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Garry B. Stenson - One of the best experts on this subject based on the ideXlab platform.
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Quantifying Some of the Major Sources of Uncertainty Associated with Estimates of Harp Seal Prey Consumption Part I: Uncertainty in the Estimates of Harp Seal
2015Co-Authors: Population Size, William G. Warren, Peter A. Shelton, Garry B. StensonAbstract:An effort is made to quantify some of the major sources of uncertainty associated with estimates of Harp Seal (Phoca groenlandica) prey consumption, with special refer-ence to the uncertainty in estimates of Seal population size. A population dynamics model is used, the inputs for which are the annual catches at age and pregnancy rates. Two pa-rameters, instantaneous mortality rate, and the hunting selection on the pups for years prior to the availability of pregnancy data, are estimated by non-linear least squares using available survey estimates of pup production. The uncertainty in estimates of population size is estimated by Monte Carlo methods from the estimates of sampling error in the pregnancy rates and in the survey estimates of pup production, with the catches at age assumed to be known. The uncertainty in the population estimates is dominated by the uncertainty in the survey estimates. Key words: catch rates, Harp Seal, mortality, pregnancy rates, stock siz
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comment on towards a precautionary approach to managing canada s commercial Harp Seal hunt by leaper et al
Ices Journal of Marine Science, 2010Co-Authors: Mike O Hammill, Garry B. StensonAbstract:Hammill, M. O., and Stenson, G. B. 2010. Comment on “Towards a precautionary approach to managing Canada's commercial Harp Seal hunt” by Leaper et al. - ICES Journal of Marine Science, 67: 321-322.The Objective-Based Fisheries Management used by Canada to manage the Northwest Atlantic Seal hunt conforms to United Nations and Canadian Government precautionary approach frameworks in its structure and industry involvement. Managers and industry use clearly identified thresholds and harvest control rules to adjust quotas to respect the management framework. Although simulation testing is needed to evaluate management model performance under additional sources of uncertainty, this approach has successfully maintained the Harp Seal population at or near the highest level ever seen, during a period of intensive hunting.
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estimation of Harp Seal pagophilus groenlandicus pup production in the north atlantic completed results from surveys in the greenland sea in 2002
Ices Journal of Marine Science, 2006Co-Authors: Tore Haug, Peter J. Corkeron, Garry B. Stenson, Kjell Tormod NilssenAbstract:From 14 March to 6 April 2002 aerial surveys were carried out in the Greenland Sea pack ice (referred to as the “West Ice”), to assess the pup production of the Greenland Sea population of Harp Seals, Pagophilus groenlandicus. One fixed-wing twin-engined aircraft was used for reconnaissance flights and photographic strip transect surveys of the whelping patches once they had been located and identified. A helicopter assisted in the reconnaissance flights, and was used subsequently to fly visual strip transect surveys over the whelping patches. The helicopter was also used to collect data for estimating the distribution of births over time. Three Harp Seal breeding patches (A, B, and C) were located and surveyed either visually or photographically. Results from the staging flights suggest that the majority of Harp Seal females in the Greenland Sea whelped between 16 and 21 March. The calculated temporal distribution of births were used to correct the estimates obtained for Patch B. No correction was considered necessary for Patch A. No staging was performed in Patch C; the estimate obtained for this patch may, therefore, be slightly negatively biased. The total estimate of pup production, including the visual survey of Patch A, both visual and photographic surveys of Patch B, and photographic survey of Patch C, was 98 500 (s.e. = 16 800), giving a coefficient of variation of 17.9% for the survey. Adding the obtained Greenland Sea pup production estimate to recent estimates obtained using similar methods in the Northwest Atlantic (in 1999) and in the Barents Sea/White Sea (in 2002), it appears that the entire North Atlantic Harp Seal pup production, as determined at the turn of the century, is at least 1.4 million animals per year.
