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Article: Ecological considerations for species distribution modelling of euphausiids in the Northeast Pacific Ocean

Evans, Rhian / Gauthier, Stéphane / Robinson, Clifford L.K.

Canadian journal of fisheries and aquatic sciences. 2022, v. 79, no. 3

2022

Abstract: Euphausiids are a keystone species in marine food webs of the Northeast Pacific Ocean, important for forage fish, commercial fish species and marine predators such as seabirds and whales. Ecosystem-based fisheries management relies on realistic lower- ... ...

Abstract	Euphausiids are a keystone species in marine food webs of the Northeast Pacific Ocean, important for forage fish, commercial fish species and marine predators such as seabirds and whales. Ecosystem-based fisheries management relies on realistic lower-trophic-level information for forecasting under future changing climate scenarios. We synthesised information from quantitative modelling studies analysing the relationship between euphausiids and their environment for two species of euphausiids that dominate assemblages in this region — Euphausia pacifica and Thysanoessa spinifera. Studies analysed suggest that variables reflecting the physical and biological environment in situ, features reflecting the geomorphic marine landscape, and large-scale climate indices all significantly affect euphausiid biomass and distribution. Temperature was the most tested predictor variable in the euphausiid models reviewed; however, it was significant in fewer models than other variables tested. We review and compare model structures, predictor variable selection and temporal lag phases to develop recommendations for species distribution modelling of euphausiids in the Northeast Pacific Ocean. We believe the results from this review will be applicable globally across regions with similar climates where euphausiids are numerous and can be adapted for different species and environments.
Keywords	Euphausia ; biomass ; climate ; forage fish ; geographical distribution ; keystone species ; landscapes ; temperature ; Pacific Ocean
Language	English
Size	p. 518-532.
Publishing place	Canadian Science Publishing
Document type	Article
ZDB-ID	1473089-3
ISSN	1205-7533 ; 0706-652X
ISSN (online)	1205-7533
ISSN	0706-652X
DOI	10.1139/cjfas-2020-0481
Database	NAL-Catalogue (AGRICOLA)

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Article: Southern resident killer whales encounter higher prey densities than northern resident killer whales during summer

Sato, Mei / Trites, Andrew W. / Gauthier, Stéphane

Canadian journal of fisheries and aquatic sciences. 2021, v. 78, no. 11

2021

Abstract: The decline of southern resident killer whales (Orcinus orca) may be due to a shortage of prey, but there is little data to test this hypothesis. We compared the availability of prey (Chinook salmon, Oncorhynchus tshawytscha) sought by southern residents ...

Abstract	The decline of southern resident killer whales (Orcinus orca) may be due to a shortage of prey, but there is little data to test this hypothesis. We compared the availability of prey (Chinook salmon, Oncorhynchus tshawytscha) sought by southern residents in Juan de Fuca Strait during summer with the abundance and distribution of Chinook available to the much larger and growing population of northern resident killer whales feeding in Johnstone Strait. We used ship-based multifrequency echosounders to identify differences in prey fields that may explain the dynamics of these two killer whale populations. Contrary to expectations, we found that both killer whale habitats had patchy distributions of prey that did not differ in their frequencies of occurrence, nor in the size compositions of individual fish. However, the density of fish within each patch was 4–6 times higher in the southern resident killer whale habitat. These findings do not support the hypothesis that southern resident killer whales are experiencing a prey shortage in the Salish Sea during summer and suggest a combination of other factors is affecting overall foraging success.
Keywords	Oncorhynchus tshawytscha ; Orcinus orca ; fish ; habitats ; summer
Language	English
Size	p. 1732-1743.
Publishing place	NRC Research Press
Document type	Article
ZDB-ID	1473089-3
ISSN	1205-7533 ; 0706-652X
ISSN (online)	1205-7533
ISSN	0706-652X
DOI	10.1139/cjfas-2020-0445
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Integrating technologies provides insight into the subsurface foraging behaviour of a humpback whale (Megaptera novaeangliae) feeding on walleye pollock (Gadus chalcogrammus) in Juan de Fuca Strait, Canada.

