Aggregation behavior and seasonal philopatry in male and female leopard sharks Triakis semifasciata along the open coast of southern California, USA

2014 ◽  
Vol 499 ◽  
pp. 157-175 ◽  
Author(s):  
AP Nosal ◽  
A Caillat ◽  
EK Kisfaludy ◽  
MA Royer ◽  
NC Wegner
Keyword(s):  
Southern California ◽  
Aggregation Behavior ◽  
Male And Female ◽  
Open Coast ◽  
Triakis Semifasciata ◽  
Leopard Sharks

Tissue-specific isotope trophic discrimination factors and turnover rates in a marine elasmobranch: empirical and modeling results

2012 ◽  
Vol 69 (3) ◽  
pp. 551-564 ◽  
Author(s):  
Luis Malpica-Cruz ◽  
Sharon Z. Herzka ◽  
Oscar Sosa-Nishizaki ◽  
Juan Pablo Lazo
Keyword(s):  
Natural Populations ◽  
Nitrogen Isotope ◽  
Cartilage Tissue ◽  
Turnover Rates ◽  
Isotopic Equilibrium ◽  
Isotope Turnover ◽  
Discrimination Factors ◽  
Triakis Semifasciata ◽  
Leopard Sharks ◽  
Trophic Discrimination

There are very few studies reporting isotopic trophic discrimination factors and turnover rates for marine elasmobranchs. A controlled laboratory experiment was conducted to estimate carbon and nitrogen isotope trophic discrimination factors and isotope turnover rates for blood, liver, muscle, cartilage tissue, and fin samples of neonate to young-of-the-year leopard sharks ( Triakis semifasciata ). Trophic discrimination factors varied (0.13‰–1.98‰ for δ13C and 1.08‰–1.76‰ for δ15N). Tissues reached or were close to isotopic equilibrium to the new diet after about a threefold biomass gain and 192 days. Liver and blood exhibited faster isotope turnover than muscle, cartilage tissue, and fin samples, and carbon isotopes turned over faster than those of nitrogen. Metabolic turnover contributed substantially to isotopic turnover, which differs from most reports for young marine teleosts. We modeled the relationship between muscle turnover rates and shark size by coupling laboratory results with growth rate estimates for natural populations. Model predictions for small, medium, and large wild leopard sharks indicate the time to isotopic equilibrium is from one to several years.

Demography of the central california population of the Leopard Shark (Triakis semifasciata)

1992 ◽  
Vol 43 (1) ◽  
pp. 183 ◽  
Author(s):  
GM Cailliet
Keyword(s):  
Population Growth ◽  
Reproductive Rate ◽  
Shark Species ◽  
Sandbar Shark ◽  
Lemon Shark ◽  
Carcharhinus Plumbeus ◽  
Net Reproductive Rate ◽  
Leopard Shark ◽  
Triakis Semifasciata ◽  
Leopard Sharks

Demographic analyses can be quite useful for effectively managing elasmobranch fisheries. However, they require valid estimates of age-specific mortality and natality rates, in addition to information on the distribution, abundance, habits and reproduction of the population, to produce reliable estimates of population growth. Because such detailed ecological information is usually unavailable, complete demographic analyses have been completed for only four shark species: the spiny dogfish, Squalus acanthias; the soupfin shark, Galeorhinus australis; the lemon shark, Negaprion brevirostris; and most recently the sandbar shark, Carcharhinus plumbeus. In California, reliable estimates of age, growth, mortality, age at maturity, and fecundity are available only for the leopard shark, Triakis semifasciata. A demographic analysis of this species yielded a net reproductive rate (Ro) of 4.467, a generation time (G) of 22.35 years, and an estimate of the instantaneous population growth coefficient (r) of 0.067. If the mean fishing pressure over 10 years (F= 0.084) is included in the survivorship function, Ro and r are reduced considerably, especially if leopard sharks first enter the fishery at early ages. A size limit of 120 cm TL (estimated age 13 years), especially for female sharks, is tentatively proposed for the leopard shark fishery.

