Protecting biodiversity in British Columbia: Recommendations for developing species at risk legislation

British Columbia has the greatest biological diversity of any province or territory in Canada. Yet increasing numbers of species in British Columbia are threatened with extinction. The current patchwork of provincial laws and regulations has not effectively prevented species declines. Recently, the Provincial Government has committed to enacting an endangered species law. Drawing upon our scientific and legal expertise, we offer recommendations for key features of endangered species legislation that build upon strengths and avoid weaknesses observed elsewhere. We recommend striking an independent Oversight Committee to provide recommendations about listing species, organize Recovery Teams, and monitor the efficacy of actions taken. Recovery Teams would evaluate and prioritize potential actions for individual species or groups of species that face common threats or live in a common area, based on best available evidence (including natural and social science and Indigenous Knowledge). Our recommendations focus on implementing an adaptive approach, with ongoing and transparent monitoring and reporting, to reduce delays between determining when a species is at risk and taking effective actions to save it. We urge lawmakers to include this strong evidentiary basis for species recovery as they tackle the scientific and socioeconomic challenges of building an effective species at risk Act.

Peripheral tissue oxygenation and the number of organs transplanted per donor

Current donor management practices target macrohaemodynamic parameters, but it is unclear if this leads to improvements in microvascular perfusion and tissue oxygenation; the latter may have more impact on organ status. In a recent preclinical study we determined that brain death impaired tissue perfusion and oxygen utilisation in swine while pharmacologic correction of these deficits improved organ function and reduced markers of tissue injury. As a first step in translating the preclinical findings, we conducted a prospective observational study to determine if there was an association between peripheral tissue oxygenation (measured by near-infrared spectroscopy) in deceased by neurological criteria human donors and the number of organs transplanted. In 60 donors, the mean time-weighted average of tissue oxygenation was 87.5% (standard deviation, SD, 5.2%) and the average number of organs transplanted was 3.5 (SD 2); there was a positive linear relationship between these two parameters. A 5% rise in tissue oxygenation was associated with an increase of 0.47 organs transplanted (95% confidence intervals 0.16 to 0.78) after adjusting for age (<i>P</i>=0.004). No such correlations were observed for the macrohaemodynamic or macro-oxygenation parameters (including arterial blood oxygenation). The results of this clinical trial are consistent with our preclinical work and support the postulate that targeting the microvasculature to improve tissue perfusion and tissue oxygen delivery in human donors has the potential to increase the quantity of organs suitable for transplant.

Salmon increase forest bird abundance and diversity

Resource subsidies across ecosystems can have strong and unforeseen ecological impacts. Marine-derived nutrients from Pacific salmon (Onchorhycus spp.) can be transferred to streams and riparian forests through diverse food web pathways, fertilizing forests and increasing invertebrate abundance, which may in turn affect breeding birds. We quantified the influence of salmon on the abundance and composition of songbird communities across a wide range of salmon-spawning biomass on 14 streams along a remote coastal region of British Columbia, Canada. Point-count data spanning two years were combined with salmon biomass and 13 environmental covariates in riparian forests to test for correlates with bird abundance, foraging guilds, individual species, and avian diversity. We show that bird abundance and diversity increase with salmon biomass and that watershed size and forest composition are less important predictors. This work provides new evidence for the importance of salmon to terrestrial ecosystems and information that can inform ecosystem-based management.

Working constructively toward an improved North American approach to wildlife management

Mawdsley et al. (2018) respond disapprovingly to our 2018 review of 667 wildlife management systems across Canada and the United States, which found that many of these systems lacked the scientific hallmarks of clear objectives, evidence, transparency, and independent review. Although we strongly agree with several of Mawdsley et al.'s points about the role of science in management, their response suggests confusion about three elements of our approach that we clarify herein: (i) the selection of hallmarks, (ii) the role of science in wildlife management, and (iii) our engagement with wildlife agencies. We contend that both critics and defenders of the current approach to wildlife management in Canada and the United States similarly desire rigorous management that achieves social and ecological benefits. Our original study-which used a clear approach to define hallmarks of science-based management, employed a reasonable set of indicator criteria to test for them, and was based on data available to the general public on whose behalf management is conducted-found evidence that the current approach falls short. However, it also provided a framework for addressing shortcomings moving forward. We suggest that advancing discussion on the operational role of science in management, including clarifying what "science-based management" actually means, could curtail practitioners and critics of the status quo talking over each other's heads and encourage all parties to work constructively to improve the governance of wildlife at a continental scale.

