Karen J. Murchie

Locomotory activity and depth distribution of adult great barracuda (Sphyraena barracuda) in Bahamian coastal habitats determined using acceleration and pressure biotelemetry transmitters

Documenting free-swimming fish in their natural environment using acoustic transmitters equipped with acceleration and pressure sensors may contribute to knowledge of locomotory behaviour for a variety of aquatic species. Previously, collection of acceleration data has been limited to archival loggers, necessitating retrieval of the devices; however, recent advances in biotelemetry have allowed for acceleration data to be transmitted to a remote receiver. To illustrate the application of this technology, relative locomotory activity and depth utilisation of adult great barracuda (Sphyraenabarracuda)weremonitoredacrosshabitattypesanddielperiodsusingacoustictransmittersequippedwithtri- axial acceleration and pressure sensors within an acoustic telemetry array (n ¼53 receivers) deployed in The Bahamas. Although there were no differences in acceleration or depth use across habitats or diel periods, there was evidence of movement into shelf habitat during mid-day where they occupied depths410m. Given both the method of calculating the accelerometer output, and that the transmitters were unable to store and transmit large quantities of data, we suggest choosing transmitter settings with a short average delay and high transmission frequency to optimise data quality and resolution. This paper represents one of the first reports of the use of telemetered acceleration values from free-swimming fish.

Evaluation of Two Forms of Electroanesthesia and Carbon Dioxide for Short-Term Anesthesia in Walleye

Abstract Anesthetics immobilize fish, reducing physical damage and stress during aquaculture practices, stock assessment, and experimental procedures. Currently, only tricaine methanesulfonate (MS-222) is approved for use as an anesthetic for food fish in Canada and the United States; however, MS-222 can only be used with certain fish species, and treated fish must be held for a specified period of time before release into the wild. Two forms of electroanesthesia and carbon dioxide (CO2) were evaluated as anesthetics for adult walleye Sander vitreus to determine their suitability for use before intracoelomic implantation of telemetry transmitters. Walleyes were subjected to one of three treatment groups: constant direct current (CDC), pulsed direct current (PDC), and CO2. Fish subjected to these treatments were monitored for induction (where appropriate) and recovery time and whether these forms of anesthesia were conducive to implanting telemetry transmitters, that is, whether they fit a surgery threshol...

Spatial ecology of juvenile lemon sharks (Negaprion brevirostris) in tidal creeks and coastal waters of Eleuthera, The Bahamas

Fisheries exploitation and habitat alteration are threatening lemon shark (Negaprion bevirostris) populations because they use nearshore regions as nursery sites. As such, there is a need for information on the spatial ecology of juvenile lemon sharks to identify critical habitats that require protection, as well as to understand their basic ecology. The purpose of this study was to determine the habitat preferences and movement patterns of juvenile lemon sharks along a sub-section of coastline characterized by coastal flats and tidal creeks of Eleuthera, The Bahamas. Eleven juvenile lemon sharks (766u2009±u2009127xa0mm total length; mean±SD) were captured from various tidal creeks within the 23xa0km study area and were surgically implanted with acoustic transmitters. A series of 27 hydrophone receivers acted as a passive monitoring array to detect tagged individuals as they moved among habitats. Findings suggest that juvenile lemon sharks tagged in this study prefer shallow water habitats within tidal creeks, and typically display high site fidelity with occasional forays to alternate habitats or creeks. In fact, more than 90% of tagged lemon sharks had the greatest percentage of detections located at a receiver at or close to the location where they were tagged. There was no evidence of differences in diel or seasonal movement and habitat use. Knowledge gained from this study will be useful for directing future conservation and management strategies including coastal development plans and marine protected areas.

An introduction to the practical and ethical perspectives on the need to advance and standardize the intracoelomic surgical implantation of electronic tags in fish

The intracoelomic surgical implantation of electronic tags (including radio and acoustic telemetry transmitters, passive integrated transponders and archival biologgers) is frequently used for conducting studies on fish. Electronic tagging studies provide information on the spatial ecology, behavior and survival of fish in marine and freshwater systems. However, any surgical procedure, particularly one where a laparotomy is performed and the coelomic cavity is opened, has the potential to alter the survival, behavior or condition of the animal which can impair welfare and introduce bias. Given that management, regulatory and conservation decisions are based on the assumption that fish implanted with electronic tags have similar fates and behavior relative to untagged conspecifics, it is critical to ensure that best surgical practices are being used. Also, the current lack of standardized surgical procedures and reporting of specific methodological details precludes cross-study and cross-year analyses which would further progress the field of fisheries science. This compilation of papers seeks to identify the best practices for the entire intracoelomic tagging procedure including pre- and post-operative care, anesthesia, wound closure, and use of antibiotics. Although there is a particular focus on salmonid smolts given the large body of literature available on that group, other life-stages and species of fish are discussed where there is sufficient knowledge. Additional papers explore the role of the veterinarian in fish surgeries, the need for minimal standards in the training of fish surgeons, providing a call for more complete and transparent procedures, and identifying trends in procedures and research needs. Collectively, this body of knowledge should help to improve data quality (including comparability and repeatability), enhance management and conservation strategies, and maintain the welfare status of tagged fish.

