Session 28: AES Life History (first 5)/ Reproduction (last 4)Room: Conference Theater2022-07-29 13:45 - 15:45 |
| Moderator: Kady Lyons |
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2. 13:45 Age and Growth of Great (Sphyrna mokarran) and Scalloped Hammerheads (Sphyrna lewini) in the Western North Atlantic Ocean. Bryan Frazier*, South Carolina Dept of Natural Resources; Ashley Galloway, South Carolina Dept of Natural Resources; Lisa Natanson, NOAA Northeast Fisheries Science Center; Andrew Piercy, Valencia College; Christian Jones, NOAA, Southeast Fisheries Science Center; Kristin Hannan, NOAA, Southeast Fisheries Science Center; William Driggers, NOAA, Southeast Fisheries Science Center bryan@dixieland-delights.com
A total of 388 vertebrae from great hammerheads (Sphyrna mokarran) and 1,026 vertebrae from scalloped hammerheads (Sphyrna lewini) were collected from fishery dependent and independent sources to generate growth models. For great hammerheads 204 females (42-357 cm FL), and 179 males (40-297) were available; for scalloped hammerheads 403 females (27-245 cm FL range), and 623 males (27.6-287 cm FL). Three parameter von Bertalanffy growth models were fit to females, males, and sexes combined. Great hammerhead females (L∞ = 323.9 mm FL, k = 0.11, to = -2.06 years) had a higher asymptotic length and lower growth constant than males (L∞ = 249.4 mm FL, k = 0.20, to = -1.37 years) with significant difference among VBGF parameter estimates between sexes. Scalloped hammerhead females (L∞ = 229.2 cm FL, k = 0.086, to = -2.35 years) and males (L∞ = 230.1 cm FL, k = 0.092, to = -2.17 years) had similar estimates of average asymptotic length and growth coefficient, although there was a significant difference among growth parameter estimates between the sexes. Maximum estimated ages for great hammerheads was 38, and 39.5 for scalloped hammerheads. While longevity is similar between the two species, scalloped hammerheads grow slower to a smaller average asymptotic length than great hammerheads. Growth and longevity of both species suggests they are highly susceptible to overfishing. |
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3. 14:00 Age and Growth of Spinner Sharks, Carcharhinus brevipinna, in the Western North Atlantic Ocean. Elizabeth Vinyard*, South Carolina Dept. of Natural Resources; David Portnoy, Texas A&M University-Corpus Christi; William Driggers, III, National Marine Fisheries Service, Southeast Fisheries Science Center; Lisa Natanson, (retired) NOAA/NMFS/NEFSC Narragansett Laboratory; Jill Hendon, Center for Fisheries Research and Development, The University of Southern Mississippi; Jeremy Higgs, Center for Fisheries Research and Development, The University of Southern Mississippi; Jim Gelsleichter, University of North Florida; Bryan Frazier, South Carolina Dept. of Natural Resources vinyarde@dnr.sc.gov
Vertebrae from spinner sharks were collected from throughout their range in coastal waters of the western North Atlantic Ocean off the United States to obtain direct age estimates and generate growth models. A total of 711 vertebrae (310 males and 401 females) were processed with maximum observed age estimates for males and females at 21.5 and 23.5 years, respectively. Sizes ranged from 482 mm to 1790 mm fork length (FL) for males and 410 mm to 2006 mm FL for females. Age and length data were fit to logistic, Gompertz and von Bertalanffy models with the three parameter von Bertalanffy models producing the best fit. There were significant differences among female and male model parameter estimates, thus necessitating sex-specific von Bertalanffy growth models. As expected, females had a higher theoretical maximum size and lower growth constant (L∞ = 1925 mm FL, k = 0.125, to = -2.87 years) than males (L∞ = 1822 mm FL, k = 0.143, to = -3.03 years). Significant spatial differences in growth were also detected ( χ2= 41.80, p < 0.001) with spinner sharks in the U.S. Atlantic reaching larger asymptotic lengths and slower growth coefficients relative to the Gulf of Mexico. |
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4. 14:15 Exploring the Physicochemical Context of Near Infrared Spectroscopy (NIRS) for Elasmobranch Ageing. Michelle Passerotti*, NOAA Fisheries Northeast Fisheries Science Center; Kenneth Goldman, Kenai Peninsula College, University of Alaska Anchorage; Sabine Wintner, University of Kwazulu-Natal; Joseph Quattro, School of the Earth, Ocean, and Environment, University of South Carolina michelle.passerotti@noaa.gov
Age estimation remains one of the most important yet costly and time-consuming components of fisheries management. Despite decades of research and a multitude of technologies evaluated, no method has emerged that displaces growth band counting for accurate age determination. This is especially problematic for some long-lived elasmobranchs such as the sand tiger shark Carcharias taurus, for which discontinuous growth band deposition (i.e. “missing time” in vertebrae) confounds traditional band-counting methods. Near infrared spectroscopy (NIRS) has recently emerged as a novel and potentially transformative technology for estimating fish age via spectroscopic detection of age-related changes to organic chemical bonds within calcified tissues. Despite compelling evidence for the use of this technology in ageing studies, little is known about the drivers underlying the NIRS-age correlation and hence how NIRS may apply to species with discontinuous growth band deposition. This talk presents novel results of physicochemical experiments using age-validated C. taurus vertebrae that elucidate the underlying drivers of the NIRS-age correlation. NIRS age predictions were generated from scans of both whole and powdered vertebrae, for which bomb-radiocarbon validated ages were available, in order to evaluate the assumption of a chemical basis, rather than a morphometric basis, for NIRS age estimation. Fixed quantities of ground powder from vertebrae yielded comparable age predictions to those obtained from whole structures, suggesting an underlying chemical basis for NIRS age prediction. However, C. taurus ages were not well-predicted beyond the age at which band deposition becomes discontinuous, suggesting NIRS is not a solution for ageing these problematic species. |
