Human-mediated dispersal among aquatic ecosystems often results in biotic transfer between drainage basins. Such activities may circumvent biogeographic factors, with considerable ecological, evolutionary, and economic implications. However, the efficacy of predictions concerning community changes following inter-basin movements are limited, often because the dispersal mechanism is poorly understood (e.g., quantified only partially). To date, spatial-interaction models that predict the movement of humans as vectors of biotic transfer have not incorporated patterns of human movement through transportation networks. As a necessary first step to determine the role of anglers as invasion vectors across a land-lake ecosystem, we investigate their movement potential within Ontario, Canada. To determine possible model improvements resulting from inclusion of network travel, spatial-interaction models were constructed using standard Euclidean (e.g., straight-line) distance measures and also with distances derived from least-cost routing of human transportation networks. Model comparisons determined that least-cost routing both provided the most parsimonious model and also excelled at forecasting spatial interactions, with a proportion of 0.477 total movement deviance explained. The distribution of movements was characterized by many relatively short to medium travel distances (median = 292.6 km) with fewer lengthier distances (75th percentile = 484.6 km, 95th percentile = 775.2 km); however, even the shortest movements were sufficient to overcome drainage-basin boundaries. Ranking of variables in order of their contribution within the most parsimonious model determined that distance traveled, origin outflow, lake attractiveness, and sportfish richness significantly influence movement patterns. Model improvements associated with least-cost routing of human transportation networks imply that patterns of human-mediated invasion are fundamentally linked to the spatial configuration and relative impedance of human transportation networks, placing increased importance on understanding their contribution to the invasion process.

FEATURERiesgo ecológico de pesquerías con carnada: un nuevo enfoque de pesca selectiva RESUMEN: el uso de carnada viva es una norma cultural en varias jurisdicciones de Norte América. Debido a que los peces que se utilizan como carnada a veces son capturados junto con una mezcla de stocks silvestres, existe el potencial de que se vuelvan fauna de acompañamiento, lo que tiene como consecuencia que especies no objetivo sean reubicadas de forma inadvertida a través pescadores y de redes de distribución; por esta razón, como sucede en muchas pesquerías, el problema medular gira en torno a la pesca selectiva. En este trabajo se evalúa la selectividad de las pesquerías de carnada en Ontario, Canadá, haciendo énfasis en la prevalencia de la fauna de acompañamiento en la cadena productiva y en la propensión que existe por parte de los pescadores a reubicar especies no objetivo. La selectividad que existe para los stocks objetivo es intensa, sin embargo las asociaciones de peces que comercializan los pescadores incluyen especies de pesca deportiva, especies en peligro, especies invasivas y otras especies no objetivo. La combinación de fauna de acompañamiento, una enorme cantidad de viajes de pesca y un comportamiento riesgoso por parte de los pescadores, da como resultado una alta probabilidad de introducir una amplia gama de especies no objetivo que son contenidas incidentalmente. El manejo utilizando corredores, podría incrementar la selectividad, controlar la introducción de especies y mantener la integridad de las operaciones pesqueras con carnada a lo largo de Norte América. ABSTRACT:The use of live baitfish is a cultural norm in many jurisdictions across North America. Because baitfish are often harvested from mixed stocks in the wild, the potential for bycatch exists, leading to the inadvertent relocation of nontarget species via distribution networks and anglers; therefore, like many fisheries, core issues revolve around selective fishing. We assess selectivity of bait fisheries in Ontario, focusing on the prevalence of bycatch within the commercial supply chain and the propensity for nontarget species introductions by anglers. Selection for target stocks was strong; however, species assemblages in retail tanks and angler purchases included game, imperiled, invasive, and other nontarget species. The combination of bycatch, a large volume of angling trips, and risky angler behavior results in high probabilities of introducing the suite of nontarget species contained incidentally. Pathway approaches to management provide opportunities to increase selectivity, manage the risk of species introductions, and sustain the integrity of bait operations throughout North America.

Environmental factors affecting growth of the threatened eastern sand darter ( Ammocrypta pellucida (Putnam, 1863)) were examined using specimens sampled from the northern edge of its range to determine the species’ critical habitat. Length-at-age increments were determined from scale samples as surrogates for growth rates based on back-calculated lengths using the Fraser–Lee method. During the first year of life, 82% of total length is attained, suggesting considerable energetic partitioning towards reproduction following age-0. Positive relationships between age-0 length increments and sand substrates and between age-0 length increments and mean annual channel discharge indicated greatest first-year growth within sand-dominated, high-discharge habitats. Environmental factors that occurred at coarse spatial and temporal levels (i.e., mean annual channel discharge) explained more of the growth variability among eastern sand darters than those occurring at fine levels (i.e., site-level substrate composition). This study indicates that environmental factors can be used to explain variability in cohort-structured population and site-level growth of eastern sand darters.

