Summer Mortality Research Articles

The differences of bacterial communities in the tissues between healthy and diseased Yesso scallop (Patinopecten yessoensis)

The tissues of marine invertebrates are colonized by species-rich microbial communities. The dysbiosis of host’s microbiota is tightly associated with the invertebrate diseases. Yesso scallop (Patinopecten yessoensis), one of the most important maricultured scallops in northern China, has recently suffered massive summer mortalities, which causes huge production losses. The knowledge about the interactions between the Yesso scallop and its microbiota is important to develop the strategy for the disease prevention and control. In the present study, the bacterial communities in hemolymph, intestine, mantle and adductor muscle were compared between the healthy and diseased Yesso scallop based on the high-throughput sequencing of 16S rRNA gene. The results indicated obvious difference of the composition rather than the diversity of the bacterial communities between the healthy and diseased Yesso scallop. Vibrio, Francisella and Photobacterium were found to overgrow and dominate in the mantle, adductor muscle and intestine of the diseased scallops, respectively. The prediction of bacterial community metagenomes and the variations of KEGG pathways revealed that the proportions of the pathways related with neurodegenerative diseases and carbohydrate metabolism both increased significantly in the mantle and hemolymph of the diseased scallops. The abundance of the metabolism pathways including carbohydrate metabolism, lipid metabolism and amino acid metabolism decreased significantly in the intestine of diseased scallops. The results suggested that the changes of bacterial communities might be closely associated with the Yesso scallop’s disease, which was helpful for further investigation of the pathogenesis as well as prevention and control of the disease in Yesso scallop.

Temporal variation in foraging activity and grouping patterns in a mountain-dwelling herbivore: Environmental and endogenous drivers

In temperate ecosystems, seasonality influences animal behaviour. Food availability, weather, photoperiod and endogenous factors relevant to the biological cycle of individuals have been shown as major drivers of temporal changes in activity rhythms and group size/structure of herbivorous species. We evaluated how diurnal female foraging activity and grouping patterns of a mountain herbivore, the Apennine chamois Rupicapra pyrenaica ornata, varied during a decreasing gradient of pasture availability along the summer-autumn progression (July–October), a crucial period for the life cycle of mountain ungulates.Females increased diurnal foraging activity, possibly because of constrains elicited by variation in environmental factors. Size of mixed groups did not vary, in contrast with the hypothesis that groups should be smaller when pasture availability is lower. Proportion of females in groups increased, possibly suggesting that they concentrated on patchily distributed nutritious forbs. Occurrence of yearlings in groups decreased, which may have depended on dispersal of chamois in this age class. Presence of kids in groups did not show variation through summer-autumn, suggesting a close mother-juvenile relationship even at the end of weaning and/or, possibly, low summer mortality. Both endogenous and environmental factors contribute to shape variation in foraging activity and grouping behaviour in mountain-dwelling herbivores.

Microbial Causes of Summer Mortality in Farmed Fish in Egypt

Bacterial diseases are responsible for sever mortalities and morbidities in cultured Nile tilapia in Egypt in various fresh water fish farms and the increase of water temperature in summer has a significant effect on mortalities. A total number of 100 clinically diseased Nile Tilapia (Orechromis niloticus) were collected alive randomly from Abbassa, Elsharkia (Central Laboratory for Aquaculture Research) Egypt, to identify the bacterial pathogens affect that fish. Samples were isolated from liver, kidney, spleen, eye, ulcer and brain. The isolated fish pathogens were identified as Aeromonas hydrophila, Ps.fluorescense, Ps.putida and V.cholera by their morphological characteristics, biochemical tests, Antibiotic sensitivity test and polymerase chain reaction test as a confirmatory results. The results of Anmicrobial sensitivity of the isolated strains revealed that tetracycline (TE30), oxytetracycline (T30), nalidixic acid (NA30), norfloxacin (NOR10) and sulpha-Trimethoprim (SXT25) were the drugs of choice against Aeromonas hydrophila, tetracycline (TE30),oxytetracycline (T30), tobramicin (TOB10) and kanamycin (K30) were the drugs of choice against Pseudomonas flurocence, streptomycin (S10), tobramicin (TOB10), and kanamycin (K30) were the drugs of choice against Pseudomonas putida While oxytetracycline (T30) and nalidixic acid (NA30) were the drugs of choice against Vibrio cholera. The results of Polymerase Chain Reaction (PCR) confirmed the antibiotic sensitivity test results and also confirmed the incidence of Aeromonas hydrophila, Pseudomonas flurocence and Vibrio cholera in the infected fish.

