AbstractObjectiveState‐space models are a flexible modeling approach and are often fit to ecological time series data exhibiting temporal autocorrelation. Traditionally, angler effort data collected using on‐site creel surveys are analyzed using design‐based methods. With some exceptions, state‐space models are rarely used to model creel survey data that are also generally a time series of temporally autocorrelated counts.MethodsIn this study, we demonstrated how to fit state‐space models to a time series of angler counts in 11 sections of three trout fisheries in Idaho. The basic model was extended to make inference about processes that may regulate angling dynamics, such as “population growth rate” of angling effort and recreational carrying capacity.ResultEstimated angling effort varied from 21,179 h in the lowermost section of the Henrys Fork Snake River to 199,457 h in the uppermost section of the South Fork Snake River. The finite population growth rate of angling effort was 1.82 when transitioning from a weekday to a weekend, suggesting that angling effort was 1.82 times greater, on average, on Saturdays than on Fridays, and the population growth rate was 0.38 (i.e., 0.38 times smaller) when transitioning from a Sunday to a Monday. Estimated carrying capacity among fishery sections varied from 129 daily hours of angling effort on the Big Lost River to 693 h on the middle section of the South Fork Snake River. Carrying capacity was 1.88 times higher on fishery sections that had ≥0.5 access points/km than on sections with <0.5 access points/km.ConclusionThe state‐space models used in this study can be modified or extended to fit a variety of data types or can be used to evaluate additional hypotheses regarding the angling process.

AbstractObjectiveWe hypothesized online text can provide insight into the satisfaction of anglers who post on online forums.MethodsWe applied sentiment analysis to almost 3 years of management‐related posts on online angling forums to estimate the long‐term satisfaction of Walleye Sander vitreus anglers in nine U.S. states.ResultSentiment varied fourfold among states. Consistent with the literature, our random forest model found that sentiment increased with angler density, bag limit, and season length. Relatively unimportant factors were fishing license cost, the frequency of special Walleye regulations, the degree to which management agencies communicated with anglers through social media, and the importance of angling to the state economy.ConclusionOur results support the hypothesis that online text can provide insight into the satisfaction of anglers who post on online forums. This work contributes to a growing interest in exploring and validating the use of online data within systems of harvest management and governance.

AbstractObjectiveIndividual habitat preference can reduce intraspecific competition for resources and may differ between age groups, sexes, and adult phenotypes. The Channel Catfish Ictalurus punctatus is a widespread species occurring in diverse freshwater habitats. This species displays breeding philopatry, returning to nesting sites occupied in previous years. Larger Channel Catfish tend to nest in the main channels of large rivers, whereas smaller fish tend to prefer smaller tributaries. The purpose of our study was to determine whether this habitat segregation potentially associated with habitat preference affects the genetic structure of a population. We hypothesized that spatial segregation of breeding sites in the Ottawa River and its smaller tributaries at Lac des Chats reduced gene flow within the population, resulting in genetically differentiated demes associated with lacustrine‐like and fluvial habitats.MethodsMicrosatellite allelic data was collected from 162 Channel Catfish.ResultWe found little genetic variation between the Ottawa, Mississippi, and Madawaska rivers. Furthermore, our analyses suggested that the sampled specimens comprised one panmictic population. Fish from one site in the Ottawa River, however, were significantly differentiated from fish from a nearby site also in the Ottawa River as well as from fish from the Mississippi River tributary.ConclusionGiven that fish from sites further up the Ottawa River were not differentiated from fish from these sites, it is unlikely that geography can account for the differences observed; rather, assortative mating may explain the differentiation. We propose that panmixia within the population is caused by ontogenetic changes in habitat selection, straying individuals, or sex‐biased dispersal and philopatry.

AbstractKokanee, the non‐anadromous life‐history form of Oncorhynchus nerka, use lacustrine habitat in watersheds draining into the north Pacific Ocean. Kokanee also have been widely introduced into reservoirs following impoundment of rivers consequent to the construction of hydroelectric dams. Genetically divergent subpopulations of Kokanee should be identified and evaluated when implementing watershed‐level fishery management strategies. We analyzed the genetic population structure of Kokanee in the Williston watershed, north‐central British Columbia, where native populations were present in the reservoir and headwater lakes prior to stocking Columbia River‐origin fish in the 1990s. Using microsatellite markers, we determined that native Williston Reservoir Kokanee were divergent from only one of the headwater lake populations. Native populations in headwater lakes remain entirely separate from the reservoir populations, and there was no indication of past or current introgression with the introduced stock. We identified all fish collected from 2006 to 2019 as introduced Columbia River‐origin genotypes, and there was no evidence of genetic divergence by spawning location. As native Williston Kokanee have not been sampled from the reservoir in survey efforts since 2000, it is likely that this population has been extirpated from the reservoir perhaps through competition with the introduced Columbia River‐origin lineage.

