Intracoelomic Implantation of Transmitters in Longnose Gar

Fish in the family Lepisosteidae (hereafter, gars) have unique ganoid scales that pose inherent challenges to implanting electronic tags in their coeloms for telemetry studies. In this paper we outline a unique approach to conducting laparotomic surgery in gars, with a focus on the Longnose Gar Lepisosteus osseus. An electric rotary tool with a circular cutting blade was used to cut through the scales, and the same tool, with a drill bit, was used to create holes through which to run the suture material. The final incision into the body cavity was made with a scalpel, and the incision was expanded using surgical scissors. Using a passive acoustic telemetry array, the survival of 12 of 15 tagged Longnose Gars was confirmed over a 123-d period based on their detection at receivers outside of their areas of capture and release. Two individuals were recaptured 17-19 weeks postsurgery and showed complete healing of the wounds with limited evidence of scarring. This approac

On the Electroimmobilization of Fishes for Research and Practice: Opportunities, Challenges, and Research Needs

As a result of growing demand for immediate-release sedatives in fisheries research, electroimmobilization has been receiving increasing attention due to its superior induction and recovery times and practicality, particularly under field conditions. However, a review of electroimmobilization and its role in fisheries science has not been previously conducted. Here we describe and differentiate the various forms of electroimmobilization and attempt to standardize relevant terminology. We review the known efficacy of electroimmobilization of fish and summarize the current available knowledge on this topic while identifying major knowledge gaps. Although more information is needed to determine optimal forms and settings for different species, life history stages, and environmental variables, electroimmobilization is a useful tool for fish handling that equals or surpasses the capabilities of chemical sedatives without exacerbating (and sometimes reducing) the negative consequences associated with chemical sedatives and fish

Size-Dependent Consequences of Exogenous Cortisol Manipulation on Overwinter Survival and Condition of Largemouth Bass

Little is known about the size-dependent consequences of stressors on wild animals, which is particularly relevant during winter where size-specific trends in survival are common. Here, exogenous cortisol manipulation was used to investigate the effect of a physiological challenge on overwinter mortality and spring condition of largemouth bass (Micropterus salmoides) across a range of body sizes. Fish were wild-caught in the fall, assigned into either control or cortisol manipulated treatments, and held in replicated experimental ponds. For bass that survived the winter, length, mass, and health metrics (e.g., gonadosomatic index [GSI], hepatosomatic index [HSI], and water content) were determined in the spring. Winter survival was marginally lower for cortisol treated bass; however, there was no influence of initial length, mass, or condition on overwinter survival. When bass were grouped by size, survival was significantly higher for bass 300–350 mm in length compared to those <200 mm. The treatment did not strongly influence spring health metrics, suggesting that largemouth bass that survived the winter were able to recover from the effects of the cortisol elevation. Initial size and sex were linked to some spring health metrics, with large females having the highest GSI and HSI scores. Overall, results from this study do not support the notion that there are size-dependent responses to cortisol manipulation in a teleost fish. Rather, this type of physiological challenge may modulate the natural rates of winter mortality that are primarily driven by starvation and predation, independent of body size, in subadult and adult largemouth bass

Comparing Immobilization, Recovery, and Stress Indicators Associated with Electric Fish Handling Gloves and a Portable Electrosedation System

Fish sedation facilitates safer handling of fish during scientific research or fisheries assessment practices, thus limiting risk of injury to fish and reducing stress responses. In recent years, there has been growing interest in using electricity to sedate fish; two methods include (1) lower-voltage, non-pulsed-DC fish handling gloves (FHGs) that tend to only sedate fish while the gloves are touching the animal; and (2) a comparatively high-voltage, pulsed-DC Portable Electrosedation System (PES) that leads to galvanonarcosis. This study compared the physiological consequence

Spatiotemporal ecology of juvenile Muskellunge (Esox masquinongy) and Northern Pike (Esox lucius) in upper St. Lawrence River nursery bays during their inaugural fall and winter

Understanding the spatial ecology of juvenile freshwater fish beyond summer months is an essential component of their life history puzzle. To this end, declines in the natural populations of sympatric Muskellunge (Esox masquinongy) and Northern Pike (Esox lucius) in the upper St. Lawrence River prompted study of spatiotemporal patterns and habitat requirements associated with earlier life stages of these congeneric, freshwater predators in fall and overwinter periods. Over 75 age-0 esocids were tagged and passively monitored using acoustic telemetry in four nursery embayments in fall and winter months from 2015 and 2017 months to elucidate spatiotemporal ecology and test hypotheses related to emigration. Presence, residency, space and habitat use were assessed and modelled against key environmental (i.e. water temperature and level) and biological (total length) covariates using mixed effect models. Muskellunge were found to spend more time in deeper, littoral regions with canopy-forming, submerged aquatic vegetation while Northern Pike aggregated in the deepest, highly vegetated region of their nursery embayment. Results suggest fish may exhibit transitionary movements in fall months and may span outwards into nearshore regions along the main river channel. Studies informing coastal restoration initiatives to increase Muskellunge production are encouraged to assess sympatric habitat use relative to prominent embayment structures and further explore depth partitioning by these young predators. With a substantial influence from water-level regulation on use of nursery habitat, future studies must work in concert with management plans aimed at producing more natural riverine cycles and thus increased recruitment of Esox species

Comparative thermal biology and depth distribution of largemouth bass (Micropterus salmoides) and northern pike (Esox lucius) in an urban harbour of the laurentian great lakes

Understandinghowindividuals are distributed in space and time, as well ashowthey interact with dynamic environmental conditions, represent fundamental knowledge gaps for many fish species. Using acoustic telemetry tags, we monitored the temperatures and depths used by northern pike (Esox lucius L., 1758) and largemouth bass (Micropterus salmoides (Lacepède, 1802)) in Toronto Harbour (Lake Ontario). Northern pike and largemouth bass had similar thermal experiences throughout the year, except during summer, when northern pike were observed in cooler waters than largemouth bass. Both species used different depths throughout the year, with northern pike occupying deeper depths. Statistical modelling indicated that depth usage was influenced by all variables (season, species, and body size) and interactions between them, whereas thermal preferences were influenced by the main effects and interactions between species:season and species: body size. Both species were observed at temperatures warmer than those in the vicinity of nearby telemetry stations, but as station temperatures exceede