Reidy, Rhonda / Gauthier, Stéphane / Doniol-Valcroze, Thomas / Lemay, Matthew A / Clemente-Carvalho, Rute B G / Cowen, Laura L E / Juanes, Francis

PloS one

2023 Volume 18, Issue 3, Page(s) e0282651

Abstract: Subsurface foraging is an important proportion of the activity budget of rorqual whales, yet information on their behaviour underwater remains challenging to obtain. Rorquals are assumed to feed throughout the water column and to select prey as a ... ...

Abstract	Subsurface foraging is an important proportion of the activity budget of rorqual whales, yet information on their behaviour underwater remains challenging to obtain. Rorquals are assumed to feed throughout the water column and to select prey as a function of depth, availability and density, but there remain limitations in the precise identification of targeted prey. Current data on rorqual foraging in western Canadian waters have thus been limited to observations of prey species amenable to surface feeding, such as euphausiids and Pacific herring (Clupea pallasii), with no information on deeper alternative prey sources. We measured the foraging behaviour of a humpback whale (Megaptera novaeangliae) in Juan de Fuca Strait, British Columbia, using three complimentary methods: whale-borne tag data, acoustic prey mapping, and fecal sub-sampling. Acoustically detected prey layers were near the seafloor and consistent with dense schools of walleye pollock (Gadus chalcogrammus) distributed above more diffuse aggregations of pollock. Analysis of a fecal sample from the tagged whale confirmed that it had been feeding on pollock. Integrating the dive profile with the prey data revealed that the whale's foraging effort followed the general pattern of areal prey density, wherein the whale had a higher lunge-feeding rate at the highest prey abundance and stopped feeding when prey became limited. Our findings of a humpback whale feeding on seasonally energy-dense fish like walleye pollock, which are potentially abundant in British Columbia, suggests that pollock may be an important prey source for this rapidly growing whale population. This result is informative when assessing regional fishing activities for semi-pelagic species as well as the whales' vulnerability to fishing gear entanglements and feeding disturbances during a narrow window of prey acquisition.
MeSH term(s)	Animals ; Humpback Whale ; Gadiformes ; British Columbia ; Cetacea ; Acoustics
Language	English
Publishing date	2023-03-06
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2267670-3
ISSN	1932-6203 ; 1932-6203
ISSN (online)	1932-6203
ISSN	1932-6203
DOI	10.1371/journal.pone.0282651
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article: Optimal rationing within a heterogeneous population

Choné, Philippe / Gauthier, Stéphane

Journal of public economic theory Vol. 19, No. 3 , p. 732-738

2017 Volume 19, Issue 3, Page(s) 732–738

Author's details	Philippe Choné, Stéphane Gauthier
Keywords	Öffentliche Dienstleistung ; Aufsichtsbehörde ; Rationierung ; Theorie
Language	English
Publisher	Wiley-Blackwell
Publishing place	Malden, Mass
Document type	Article
ZDB-ID	1468434-2 ; 1478348-4
ISSN	1467-9779 ; 1097-3923
ISSN (online)	1467-9779
ISSN	1097-3923
Database	ECONomics Information System

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Article: Redistribution by means of lotteries

Gauthier, Stéphane / Laroque, Guy

Journal of economic theory Vol. 169 , p. 707-716

2017 Volume 169, Page(s) 707–716

Author's details	Stéphane Gauthier, Guy Laroque
Keywords	Lerner egalitarianism ; Random redistribution ; Incentives
Language	English
Publisher	Elsevier
Publishing place	Amsterdam
Document type	Article
ZDB-ID	410539-4 ; 1469177-2
ISSN	0022-0531
ISSN	0022-0531
Database	ECONomics Information System

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Article: Optimal tax base with administrative fixed costs

Gauthier, Stéphane

International tax and public finance Vol. 20, No. 6 , p. 961-973

2013 Volume 20, Issue 6, Page(s) 961–973

Author's details	Stéphane Gauthier
Keywords	Indirect taxation ; VAT ; Tax base ; Administrative costs
Language	English
Size	graph. Darst.
Publisher	Springer
Publishing place	New York
Document type	Article
ZDB-ID	1207421-4 ; 2016247-9
ISSN	1573-6970 ; 0927-5940
ISSN (online)	1573-6970
ISSN	0927-5940
Database	ECONomics Information System

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Article ; Online: The influence of temperature on Pacific hake co‐occurrence with euphausiids in the California Current Ecosystem

Phillips, Elizabeth Mary / Malick, Michael J. / Gauthier, Stéphane / Haltuch, Melissa A. / Hunsicker, Mary E. / Parker‐Stetter, Sandra L. / Thomas, Rebecca E.