Urban environmental influences on the temperature–mortality relationship associated mental disorders and cardiorespiratory diseases during normal summer days in a subtropical city

Temperature is associated with mortality risk across cities. However, there is lack of study investigating the summer effect on mortality associated with mental/behavioral disorders, especially in cities with subtropicalclimate. In addition, summer mortality in subtropical cities is different from tropical cities, and previous studies have not investigated the urban environmental inequality on heat mortality associated with mental/behavioral disorders. A register-based study was developed to estimate the temperature effects on decedents on days with 50th percentile of average daily temperature between 2007 and 2014 in Hong Kong (n= 133,359). Poisson regression was firstlyapplied to estimate the incidence rate ratio (IRR) from the summer temperature effects on all-cause mortality, cardiovascular mortality, respiratory mortality, and mortality associated with mental/behavioral disorders. For a 1°C increase in average temperatureon days with temperature ≥ 24.51 °C, IRRs of mortality associated with mental and behavioral disorders on lag 0 and lag 1days were 1.033 [1.004, 1.062] and 1.030 [1.002, 1.060], while temperature effects on cardiovascular mortality and respiratory mortality during normal summer days (not extreme heat events) were not significant. A further investigation with linear regression has shown that decedents with mental/behavioral disorders on higher temperature days resided in areas with lower percentage of sky view, lower percentage of vegetation cover, higher level of neighborhood-level PM2.5, higher level of neighborhood-level NO, and higher level of neighborhood-level black carbon (BC). In order to develop protocols for community healthcare based on the "Leaving no one behind" scheme documented in the 2016 Sustainable Development Goals report of the United Nations, it is necessary to include heat effects on mental/behavioral disorders, especially people with dementia, for community planning and healthcare development.

Physiological responses of the abalone Haliotis discus hannai to daily and seasonal temperature variations

Organisms inhabiting tidal mixing-front zones in shallow temperate seas are subjected to large semidiurnal temperature fluctuations in summer. The ability to optimize energy acquisition to this episodic thermal oscillation may determine the survival, growth and development of these ectotherms. We compared the physiological and molecular responses of Haliotis discus hannai cultivated in suspended cages to fluctuating or stable temperature conditions. Several physiological indicators (respiration, excretion rates and O:N) were measured in both conditions, and alterations in the proteome during thermal fluctuations were assessed. No summer mortality was observed in abalone cultivated in fluctuating temperatures compared with that at stable high temperatures. Metabolic rates increased sharply during stable warm summer conditions and fluctuated in accordance with short-term temperature fluctuations (20–26 °C). Ammonia excretion rates during acute responses were comparable in both conditions. When abalone were exposed to fluctuating temperatures, enzyme activities were downregulated and structure-related protein expression was upregulated compared with that at an acclimation temperature (26 °C), highlighting that exposure to low temperatures during fluctuations alters molecular processes. Our results reveal that modulation of physiological traits and protein expression during semidiurnal thermal fluctuations may buffer abalone from the lethal consequences of extreme temperatures in summer.

Summer Development and Survivorship of the Weed Biocontrol Agent, Mecinus janthiniformis (Coleoptera: Curculionidae), Within Stems of Its Host, Dalmatian Toadflax (Lamiales: Plantaginaceae), in Utah.