Effects of an experimental short-term cortisol challenge on the behaviour of wild creek chub Semotilus atromaculatus in mesocosm and stream environments

The consequences of stress on the behaviour of wild creek chub Semotilus atromaculatus outside the reproductive period were studied using a single intra-coelomic injection of cortisol, suspended in coconut butter, to experimentally raise plasma cortisol levels. Behaviour between cortisol-treated, sham-treated (injected with coconut butter) and control S. atromaculatus was compared in a mesocosm system, using a passive integrated transponder array, and in a natural stream system (excluding shams), using surgically implanted radio transmitters. While laboratory time-course studies revealed that the cortisol injection provided a physiologically relevant challenge, causing prolonged (c. 3 days) elevations of plasma cortisol similar to that achieved with a standardized chasing protocol, no differences in fine-scale movements were observed between cortisol-treated, sham-treated and control S. atromaculatus nor in the large-scale movements of cortisol-treated and control S. atromaculatus. Moreover, no differences were observed in diel activity patterns among treatments. Differential mortality, however, occurred starting 10 days after treatment where cortisol-treated S. atromaculatus exhibited nearly twice as many mortalities as shams and controls. These results suggest that, although the experimental manipulation of cortisol titres was sufficient to cause mortality in some individuals, there were compensatory mechanisms that maintained behaviours (i.e. including activity and movement) prior to death. This study is one of the first to use experimental cortisol implants outside a laboratory environment and during the non-reproductive period and yields insight into how wild animals respond to additional challenges (in this case elevated cortisol) using ecologically meaningful endpoints.

Sustainable “Seafood” Ecolabeling and Awareness Initiatives in the Context of Inland Fisheries: Increasing Food Security and Protecting Ecosystems

The sustainable seafood movement has adopted a variety of certification and ecolabeling systems, as well as seafood-awareness campaigns, to influence industry and help consumers make informed decisions regarding their seafood consumption. However, a review of these programs revealed that the majority are focused on marine and coastal fisheries. Globally, freshwaters and their fish assemblages represent some of the most threatened systems and taxa because of multiple anthropogenic stressors. There is an urgent need to harness the momentum of the sustainable seafood movement for marine systems to benefit all aquatic systems, including freshwater. Moreover, given that freshwater systems are at particular risk in developing countries in which small-scale fisheries dominate, it is essential to expand awareness campaigns, through grassroots initiatives that differ significantly from current awareness campaigns that are global in focus, involve industrialized large-scale fisheries, and assume significant exports of seafood. Addressing the limitations of marine campaigns is a logical first step before launching new programs aimed at inland fisheries. In the long term, failure of the sustainable seafood movement to incorporate freshwater fisheries will lead to public perception that these fisheries are not in peril and may allow unsustainable practices to continue.

Seasonal Energetics and Condition of Bonefish from Different Subtropical Tidal Creeks in Eleuthera, the Bahamas

Abstract Body composition and fish health indices of bonefish Albula vulpes were investigated to elucidate the energy dynamics in poorly studied tropical tidal flat environments. In general, bonefish were composed of 72% water, 21% protein, 4% ash, and 3% lipids, which is consistent with the wet weight values of the majority of freshwater and marine fish studied to date. Significant inverse relationships between the water and lipid contents of whole-body, gonad, and liver tissues revealed that the percentage of water is a good indicator of the relative amount of stored energy in bonefish and may be used as a surrogate for lipid content in future studies. The liver was the main storage site for lipids, containing more than twice the fat in the whole body. While both abiotic (e.g., season and location) and biotic (e.g., sex and size) factors contributed to the predictive power of the general linear models generated for all constituent analyses, there were no significant differences in whole-body or liver lipid content between seasons, which may be explained by there being a consistent food supply year-round. There was, however, a significant relationship between lipid content and body size with respect to season. Lipid content decreased in the winter and increased in the summer with increasing body size, a trend that can be explained by the timing of the reproductive season in bonefish. Seasonal changes in the condition factor and gonadosomatic indices were also linked to the winter spawning season, with decreasing body condition and increasing gonad development in the winter. Observed site-specific differences in the lipid content and liver somatic indices of bonefish may be accounted for by local trophodynamics as well as subtle differences in life history strategies. The energy reserve and fish health index data collected in this study may provide a useful baseline for future comparative work and help elucidate fish energetics in dynamic tropical tidal flat systems.

Ontogenetic patterns in resource use dynamics of bonefish (Albula vulpes) in the Bahamas

We used stable isotope analysis to examine ontogenetic patterns in the resource use dynamics of bonefish (Albula vulpes) collected from two locations (Banks and Atlantic) within the coastal waters of Eleuthera, The Bahamas. A marked shift in δ13C signatures between leptocephali and juveniles reflected a rapid change in resource use, likely from pelagic to alternate neritic sources of primary production. Ontogenetic shifts in habitat use were observed across bonefish from both sides of Eleuthera, but direction of the isotopic shifts varied. Bonefish from the Atlantic side demonstrated an enrichment in 13C with size, whereas the opposite pattern was observed for individuals captured from the Banks. Differences are likely to be explained by the variability of primary production sources, which dominate each side of the island (i.e., more reliance on seagrass with ontogeny on the Atlantic side, versus a shift to macroalgal-dominated foodwebs with growth on the Banks side). Enrichment in 15N with body size was observed for both locations and reflects the ability to utilize a broader range of prey items with increasing gape size. Trophic diversity (inferred through nitrogen range), however, was lower on the Banks side, suggesting that reduced prey diversity may limit the increase in dietary shifts that gape size increases typically allow. A significant positive relationship between δ13C and whole-body energy density (MJxa0kg-1) in adults on the Banks side was observed. Adult bonefish that forage in seagrasses likely benefit from higher energy densities from selected prey items, and may explain this result. Data from this study reinforces the importance of a diversity of habitats in supporting bonefish throughout ontogeny.