Oust the louse: leaping behaviour removes sea lice from wild juvenile sockeye salmon Oncorhynchus nerka

We conducted a manipulative field experiment to determine whether the leaping behaviour of wild juvenile sockeye salmon Oncorhynchus nerka dislodges ectoparasitic sea lice Caligus clemensi and Lepeophtheirus salmonis by comparing sea-lice abundances between O. nerka juveniles prevented from leaping and juveniles allowed to leap at a natural frequency. Juvenile O. nerka allowed to leap had consistently fewer sea lice after the experiment than fish that were prevented from leaping. Combined with past research, these results imply potential costs due to parasitism and indicate that the leaping behaviour of juvenile O. nerka does, in fact, dislodge sea lice.

The effect of inhalational anaesthesia during deceased donor organ procurement on post-transplantation graft survival

Many deceased by neurologic criteria donors are administered inhalational agents during organ recovery surgery-a process that is characterised by warm and cold ischaemia followed by warm reperfusion. In certain settings, volatile anaesthetics (VA) are known to precondition organs to protect them from subsequent ischaemia-reperfusion injury. As such, we hypothesised that exposure to VA during organ procurement would improve post-graft survival. Lifebanc (organ procurement organisation [OPO] for NE Ohio) provided the investigators with a list of death by neurologic criteria organ donors cared for at three large tertiary hospitals in Cleveland between 2006 and 2016-details about the surgical recovery phase were extracted from the organ donors' medical records. De-identified data on graft survival were obtained from the United Network for Organ Sharing (UNOS). The collated data underwent comparative analysis based on whether or not VA were administered during procurement surgery. Records from 213 donors were obtained for analysis with 138 exposed and 75 not exposed. Demographics, medical histories, and organ procurement rates were similar between the two cohorts. For the primary endpoint, there were no significant differences observed in either early (30-day) or late (five-year) graft survival rates for kidney, liver, lung, or heart transplants. Our findings from this retrospective review of a relatively small cohort do not support the hypothesis that the use of VA during the surgical procurement phase improves graft survival. Reviews of larger datasets and/or a prospective study may be required to provide a definitive answer.

Hallmarks of science missing from North American wildlife management

Resource management agencies commonly defend controversial policy by claiming adherence to science-based approaches. For example, proponents and practitioners of the "North American Model of Wildlife Conservation," which guides hunting policy across much of the United States and Canada, assert that science plays a central role in shaping policy. However, what that means is rarely defined. We propose a framework that identifies four fundamental hallmarks of science relevant to natural resource management (measurable objectives, evidence, transparency, and independent review) and test for their presence in hunt management plans created by 62 U.S. state and Canadian provincial and territorial agencies across 667 management systems (species-jurisdictions). We found that most (60%) systems contained fewer than half of the indicator criteria assessed, with more criteria detected in systems that were peer-reviewed, that pertained to "big game," and in jurisdictions at increasing latitudes. These results raise doubt about the purported scientific basis of hunt management across the United States and Canada. Our framework provides guidance for adopting a science-based approach to safeguard not only wildlife but also agencies from potential social, legal, and political conflict.