The summer phenology and survivorship of the stem-mining weevil, Mecinus janthiniformis Toševski and Caldara, a biocontrol agent of Dalmatian toadflax, Linaria dalmatica (L.) Miller, was studied in 2015-2016 as it developed within host plant stems at a low elevation, open rangeland site in northern Utah. Hatching from eggs in spring and early summer, weevils occurred as larvae within stems in June. Earliest maturing adults occurred in mid-July, and the majority of individuals had completed pupal development by early August. Survivorship within stems was high, with two-thirds or more of individuals surviving from egg hatch to adulthood as assessed in mid-September. Mortality rates within stems were highest during larval development, with parasitism accounting for the majority of deaths. At least three parasitoid species (Chalcidoidea: Pteromalidae and Eupelmidae), including both endoparasitoids and ectoparasitoids, were found attacking weevils within stems. Although most surviving weevils remained as adults within stems to overwinter, some adults were found to have chewed exit holes, and in some cases had exited from stems, beginning in July; the fate of these prematurely exiting adults is unknown. Low summer mortality rates within stems should promote weevil establishment under the hot, dry conditions of northern Utah, but parasitism and premature exiting of adults from host stems merit further investigation concerning their potential to reduce biocontrol efficacy. The results presented here for M. janthiniformis phenology within host stems will contribute to the development of standardized, summer monitoring for this biocontrol agent by stem dissection.

Tracking Triploid Mortalities of Eastern Oysters Crassostrea virginica in the Virginia Portion of the Chesapeake Bay

Since 2012, aquacultured eastern oysters Crassostrea virginica have been reported by oyster farmers to display mortality approaching 30%, and in some cases 85%, in areas of the lower Chesapeake Bay, VA. Based on accounts from industry, this mortality has typically affected 1-y-old oysters between May and early July, and has tended to occur in triploid oysters, which represent the vast bulk of production in the area. During this period, samples submitted for pathology have not revealed the presence of major pathogens as a cause. In 2015, to gain deeper insight into this mortality and determine whether specific sites, ploidy condition, or genetic lines were affected, oyster seed commercially produced in early 2014 were obtained from four lines, one diploid (2N DEBY) and three triploid (3N DEBY, 3N hANA, and 3N Northern). These lines were deployed in July 2014 at aquaculture farms at five Chesapeake Bay locations: Locklies Creek and Milford Haven on the western shore, and Pungoteague Creek, Nassawadox Creek, and Cherrystone Creek on the Eastern Shore. During this study, mortality was observed to peak in June at most sites, reaching a mean mortality across all tested lines of 17.0% and a cumulative mortality for the study period of 32.0% at Nassawadox Creek, the site most severely affected by mortality that followed the expected early summer mortality pattern. Interval mortality at all sites decreased to under 5% after June, but cumulative levels for the study period reached from 8.8% to 18.6% even at the sites least affected by mortality. This represents a high level of mortality given the documented absence of material involvement by major oyster pathogens such as Hapolosporidium nelsoni and Perkinsus marinus. Infiltration of gill tissues by hemocytes, observed in up to 33% of individuals at Nassawadox Creek coincident with the increase in mortality, was the only pathology observed. Harmful algal blooms were not associated with the mortality, nor were abnormal temperatures or salinities. There was no clear relationship of mortality to oyster genetic heritage, although there was variability in susceptibility among oyster lines and interactions between lines and specific sites. At some locations and in comparison with diploids, triploid oysters appeared to be more susceptible to mortality. Mortality in triploids was coincident with the timing of peak gametogenic development in diploids. Given the lack of involvement by major pathogens and the possible association of mortality with oyster gametogenesis, future work should seek to better understand the suite of environmental stressors potentially impacting cultured oysters in these systems and their interactions with the physiology and energetics of these animals.

Temperature-Related Summer Mortality Under Multiple Climate, Population, and Adaptation Scenarios.

