Mixed-Species Associations of Marine Mammals in the Southern California Bight, with Emphasis on Risso’s Dolphins (Grampus griseus)

Bacon, Cathy E.; Smultea, Mari A.; Fertl, Dagmar; Würsig, Bernd; Burgess, Elizabeth A.; Hawks-Johnson, Stefanie

doi:10.1578/am.43.2.2017.177

Cited by 12 publications

(5 citation statements)

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“…The species also interact in the ocean, including relatively common observations of mixed‐species associations between common bottlenose dolphins and short‐finned pilot whales off Japan (Kanaji & Miyashita, 2021; Kasuya & Marsh, 1984), and sporadic formation of mixed‐species groups between common bottlenose dolphins and Risso's dolphins observed during sighting survey cruises (Kanaji & Miyashita, 2021). Similar mixed‐species associations between these three species have been reported outside of our study area (Bacon et al., 2017; Shane, 1995). Exploiting the same prey is one plausible reason for the formation of mixed‐species associations, although there might also be other reasons such as predator avoidance and social or reproductive advantages (Stensland et al., 2003).…”

Section: Discussionsupporting

confidence: 89%

Multiple‐model stock assessment frameworks for precautionary management and conservation on fishery‐targeted coastal dolphin populations off Japan

Kanaji

Maeda

Okamura

et al. 2021

Journal of Applied Ecology

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1. Stock assessment approaches are often oversimplified due to lack of biological knowledge and insufficient data. In spite of world-wide attention, fishery-targeted coastal dolphin species in Japan have lacked in-depth quantitative stock assessments because of limited time series of population size and an absence of associated biological information. We consequently developed integrated population models that analysed multiple sources of data simultaneously with published biological information within a Bayesian framework. 2. We estimate population status and trends for three main species targeted by fisheries, bottlenose dolphins Tursiops truncatus, Risso's dolphins Grampus griseu, and short-finned pilot whales Globicephala macrorhynchus, using single-species ageaggregated and age-structured population dynamics models. Models were fit to absolute abundance estimates from systematic line-transect surveys, four series of abundance indices calculated from fisher's logbooks, and historical catch records. Published biological information was used to develop prior distributions for the biological parameters. We assessed the possible effects of ecological disturbance and competition using state-space and multispecies models.3. The multispecies model was selected by the model selection both for the ageaggregated and the age-structured approaches.4. Single-species assessments found that population size declined 4.2% (Risso's dolphin) to 8.0% (bottlenose dolphin) for three species since the late 1800s based on median posterior values, while the state-space and multispecies models found that environmental disturbance and an interaction among species could have reduced population size more substantially.5. Policy implications. Simple single-species models are often used to provide conservation and management advice for wild animals but, in this case, results from such models are overly optimistic because they overlook important ecological process. In contrast, current population status could be less favorable if environmental disturbance and interspecific competition actually control population dynamics. Even if that is not the case, considering ecological process in the model will provide more precautionary ways. Our approach of combining multiple modelling frameworks is

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Section: Discussionsupporting

confidence: 89%

Multiple‐model stock assessment frameworks for precautionary management and conservation on fishery‐targeted coastal dolphin populations off Japan

Kanaji

Maeda

Okamura

et al. 2021

Journal of Applied Ecology

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“…Mixed‐species groups of the delphinid family have been observed in several species in the world (Bearzi, 2005). Foraging advantage, predator avoidance, and social advantage have been recognized as functional explanations for mixed‐species groups among mammals (Stensland et al, 2003), while many researchers have reported that mixed‐species groups of delphinid were formed mainly in relation to dietary overlap (Bacon et al, 2017; Clua & Grosvalet, 2001; Kraus & Gihr, 1971; Quérouil et al, 2008; Shane, 1995). Thus, it is widely considered that the occurrence of mixed‐species groups is a proxy for existing habitat overlap because it is direct evidence that distinct species groups temporally use the same microhabitat in which individuals or schools can directly interact each other.…”

Section: Habitat Group Speciesmentioning

confidence: 99%

Habitat use and habitat overlap of Delphinidae species revealed by mixed‐species group occurrence in the North Pacific Ocean

Kanaji

Miyashita

2021

Marine Mammal Science

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Interspecific competition, environmental disturbance, and predation are important factors controlling the population dynamics of animals (Hollowed et al., 2000;Link, 2002). Spatiotemporal changes and dietary overlaps in species' habitats have been recognized to potentially cause interspecific competition (Carothers & Jaksi c, 1984). In this regard, our study group has investigated macroscale spatial overlaps among delphinid species using multivariate analysis (Kanaji et al., 2016), habitat modeling (Kanaji, Okazaki, & Miyashita, 2017), and stable-isotopic approaches (Kanaji, Yoshida, & Okazaki, 2017) in the North Pacific Ocean. In this ocean, 15 delphinid species were classified into habitat groups in relation to oceanographic environment (Table 1; Kanaji, Okazaki, & Miyashita, 2017;Kanaji et al., 2016).However, these macroscale spatial overlaps revealed that ocean-wide scale analyses do not necessarily prove the existence of interspecific competition. For example, a certain degree of niche partitioning could occur to avoid direct competition, even within the same habitat group (Kanaji, Yoshida, & Okazaki, 2017). Therefore, more direct biological evidence is required to provide detailed insights into interspecific competition and habitat use among delphinid species.Mixed-species groups of the delphinid family have been observed in several species in the world (Bearzi, 2005).Foraging advantage, predator avoidance, and social advantage have been recognized as functional explanations for mixed-species groups among mammals (Stensland et al., 2003), while many researchers have reported that mixedspecies groups of delphinid were formed mainly in relation to dietary overlap (

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“…gas or vapor bubbles, immiscible liquid droplets, or solid particles) are important, may serve as a useful model for heterospecific organismal aggregations. Though most animal groups comprise a single species, some animals including birds [71], ungulates [72,73], fish [74], primates [75], and cetaceans [76] form heterospecific aggregations. Benefits of heterospecific aggregations are thought to include enhanced detection of food and predators [75].…”

Section: Multiphase Flowmentioning

confidence: 99%

Organismal aggregations exhibit fluidic behaviors: a review

2019

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Groups of organisms such as flocks, swarms, herds, and schools form for a variety of motivations linked to survival and proliferation. Their size, locomotive domain, population, and the environmental stimuli guiding motion make challenging the study of member interactions and global behaviors. In this review, we borrow principles and analogies from fluids to describe the characteristics of organismal aggregations, which may inspire new tools for the analysis of collective motion. Examples of fluid resemblance include open channel flow, droplet formation, and particleladen flow. We show how the properties of density, viscosity, and surface tension have strong parallels in the structure and behavior of aggregations of contrasting scale and domain. In certain cases, aggregations are sufficiently fluid-like that values can be assigned to such properties. We highlight how organisms engaging in collective motion can flow, roll, and change phase. Finally, we present limitations and exceptions for the application of fluidic principles to the motion of living groups.

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Mixed-Species Associations of Marine Mammals in the Southern California Bight, with Emphasis on Risso’s Dolphins (Grampus griseus)

Cited by 12 publications

References 0 publications

Multiple‐model stock assessment frameworks for precautionary management and conservation on fishery‐targeted coastal dolphin populations off Japan

Multiple‐model stock assessment frameworks for precautionary management and conservation on fishery‐targeted coastal dolphin populations off Japan

Habitat use and habitat overlap of Delphinidae species revealed by mixed‐species group occurrence in the North Pacific Ocean

Organismal aggregations exhibit fluidic behaviors: a review

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