Comparative Modeling of Cod-Capelin Dynamics in the Newfoundland-Labrador Shelves and Barents Sea Ecosystems

The Atlantic cod (Gadus morhua) stocks in the Newfoundland-Labrador Shelves (NL) and Barents Sea (BS) ecosystems have shown divergent trajectories over the last 40 years. Both stocks experienced either an important decline (BS) or a collapse (NL) in the mid-1980s and early 1990s, respectively. After these population reductions, the BS stock quickly rebounded and it is currently at record high levels, while the NL stock, despite showing some improvement since the mid-2000s, remains at low levels. Fishing and environmental conditions are known to be important drivers of cod dynamics in both ecosystems, especially the availability of high energy prey like capelin (Mallotus villosus), however, the question of how different or similar these two stocks truly are remains. Could, for example, the NL cod stock rebuild if presented to conditions like the ones experienced by BS cod? To explore such questions, we developed a simple biomass dynamic model for cod using a bioenergetic-allometric approach. This model includes fisheries catches and capelin availability as external drivers and was implemented for both ecosystems. Despite the contrasting trends, the model produced very good fits, and showed some remarkably similar estimated parameters in both systems. We explored these similarities by (a) performing the thought experiment of transferring cod stocks between ecosystems by switching estimated key parameters between models and comparing the output, and (b) implementing an integrated model architecture which allowed fitting common parameters for both stocks to evaluate the similarity of key vital rates. Our results indicate that cod trajectories in NL and BS can be reliably described using simple bioenergetic-allometric arguments, fishery catches, and capelin availability. Model parameters that encapsulate intrinsic vital rates were not significantly different between stocks. This indicates that NL and BS cod stocks are biologically similar, and that the differences in their trajectories are driven by the ecosystem context in which these stocks are embedded, and suggests that the NL stock would be expected to rebuild if enough capelin were available. This also indicates that capelin status and trend should be an important consideration for effective management of these cod stocks.publishedVersio

Analysing the natural population growth of a large marine mammal after a depletive harvest

An understanding of the underlying processes and comprehensive history of population growth after a harvest-driven depletion is necessary when assessing the long-term effectiveness of management and conservation strategies. The South American sea lion (SASL), Otaria flavescens, is the most conspicuous marine mammal along the South American coasts, where it has been heavily exploited. As a consequence of this exploitation, many of its populations were decimated during the early 20th century but currently show a clear recovery. The aim of this study was to assess SASL population recovery by applying a Bayesian state-space modelling framework. We were particularly interested in understanding how the population responds at low densities, how human-induced mortality interplays with natural mechanisms, and how density-dependence may regulate population growth. The observed population trajectory of SASL shows a non-linear relationship with density, recovering with a maximum increase rate of 0.055. However, 50 years after hunting cessation, the population still represents only 40% of its pre-exploitation abundance. Considering that the SASL population in this region represents approximately 72% of the species abundance within the Atlantic Ocean, the present analysis provides insights into the potential mechanisms regulating the dynamics of SASL populations across the global distributional range of the species.Fil: Romero, Maria Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Comahue. Instituto de Biología Marina y Pesquera Almirante Storni; ArgentinaFil: Grandi, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Koen Alonso, Mariano. Fisheries And Ocean Canada. Northwest Atlantic Fisheries Centre; CanadáFil: Svendsen, Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Comahue. Instituto de Biología Marina y Pesquera Almirante Storni; ArgentinaFil: Ocampo Reinaldo, Matías. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Comahue. Instituto de Biología Marina y Pesquera Almirante Storni; ArgentinaFil: Garcia, Nestor Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Dans, Silvana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. Universidad Nacional de la Patagonia; ArgentinaFil: González, Raul Alberto Candido. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Comahue. Instituto de Biología Marina y Pesquera Almirante Storni; ArgentinaFil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. Universidad Nacional de la Patagonia; Argentin

Reactivity of Cobalt-Fullerene Complexes towards Deuterium

The adsorption of molecular deuterium (D2) onto charged cobalt-fullerene-complexes ConC60 + (n=1–8) is measured experimentally in a few-collision reaction cell. The reactivity is strongly size-dependent, hinting at clustering of the transition metal atoms on the fullerenes. Formation and desorption rate constants are obtained from the pressure-dependent deuterogenation curves. DFT calculations indeed find that this transition metal clustering is energetically more favorable than decorating the fullerene. For n=1, D2 is predicted to bind molecularly and for n=2 dissociative and molecular configurations are quasi-isoenergetic. For n=3–8, dissociation of D2 is thermodynamically preferred. However, reaching the ground state configuration with dissociated deuterium on the timescale of the experiment may be hindered by dissociation barriers.Fil: Vanbuel, Jan. Katholikie Universiteit Leuven; BélgicaFil: German, Estefania. Universidad de Valladolid; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Libeert, Guillaume. Katholikie Universiteit Leuven; BélgicaFil: Veys, Koen. Katholikie Universiteit Leuven; BélgicaFil: Moens, Janni. Katholikie Universiteit Leuven; BélgicaFil: Alonso, Julio A.. Donostia International Physics Center; España. Universidad de Valladolid; EspañaFil: López, María J.. Universidad de Valladolid; EspañaFil: Janssens, Ewald. Katholikie Universiteit Leuven; Bélgic