Fisheries Oceanography. 2023 May, v. 32, no. 3 p.267-279

2023

Abstract: Understanding the influence of ocean conditions on predator–prey relationships can provide insight for ecosystem‐based fisheries management. Pacific hake (Merluccius productus) are abundant and commercially important groundfish in the California Current ... ...

Abstract	Understanding the influence of ocean conditions on predator–prey relationships can provide insight for ecosystem‐based fisheries management. Pacific hake (Merluccius productus) are abundant and commercially important groundfish in the California Current Ecosystem (CCE) that consume euphausiids (krill) as a major prey item. We used data from the biennial joint U.S.‐Canada Integrated Ecosystem & Acoustic Trawl Survey for Pacific hake (2007–2019, n = 8 surveys) to quantify co‐occurrence of age 2+ hake with krill in relation to bottom depth, continental shelf break location, surface chlorophyll‐a, and 100‐m temperature. Vertical distributions of hake varied among years and were not correlated to krill depth. Hake hotspots occurred primarily off the Oregon coast and near Cape Mendocino, while most krill hotspots occurred in the northern CCE. The probability of co‐occurrence was greatest during cool ocean conditions (100‐m temperature 1°C below average), averaging 41.0% and extending throughout most of the CCE. During warm ocean conditions (100‐m temperature 1°C above average), predicted co‐occurrence averaged 17.0% and was concentrated near Cape Mendocino. These results indicate that hake‐krill co‐occurrence is a function of predator and prey spatial distributions and overall krill abundance. Furthermore, temperature influences hake‐krill co‐occurrence and may explain some of the variation in hake growth and recruitment to the fishery.
Keywords	Euphausiacea ; Merluccius productus ; Oregon ; acoustics ; chlorophyll ; coasts ; continental shelf ; demersal fish ; ecosystems ; fisheries ; hake ; krill ; oceanography ; probability ; surveys ; temperature ; Pacific Ocean
Language	English
Dates of publication	2023-05
Size	p. 267-279.
Publishing place	John Wiley & Sons, Ltd
Document type	Article ; Online
Note	JOURNAL ARTICLE
ZDB-ID	1214985-8
ISSN	1054-6006 ; 1361-9470
ISSN	1054-6006 ; 1361-9470
DOI	10.1111/fog.12628
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Factors affecting the seasonal distribution and biomass of E. pacifica and T. spinifera along the Pacific coast of Canada: A spatiotemporal modelling approach.

Evans, Rhian / English, Philina A / Anderson, Sean C / Gauthier, Stéphane / Robinson, Clifford L K

PloS one

2021 Volume 16, Issue 5, Page(s) e0249818

Abstract: Euphausiids are a keystone species in coastal food webs due to their high lipid content and seasonally high biomass. Understanding the habitat and environmental drivers that lead to areas of high biomass, or 'hotspots', and their seasonal persistence, ... ...

