Fisheries‐induced evolution of alternative male life history tactics in Coho salmon

Abstract Fisheries‐induced evolution (FIE) can result when harvest imposes artificial selection on variation in heritable phenotypic traits. While there is evidence for FIE, it remains difficult to disentangle the contributions of within‐generation demographic adjustment, phenotypic plasticity, and genetic adaption to observed changes in life history traits. We present evidence for FIE using dozens of Coho salmon (Oncorhynchus kisutch) populations in which males adopt one of two age‐invariant, heritable life history tactics: most mature as large three‐year‐old “hooknose” and typically fight for spawning opportunities, while some mature as small two‐year‐old “jacks” and fertilize eggs through sneaking. The closure of a fishery targeting three‐year‐old fish provided an experimental test of the prediction that fishery‐imposed selection against hooknose males drives an evolutionary increase in the proportion of males adopting the jack tactic. The data support the prediction: 43 of 46 populations had higher jack proportions during than after the fishery. The data further suggest that changes in jack proportion were not solely the result of demographic adjustments to harvest. We suggest that systems where fisheries differentially exploit phenotypically discrete, age‐invariant life histories provide excellent opportunities for detecting FIE.

. First, the strength of fishery-imposed selection is often less than that imposed in relevant experiments (Hilborn & Minte-Vera, 2008). Second, the nature of life history traits may constrain the evolutionary response to fishery-imposed selection.
Life history traits can have relatively low heritability because they are closely related to fitness, integrate variation across multiple component traits, are strongly affected by environmental variance, and may often be underlain by nonadditive dominance and epistatic variance (Merilä & Sheldon, 1999;Mousseau & Roff, 1987;Price & Schluter, 1991). Similarly, continuous life history traits such as age and size at maturity are mechanistically correlated, making it difficult to disentangle the contributions of phenotypic plasticity and evolutionary change to observed changes in trait values.
While probabilistic maturation reaction norm analysis has gone some way in separating the contributions of plasticity and genetic adaption to changing maturation schedules, uncertainty is inevitable (Dieckmann & Heino, 2007). Third, many case studies of FIE involve single exploited populations or stocks monitored during a fishery and are thus unreplicated observations lacking experimental manipulation associated with the initiation or closure of the fishery (Heino et al., 2015). Finally, fisheries-induced changes in life history traits can occur without FIE. Life history traits may change simply due to annual demographic adjustment to harvest or phenotypic plasticity in response to changes in population size, community composition, and environmental conditions caused by (or coincident with) the fishery of interest (Eikeset et al., 2016;Kuparinen & Merilä, 2007).
The challenge of implicating FIE may be best met using systems where: a fishery targets a subset of phenotypically discrete, age-invariant, and heritable life histories; data on the relative frequency of each life history span periods before and after the initiation or cessation of the fishery; such data exist for multiple populations subjected to a common fishery; analyses can reasonably account for the effects of temporal variation in relevant population indices and environmental conditions (Kuparinen & Merilä, 2007).

Anadromous, semelparous Coho salmon (Oncorhynchus kisutch)
from the Oregon coast (USA) meet these criteria reasonably well.
All females and most males mature as three-year-olds following an 18-month ocean phase, while some males mature precociously as smaller two-year-olds following six months in the ocean (Figure 1a).  Nickelson, 1986;Scarnecchia, 1981), and relevant environmental data are available from throughout the period of population monitoring.
Here, we use male Coho life history variation, the "pulse experiment" of a fishery and its closure, and demographic data from dozens of populations to test the prediction that fishery-imposed selection against three-year-old males increased the proportion of two-year-old males in breeding populations (Gross, 1991;Myers, 1986). The data support this prediction and offer additional evidence that FIE contributed to the observed changes in male life history.

