Population Dynamics and Angler Exploitation of the Unique Muskellunge Population in Shoepack Lake, Voyageurs National Park, Minnesota

A unique population of muskellunge Esox masquinongy inhabits Shoepack Lake in Voyageurs National Park, Minnesota. Little is known about its status, dynamics, and angler exploitation, and there is concern for the long-term viability of this population. We used intensive sampling and mark–recapture methods to quantify abundance, survival, growth, condition, age at maturity and fecundity and angler surveys to quantify angler pressure, catch rates, and exploitation. During our study, heavy rain washed out a dam constructed by beavers Castor canadensis which regulates the water level at the lake outlet, resulting in a nearly 50% reduction in surface area. We estimated a population size of 1,120 adult fish at the beginning of the study. No immediate reduction in population size was detected in response to the loss of lake area, although there was a gradual, but significant, decline in population size over the 2-year study. Adults grew less than 50 mm per year, and relative weight (W r) averaged roughly 80. Anglers were successful in catching, on average, two fish during a full day of angling, but harvest was negligible. Shoepack Lake muskellunge exhibit much slower growth rates and lower condition, but much higher densities and angler catch per unit effort (CPUE), than other muskellunge populations. The unique nature, limited distribution, and location of this population in a national park require special consideration for management. The results of this study provide the basis for assessing the long-term viability of the Shoepack Lake muskellunge population through simulations of long-term population dynamics and genetically effective population size

Factors affecting survival in Mediterranean populations of the Eurasian eagle owl

The survival rate is a key parameter for population management and the monitoring of populations. Thus, an analysis of survival rate variations and the factors influencing the same is essential for understanding population dynamics. Here, we study the factors determining the survival and the causes of mortality of the Eurasian eagle owl (Bubo bubo) in two Spanish Mediterranean populations (Murcia and Seville) where the species has a high population density and breeding success; yet its survival rates and the factors that affect them are unknown. Between 2003 and 2010, 63 breeding owls were captured and radio-tracked. Three monthly (quarterly) survival rates were estimated using known-fate models in the program MARK. The mean overall annual survival rate was 0.776 (95 % CI: 0.677, 0.875). We observed survival differences between sexes, and between the breeding and non-breeding periods, although no overwhelming support was found for any particular model. We concluded that (i) females have a lower survival rate than males, probably due to their larger home ranges, which increase the risk of mortality; (ii) the survival rates of both sexes were lower during the non-breeding period; and (iii) the causes of mortality differed significantly between the two populations, gunshot being the main cause in Seville and electrocution in Murcia.Peer Reviewe

Evaluating vital rate contributions to greater sage-grouse population dynamics to inform conservation

Species conservation efforts often use short‐term studies that fail to identify the vital rates that contribute most to population growth. Although the greater sage‐grouse (Centrocercus urophasianus; sage‐grouse) is a candidate for protection under the U.S. Endangered Species Act, and is sometimes referred to as an umbrella species in the sagebrush (Artemisia spp.) biome of western North America, the failure of proposed management strategies to focus on key vital rates that may contribute most to achieving population stability remains problematic for sustainable conservation. To address this dilemma, we performed both prospective and retrospective perturbation analyses of a life cycle model based on a 12‐yr study that encompassed nearly all sage‐grouse vital rates. To validate our population models, we compared estimates of annual finite population growth rates (λ) from our female‐based life cycle models to those attained from male‐based lek counts. Post‐fledging (i.e., after second year, second year, and juvenile) female survival parameters contributed most to past variation in λ during our study and had the greatest potential to change λ in the future, indicating these vital rates as important determinants of sage‐grouse population dynamics. In addition, annual estimates of λ from female‐based life cycle models and male‐based lek data were similar, providing the most rigorous evidence to date that lek counts of males can serve as a valid index of sage‐grouse population change. Our comparison of fixed and mixed statistical models for evaluating temporal variation in nest survival and initiation suggest that conservation planners use caution when evaluating short‐term nesting studies and using associated fixed‐effect results to develop conservation objectives. In addition, our findings indicated that greater attention should be paid to those factors affecting sage‐grouse post‐fledging females. Our approach demonstrates the need for more long‐term studies of species vital rates across the life cycle. Such studies should address the decoupling of sampling variation from underlying process (co)variation in vital rates, identification of how such variation drives population dynamics, and how decision makers can use this information to re‐direct conservation efforts to address the most limiting points in the life cycle for a given population.Peer reviewedNatural Resource Ecology and Managemen

Nature’s nations: the shared conservation history of Canada and the USA

Historians often study the history of conservation within the confines of national borders, concentrating on the bureaucratic and political manifestations of policy within individual governments. Even studies of the popular expression of conservationist ideas are generally limited to the national or sub-national (province, state, etc.) scale. This paper suggests that conservationist discourse, policy and practice in Canada and the USA were the products of a significant cross-border movement of ideas and initiatives derived from common European sources. In addition, the historical development of common approaches to conservation in North America suggests, contrary to common assumptions, that Canada did not always lag behind the USA in terms of policy innovation. The basic tenets of conservation (i.e. state control over resource, class-based disdain for subsistence hunters and utilitarian approaches to resource management) have instead developed at similar time periods and along parallel ideological paths in Canada and the USA