Projections of the magnitude and pattern of possible health risks from climate change should be based on multiple climate and development scenarios to describe the range of uncertainties, to inform effective and efficient policies. For a better understanding of climate change-related risks in seven metropolitan cities of South Korea, we estimated temperature-related summer (June to August) mortality until 2100 using projected changes in climate, population, and adaptation. In addition, we extracted the variations in the mortality estimates associated with uncertainties in climate, population, and adaptation scenarios using 25 climate models, two Representative Concentration Pathways (RCP 4.5 and 8.5), three population scenarios (high, medium and low variants), and four adaptation scenarios (absolute threshold shift, slope reduction in the temperature-mortality relationship, a combination of slope reduction and threshold shift, and a sigmoid function based on the historical trend). Compared to the baseline period (1991–2015), temperature-attributable mortality in South Korea during summer in the 2090s is projected to increase 5.1 times for RCP 4.5 and 12.9 times for RCP 8.5 due to climate and population changes. Estimated future mortality varies by up to +44%/−55%, −80%, −60%, and +12%/−11% associated with the choice of climate models, adaptation, climate, and population scenarios, respectively, compared to the mortality estimated for the median of the climate models, no adaptation, RCP 8.5, and medium population variant. Health system choices about adaptation are the most important determinants of future mortality after climate projections. The range of possible future mortality underscores the importance of flexible, iterative risk management.

Abnormal mortality of triploid adult Pacific oysters: Is there a correlation with high gametogenesis in Normandy, France?

Summer mortalities of the adult Pacific oysters Crassostrea gigas are an important economic concern. In 2015 and 2016, the mortality of hatchery origin spat comprising 4 diploid batches and 9 triploid batches as well as 12 batches of wild caught diploids was followed at 3 sites in Normandy. Abnormal mortalities (>20%) were observed at one site only and were significantly higher in triploid animals (P < .05). Triploid oysters are believed to be partially sterile but a high level of gametogenesis was observed in all monitored triploid batches. In 2015, preliminary results revealed that triploid oysters underwent strong gametogenesis with mature gametes (stage 3) and 50% of them were non-perturbed (i.e. named alpha). In 2016, 42% of triploid oysters were alpha. This study revealed that triploid oyster maturation occurred in September, which corresponded to the time of high mortalities in Normandy.

Hemolymph and transcriptome analysis to understand innate immune responses to hypoxia in Pacific abalone

Hypoxia was thought to inhibit immune responses, causing severe mortality to marine organisms. The Pacific abalone, Haliotis discus hannai, is the most widely cultured abalone species in China, but suffering from “summer mortality” in which hypoxia has been one of the main reasons. The effect of hypoxia exposure on immune responses in H. discus hannai was investigated, including cellular immune response using flow cytometry and transcriptome profiles. The influence of hypoxia treatment on the total hemocyte count (THC) of H. discus hannai was rather limited but the hemocyte survival rate of abalone increased during 48 h exposure. There was an initial rise in the production of phagocytes and reactive oxygen species (ROS) shortly (3 h) after hypoxic stimulation, but finally decreased after 48 h. This indicates that hypoxia inhibited redox activity of abalone. RNA-seq studies of gill tissues also revealed immune response mechanism in abalone after 24 h of hypoxia. Totally 954 differentially expressed genes (DEGs) were detected under different degrees of deoxygenation. Though oxidation-reduction turbulence was a result of both up- and down-regulated DEGs, cell death/apoptosis induction resulted from up-regulated DEGs, whilst DNA metabolic and immunity suppression resulted from down-regulated DEGs. In summary, our data provides evidence that deoxygenation greatly affects abalone immunity, probably making it more vulnerable. The present study also lays the foundation for further research in hypoxia-associated conditions in abalone aquaculture.

