A demographic method with population density compensation for estimating productivity and yield per recruit of the leopard shark (Triakis semifasciata)

1997 ◽  
Vol 54 (2) ◽  
pp. 415-420 ◽  
Author(s):  
D W Au ◽  
S E Smith
Keyword(s):  
Population Density ◽  
Density Compensation ◽  
Leopard Shark ◽  
Triakis Semifasciata ◽  
Yield Per Recruit

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.

Cardiac function of the leopard shark, Triakis semifasciata

1990 ◽  
Vol 160 (3) ◽  
pp. 259-268 ◽  
Author(s):  
N. Chin Lai ◽  
Ralph Shabetai ◽  
Jeffrey B. Graham ◽  
Brian D. Hoit ◽  
Katharina S. Sunnerhagen ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Leopard Shark ◽  
Triakis Semifasciata

scholarly journals Tiller size/population density compensation in grazed Coastcross bermudagrass swards

2001 ◽  
Vol 58 (4) ◽  
pp. 655-665 ◽  
Author(s):  
André Fischer Sbrissia ◽  
Sila Carneiro da Silva ◽  
Carlos Augusto Brandão de Carvalho ◽  
Roberta Aparecida Carnevalli ◽  
Luiz Felipe de Moura Pinto ◽  
...  
Keyword(s):  
Population Density ◽  
Leaf Area ◽  
Compensation Mechanism ◽  
Regression Analyses ◽  
Sheep Grazing ◽  
Cool Season ◽  
Compensatory Mechanisms ◽  
Area Index ◽  
Density Compensation ◽  
Size Population

Several compensatory mechanisms in pastures do not allow optimisation of responses from the processes of herbage production and utilisation. Compensation due to tiller size/density relationships is one of these mechanisms. This experiment evaluated this process for Coastcross bermudagrass and compared the responses to those reported for temperate forages. Treatments were "steady state" sward surface heights of 5, 10, 15, and 20 cm that were maintained from August, 1998, through July, 1999 by sheep grazing. The experimental design was a randomised complete block, replicated four times. Pasture responses were evaluated on four separate dates (15/12/1998, 25/01/1999, 07/04/1999 and 04/07/1999) with respect to: tiller population density, tiller weight, leaf mass and leaf area per tiller and herbage mass (biomass). Tiller volume, leaf area index (LAI), tiller leaf:stem ratio and tiller leaf area:volume ratio (R) were calculated. Simple regression analyses between tiller population density and tiller weight were also performed. Coastcross swards showed a tiller size/density compensation mechanism where high tiller population densities were associated with small tillers and vice-versa; except on the last evaluation. However, regression analysis revealed linear coefficients of -3.83 to -2.05, which are lower than the theoretical expectation of -3/2. The lower R values observed, when compared to those reported for perennial ryegrass, suggest that Coastcross swards optimised their LAI via clonal integration among tillers in contrast with tillers of cool-season grasses that respond more as individuals. However, this hypothesis has yet to be experimentally verified.

Aspects of Shark Swimming Performance Determined Using a Large Water Tunnel

1990 ◽  
Vol 151 (1) ◽  
pp. 175-192 ◽  
Author(s):  
JEFFREY B. GRAHAM ◽  
HEIDI DEWAR ◽  
N. C. LAI ◽  
WILLIAM R. LOWELL ◽  
STEVE M. ARCE
Keyword(s):  
Body Size ◽  
Swimming Speed ◽  
Swimming Performance ◽  
Beat Frequency ◽  
Swimming Velocity ◽  
Water Tunnel ◽  
Lemon Shark ◽  
Negaprion Brevirostris ◽  
Leopard Shark ◽  
Triakis Semifasciata

A large, sea-going water tunnel was used in various studies of shark swimming performance. The critical swimming velocity (Ucrit, an index of aerobically sustainable swimming speed) of a 70 cm long lemon shark (Negaprion brevirostris Poey) was determined to be 1.1 Ls−1, where L is body length. The Ucrit of the leopard shark (Triakis semifasciata Girard) was found to vary inversely with body size; from about 1.6Ls−1in 30–50cm sharks to 0.6LS−1 in 120cm sharks. Large Triakis adopt ram gill ventilation at swimming speeds between 27 and 60cms−1, which is similar to the speed at which this transition occurs in teleosts. Analyses of tail-beat frequency (TBF) in relation to velocity and body size show that smaller Triakis have a higher TBF and can swim at higher relative speeds. TBF, however, approaches a maximal value at speeds approaching Ucrit, suggesting that red muscle contraction velocity may limit sustained swimming speed. The TBF of both Triakis and Negaprion rises at a faster rate with swimming velocity than does that of the more thunniform mako shark (Isurus oxyrinchus Rafinesque). This is consistent with the expectation that, at comparable relative speeds, sharks adapted for efficient swimming should have a lower TBF. The rates of O2 consumption of swimming lemon and mako sharks are among the highest yet measured for elasmobranchs and are comparable to those of cruise-adapted teleosts.

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