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bacular and testicular growth allometry and variation in the Harp Seal pagophilus groenlandicus
Journal of Mammalogy, 1998Co-Authors: Edward H Miller, Andrew R J Stewart, Garry B. StensonAbstract:We investigated quantitative relationships of bacular size to age, length of body, and testicular size in the Harp Seal ( Pagophilus groenlandicus ), based on collections made in the northwestern Atlantic from 1985 to 1992. Bacular growth was faster than growth in length of body except in old Seals (>9 years of age), in which relative growth was isometric. A pubertal spurt in growth in bacular size occurred between 3 and 4 years of age when length increased by 48.3%, mass by 331%, and density by 185%. Concurrently, length of body showed a spurt in growth of 7.2%. Bacular length reached 90% of its asymptotic size of 17.4 cm at ca. 9 years of age, and bacular mass reached that point relative to its asymptote (49.6 g) later at ca. 20 years. In contrast, length of body reached 90% of asymptotic size (176 cm) at only 5–6 years of age. In old Seals, bacular length was correlated positively with length of body and age independently. It averaged 9.9% of length of body in old Seals. Bacular size was variable: CV = 8.3% for bacular length and 32.8% for bacular mass in old Seals. Testicular size peaked in February and March. For young Seals (≤9 years old), growth in bacular length was isometric, and growth in bacular mass was positively allo-metric relative to testicular length and mass. In contrast, testicular length and mass of breeding old Seals were not correlated significantly with bacular size, length of body, or age. In breeding old Seals, testes averaged 10.1 cm in length (range = 7.4–13.2 cm, CV = 10.9%) and 128 g in mass (range = 60.6–204 g, CV = 24.9%), and testicular length averaged 5.7% of length of body. Variation in bacular and testicular size suggests that males have variable reproductive strategies. Comparative analyses on phocid species with known mating systems are needed to test this interpretation.
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quantifying some of the major sources of uncertainty associated with estimates of Harp Seal prey consumption parti uncertainty in the estimates of Harp Seal population size
Journal of Northwest Atlantic Fishery Science, 1997Co-Authors: William G. Warren, Peter A. Shelton, Garry B. StensonAbstract:An effort is made to quantify some of the major sources of uncertainty associated with estimates of Harp Seal (Phoca groenlandica) prey consumption, with special reference to the uncertainty in estimates of Seal population size. A population dynamics model is used, the inputs for which are the annual catches at age and pregnancy rates. Two parameters, instantaneous mortality rate, and the hunting selection on the pups for years prior to the availability of pregnancy data, are estimated by non-linear least squares using available survey estimates of pup production. The uncertainty in estimates of population size is estimated by Monte Carlo methods from the estimates of sampling error in the pregnancy rates and in the survey estimates of pup production, with the catches at age assumed to be known. The uncertainty in the population estimates is dominated by the uncertainty in the survey estimates.
Kit M Kovacs - One of the best experts on this subject based on the ideXlab platform.
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diving behaviour of lactating Harp Seal phoca groenlandica females from the gulf of st lawrence canada
Animal Behaviour, 1993Co-Authors: Christian Lydersen, Kit M KovacsAbstract:Abstract Abstract. Diving behaviour of four lactating Harp Seal females was recorded using time-depth recorders. The females spent 20·6 ± 3·8% (X ± SD) of their time hauled out on the surface of the ice, 34·2 ± 2·5% of the time in the water in a surface position, and 45·2 ± 5·9% of the time diving. A total of 3701 dives were recorded with a mean duration of 3·2 ± 2·4 min. The maximum dive duration recorded was 13 min and maximum recorded depth was 90 m. Only 0·6% of the dives exceeded the estimated aerobic dive limit of 10·4 min. The mean duration of haul-out periods was 1·2 ± 2·3 h. The average time between haul-out episodes was 3·9 ± 1·5 h. The majority of the haul-out periods (86%) were only 20·8 ± 10·3 min long, indicating that in most cases females returned to the ice only to nurse their pups. Longitudinal mass records showed that the females were losing an average of 2·8 ± 0·8 kg daily while pups were gaining an average of 2·3 ± 0·4 kg/day. The average mass transfer efficiency was 86 ± 19%. This extremely high transfer rate, with a recorded maximum of 111% for one mother-pup pair, can only be explained by females consuming some food during the lactation period, which is consistent with the diving records obtained during this study, but in contrast to the general belief that in most phocid species females fast throughout lactation.
