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.

Growth and demography of the Pacific Angle Shark (Squatina californica), based upon tag returns off California

1992 ◽  
Vol 43 (5) ◽  
pp. 1313 ◽  
Author(s):  
GM Cailliet ◽  
HF Mollet ◽  
GG Pittenger ◽  
D Bedford ◽  
LJ Natanson
Keyword(s):  
Population Growth ◽  
Age Determination ◽  
Growth Function ◽  
Reproductive Rate ◽  
Shark Species ◽  
Demographic Analysis ◽  
Net Reproductive Rate ◽  
Leopard Shark ◽  
The Pacific ◽  
Elasmobranch Species

Knowledge of the age, growth and demography of an organism can be quite useful for managing its fishery. However, for many elasmobranch species, no valid estimates of age, growth and therefore age-specific mortality and natality rates are available. Thus, even though the distribution, abundance, habits and reproduction of a population may be known, no reliable estimates of population growth are possible. As a result, detailed demographic analysis has been completed for only a few shark species (e.g. the California leopard shark, Triakis semlfasciata). All age-determination techniques attempted for the Pacific angel shark (Squatina californica) have met with difficulties. Recently, however, we have accumulated data on 69 tag-recaptures and have used this information to model a von Bertalanffy growth function (VBGF) to predict the growth of this commercially exploited shark species. We performed a demographic analysis of this species, which yielded a net reproductive rate (R0) of 2.25, a generation time (G) of 14.5 years, and an estimate of the instantaneous population growth coefficient (r) of 0.056 year-1, assuming that only natural mortality (M) was occurring, estimated to be 0.2 year-1. When reasonable estimates of fishing mortality (F) are included in the survivorship function, Ro and r are reduced considerably. Presently, Pacific angel sharks first enter the fishery at the same size and age at which they first reproduce. Until accurate estimates of M and Fare available, it would be prudent to set a size limit considerably above the size at first reproduction to protect the Pacific angel shark in California.

Plant Resistance in Some Modern Soybean Varieties May Favor Population Growth and Modify the Stylet Penetration of Bemisia tabaci (Hemiptera: Aleyrodidae)

2021 ◽  
Author(s):  
Mauricélia F Almeida ◽  
Clébson S Tavares ◽  
Euires O Araújo ◽  
Marcelo C Picanço ◽  
Eugênio E Oliveira ◽  
...  
Keyword(s):  
Population Growth ◽  
Bemisia Tabaci ◽  
Intrinsic Rate ◽  
Reproductive Rate ◽  
Genetically Engineered ◽  
Population Increase ◽  
Net Reproductive Rate ◽  
Bt Toxin ◽  
Demographic Performance

Abstract Complaints of severe damage by whiteflies in soybean fields containing genetically engineered (GE) varieties led us to investigate the role of transgenic soybean varieties expressing resistance to some insects (Cry1Ac Bt toxin) and to herbicide (glyphosate) on the population growth and feeding behavior of Bemisia tabaci (Gennadius) MEAM1 (Hemiptera: Aleyrodidae). In the laboratory, the whiteflies reared on the GE Bt soybeans had a net reproductive rate (R0) 100% higher and intrinsic rate of population increase (rm) 15% higher than those reared on non-GE soybeans. The increased demographic performance was associated with a higher lifetime fecundity. In electrical penetration graphs, the whiteflies reared on the GE soybeans had fewer probes and spent 50% less time before reaching the phloem phase from the beginning of the first successful probe, indicating a higher risk of transmission of whitefly-borne viruses. Data from Neotropical fields showed a higher population density of B. tabaci on two soybean varieties expressing glyphosate resistance and Cry1Ac Bt toxin. These results indicate that some GE soybean varieties expressing insect and herbicide resistances can be more susceptible to whiteflies than non-GE ones or those only expressing herbicide resistance. Most likely, these differences are related to varietal features that increase host-plant susceptibility to whiteflies. Appropriate pest management may be needed to deal with whiteflies in soybean fields, especially in warm regions, and breeders may want to consider the issue when developing new soybean varieties.