Bottom-Up Regulation of Capelin, a Keystone Forage Species

The Northwest Atlantic marine ecosystem off Newfoundland and Labrador, Canada, has been commercially exploited for centuries. Although periodic declines in various important commercial fish stocks have been observed in this ecosystem, the most drastic changes took place in the early 1990s when the ecosystem structure changed abruptly and has not returned to its previous configuration. In the Northwest Atlantic, food web dynamics are determined largely by capelin (Mallotus villosus), the focal forage species which links primary and secondary producers with the higher trophic levels. Notwithstanding the importance of capelin, the factors that influence its population dynamics have remained elusive. We found that a regime shift and ocean climate, acting via food availability, have discernible impacts on the regulation of this population. Capelin biomass and timing of spawning were well explained by a regime shift and seasonal sea ice dynamics, a key determinant of the pelagic spring bloom. Our findings are important for the development of ecosystem approaches to fisheries management and raise questions on the potential impacts of climate change on the structure and productivity of this marine ecosystem

Mapping benthic ecological diversity and interactions with bottom-contact fishing on the Flemish Cap (northwest Atlantic)

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Status and trends of the fish community in the Flemish Cap (NAFO Div. 3M) bioregion

This report summarizes fish community trends for the Flemish Cap (NAFO Div. 3M) based on European Union summer trawl research vessel surveys between 1988 and 2018. Species were classified into eight functional groups and trends were described using biomass indices, biomass and abundance anomalies, and fish size (Biomass/Abundance Ratio) anomalies. In 2003, a replacement of the research vessel allowed extending the depth coverage of the survey from 700m to 1400m. The vessel change had an impact on survey catchability, so to account for it conversion factors were applied. Considering the change in depth coverage, trends were examined for 1988-2018 with data up to 700m, and for 2004-2018 with data up to 1400m. Fish community trends were similar between the two datasets, but the analyses including deeper waters showed a comparatively higher levels of benthivores, reflecting the changes in community structure with depth. Generally speaking, trends in average fish size as tracked by the Biomass/Abundance Ratio appeared driven by recruitment, where general declines in abundance and absences of good recruitments got reflected in increases of this ratio. Biomass of plankpiscivores (mostly Sebastes sp.) experienced a sharp increase in the early 2000s but then returned to levels comparable to the 1990s. Piscivores biomass showed a strong decline in the early 1990s due to the collapse of cod but has since shown signs of recovery. Shellfish, driven by northern shrimp, saw a sustained increase in biomass from the early 1990s until 2002, when started a decline that has persisted until 2018. The biomass of large benthivores decline in the late 1990s and remains low to this date

Advances in the Assessment of Habitat Fragmentation and Protection in the NAFO Regulatory Area

NAFO has used kernel density analyses to identify VMEs dominated by large-sized sponges, sea pens, small and large gorgonian corals, erect bryozoans, sea squirts (Boltenia ovifera), and black corals. That analysis generates polygons of significant concentrations of biomass for each VME indicator which are spread across the spatial domain of the NAFO fishing footprint. There is potential for bottom contact fishing to induce changes in both the amount and configuration of habitat (e.g., decreased polygon size, increased polygon isolation, and increased edge area) through direct and indirect impacts, and it is unknown to what degree such changes may already have taken place given the long fishing history of the area. In the Report of the 13th Meeting of the NAFO Scientific Council Working Group on Ecosystem Science and Assessment (WGE-ESA), preliminary work on assessing and monitoring habitat fragmentation was presented. Here we continue that work by recalculating the indices after removing connections that are not identified through particle tracking models. We have reanalyzed the nearest neighbour distances and PX, a proximity index, for the VME polygons noted above, and for the new closed areas that will come into effect 1 January 2022. We show that PX when applied to the new closures appears sensitive to their spatial configuration which bodes will for the ability of this index to identify habitat fragmentation in the future, brought about through fishing activities and/or natural disturbances.Versión del edito

Cambio en la estrategia de alimentación de las hembras del león marino sudamericano (Carnivora: Pinnipedia) tras el parto

