Search

Annual recruitment in fish is undoubtedly impacted by a vast number of biotic and abiotic factors. That is especially the case for fish species such as the black bass (species in the genus Micropterus), where there is extended parental care. Although much focus has been given in the past on determining the roles that many of these factors (e.g., temperatures, wind, flow rates, and habitat change) play in determining recruitment among the back basses, little attention has been given to assessing what role reproductive success plays in that determination. To address this question, we conducted a long-term study on two adjacent smallmouth bass (SMB) Micropterus dolomieu Lacepede, 1802 populations in eastern ON to assess the relationship between annual fry cohort size (FCS) (i.e., population-wide reproductive success) and annual recruitment. To measure population-wide annual FCS, we used snorkel surveys to conduct a complete census of nesting SMB males during the spawn from 1990 to 2015. During those surveys, we quantified mating success, determined which nests were successful or not, and calculated the number of independent fry produced each year by summing those numbers across all successful nests. Summer snorkel surveys from 1991 to 2016 assessed annual recruitment through visual counts of age 1+ juveniles. Results demonstrated a highly significant, positive, linear relationship between annual FCS and annual recruitment. Key words: smallmouth bass, Micropterus dolomieu, annual recruitment, reproductive success, angling, Introduction Smallmouth bass (SMB) Micropterus dolomieu Lacepede, 1802 and largemouth bass M. salmoides (Lacepede, 1802), two of the species in the genus commonly referred to as black bass, are both [...]

We conceptualize and test a non-intrusive barrier, comprised of an oblique bubble screen (OBS) oriented at an angle to the mean flow, to prevent the downstream dispersal of invasive carp egg surrogates. Three surrogates of different densities and diameters were tested. Secondary flows created by the OBS were tuned to redirect surrogate eggs to facilitate their capture. Surface particle image velocimetry and acoustic Doppler velocimetry were used to characterize secondary flows. We assessed the influence of airflow rate, OBS angle, mean flow velocity, and surrogate density on particle redirection. In general, redirection efficiency improves by increasing the OBS angle with respect to the cross-section. At a mean flow velocity of 0.75 metres per second (m/s), the OBS system redirected up to 60% (%) of positively buoyant particles (specific gravity SG = 0.9, and diameter d = 7.09 millimetres [mm]) and 40% of semi-buoyant particles (SG = 1.001, d = 3.1 mm). Negatively buoyant particles (SG = 1.04, and d = 5.90 mm) were redirected by the physical structure of the diffuser rather than by OBS-induced flow. The study shows that an OBS system can be used to effectively redirect carp-egg surrogates over a wide range of particle sizes and densities, allowing for selective targeting of undesired particles in streams. [ABSTRACT FROM AUTHOR]

Restoration practices aimed at fish habitat enhancement often include installation of instream structures. However, mixed outcomes have been reported regarding structure effectiveness, while mechanisms underlying success remain unclear. The interactions between fish and flow conditions generated by instream structures and their subsequent impact on fish energetics may provide some insight. This study seeks to quantify how restoration structures, simulated by cylinders in three orientations, alter the energetics and swimming stability of smallmouth bass (Micropterus dolomieu). Accelerometers measured swimming stability while a respirometer measured energy expenditure at multiple velocities. Particle image velocimetry was used to characterize flow fields behind structures. Structures generated flow conditions that benefited fish energetically. Fish had a smoother gait and expended less energy when swimming near a structure, regardless of its orientation. Benefits varied with flow conditions; reductions in energy expenditure were especially apparent at high flow velocities. Results suggest that restoration structures may be most energetically beneficial in stream systems with consistently high velocities and inform restoration by indicating flow conditions in which structures provide the greatest energetic benefits for fish. Les pratiques de restauration visant a ameliorer les habitats de poissons comprennent souvent l'amenagement d'ouvrages dans les cours d'eau. Des resultats mitiges ont toutefois ete rapportes quant a l'efficacite de tels ouvrages, et les mecanismes qui sous-tendent cette derniere demeurent mal compris. Les interactions entre les poissons et les conditions d'ecoulement produites par les ouvrages dans les cours d'eau et leur incidence subsequente sur l'energetique des poissons pourraient fournir des indices. L'etude tente de quantifier comment des ouvrages de restauration, simules par des cylindres de trois orientations differentes, modifient l'energetique et la stabilite de nage d'achigans a petite bouche (Micropterus dolomieu). Des accelerometres sont utilises pour mesurer la stabilite de nage et un respirometre, pour mesurer la depense energetique a differentes vitesses. La velocimetrie par images de particules est utilisee pour caracteriser les champs d'ecoulement en arriere des ouvrages. Ces derniers produisent des conditions d'ecoulement avantageuses pour les poissons sur le plan energetique. Les poissons nagent de maniere plus stable et depensent moins d'energie a proximite d'un ouvrage, peu importe son orientation. Les avantages varient selon les conditions d'ecoulement; des reductions de la depense energetique sont particulierement evidentes a de hautes vitesses d'ecoulement. Les resultats portent a croire que les ouvrages de restauration pourraient offrir les plus grands avantages sur le plan energetique dans les reseaux hydrographiques caracterises par des vitesses d'ecoulement uniformement elevees, et fournissent des renseignements utiles pour la restauration en indiquant les conditions d'ecoulement dans lesquelles ces ouvrages offrent aux poissons les plus grands avantages energetiques. [Traduit par la Redaction], Introduction Freshwater ecosystems worldwide are currently at risk due to anthropogenic degradation that imperils water quality, connectivity, and biodiversity (Gleick 2003; Dudgeon et al. 2006; Vorosmaity et al. 2010). The [...]

