Session 38: AES Fisheries (first 1)/Physiology (first 5)/ Morphology (last 4)Room: Conference Theater2022-07-30 13:30 - 15:30 |
| Moderator: Kara Yopak |
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1. 13:30 The Recreational Shore-based Shark Fishery in Florida, USA: Catch Rates, Mortality Rates, and Updates. Jill Brooks*, Carleton University; Emma Kent, Carleton University; Jessika Guay, Carleton University; Jacqueline Chapman, BC Hydro; Vivian Nguyen, Carleton University; Daniel Tabatabai, Recreational Angler; Kaytlin Russel, Recreational Angler; Thomas Gallagher, Recreational Angler; Steven Cooke, Carleton University; Hannah Medd, American Shark Conservancy hannah@americansharkconservancy.org
Recreational, rod and reel, shore-based shark fishing is a popular activity along the coast of Florida, USA. The recent review of NOAA’s recreational fishing data resulted in a six-fold increase in the estimation of effort, catch and harvest by all shore-based anglers. A portion of these data are collected in part by intercepting anglers at fishing access points, however, it may not capture those involved in shore-based shark fishing which occurs mostly at night in locations with relatively low fishing activity. We analyzed responses to our online survey of Florida shore-based shark fishing permit holders representing a subset that specifically targets great hammerhead (Sphyrna mokarran) to better describe angler demographics, motivations, gear types, and behaviors. We will also present survivorship data on the great hammerheads caught and released with pop-off archival satellite tags (PSATs) to estimate the post-release mortality rates of this species in the shore-based fishery and insights into the diversity of species caught in this fishery, including several species with upcoming stock assessments. These data, both the human dimension and the mortality rates, are important to decision-makers for determining stock assessments, calculating Annual Catch Limits across the commercial and recreational sectors as well as providing evidence for the development of best practices with and for the angling community. |
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2. 13:45 Sleeping at the bottom of the sea: The first physiological evidence of sleep in sharks. Michael Kelly*, Simon Fraser University mlk.sleepresearch@gmail.com
Sharks represent the earliest group of jawed vertebrates and as such, they may provide original insight for understanding the evolution of sleep in more derived animals. Unfortunately, beyond a single behavioural investigation, very little is known about sleep in these ancient predators. As such, recordings of physiological indicators of sleep in sharks have never been reported. Reduced energy expenditure arising from sustained restfulness and lowered metabolic rate during sleep have given rise to the hypothesis that sleep plays an important role for energy conservation. To determine whether this idea applies also to sharks, we compared metabolic rates of draughtsboard sharks (Cephaloscyllium isabellum) during periods ostensibly thought to be sleep, along with restful and actively swimming sharks across a 24 h period. We also investigated behaviours that often characterize sleep in other animals, including eye closure and postural recumbency, to establish relationships between physiology and behaviour. Overall, lower metabolic rate and a flat body posture reflect sleep in draughtsboard sharks, whereas eye closure is a poorer indication of sleep. Our results support the idea for the conservation of energy as a function of sleep in these basal vertebrates. |
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3. 14:00 Acute Phase Reactants in the Nurse Shark, Ginglymostoma cirratum. Elana Rusnak*, Rosenstiel School of Marine and Atmospheric Science, University of Miami; Liza Merly, Rosenstiel School of Marine and Atmospheric Science, University of Miami e.rusnak@umiami.edu
Overall health and wellness can be measured by a suite of biomarkers that are direct indicators of immune condition. Acute phase proteins, like C-reactive protein (CRP) and serum amyloid-P (SAP), have been extensively used as biomarkers in wellness assessments in clinical and veterinary medicine and aquaculture practices. There does not yet exist a shark-specific biomarker assay that allows researchers to monitor captive populations or assess health in wild populations. In this study, liver tissue from healthy and sick nurse sharks, Ginglymostoma cirratum, were probed for clinically relevant acute phase proteins using molecular techniques. For the first time, a C-reactive protein-like molecule has been isolated from nurse shark genomic DNA. When compared phylogenetically with other taxa, the nurse shark CRP-like molecule grouped closest with similar proteins from elasmobranchs, teleosts, and basal teleost fish, indicating that this molecule may function differently from what is seen in the mammalian condition. In a novel case study, liver transcriptomes between a healthy and a sick nurse shark were compared, and clinically relevant immune genes were sought out within these transcriptomes. Genes in the complement and coagulation cascades were among the most significant differentially expressed genes, indicating that these pathways are critical during a shark immune response. As no major acute phase proteins (e.g. CRP/SAP) were actively expressed in the liver tissue during infection, it is suggested that complement proteins should be the focus of future work with respect to isolation of suitable shark biomarkers that could be used in clinical and wild health assessments. |