Effects of thermal stress on oxidative stress and antioxidant response, heat shock proteins expression profiles and histological changes in Marsupenaeus japonicus

Water temperature is a crucial ecological factor in aquatic environments. In the context of global warming, aquatic organisms are inevitably subject to thermal stress. The kuruma shrimp Marsupenaeus japonicus is an important commercial crustacean and has become one of the most important species in shrimp fisheries and aquaculture in China. However, M. japonicus showed relatively poor thermotolerance and frequently suffers mass mortalities during the summer months. The thermally sensitive properties of this species also make it a potential indicator species to reflect thermal alteration. Since this species raises both commercial and scientific interests, we investigated the effects of thermal stress on M. japonicus with special emphases on oxidative stress and antioxidant response, heat shock proteins expression profiles and histological changes. The results revealed that transcription of antioxidant enzymes (MjSeGpx and MjGSTMu) and heat shock proteins (Mjhsp60, Mjhsp70 and Mjhsp90) were all dramatically induced in both hepatopancreas and gill of M. japonicus under thermal stress with various expression patterns, and the up-regulated extent of the five genes exhibited a tendency of increasing with temperature. Several oxidative stress biomarkers, including MDA content, CAT activity, SOD activity and GST activity were assessed. The CAT activity was found to be more inducible than SOD and GST activities under thermal stress. In contrast to the higher basal antioxidant enzymes activities in the gill than that in the hepatopancreas, the hepatopancreas exhibited higher MDA content than that of gill. In consistent with the relatively higher MDA content, histological alterations appeared in the hepatopancreas of M. japonicus under thermal stress. This study provided comprehensive clues for uncovering the mechanisms underlying the thermal stress response and summer mortality syndrome of M. japonicus and evaluating the bioindicator potential of this species.

Different Transcriptomic Responses to Thermal Stress in Heat-Tolerant and Heat-Sensitive Pacific Abalones Indicated by Cardiac Performance.

The Pacific abalone Haliotis discus hannai is one of the most economically important mollusks in China. Even though it has been farmed in southern China for almost 20 years, summer mortality remains the most challengeable problem for Pacific abalone aquaculture recently. Here, we determined the different heat tolerance ability for five selective lines of H. discus hannai by measuring the cardiac performance and Arrhenius breakpoint temperature (ABT). The Red line (RL) and Yangxia line (YL) were determined as the most heat-sensitive and most heat-tolerant line, respectively. Heart rates for RL were significantly lower than those of the YL at the same temperature (p < 0.05). The differentially expressed genes (DEGs), which were enriched in several pathways including cardiac muscle contraction, glutathione metabolism and oxidative phosphorylation, were identified between RL and YL at control temperature (20°C) and heat stress temperature (28.5°C, the ABT of the RL) by RNA-seq method. In the RL, 3370 DEGs were identified between the control and the heat-stress temperature, while only 1351 DEGs were identified in YL between these two temperature tests. Most of these DEGs were enriched in the pathways such as protein processing in endoplasmic reticulum, nucleotide binding and oligomerization domain (NOD) like receptor signaling, and ubiquitin mediated proteolysis. Notably, the most heat-tolerant line YL used an effective heat-protection strategy based on moderate transcriptional changes and regulation on the expression of key genes.

Do heat alerts save lives?

Short-term heat events (e.g. heat waves) and cold events cause more loss of life in Australia than any other weather or climate extreme. They are also, relative to other extremes, easier to predict, exhibit larger spatial scales and thus affect more people, and responses that can reduce the excess mortality associated with them are better understood and more readily actionable. There is evidence that the heat-event alert system introduced in Victoria in 2009, and subsequently enhanced, saves lives. Improving and further enhancing heat-alert systems will reduce the costs, both human and financial, associated with heat events. This paper discusses whether a cold alert system is required, along with the possible reasons why the excess mortality after a hot event is of shorter duration than after a cold event, and why winter mortality typically exceeds summer mortality even for similar temperatures.

Comparative transcriptome analysis provides comprehensive insights into the heat stress response of Marsupenaeus japonicus

The kuruma shrimp Marsupenaeus japonicus is an economically important crustacean that is widely distributed throughout the Indo-West Pacific. However, M. japonicus exhibits relatively poor thermotolerance properties and frequently suffers from mass mortality during the hot summer months in aquaculture systems. Herein, we performed a comparative transcriptome analysis of M. japonicus in response to heat stress, focusing on immune responses, heat shock proteins, antioxidant systems and metabolism alterations under heat stress. The results revealed that M. japonicus generated adaptive responses to maintain physiological homeostasis under heat stress via the transcriptional up-regulation of heat shock proteins and antioxidant enzymes, enhancement of fatty acid metabolism. However, acute and prolonged exposure to heat stress resulted in the continually decreased expression of immune molecules and led to the repression of glycometabolism, the tricarboxylic acid cycle and the respiratory chain. This study provides a systematic overview of the M. japonicus heat stress response and elucidates potential molecular mechanisms underlying this phenomenon and summer mortality syndrome in this species, which is beneficial for proposing effective strategies to address summer mortality syndrome and promote kuruma shrimp production.

