The status of the western rock lobster, Panulirus cygnus, fishery and the effectiveness of management controls in increasing the egg production of the stock

2001 ◽  
Vol 52 (8) ◽  
pp. 1657 ◽  
Author(s):  
Norm Hall ◽  
Norm Hall ◽  
Chris Chubb ◽  
Chris Chubb
Keyword(s):  
Egg Production ◽  
Maximum Size ◽  
Management Control ◽  
Effective Control ◽  
Rock Lobster ◽  
The Status ◽  
Fishery Data ◽  
Age Structured ◽  
Panulirus Cygnus ◽  
Age Structured Model

In 1993, managers were concerned about the decline in the breeding stock of western rock lobster and introduced controls to raise egg production from the stock to those levels experienced in the late 1970s and early 1980s. The release of setose female lobsters (those with ovigerous setae) and of nonsetose female lobsters larger than a maximum legal size was required, the minimum legal carapace length (CL) was raised by 1 mm during the migratory phase between November and January, and the number of pots (traps) fished was reduced by 18%. Between 1993 and 1999, increases were observed in the indices of egg production obtained from research surveys and in the estimated released catches of setose female lobsters and of nonsetose female lobsters larger than the maximum size. From these and other fishery data, an age-structured model was developed to determine the status of the fishery and the effectiveness of each management control. By 1999, egg production of the stock had increased to 134% of the target level and 22% of the virgin level. Protection of setose female lobsters was the most effective control, followed by the reduction in pot usage, and then maximum legal size.

scholarly journals Spatial and temporal changes in egg production in the western rock lobster(Panulirus cygnus)fishery

2009 ◽  
Vol 43 (1) ◽  
pp. 151-161 ◽  
Author(s):  
Roy Melville‐Smith ◽  
Simon De Lestang ◽  
Adrian W. Thomson
Keyword(s):  
Egg Production ◽  
Temporal Changes ◽  
Rock Lobster ◽  
Spatial And Temporal Changes ◽  
Panulirus Cygnus

Increased density, biomass and egg production in an unfished population of Western Rock Lobster (Panulirus cygnus) at Rottnest Island, Western Australia

2007 ◽  
Vol 58 (3) ◽  
pp. 286 ◽  
Author(s):  
R. C. Babcock ◽  
J. C. Phillips ◽  
M. Lourey ◽  
G. Clapin
Keyword(s):  
Western Australia ◽  
Carrying Capacity ◽  
Egg Production ◽  
Carapace Length ◽  
Spiny Lobster ◽  
Shallow Waters ◽  
Recreational Fishing ◽  
Total Biomass ◽  
Rock Lobster ◽  
Panulirus Cygnus

Surveys of spiny lobster (Panulirus cygnus) populations in shallow waters surrounding Rottnest Island in Western Australia revealed much higher levels of density, biomass and egg production in no-take than in fished areas. Density of lobsters was ~34 times higher in the sanctuary, and density of lobsters above minimum legal size around 50 times higher than in other areas around the island where recreational fishing is allowed. Mean carapace length (CL), total biomass and egg production of lobsters in the sanctuary zone were significantly higher than in adjacent fished areas. Large individuals (≥100 mm CL), especially large males, were found almost exclusively within the sanctuary. The abundance of mature animals in these shallow waters indicates that not all P. cygnus migrate to deep water and that shallow water habitats may currently be well below carrying capacity in terms of biomass and egg production. If implemented in a systematic way, unfished areas such as the Kingston Reefs could also provide a useful fisheries-independent tool for assessing trophic interactions and the structure and density of unfished populations, and for estimating parameters such as growth of larger individuals that may be rare or absent in more widely fished populations.

scholarly journals A Numerical Model of Philippine Population Growth: Child Policy, Quantitative Insights and Challenges

2014 ◽  
Vol 8 (1) ◽  
Author(s):  
DYLAN ANTONIO SJ. TALABIS ◽  
ERICK JUSTINE V. MANAY ◽  
ARIEL L. BABIERRA ◽  
JABEZ JOSHUA M. FLORES ◽  
JOMAR F. RABAJANTE
Keyword(s):  
Population Growth ◽  
Carrying Capacity ◽  
Birth Rate ◽  
The Philippines ◽  
Child Policy ◽  
The Status ◽  
Zero Growth ◽  
Age Structured ◽  
Age Structured Model ◽  
Transient Stabilization