The Mechanism of Gill Ventilation in the Dogfish and Skate

1960 ◽  
Vol 37 (1) ◽  
pp. 11-27 ◽  
Author(s):  
G. M. HUGHES
Keyword(s):  
Time Course ◽  
Gill Slit ◽  
Suction Pump ◽  
Pressure Pump ◽  
The Individual ◽  
Triakis Semifasciata ◽  
Leopard Sharks ◽  
Pressure Changes ◽  
Respiratory Movements ◽  
Branchial Region

1. The respiratory movements of the dogfish, Scyliorhinus (Scyllium) canicula (L.), and the ‘skate’, Raia clavata L. (thornback ray), have been studied by the use of cinematographic and mechanotransducer recording methods. Simultaneous determinations of the time-course of pressure changes in the oro-branchial and parabranchial cavities were also made by means of Hansen condenser manometers. 2. In both species movements of the mouth precede those of the spiracular valve and of the branchial region. Adduction and abduction of the branchial region spreads serially from the first to last gill slit in the dogfish, but movements of the individual gill arches are more nearly synchronous in the skate. Opening of the flap valves formed by extensions of the inter-branchial septa are synchronous in both species. 3. Water entering one side of the mouth leaves by the three posterior gill slits of the same side. Water entering the spiracle leaves through the anterior slits of the same side. This separation of flow is less marked in the skate. 4. The pressure curves recorded in all parts of the system have both positive and negative phases with respect to the external medium. The positive phase, associated with closing of the mouth and spiracle, is larger in the oro-branchial than in the parabranchial cavities and vice versa. The time-course of the pressure changes indicates that the flow across the gills is maintained by the action of a pressure pump in front and a suction pump behind. 5. The suction pump plays a more important role than the pressure pump in the skate and its contribution to the flow across the gills is by no means negligible in the dogfish. 6. The differential pressure curves suggest that the flow across the gills is continuous except in the dogfish for a brief period when the gradient is reversed. The absence of this reversal in the skate suggests that the external gill slit openings are controlled by an active mechanism. This is probably an adaptation to bottom-living habit. 7. All these observations relate to animals which are stationary with respect to the water. During swimming at a reasonable speed leopard sharks (Triakis semifasciata) have been observed to make few or no respiratory movements, although they immediately ventilate actively on coming to rest at the bottom of the aquarium.

Reproduction, diet and habitat use of leopard sharks, Triakis semifasciata (Girard), in Humboldt Bay, California, USA

2005 ◽  
Vol 56 (8) ◽  
pp. 1089 ◽  
Author(s):  
David A. Ebert ◽  
Thomas B. Ebert
Keyword(s):  
Habitat Use ◽  
Sexual Segregation ◽  
Minor Importance ◽  
Nursery Ground ◽  
Relative Importance ◽  
Fish Eggs ◽  
Index Of Relative Importance ◽  
Diet Analyses ◽  
Triakis Semifasciata ◽  
Leopard Sharks

A total of 312 female leopard sharks (Triakis semifasciata) was sampled in Humboldt Bay, California, USA, an important nursery ground for this species, during the spring month of May from 1983 to 1984 and 1985. Sexual segregation is strong as only three males were observed in the study area. Females ranged in size from 120 to 154 cm total length, and all examined were determined to be mature. Overall, 130 out of 153 females examined in early May contained term embryos. The number of embryos per female ranged from 1 to 37 with larger females tending to possess more embryos. Of the 159 individuals examined in late May, no females were found carrying embryos and most were ovulating. Diet analyses revealed that, overall, fish eggs (Atherinopsis californiensis) at 48.0%, had the highest percentage Index of Relative Importance (%IRI), followed by the cancrid crabs, Cancer antennarius (29.8%) and C. magister (11.6%). All other prey were of relatively minor importance, cumulatively representing 10.6% of the overall diet. Adults shift their diet after parturition: early May sharks fed almost exclusively on fish eggs, while crabs were more important in those examined in late May.

Absence of neurotoxic effects in leopard sharks, Triakis semifasciata, following domoic acid exposure

Toxicon ◽  
2006 ◽  
Vol 47 (7) ◽  
pp. 747-752 ◽  
Author(s):  
P. Schaffer ◽  
C. Reeves ◽  
D.R. Casper ◽  
C.R. Davis
Keyword(s):  
Domoic Acid ◽  
Acid Exposure ◽  
Neurotoxic Effects ◽  
Triakis Semifasciata ◽  
Leopard Sharks
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