scholarly journals Patterns in abundance and size of sharks in northwestern Australia: cause for optimism

2019 ◽  
Vol 77 (1) ◽  
pp. 72-82
Author(s):  
Matias Braccini ◽  
Brett Molony ◽  
Nick Blay
Keyword(s):  
Life Histories ◽  
Shark Species ◽  
Sandbar Shark ◽  
Carcharhinus Plumbeus ◽  
Study Region ◽  
Scalloped Hammerhead ◽  
Carcharhinus Obscurus ◽  
Northwestern Australia ◽  
Mean Size ◽  
Catch Rates

Abstract Reliable information for population assessments is rare for sharks. We quantified patterns in catch rates and mean size for numerous tropical and subtropical species from 15 years of fishery-independent surveys (2002–2017) in northwestern Australia. This study region represents an area of ~0.8 million km2 which was closed to commercial shark fishing from 1993 or 2005 onward due to the very high State-wide catches of sandbar (Carcharhinus plumbeus) and dusky (Carcharhinus obscurus) sharks. A total of 43 shark and ray species were sampled, with sandbar shark being the most commonly caught species, followed by milk (Rhizoprionodon acutus), spot-tail (Carcharhinus sorrah), tiger (Galeocerdo cuvier), blacktip (Carcharhinus limbatus and Carcharhinus tilstoni), dusky and sliteye (Loxodon macrorhinus) sharks, and scalloped hammerhead (Sphyrna lewini). For sandbar shark, catch rates increased between 2008 and 2017 whereas for other taxa catch rates were mostly stable (albeit fluctuating). Mean size at capture fluctuated across years with no particular trends. Unlike for other parts of the world, catch rates and mean size of northwestern Australian sharks have been stable or increased in recent years. Though most shark species have conservative life histories, when science, management and enforcement work synergistically, sustainable resource use, recovery and conservation outcomes can all be achieved.

scholarly journals Epidermal Microbiomes of Triakis Semifasciata Are Consistent Across Captive and Wild Environments

2021 ◽  
Author(s):  
Asha Goodman ◽  
Bhavya Papudeshi ◽  
Michael P. Doane ◽  
Colton Johnson ◽  
Maria Mora ◽  
...  
Keyword(s):  
Taxonomic Composition ◽  
Shark Species ◽  
Wild Populations ◽  
Microbiome Composition ◽  
Α Diversity ◽  
Novel Association ◽  
Species Specific ◽  
La Jolla ◽  
Triakis Semifasciata ◽  
Leopard Sharks

Abstract Background: Characterizations of sharks-microbe systems in wild environments have outlined patterns of species-specific microbiomes; however, whether captivity affects these trends has yet to be determined. We used high-throughput shotgun sequencing to assess the epidermal microbiome belonging to leopard sharks (Triakis semifasciata) in captive (Birch Aquarium, La Jolla California), semi-captive (<1 year in captivity; Scripps Institute of Oceanography, California) and wild environments (Moss Landing and La Jolla, California). Results: Here we report captive environments do not drive microbiome composition of T. semifasciata to significantly diverge from wild counterparts as life-long captive sharks maintain a species-specific epidermal microbiome resembling those associated with semi-captive and wild populations. Major taxonomic composition shifts observed were inverse changes of top taxonomic contributors across captive duration, specifically an increase of Pseudoalteromonadaceae and consequent decrease of Pseudomonadaceae relative abundance as T. semifasciata increased duration in captive conditions. Moreover, we show captivity did not lead to significant losses in microbial α-diversity of shark epidermal communities. Finally, we present a novel association between T. semifasciata and the Muricauda genus as MAGs revealed a consistent relationship across captive, semi-captive, and wild populations. Conclusions: Our report illustrates the importance of conservation programs for coastal fishes as epidermally-associated microbes of near-shore shark species do not suffer detrimental impacts from long or short-term captivity. Our findings also expand on current understanding of shark epidermal microbiomes, explore the effects of ecologically different scenarios on benthic shark microbe associations, and highlight novel microbial associations that are consistent across captive gradients.

scholarly journals Statistik demografi Dolichotetranychus floridanus Banks pada dua kultivar nanas (Ananas comosus (L.) Merr.)

