Genetics of Century-Old Fish Scales Reveal Population Patterns of Decline

Conservation scientists rarely have the information required to understand changes in abundance over more than a few decades, even for important species like Pacific salmon. Such lack of historical information can underestimate the magnitude of decline for depressed populations. We applied genetic tools to a unique collection of 100‐year‐old salmon scales to reveal declines of 56%–99% in wild sockeye populations across Canada\u27s second largest salmon watershed, the Skeena River. These analyses reveal century‐long declines that are much greater than those based on modern era abundance data, which suggested that only 7 of 13 populations declined over the last five decades. Populations of larger‐bodied fish have declined the most in abundance, likely because of size‐selective commercial fisheries. Our findings illustrate how a deep historical perspective can expand our understanding of past abundances to a time before species incurred significant losses from fishing, and help inform conservation for diminished populations

Minimal residual disease in Myeloma: Application for clinical care and new drug registration

The development of novel agents has transformed the treatment paradigm for multiple myeloma, with minimal residual disease (MRD) negativity now achievable across the entire disease spectrum. Bone marrow–based technologies to assess MRD, including approaches using next-generation flow and next-generation sequencing, have provided real-time clinical tools for the sensitive detection and monitoring of MRD in patients with multiple myeloma. Complementary liquid biopsy–based assays are now quickly progressing with some, such as mass spectrometry methods, being very close to clinical use, while others utilizing nucleic acid–based technologies are still developing and will prove important to further our understanding of the biology of MRD. On the regulatory front, multiple retrospective individual patient and clinical trial level meta-analyses have already shown and will continue to assess the potential of MRD as a surrogate for patient outcome. Given all this progress, it is not surprising that a number of clinicians are now considering using MRD to inform real-world clinical care of patients across the spectrum from smoldering myeloma to relapsed refractory multiple myeloma, with each disease setting presenting key challenges and questions that will need to be addressed through clinical trials. The pace of advances in targeted and immune therapies in multiple myeloma is unprecedented, and novel MRD-driven biomarker strategies are essential to accelerate innovative clinical trials leading to regulatory approval of novel treatments and continued improvement in patient outcomes

Evaluating Relationships between Wild Skeena River Sockeye Salmon Productivity and the Abundance of Spawning Channel Enhanced Sockeye Smolts

The enhancement of salmon populations has long been used to increase the abundance of salmon returning to spawn and/or to be captured in fisheries. However, in some instances enhancement can have adverse impacts on adjacent non-enhanced populations. In Canada\u27s Skeena watershed, smolt-to-adult survival of Babine Lake sockeye from 1962–2002 was inversely related to the abundance of sockeye smolts leaving Babine Lake. This relationship has led to the concern that Babine Lake smolt production, which is primarily enhanced by spawning channels, may depress wild Skeena (Babine and non-Babine) sockeye populations as a result of increased competition between wild and enhanced sockeye smolts as they leave their natal lakes and co-migrate to sea. To test this hypothesis we used data on Skeena sockeye populations and oceanographic conditions to statistically examine the relationship between Skeena sockeye productivity (adult salmon produced per spawner) and an index of Babine Lake enhanced smolt abundance while accounting for the potential influence of early marine conditions. While we had relatively high power to detect large effects, we did not find support for the hypothesis that the productivity of wild Skeena sockeye is inversely related to the abundance of enhanced sockeye smolts leaving Babine Lake in a given year. Importantly, life-time productivity of Skeena sockeye is only partially explained by marine survival, and likely is an unreliable measure of the influence of smolt abundance. Limitations to our analyses, which include: (1) the reliance upon adult salmon produced per spawner (rather than per smolt) as an index of marine survival, and (2) incomplete age structure for most of the populations considered, highlight uncertainties that should be addressed if understanding relationships between wild and enhanced sockeye is a priority in the Skeena

Run-of-River hydropower and salmonids: potential effects and perspective on future research

