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Edward J. Heist - One of the best experts on this subject based on the ideXlab platform.
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Microsatellite analysis of population structure in the shortfin mako (Isurus oxyrinchus)
Canadian Journal of Fisheries and Aquatic Sciences, 2003Co-Authors: Aaron W. Schrey, Edward J. HeistAbstract:Microsatellite analysis of the shortfin mako shark (Isurus oxyrinchus) revealed very weak evidence of population structure. Samples collected from the North Atlantic, South Atlantic, North Pacific, South Pacific, and Atlantic, and Pacific coasts of South Africa were screened at four microsatellite loci. Multilocus measures of population subdivision were much lower than expected (FST = 0.0014, P = 0.1292; RST = 0.0029, P = 0.019). Power analysis revealed that the study had a high level of power (>0.995) to detect the magnitude of FST expected based on a previous study of mtDNA and assumptions of equal male and female dispersal. Thus, integrating the results from microsatellite- and mitochondrial-based studies may provide evidence for gender-biased dispersal for the shortfin mako.
Douglas A Syme - One of the best experts on this subject based on the ideXlab platform.
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thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark
The Journal of Experimental Biology, 2007Co-Authors: Jeanine M Donley, Chugey A Sepulveda, Robert E Shadwick, Douglas A SymeAbstract:The work loop technique was used to examine contractile properties of the red aerobic locomotor muscle (RM) in the ectothermic leopard shark Triakis semifasciata and endothermic shortfin mako shark Isurus oxyrinchus . The effects of axial position and temperature on the twitch kinetics, and the stimulus duration and phase producing maximum net positive work and power output were investigated. Contractile performance was measured over the temperature range of 15 to 25°C for Triakis and 15 to 28°C for Isurus at cycle frequencies (analogous to tailbeat frequencies) ranging from 0.25 to 3 Hz using muscle bundles isolated from anterior (0.4 L where L is total body length) and posterior (0.6–0.65 L ) axial positions. Pairwise comparisons of twitch times for anterior and posterior muscle samples indicated that there were no significant differences related to body position, except in mako sharks at unphysiologically cool temperatures (<20°C). We found no significant differences in optimal stimulus duration, phase, net work or power output between anterior and posterior bundles in each species. With increasing cycle frequency the stimulus duration yielding maximum power decreased while optimal phase occurred earlier. The cycle frequency at which peak power was generated in leopard shark RM was only affected slightly by temperature, increasing from about 0.6 to 1.0 Hz between 15 and 25°C. In contrast, mako RM showed a much more dramatic temperature sensitivity, with the peak power frequency rising from <0.25 to 2.25 Hz between 15 and 28°C. These data support the hypothesis that the contractile properties of RM are functionally similar along the body in both species. In addition, our data identify a significant difference in the effect of temperature on net work and power output between these two shark species; at 15°C muscle from the ectothermic leopard shark performs relatively well in comparison with mako, while at higher temperatures, which reflect those normally experienced by the mako, the optimal cycle frequency for power is nearly double that of the leopard shark, suggesting that the mako may be able to maintain greater aerobic swimming speeds.
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Thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark
The Journal of Experimental Biology, 2007Co-Authors: Jeanine M Donley, Chugey A Sepulveda, Robert E Shadwick, Douglas A SymeAbstract:The work loop technique was used to examine contractile properties of the red aerobic locomotor muscle (RM) in the ectothermic leopard shark Triakis semifasciata and endothermic shortfin mako shark Isurus oxyrinchus . The effects of axial position and temperature on the twitch kinetics, and the stimulus duration and phase producing maximum net positive work and power output were investigated. Contractile performance was measured over the temperature range of 15 to 25°C for Triakis and 15 to 28°C for Isurus at cycle frequencies (analogous to tailbeat frequencies) ranging from 0.25 to 3 Hz using muscle bundles isolated from anterior (0.4 L where L is total body length) and posterior (0.6–0.65 L ) axial positions. Pairwise comparisons of twitch times for anterior and posterior muscle samples indicated that there were no significant differences related to body position, except in mako sharks at unphysiologically cool temperatures (
Jeffrey B. Graham - One of the best experts on this subject based on the ideXlab platform.
