Assessment of harbor seal predation on adult salmonids in a Pacific Northwest estuary.

The populations of many native species have increased or expanded in distribution in recent decades, sometimes with negative consequences to sympatric native species that are rarer or less adaptable to anthropogenic changes to the environment. An example of this phenomenon from the Pacific Northwest is predation by locally abundant pinnipeds (seals and sea lions) on threatened, endangered, or otherwise depleted salmonid (Oncorhynchus spp.) populations. We used survey sampling methodology, acoustic telemetry, and molecular genetics to quantify the amount of harbor seal (Phoca vitulina) predation on a depressed run of coho salmon (O. kisutch) and to determine whether some seals consumed a disproportionately higher number of salmonids than others. Based on a probability sample totaling 759.5 h of observation, we estimated that seals consumed 1161 adult salmonids (95% CI = 503-1818 salmonids) during daylight hours over an 18.9-km estuarine study area in Oregon during an 84-d period in fall 2002. Simultaneous tracking of 56 seals via an acoustic telemetry array indicated that a small proportion of marked seals (12.5%) exhibited behavior that was consistent with specialization on salmonids. These seals spent the majority of their time in the riverine portion of the study area and did so disproportionately more at night than day. Genetic analysis of 116 salmonid structures recovered from 11 seal fecal samples suggested that coho salmon accounted for approximately one-half of total salmonid consumption. Though subject to considerable uncertainty, the combined results lead us to infer that seals consumed 21% (range = 3-63%) of the estimated prespawning population of coho salmon. We speculate that the majority of the predation occurred upriver, at night, and was done by a relatively small proportion of the local seal population. Understanding the extent and nature of pinniped predation can provide important inputs into risk assessments and other modeling efforts designed to aid the conservation and recovery of salmonids in the Pacific Northwest. Such understanding may also help inform management actions designed to reduce the impact of pinniped predation on salmonids, which potentially range from short-term lethal removal programs to long-term ecosystem restoration and protection efforts.     

Regional Turnover and Fluctuation in Populations of Five Plants Confined to Serpentine Seeps

Abstract: Spatial patterns in population turnover were analyzed for five plant species confined to a patchy and isolated habitat, serpentine seeps: annuals Helianthus exilis and Mimulus nudatus and perennials Senecio clevelandii , Astragalus clevelandii , and Delphinium uliginosum . A 3-year survey showed that, over a preceding 15-year period, 32 of 132 known populations in a 4200-ha area disappeared, and 65 new populations appeared. Populations that disappeared were significantly more isolated from conspecific populations than were surviving populations. Populations that disappeared were also marginally significantly closer to human-caused disturbances than were populations that survived. Vacant sites in which new populations appeared were significantly less isolated from conspecific populations than sites remaining vacant. Spatial patterns in population density were analyzed for three of the species for 3 years at 50 sites in a 20 × 40 km region. From 1997 to 1998, population densities of each species changed synchronously throughout the region. From 1998 to 1999, one species (   Mimulus nudatus ) again showed synchrony, and populations of the other two species (   Helianthus exilis , Delphinium uliginosum ) remained asynchronous and spatially uncorrelated. The five species we studied all appear to be persisting well at the regional scale, despite recent disturbance to the study region. These results suggest that for rare plants in isolated habitats, the spatial configuration of populations may have an important influence on local population persistence.     

Blood-based biomarkers in the maternal circulation associated with fetal growth restriction

Fetal growth restriction (FGR) is associated with threefold to fourfold increased risk of stillbirth. Identifying FGR, through its commonly used surrogate—the small-for-gestational-age (SGA, estimated fetal weight and/or abdominal circumference <10th centile) fetus—and instituting fetal surveillance and timely delivery decrease stillbirth risk. Methods available to clinicians for antenatal identification of SGA fetuses have surprisingly poor sensitivity. About 80% of cases remain undetected. Measuring the symphysis-fundal height detects only 20% of SGA fetuses, and even universal third trimester ultrasound detects, at best, 57% of those born SGA. There is an urgent need to find better ways to identify this at-risk cohort. This review summarises efforts to identify molecular biomarkers (proteins, metabolites, or ribonucleic acids) that could be used to better predict FGR. Most studies examining potential biomarkers to date have utilised case-control study designs without proceeding to validation in independent cohorts. To develop a robust test for FGR, large prospective studies are required with a priori validation plans and cohorts. Given that current clinical care detects 20% of SGA fetuses, even a screening test with ≥60% sensitivity at 90% specificity could be clinically useful, if developed. This may be an achievable aspiration. If discovered, such a test may decrease stillbirth.     

Crayfish Use of Trash Versus Natural Cover in Incised, Sand-Bed Streams

Historic land use changes and subsequent river channelization created deeply incised, unstable stream channels largely devoid of natural cover throughout the Yazoo River basin, Mississippi, USA. Large trash (e.g., televisions, toilets, car parts) dumped in streams provided shelter for some aquatic fauna. To determine whether trash served as a surrogate for natural cover, I examined crayfish use of both cover types. I sampled crayfishes by kick-seining 2 × 1-m plots in three cover classes: trash, natural cover, and no cover. I captured 415 crayfishes from 136 of the 294 plots. Most crayfishes were in natural cover (253), followed by trash (154), and no-cover (8) plots. Trash use varied by crayfish genus and size. Frequencies of all size classes of Procambarus and of the smallest Cambarus were higher in natural cover than trash. Many of the smallest individuals were found in live root mats. As Cambarus and Orconectes grew, they shifted more toward trash, and the largest Orconectes size class was significantly more abundant than expected in trash. Trash served as “artificial reefs,” providing cover for crayfishes and other fauna, but functioned differently than the remaining natural cover. The results confirmed that stream substrate did not provide adequate instream cover for crayfishes in the study area and suggested that high-quality natural cover for large crayfishes was in short supply, at least for some species. Land management that provides for abundant, ongoing input and retention of complex cover, such as trees and live roots, to stream channels should be beneficial for crayfish assemblages.