Dan Kehler

Parks Canada

Impacts from a changing climate, in particular sea-level rise, will be most acutely felt on small oceanic islands. A common configuration of mid-latitude islands is the sandy barrier island. Sable Island, Nova Scotia, Canada is a vegetated sand island near the shelf edge, 160 km from the nearest point of land, that is morphologically similar to a b...

Universities are offering more online courses in ecological restoration to meet the growing demand for practitioners in this field. Online courses have the potential to contribute to this nuanced discipline by creating an environment in which learners from various backgrounds and locations can co-create knowledge. Unfortunately, online courses are...

Sound is used by a variety of marine taxa for feeding, reproduction, navigation and predator avoidance and therefore alterations to the soundscape from industrial noise have the potential to negatively affect an animal's fitness. Furthermore, responses to industrial noise would also have the potential to negatively influence commercial fishing inte...

Recent advances in the ability to quantify longitudinal connectivity of riverine systems is enabling a better understanding of how connectivity affects fish assemblages. However, the role of connectivity relative to other factors, such as land use, in structuring biological assemblages is just emerging. We assessed the relevance of a structural con...

Aquatic connectivity is an ecological process that is impacted by anthropogenic activity and has been implicated in the decline of many aquatic species. This has lead to the development of numerous theoretical applications to evaluate connectivity in river systems and optimize barrier restoration. Such tools are attractive as they can be less depen...

Anthropogenic barriers to fish passage, such as culverts and dams, are major factors impeding the persistence and recovery of aquatic species. Considerable work has focused on mitigating these impacts; however, activities associated with measuring and restoring connectivity of aquatic ecosystems often face challenges in determining the passability...

The effects on benthic macroinvertebrate communities of simulated degradation of streams enabled evaluation of the effects of starting condition, type of degradation, and biota descriptor on the type 1 and type 2 error rates of bioassessment. Benthic macroinvertebrate communities from five reference streams in the Fraser River basin (British Columb...

Despite heightened levels of protection, impacts of river fragmentation are widespread in Canada's National Parks. Fragmentation associated with dams and culverts is a pervasive stressor that impacts Species at Risk and/or culturally important species such as Atlantic salmon and American eel. While this ecological problem is tractable and efforts a...

Habitat connectivity has one of the most significant effects on the persistence and/or recovery of aquatic species. The modification of stream barriers is a critical step towards the reconnection of movement corridors for fish species. One important aspect in the improvement of stream barriers is an understanding of how barriers affect the movement...

Barriers (culverts and dams) can impede fish passage and affect the overall habitat connectivity of rivers. However, a challenge lies in how to conceptualize and adequately measure passability at barriers. We hypothesize that estimates of barrier and watershed connectivity are dependent on assumptions about the nature of passability, and how it is...

Landscape composition and configuration, often termed as habitat loss and fragmentation, are predicted to reduce species population viability, partly due to the restriction of movement in the landscape. Unfortunately, measuring the effects of habitat loss and fragmentation on functional connectivity is challenging because these variables are confou...

Habitat connectivity is a central factor in shaping aquatic biological communities, but few tools exist to describe and quantify this attribute at a network scale in riverine systems. Here, we develop a new index to quantify longitudinal connectivity of river networks based on the expected probability of an organism being able to move freely betwee...

Reliable estimates of population size are critical for fisheries management and for testing ecological hypotheses but can be expensive and time consuming to obtain. Sampling methodologies have been developed to obviate complete enumeration, but their effectiveness can be limited by logistical constraints. A posteriori sampling from digital video re...

The authors of the critiqued shark articles describe and defend their use and analysis of the data sets and conclude that their results are robust and their conclusions are balanced.

Estimating parameters for population-dynamics models is a critical com-ponent in assessing extinction probabilities of populations. For many individual populations, key parameters will be poorly defined, and meta-analysis would provide a basis for esti-mating the parameters. Here, we introduce meta-analytical techniques to estimate the max-imum rep...

Overexploitation threatens the future of many large vertebrates. In the ocean, tunas and sea turtles are current conservation concerns because of this intense pressure. The status of most shark species, in contrast, remains uncertain. Using the largest data set in the Northwest Atlantic, we show rapid large declines in large coastal and oceanic sha...

We investigated the consequences of measurement errors in spawner abundance on the estimation of α̃, the maximum lifetime reproductive rate, in the Ricker spawner-recruit model. This rate is equivalent to the slope at the origin for the Ricker model, which is crucial for the estimation of management reference points. Simulation results indicate tha...

The usefulness of Bayesian analysis depends in great part on specifying appropriate prior distributions. In this article, we investigate three quantitative techniques for obtaining a prior distribution for steepness, a critical parameter in fisheries management. These techniques were developed in the context of a risk assessment of a power plant's...

SUMMARY The purpose of this paper is to investigate all available U.S. and Canadian observer and logbook data to detect trends in abundance for pelagic and large coastal shark species in the Northwest Atlantic. We found that it was very difficult to obtain long terms trends from a combined analysis of the U.S. and Canadian observer data sets becaus...

We develop a simple theoretical model of yield and spawning stock biomass per recruit for the American sea scallop (Placopecten magellanicus), which appears to have high indirect fishing mortality when harvested with dredges, i.e., mortality caused by the act of fishing that does not result in landings. The age at and degree to which individuals ar...

We investigated the effect of spatial isolation on the incidence of a fungivorous forest beetle in continuous and fragmented forests at three spatial scales, while controlling for confounding variables, such as patch size and quality. Isolation was measured using nearest-neighbour distances and we compared the usefulness of measuring multiple patch...