scholarly journals Evaluación de la pesquería de Lutjanus peru (Pisces: Lutjanidae) de . Guerrero, México

1969 ◽  
pp. 571-580
Author(s):  
Apolinar Santamaría ◽  
Ernesto A Chávez
Keyword(s):  
Growth Model ◽  
Population Analysis ◽  
Small Fish ◽  
Natural Mortality ◽  
Von Bertalanffy ◽  
Cohort Size ◽  
Virtual Population ◽  
Von Bertalanffy Growth Model ◽  
Parameter Values ◽  
Yield Per Recruit

Red snapper (Lutjanus peru) fishery was analyzed from landings and catch records. Stock age structure was reconstructed after the parameter values of the von Bertalanffy growth model, the length-weight relationship, ages and the natural mortality coefficient through each of nine years of cateh records. The Pisat software package was applied to assess population parameters, whose estimates are, for the von Bertalanffy growth model, K = 0. 1 442 to 0.38; lo = -0.2; L = 87 cm; W = 9.4 Kg, and the natural mortality coefficient (M) afier several methods (0. 14 to 0.38). Cohort size was assessed by the virtual population analysis (VPA), estlmating population size in 5.2* 1 06 fish with a biomass of 8 454 tonnes. Current fishing mortality P, ranges from 0.06 to 1 . 1 3, depending upon the chosen M value; according to this, when the M value used is low, the results suggest that the stock is nnderexploited, and vice versa. The yield per recruit model applied suggests improvements to the management strategy. The model indicates recruit overfishing because very small fish are the main target (te

scholarly journals EDAD, CRECIMIENTO Y MORTALIDAD DE LUTJANUS PURPUREUS POEY, 1867 (PISCES: LUTJANIDAE) DE LA REGION DE GUAYANAS

2016 ◽  
Vol 27 ◽  
Author(s):  
Leo W. González ◽  
Nora Eslava ◽  
Carlos Silva
Keyword(s):  
Growth Model ◽  
Age Groups ◽  
Total Mortality ◽  
Growth Curves ◽  
Model Parameters ◽  
Natural Mortality ◽  
Von Bertalanffy ◽  
Research Survey ◽  
Curve Method ◽  
Von Bertalanffy Growth Model

Age, growth and mortality of the red snapper, Lutjanus purpureus Poey, 1867, were estimated based on lecture of 152 urohials of 1561 individuals caught in the region of Guianas, located between 06° - 10° LN and 54° - 61° LW, in 1988, by means of a research survey of the B/l "Dr. Fridtjof Nansen". Seven age groups could be distinguished within the annual zones of the urohial. The theoretical growth curves was adjusted according to the values of the von Bertalanffy growth model parameters: L„ = 91.99 cm ; K = 0.245 per year; to = - 0.499 yr. The values of natural mortality M = 0.255, were obtained using the equation of Taylor; and total mortality Z = 0.703 per year, by aplication of the linearized catch curve method.

Virtual Population Analysis (VPA) Equations for Nonhomogeneous Populations, and a Family of Approximations Including Improvements on Pope's Cohort Analysis

1986 ◽  
Vol 43 (12) ◽  
pp. 2406-2409 ◽  
Author(s):  
Alec D. MacCall
Keyword(s):  
Mortality Rate ◽  
Population Analysis ◽  
Seasonal Pattern ◽  
Cohort Analysis ◽  
Natural Mortality ◽  
Close Approximation ◽  
Virtual Population Analysis ◽  
Virtual Population ◽  
Special Case

A set of "backward" virtual population analysis (VPA) equations relates catch (Ct) from continuous fishing between times t and t + 1 to population n size (Nt, Nt+1) when a portion of the stock is unavailable to fishing. The usual VPA equations become a special case where the entire stock is available (i.e. the stock is homogeneous). A close approximation to the VPA equations is Nt = Nt+1 exp(M) + CtM/(1 − exp(−M)), which has properties similar to Pope's "cohort analysis" and is somewhat more accurate in the case of a continuous fishery, especially if the natural mortality rate (M) is large. Much closer simple approximations are possible if the seasonal pattern of catches is known.

Growth of the saucer scallop, Amusium japonicum balloti Habe, in central eastern Queensland

1981 ◽  
Vol 32 (4) ◽  
pp. 657 ◽  
Author(s):  
MJ Williams ◽  
MCL Dredge
Keyword(s):  
Growth Model ◽  
Larval Stage ◽  
Size Range ◽  
Von Bertalanffy ◽  
Commercial Fishery ◽  
Long Distance ◽  
Von Bertalanffy Growth Model ◽  
Central Eastern

Tag-recapture data were used to determine growth and movement of A. japonicum balloti. The von Bertalanffy growth model was found to be suitable for describing growth in the latter half of the size range for A. japonicum balloti, and estimated S∞ of scallops varied with year and area. A. japonicum balloti grows rapidly, being recruited to the commercial fishery at about 6 months of age in some cases. Recapture data indicated that A. japonicum balloti does not undergo long-distance displacements in its post-larval stage.