BOX 1 Lessons from Louis
My academic relationship with Louis began at the Canadian Society for Ecology and Evolution conference in 2009; I was asking him about the publication of a salmonid phylogeny that had been in the making for a while. A relatively decent French background, along with a blossoming understanding of phylogenetic analyses, led to my involvement in helping to publish the phylogeny that had to be repackaged from a thesis written in French. This was a four months postdoc with a single goal-to get the paper out while it was still relevant. Aside from the standard lessons that we all learn from gifted academics (i.e., do your best, get the work out and share it with the world), I learned a couple extra things about Louis during that time as well.
The first was that he is up on the latest trends. The evidence for this came from my correspondence with Louis, always via email. In my email software program, the signoffs from Louis (on good news days) were always "Louis J"; this led me to think that he had a secret middle name that was kept off of the countless papers that he had authored. In retrospect, I'm glad that I never asked him about this-I first thought it was a weird recurring typo and attributed this to his remarkable ability to field emails at a rapid pace. Years (literally) later, I realized that the "J" was an early version of a poorly translate happy face emoticon, and neither my luddite brain nor my email program was equipped to make that translation. Bottom line: Louis was using emojis before it was something that became integral to virtual communication. The second lesson that I learned from Louis was that no matter how successful or driven a person may be, it is always okay to be human. Witnessing, and being a part of, Louis' interactions has influenced how I interact with students and colleagues-Louis could be tough on people at times, but he was always compassionate in the end. I think about this every time I am a bit frustrated, and I remember how he always encouraged us in these weird moments, even if he was probably feeling a bit annoyed himself. To this day, over a decade after our short academic relationship, he still notices the littlest things about what I (and almost countless others) am up to; this is a testament to his humanity, and the care he puts into his trainees. That is the kind of mentor I strive to be.