Abstract	Euphausiids are a keystone species in coastal food webs due to their high lipid content and seasonally high biomass. Understanding the habitat and environmental drivers that lead to areas of high biomass, or 'hotspots', and their seasonal persistence, will support the identification of important foraging regions for mid- and upper- trophic level predators. We quantify the distribution of hotspots of the two dominant species of euphausiid in the north-east Pacific Ocean: Euphausia pacifica and Thysanoessa spinifera, as well as euphausiid larvae (mixed species). The Canadian coast encompasses the northern California Current Ecosystem and the transition zone to the Alaska current, and is a highly productive region for fisheries, marine mammals, and seabirds. We used spatiotemporal modelling to predict the distribution of these three euphausiid groups in relation to geomorphic and environmental variables during the important spring-summer months (April through September) when euphausiid biomass is highest. We quantified the area, intensity, and persistence of biomass hotspots across months according to specific oceanographic ecosections developed for marine spatial planning purposes. Persistent hotspots of both adult species were predicted to occur along the 200 m depth contour of the continental slope; however, differences were predicted on the shallower Dixon shelf, which was a key area for T. spinifera, and within the Juan de Fuca Eddy system where E. pacifica hotspots occurred. The continental slope along the west coast of Vancouver Island was the only persistent hotspot region common between both adult species and euphausiid larvae. Larval distribution was more correlated with T. spinifera than E. pacifica biomass. Hotspots of adults were more persistent across months than hotspots of euphausiid larvae, which were seasonally patchy. The persistence of biomass hotspots of forage species through periods of low overall biomass could maintain trophic connectivity through perturbation events and increase ecosystem resilience to climate change.
MeSH term(s)	Animals ; Biomass ; Canada ; Climate Change ; Ecosystem ; Euphausiacea/growth & development
Language	English
Publishing date	2021-05-14
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2267670-3
ISSN	1932-6203 ; 1932-6203
ISSN (online)	1932-6203
ISSN	1932-6203
DOI	10.1371/journal.pone.0249818
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: A multi-frequency acoustic method to estimate mean standard length of juvenile salmon in the Discovery Islands, British Columbia

Rousseau, S. / Gauthier, Stéphane / Neville, C. M. / Johnson, Stewart / Trudel, Marc

Fisheries research. 2020 July, v. 227 p.105536-

2020

Abstract: A method to estimate the mean standard length (L¯) of juvenile salmon in aggregations using multi-frequency (67 and 125 kHz) acoustic analysis was developed. An autonomous, single beam echosounder (Acoustic Zooplankton and Fish Profiler (AZFP), ASL ... ...

Abstract	A method to estimate the mean standard length (L¯) of juvenile salmon in aggregations using multi-frequency (67 and 125 kHz) acoustic analysis was developed. An autonomous, single beam echosounder (Acoustic Zooplankton and Fish Profiler (AZFP), ASL Environmental Sciences) was deployed on the seafloor in Okisollo Channel, British Columbia during peak juvenile salmon migration season in 2015 and 2016. A positive correlation was found between the difference in the mean volume backscattering strength at 67 and 125 kHz (ΔMVBS₆₇₋₁₂₅ₖHz) of juvenile salmon aggregations and the mean standard length of juvenile salmon collected with a purse seiner. A relationship of the form ΔMVBS67-125kHz=Alog10L¯+B was established. High variability was observed due to differences in salmon species composition and lower sampling sizes at the tail end of the migration periods, but a consistent relationship with comparable parameters was found. We suggest that this method is valuable particularly in the case of long-term monitoring of species that are known to aggregate in schools of individuals with similar size, as it can be used to estimate mean size without the use of invasive capture techniques.
Keywords	acoustic properties ; islands ; juveniles ; monitoring ; salmon ; sample size ; schools of fish ; species diversity ; British Columbia ; Acoustics ; Salmon ; Multifrequency ; Size ; Monitoring
Language	English
Dates of publication	2020-07
Publishing place	Elsevier B.V.
Document type	Article ; Online
ZDB-ID	406532-3
ISSN	0165-7836
ISSN	0165-7836
DOI	10.1016/j.fishres.2020.105536
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Small departures from rationality magnify fluctuations

Gauthier, Stéphane

Economics bulletin : EB

2004

Author's details	Stéphane Gauthier
Keywords	Sunspots ; Erwartungsbildung ; Konjunkturtheorie
Language	English
Size	Online-Ressource
Publisher	Univ. of Illinois
Publishing place	Champaign-Urbana, Ill
Document type	Article ; Online
Note	IMD-Felder maschinell generiert
ZDB-ID	2041623-4
ISSN	1545-2921
Database	ECONomics Information System

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