AbstractMovement of fish past dams can be facilitated by dedicated fish passage structures, navigational locks, and crested spillways, with the efficacy of a passage structure depending strongly on the nature of the systems (height of the dam, flow rate, etc.) and the fish's behavior and swimming capability. However, once past a dam whether by the use of a mitigation structure or due to active translocation, fish encounter a different habitat upstream versus in the tailrace, potentially affecting their ability to continue their upstream migration. Here we had two objectives: First, we determined whether Paddlefish Polyodon spathula that successfully passed a structure continued on their upstream migration. Because assuring passage by tagged fish required that we move fish past the dam, our second objective was to determine whether translocated fish exhibited fallback behavior (downstream drift or movement post‐release that would compromise their continued migration). We used both active and passive telemetry to quantify post‐passage movements of tagged and translocated Paddlefish. Fish translocated above Claiborne Lock and Dam (CLD) exhibited up‐river movements once translocated and exhibited no fallback (i.e., downstream movement with delayed or no continuation upstream). Timing of movement relative to spawning periods did not influence initial fish movement or the likelihood of reaching the next upstream dam (Millers Ferry Lock and Dam; MFLD, approx. 100 river km upstream) within the first 30‐days of observation, but more fish tagged and released during the early pre‐spawning period made it within 4.83 km of MFLD (the location of our closest receiver below MFLD) than did fish from pre‐spawning or spawning periods. Fish released above CLD had a lower probability of being subsequently detected downstream of their release sites compared to fish released below CLD. Our findings support that Paddlefish will continue their upstream migration once past a structure despite changes in habitat.

AbstractSupplementation of naturally‐spawning populations by the addition of hatchery‐spawned individuals is commonly conducted for recovery of threatened and endangered populations and to support harvest opportunities. We present an analysis of steelhead, the anadromous form of Rainbow Trout (Oncorhynchus mykiss), returning to an integrated supplemented population in Southwest Washington over the course of 15 years. The goal of the supplementation program was to evaluate whether use of a juvenile captive broodstock and an integrated paradigm could be used to increase adult returns, while avoiding negative genetic impacts to the population. Estimates of relative reproductive success (RRS) for fish spawned in the hatchery ranged from 2.4 for hatchery‐origin females to 6.4 for natural‐origin males, indicating that fish spawned in the hatchery produced more returning adult progeny than did fish allowed to spawn in the natural environment. We observed a slight reduction in reproductive success (RS) for hatchery‐origin (relative to natural‐origin) fish when spawning in the natural environment, but the difference was non‐significant for males and marginally significant for females. In contrast to the relatively weak relationship between RS and origin (male P = 0.347, η2 = 0.008; female P = 0.066, η2 = 0.037), we observed a strong relationship between RS and return year (male P < 0.001, η2 = 0.896; female P < 0.001, η2 = 0.867) (i.e., hatchery‐ and natural‐origin fish did well or poorly together each year). Hatchery origin fish exhibited reduced genetic diversity, as well as evidence of increased temporal population structure among hatchery fish. We suspect the latter is an artifact of culture practices that reduce diversity in age at smoltification. We conclude that the program was successful in achieving an increase in adult return, but not in avoiding negative genetic effects on the population, and that any lasting impacts of supplementation remain to be determined.

AbstractObjectiveSeaward migration and early marine residence are periods of high mortality in the lifecycle of Pacific salmon Oncorhynchus spp. The conservation of these species requires knowledge of habitat use patterns during early life to address survival bottlenecks. Using new miniaturized transmitters (V3 307‐kHz tag; Innovasea Systems), we investigated the association between biological and environmental factors and the residence behavior of subyearling Chinook Salmon Oncorhynchus tshawytscha in a fjord estuary in British Columbia.MethodsTagged wild subyearling Chinook Salmon (n = 49; 67–95 mm) were experimentally released into an estuary. Using time‐to‐event analysis and model selection, we evaluated the association between biological (size, growth, day of release) and environmental (temperature, salinity, depth, discharge, tide direction) factors and estuary residence patterns.ResultOf the 49 fish released, 36 were inferred to have exited the estuary successfully. In this sample of subyearling Chinook Salmon, the median residence duration was estimated to be 11.2 days (95% CI = 6.5–15.5). We found tide direction and salinity to be important factors influencing the probability of a fish leaving the estuary. Fish were 75% more likely to leave the estuary on an ebb tide. Higher salinity also increased the probability of a fish leaving the estuary. Fish successful in leaving the estuary displayed either direct or indirect movement patterns in the estuary, with most fish (71%) being indirect movers that made multiple trips upstream and downstream. Within the estuary, most movements occurred at night (76%), regardless of tide direction.ConclusionThis study provides the first direct measure of estuary residence duration in wild subyearling Chinook Salmon and a valuable description of movement ecology in this age‐class of fish. While this was a small study in a single year, our results indicate this estuary is likely a stopover habitat for larger subyearlings. Studies indicating the use of habitats by specific populations, as presented here, are integral to the design of habitat‐based conservation measures for mobile species.