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4. 14:15 Metabolic Morphology and Ecological Lifestyle In Sharks. Wade VanderWright*, Simon Fraser University; Jennifer Bigman, NOAA; Anthony Iliou, Simon Fraser University; Nick Dulvy, Simon Fraser University wvanderw@sfu.ca
Metabolism underpins life histories, population dynamics, and extinction risk. Morphological traits that are linked to an organism's metabolism may provide a first approximation to the ecological needs to support growth, survival, and reproduction. Here we examine the relationship between respiratory physiology (i.e. gill slit height in proportion to total length) and activity level (caudal fin aspect ratio) in nearly all extant shark species (n=456). Gill slit heights and caudal fin aspect ratios were collected and measured from the field guide Sharks of the World (Ebert 2013). We used a Bayesian-phylogenetic inference model that accounts for each species’ maximum size, primary habitat type, and evolutionary history. We found a strong positive relationship between gill slit height and activity level. We also show that primary habitat had a strong effect on this relationship with pelagic sharks exhibiting the highest gill slit heights and activity levels while deep water sharks showed the opposite trend. These findings suggest that proxies for metabolic demand may be available via external and easy to measure morphological traits and natural history. Insight into the metabolic demand of these animals may allow us to estimate vital life history traits that could inform ecological risk assessments. |
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5. 14:30 Liver Biopsy as a Non-lethal Sampling Technique for Laboratory and Field Applications. Christine Bedore*, Georgia Southern University; Emily Sapp, University of North Florida; Pierce Folk, Georgia Southern University; Johanne Lewis, Georgia Southern University; Kady Lyons, Georgia Aquarium; Alexa Delaune, Mississippi Aquarium cbedore@georgiasouthern.edu
Tissue sampling is a staple of ecological, conservation, and physiological work on all vertebrate animals. However, tissue collection is often limited to external and easy to access samples or it requires lethal sampling. Internal organ and tissue samples, the liver for example, can substantially increase the amount of information we can collect from each animal. Elasmobranch fishes have lipid-rich livers that can contribute a breadth of additional data for projects investigating stable isotopes, organic contaminants, nutritional status/bioenergetics, egg production, and chronic stress. To improve access to internal liver tissues without the need for lethal sampling, we have applied a veterinary-based liver biopsy surgical technique for use on stingrays and sharks in the laboratory. We used three treatment groups to assess recovery from surgery: control (only handled, no surgical procedures), sham surgeries (incision only, no biopsy), and liver biopsy (8mm biopsy collected with biopsy punch tool). Biopsied individuals were sacrificed between 2-8 weeks after surgery to examine liver healing. All livers were healed at the time of euthanasia, indicated by presence of a superficial scar at the biopsy site. Though the procedure is still limited to laboratory uses, the success of our biopsy procedure could make it a valuable addition to surgical procedures performed for implanting acoustic transmitters in the field. |
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6. 14:45 Temporal Microbiome Colonization Dynamics of Zebra Shark Egg Cases. Kady Lyons*, Georgia Aquarium; Jennifer Wyffels, University of Delaware; Sonsiray Álvarez-Narváez, University of Georgia; Emily
Peele, University of North Carolina Wilmington ; Ryan Freedman, NOAA; Susan Sanchez, University of Georgia klyons@georgiaaquarium.org
The Zebra Shark is an oviparous species where the surface structure of the outside and the inside of the egg case is macroscopically distinct, and thus each may play an organizing role in microbiome colonization post-oviposition. The anterior half of six, freshly-laid wind egg cases were dissected, and initial swabs of the inside and outside of the egg case were taken adjacent to a corresponding formalin-fixed shell piece. Egg case halves were then suspended in a tank filled with artificial seawater where they were serially sampled at four, eight, and twelve weeks post-oviposition for pairs of swabs and fixed shell pieces. Swabs were sent to the University of Georgia for bacterial quantification and fixed shell pieces to the University of Delaware for SEM image analysis of the inside and outside of egg cases over time. Microbial composition at the initial time point, both in terms of numbers and species diversity, was significantly different between the inside and outside of egg cases. However, by the week-4 time point, microbial composition on the inside and outside of egg cases were similar in terms of bacterial abundance and diversity, and by the 12-week time point, the microbiome of both the inside and outside had converged. SEM images of the outside and inside of egg cases visually corroborated these results. Thus, microbial differences between the outside and inside of Zebra Shark egg cases at oviposition appear to last temporarily during incubation." |