2021 ◽  
Vol 10 (4) ◽  
pp. 660-667
Author(s):  
Ariffatchur Fauzi ◽  
Sugeng Santoso ◽  
Ali Nurmansyah
Keyword(s):  
Life Cycle ◽  
Population Growth ◽  
Generation Time ◽  
Intrinsic Rate ◽  
Reproductive Rate ◽  
Ananas Comosus ◽  
Reproduction Rate ◽  
Fruit Crops ◽  
Net Reproductive Rate ◽  
Pest Infestation

Pineapple is one of important fruit crops in Indonesia. One of important problems in pineapple production is pest infestation.. This study aims to investigate the biology, demography, and life cycle of Dolichotetranychus floridanus Banks on two pineapple cultivars (Queen and Cayenne). Observation of mite development (eggs-adults) were conducted every 6 hours.  Adults were observed everyday to record the fecundity.  The life table was constructed from the survivor and fecundity of D. floridanus. Based on this table, the variables of population growth, including gross reproduction rate (GRR), net reproductive rate (R0), mean generation time (T) and increase intrinsic rate (r) were determined. The results showed that the GRR, R0, and r of D. floridanus in the Queen cultivar were higher than Cayenne cultivar, while the T in the Queen cultivar was lower. Queen cultivar more suitable for D. floridanus than Cayenne cultivar.

scholarly journals Effect of flufenzine on population growth of Tetranychus urticae Koch (Acari: Tetranychidae)

Pesticidi ◽  
2002 ◽  
Vol 17 (1-2) ◽  
pp. 5-22 ◽  
Author(s):  
Dejan Marcic
Keyword(s):  
Population Growth ◽  
Tetranychus Urticae ◽  
Sublethal Effects ◽  
Reproductive Rate ◽  
Net Reproductive Rate ◽  
Development Stages ◽  
Female Survivors ◽  
Significant Statistical Difference ◽  
Jackknife Procedure ◽  
Tetranychus Urticae Koch

Effect of flufenzine on different parameters of Tetranychus urticae Koch population growth was investigated. The parameters were computed based on the life tables of female survivors of treatment at different development stages (egg, larva, protonymph, deutonymph) with acaricide concentrations that had caused >90% mortality. The intrinsic rates of increase acquired by the so-called jackknife procedure (rj) from female treatment survovors at egg (rj = 0.237) and larva (rj = 0.220) stages had no significant statistical difference from the corresponding values in control (rj = 0.230). Female survovors of treatment at protonymph or deutonymph stages had 2.1 and 4.5 times lower net reproductive rate (R0) against the control while the corresponding rj values in treatment (0.204 and 0.171) were statistically significantly lower than the control (0.255). Treatment with flufenzine at protonymph and deutonymph stages significantly disturbed the age structure of the surviving part of population. The article discusses the significance of sublethal effects of flufenzine in advancement of the acaricide's application strategy in controlling T. urticae.

scholarly journals MODELING DEMOGRAPHIC RESPONSE TO CONSTANT TEMPERATURE IN BRYOBIA RUBRIOCULUS (ACARI: TETRANYCHIDAE)

2014 ◽  
Vol 1 (1) ◽  
pp. 18-29
Author(s):  
Saeid Javadi Khederi ◽  
Mohammad Khanjani
Keyword(s):  
Population Growth ◽  
Reproductive Rate ◽  
Natural Increase ◽  
Growth Potential ◽  
Distribution Model ◽  
Thermal Constant ◽  
Temperature Threshold ◽  
Immature Stages ◽  
Net Reproductive Rate ◽  
Rate Of Increase