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mass transfer efficiency between Harp Seal phoca groenlandica mothers and their pups during lactation
Journal of Zoology, 1991Co-Authors: Kit M Kovacs, D.m. Lavigne, S InnesAbstract:We investigated the efficiency of mass transfer in lactating Harp Seals through serial measurements on individual mother-pup pairs during the whelping seasons of 1988 and 1989. We also compared the influence of longitudinal versus cross-sectional sampling on estimates of the efficiency of mass transfer. Among longitudinally sampled pairs, pups grew at an average rate of 2·3 ± 0·5 (mean ± S.D.) kg/d (N = 20). The concomitant mass loss by females averaged 3·1 ± 0·8 kg/d (N = 19). The mean efficiency of mass transfer was 77·0 ± 13·6% (N= 19 pairs). Estimates of pup growth and female mass loss from regressions of cross-sectional data were 2·0 kg/d and 3·1 kg/d, respectively. These values produce an estimate of 65% for the efficiency of mass transfer. Consistent with the high efficiency of mass transfer, Harp Seal females contribute less of their total body mass to nursing (c. 28%) than most other phocids examined. The resulting energy savings may be important for females of an ice-breeding species, which migrate a long distance shortly after weaning their pups
David W. Johnston - One of the best experts on this subject based on the ideXlab platform.
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Factors Affecting Harp Seal (Pagophilus groenlandicus) Strandings in the Northwest Atlantic
2016Co-Authors: Brianne K. Soulen, Kristina Cammen, Thomas F. Schultz, David W. JohnstonAbstract:The effects of climate change on high latitude regions are becoming increasingly evident, particularly in the rapid decline of sea ice cover in the Arctic. Many high latitude species dependent on sea ice are being forced to adapt to changing habitats. Harp Seals (Pagophilus groenlandicus) are an indicator species for changing high-latitude ecosystems. This study analyzed multiple factors including ice cover, demographics, and genetic diversity, which could affect Harp Seal stranding rates along the eastern coast of the United States. Ice cover assessments were conducted for the month of February in the Gulf of St. Lawrence whelping region from 1991–2010 using remote sensing data, and Harp Seal stranding data were collected over the same time period. Genetic diversity, which may affect how quickly species can adapt to changing climates, was assessed using ten microsatellite markers to determine mean d2 in a subset of stranded and by-caught (presumably healthy) Seals sampled along the northeast U.S. coast. Our study found a strong negative correlation (R2 = 0.49) between ice cover in the Gulf of St. Lawrence and yearling Harp Seal strandings, but found no relationship between sea ice conditions and adult strandings. Our analysis revealed that male Seals stranded more frequently than females during the study period and that this relationship was strongest during light ice years. In contrast, we found no significant difference in mean d2 between stranded and by-caught Harp Seals. The results demonstrate that sea ice cover and demographic factors have a greater influence on Harp Seal stranding rates than genetic diversity, with only a little of the variance in mean d2 among strande
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Factors affecting Harp Seal (Pagophilus groenlandicus) strandings in the Northwest Atlantic.
PloS one, 2013Co-Authors: Brianne K. Soulen, Kristina Cammen, Thomas F. Schultz, David W. JohnstonAbstract:The effects of climate change on high latitude regions are becoming increasingly evident, particularly in the rapid decline of sea ice cover in the Arctic. Many high latitude species dependent on sea ice are being forced to adapt to changing habitats. Harp Seals (Pagophilus groenlandicus) are an indicator species for changing high-latitude ecosystems. This study analyzed multiple factors including ice cover, demographics, and genetic diversity, which could affect Harp Seal stranding rates along the eastern coast of the United States. Ice cover assessments were conducted for the month of February in the Gulf of St. Lawrence whelping region from 1991–2010 using remote sensing data, and Harp Seal stranding data were collected over the same time period. Genetic diversity, which may affect how quickly species can adapt to changing climates, was assessed using ten microsatellite markers to determine mean d2 in a subset of stranded and by-caught (presumably healthy) Seals sampled along the northeast U.S. coast. Our study found a strong negative correlation (R2 = 0.49) between ice cover in the Gulf of St. Lawrence and yearling Harp Seal strandings, but found no relationship between sea ice conditions and adult strandings. Our analysis revealed that male Seals stranded more frequently than females during the study period and that this relationship was strongest during light ice years. In contrast, we found no significant difference in mean d2 between stranded and by-caught Harp Seals. The results demonstrate that sea ice cover and demographic factors have a greater influence on Harp Seal stranding rates than genetic diversity, with only a little of the variance in mean d2 among stranded Seals explained by ice cover. Any changes in these factors could have major implications for Harp Seals, and these findings should be considered in the development of future management plans for the Arctic that incorporate climate variability.
