NAMMCO Scientific Publications 2022-03-02T10:48:12+01:00 Albert Chacón Open Journal Systems <p>The NAMMCO Scientific Publications series makes available in published, peer-reviewed form, scientific knowledge that is important for decision-making on the conservation and management of marine mammals.</p> Pup production of Harp Seals in the Northwest Atlantic in 2017 during a time of ecosystem change 2022-02-07T11:14:20+01:00 Garry Stenson Jean- François Gosselin John Lawson Alejandro Buren Pierre Goulet Shelley Lang Kjell Tormod Nilssen Mike Hammill <p>Photographic and visual aerial surveys were conducted off Newfoundland and Labrador (”the Front<em>”</em>), and in the Gulf of St. Lawrence (“Gulf<em>”</em>) in March 2017 to estimate pup production of Northwest Atlantic harp seals (<em>Pagophilus groenlandicus</em>). Traditionally, harp seals pup (<em>whelp</em>) in three general areas; the southern Gulf of St. Lawrence, the northern Gulf of St. Lawrence, and off the east coast of Newfoundland and Labrador. After extensive reconnaissance, four whelping areas were identified: one in each of the southern and northern Gulf, and two at the Front. We estimated a total pup production in 2017 of 746,500 (SE=89,900, CV=12%), the lowest since 1994. Most (96%) pups were born at the Front (714,600 pups, SE=89,700). Very few pups were born in the southern Gulf (18,300, SE=1,500) and no whelping concentrations were observed prior to March 5, approximately one week later than previously observed. This is far lower than the 2012 survey estimate of 115,500 (SE=15,100) for the same area. Pup production in the northern Gulf was also lower than in previous years, at 13,600 (SE=3,000). The timing of births in the southern Gulf was much later than normal in 2017, and unusually early pupping at the Front suggests that some females from the Gulf herd may have moved to the Front to whelp due to a lack of ice suitable for pupping (i.e., thin first year) in the Gulf. Harp seals whelp in large concentrations. While one large whelping concentration formed at the Front, approximately 15% of the pupping at the Front occurred in small, dispersed groups which formed later than observed in previous years. Given the unusual ice conditions, distribution of whelping seals, and timing of pupping, assessing the results of the 2017 surveys relative to other estimates of pup production in the Northwest Atlantic is challenging and indicates the ongoing difficulties of assessing a population that is being impacted by climate change.</p> 2022-08-08T00:00:00+02:00 Copyright (c) 2022 Garry Stenson, Jean- François Gosselin, Jack Lawson, Alejandro Buren, Pierre Goulet, Shelley Lang, Kjell Tormod Nilssen, Mike Hammill Recent Harp and Hooded Seal Pup Production Estimates in the Greenland Sea Suggest Ecology-Driven Declines 2021-08-25T11:16:17+02:00 Martin Biuw Tor Arne Øigård Kjell Tormod Nilssen Garry Stenson Lotta Lindblom Michael Poltermann Martin Kristiansen Tore Haug <p>Pup production of the Greenland Sea populations of harp (Pagophilus groenlandicus) and hooded (Cystophora cristata) seals were estimated based upon aerial surveys in March 2018. One fixed-wing aircraft was used for large-area reconnaissance flights to identify the whelping concentrations and to carry out photographic surveys along systematic transects over the whelping areas. A helicopter, operated from an ice-going vessel, flew more localised reconnaissance flights, deployed GPS beacons within the detected whelping concentrations to monitor ice movements, and determined the proportion of pups in specific age-related developmental stages. While the entire estimated pupping region should ideally be covered during one day, photographic surveys in 2018 were carried out on two consecutive days, March 27 and 28, with slightly different survey designs between the two days to account for potential gaps in coverage caused by changes in visibility and cloud cover. Surveys on the two days were partially overlapping, and pup production estimates were consistent when using different combinations of transects from the two days, suggesting that these photographic counts give a relatively robust estimate of pup production in 2018. The combination of surveys that was deemed most appropriate (in terms of maximum coverage with minimum risk of double coverage) yielded an estimated harp seal pup production of 54,181 (SE=9,236, CV=0.17), which is significantly lower than estimates obtained in similar surveys in 2002, 2007, and 2012. Estimated hooded seal pup production was 12,977 (SE=1,823, CV=0.14), which is lower than estimates obtained from surveys in 2005 and 2007, but similar to estimates from the most recent survey in 2012. The reasons for these declines are unknown, but similar declines in the Barents Sea and White Sea harp seals in the mid-2000s suggest that large-scale environmental or ecological changes affecting the Barents Sea and the Norwegian Sea may be important factors.</p> 2022-01-19T00:00:00+01:00 Copyright (c) 2022 Martin Biuw, Tor Arne Øigård, Kjell Tormod Nilssen, Garry Stenson, Lotta Lindblom, Michael Poltermann, Martin Kristiansen, Tore Haug Recent trends in temporal and geographical variation in blubber thickness of common Minke whales (Balaenoptera acutorostrata acutorostrata) in the Northeast Atlantic 2022-03-02T10:48:12+01:00 Hiroko Solvang Tore Haug Nils Øien <p>The common minke whale (<em>Balaenoptera acutorostrata acutorostrata</em>) is a migratory species, and the summer period is generally characterized by intensive feeding and consequently seasonal fattening at high latitudes. The fat deposited is stored as energy reserves for overwintering at lower latitudes where feeding is supposed to be greatly reduced. It is therefore expected that their body condition on the summer feeding grounds will reflect foraging success during their most intensive feeding period and thus indicate how well the high latitude ecosystems can support the populations. During the commercial catch operations on feeding grounds in Norwegian waters, body condition data (blubber thickness and girth) have been collected from 13 937 common minke whales caught during the period 1993-2020. To investigate associations between body condition and area usage in minke whales, we applied three statistical approaches: regressions, canonical correlations, and spatiotemporal effect estimations. The analyses revealed a significant negative trend in blubber thickness from 1993 until 2015. After 2015, the trend was reversed, and blubber thickness values increased significantly. It has previously been suggested that there may be a link between the decreased minke whale blubber thickness and the abundance of the Northeast Arctic cod (Gadus morhua) stock which increased to a record high level between 2006 and 2013. Recruitment to the cod stock in more recent years has been low with a subsequent and continuous decrease in the total stock after 2013 to a current level which is presumably approximately 60% of the 2013 level. Interestingly, the observed common minke whale body condition was at its lowest in 2015, after which it has increased. This may support a connection between cod abundance and common minke whale body condition.