This study tests the hypothesis that female South American sea lions shift from off-shore, pelagic prey to coastal, benthic prey after parturition in order to reduce the foraging trip duration and hence the time pups remain unattended on the beach during early lactation. The δ13C and δ15N values of the serum and blood cells of 26 South American sea lion suckling pups from northern Patagonia were used to track the dietary changes of their mothers from late pregnancy to early lactation, after correction for differential isotopic fractionation between tissues. Primary producers and potential prey species were also analysed to establish a baseline for interpreting the stable isotope concentration of serum and blood cells. Isotopic ratios revealed a generalized increase in the consumption of coastal-benthic prey after parturition. Such a generalized post-partum shift will allow females to spend more time on land and look after their pups. The effects of this foraging strategy on the nutritional quality of the female’s diet are discussed.El presente estudio pretende comprobar si las hembras del león marino sudamericano adoptan una dieta más bentónica y costera tras el parto, con el fin de reducir la duración de los viajes de alimentación y reducir así el tiempo durante el cual las crías permanecen desatendidas en la playa. Para ello, se determinaron las concentraciones de isótopos estables de carbono y nitrógeno en el suero y las células sanguíneas de 26 crías lactantes de león marino sudamericano del norte de la Patagonia, con el fin de reconstruir la dieta de la madre durante la parte final de la gestación y el inicio de la lactancia, tras la correspondiente corrección del fraccionamiento isotópico entre tejidos. También se analizaron muestras de productores primarios y de presas potenciales para ayudar en la interpretación de los resultados. Las concentraciones de isótopos estables antes y después del parto confirmaron un incremento en el consumo de presas bentónicas costeras tras el parto. Este cambio generalizado de dieta tras el parto permitiría a las hembras incrementar el tiempo que pasan junto a las crías. Se discuten los efectos que esta estrategia puede tener sobre la calidad de la dieta de las hembras

Posttraumatic stress disorder associated with unexpected death of a loved one: Cross-national findings from the world mental health surveys

Background: Unexpected death of a loved one (UD) is the most commonly reported traumatic experience in cross‐national surveys. However, much remains to be learned about posttraumatic stress disorder (PTSD) after this experience. The WHO World Mental Health (WMH) survey initiative provides a unique opportunity to address these issues. Methods: Data from 19 WMH surveys (n = 78,023; 70.1% weighted response rate) were collated. Potential predictors of PTSD (respondent sociodemographics, characteristics of the death, history of prior trauma exposure, history of prior mental disorders) after a representative sample of UDs were examined using logistic regression. Simulation was used to estimate overall model strength in targeting individuals at highest PTSD risk. Results: PTSD prevalence after UD averaged 5.2% across surveys and did not differ significantly between high‐income and low‐middle income countries. Significant multivariate predictors included the deceased being a spouse or child, the respondent being female and believing they could have done something to prevent the death, prior trauma exposure, and history of prior mental disorders. The final model was strongly predictive of PTSD, with the 5% of respondents having highest estimated risk including 30.6% of all cases of PTSD. Positive predictive value (i.e., the proportion of high‐risk individuals who actually developed PTSD) among the 5% of respondents with highest predicted risk was 25.3%. Conclusions: The high prevalence and meaningful risk of PTSD make UD a major public health issue. This study provides novel insights into predictors of PTSD after this experience and suggests that screening assessments might be useful in identifying high‐risk individuals for preventive interventions

Post-traumatic stress disorder associated with natural and human-made disasters in the World Mental Health Surveys

Background: Research on post-traumatic stress disorder (PTSD) following natural and human-made disasters has been undertaken for more than three decades. Although PTSD prevalence estimates vary widely, most are in the 20–40% range in disaster-focused studies but considerably lower (3–5%) in the few general population epidemiological surveys that evaluated disaster-related PTSD as part of a broader clinical assessment. The World Mental Health (WMH) Surveys provide an opportunity to examine disaster-related PTSD in representative general population surveys across a much wider range of sites than in previous studies. Method: Although disaster-related PTSD was evaluated in 18 WMH surveys, only six in high-income countries had enough respondents for a risk factor analysis. Predictors considered were socio-demographics, disaster characteristics, and pre-disaster vulnerability factors (childhood family adversities, prior traumatic experiences, and prior mental disorders). Results: Disaster-related PTSD prevalence was 0.0–3.8% among adult (ages 18+) WMH respondents and was significantly related to high education, serious injury or death of someone close, forced displacement from home, and pre-existing vulnerabilities (prior childhood family adversities, other traumas, and mental disorders). Of PTSD cases 44.5% were among the 5% of respondents classified by the model as having highest PTSD risk. Conclusion: Disaster-related PTSD is uncommon in high-income WMH countries. Risk factors are consistent with prior research: severity of exposure, history of prior stress exposure, and pre-existing mental disorders. The high concentration of PTSD among respondents with high predicted risk in our model supports the focus of screening assessments that identify disaster survivors most in need of preventive interventions