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Inter-cohort cannibalism of early benthic phase blue king crabs (Paralithodes platypus): alternate foraging strategies in different habitats lead to different functional responses.

Daly B, Long WC - PLoS ONE (2014)

Bottom Line: Predator foraging activity was reduced in shell and may be an adaptive behavior to balance foraging efficiency and susceptibility to larger predators.The distribution and abundance of such habitat may be important for recruitment success in some populations.Future studies should compare benthic habitat and species assemblages in areas with variable abundances, such as the Pribilof Islands and Saint Matthew Island in the eastern Bering Sea, to better understand possible mechanisms for recruitment variability.

View Article: PubMed Central - PubMed

Affiliation: Kodiak Laboratory, Resource Assessment and Conservation Engineering Division, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Kodiak, Alaska, United States of America.

ABSTRACT
Blue king crabs (Paralithodes platypus) are commercially and ecologically important in Alaska, USA, but population abundances have fluctuated over the past several decades likely resulting from a combination of environmental and biological factors, including recruitment variability. Cannibalism between cohorts may be a source of mortality limiting recruitment success in the wild, but the degree of inter-cohort cannibalism is unknown for early benthic phase blue king crabs. In laboratory experiments, we evaluated the effects of habitat type (sand and shell) on the predator functional response and foraging behavior of year-1 blue king crabs as predators of year-0 conspecifics and examined the effects of predator presence on crypsis of prey crabs. In sand, consumption rates increased with predator size and prey density until satiation, while predation rates in shell were low regardless of predator size or prey density. These differential predation rates yielded a type III functional response in sand but a type I functional response in shell habitat. Crypsis of prey crabs was generally high and did not change in the presence of predators. Predator foraging activity was reduced in shell and may be an adaptive behavior to balance foraging efficiency and susceptibility to larger predators. Our results demonstrate that early benthic phase blue king crabs are cannibalistic between cohorts in the laboratory and that shell material is extremely effective for reducing encounter rates with conspecific predators. The distribution and abundance of such habitat may be important for recruitment success in some populations. Future studies should compare benthic habitat and species assemblages in areas with variable abundances, such as the Pribilof Islands and Saint Matthew Island in the eastern Bering Sea, to better understand possible mechanisms for recruitment variability.

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Related in: MedlinePlus

Functional response of year-1 blue king crabs (P. platypus) to year-0 blue king crabs density in sand (closed circles) and shell (open circles) habitat: (A) proportional predation and (B) number of prey crabs eaten.Points are the average (± SE) at each density and are offset slightly. Lines represent the best fit functional response model for each habitat. Parameter estimates (± SE) for sand are: b = 0.039 (0.023), c = −0.068 (0.19), Th = 0.84 (0.19), and for shell are: r = 0.016 (0.003).
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pone-0088694-g001: Functional response of year-1 blue king crabs (P. platypus) to year-0 blue king crabs density in sand (closed circles) and shell (open circles) habitat: (A) proportional predation and (B) number of prey crabs eaten.Points are the average (± SE) at each density and are offset slightly. Lines represent the best fit functional response model for each habitat. Parameter estimates (± SE) for sand are: b = 0.039 (0.023), c = −0.068 (0.19), Th = 0.84 (0.19), and for shell are: r = 0.016 (0.003).

Mentions: In control trials, overall prey crab recovery was 100% indicating cannibalism within the year-0 cohort did not occur. In sand, the type III functional response model was best supported by our data (Fig. 1A, Table 1). Predator crabs appeared to reach satiation at approximately seven prey crabs (Fig. 1B). In shell, the data were unable to differentiate among the functional response models (Table 1), likely because of low predation rates at all prey densities (Fig. 1B). Because the type I functional response had the lowest AICc and is the most parsimonious model, we present and draw inferences from that model.


Inter-cohort cannibalism of early benthic phase blue king crabs (Paralithodes platypus): alternate foraging strategies in different habitats lead to different functional responses.

Daly B, Long WC - PLoS ONE (2014)

Functional response of year-1 blue king crabs (P. platypus) to year-0 blue king crabs density in sand (closed circles) and shell (open circles) habitat: (A) proportional predation and (B) number of prey crabs eaten.Points are the average (± SE) at each density and are offset slightly. Lines represent the best fit functional response model for each habitat. Parameter estimates (± SE) for sand are: b = 0.039 (0.023), c = −0.068 (0.19), Th = 0.84 (0.19), and for shell are: r = 0.016 (0.003).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3928282&req=5

pone-0088694-g001: Functional response of year-1 blue king crabs (P. platypus) to year-0 blue king crabs density in sand (closed circles) and shell (open circles) habitat: (A) proportional predation and (B) number of prey crabs eaten.Points are the average (± SE) at each density and are offset slightly. Lines represent the best fit functional response model for each habitat. Parameter estimates (± SE) for sand are: b = 0.039 (0.023), c = −0.068 (0.19), Th = 0.84 (0.19), and for shell are: r = 0.016 (0.003).
Mentions: In control trials, overall prey crab recovery was 100% indicating cannibalism within the year-0 cohort did not occur. In sand, the type III functional response model was best supported by our data (Fig. 1A, Table 1). Predator crabs appeared to reach satiation at approximately seven prey crabs (Fig. 1B). In shell, the data were unable to differentiate among the functional response models (Table 1), likely because of low predation rates at all prey densities (Fig. 1B). Because the type I functional response had the lowest AICc and is the most parsimonious model, we present and draw inferences from that model.

Bottom Line: Predator foraging activity was reduced in shell and may be an adaptive behavior to balance foraging efficiency and susceptibility to larger predators.The distribution and abundance of such habitat may be important for recruitment success in some populations.Future studies should compare benthic habitat and species assemblages in areas with variable abundances, such as the Pribilof Islands and Saint Matthew Island in the eastern Bering Sea, to better understand possible mechanisms for recruitment variability.

View Article: PubMed Central - PubMed

Affiliation: Kodiak Laboratory, Resource Assessment and Conservation Engineering Division, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Kodiak, Alaska, United States of America.

ABSTRACT
Blue king crabs (Paralithodes platypus) are commercially and ecologically important in Alaska, USA, but population abundances have fluctuated over the past several decades likely resulting from a combination of environmental and biological factors, including recruitment variability. Cannibalism between cohorts may be a source of mortality limiting recruitment success in the wild, but the degree of inter-cohort cannibalism is unknown for early benthic phase blue king crabs. In laboratory experiments, we evaluated the effects of habitat type (sand and shell) on the predator functional response and foraging behavior of year-1 blue king crabs as predators of year-0 conspecifics and examined the effects of predator presence on crypsis of prey crabs. In sand, consumption rates increased with predator size and prey density until satiation, while predation rates in shell were low regardless of predator size or prey density. These differential predation rates yielded a type III functional response in sand but a type I functional response in shell habitat. Crypsis of prey crabs was generally high and did not change in the presence of predators. Predator foraging activity was reduced in shell and may be an adaptive behavior to balance foraging efficiency and susceptibility to larger predators. Our results demonstrate that early benthic phase blue king crabs are cannibalistic between cohorts in the laboratory and that shell material is extremely effective for reducing encounter rates with conspecific predators. The distribution and abundance of such habitat may be important for recruitment success in some populations. Future studies should compare benthic habitat and species assemblages in areas with variable abundances, such as the Pribilof Islands and Saint Matthew Island in the eastern Bering Sea, to better understand possible mechanisms for recruitment variability.

Show MeSH
Related in: MedlinePlus