The study investigates the effect of imposing an n-child policy by forecastingthe population of the Philippines using a discrete age-structured compartmental model. Based on the results of the projection, a policy promoting a maximumof two children per couple leads to a transient stabilization (i.e., the populationeventually declines after attaining zero-growth rate). A three-child policy may alsolead to stabilization yet may converge beyond the calculated Verhulstian carryingcapacity of approximately 200M. However, overshooting the carrying capacity canbe resolved by increasing the available resources that can support the escalatingpopulation size. A child policy dictating a maximum of four or more children percouple results to a similar population growth as the status quo due to the inherentdeclining birth rate. With the declining birth rate trend in the Philippines,population stabilization is realizable even without implementing a child policy butonly after 100 years. Furthermore, this study estimated the future age structure andthe resultant GDP per capita income associated with each child policy.Keywords: Demography, population projection, child policy, zero growth, economy,logistic, carrying capacity, age-structured model, Philippines

scholarly journals Fractional optimal control problem for an age-structured model of COVID-19 transmission

2021 ◽  
pp. 110625
Author(s):  
Bouchaib Khajji ◽  
Abdelfatah Kouidere ◽  
Mohamed Elhia ◽  
Omar Balatif ◽  
Mostafa Rachik
Keyword(s):  
Optimal Control ◽  
Optimal Control Problem ◽  
Control Problem ◽  
Structured Model ◽  
Fractional Optimal Control Problem ◽  
Fractional Optimal Control ◽  
Age Structured ◽  
Age Structured Model

scholarly journals An Age-Structured Model for Tilapia Lake Virus Transmission in Freshwater with Vertical and Horizontal Transmission

2021 ◽  
Vol 83 (8) ◽  
Author(s):  
Cyrille Kenne ◽  
René Dorville ◽  
Gisèle Mophou ◽  
Pascal Zongo
Keyword(s):  
Horizontal Transmission ◽  
Virus Transmission ◽  
Structured Model ◽  
Age Structured ◽  
Age Structured Model

scholarly journals The emergence of rabbit haemorrhagic disease virus: will a non-pathogenic strain protect the UK?

2001 ◽  
Vol 356 (1411) ◽  
pp. 1087-1095 ◽  
Author(s):  
P.J. White ◽  
R.A. Norman ◽  
R.C. Trout ◽  
E.A. Gould ◽  
P.J. Hudson
Keyword(s):  
Disease Virus ◽  
Pathogenic Strain ◽  
Rabbit Haemorrhagic Disease Virus ◽  
Rabbit Haemorrhagic Disease ◽  
Seroprevalence Data ◽  
Age Structured ◽  
Reproductive Rates ◽  
The Uk ◽  
Haemorrhagic Disease ◽  
Age Structured Model

Rabbit haemorrhagic disease virus emerged in China in 1984, and has killed hundreds of millions of wild rabbits in Australia and Europe. In the UK there appears to be an endemic non–pathogenic strain, with high levels of seroprevalence being recorded, in the absence of associated mortality. Using a seasonal, age–structured model we examine the hypothesis that differences in rabbit population demography differentially affect the basic reproductive rates ( R 0 ) of the pathogenic and non–pathogenic strains, leading to each dominating in some populations and not others. The strain with the higher R 0 excluded the other, with the dynamics depending upon the ratio of the two R 0 values. When the non–pathogenic strain dominated, the pathogenic strain caused only transient mortality, although this could be significant when the two R 0 values were similar. When the pathogenic strain dominated, repeated epidemics led to host eradication. Seroprevalence data suggest that the non–pathogenic strain may be protecting some, but not all UK populations, with half being ‘at risk’ from invasion by the pathogenic strain and a fifth prone to significant transient mortality. We identify key questions for empirical research to test this prediction.

POTENTIAL YIELD OF A ROCK SHRIMP STOCK, SICYONIA PENICILLATA IN THE NORTHERN GULF OF CALIFORNIA

Crustaceana ◽  
1999 ◽  
Vol 72 (6) ◽  
pp. 581-590 ◽  
Author(s):  
Juana Lopez-Martinez ◽  
Edgar Alcantara-Razo ◽  
Sergio Hernandez-Vazquez ◽  
Ernesto Chavez
Keyword(s):  
Gulf Of California ◽  
Age Groups ◽  
Potential Yield ◽  
Natural Oscillations ◽  
Recruitment Pattern ◽  
Stock Recruitment ◽  
Age Structured ◽  
Stochastic Recruitment ◽  
Age Structured Model ◽  
Compensatory Effect