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Towards a precautionary approach to managing Canada's commercial Harp Seal hunt
ICES Journal of Marine Science, 2009Co-Authors: Russell Leaper, D.m. Lavigne, Peter J. Corkeron, David W. JohnstonAbstract:Leaper, R., Lavigne, D. M., Corkeron, P., and Johnston, D. W. 2010. Towards a precautionary approach to managing Canada's commercial Harp Seal hunt. - ICES Journal of Marine Science, 67: 316-320.The Canadian government's approach to the management of its commercial Harp Seal hunt is compared with other precautionary approaches developed for setting anthropogenic removal limits for marine mammal populations. For Canada's Harp Seal hunt, the current management strategy has not been fully specified or tested, and its robustness to changes in biological parameters, uncertainty in input data and environmental variability, remains unknown. As such, the management approach cannot be considered precautionary and there is a substantial, but not quantified, probability that it will not meet its objectives. There is an urgent need for a fully specified and rigorously tested management procedure, and steps towards this are suggested that should reduce the risks associated with the current approach.
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an evaluation of management objectives for canada s commercial Harp Seal hunt 1996 1998
Conservation Biology, 2000Co-Authors: David W. Johnston, P Meisenheimer, D. M. LavigneAbstract:: The largest existing hunt for marine mammals is Canada's commercial hunt for Northwest Atlantic Harp Seals (Pagophilus groenlandicus). From 1995 to 1998, the total allowable catch was set at a level that the Canadian Department of Fisheries and Oceans calculated would not cause the population to decline, consistent both with its stated management objectives of maintaining stable Seal populations while allowing a sustainable harvest and with its stated policy of taking a precautionary approach to management. During those years, Canada's total allowable catch was progressively increased from 186,000 Harp Seals per year (1995) to 250,000 (1996) to 275,000 (1997 & 1998). We examined whether the government's management objectives were achieved using the conventional approach of comparing landed catches with the replacement yield estimated from a biological population model. We then conducted a second assessment, using a more modern and precautionary approach recently implemented for marine mammal management in the United States which incorporates uncertainty into management models to estimate sustainable “potential biological removal levels.” From 1996 to 1998, landed catches from Canada and Greenland exceeded Canada's estimated replacement yield. Over the same period, estimated total human-caused mortality exceeded potential biological removal levels by 1.5 to 5.9 times. Given such levels of reported catches and estimated total human-caused mortality, Canada's management of its Harp Seal hunt did not achieve its objectives. It is likely, therefore, that the population is now declining and, if recent levels of killing continue, the population will stabilize only at levels below (and possibly far below) its maximum net productivity level. Viewed from this perspective, Canada's approach to Harp Seal management between 1996 and 1998 cannot be deemed precautionary or risk-averse. Resumen: Resumen: La caza mas grande de mamiferos marinos que existe es la captura comercial de las focas Harp (Pagophilus groenlandicus) del Canada. De 1995 a 1998 se fijo la captura total permisible a un nivel que, segun el Departamento Canadiense de Pesquerias y Oceanos, no causaria una disminucion de la poblacion, congruente tanto con los objetivos establecidos de manejo dirigidos a mantener poblaciones estables de focas y permitir, a la vez, una cosecha sostenida, como con su politica declarada de adoptar una estrategia de manejo precavido. Durante estos anos, la cosecha total permisible del Canada