17 research outputs found
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Meristic Differences in Spawning Populations of American Shad, Alosa sapidissima: Evidence for Homing to Tributaries in the St. John River, New Brunswick
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Niche Breadth: Causes and Consequences for Ecology, Evolution, and Conservation
Niche breadth is a unifying concept spanning diverse aspects of ecology, evolution, and conservation biology. Niche breadth usually refers to the diversity of resources used or environments tolerated by an individual, population, species, or clade. Here we review key research in ecology, evolution, and conservation biology in light of niche breadth. Namely, we explore the role of niche breadth in shaping geographic distributions and species richness from local to landscape scales, how niche breadth evolves and influences lineage diversification, and its use for understanding species invasions, responses to climate change, vulnerability to extinction, and ecosystem functioning. This diverse literature informs a research agenda that identifies focused needs for further progress: testing the hierarchical nature of niche breadth (e.g., of individuals, populations, and species); quantifying correlations in niche breadth among different niche axes and the role of environmental drivers and organismal constraints in generating these correlations; and evaluating the factors that decouple fundamental and realized niches. We describe how this research agenda could help unify disparate subdisciplines and shed light on key questions in ecology, evolution, and conservation
Decline and Recovery of Atlantic Cod (Gadus morhua) Stocks throughout the North Atlantic
Many stocks of Atlantic cod (Gadus morhua) on both sides of the North
Atlantic are currently at much reduced levels of biomass, but this situation
is not in all instances the result of long, continuous decline. Most
Northwest Atlantic stocks declined to low levels during the 1970s, but
increased during the 1980s before declining even more severely during
the late 1980s and early 1990s. Several of these stocks have shown
little recovery despite severe restrictions on directed fishing. Many
stocks in the Northeast Atlantic have experienced sustained increases
and sustained decreases, but generally not in concert. Among-stock
comparisons illustrate that fishing has played a dominant role in the
dynamics of all cod stocks, but variability in climate has contributed
to variability in recruitment, individual growth, and natural mortality.
A cooling event during the last three decades of the twentieth century
contributed to the rapid decline of several stocks in the Northwest
Atlantic, and changes in life-history traits (growth rate, age and size at
maturity) and in the biotic environment (predators and prey) may be
contributing to recovery being slow