AbstractObjectiveWe investigated foraging success, diet composition, and the abundances of various prey taxa in the diets of larval Freshwater Drum Aplodinotus grunniens across a gradient of bigheaded carp (Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix) relative abundance and in relation to zooplankton density, temperature, discharge, and larval fish densities in the upper Mississippi River (UMR).MethodsWe sampled fish larvae and zooplankton every 10 days (May–August 2017 and 2018) from UMR Pools 14, 16, and 18–20; collected environmental data from nearby gauging stations; and assessed bigheaded carp relative abundance.ResultCrustacean zooplankton abundance was positively related to larval foraging success. Copepods were the dominant prey, but larvae also consumed large proportions of rotifer eggs and benthic insect larvae. Bigheaded carp presence and catch per unit effort were positively associated with increased larval consumption of atypical prey (rotifer eggs and aquatic insect larvae) and cyclopoid copepods. Cladocerans were the rarest prey consumed by larvae in pools where bigheaded carp were present, but they were more frequently consumed in pools where bigheaded carp were absent. In addition to bigheaded carp abundance, river discharge was negatively associated with larval consumption of cladocerans, aquatic insect larvae, and rotifers; water temperature was negatively associated with the consumption of copepods and cladocerans; and rotifer abundance was positively associated with their consumption.ConclusionWe suggest that bigheaded carp alter larval fish diets to prey that may be less energetically beneficial, which can have implications for larval growth and survival.

AbstractObjectiveFisheries managers and anglers have expressed concerns regarding warmwater angling mortality, representing a need to evaluate mortality rates at various water temperatures and multiple latitudes. Up to 97% of Muskellunge Esox masquinongy caught by anglers are released, and previous research on catch and release (C&R) for Muskellunge has suggested relatively low mortality rates (0–5%). However, those studies were all conducted within the range of water temperatures that are thermally optimal for Muskellunge and generally at water temperatures less than 25°C. As many Muskellunge populations routinely experience temperatures greater than 25°C during the summer months our objective was to quantify warmwater (>25°C) C&R mortality rates in Muskellunge.MethodsWe collected 102 adult Muskellunge (>760 mm) and stocked them into and identify factors influencing mortality by using experimental ponds. Adult Muskellunge (n = 102) were stocked into eight earthen or plastic‐lined flow‐through ponds (0.06–0.71 ha) at densities less than 16 fish/ha. Muskellunge (n = 50) were angled by utilizing specialized Muskellunge fishing gear at water temperatures of 19.6–32.6°C, with 32 fish being caught at temperatures exceeding 25°C. After being angled, fish were closely monitored for 2 weeks to assess mortality; fish that remained uncaught during the experiment were used as controls (n = 53).ResultMortality was greater for angled fish (30.0%) than for control fish (11.3%). Differences in C&R mortality were compared across a range of temperature regimes using Firth logistic regression. Five‐day cumulative temperature and net time were positively related to the probability of mortality, but size and sex were unrelated to mortality. Increasing C&R mortality with temperature was mitigated somewhat by lower catch rates at higher temperatures. Mortalities per 100 angler‐hours were 0 at <25°C, 4.98 at 25.00–27.49°C, 2.48 at 27.5–30.0°C, and 1.17 at >30°C.ConclusionRecent field studies have identified the importance of thermal refuge in mitigating summer C&R mortality of Muskellunge. This study identified specific temperature conditions responsible for elevated mortality in the absence of refugia. Although increasing temperatures above 25°C led to increasing C&R mortality in our ponds, lower catchability seemingly provided some mitigation. The interactive effects of thermal refugia and catch rates with temperature warrant further investigations into population‐level effects at varying levels of exploitation.

AbstractObjectiveWe investigated environmental variables associated with spawning migration behavior for a dual‐spawning population of endangered Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus in the Great Pee Dee River, South Carolina.MethodsFrom 2016 to 2021, 147 Atlantic Sturgeon were captured, implanted with acoustic transmitters, and monitored using a stationary array of 40 receivers located every 5–20 km along a 302‐km section of the Great Pee Dee River from the river mouth at Winyah Bay to the first movement barrier at Blewett Falls Dam, North Carolina.ResultWe observed 47 Atlantic Sturgeon attempting 74 spring migrations and 39 Atlantic Sturgeon attempting 76 fall migrations across 4 years of telemetry observations (2018–2021). Mixed‐effects models indicated that discharge interacted with water temperature to affect both migration initiation and upriver movement, and these interactions differed between the spring and fall runs. Spring runs were cued by rising temperatures and high river discharge, whereas fall runs were cued by falling temperatures and low discharge. Within migrations, spring‐run fish migrated further upriver when discharge was falling, and fall‐run fish moved further upriver when discharge was rising. Overall, fall‐run sturgeon migrated significantly further upriver than spring‐run sturgeon.ConclusionDifferences in migratory behavior between the two runs suggest potentially unique adaptations to ambient river conditions during the respective spawning seasons. Identifying the environmental factors that drive—and thereby limit—Atlantic Sturgeon migrations in the Great Pee Dee River informs regional recovery efforts and highlights the importance of studying and managing this species at the population level.