</p> 2022-09-28T00:00:00+02:00 Copyright (c) 2022 Hiroko Solvang, Tore Haug, Nils Øien Developments in the Quantitative Assessment of Welfare Outcomes in Hunted Mammals Subject to Shooting 2021-08-02T12:40:19+02:00 Samuel D. G. Smith Kathrine A. Ryeng <p>Knowledge gaps surrounding animal welfare assessment in hunted terrestrial wild mammals and seals were highlighted in the reviews by Knudsen (2005) and EFSA (2007). Following these reviews, the present paper aims to report on developments in the quantitative assessment of welfare outcomes in wild mammals killed via rifle shooting, and modern explosive harpoon grenades used in the killing of whales. Time to death (TTD) and instantaneous death rate (IDR) are widely accepted ante-mortem variables for assessing the duration of suffering during the killing process. The addition of post-mortem assessments allows for validation of TTD and IDR, thus providing a more accurate appraisal of animal welfare during hunting. While this combined assessment for large cetaceans has been implemented since the 1980s in the Norwegian minke whale (Balaenoptera acutorostrata) hunt, we report that this approach has been implemented in studies of the Icelandic minke and fin whale (Balaenoptera physalus) hunts, as well as the Canadian and Norwegian commercial harp seal (Pagophilus groenlandicus) hunts. Additionally, this approach has been incorporated into welfare studies in terrestrial herbivore management programmes. Quantitative welfare assessment during hunts is capable of effectively evaluating the weapons used and judging modifiable variables such as projectile choice, optimal shooting procedure, as well as identifying areas for improvement in hunter training. In moving towards a standardised approach for welfare outcome assessment, an established framework can effectively allow all hunts to be contrasted and allow for identification of optimal strategies that minimise animal suffering.</p> 2022-07-20T00:00:00+02:00 Copyright (c) 2022 Samuel D. G. Smith, Kathrine A. Ryeng Report of the NAMMCO-ICES Workshop on Seal Modelling (WKSEALS 2020) 2021-05-18T21:25:58+02:00 Sophie Smout Kimberly Murray Geert Aarts Martin Biuw Sophie Brasseur Alejandro Buren Fanny Empacher Anne Kirstine Frie James Grecian Mike Hammill Bjarni Mikkelsen Arnaud Mosnier Aqqalu Rosing-Asvid Debbie Russell Hans Skaug Garry Stenson Len Thomas Jay ver Hoef Lars Witting Vladimir Zabavnikov Tor Arne Øigård Ruth Fernandez Fern Wickson <p>To support sustainable management of apex predator populations, it is important to estimate population size and understand the drivers of population trends to anticipate the consequences of human decisions. Robust population models are needed, which must be based on realistic biological principles and validated with the best available data. A team of international experts reviewed age-structured models of North Atlantic pinniped populations, including Grey seal (Halichoerus grypus), Harp seal (Pagophilus groenlandicus), and Hooded seal (Cystophora cristata). Statistical methods used to fit such models to data were compared and contrasted. Differences in biological assumptions and model equations were driven by the data available from separate studies, including observation methodology and pre-processing. Counts of pups during the breeding season were used in all models, with additional counts of adults and juveniles available in some. The regularity and frequency of data collection, including survey counts and vital rate estimates, varied. Important differences between the models concerned the nature and causes of variation in vital rates (age-dependent survival and fecundity). Parameterisation of age at maturity was detailed and time-dependent in some models and simplified in others. Methods for estimation of model parameters were reviewed and compared. They included Bayesian and maximum likelihood (ML) approaches, implemented via bespoke coding in C, C++, TMB or JAGS. Comparative model runs suggested that as expected, ML-based implementations were rapid and computationally efficient, while Bayesian approaches, which used MCMC or sequential importance sampling, required longer for inference. For grey seal populations in the Netherlands, where preliminary ML-based TMB results were compared with the outputs of a Bayesian JAGS implementation, some differences in parameter estimates were apparent. For these seal populations, further investigations are recommended to explore differences that might result from the modelling framework and model-fitting methodology, and their importance for inference and management advice. The group recommended building on the success of this workshop via continued collaboration with ICES and NAMMCO assessment groups, as well as other experts in the marine mammal modelling community. Specifically, for Northeast Atlantic harp and hooded seal populations, the workshop represents the initial step towards a full ICES benchmark process aimed at revising and evaluating new assessment models.</p> 2021-05-18T00:00:00+02:00 Copyright (c) 2021 Sophie Smout, Kimberly Murray, Geert Aarts, Martin Biuw, Sophie Brasseur, Alejandro Buren, Fanny Empacher, Anne Kirstine Frie, James Grecian, Mike Hammill, Bjarni Mikkelsen, Arnaud Mosnier, Aqqalu Rosing-Asvid, Debbie Russell, Hans Skaug, Garry Stenson, Len Thomas, Jay ver Hoef, Lars Witting, Vladimir Zabavnikov, Tor Arne Øigård, Ruth Fernandez, Fern Wickson