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5. 14:30 The Metabolic Basis of Population Growth Rate Across Marine Fishes. Sarah Gravel*, Simon Fraser University; Jennifer Bigman, NOAA; Sebastian Pardo, Ecology Action Centre; Serena Wong, Pacific Salmon Foundation; Nicholas Dulvy, Simon Fraser University sarahgravel95@gmail.com
The intrinsic rate of population increase (rmax) is a fundamental parameter in fisheries management and conservation, representing a population’s capacity to replace itself. While we have long known that body size is a key correlate of rmax, there is increasing evidence that population growth rates vary latitudinally and with depth, suggesting there is a thermal metabolic basis of population dynamics. Furthermore, recent advances highlight the influence of oxygen availability in shaping metabolic traits of water-breathing ectotherms. Yet, little is understood of how oxygen and temperature effects on physiological performance relate to population dynamics. We bridge from the individual to population scales with a comparative analysis of rmax and metabolic rate, in relation to oxygen, temperature, and body size across 38 chondrichthyan and 102 teleost species, using population-matched life history and metabolic traits mined from primary literature and environmental data from the World Ocean Atlas. Specifically, we ask whether: (1) variation in metabolic rates across species are best explained by models including mass, temperature and oxygen, (2) the same can be said when modeling variation in rmax. Using model selection, we found that body mass, temperature and oxygen, including an interaction between oxygen and mass, best explained variation in resting metabolic rates and rmax. Our results corroborate previous findings of the effects of temperature and body mass on metabolism and further support the central role of oxygen in shaping traits underlined by metabolic physiology in aquatic ectotherms, and the importance in considering how it affects smaller and larger species disparately. |
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6. 14:45 Reproductive Ecology of Centrophorus uyato in the Northeastern Gulf of Mexico. Brian Moe*, Florida State University; Charles Cotton, State University of New York College of Agriculture and Technology; Dean Grubbs, Florida State University Coastal and Marine Laboratory brian.moe87@gmail.com
The Little Gulper, Centrophorus uyato, is a deep-water shark that exhibits a very conservative life history strategy, including slow growth, low fecundity, and late maturity. A total of 671 C. uyato (406 males, 255 females, and 10 unsexed embryos) were collected in the northeastern Gulf of Mexico between 2011 and 2017 at depths ranging from 200 m to 860 m to provide a comprehensive description of the reproductive ecology of this species. This species segregates by sex, though segregation is not correlated to depth, geographic location, or seasonality. Total catch rates were, however, correlated with geographic location. Sexual dimorphism is evident with females attaining larger weights and lengths and maturing at a significantly larger size than males. Of the 68 pregnant females observed, 78% had vitellogenic ova in at least one ovary, suggesting gestation is concurrent with vitellogenesis. Average ovarian fecundity was 1.13 with a maximum of three vitellogenic oocytes and no significant difference in oocytes found in the right versus left ovaries. Average uterine fecundity was 1.04 (maximum of 2), with 91% of pups found in the right uterus. Reproduction is lecithotrophic viviparous with full-term embryos (with depleted yolk sacs) ranging in size from 31.6 – 36.1 cm FL. The smallest free-swimming pup (open yolk sac scar) was 34 cm, suggesting pupping occurs within the observed size range of fell-term embryos. Embryos captured in March and April ranged in size from 8.5 – 36.1 cm FL, suggesting mating is aseasonal. This information may inform management and conservation of this vulnerable species. |
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7. 15:00 Residency, dispersal, and repeated philopatry of tiger sharks Galeocerdo cuvier at a proposed pupping location in The Bahamas. Matthew Smukall*, Bimini Shark Lab; Andrew Seitz, University of Alaska Fairbanks; Felicie Dhellemmes, Leibniz Institute of Freshwater Ecology and Inland Fisheries; Maurits van Zinnicq Bergmann, Florida International University; Vital Heim, University of Basel; Samuel Gruber, Bimini Shark Lab; Tristan Guttridge, Saving The Blue mattsmukall@biminisharklab.com