Immune response to temperature stress in three bivalve species: Pacific oyster Crassostrea gigas, Mediterranean mussel Mytilus galloprovincialis and mud cockle Katelysia rhytiphora

Summer mortality of some bivalve species is often associated with the change of environmental temperature. This study compares the response of immunological parameters to temperature change in three marine bivalves: Pacific oyster Crassostrea gigas, Mediterranean mussel Mytilus galloprovincialis and mud cockle Katelysia rhytiphora. Each species was exposed to three temperatures, 15 °C, 20 °C and 25 °C for 14 days. The total haemocyte count (THC), phagocytosis, reactive oxygen species (ROS) and the activity of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) were used as indicators to measure the response of each species to different temperatures. The highest temperature (25 °C) significantly increased the THC and phagocysis of haemocytes in all species. The SOD and CAT activities in the haemocytes of M. galloprovincialis and K. rhytiphora rapidly increased with temperature elevation, concomitantly with the increase of ROS ions. In contrast, the increases of ROS and SOD in C. gigas only occurred from 20 °C to 25 °C, suggesting that this intertidal species is more adaptive to different temperature levels. This study indicates that the activities of antioxidant enzymes can reflect the immune response of marine bivalves to thermal stress. Intertidal species such as Pacific oysters have a greater tolerance to thermal stress than subtidal species (e.g. Mediterranean mussel) and demersal species buried in sand (e.g. cockle).

Rapid Detection and Control of Gram-negative Bacterial Pathogens Isolated from Summer Mortality Outbreak Affecting Tilapia Farms

Rapid Detection and Control of Gram-negative Bacterial Pathogens Isolated from Summer Mortality Outbreak Affecting Tilapia Farms

Molecular cloning and expression of the heat shock protein 70 gene in the Kumamoto oyster &lt;i&gt;Crassostrea sikamea&lt;/i&gt;

Episodes of summer mortality of the Kumamoto oyster Crassostrea sikamea are a major problem for its cultivation. Expression of the heat shock protein 70 (HSP70) is induced by various environmental stresses, including heat. We cloned and sequenced hsp70 complementary DNA from C. sikamea to investigate the relationship between hsp70 expression and heat tolerance in this oyster. Quantitative real-time polymerase chain reaction was performed using gill tissue dissected from oysters before and after heat shock for 1 h. The results showed hsp70 expression was faster and greater in oysters cultured at 20–22 °C than at 10–12 °C, and survival was lower among oysters cultured at 20–22 °C than at 10–12 °C. Moreover, heat tolerance was investigated by a 1-h pre-heat treatment, followed by exposure to heat shock conditions 5 days later. Survival was higher and hsp70 expression was notably lower in oysters that received the pre-heat treatment compared with those that did not. We conclude that a pre-heat treatment of only 1 h may be useful for inducing heat tolerance in C. sikamea, and that a low level of hsp70 expression after heat shock is an important index in selecting for high heat tolerance in these oysters.

Characterisation of the Pacific Oyster Microbiome During a Summer Mortality Event.

