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During their winter migration, bald eagles (Haliaeetus leucocephalus) stop at Lake Coeur d'Alene, Idaho to eat spawned kokanee salmon (Oncorhynchus nerka). Long-term data on these migrating bald eagles provide a unique opportunity to investigate their trend from 1974 to 2010. We counted bald eagles during 12 weeks from November through February of each year. They arrived in mid-November, peaked in number in late-December, and departed in January. We recorded the fewest bald eagles, latest arrival dates, and slowest rates of arrival (i.e., linear slope between peak numbers of bald eagles with dates of their first and peak occurrences) during the 1980s. Numbers of bald eagles rebounded during the 2000s, with the most bald eagles, earliest arrival dates, and fastest rate of arrival. To explore trends at a regional scale, we utilized data from the Midwinter Bald Eagle Surveys along with available salmon data. We found that Lake Coeur d'Alene had an average 34% more midwinter numbers of bald eagles and an average 74% less biomass of kokanee salmon during the 2000s than the 1980s. Neighboring Lake Pend Oreille had an average 48% fewer midwinter numbers of bald eagles and an average 58% less biomass of kokanee salmon during the same time period. These results indicate that active management of kokanee salmon may increase bald eagles at Lake Pend Oreille but not necessarily at Lake Coeur d'Alene. Numbers of bald eagles at Lake Coeur d'Alene have been largely influenced by a combination of growing nesting populations and shifting migration patterns.
We estimated hooking and landing success and relative hooking mortality for stream-dwelling trout caught with baited circle and J hooks, J hook dry flies, and treble hook spinners (all hooks barbed). Trout were caught, individually marked, and released for 69 days. Deep-hooking rate was higher for trout captured with baited J hooks (21%) than for spinners (5%), baited circle hooks (4%), and dry flies (1%). Relative mortality rate was higher for trout captured with baited J hooks (25%) and spinners (29%) than for trout captured with baited circle hooks (7%) and dry flies (4%). Deep-hooking was two and six times higher for baited J hooks than baited circle hooks for fish caught actively and passively , respectively. For baited circle hooks, deep-hooking was over three times greater when using an active fishing method (i.e., an active hookset) compared to passive fishing method (no hookset), which conflicts with manufacturer&s recommendations on how circle hooks should be fished. Hooking success (ratio of hook-ups to number of fish strikes) was about one-third lower for baited circle hooks fished both passively and actively compared to other hook types and fishing methods, except for passively-fished baited J hooks. Once hooked, landing success (ratio of fish landed to number of hook-ups) was relatively high for all hook types and fishing methods (range 68–87%). Our results suggest that when bait fishing for trout in streams, circle hook use may reduce deep-hooking and hooking mortality (but also catch rate) regardless of whether anglers fish passively or actively.
We investigated the vertical pattern of foliage retention of Douglas-fir (Pseudotsuga menziesii) in the western Oregon Coast Range where Swiss needle cast, a foliage disease caused by Phaeocryptopus gaeumannii, is causing foliage loss and growth impacts. Swiss needle cast reduced foliage retention more in the upper crown than the lower crown within the epidemic area, which is unusual as foliage diseases usually reduce foliage retention most in the lower crown. We hypothesized that as foliage retention increased across environmental gradients that it would also increase in the upper crown at a greater rate than the lower crown. We randomly selected 72 sites from a population of Douglas-fir plantations in the northwest Oregon Coast Range. We estimated foliage retention from the lower, mid and upper crown of 10 trees per plot. We fitted a two-level hierarchical model with tree and stand level predictors to model changes in foliage retention with changing environmental gradient for foliage in each of three vertical crown positions. We found that the vertical pattern of foliage retention was generally similar throughout the study area with lowest retention in the upper crown, and highest retention in the lower crown. Foliage retention increased with increasing distance from the coast, which is correlated with increased elevation and decreased temperature and site productivity. These findings are consistent with our current understanding of conifer foliage retention. No apparent shift occurs from whole crown to lower crown impacts in our study area as foliage retention increases and approaches normal.
Olympic mudminnow (Novumbra hubbsi) is a small species endemic to western Washington State that inhabits marshy, wetland-type areas with abundant aquatic macrophytes. Because they can be locally abundant and may be the only fish species present, they may have important effects on the aquatic community. However, little is known about their diet under natural conditions. To get a detailed account of their feeding ecology, Olympic mudminnow were sampled from six sites. Three sites were sampled monthly from February to August 2012 and the other three sites were sampled once in June 2012. Gastric lavage was used to collect stomach samples from fish ≥ 40 mm total length (TL). Stomach samples were collected from 477 fish (40–75 mm TL). Olympic mudminnow diet was comprised primarily of aquatic invertebrates. By weight, oligochaetes and chironomid larvae were the predominant prey types but by number, copepods were the predominant prey type. Of the three monthly sample sites, diet overlap between seasons was high at one site, low at another site, and variable at the third site. Diet overlap was generally low between sites. Olympic mudminnow 40–49 mm TL primarily displayed a generalist feeding strategy, whereas larger fish displayed more specialization. A consistent pattern of ontogenetic diet shifts was not apparent. Results of this study and an earlier study indicate Olympic mudminnow consume a wide variety of types and sizes of aquatic invertebrates and their diet can vary widely between sites and seasons.
Psathyrella aquatica was observed fruiting in the Rogue River in southern Oregon in 2005 and described as a new species in 2010. The goals of this study were to determine the ability of P. aquatica to grow and fruit in culture, and to observe morphological characters during sporocarp development in terrestrial as well as aquatic environments. Under conditions similar to that for cultivation of terrestrial species, the underwater mushroom P. aquatica grew in culture and formed sporocarps on woody substrates. In vitro, mature sporocarps of P. aquatica formed on woody substrates in containers subjected to submersion and temporary cooling. While in vitro fruiting under predominantly terrestrial conditions supports the hypothesis that P. aquatica may form terrestrial sporocarps, in natural conditions P. aquatica has been observed fruiting only underwater. Terrestrial search parameters for this rare mushroom can now include cultural characters of the mycelium and morphological characters of sporocarps observed in vitro.
Aerial insectivores have undergone marked population declines in recent decades, including members of the Hirundinidae (swallows), which have long served as sentinels of environmental change. In contrast to other swallow species that breed in North America, we have a poor understanding of most aspects of the basic ecology and life history of the violetgreen swallow (Tachycineta thalassina), a widespread species found throughout the Pacific Northwest. In this study, we investigated the diet composition of violet-green swallow nestlings to document the consumption of food resources by offspring during adult feeding visits. We identified arthropods from 13 taxonomic orders in feeding boluses and found that representation of taxonomic groups was highly uneven and dominated by Diptera and Hemiptera. Although swallows did provision some large prey, the great majority (i.e., 92.6% of 1047) of food items were < 5 mm in length. Feeding boluses collected from the congeneric tree swallow (T. bicolor) at the same study area and during the same time period revealed similar patterns of size and taxonomic representation of diet composition of violet-green nestlings, raising questions as to how these species partition critical resources in areas of sympatry.
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