Dataset Information

Evaluation of harvest and information needs for North American sea ducks.

ABSTRACT: Wildlife managers routinely seek to establish sustainable limits of sport harvest or other regulated forms of take while confronted with considerable uncertainty. A growing body of ecological research focuses on methods to describe and account for uncertainty in management decision-making and to prioritize research and monitoring investments to reduce the most influential uncertainties. We used simulation methods incorporating measures of demographic uncertainty to evaluate risk of overharvest and prioritize information needs for North American sea ducks (Tribe Mergini). Sea ducks are popular game birds in North America, yet they are poorly monitored and their population dynamics are poorly understood relative to other North American waterfowl. There have been few attempts to assess the sustainability of harvest of North American sea ducks, and no formal harvest strategy exists in the U.S. or Canada to guide management. The popularity of sea duck hunting, extended hunting opportunity for some populations (i.e., special seasons and/or bag limits), and population declines have led to concern about potential overharvest. We used Monte Carlo simulation to contrast estimates of allowable harvest and observed harvest and assess risk of overharvest for 7 populations of North American sea ducks: the American subspecies of common eider (Somateria mollissima dresseri), eastern and western populations of black scoter (Melanitta americana) and surf scoter (M. perspicillata), and continental populations of white-winged scoter (M. fusca) and long-tailed duck (Clangula hyemalis). We combined information from empirical studies and the opinions of experts through formal elicitation to create probability distributions reflecting uncertainty in the individual demographic parameters used in this assessment. Estimates of maximum growth (rmax), and therefore of allowable harvest, were highly uncertain for all populations. Long-tailed duck and American common eider appeared to be at high risk of overharvest (i.e., observed harvest < allowable harvest in 5-7% and 19-26% of simulations, respectively depending on the functional form of density dependence), whereas the other populations appeared to be at moderate risk to low risk (observed harvest < allowable harvest in 22-68% of simulations, again conditional on the form of density dependence). We also evaluated the sensitivity of the difference between allowable and observed harvest estimates to uncertainty in individual demographic parameters to prioritize information needs. We found that uncertainty in overall fecundity had more influence on comparisons of allowable and observed harvest than adult survival or observed harvest for all species except long-tailed duck. Although adult survival was characterized by less uncertainty than individual components of fecundity, it was identified as a high priority information need given the sensitivity of growth rate and allowable harvest to this parameter. Uncertainty about population size was influential in the comparison of observed and allowable harvest for 5 of the 6 populations where it factored into the assessment. While this assessment highlights a high degree of uncertainty in allowable harvest, it provides a framework for integration of improved data from future research and monitoring. It could also serve as the basis for harvest strategy development as management objectives and regulatory alternatives are specified by the management community.

SUBMITTER: Koneff MD

PROVIDER: S-EPMC5395144 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Evaluation of harvest and information needs for North American sea ducks.

Koneff Mark D MD Zimmerman Guthrie S GS Dwyer Chris P CP Fleming Kathleen K KK Padding Paul I PI Devers Patrick K PK Johnson Fred A FA Runge Michael C MC Roberts Anthony J AJ

PloS one 20170418 4

Wildlife managers routinely seek to establish sustainable limits of sport harvest or other regulated forms of take while confronted with considerable uncertainty. A growing body of ecological research focuses on methods to describe and account for uncertainty in management decision-making and to prioritize research and monitoring investments to reduce the most influential uncertainties. We used simulation methods incorporating measures of demographic uncertainty to evaluate risk of overharvest a ...[more]