The spatial footprint of individual run-of-river (RoR) hydropower facilities is smaller than reservoir-storage hydroelectric projects and their impacts to aquatic ecosystems are often assumed to be negligible. However, these effects are poorly understood, especially for salmonids whose freshwater habitat often overlaps with RoR hydropower potential. Flow regulation for RoR hydropower is unique in how it influences the seasonality and magnitude of flow diversion, and because low-head dams can be overtopped at high flows. Based on a review of the primary literature, we identified three pathways of effects by which RoR hydropower may influence salmonids: reduction of flow, presence of low-head dams impounding rivers, and anthropogenic flow fluctuations. We synthesized empirical evidence of effects of RoR hydropower on river ecosystems from 31 papers, of which only ten explicitly considered salmonids. We identified key research gaps including impacts of extended low flow periods, anthropogenic flow fluctuations, and cumulative effects of multiple RoR projects. Filling these gaps is necessary to help manage and conserve salmonid populations in the face of the growing global demand for small-scale hydropower.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Data from: Allee effects may slow the spread of parasites in a coastal marine ecosystem

Allee effects are thought to mediate the dynamics of population colonization, particularly for invasive species. However, Allee effects acting on parasites have rarely been considered in the analogous process of infectious disease establishment and spread. We studied the colonization of uninfected wild juvenile Pacific salmon populations by ectoparasitic salmon lice (Lepeophtheirus salmonis) over four years. From a dataset of 67,896 fish, we observed 88 occurrences of pre-copular pair formation among 1258 pre-adult female and 611 adult male lice. The probability of pair formation was dependent on the local abundance of lice, but this mate limitation is likely offset somewhat by mate-searching dispersal of males among host fish. A mathematical model of macroparasite population dynamics that incorporates the empirical results suggests a high likelihood of a demographic Allee effect, which can cause the colonizing parasite populations to die out. These results may provide the first empirical evidence for Allee effects in a macroparasite. Furthermore, the data give a rare detailed view of Allee effects in colonization dynamics and suggest that Allee effects may dampen the spread of parasites in a coastal marine ecosystem

Wild Skeena lake sockeye Conservation Units (CU) and Babine Lake sockeye run-timing groups used in the analyses (CU/group).

<p>*The number of stock-recruitment pairs, age-samples, and age-years are shared among the 3 wild Babine groups.</p><p>Legend: “Stock-recruit” is the total number of stock-recruitment pairs available for each CU/group between 1960 and 2000 brood years, “First/last year” is the first and last brood year of the stock-recruit time series for each CU/group used in the analyses, “Age-samples” is the total number of adult age samples for the CU/group, and “Age-years” is the number of years where age data was available.</p

Multi-model averaged parameter estimates and unconditional standard errors (SE) of parameters in the set of hypotheses considered.

<p>Legend: Productivity (log_e[recruits/spawner]) at low spawner abundance is <i>α</i>, and the variables are: enhanced Babine smolt abundance at the full Skeena (Sm(f)) and Babine Lake (Sm(b)) scale, sea surface temperature (SST), and an interaction between the two (x). All parameters were estimated from a dataset in standard deviation units (SDU) to permit meaningful comparisons because the independent variables are on different numerical scales. For example, the −0.159 parameter estimate for SST means that a 1 SDU increase in SST results in an decrease of 0.159 log_e[recruits/spawner] or 0.85 recruits/spawner.</p

Relationship between sockeye smolt-to-adult survival and smolt abundance.

<p>Legend: Aggregate Babine (i.e., wild and enhanced) sockeye smolt-to-adult survival as a function of smolt abundance (the total number of out-migrating sockeye smolts in a given year between 1962–2002). Line is the best-fit relationship based on a nonlinear least-squares model fit (y = 7.4exp[−0.01*x], <i>p</i> = 0.0013).</p

Statistical power to detect an effect of channel-enhanced sockeye smolt abundance.

<p>Legend: Power is the probability of correctly detecting some specified effect size at α = 0.05) to detect an effect of Babine smolt abundance on wild Skeena lake sockeye Conservation Units (CU). The “smolt effect” is the reduction in wild Skeena lake sockeye CU productivity due to an increase in smolt abundance from 66 to 100 million out-migrating smolts, and the red line is the “smolt effect” estimated from the relationship between Babine smolt-to-adult survival and out-migrating smolt abundance from 1962–2002 (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095718#pone-0095718-g002" target="_blank">Figure 2</a>).</p