Reduced growth in wild juvenile sockeye salmon Oncorhynchus nerka infected with sea lice

Daily growth rings were examined in the otoliths of wild juvenile sockeye salmon Oncorhynchus nerka to determine whether infection by ectoparasitic sea lice Caligus clemensi and Lepeophtheirus salmonis was associated with reduced host body growth, an important determinant of survival. Over 98% of the sea lice proved to be C. clemensi and the fish that were highly infected grew more slowly than uninfected individuals. Larger fish also grew faster than smaller fish. Finally, there was evidence of an interaction between body size and infection status, indicating the potential for parasite-mediated growth divergence.

MUTUAL MATE CHOICE AND SEX DIFFERENCES IN CHOOSINESS

Sexual competition is associated closely with parental care because the sex providing less care has a higher potential rate of reproduction, and hence more to gain from competing for multiple mates. Sex differences in choosiness are not easily explained, however. The lower-caring sex (often males) has both higher costs of choice, because it is more difficult to find replacement mates, and higher direct benefits, because the sex providing more care (usually females) is likely to exhibit more variation in the quality of contributions to the young. Because both the costs and direct benefits of mate choice increase with increasing parental care by the opposite sex, general predictions about sex difference in choosiness are difficult. Furthermore, the level of choosiness of one sex will be influenced by the choosiness of the other. Here, we present an ESS model of mutual mate choice, which explicitly incorporates differences between males and females in life history traits that determine the costs and benefits of choice, and we illustrate our results with data from species with contrasting forms of parental care. The model demonstrates that sex differences in costs of choice are likely to have a much stronger effect on choosiness than are differences in quality variation, so that the less competitive sex will commonly be more choosy. However, when levels of male and female care are similar, differences in quality variation may lead to higher levels of both choice and competition in the same sex.

Effects of habitat features on size-biased predation on salmon by bears

Predators can drive trait divergence among populations of prey by imposing differential selection on prey traits. Habitat characteristics can mediate predator selectivity by providing refuge for prey. We quantified the effects of stream characteristics on biases in the sizes of spawning salmon caught by bears (Ursus arctos and U. americanus) on the central coast of British Columbia, Canada by measuring size-biased predation on spawning chum (Oncorhynchus keta) and pink (O. gorbuscha) salmon in 12 streams with varying habitat characteristics. We tested the hypotheses that bears would catch larger than average salmon (size-biased predation) and that this bias toward larger fish would be higher in streams that provide less protection to spawning salmon from predation (e.g., less pools, wood, undercut banks). We then we tested for how such size biases in turn translate into differences among populations in the sizes of the fish. Bears caught larger-than-average salmon as the spawning season progressed and as predicted, this was most pronounced in streams with fewer refugia for the fish (i.e., wood and undercut banks). Salmon were marginally smaller in streams with more pronounced size-biased predation but this predictor was less reliable than physical characteristics of streams, with larger fish in wider, deeper streams. These results support the hypothesis that selective forces imposed by predators can be mediated by habitat characteristics, with potential consequences for physical traits of prey.

Sneaker Males Affect Fighter Male Body Size and Sexual Size Dimorphism in Salmon

Large male body size is typically favored by directional sexual selection through competition for mates. However, alternative male life-history phenotypes, such as "sneakers," should decrease the strength of sexual selection acting on body size of large "fighter" males. We tested this prediction with salmon species; in southern populations, where sneakers are common, fighter males should be smaller than in northern populations, where sneakers are rare, leading to geographical clines in sexual size dimorphism (SSD). Consistent with our prediction, fighter male body size and SSD (fighter male∶female size) increase with latitude in species with sneaker males (Atlantic salmon Salmo salar and masu salmon Oncorhynchus masou) but not in species without sneakers (chum salmon Oncorhynchus keta and pink salmon Oncorhynchus gorbuscha). This is the first evidence that sneaker males affect SSD across populations and species, and it suggests that alternative male mating strategies may shape the evolution of body size.

