

Bottom Line: In two-prey experiments, chinook salmon and northern pikeminnow both strongly selected native cladocerans (Daphnia retrocurva) over P. forbesi, and moreover, northern pikeminnow selected native Cyclopidae spp. over P. forbesi.On the other hand, in two-prey experiments, chinook salmon, three-spined stickleback and mysids were non- selective with respect to feeding on native cyclopoid copepods versus P. forbesi.Our results indicate that all four native predators in the Columbia River Estuary can consume the invasive copepod, P. forbesi, but that some predators select for native zooplankton over P. forbesi, most likely due to one (or both) of two possible underlying casual mechanisms: 1) differential taxon-specific prey motility and escape responses (calanoids > cyclopoids > daphnids) or 2) the invasive status of the zooplankton prey resulting in naivety, and thus lower feeding rates, of native predators feeding on invasive prey.

View Article: PubMed Central - PubMed

Affiliation: School of the Environment, Washington State University, Vancouver, Washington, United States of America.

ABSTRACT
Invasive planktonic crustaceans have become a prominent feature of aquatic communities worldwide, yet their effects on food webs are not well known. The Asian calanoid copepod, Pseudodiaptomus forbesi, introduced to the Columbia River Estuary approximately 15 years ago, now dominates the late-summer zooplankton community, but its use by native aquatic predators is unknown. We investigated whether three species of planktivorous fishes (chinook salmon, three-spined stickleback, and northern pikeminnow) and one species of mysid exhibited higher feeding rates on native copepods and cladocerans relative to P. forbesi by conducting `single-prey' feeding experiments and, additionally, examined selectivity for prey types with `two-prey' feeding experiments. In single-prey experiments individual predator species showed no difference in feeding rates on native cyclopoid copepods (Cyclopidae spp.) relative to invasive P. forbesi, though wild-collected predators exhibited higher feeding rates on cyclopoids when considered in aggregate. In two-prey experiments, chinook salmon and northern pikeminnow both strongly selected native cladocerans (Daphnia retrocurva) over P. forbesi, and moreover, northern pikeminnow selected native Cyclopidae spp. over P. forbesi. On the other hand, in two-prey experiments, chinook salmon, three-spined stickleback and mysids were non- selective with respect to feeding on native cyclopoid copepods versus P. forbesi. Our results indicate that all four native predators in the Columbia River Estuary can consume the invasive copepod, P. forbesi, but that some predators select for native zooplankton over P. forbesi, most likely due to one (or both) of two possible underlying casual mechanisms: 1) differential taxon-specific prey motility and escape responses (calanoids > cyclopoids > daphnids) or 2) the invasive status of the zooplankton prey resulting in naivety, and thus lower feeding rates, of native predators feeding on invasive prey.

Show MeSH
Related in: MedlinePlus