aumento progresivamente de 186,000 focas por ano (1995), a 250,000 (1996) y a 275,000 (1997 y 1998). Examinamos si se alcanzaron los objetivos de manejo del gobierno usando la estrategia convencional de comparar capturas desembarcadas con la produccion de reemplazo estimada a partir de un modelo de biologia poblacional. Luego realizamos una segunda evaluacion utilizando una estrategia mas moderna y precavida implementada recientemente en los Estados Unidos para el manejo de mamiferos marinos y que incorpora la incertidumbre en los modelos de manejo para estimar los “niveles potenciales de remocion biologica” sostenibles. De 1996 a 1998, las capturas desembarcadas del Canada y Groenlandia excedieron la produccion de reemplazo estimada. Durante el mismo tiempo, la mortalidad total estimada causada por humanos excedio los niveles potenciales de remocion biologica por 1.5 a 5.9 veces. Debido a los niveles de captura reportados y a la mortalidad total estimada causada por humanos, el manejo de la caza de focas P. groenlandicus del Canada no alcanzo los objetivos planteados. Por lo tanto, es probable que la poblacion se encuentre en disminucion y si los recientes niveles de caza continuan, la poblacion se estabilizaraunicamente a niveles por debajo (y posiblemente muy por debajo) de su nivel maximo de productividad neta. Visto desde esta perspectiva, la estrategia del Canada para el manejo de las poblaciones de P. groenlandicus entre 1996 y 1998 no puede considerarse precavido ni adverso al riesgo.
Janneche Utne Skaare - One of the best experts on this subject based on the ideXlab platform.
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organochlorine pesticides and pcbs in the east ice Harp Seal phoca groenlandica population
Marine Environmental Research, 1997Co-Authors: L. Kleivane, Oscar Espeland, K A Fagerheim, Ketil Hylland, A Polder, Janneche Utne SkaareAbstract:Blubber samples from the Eastern Harp Seal (Phoca groenlandica) population were obtained during the moulting season in the Russian sector outside of the White Sea, in April and May 1993. Subcutaneous blubber of adult males and females, and juveniles of both sexes was sampled. The following organochlorines were determined: the industrial chemicals PCBs (polychlorinated biphenyls; 21 individual PCB congeners) and HCB (hexachlorobenzene); and the organochlorine pesticides DDT (dichlorodiphenyltrichloroethane); ΣHCH (sum of hexachlorocyclohexane isomers; α-, β- and γ-HCH); and ΣCHL (sum of chlordane metabolites; oxy chlor done, cis-chlordane and trans-nonachlor). A total of 16 PCB congeners, the p,p′-DDT metabolites, and all the pesticides, except γ-HCH, were detected in all animals. The concentrations of ΣPCB (sum of concentrations of 21 PCB congeners) and ΣDDT (sum of concentrations of p,p′-DDT, p,p′-DDE, p,p′-DDD, o,p′-DDT and o,p′-DDD) ranged from 0.8–9.8 and 0.6–7.9 μg g−1 lipid weight, respectively. The median concentrations of HCB, the chlordane metabolites oxychlordane, cis-chlordane and trans-nonachlor, and the HCH isomers were all < 1 μg g−1 lipid weight. When comparing two adult male groups caught early and late in the moulting period, significantly higher HCB levels were found in the latter and leanest group. Although not statistically significant, the same trend was observed in the case of ΣPCB, ΣDDT, ΣCHL and ΣHCH. There is probably a differentiated relative release of organochlorines from the blubber reservoir during the moult in adult males. Significantly higher concentrations of the three major pollutants (ΣPCB, ΣDDT and ΣCHL) were found in adults as compared to the juveniles, while no such relations were found for ΣHCH or ΣHCB. Although the concentrations of ΣPCB, ΣDDT, ΣCHL and ΣHCH in blubber of different Harp Seal groups were not significantly different with respect to sex, a multiple regression analysis including LMD-index, sex and age indicated that there were lower concentrations of PCB, DDT, CHL and ΣHCH in adult female Seals compared to males and juveniles.