PMID: 28419113

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Project description:Density dependence, population regulation, and variability in population size are fundamental population processes, the manifestation and interrelationships of which are affected by environmental variability. However, there are surprisingly few empirical studies that distinguish the effect of environmental variability from the effects of population processes. We took advantage of a unique system, in which populations of the same duck species or close ecological counterparts live in highly variable (north American prairies) and in stable (north European lakes) environments, to distinguish the relative contributions of environmental variability (measured as between-year fluctuations in wetland numbers) and intraspecific interactions (density dependence) in driving population dynamics. We tested whether populations living in stable environments (in northern Europe) were more strongly governed by density dependence than populations living in variable environments (in North America). We also addressed whether relative population dynamical responses to environmental variability versus density corresponded to differences in life history strategies between dabbling (relatively "fast species" and governed by environmental variability) and diving (relatively "slow species" and governed by density) ducks. As expected, the variance component of population fluctuations caused by changes in breeding environments was greater in North America than in Europe. Contrary to expectations, however, populations in more stable environments were not less variable nor clearly more strongly density dependent than populations in highly variable environments. Also, contrary to expectations, populations of diving ducks were neither more stable nor stronger density dependent than populations of dabbling ducks, and the effect of environmental variability on population dynamics was greater in diving than in dabbling ducks. In general, irrespective of continent and species life history, environmental variability contributed more to variation in species abundances than did density. Our findings underscore the need for more studies on populations of the same species in different environments to verify the generality of current explanations about population dynamics and its association with species life history.

Project description:ImportanceThere are few population-level studies on ophthalmic conditions and services among North American Native individuals.ObjectiveTo evaluate whether disparities in ophthalmic conditions and services exist between North American Native individuals and non-Hispanic White individuals in the US.Design, setting, and participantsThis cross-sectional study used 100% Medicare fee-for-service (MFFS) enrollment data from the Vision and Eye Health Surveillance System (VEHSS) to examine ophthalmic conditions and service use in North American Native individuals and non-Hispanic White individuals in the US. In this study North American Native individuals included those who identified as American Indian, Native Alaskan, Native Hawaiian, and Pacific Islander. Data were analyzed from August 2020 to April 2021.InterventionsClaims and sociodemographic characteristics were extracted and means computed for categories of ophthalmic conditions and select ophthalmic services. Ophthalmic conditions and services were defined in the VEHSS using International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Clinical Modification (ICD-10-CM) codes. Logistic regression was used to model differences between age-adjusted mean ophthalmic condition and service claim rates among North American Native individuals and non-Hispanic White individuals for each age cohort. Matching ophthalmic condition claim rates and ophthalmic service claim rates was performed to examine disparities by racial group.Main outcomes and measuresMean age-adjusted claim rates for ophthalmic conditions and services among North American Native individuals vs non-Hispanic White individuals per 100 persons.ResultsClaims were identified for 177 100 Native American Native individuals and 24 438 000 non-Hispanic White individuals. In 16 of 17 ophthalmic condition categories and 6 of 9 service categories, North American Native individuals had significantly different claim rates from non-Hispanic White individuals. There were higher ophthalmic condition claim rates but lower service claim rates for North American Native individuals (vs non-Hispanic White individuals) for refractive errors (ophthalmic condition, 17.2 vs 11.1; service, 48.3 vs 49.6, respectively; P < .001); blindness and low vision (ophthalmic condition, 1.48 vs 0.75: service, 19.2 vs 20.1, respectively; P < .001); injury, burns, and surgical complications (ophthalmic condition, 1.8 vs 1.7; service, 19.2 vs 20.1, respectively; P < .001); and orbital and external disease (ophthalmic condition, 15.7 vs 13.3; service, 48.3 vs 49.6, respectively; P < .001). For diabetic eye diseases, North American Native individuals had higher ophthalmic condition claim rates (5.22 vs 2.20) but no difference in service claim rates (14.4 vs 14.8; P = .26) compared with non-Hispanic White individuals.Conclusions and relevanceIn this cross-sectional study, North American Native individuals had higher prevalence of ophthalmic conditions but no corresponding increase in services (treatment for most ophthalmic conditions) compared with non-Hispanic White individuals. These results suggest worse eye health and higher unmet eyecare needs for North American Native individuals with MFFS coverage compared with non-Hispanic White individuals with MFFS coverage.

Dataset Information

Evaluation of harvest and information needs for North American sea ducks.

Publications

Evaluation of harvest and information needs for North American sea ducks.

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