As with other species, frequency-dependent selection during reproduction has long been proposed as an important mechanism in maintaining alternative male reproductive phenotypes in Pacific salmon ( Oncorhynchus spp.). Jack salmon mature one year earlier than the youngest females in a population and are much smaller than older “adult” males. We tested the hypothesis that mating success of both phenotypes is consistent with the frequency-dependent selection model. By holding male density constant and varying the frequency of adults and jacks in eight separate breeding groups, we found that adult male access to females, participation in spawning events, and adult-to-fry reproductive success increased with their decreasing frequency in a breeding group. Jacks exhibited the same pattern (increasing success with decreasing frequency), although the relationships were not as strong as for adults. Overall, jack and adult males mated with a similar number of females, but jacks sired only 20% of all offspring. Observational data suggested that adult males benefited from sperm precedence associated with their ability to court females and enter the nest first at the time of spawning. Our work provides the first experimental evidence of frequency-dependent selection during mating in the family Salmonidae.

Until recently, research on mortality of anadromous fishes in the marine environment was largely limited to estimates of total mortality and association with group characteristics or the environment. Advances in sonic transmitter technology now allow estimates of survival in discrete marine habitats, yielding important information on species of conservation concern. Previous telemetry studies of steelhead Oncorhynchus mykiss smolts in Puget Sound, Washington, USA indicated that approx. 80% of fish entering marine waters did not survive to the Pacific Ocean. The present study re-examined data from previous research and incorporated data from additional Puget Sound populations (n = 7 wild and 6 hatchery populations) tagged during the same period (2006−2009) for a comprehensive analysis of steelhead early marine survival. We used mark-recapture models to examine the effects of several factors on smolt survival and to identify areas of Puget Sound where mortality rates were highest. Wild smolts had higher survival probabilities in general than hatchery smolts, with exceptions, and wild smolts released in early April and late May had a higher probability of survival than those released in early and mid-May. Steelhead smolts suffered greater instantaneous mortality rates in the central region of Puget Sound and from the north end of Hood Canal through Admiralty Inlet than in other monitored migration segments. Early marine survival rates were low (16.0 and 11.4% for wild and hatchery populations, respectively) and consistent among wild populations, indicating a common rather than watershed-specific mortality source. With segment-specific survival information we can begin to identify locations associated with high rates of mortality, and identify the mechanisms responsible.

The depressed status of Puget Sound populations of steelhead Oncorhynchus mykiss contrasts with the healthier condition of those along the coast of Washington and suggests that there is substantial smolt mortality during the migration through Puget Sound to the Pacific Ocean. Acoustic telemetry transmitters and stationary receivers were used to investigate the survival, migration timing, and migratory behavior of 159 steelhead smolts in 2006 and 187 smolts in 2007 from four Hood Canal (part of Puget Sound) streams and one stream flowing into the Strait of Juan de Fuca. The estimated population‐specific survival rates for wild and hatchery smolts from the river mouths to the northern end of Hood Canal (28.1–75.4 km) ranged from 55% to 86% in 2006 and from 62% to 84% in 2007. Survival was much lower from the northern end of Hood Canal to the Strait of Juan de Fuca (135 km) in 2006 (23–49%) and could not be reliably measured in 2007. Travel rates through Hood Canal (8–10 km/d) were significantly lower than those estimated as the fish migrated through northern Puget Sound and the Strait of Juan de Fuca (26–28 km/d), while the mortality rates per unit of distance traveled were very similar in the two segments. The high daily mortality rates estimated during the early marine phase of the steelhead life cycle (2.7%/d) suggest that mortality rates decrease substantially after steelhead enter the Pacific Ocean.

Insect parasitoids, and the arthropod hosts they consume during development, are important ecological players in almost all environments across the globe. As ectothermic organisms, both parasitoid and host are strongly impacted by environmental temperature. If thermal tolerances differ between host insect and parasitoid, then the outcome of their interaction will be determined by the ambient temperature. As mean temperatures continue to rise and extreme temperatures become more frequent, we must determine the effect of high temperature stress on host–parasitoid systems to predict how they will fare in the face of climate change. The majority of studies conducted on host–parasitoid systems focus on either performance under constant temperature or a fixed metric of thermal tolerance (CTmax) for individual organisms. However, performance at constant temperatures is not predictive of performance under ecologically relevant, fluctuating temperatures and measurements of thermal thresholds provide little information regarding the effects of temperature throughout development. We address this by testing the effects of increasing mean temperature in both constant and fluctuating (±10°C) environments throughout development on the performance of the parasitoid wasp Cotesia congregata and its lepidopteran larval host, Manduca sexta. The growth of M. sexta was influenced by mean temperature, diurnal fluctuations and parasitization status. Caterpillar growth rate increased with increasing mean temperature, but decreased in response to diurnal fluctuations and parasitization by C. congregata wasps. Wasp survival decreased with increasing mean temperature and with diurnal fluctuations. The effect of diurnal fluctuations was stronger at higher mean temperatures. Diurnal fluctuations at our highest mean temperature treatment (30 ± 10°C) resulted in complete wasp mortality, and parasitized hosts displayed abnormal physiology, wherein they failed to exhibit wasp emergence, did not enter the prepupal stage, continued to feed and grew up to twofold larger than a normal, unparasitized caterpillar. Our results indicate hosts and parasitoids in this system have different thermal tolerances during development; the parasitoid wasp suffered complete mortality at a temperature regime that is mildly stressful for the unparasitized caterpillar host species. Our findings suggest C. congregata will suffer more severely under increasing temperatures than M. sexta, with cascading trophic and ecological effects. A free Plain Language Summary can be found within the Supporting Information of this article.