| Coho life history and FIE
Oregon coast Coho have two discrete, age-invariant life histories. All juveniles spend 18 months in freshwater before migrating to the ocean as smolts, and all females mature as three-year-olds after 18 months in the ocean (Figure 1a). Most males also mature as three-year-old "hooknose" and typically adopt a "fighter" tactic when competing for access to spawning females. Other males mature precociously as "jacks" after six months in the ocean and usually adopt a "sneaker" tactic to fertilize eggs released by females mating with hooknose males (Gross, 1991). Male maturation age is heritable (jacks sire more jacks than hooknose males and vice versa), affected by maternal egg size (large eggs produce large juveniles more likely to mature as jacks), and condition-dependent: juvenile males that reach a size/growth condition-dependent threshold mature as two-year-old jacks (Appleby, Tipping, & Seidel, 2003;Iwamoto, Alexander, & Hershberger, 1984;Silverstein & Hershberger, 1992).
Understanding of the Coho jack-hooknose system has developed alongside broader research on the evolutionary ecology of alternative reproductive phenotypes in both salmon and other animal taxa. Gross (1985) first described the system as a genetically polymorphic mixed evolutionarily stable strategy (mESS) in which population-specific jack proportions occur where the lifetime fitness (survival to maturity × mating success) equality of the two strategies is maintained via negative frequency-dependent sexual selection. He later proposed the system operates as a single genetically monomorphic conditional life history strategy with alternative tactics, the average lifetime fitnesses of which need not be equal (Gross, 1996). Neither of these models offers a satisfactory description of the jack-hooknose system, and the latter has been criticized because the assumption of genetic monomorphism is unrealistic, especially in an evolutionary context (Shuster & Wade, 2003;Tomkins & Hazel, 2007). We build upon Tomkins and Hazel's (2007) environmental threshold model, informed by research on other salmon species, to offer a conceptual framework for understanding the evolutionary ecology of the Coho jack-hooknose system and the influence of FIE on jack proportions ( Figure 2). Importantly, our framework accommodates two features of the system: in Coho and other salmon species precocious male maturation is rare or absent in northern populations where juvenile growth rates are low (Weir, Kindsvater, Young, & Reynolds, 2016); and jacks persistently occur in hatchery populations that use only hooknose males for breeding, but in which juvenile growth rates are markedly higher than in the wild (Vøllestad, Peterson, & Quinn, 2004).
The irreversible decision by a male to mature as a two-year-old jack or three-year-old hooknose is made at age S A during the early juvenile stage. Males that reach a size or condition threshold S C by age S A mature as jacks, while males that do not reach S C mature as hooknose (Figure 2a). Within a population, there is genetic variation in S C , such that, strictly speaking, each male's life history reaction norm is a different conditional strategy (Figure 2b). In any population, there is thus variation in both S C and condition at age S A , such that some proportions of males have condition ≥ S C and mature as jacks (Figure 2c). Males that mature as jacks will tend to have low S C and/or relatively high condition at age S A (Berejikian, Van Doornik, & Atkins, 2011). Whereas variance in S C is likely determined principally by genetic variance, the greater phenotypic variance in condition will depend on genetic variance in traits related to growth, but will also be strongly influenced by environmental variation. For any population, plotting the distributions of F I G U R E 1 (a) Coho salmon life history on the Oregon (USA) coast. All fish spend 18 months rearing in freshwater before migrating to the ocean as smolts. All females and most males (hooknose) mature as three-year-olds after 18 months in the ocean, while some males (jack) mature precociously after six months at sea. A coast-wide commercial fishery harvested three-year-old fish until its closure in 2003 (vertical arrow). (b) Estimates of the exploitation rate on three-year-olds (solid and dashed black lines) and coast-wide three-year-old escapement (gray line) from 1950 to 2003. The commercial fishery was closed after the 1993 season, but harvest continued at low levels For Coho salmon populations in the wild, a fishery that harvests hooknose males will impose artificial viability selection against fish with high S C and/or slow juvenile growth ( Figure 2c). Such fisheries can thus drive FIE increases in jack proportion by increasing a population's mean condition at age S A and/or decreasing the population's mean S C at age S A (Figure 2d). This evolutionary response will be modified by the genetic architecture of and correlations between F I G U R E 2 A graphical depiction of the evolutionary ecology and Fisheries-Induced Evolution (FIE) of male Coho salmon life history (informed by Gross, 1991Gross, , 1996Hutchings & Myers, 1994;Shuster & Wade, 2003;Tomkins & Hazel, 2007). (a) The two life histories of male Coho salmon from Oregon coast (USA) populations. After rearing for 18 months in freshwater, most males spend 18 months in the ocean before maturing as large three-year-old "hooknose," while some males mature after only six months in the ocean as small two-year-old "jacks." The irreversible decision between life history tactics occurs at age S A of the freshwater stage: juvenile males meeting a condition (size) threshold S C at age S A mature as jacks. Males adopting the hooknose and jack life history tactics typically use "fighting" and "sneaking" behavioral tactics, respectively, to gain access to spawning females. (b) A depiction of variation in male conditional life history strategy reaction norms. The life history tactic adopted by a male depends both on its heritable S C and its condition at age S A , which will depend on both environmental conditions and heritable variation in traits related to juvenile growth. (c) In any population, there will be variation in both S C and condition at age S A . The distributions are normal with greater variation in condition than S C . The graded bars highlight that the decision to adopt the jack strategy is more likely for males with high condition and/or a low S C . (d) The distributions of S C and condition at age S A can be visualized as an ellipse in a condition-S C life history phase space. In this example, fish have condition-S C combinations in both the hooknose (condition < S C ) and jack (condition ≥ S C ) regions of the phase space. The two dashed ellipses show how a fishery targeting hooknose males can drive FIE toward higher jack proportions by imposing viability selection against males with high S C and/or low condition. The orientation of an ellipse, and the evolutionary response to selection, will depend on the phenotypic and genetic correlations between condition and S C , which is assumed here to be zero. This life history phase space accommodates two important features of Coho "natural" history. First, jacks are rare or absent in northern populations with low juvenile growth rates because few or no males grow quickly enough to meet S C min. at age S A . Second, hatchery populations that use only hooknose males for breeding regularly produce some jack males because unnaturally high juvenile growth rates allow some juvenile males to meet S C max. at age S A relevant traits (Merilä & Sheldon, 1999;Schluter, 1996), any environmentally induced changes in juvenile growth rates that affect the distribution of condition at age S A , and the effects on lifetime fitness of changes in density-and frequency-dependent sexual selection acting on the mature male phenotypes (Berejikian et al., 2010;Fleming & Gross, 1994;Roff, 1996).