The potential benefits of physiology for conservation are well established and include greater specificity of management techniques, determination of cause-effect relationships, increased sensitivity of health and disturbance monitoring and greater capacity for predicting future change. While descriptions of the specific avenues in which conservation and physiology can be integrated are readily available and important to the continuing expansion of the discipline of 'conservation physiology', to date there has been no assessment of how the field has specifically contributed to conservation success. However, the goal of conservation physiology is to foster conservation solutions and it is therefore important to assess whether physiological approaches contribute to downstream conservation outcomes and management decisions. Here, we present eight areas of conservation concern, ranging from chemical contamination to invasive species to ecotourism, where physiological approaches have led to beneficial changes in human behaviour, management or policy. We also discuss the shared characteristics of these successes, identifying emerging themes in the discipline. Specifically, we conclude that conservation physiology: (i) goes beyond documenting change to provide solutions; (ii) offers a diversity of physiological metrics beyond glucocorticoids (stress hormones); (iii) includes approaches that are transferable among species, locations and times; (iv) simultaneously allows for human use and benefits to wildlife; and (v) is characterized by successes that can be difficult to find in the primary literature. Overall, we submit that the field of conservation physiology has a strong foundation of achievements characterized by a diversity of conservation issues, taxa, physiological traits, ecosystem types and spatial scales. We hope that these concrete successes will encourage the continued evolution and use of physiological tools within conservation-based research and management plans.

Carbon dioxide (C[O.sub.2]) in water has been explored for use as an invasive species deterrent system. To date, studies have not determined C[O.sub.2] avoidance by fish in flowing water, and this is a necessary step before an operational deterrent system can be implemented. The objective of the study was to define how flowing water influences the response of bighead carp (Hypophthalmichthys nobilis) to continuous plugs of C[O.sub.2]. A choice experiment by which C[O.sub.2] was injected into channels of an annular flowing water flume was completed. In trials when C[O.sub.2] was injected into the inner vein, fish spent less time in the vein when compared with control conditions. An increased amount of lateral movements and reduced performance were also observed when fish were exposed to elevated C[O.sub.2]. The study demonstrates that bighead carp in flowing water enriched with C[O.sub.2] move away, a finding consistent with static water experiments. Le dioxyde de carbone (C[O.sub.2]) dans l'eau a ete etudie en vue de son utilisation comme systeme de dissuasion d'especes envahissantes. A ce jour, les etudes n'ont pas etabli s'il y a evitement du C[O.sub.2] par les poissons dans l'eau mouvante, bien qu'il s'agisse d'une etape prealable necessaire a la mise en reuvre de tout systeme de dissuasion. L'objectif de la presente etude etait d'etablir comment l'eau mouvante influence la reaction de carpes a grosse tete (Hypophthalmichthys nobilis) a des bouffees continues de C[O.sub.2]. Une experience de choix dans laquelle du C[O.sub.2] est injecte dans les chenaux d'un canal annulaire d'eau mouvante a ete realisee. Dans les essais, quand du C[O.sub.2] etait injecte dans la veine interieure, les poissons y passaient moins de temps que dans les conditions de reference. Plus de deplacements lateraux et une performance plus faible etaient aussi observes quand les poissons etaient exposes a des concentrations elevees de C[O.sub.2]. L'etude demontre que les carpes a grosse tete dans de l'eau mouvante enrichie en C[O.sub.2] s'en eloignent, une constatation qui concorde avec les resultats d'experiences en eau stationnaire. [Traduit par la Redaction], Introduction Aquatic invasive species (AIS) are prevalent across the planet, and management tools are often used to control their spread (Vander Zanden and Olden 2008). Specifically, for freshwater fish, unfettered [...]

Heatwaves are becoming more frequent and intensified with climate change. Freshwater ecosystems are among the most threatened, within which, differing responses between cool- and warmwater species to heatwaves can lead to fundamental changes in communities. Physiological experiments can identify potential mechanisms underlying the impacts of such heatwaves on fish communities. In the current study, we quantified the oxygen consumption rate, aerobic scope and swimming performance of cool- and warmwater fish species following the simulation of short-term heatwaves currently occurring in streams in the Midwestern United States. The coolwater predator walleye (Sander vitreus) showed clear thermal disadvantages relative to the warmwater predator largemouth bass (Micropterus salmoides), based on a high metabolic cost during the heatwave, low metabolic activity when encountering prey, and reduced swimming performance following the heatwave. Largemouth bass also showed a thermal advantage relative to the warmwater prey fathead minnow (Pimephales promelas) related to swimming performance and energetic costs, highlighting differing thermal responses between predators and prey. This study demonstrates the importance of considering short-term extreme thermal events in the response of aquatic communities to climate stressors. [ABSTRACT FROM AUTHOR]

Reduced food availability increases the capture of several fish species, although the mechanisms responsible for how food resources result in increased capture are undefined. Our objective was to quantify the mechanism by which food availability might influence the angling vulnerability of muskellunge (Esox masquinongy). We assessed capture rates in the field under different food levels, quantified the behaviors of muskellunge that were either fed or food deprived, and determined if appetite‐related hormones leptin and ghrelin affected fish behavior. Catch rates of fasted muskellunge were more than twice as high as those of fed muskellunge. However, food deprivation and hormonal treatments did not influence laboratory behavior, which suggested that catch rates of food‐deprived muskellunge increased because fish were more receptive to lures. Furthermore, an ecosystem approach should be used to consider forage as a component of management goals. [ABSTRACT FROM AUTHOR]