Salmon nutrients are associated with the phylogenetic dispersion of riparian flowering-plant assemblages

A signature of nonrandom phylogenetic community structure has been interpreted as indicating community assembly processes. Significant clustering within the phylogenetic structure of a community can be caused by habitat filtering due to low nutrient availability. Nutrient limitation in temperate Pacific coastal rainforests can be alleviated to some extent by marine nutrient subsidies introduced by migrating salmon, which leave a quantitative signature on the makeup of plant communities near spawning streams. Thus, nutrient-mediated habitat filtering could be reduced by salmon nutrients. Here, we ask how salmon abundance affects the phylogenetic structure of riparian flowering plant assemblages across 50 watersheds in the Great Bear Rainforest of British Columbia, Canada. Based on a regional pool of 60 plant species, we found that assemblages become more phylogenetically dispersed and species poor adjacent to streams with higher salmon spawning density. In contrast, increased phylogenetic clumping and species richness was seen in sites with low salmon density, with steeper slopes, further from the stream edge, and within smaller watersheds. These observations are all consistent with abiotic habitat filtering and biotic competitive exclusion acting together across local and landscape-scale gradients in nutrient availability to structure assembly of riparian flowering plants. In this case, rich salmon nutrients appear to release riparian flowering-plant assemblages from the confines of a low-nutrient habitat filter that drives phylogenetic clustering.

Costs of reproduction can explain the correlated evolution of semelparity and egg size: theory and a test with salmon

Species' life history traits, including maturation age, number of reproductive bouts, offspring size and number, reflect adaptations to diverse biotic and abiotic selection pressures. A striking example of divergent life histories is the evolution of either iteroparity (breeding multiple times) or semelparity (breed once and die). We analysed published data on salmonid fishes and found that semelparous species produce larger eggs, that egg size and number increase with salmonid body size among populations and species and that migratory behaviour and parity interact. We developed three hypotheses that might explain the patterns in our data and evaluated them in a stage-structured modelling framework accounting for different growth and survival scenarios. Our models predict the observation of small eggs in iteroparous species when egg size is costly to maternal survival or egg number is constrained. By exploring trait co-variation in salmonids, we generate new hypotheses for the evolution of trade-offs among life history traits.

Ten principles from evolutionary ecology essential for effective marine conservation

Sustainably managing marine species is crucial for the future health of the human population. Yet there are diverse perspectives concerning which species can be exploited sustainably, and how best to do so. Motivated by recent debates in the published literature over marine conservation challenges, we review ten principles connecting life‐history traits, population growth rate, and density‐dependent population regulation. We introduce a framework for categorizing life histories, POSE (Precocial–Opportunistic–Survivor–Episodic), which illustrates how a species’ life‐history traits determine a population's compensatory capacity. We show why considering the evolutionary context that has shaped life histories is crucial to sustainable management. We then review recent work that connects our framework to specific opportunities where the life‐history traits of marine species can be used to improve current conservation practices.

Effects of salmon-derived nutrients and habitat characteristics on population densities of stream-resident sculpins

Movement of nutrients across ecosystem boundaries can have important effects on food webs and population dynamics. An example from the North Pacific Rim is the connection between productive marine ecosystems and freshwaters driven by annual spawning migrations of Pacific salmon (Oncorhynchus spp). While a growing body of research has highlighted the importance of both pulsed nutrient subsidies and disturbance by spawning salmon, their effects on population densities of vertebrate consumers have rarely been tested, especially across streams spanning a wide range of natural variation in salmon densities and habitat characteristics. We studied resident freshwater prickly (Cottus asper), and coastrange sculpins (C. aleuticus) in coastal salmon spawning streams to test whether their population densities are affected by spawning densities of pink and chum salmon (O. gorbuscha and O. keta), as well as habitat characteristics. Coastrange sculpins occurred in the highest densities in streams with high densities of spawning pink and chum salmon. They also were more dense in streams with high pH, large watersheds, less area covered by pools, and lower gradients. In contrast, prickly sculpin densities were higher in streams with more large wood and pools, and less canopy cover, but their densities were not correlated with salmon. These results for coastrange sculpins provide evidence of a numerical population response by freshwater fish to increased availability of salmon subsidies in streams. These results demonstrate complex and context-dependent relationships between spawning Pacific salmon and coastal ecosystems and can inform an ecosystem-based approach to their management and conservation.