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Seasonal variation of organochlorine concentrations in Harp Seal (Phoca groenlandica)
Developments in Marine Biology, 1995Co-Authors: L. Kleivane, Oscar Espeland, Karl I. Ugland, Janneche Utne SkaareAbstract:Abstract The organochlorine (OCs) pollutants PCB, DDT, chlordanes, HCH and HCB were determined in blubber samples of 97 Harp Seals by capillary gas chromatography. The Harp Seal undergoes dramatic changes in the blubber layer during the year, with a minimum layer in the breeding and moulting periods. Seasonal differences in the OC concentrations between adult Harp Seals (>6 years) of both sexes were found. Highest and lowest OC levels were detected in animals caught during April/May and September, when the animals are at the leanest and at the fattest, respectively. A decline in OC levels in blubber of juvenile Harp Seals was observed from January to May.
Pierreyves Daoust - One of the best experts on this subject based on the ideXlab platform.
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detection and preliminary characterization of phocine distemper virus in a stranded Harp Seal pagophilus groenlandicus from the gulf of st lawrence canada
Journal of Wildlife Diseases, 2020Co-Authors: Pierreyves Daoust, Thais C S Rodrigues, Liam B Shea, Kuttichantran Subramaniam, Thomas B Waltzek, Ole NielsenAbstract:Abstract A lethargic juvenile male Harp Seal (Pagophilus groenlandicus) in poor nutritional condition was found on the beach on the north shore of Prince Edward Island, Canada, in June 2017. Micros...
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detection and preliminary characterization of phocine distemper virus in a stranded Harp Seal pagophilus groenlandicus from the gulf of st lawrence canada
Journal of Wildlife Diseases, 2020Co-Authors: Pierreyves Daoust, Thais C S Rodrigues, Liam B Shea, Kuttichantran Subramaniam, Thomas B Waltzek, Ole NielsenAbstract:A lethargic juvenile male Harp Seal (Pagophilus groenlandicus) in poor nutritional condition was found on the beach on the north shore of Prince Edward Island, Canada, in June 2017. Microscopic examination revealed a severe nonsuppurative encephalitis positive for morbillivirus antigen on immunohistochemistry. Virus isolation attempts were negative. However, phocine distemper virus (PDV) was detected in brain tissue RNA extracts with a seminested reverse transcription PCR that targeted the paramyxovirus RNA-dependent RNA polymerase (pol) gene. Comparison of the resulting partial PDV pol nucleotide sequence revealed it was nearly identical to PDV strains isolated from eastern Atlantic harbor Seals (Phoca vitulina vitulina) during a 1988 epizootic in the Wadden and Irish seas, and a western Atlantic harbor Seal (Phoca vitulina concolor) that stranded in Maine, USA, in 2006. Our study confirmed that closely related PDV strains are circulating in multiple Seal species along the coastlines of North America and Europe.
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the canadian Harp Seal hunt observations on the effectiveness of procedures to avoid poor animal welfare outcomes
Animal Welfare, 2012Co-Authors: Pierreyves Daoust, Charles G B CaraguelAbstract:The Canadian Harp Seal (Pagophilus groenlandicus) hunt has, for several decades, raised public concerns related to animal welfare. The field conditions under which this hunt is carried out do not lend themselves easily to detailed observations and analyses of its killing practices. This article reports observations carried out over several seasons that aimed at obtaining more specific information about the conditions under which Seals are killed, in order to assess potential welfare issues and explore avenues for possible improvements in its practice. A standardised three-step process for killing Seals (ie stunning, checking by palpation of the skull, and bleeding) was recently implemented to maximise the proportion of animals that are killed rapidly with minimum pain. Based on field observations, the rifle and the hakapik, when used properly, appeared to be efficient tools for stunning and/or killing young Harp Seals. All carcases of Seals observed to be killed with a rifle, either on the ice or in the water, could be recovered. However, shooting Seals in water rather than on ice carried a higher risk of poor welfare outcome because of the limited opportunities to shoot the animals again if not stunned with the first shot. Based on current practices, there is no reliable evidence that the Canadian Harp Seal hunt differs from other forms of exploitation of wildlife resources from the perspective of animal welfare. Although opportunistic field observations may be less amenable to generalisation than structured studies, we believe that they reflect the reality of the hunt and provide valuable information to direct the evolution of its practice.