Each year, 33% of US citizens suffer from a musculoskeletal condition that requires medical intervention, with direct medical costs approaching $1 trillion USD per year. Despite the ubiquity of skeletal dysfunction, there are currently limited safe and efficacious bone growth factors in clinical use. Notch is a cell–cell communication pathway that regulates self-renewal and differentiation within the mesenchymal/osteoblast lineage. The principal Notch ligand in bone, Jagged-1, is a potent osteoinductive protein that positively regulates post-traumatic bone healing in animals. This report describes the temporal regulation of Notch during intramembranous bone formation using marrow ablation as a model system and demonstrates decreased bone formation following disruption of Jagged-1 in mesenchymal progenitor cells. Notch gain-of-function using recombinant Jagged-1 protein on collagen scaffolds promotes healing of craniofacial (calvarial) and appendicular (femoral) surgical defects in both mice and rats. Localized delivery of Jagged-1 promotes bone apposition and defect healing, while avoiding the diffuse bone hypertrophy characteristic of the clinically problematic bone morphogenetic proteins. It is concluded that Jagged-1 is a bone-anabolic agent with therapeutic potential for regenerating traumatic or congenital bone defects.

Changes in the Puget Sound ecosystem over the past 3 decades include increases in harbor seal (Phoca vitulina) abundance and declines in many of their preferred prey species. Harbor seals were outfitted with acoustic telemetry receivers and GPS tags to investigate spatial and temporal interactions with steelhead trout Oncorhynchus mykiss smolts implanted with acoustic transmitters. A total of 6846 tag detections from 44 different steelhead trout smolts (from an initial group of 246 smolts released into 2 rivers) were recorded by the 11 recovered sealmounted receivers. Central Puget Sound seal receivers detected a greater proportion of smolts surviving to the vicinity of the haul-out locations (29 of 51; 58%) than Admiralty Inlet seal receivers (7 of 50; 14%; p < 0.001). Detection data suggest that none of the tagged smolts were consumed by the 11 monitored seals. Nine smolts were likely consumed by non-tagged harbor seals based partly on detections of stationary tags at the seal capture haul-outs, although tag deposition by other predators cannot be ruled out. Smolts implanted with continuously pinging tags and smolts implanted with tags that were silent for the first 10 d after release were detected in similar proportions leaving Puget Sound (95% CI for the difference between proportions: −0.105 to 0.077) and stationary at harbor seal haul-outs (95% CI: −0.073 to 0.080). This study suggests that harbor seals contribute to mortality of migrating steelhead smolts, and we hypothesize that documented changes in the Puget Sound ecosystem may currently put steelhead smolts at greater risk of predation by harbor seals and possibly other predators.

1. Temperature strongly influences the rates of physiological processes in insects, including the herbivore Manduca sexta and its larval endoparasitoid Cotesia congregata. Parasitisation by C. congregata decreases the growth and consumption of food by larval M. sexta. However, the effects of temperature on parasitised caterpillars and the developing wasp larvae are largely unknown.2. In this study, parasitised and unparasitised caterpillars were reared at three constant temperatures (20, 25 and 30 °C) throughout larval development. Caterpillar mass gain and consumption were monitored daily until wandering (unparasitised control group) or wasp emergence (parasitised group) was observed. Development time and survival to emergence were measured as metrics of parasitoid performance.3. Parasitised M. sexta developed more slowly than unparasitised controls, but had similar cumulative consumption until the terminal instar. Parasitised caterpillars with relatively large parasitoid loads had higher rates of consumption and growth than those with smaller loads. Both temperature and parasitoid load strongly affected wasp success. Mean development time to wasp emergence increased with low temperatures and with large loads. The combination of warm temperature and large parasitoid loads greatly reduced wasp survival.4. These results demonstrate the interactive effects of rearing temperature and parasitisation on host consumption and growth rates throughout larval development. In addition, wasp performance was affected by the interaction of temperature and parasitoid load size. High temperatures alter the dynamics of the interaction between the parasitoid and its caterpillar host, which could have far‐reaching impacts as the global temperatures continue to rise.

Wild steelhead (Oncorhynchus mykiss) typically spend two or more years in freshwater before migrating to sea, but hatchery steelhead are almost ubiquitously released as yearlings. Their large size at release coupled with life history pathways that include both male and female maturation in freshwater present ecological risks different from those posed by hatchery populations of Pacific salmon. Yearling hatchery reared steelhead that fail to attain minimum thresholds for smoltification or exceed thresholds for male maturation tend to 'residualize' (i.e., remain in freshwater). Residuals pose ecological risks including size-biased interference competition and predation on juvenile salmon and trout. Three hatchery populations of steelhead in Hood Canal, WA were reared under growth regimes designed to produce a more natural age at smoltification (age-2) to aid in rebuilding their respective natural populations. Mean smolt sizes and size variability at age-2 were within the range of wild smolts for two of the three populations. The third population reared at a different facility under similar temperatures exhibited high growth rate variability and high male maturation rates (20% of all released fish). Experimentally comparing age-1 and age-2 smolt programs will help identify optimal rearing strategies to reduce the genetic risk of domestication selection and reduce residualism rates and associated negative ecological effects on natural populations. Investigations of Winthrop National Fish Hatchery summer-run steelhead will measure a) selection on correlated behavioral traits ('behavioral syndromes'), b) degree of smoltification, c) changes in hormones that regulate gonad growth at key developmental stages, and d) conduct extensive post-release monitoring of fish reared under each growth regime.