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7. 15:00 Morphology of the Embryonic Rostral Sheath of the Smalltooth Sawfish, Pristis pectinata. Gregg R. Poulakis, Charlotte Harbor Field Laboratory, Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission; Jennifer T. Wyffels, University of Delaware; P. Eric Fortman, Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission; Andrew K. Wooley, Charlotte Harbor Field Laboratory, Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission; Lukas B. Heath*, Charlotte Harbor Field Laboratory, Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission; Patrick W. Wilson, Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission lukas.heath@myfwc.com
Elongated rostra have evolved in taxonomically diverse animals and improve feeding success, enhance defense, and aid reproduction. The sawfishes (family Pristidae) have among the most extreme examples of elongated rostra, comprising up to 25% of the total length and containing modified dermal denticles, often referred to as ‘rostral teeth’, along the lateral margins. Pristids have evolved a covering for the embryonic rostral teeth that is present during gestation and parturition. Despite its uniqueness, little is known about the morphology of the covering, which has led to it being referred to by several names including sheath. Capture of individuals with sheath remaining is rare. Of the 768 smalltooth sawfish (Pristis pectinata) caught primarily in the Charlotte Harbor estuarine system, Florida during permitted sampling between 2004 and 2021, remnant embryonic rostral sheaths were noted on 22 occasions. Sheath samples were taken from between rostral teeth, fixed in the field, and later processed for light microscopy. Most of the sheath is composed of a central collagen layer that contains reticulin and other collagens with blood vessels and fibrocytes. An outer layer is composed of columnar cells above a basement membrane and outermost spherical cells that are hypothesized to maintain isolation of the rostral teeth. Based on field recapture data, the sheath disappears within about 4 days postpartum. The sheath should be classified as an organ because it is a collection of tissues that form a specialized functional unit. |
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8. 15:15 Are Two Heads Better Than One? Brain and Sensory Organization in a Dicephalic Blue Shark Embryo, Prionace glauca. Kara Yopak*, Department of Biology and Marine Biology, University of North Carolina Wilmington; Omar Santana Morales, Ecología Cielo Mar y Tierra AC; Dan Cartamil, Scripps Institution of Oceanography, University of California San Diego; Gary Cowin, National Imaging Facility, Centre for Advanced Imaging, The University of Queensland; Shaun Collin, School of Agriculture, Biomedicine, and Environment, La Trobe University yopakk@uncw.edu
Dicephaly is a developmental anomaly, whereby the embryo is axially bifurcated and presents as conjoined twins, with two heads on a single body. Although this abnormality is rare, there are more descriptions in blue sharks (Prionace glauca) than any other shark species, likely given their global distribution, importance in several fisheries, and relatively high fecundity. However, no study to date has assessed patterns of brain organization in any shark species with this malformation. In this study, a dicephalic P. glauca embryo was incidentally collected from a pregnant female off Baja California, Mexico and imaged on a 9.4T Bruker Biospec small animal scanner, using contrast-enhanced, T1-weighted MR imaging. The brain, cranial nerves, and key sensory systems (olfactory rosette, eyes, semicircular canals) were segmented from the 3D data. Externally, the embryo has shared gill slits, trunk, umbilical opening, and a single coiled caudal fin. Anterior to the gills, there are two rostra, two mouths, four distinct nares, and four eyes, two of which that are fused just at the edge of the ocular cavity. Correspondingly, the brain shows four distinct olfactory rosettes and olfactory bulbs, and two distinct telencephala, which fuses just beyond the mesencephalic midbrain. Posteriorly, the specimen has a partially bifurcated cerebellum, a single medulla, and a single set of semicircular canals. Three additional blue shark embryos of a similar developmental stage without malformations were scanned and assessed for comparison. Data on the dicephalic specimen will be contextualized within normal embryonic and ontogenetic brain and sensory development in P. glauca. |