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The artisanal elasmobranch fishery of the Pacific coast of Baja California Sur, Mexico, management implications
Scientia Marina, 2013Co-Authors: Sergio Ramírez-amaro, Ofelia Escobar-sánchez, Felipe Galván-magaña, Jeffrey B. Graham, Daniel P. Cartamil, Gerardo González-barba, Maribel Carrera-fernández, Oscar Sosa-nishizaki, Anet Rochin-alamilloAbstract:Artisanal fisheries in Mexico account for approximately 40% of the total national catch. In 2009, Baja California Sur (BCS) had the second largest catch of elasmobranchs on the Mexican Pacific coast. This paper characterizes and describes the artisanal elasmobranch fishery of Pacific coast of BCS from 2000 to 2010. Sixty artisanal camps were documented, of which 45 targeted elasmobranchs, using primarily gillnets and longlines. We identified 52 elasmobranch species. Gillnetting accounted for 73.5% of the fishing effort and most frequently captured Rhinobatos productus, Mustelus henlei and Myliobatis californica . Longline fishing accounted for 26.5% of effort, most frequently capturing Prionace glauca and Isurus oxyrinchus . The prevalence of juveniles of several species (e.g., Cephaloscyllium ventriosum, Galeorhinus galeus, Isurus oxyrinchus , and Myliobatis californica ) within landings suggests that fishing effort may be opportunistically directed at breeding or nursery areas. Despite the dominance of species with wide distributions, we observed a significant biogeographic pattern in the abundance of some species relative to Bahia Magdalena. Results of the present study will be useful to detect changes in the structure of commercially exploited elasmobranch populations, and to provide useful indications for management purposes.
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Aerobic metabolic rates of swimming juvenile mako sharks, Isurus oxyrinchus
Marine Biology, 2007Co-Authors: C. A. Sepulveda, Jeffrey B. Graham, Diego BernalAbstract:The shortfin mako shark, Isurus oxyrinchus, is a highly streamlined epipelagic predator that has several anatomical and physiological specializations hypothesized to increase aerobic swimming performance. A large swim-tunnel respirometer was used to measure oxygen consumption (MO2) in juvenile mako sharks (swimming under controlled temperature and flow conditions) to test the hypothesis that the mako shark has an elevated maintenance metabolism when compared to other sharks of similar size swimming at the same water temperature. Specimen collections were conducted off the coast of southern California, USA (32.94°N and 117.37°W) in 2001-2002 at sea-surface temperatures of 16.0–21.0°C. Swimming MO2 and tail beat frequency (TBF) were measured for nine mako sharks [77–107 cm in total length (TL) and 4.4 to 9.5 kg body mass] at speeds from 28 to 54 cm s−1 (0.27–0.65 TL s−1) and water temperatures of 16.5–19.5°C. Standard metabolic rate (SMR) was estimated from the extrapolation to 0-velocity of the linear regression through the LogMO2 and swimming speed data. The estimated LogSMR (±SE) for the pooled data was 2.0937 ± 0.058 or 124 mg O2 kg−1 h−1. The routine metabolic rate (RMR) calculated from seventeen MO2 measurements from all specimens, at all test speeds was (mean ± SE) 344 ± 22 mg O2 kg−1h−1 at 0.44 ± 0.03 TL s−1. The maximum metabolic rate (MMR) measured for any one shark in this study was 541 mg O2 kg−1h−1 at 54 cm s−1 (0.65 TL s−1). The mean (±SE) TBF for 39 observations of steady swimming at all test speeds was 1.00 ± 0.01 Hz, which agrees with field observations of 1.03 ± 0.03 Hz in four undisturbed free-swimming mako sharks observed during the same time period. These findings suggest that the estimate of SMR for juvenile makos is comparable to that recorded for other similar-sized, ram-ventilating shark species (when corrected for differences in experimental temperature). However, the mako RMR and MMR are apparently among the highest measured for any shark species.
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Movement Patterns and Bioenergetics of the Shortfin Mako Shark
California Sea Grant College Program, 2004Co-Authors: Jeffrey B. GrahamAbstract:The mako shark (Isurus oxyrinchus) is the quintessential shark—an awesome swimming machine, spectacularly acrobatic, fast, sleek and muscular, with a mouthful of razor sharp teeth. As with tunas, makos maintain body temperatures in their locomotor muscles above ambient water temperatures. This regional endothermy, as it is known technically, is believed to enhance muscle power and efficiency while swimming.
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Hemodynamics and Blood Properties of the Shortfin Mako Shark (Isurus oxyrinchus)
Copeia, 1997Co-Authors: N. Chin Lai, Keith E. Korsmeyer, Steven Katz, David B. Holts, Leeanne M. Laughlin, Jeffrey B. GrahamAbstract:Lamnid sharks are difficult experimental subjects, and knowledge of their cardiovascular system has been largely based on morphological (Tota et al., 1983; Emery et al., 1985), histological (Sanchez-Quintana and Hurle, 1987; De Andres et al., 1990), biochemical (Farrell and Davie, 1991; Dickson et al., 1993), and hematological investigations (Wells and Davie, 1985; Emery, 1986). Because these sharks have a physiological capacity that exceeds other species (Graham et al., 1990), it is important to obtain cardiovascular data in living specimens. This report details in vivo studies of the cardiovascular and blood respiratory properties and the heartregulatory mechanism of shortfin mako sharks (Isurus oxyrinchus) carried out at sea on freshly collected specimens, most of which were subsequently released.