Captive breeding programs are widely applied by conservation practitioners as a means of conserving, reintroducing, and supplementing populations of imperilled freshwater fishes and mussels. We conducted a systematic map to provide an overview of the existing literature base on the effectiveness of captive breeding and release programs. A key finding is that there is limited evaluation of the effectiveness of such programs at all three stages (i.e., broodstock collection, rearing/release methods, and post-release monitoring). We identified clusters of evidence for supplementation evaluations related to rearing/release methods for fish growth and survival metrics, and the monitoring stage for fish genetic diversity, growth, and survival metrics, primarily focused on salmonids. However, many studies had inadequate experimental designs (i.e., lacked a comparator). Overall, there was a paucity of studies on the effectiveness of captive breeding programs for imperilled freshwater mussels, highlighting the need to make such information broadly available when studies are undertaken. Outputs from this systematic map (i.e., the map database and heatmaps) suggest that the effectiveness of captive breeding and release programs requires further systematic evaluation.

Freshwater ecosystems are among the most threatened environments on our planet. Disturbances across the terrestrial landscape accrue within freshwater ecosystems and, combined with global stressors such as climate change and invasive species, create a complex situation for recovering imperilled fishes. Given the drastic global decline of freshwater fishes, similarly extreme efforts are needed for their conservation and recovery — repatriation represents one such opportunity. Species repatriation describes the act of releasing a species in areas where extirpation has occurred. Paradoxically, a long history of fish introductions for recreational purposes exists, yet examples of repatriation for imperilled fishes are relatively rare compared with terrestrial species. Stemming from the restoration and species introduction literature, we identify five ecological themes to consider when evaluating repatriation potential of freshwater fishes and suggest that repatriation represents the “drastic” approach needed to achieve meaningful conservation milestones.

Life‐history and other vital rate information is important for effective species conservation by informing demographic trends and aspects of population viability. However, species‐specific information is lacking for many small‐bodied freshwater fishes, which can make it difficult to relate demographic trends to threats or recovery actions. Silver Shiner (Notropis photogenis), a small‐bodied species listed as Threatened under Canada's Species at Risk Act, lacks well‐informed age and vital rate information. We aged 254 Silver Shiner using opercular and otolith structures and determined that Silver Shiner is short‐lived, with a probable maximum age of 4. Three years of field collections (2017–2019) were used to parameterize growth models and to estimate adult (age 1–3+) mortality rates. Silver Shiner captured in urban reaches exhibited altered growth and higher mortality compared to non‐urban reaches, indicating that urbanization may have demographic impacts on the species. Results highlight the importance of detailed age and vital rate information for assessing threats and informing effective conservation approaches for imperilled fishes. Furthermore, the potential negative impact of urbanization on the growth and survival of this species highlights the urgency of better understanding the influence of urbanization on small‐bodied freshwater fishes in general.

Organisms living in environments with oscillating temperatures may rely on plastic traits to sustain thermal tolerance during high temperature periods. Phenotypic plasticity in critical thermal maximum (CTmax) is a powerful thermoregulative strategy that enables organisms to adjust CTmax when ambient temperatures do not match thermal preference. Given that global temperatures are increasing at an unprecedented rate, identifying factors that affect the plastic response in CTmax can help predict how organisms are likely to respond to changes in their thermal landscape. Using an experimental thermal chamber in the field, we investigated the effect of short-term acclimation on the CTmax and thermal safety margin (TSM) of wild-caught redside dace, Clinostomus elongatus, (n = 197) in a northern population in Two Tree River, Ontario. Streamside CTmax trials were used to identify the maximum temperature at which redside dace maintain equilibrium, providing a powerful tool for understanding how thermal stress affects individual performance. CTmax and TSM of redside dace were sensitive to changes in temperature, regardless of season, suggesting that temperature pulses caused by climate change or urban activities can impose negative fitness consequences year round. Interestingly, an individual’s recent thermal history was more influential to its thermal tolerance than the current ambient water temperature. While the CTmax of redside dace increased with body size, the effect of body size on TSM remains unclear based on our models. The results provide insight into the thermal performance of redside dace that, to date, has been difficult to assess due to the species’ rarity and lack of suitable streamside protocols.

Fishes are among the most threatened taxa in Canada with over 70 species, subspecies, and (or) designatable units presently listed for protection under the Species at Risk Act (SARA). Protecting these species requires a diverse set of strategies based on the best-available data and information. One approach identified under SARA and in Canadian federal recovery strategies for improving the status of SARA-listed fishes is species reintroduction, which involves the release of individuals into areas from which they have been extirpated with the goal of re-establishing self-sustaining populations. The success of reintroduction relies on a comprehensive understanding of species ecology and life history, with considerations around population genetics and genomics. However, SARA-listed species are some of the most poorly known species in Canada due to their rarity and relative lack of research investment prior to the enactment of SARA. As a result, SARA-listed species have the most to lose if reintroduction activities are not carefully researched, planned, and executed. Therefore, the purpose of this review is to present an accessible summary on the state of reintroduction science for SARA-listed fishes in Canada with the hope of motivating future research to support reintroduction activities. We focus our review on 14 SARA-listed freshwater or anadromous fishes identified as candidates for reintroduction in federal recovery strategies. We follow the species-specific summaries with guidance on how basic research questions in population ecology, habitat science, and threat science provide a critical foundation for addressing knowledge gaps in reintroduction science. Subsequently, we identify the importance of genetic and genomic techniques for informing future research on the reintroduction of SARA-listed species. We conclude with recommendations for active, experimental approaches for moving reintroduction efforts forward to recover Canadian fishes.