AbstractA stock of rock shrimp Sicyonia penicillata was assessed in a fishery recently opened at Bahoa Kino, Sonora, Mexico. An age-structured model with stochastic recruitment was developed, which considers growth rate, natural mortality, and fishing mortality by age. Age groups were followed year by year with a stock-recruitment Ricker function where the seasonal recruitment pattern was defined as well. Simulations might be interpreted as showing a stable population with four year cycles, reflecting a density-dependent process. In 1996, fishing intensity had an apparent compensatory effect on the stock, decreasing the amplitude of natural oscillations and maintaining the stock at a biomass level similar to the size observed in a condition of no exploitation. The stock was found currently underexploited. As a result of the seasonal accessibility and the age of first-catch fishing (adult shrimp), the stock might be capable to withstand high fishing pressure without being overexploited. Se evaluo una poblacion de camaron de roca Sicyonia penicillata, de una pesqueroa recientemente abierta en Bahoa Kino, Sonora, Mexico. Se desarrollo un modelo basado en la estructura por edades que considera reclutamiento estocastico, tasa de crecimiento, mortalidad natural y mortalidad por pesca por grupo de edad. Estos grupos de edad fueron determinados ano tras ano mediante la funcion de reclutamiento de Ricker, en los que tambien se definio el patron estacional de reclutamiento. Las simulaciones muestran una poblacion estable con ciclos de cuatro anos, que indican un proceso de densodependencia. En 1996, la intensidad de pesca tuvo un efecto compensatorio sobre la poblacion, reduciendo la amplitud de las oscilaciones naturales y manteniendo al stock en un nivel de biomasa similar al observado en la condicion sin explotacion. Se encontro que el recurso esta subexplotado. Como resultado de la accesibilidad estacional y de que la edad de primera captura corresponde a camaron adulto, el recurso soporta alta presion de pesca sin dar evidencias de sobreexplotacion.

An age-structured model with delay mortality

Biosystems ◽  
2005 ◽  
Vol 81 (3) ◽  
pp. 255-260
Author(s):  
J.M. Tchuenche
Keyword(s):  
Structured Model ◽  
Age Structured ◽  
Age Structured Model

scholarly journals The development and validation of an age-structured model for the evaluation of disease control strategies for intestinal helminths

Parasitology ◽  
1994 ◽  
Vol 109 (3) ◽  
pp. 389-396 ◽  
Author(s):  
M. S. Chan ◽  
H. L. Guyatt ◽  
D. A. P. Bundy ◽  
G. F. Medley
Keyword(s):  
Helminth Infection ◽  
Control Strategies ◽  
Intestinal Helminth ◽  
Intestinal Helminths ◽  
Parasite Control ◽  
Age Related ◽  
Control Programmes ◽  
Age Structured ◽  
Development And Validation ◽  
Age Structured Model

SummaryEpidemiological modelling can be a useful tool for the evaluation of parasite control strategies. An age-structured epidemiological model of intestinal helminth dynamics is developed. This model includes the explicit representation of changing worm distributions between hosts as a result of treatment, and estimates the morbidity due to heavy infections. The model is used to evaluate the effectiveness of different programmes of age-targeted community chemotherapy in reducing the amount of morbidity due to helminth infection. The magnitude of age-related heterogeneities is found to be very important in determining the results of age-targeted treatment programmes. The model was verified using field data from control programmes for Ascaris lumbricoides and Trichuris trichiura, and was found to provide accurate predictions of prevalence and mean intensities of infection during and following different control regimes.

The Life-History of Badumna-Candida (Araneae, Amaurobioidea)

1993 ◽  
Vol 41 (5) ◽  
pp. 441 ◽  
Author(s):  
MF Downes
Keyword(s):  
Sex Ratio ◽  
Egg Production ◽  
Production Cycle ◽  
Social Spider ◽  
Social Spiders ◽  
Primary Sex Ratio ◽  
The Social ◽  
The Status ◽  
History Of ◽  
Changes Over Time

A two-year study of the social spider Badumna candida at Townsville, Queensland, provided information on colony size and changes over time, maturation synchrony, temperature effects on development, sex ratio, dispersal, colony foundation, fecundity and oviposition. Key findings were that B. candida outbred, had an iteroparous egg-production cycle between March and October, had an even primary sex ratio and achieved maturation synchrony by retarding the development of males, which matured faster than females at constant temperature. There was no overlap of generations, the cohort of young from a nest founded by a solitary female in summer dispersing the following summer as subadults (females) or subadults and adults (males). These findings confirm the status of B. candida as a periodic-social spider (an annual outbreeder), in contrast to the few known permanent-social spider species whose generations overlap. Cannibalism, normally rare in social spiders, rose to 48% when spiders were reared at a high temperature. This may be evidence that volatile recognition pheromones suppress predatory instincts in social spiders.

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