South Pacific humpback whales were devastated by commercial whaling in their Antarctic feeding areas during the 20th century. Understanding migratory connections and current abundance of these isolated breeding stocks is crucial for the allocation of historical Antarctic catches in population dynamic models used to assess current recovery. However, only a...
Animal weapons are thought to have evolved to compete for reproductive opportunities within a species. Across the diverse weapon-bearing taxa, several evolutionary trends have emerged: (1) increasing complexity and relative size across ontogeny, (2) sexual dimorphism, and (3) higher levels of random deviations from symmetry (i.e., fluctuating asymmetry) than non-weaponized...
Hatcheries whose purpose is to provide for a recreational fishery must minimize impacts on wild fishes. Management to reduce hatchery and wild interactions is especially important on river systems that contain Endangered Species Act (ESA) listed species. I examined adult hatchery summer steelhead, Oncorhynchus mykiss, behavior, current management and a...
Longitudinal patterns of fish and benthic invertebrate distribution and
habitat use were similar in Thomas Creek, Oregon but clarity of these patterns
differed. I studied fish and aquatic invertebrates simultaneously, at multiple
scales, and used multivariate statistical techniques to compare responses to the
same environmental conditions. Both types of organisms...
Riparian areas are eco-tones where aquatically- and terrestrially-derived insect biomass is exchanged between habitats, presenting consumers with new sources of energy, and resulting in a reciprocal subsidy. The relative contribution of energy exchange and the
resulting impacts on vertebrate riparian consumers, such as fish or birds, remains poorly understood. We...
This study examined features of deep pool (>0.8 m mean depth) used by
adult summer steelhead in Steamboat Creek (1991-1992). Steamboat Creek had
a heterogenous thermal profile, with some segments exceeding preferred
temperature of steelhead. Deep pools were scarce (4% of the total habitat units)
and 39% of them were...
The West Fork Smith River, a 69 km2 watershed in the Coast Range of Oregon, is prone to short periods of very high water temperature in mid-summer due to a combination of human and natural influences. In the summers of 2003 and 2004 more than 400 juvenile coho salmon regularly...
Ecologists have studied the responses of pelagic ecosystems
to varying levels of nutrient loading and fish predation on many
different scales ranging from small experimental enclosures to
whole lake systems. There are recurring patterns of response to
these two variables, which are generally predictable on the basis
of biogeographic, behavioral,...
I studied the occurrence of two sympatric morphs of arctic charr, Salvelinus
alpinus (L.) in Vatnshlidarvatn, a small shallow lake in NW Iceland. The arctic charr
were subjectively distinguished by colour and appearance as brown morph or silver
morph, and measured for morphological and life history characters. The study
revealed...
The National Park Service has a dual mission of providing public access to exceptional natural resources, but in a manner such that these resources are left “unimpaired for the enjoyment of future generations.” Human activities in parks undoubtedly affect wildlife, but the degree to which such activities cause impairment is...