Species specific management zones, such as The Bahamas Shark Sanctuary, can provide some protection for sharks across large swaths of ocean. However, it is important to understand the manner and duration for which species use these areas, especially during key life stages like reproduction. This can be challenging for highly mobile species, which have large home ranges and occupy diverse habitat. The waters around Bimini, The Bahamas, are hypothesized to be pupping and nursery grounds for tiger sharks Galeocerdo cuvier, with documented catches of gravid females and young-of-year pups each year. Here, we combined conventional tagging, and acoustic and satellite telemetry to investigate this hypothesis based on seasonal residency, dispersal patterns, and longterm philopatry in this area. Young-of-year sharks had low overall residency to Bimini and few detections on cooperative arrays throughout the region, indicating that high natural mortality may limit dispersal for this age class. Recapture rates and acoustic telemetry indicate longterm philopatry to this area, predominately by mature sharks. Sexually mature females showed seasonal residency to Bimini during cooler water months, but sharks also dispersed extensively throughout the region (up to 12,000 km) and spent significant time (mean = 67 ± 25.5% of transmitted days) outside the protection of The Bahamas Shark Sanctuary. Several mature sharks returned across consecutive years; one being documented across a decade. Our findings suggest that the broad area around Bimini likely plays an important role as a pupping site, but may not serve as a primary nursery ground for tiger sharks. |
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8. 15:15 Anamniocentesis: Development of a method to genotype oviparous embryos from perivitelline fluid using Zebra Sharks as a model. Jennifer Wyffels*, University of Delaware; Kady Lyons, Georgia Aquarium; Lance Adams, Aquarium of the Pacific; Kevin Feldheim, Field Museum klyons@georgiaaquarium.org
Future conservation efforts intend to breed Zebra Sharks (Stegostoma tigrinum) from zoos and aquariums and send egg cases to the Indo-Pacific as part of a multi-institutional effort to reintroduce this species to Indonesia. Zebra Sharks are able to reproduce parthenogenically and, thus, there is an outstanding need to develop a method to screen egg cases before they are shipped to Indonesia ensure high genetic diversity in this founder population. The objective of this study was to determine if pervitelline fluid could serve as an alternative medium for genotyping sharks to identify developing parthenotes before hatch and avoid direct tissue sampling of embryos. Perivitelline fluid was aspirated from wind egg cases, egg cases with a yolk but no developing embryo and egg cases with a yolk and a developing embryo 4 – 7 weeks post-oviposition and preserved using RNAlater or TNES. Perivitelline fluid and embryos (if present) were genotyped and methods were compared across egg case categories and buffers. Perivitelline fluid from negative controls (wind and infertile yolked egg cases with no developing embryos) failed to produce a genetic signal using either preservation buffer. The majority (80%) of perivitelline fluid from egg cases with a developing embryo resulted in successful DNA amplification and genotyping when preserved in TNES compared to none in RNAlater. The genotype from perivitelline fluid matched the genetic identity of the embryo for all fertile eggs sampled. Perivitelline fluid shows promise as a medium for genetically screening fertile egg cases to identify embryos developing parthenogenetically. |
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9. 15:30 Quantifying Reproductive Hormones in Skeletal Muscle Tissue of Porbeagles (Lamna nasus) Demonstrates the Value of Biological Sample Sharing. Brooke Anderson*, Arizona State University; Juliana Kaloczi, Arizona State University; Amanda Einig, Arizona State University; Courtney Holden, Arizona State University; Linda Donaldson, Arizona State University; Lisa Natanson, NOAA Fisheries Northeast Fisheries Science Center (Just Retired); Katherine Viducic, NOAA Fisheries Northeast Fisheries Science Center; Michelle Passerotti, NOAA Fisheries Northeast Fisheries Science Center; Heather Bowlby, Fisheries and Oceans Canada; James Sulikowski, Arizona State University bnande11@asu.edu
Effective conservation and management of elasmobranchs requires an understanding of life history, including reproductive characteristics, for each species. While lethal sampling is often required or is the most effective technique to collect many life history data, it is recognized that the amount of information gained from lethal sampling needs to be optimized, and at the same time non-lethal techniques need to be developed and validated for future use. For example, concentrations of reproductive hormones in plasma and muscle tissues have been found to correlate to sexual maturity and reproductive cycles in many elasmobranch species, offering a potentially non-lethal technique to study reproductive characteristics. This study utilized muscle tissues from porbeagles (Lamna nasus) that were collected and dissected up to 37 years ago for other life history studies, to quantify reproductive hormone concentrations (testosterone, estradiol) for this species. To date, testosterone has been isolated and quantified in muscle of 45 males (85-246 cm fork length) and estradiol has been isolated and quantified in muscle of 19 females (80-226 cm fork length). Male muscle testosterone concentrations varied from below the detection limit to 735 pg/g and female muscle estradiol concentrations ranged from below the detection limit to 99 pg/g. Twenty or more additional samples will be analyzed for each sex and insights into the relationship between reproductive hormone concentrations and maturity and reproductive stage will be presented. This study demonstrates the value of collaboration and specimen sharing among researchers to optimize the amount of data gained from biological samples. |