Roberto Melendez - One of the best experts on this subject based on the ideXlab platform.
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new insights on the trophic ecology of blue prionace glauca and shortfin mako sharks Isurus oxyrinchus from the oceanic eastern south pacific
Marine Biology Research, 2018Co-Authors: Sebastian A Klarian, Patricio Barria, Francisco Concha, Carlos Canalescerro, Patricia Zarate, Sebastian Hernandez, Maike Heidemeyer, Pauline Sallaberrypincheira, Roberto MelendezAbstract:The blue shark (Prionace glauca) and the shortfin mako shark (Isurus oxyrinchus) are two large and highly migratory sharks distributed in most oceans. Although they are often caught in the south Pa...
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Assessing the trophic position of two sharks from the open waters of the southeastern Pacific Ocean
Latin American Journal of Aquatic Research, 2016Co-Authors: Sebastian A Klarian, Patricio Barria, Augusto Cornejo, Pauline Sallaberry-pincheira, Roberto MelendezAbstract:Indexación: Web of ScienceStable isotope analyses for shortfin mako (Isurus oxyrinchus) and blue sharks (Prionace glauca) were conducted to assess their trophic position in two periods of time (before 1980 and after 2000) in the Southeastern Pacific waters (SEP). Both sharks showed that their trophic position decreased over time (P < 0.05). Many factors could be involved in this change such as dietary shifts, prey availability, or indirect fishing effects in SEP waters.RESUMEN. Para evaluar los niveles tróficos de los tiburones marrajo (Isurus oxyrinchus) y azulejo (Prionace glauca) en dos períodos de tiempo (previo a 1980 y posterior al 2000) en aguas del Pacífico suroriental (SEP), se realizaron análisis de isótopos estables. Ambos tiburones mostraron un descenso del nivel trófico en el tiempo (P < 0,05). Varios son los factores que pueden estar involucrados en este evento, como los cambios dietarios, la disponibilidad de las presas o los efectos indirectos de la pesquería en aguas del Pacífico suroriental.http://www.lajar.cl/pdf/imar/v44n2/Art%C3%ADculo_44_2_25.pd
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Feeding and trophic relationships of two highly migratory sharks in the eastern south Pacific Ocean
2012Co-Authors: Sebastian Lopez, Patricio Barria, Roberto MelendezAbstract:A total of 433 stomachs of Prionace glauca and Isurus oxyrinchus. The results showed a high dietary overlapping (PSI = 0.69) in both sharks, whereas the most important preys were bony fishes (72.21 % and 86.95 % IRI, P. glauca and I. oxyrinchus, respectively).
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alimentacion del tiburon marrajo Isurus oxyrinchus rafinesque 1810 lamniformes lamnidae en el pacifico suroriental
Revista De Biologia Marina Y Oceanografia, 2009Co-Authors: Sebastian Lopez, Roberto Melendez, Patricio BarriaAbstract:In order to examine the feeding of mako shark Isurus oxyrinchus, the stomach content of 205 specimens, captured between 21o and 35oS and 78o and 118o W off C...
Aaron W. Schrey - One of the best experts on this subject based on the ideXlab platform.
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Microsatellite analysis of population structure in the shortfin mako (Isurus oxyrinchus)
Canadian Journal of Fisheries and Aquatic Sciences, 2003Co-Authors: Aaron W. Schrey, Edward J. HeistAbstract:Microsatellite analysis of the shortfin mako shark (Isurus oxyrinchus) revealed very weak evidence of population structure. Samples collected from the North Atlantic, South Atlantic, North Pacific, South Pacific, and Atlantic, and Pacific coasts of South Africa were screened at four microsatellite loci. Multilocus measures of population subdivision were much lower than expected (FST = 0.0014, P = 0.1292; RST = 0.0029, P = 0.019). Power analysis revealed that the study had a high level of power (>0.995) to detect the magnitude of FST expected based on a previous study of mtDNA and assumptions of equal male and female dispersal. Thus, integrating the results from microsatellite- and mitochondrial-based studies may provide evidence for gender-biased dispersal for the shortfin mako.
