Contribution of toothfish depredated on fishing lines to the energy intake of killer whales off the Crozet Islands: a multi-scale bioenergetic approach

Faure, Johanna; Péron, Clara; Gasco, Nicolas; Massiot‐Granier, Félix; Spitz, Jérôme; Guinet, Christophe; Tixier, Paul

doi:10.3354/meps13725

Cited by 6 publications

(6 citation statements)

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“…This could occur by decreasing predation pressure on natural prey functional groups, in the short term, and by numerically enhancing predator populations, in the long-term [2]. Although the contribution of depredated toothfish to the annual food requirements of KW is limited [32], a facilitated access to this prey through depredation was shown to influence positively the reproductive output of females of the regular form [17]. However, this positive effect was minor, and unlikely to exceed the costs of depredation (e.g.…”

Section: Discussionmentioning

confidence: 99%

Increasing numbers of killer whale individuals use fisheries as feeding opportunities within subantarctic populations

et al. 2022

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Fisheries can generate feeding opportunities for large marine predators in the form of discards or accessible catch. How the use of this anthropogenic food may spread as a new behaviour, across individuals within populations over time, is poorly understood. This study used a 16-year (2003–2018) monitoring of two killer whale Orcinus orca subantarctic populations ( regular and Type-D at Crozet), and Bayesian multistate capture–mark–recapture models, to assess temporal changes in the number of individuals feeding on fish caught on hooks (‘depredation’ behaviour) of a fishery started in 1996. For both populations, the number of depredating individuals increased during the study period (34 to 94 for regular ; 17 to 43 for Type-D ). Increasing abundance is unlikely to account for this and, rather, the results suggest depredation was acquired by increasing numbers of existing individuals. For regular killer whales, a plateau reached from 2014 suggests that it took 18 years for the behaviour to spread across the whole population. A more recent plateau was apparent for Type-D s but additional years are needed to confirm this. These findings show how changes in prey availability caused by human activities lead to rapid, yet progressive, innovations in killer whales, likely altering the ecological role of this top-predator.

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Section: Discussionmentioning

confidence: 99%

Increasing numbers of killer whale individuals use fisheries as feeding opportunities within subantarctic populations

et al. 2022

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“…Similar evaluations of populations’ overall energy requirements and prey consumption have continued over the years ( Banas et al, 2021 ; Bejarano et al, 2017 ; Benoit-Bird, 2004 ; Costa et al, 1989 ; Fortune et al, 2013 ; Gallagher et al, 2018 ; Guilpin et al, 2019 ; Kriete, 1995 ; Lockyer, 2007 ; Malavear, 2002 ; McHuron et al, 2017b ; Noren, 2011 ; Noren et al, 2012 , 2014 ; Rechsteiner et al, 2013 ; Reisinger et al, 2011 ; Williams et al, 2004 ; Winship et al, 2002 ). Often, accounting models have been developed with the applied management goal of quantifying the levels of predation on prey stocks and potential competition with local fisheries ( Acevedo and Urbán, 2021 ; Boyd, 2002 ; Cornick et al, 2006 ; Faure et al, 2021 ; Forcada et al, 2009 ; Markussen et al, 1992 ; McHuron et al, 2020 ; Mohn and Bowen, 1996 ; Nilssen et al, 2014 ; Olesiuk, 1993 ; Queiros et al, 2018 ; Trzcinski et al, 2006 ; Weise and Harvey, 2008 ).…”

Section: Bioenergetic Accounting Models Of Population Energy Requirem...mentioning

confidence: 99%

A review of bioenergetic modelling for marine mammal populations

Pirotta

2022

Conservation Physiology

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Bioenergetic models describe the processes through which animals acquire energy from resources in the environment and allocate it to different life history functions. They capture some of the fundamental mechanisms regulating individuals, populations and ecosystems and have thus been used in a wide variety of theoretical and applied contexts. Here, I review the development of bioenergetic models for marine mammals and their application to management and conservation. For these long-lived, wide-ranging species, bioenergetic approaches were initially used to assess the energy requirements and prey consumption of individuals and populations. Increasingly, models are developed to describe the dynamics of energy intake and allocation and predict how resulting body reserves, vital rates and population dynamics might change as external conditions vary. The building blocks required to develop such models include estimates of intake rate, maintenance costs, growth patterns, energy storage and the dynamics of gestation and lactation, as well as rules for prioritizing allocation. I describe how these components have been parameterized for marine mammals and highlight critical research gaps. Large variation exists among available analytical approaches, reflecting the large range of life histories, management needs and data availability across studies. Flexibility in modelling strategy has supported tailored applications to specific case studies but has resulted in limited generality. Despite the many empirical and theoretical uncertainties that remain, bioenergetic models can be used to predict individual and population responses to environmental change and other anthropogenic impacts, thus providing powerful tools to inform effective management and conservation.

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“…Crozet were shown to contribute 8.8% of the annual energetic requirements of the whole killer whale population (Faure et al, 2021;Tixier et al, 2020), but from our findings, this contribution is likely to greatly vary across social units. In particular, this contribution and its subsequent demographic and ecological effects are likely maximum for the 4 social units out of 17 that we found involved in more than 70% of the depredation events.…”

Section: Our Findings Have Implications For Both the Conservation Ofmentioning

confidence: 58%

Behavioural heterogeneity across killer whale social units in their response to feeding opportunities from fisheries

Auguin,

Guinet,

Mourier

et al. 2024

Ecology and Evolution

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Intra‐population heterogeneity in the behavioural response of predators to changes in prey availability caused by human activities can have major evolutionary implications. Among these activities, fisheries, while extracting resources, also provide new feeding opportunities for marine top predators. However, heterogeneity in the extent to which individuals have responded to these opportunities within populations is poorly understood. Here, we used 18 years of photo‐identification data paired with statistical models to assess variation in the way killer whale social units within a subantarctic population (Crozet Islands) interact with fisheries to feed on fish caught on fishing gear (i.e., depredation behaviour). Our results indicate large heterogeneity in both the spatial and temporal extents of depredation across social units. While some frequently depredated on fishery catches over large areas, others sporadically did so and in small areas consistently over the years. These findings suggest that killer whale social units are exposed to varying levels of impacts of depredation, both negative (potential retaliation from fishers) and positive (food provisioning), on their life history traits, and may explain the contrasted demographic patterns observed within the declining population at Crozet but also potentially within the many other killer whale populations documented depredating on fisheries catches worldwide.

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Contribution of toothfish depredated on fishing lines to the energy intake of killer whales off the Crozet Islands: a multi-scale bioenergetic approach

Cited by 6 publications

References 53 publications

Increasing numbers of killer whale individuals use fisheries as feeding opportunities within subantarctic populations

Increasing numbers of killer whale individuals use fisheries as feeding opportunities within subantarctic populations

A review of bioenergetic modelling for marine mammal populations

Behavioural heterogeneity across killer whale social units in their response to feeding opportunities from fisheries

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