Modelling individual variability in growth of bull trout in the Walla Walla River Basin using a hierarchical von Bertalanffy growth model

2016 ◽  
Vol 27 (1) ◽  
pp. 103-115 ◽  
Author(s):  
Julianne E. Harris ◽  
Courtney Newlon ◽  
Philip J. Howell ◽  
Ryan C. Koch ◽  
Steven L. Haeseker
Keyword(s):  
River Basin ◽  
Growth Model ◽  
Individual Variability ◽  
Bull Trout ◽  
Von Bertalanffy ◽  
Von Bertalanffy Growth Model ◽  
Walla Walla

Length-at-Age Analysis: Can You Get What You See?

1992 ◽  
Vol 49 (4) ◽  
pp. 632-643 ◽  
Author(s):  
T. J. Mulligan ◽  
B. M. Leaman
Keyword(s):  
Growth Model ◽  
Time Trend ◽  
Single Point ◽  
Mortality Rates ◽  
Individual Growth ◽  
Parameter Estimates ◽  
Von Bertalanffy ◽  
Model Ambiguity ◽  
Von Bertalanffy Growth Model ◽  
Single Set

Observations at a single point in time of length-at-age (LAA) for a long-lived rockfish (Sebastes alutus) show that old fish are shorter than intermediate-aged fish. Fitting of a von Bertalanffy growth model to these data produces a systematic trend in the residual of observed versus calculated LAA. We examined how such LAA data can lead to erroneous conclusions about individual growth, and whether asymptotic growth can give rise to such data. We considered two hypotheses: (i) that a time trend in growth rate resulted in larger fish in more recent years and (ii) that there are multiple growth types, where growth and mortality rates are directly related. Using a general growth model that incorporated both (i) and (ii), we show that both hypotheses can generate data identical to those for the rockfish. A single set of LAA data is inadequate for describing individual growth; however, if sufficient data are available, model ambiguity can be resolved and reasonable parameter estimates obtained. Analysis of the rockfish data indicates that (ii) is more likely to explain the observations than (i). We show how fisheries on such species may preclude our understanding these biological relationships.

scholarly journals Estimation of the age-specific rate of natural mortality for Shetland sandeels

2004 ◽  
Vol 61 (2) ◽  
pp. 159-164 ◽  
Author(s):  
R.M. Cook
Keyword(s):  
Survey Data ◽  
Population Analysis ◽  
Mean Value ◽  
Specific Rate ◽  
Natural Mortality ◽  
The North ◽  
Virtual Population ◽  
Stock Assessments ◽  
The North Sea ◽  
The Mean

Abstract It is generally difficult to obtain reliable direct estimates of natural mortality, M, from conventional fisheries data and stock assessments. However, as a result of the closure of the Shetland sandeel (Ammodytes marinus) fishery from 1991 to 1994 and in the absence of any significant fishery in other years, research vessel survey data offer a rare opportunity to obtain estimates of M directly. A model is described that assumes that M can be decomposed into an age effect and year effects. Application of the model to the survey data produces values of M that decline from 2.1 for 0-group fish to 0.6 at age 2. There is some indication of an increase for ages 4 and older. Although there does not appear to be an overall trend in the mean value of M for the period 1985–1999, the annual values change by up to 50%. The values calculated from the model are in line with estimates obtained for the North Sea from multispecies virtual population analysis (MSVPA).

scholarly journals Conditional Ulam stability and its application to von Bertalanffy growth model

2022 ◽  
Vol 19 (3) ◽  
pp. 2819-2834
Author(s):  
Masakazu Onitsuka ◽  
Keyword(s):  
Numerical Simulations ◽  
Growth Model ◽  
Von Bertalanffy ◽  
Ulam Stability ◽  
Von Bertalanffy Growth Model

<abstract><p>The purpose of this paper is to apply conditional Ulam stability, developed by Popa, Rașa, and Viorel in 2018, to the von Bertalanffy growth model $ \frac{dw}{dt} = aw^{\frac{2}{3}}-bw $, where $ w $ denotes mass and $ a &gt; 0 $ and $ b &gt; 0 $ are the coefficients of anabolism and catabolism, respectively. This study finds an Ulam constant and suggests that the constant is biologically meaningful. To explain the results, numerical simulations are performed.</p></abstract>

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