| Demographic data
The ODFW began conducting spawning ground surveys during the these data provide estimates of three-year-old and jack abundance for dozens of populations during (1950,(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993) and after (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)) the commercial fishery. We considered only wild-born fish, and the data were corrected for observer efficiency because during spawning ground surveys large adults are easier to see than smaller jacks; observer efficiency is corrected by multiplying the number of jacks by 2 and the number of adults by 1.3 (Solazzi, 1984). Assuming a 1:1 sex ratio for three-year-old adults (Koseki & Fleming, 2007;Nickelson, 2001;Young, 1999), annual jack proportion was calculated as: Annual jack proportions were calculated using both the peak count and (from 1981) area under the curve (AUC) estimates. The AUC method uses data from the multiple surveys and the lifespan of spawning fish to calculate estimates of total escapement (Young, 1999). Jack proportion values based on peak counts and AUC estimates were strongly positively correlated (Table S1). We thus used peak count data in all analyses to include populations/ years with insufficient surveys to calculate AUC estimates and to include data from 1950 to 1980. To estimate breeding densities (m −2 ), we used peak count data divided by the product of survey length and bankfull width, which we estimated according to Faustini, Kaufmann, and Herlihy (2009).
We calculated annual jack proportions using return year (jack and hooknose from year t) rather than brood year (jack t, hooknose t + 1) for three reasons (Koseki & Fleming, 2007). First, return year jack proportions reflect the conditions experienced by male Coho during breeding and are thus more relevant to sexual selection's role in determining within-and between-population variation in the expression of male life history tactics. Second, using return year jack proportion controls for random and systematic errors associated with interannual variation in observer ability and survey conditions. Third, using brood year would reduce the number of observations available for analysis because a single year (t) of missing data eliminates three years (t−1, t, t + 1) of jack proportion estimates.
However, we repeated our main analyses using brood year jack proportions, and our results were qualitatively unchanged ( Figure S1).

| Environmental data
Because the relative abundance of jacks and hooknose males may be influenced by temporal variation in environmental conditions, we compiled data on three factors known to affect survival and recruitment in Oregon coast Coho salmon: marine upwelling, sea surface temperature, and streamflow (Nickelson, 1986;Scarnecchia, 1981).
While this list is not exhaustive, it did allow us to compare the environment experienced by jacks and adults during and after the fishery. The values for these environmental parameters fluctuated irregularly on a year-to-year basis ( Figure S2). Our aim is not to assess correlates of jack and adult returns, but rather to control for how environmental conditions may affect the proportion of jacks in a given year. Thus, for each of these variables, we calculated the ratio of conditions experienced by jack (t) and hooknose (t−1) and compared these ratios before and after the fishery closure in 1994.
Marine upwelling data are mean monthly volume estimates ob- where m 3 represents upwelling volume for a particular month, and t is a given year. In addition to analysis of upwelling ratios at individual stations, we calculated the mean of these three ratios as an overall metric for the area of the ocean used by Oregon Coho salmon. Because demographic data were collected for 30 populations beginning in 1950, with another 16 added in 1981 (see details below), we compared upwelling data before and after the fishery closure using all data as well as data only from 1981 onward, when all 46 populations could be used for other analyses. We found no strong evidence for differences between the mean upwelling ratios during and after the fishery (Table   S2; Figure S2). year to reflect conditions during the spring and summer. As for the marine upwelling data, we took the ratio of SST means experienced jack abundance jack abundance + hooknose abundance by two-year-old jacks (µSST t ) and three-year-old hooknose (µSST t-1 ) males. Again, means during and after the fishery did not differ considerably for this variable (Table S2; Figure S2).
Streamflow data were obtained from the United States Geological Survey (USGS; http://water data.usgs.gov). We summed the mean monthly flow rate from five Oregon coast rivers between 1948 and 2003 and calculated the total flow experience by jack and hooknose males during their 18-month freshwater residency as: where t is a given year. These values were compared as above and did not differ between the periods during and after the fishery (Table S2; Figure S2).
Although interannual variation in environmental conditions appeared unlikely to influence our results, we nonetheless constructed additive models to account for the effect of marine upwelling, sea surface temperature, and streamflow on jack proportions. For each population, jack proportion was regressed on the ratios of the three environmental parameters using a linear model: where Y i is a population's jack proportion for year i. We used the residuals from this model for analyses of "environmentally corrected" jack proportions.

| Pre-and postfishery closure comparison
To test our main prediction that fishery-imposed selection against hooknose males would drive increases in jack proportions (Figure 2d), we used data from 1981 to 1993 and 1994 to 2003 to calculate the mean jack proportions of 46 populations during and after the fishery. The same approach was used for the environmentally corrected data; residuals from the linear model for each population were averaged for the two time periods. Jack proportion during and after the fishery for both datasets were compared using linear mixed-effects models with stream as a random effect to account for the paired nature of the data; the unit of observation for this analysis was the 46 populations.