Location is everything: evaluating the effects of terrestrial and marine resource subsidies on an estuarine bivalve

Estuaries are amongst the world's most productive ecosystems, lying at the intersection between terrestrial and marine environments. They receive substantial inputs from adjacent landscapes but the importance of resource subsidies is not well understood. Here, we test hypotheses for the effects of both terrestrial- and salmon-derived resource subsidies on the diet (inferred from stable isotopes of muscle tissue), size and percent nitrogen of the soft-shell clam (Mya arenaria), a sedentary estuarine consumer. We examine how these relationships shift across natural gradients among 14 estuaries that vary in upstream watershed size and salmon density on the central coast of British Columbia, Canada. We also test how assimilation and response to subsidies vary at smaller spatial scales within estuaries. The depletion and enrichment of stable isotope ratios in soft-shell clam muscle tissue correlated with increasing upstream watershed size and salmon density, respectively. The effects of terrestrial- and salmon-derived subsidies were also strongest at locations near stream outlets. When we controlled for age of individual clams, there were larger individuals with higher percent nitrogen content in estuaries below larger watersheds, though this effect was limited to the depositional zones below river mouths. Pink salmon exhibited a stronger effect on isotope ratios of clams than chum salmon, which could reflect increased habitat overlap as spawning pink salmon concentrate in lower stream reaches, closer to intertidal clam beds. However, there were smaller clams in estuaries that had higher upstream pink salmon densities, possibly due to differences in habitat requirements. Our study highlights the importance of upstream resource subsidies to this bivalve species, but that individual responses to subsidies can vary at smaller scales within estuaries.

Evolutionary consequences of fishing and their implications for salmon

We review the evidence for fisheries-induced evolution in anadromous salmonids. Salmon are exposed to a variety of fishing gears and intensities as immature or maturing individuals. We evaluate the evidence that fishing is causing evolutionary changes to traits including body size, migration timing and age of maturation, and we discuss the implications for fisheries and conservation. Few studies have fully evaluated the ingredients of fisheries-induced evolution: selection intensity, genetic variability, correlation among traits under selection, and response to selection. Most studies are limited in their ability to separate genetic responses from phenotypic plasticity, and environmental change complicates interpretation. However, strong evidence for selection intensity and for genetic variability in salmon fitness traits indicates that fishing can cause detectable evolution within ten or fewer generations. Evolutionary issues are therefore meaningful considerations in salmon fishery management. Evolutionary biologists have rarely been involved in the development of salmon fishing policy, yet evolutionary biology is relevant to the long-term success of fisheries. Future management might consider fishing policy to (i) allow experimental testing of evolutionary responses to exploitation and (ii) improve the long-term sustainability of the fishery by mitigating unfavorable evolutionary responses to fishing. We provide suggestions for how this might be done.

Maternal and environmental influences on egg size and juvenile life-history traits in Pacific salmon

Life-history traits such as fecundity and offspring size are shaped by investment trade-offs faced by mothers and mediated by environmental conditions. We use a 21-year time series for three populations of wild sockeye salmon (Oncorhynchus nerka) to test predictions for such trade-offs and responses to conditions faced by females during migration, and offspring during incubation. In years when their 1100 km upstream migration was challenged by high water discharges, females that reached spawning streams had invested less in gonads by producing smaller but not fewer eggs. These smaller eggs produced lighter juveniles, and this effect was further amplified in years when the incubation water was warm. This latter result suggests that there should be selection for larger eggs to compensate in populations that consistently experience warm incubation temperatures. A comparison among 16 populations, with matching migration and rearing environments but different incubation environments (i.e., separate spawning streams), confirmed this prediction; smaller females produced larger eggs for their size in warmer creeks. Taken together, these results reveal how maternal phenotype and environmental conditions can shape patterns of reproductive investment and consequently juvenile fitness-related traits within and among populations.