The demographic parameters of brown mite, Bryobia rubrioculus Scheuten were carried out in order to characterize the population growth potential at five constant temperatures: 20, 22.5, 25, 27.5 and 30ºC, 60 ± 5 % RH and 16: 8 (L: D) h. The highest intrinsic rate of natural increase (rm = 0.0243/day), net reproductive rate (R0 = 2.4 ♀/♀/T) and finite rate of increase (λ = 1.0245 day-1) values were determined at 22.5°C. The mean generation time (T) of the population ranged from 22.7 days at 30°C to 45.8 days at 20°C. The maximum and minimum survival rates (lx) were recorded at 22.5ºC and 30ºC. Survivorship data (lx) of adult females were summarized and compared using the shape and scale parameters of the Weibull frequency distribution model across. The age specific fecundity data (mx) was modeled as a function of time by using Polynomial model. The lower temperature threshold (t) and thermal constant (k) of the immature stages were estimated using Ikemoto and Takai linear model to be 12.85ºC and 279.7 degree days (DD), respectively. Of the non-linear models, the Analitis-1, Analitis-2, Analitis-3 and Analitis/Allahyari models were found to be the best for the modeling development rate of immature stages of B. rubrioculus. The optimal temperature for population growth of brown mite on apple was found at 22.5°C.

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.

Population dynamics of the plant pathogenic fungus Uncinula necator

1992 ◽  
Vol 70 (5) ◽  
pp. 942-946 ◽  
Author(s):  
Dan O. Chellemi ◽  
James J. Marois
Keyword(s):  
Population Growth ◽  
Pathogenic Fungus ◽  
Age Distribution ◽  
Reproductive Rate ◽  
Vitis Vinifera L ◽  
Uncinula Necator ◽  
Matrix Population Models ◽  
Net Reproductive Rate ◽  
Generation Times ◽  
Doubling Times

Cohort life tables were constructed and population parameters determined for Uncinula necator (Schw.) Burr. parasitizing the foliage of Vitis vinifera L. cv. Carignane at various temperatures. The net reproductive rate per individual conidium at 19, 22, 26, and 30 °C was 577, 2272, 1300, and 157 conidia per generation, respectively. Mean generation times ranged from 22.84 days at 19 °C to 13.60 days at 30 °C. Intrinsic growth rates (r) varied from 0.43 per day at 19 °C to 1.24 per day at 26 °C. Doubling times ranged from 0.56 days at 26 °C to 1.63 days at 19 °C. Matrix population models were used to project population growth. Stable age distributions at 19, 22, 26, and 30 °C were reached after 70, 50, 45, and 45 days, respectively. At a stable age distribution, greater than 96% of the population was contained in the first age-class (days 1 – 5). Key words: demography, cohort life table, grape powdery mildew, net reproductive rate, population growth rate.

scholarly journals Fatal Infection in a Wild Sandbar Shark (Carcharhinus plumbeus), Caused by Streptococcus agalactiae, Type Ia-ST7

Animals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 284
Author(s):  
Danny Morick ◽  
Nadav Davidovich ◽  
Eyal Bigal ◽  
Ezra Rosenbluth ◽  
Arieli Bouznach ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
Streptococcus Agalactiae ◽  
Pathogenic Bacteria ◽  
Molecular Techniques ◽  
Shark Species ◽  
Post Mortem ◽  
Sandbar Shark ◽  
Carcharhinus Plumbeus ◽  
Type Ia ◽  
Important Fish

Streptococcus agalactiae is one of the most important fish pathogenic bacteria as it is responsible for epizootic mortalities in both wild and farmed species. S. agalactiae is also known as a zoonotic agent. In July 2018, a stranded wild sandbar shark (Carcharhinus plumbeus), one of the most common shark species in the Mediterranean Sea, was found moribund on the seashore next to Netanya, Israel, and died a few hours later. A post-mortem examination, histopathology, classical bacteriology and advanced molecular techniques revealed a bacterial infection caused by S. agalactiae, type Ia-ST7. Available sequences publicly accessible databases and phylogenetic analysis suggest that the S. agalactiae isolated in this case is closely related to fish and human isolates. To the best of our knowledge, this is the first description of a fatal streptococcosis in sandbar sharks.

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