| Evidence for evolutionary change
For given numbers of returning hooknose and jack males, harvesting three-year-old fish will clearly increase return year jack proportions through demographic adjustment. To assess the relative importance of demographic adjustment and FIE, we conducted four analyses exploring interannual variation in populations' jack proportions during the fishery. For three "temporal" hypotheses, we used only the 30 populations with data from 1950 because these populations provide a sufficient number of observations for meaningful analyses.
Before doing these analyses, we interrogated the data to determine whether temporal autocorrelation affected our analyses. We found no evidence of temporal autocorrelation (Appendix S1: Methods and Analyses) and thus proceeded with mixed modeling and correlation approaches.
First, we tested whether fishery exploitation rate significantly affected interannual variation in jack proportion. To this end, we calculated the correlation coefficient between exploitation rate and jack proportion for each of the 30 populations; positive correlations would suggest demographic adjustment to harvest was important.
We then tested whether exploitation rate affected interannual variation in jack proportion by regressing jack proportion on exploitation rate using a linear mixed-effects model with jack proportion as the dependent variable, exploitation rate as a fixed effect, and population as a random effect (n = 30). Second, noting that exploitation rate did not increase systematically during the fishery (Figure 1b) for the paired nature of the analysis. We asked whether declines in jack proportion following the fishery closure were due simply to increases in three-year-old density (same slope and intercept) or to a change in the relationship between three-year-old density and the proportion of males adopting the jack tactic (different slopes and/ or intercepts). Second, we compared mean adult and jack escapement across populations during and after the fishery using linear mixed-effects models with population as a random effect (n = 46).
If declines in jack proportion reflected an evolutionary response to the cessation of the fishery targeting adults, we predict that jack escapement would decline despite increases in adult escapement.
All analyses were conducted in R 3.6.2 (R Core Team, 2019).
Mixed models were constructed using the lme4 package in R (Bates, Mächler, Bolker, & Walker, 2015). To assess model fits, likelihoods were calculated using the maximum likelihood method and compared using Akaike information criteria (AIC).

| RE SULTS
We found strong support for our principal prediction. In 43 of 46 populations, mean jack proportion was higher during than after the fishery (Table 1; Figure 3). For the 30 populations with data from 1950, there was no evidence that exploitation rate and jack proportion were positively correlated during the fishery; rather, most correlations were negative (Figure 4a). A linear mixed-effects model that directly examined the influence of exploitation rate on jack proportion supports these results, such that the overall effect of harvest rate on jack proportion across all populations was weak and negative (Table 1, Figure 4b). While exploitation decreased following its peak in the 1970s (quadratic model  Note: The number of parameters (k), Akaike information criterion values (AIC), the difference between the best model and the other model (ΔAIC) and relative model weight (ω i ) are shown for each analysis. We considered the model with the lowest AIC to be of best fit if ΔAIC > 2; these models are in bold. Parameter estimates are shown if they provide information regarding the direction of change in the data.

TA B L E 1
Model fits for linear mixedeffects models to examine evidence for evolutionary change main and supplementary results reveal that fishery-imposed selection was associated with increased jack proportions across dozens of populations and that demographic adjustment to variation in exploitation rate does not appear to solely explain variation in jack proportion among or across populations. These results were qualitatively unchanged after controlling for interannual variation in environmental conditions.
Our final analysis using the 46 populations with data from 1981 reveals how the relationship between adult density, jack density, and jack proportion was affected by the fishery (Figure 5). During both periods, populations with higher mean adult breeding densities tended to have higher mean jack proportions, a pattern consistent with previous observations (Young, 1999). While the slopes of these relationships were similar, the intercept was significantly higher during the fishery (Table 1); thus, for a given density of three-year-old spawners, the proportion of males adopting the jack life history tactic was significantly higher during than after the fishery. This result is not simply due to adult densities increasing more than jack densities following the fishery closure. While adult densities increased significantly following the 1993 closure (Table 1; Figure 5b), jack densities tended to decrease (Table 1; Figure 5c).  Figure 2d).