The Pacific oyster, Crassostrea gigas, is a key commercial species that is cultivated globally. In recent years, disease outbreaks have heavily impacted C. gigas stocks worldwide, with many losses incurred during summer. A number of infectious agents have been associated with these summer mortality events, including viruses (particularly Ostreid herpesvirus 1, OsHV-1) and bacteria; however, cases where no known aetiological agent can be identified are common. In this study, we examined the microbiome of disease-affected and disease-unaffected C. gigas during a 2013-2014 summer mortality event in Port Stephens (Australia) where known oyster pathogens including OsHV-1 were not detected. The adductor muscle microbiomes of 70 C. gigas samples across 12 study sites in the Port Stephens estuary were characterised using 16S rRNA (V1-V3 region) amplicon sequencing, with the aim of comparing the influence of spatial location and disease state on the oyster microbiome. Spatial location was found to be a significant determinant of the disease-affected oyster microbiome. Furthermore, microbiome comparisons between disease states identified a significant increase in rare operational taxonomic units (OTUs) belonging to Vibrio harveyi and an unidentified member of the Vibrio genus in the disease-affected microbiome. This is indicative of a potential role of Vibrio species in oyster disease and supportive of previous culture-based examination of this mortality event.

Canada goose gosling survival of the Atlantic Flyway Resident Population

ABSTRACTGosling losses account for the majority of summer mortality for Canada geese (Branta canadensis), but survival at this stage can be difficult to estimate because of their small size, precocial behavior, and the land cover in which they live. Previous methods of measuring gosling survival often used individual markers, which can bias estimates when not accounting for total brood loss or emigration. We estimated gosling survival of Canada geese in the Atlantic Flyway Resident Population (AFRP) in New Jersey, USA, during 2009–2010 through use of marked parents and young to incorporate total and partial brood losses. The proportion of marked parents who lost their entire brood occurring during the first 3 weeks after hatch and prior to banding was 0.316. Gosling survival that accounted for partial brood loss was 0.461 ± 0.027 (SE), and was most influenced by nest density and the percent agriculture land use within 215 m of the nest site. The gosling survival estimate incorporating total and partial brood losses during this study was 0.315 ± 0.018. Acquiring current reproductive vital rates will assist in understanding the dynamics of recruitment as a function of population size. The above information, in combination with nest survival and annual survival estimates from band recovery and recapture analyses, has been used to inform a population model for Canada geese in the AFRP. © 2018 The Wildlife Society.

Effects of calf predation and nutrition on elk vital rates

ABSTRACTDemographic data indicated a population of elk (Cervus canadensis) in northern New Mexico had reduced juvenile recruitment, resulting in a concern over quality hunting opportunities. Following several years of low calf:female ratios of &lt;25:100, we conducted a 4‐year study from 2009–2012 to identify reasons for poor recruitment and evaluated the role of predation and nutrition in limiting productivity. We captured and fixed ear‐tag radio transmitters to 245 elk calves (126 males, 119 females) to determine cause‐specific mortality and estimate calf survival. During the second half of our study, we implemented a new spring black bear (Ursus americanus) season resulting in higher spring black bear harvest and evaluated response in calf survival. We also quantified herd‐wide nutritional condition and productivity. We estimated percent ingesta‐free body fat (IFBF) and pregnancy rates by sampling 1,808 hunter‐harvested female elk from autumn through winter. The primary cause of summer mortality for calves across all years was black bear predation. Estimates for annual calf survival were greater when spring black bear harvest was moderate to high (0.44–0.47) compared to periods with lower bear harvest (0.33–0.35). For every additional bear harvested in spring, radio‐tagged elk calves were 2.4% more likely to survive the summer. Across years and age classes 82 ± 1% (SE) of females were pregnant. Pregnancy rate was greatest for prime‐aged (2–14 yr) females (88 ± 1%). Our herd‐wide estimate of IFBF for prime‐aged adult female elk was 11.9 ± 0.19% but varied by pregnancy and lactation status. Our results that black bear predation was the primary cause of summer calf mortality and that adult females were in adequate nutritional condition suggested that black bear predation was limiting population productivity. Additionally, calf survival was higher in drought years, the same years when targeted spring black bear harvest was implemented. Our results demonstrated that productivity could be increased by implementing a spring black bear harvest strategy targeted around calving areas and could be applied in other areas experiencing low elk calf survival. © 2018 The Wildlife Society.