| D ISCUSS I ON
The roles of these two direct mechanisms in driving FIE are unclear and likely complex. Data from Coho (Silverstein & Hershberger, 1992, Chinook (Oncorhynchus tshawytscha; Spangenberg et al., 2015), and Atlantic salmon (Salmo salar; Aubin-Horth & Dodson, 2004;Piché, Hutchings, & Blanchard, 2008) suggest there is heritable variation in both juvenile growth rate (condition) and S C within and between our study populations ( Figure 2b,c). The environmental threshold model (Tomkins & Hazel, 2007) sensibly assumes higher phenotypic variance in condition than S C (Figure 2c), but how the trait distributions respond to viability selection against hooknose males will depend on the heritability of the traits, and the genetic architecture of (Merilä & Sheldon, 1999) and correlations between (Schluter, 1996) traits.
We are not aware of data on how S C variance might depend on additive, dominance, and epistatic genetic variance, but condition  (Schluter, 1996).
We should expect the evolutionary response to direct viability selection against hooknose males to be mediated by other evolutionary and ecological processes (Eikeset et al., 2016;Gross, 1991;Kuparinen & Merilä, 2007). From an evolutionary perspective, fishery-imposed selection favors jacks directly through the survival component of lifetime fitness, but the demographic consequences of fishery harvest are likely to indirectly affect the relative reproductive fitness of hooknose and jack males. First, the mean mating success of the jack-sneaking tactic is expected to decline with jack proportion through negative frequency-dependent sexual selection (Gross, 1985;Hutchings & Myers, 1988) as mediated by habitat conditions (DeFilippo et al., 2018). Second, changes in the form and strength of sexual selection likely favor hooknose males as breeding densities decline due to harvest. The jack life history is expected to be favored at high breeding densities because sneaking tactics are favored at high breeding densities in general (Roff, 1996) and because sexual selection on male body size in Coho changes from disruptive to directional to as breeding density declines (Fleming & Gross, 1994). Thus, the indirect effects of frequency-and/or density-dependent sexual selection are expected to favor hooknose males and act in the opposite direction to the effects of fishery-induced viability selection favoring jacks.
The fishery targeting hooknose males may also have affected jack proportions through ecological processes other than simple demographic adjustment. Fishery harvest reduced breeding densities (Figures 1b and 5b), and thus juvenile densities, which is expected to increase juvenile growth rates, conditions at age S A , and the proportion of males meeting condition-dependent thresholds for maturing as jacks (Grant & Imre, 2005;Rosenfeld, Leiter, Lindner, & Rothman, 2005;Vincenzi, Satterthwaite, & Mangel, 2012;Figure 2c). Alternatively, reduced escapement might lower juvenile growth rates by reducing levels of carcass-derived nutrients in streams (Heintz et al., 2004). While such ecological processes likely operate alongside and mediate any FIE changes in jack proportions, it is noteworthy that high breeding densities are associated with F I G U R E 4 (a) For the 30 populations with data from 1950, there was no tendency for interannual variation in fishery exploitation rate to be positively correlated with interannual variation in jack proportion between 1950 and 1993. (b) Jack proportion was not related to exploitation rate from 1950 to 1993. (c) Jack proportion increased gradually over time during the fishery. (d) Jack proportion increased between 1950 and 1993 in 27 of the 30 populations, and the rate of increase in jack proportion was unrelated to changes in three-year old density during the fishery  (1950−1993) high jack proportions (Young, 1999, Figure 5a). This may be because density-dependent sexual selection favoring jacks outweighs the effects of density-dependent reductions in juvenile growth. Also, the effect of intraspecific asymmetric competition tends not reduce growth rates of large, dominant juveniles destined to mature as jacks (Rosenfeld et al., 2005). The number and complexity of such processes make it unsurprising that we found no relationship between declines in adult density and increases in jack proportions during the fishery (Figure 4b).
We conclude that the data from Oregon coast Coho salmon populations offer compelling evidence for FIE. Identifying the specific evolutionary mechanism and quantifying the relative importance of FIE and ecological processes remain open challenges.

ACK N OWLED G EM ENTS
We thank the hundreds of ODFW employees who collected and managed the data used in this study. We thank Isabelle Côté, Martin Genner, and John Reynolds for comments on a previous version of the manuscript. Finally, congratulations and thank you to Louis Bernatchez for entering his seventh decade and inviting this contribution (Box 1).

DATA AVA I L A B I L I T Y S TAT E M E N T
The data herein are available upon request from the Oregon Department of Fish and Wildlife.