Maintenance of genetic polymorphism under conditions of genotype-dependent growth and size-selective mortality

1985 ◽  
Vol 27 (3) ◽  
pp. 279-288 ◽  
Author(s):  
Robert A. Desharnais ◽  
David W. Foltz ◽  
E. Zouros
Keyword(s):  
Growth Rate ◽  
Mortality Rate ◽  
General Pattern ◽  
Fishing Effort ◽  
Minimum Size ◽  
Size Analysis ◽  
Fishing Mortality ◽  
Biochemical Basis ◽  
Important Species ◽  
Dependent Growth

Associations between heterozygosity at one or more electrophoretically detected enzyme loci and growth rate have been reported for several species of plants and animals, including several commercially important species of finfish and shellfish. The general pattern is for heterozygotes to grow faster than homozygotes, although there is some variation in growth response even within a species. Regardless of the physiological or biochemical basis of genotype-dependent growth, polymorphism at a locus affecting growth rate in an overdominant manner may be lost if larger individuals have a greater mortality rate than smaller ones. In an exploited population, mortality of this sort is likely to result from size-selective fishing pressure. Using a continuous-time single-locus model of natural selection, we have related the maintenance of polymorphism at a locus to two measures of fishing effort: β, the legal minimum size below which there is no mortality, and f, an instantaneous mortality rate owing to fishing (above the legal minimum size). We considered two different models of fishing mortality. In model 1, fishing mortality above the legal minimum size is constant; in model 2, fishing mortality is a linear function of size (above β). Numerical analysis of model 1 indicates that maintenance of polymorphism requires either a low rate of fishing mortality or a value of β that is close to zero or close to the maximum attainable size. Analysis of model 2 gives similar results, suggesting that the conclusions are not dependent on the exact form of the mortality function.Key words: heterozygosity, growth, size, mortality.

scholarly journals Growth Pattern, Mortality and Exploitation Rate of the Giant African Threadfin, Polydactylus quadrifilis (Cuvier, 1829) from Ebrié Lagoon (Potou Sector, Côte d’Ivoire)

2020 ◽  
pp. 33-42
Author(s):  
Théophile Aké Bédia ◽  
Bakari Coulibaly ◽  
Yao Aristide Konan ◽  
Essetchi Paul Kouamelan ◽  
Valentin N’douba
Keyword(s):  
Growth Rate ◽  
Mortality Rate ◽  
Growth Pattern ◽  
Total Mortality ◽  
Fishing Effort ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Population Parameters ◽  
Exploitation Rate ◽  
First Maturity

The study evaluated some population parameters of Polydactylus quadrifilis within Ebrié lagoon (Potou sector). Samples were obtained using artisanal gillnet fishery from April 2004 to March 2006. A total of 741 individuals of P. quadrifilis ranged from 11 to 70 cm were examined. Population parameters were estimated where asymptotic length (L∞) was found 60 cm, growth rate (K) 0.33 per year, the longevity (T max) 9.09 years, and growth performance index (Φ′) 3.06. The length at first capture (Lc50 = 10.60 cm) was lower than the length at first maturity (Lm50 = 40 cm). Total mortality rate (Z) was calculated as 1.10 per year including natural mortality and fishing mortality. The exploitation rate (E=0.36) was found to be less than the maximum exploitation rate (E max = 0.44) and indicated that P. quadrifilis is not overexploited. The current exploitation rate should be maintained by sustainable fisheries measures including monitoring of fishing effort.

Movement, Growth and natural mortality rate of the Red Spot King Prawn, Penaeus longistylus Kubo, from the Great Barrier Reef Lagoon

1990 ◽  
Vol 41 (3) ◽  
pp. 399 ◽  
Author(s):  
MCL Dredge
Keyword(s):  
Growth Rate ◽  
Mortality Rate ◽  
Great Barrier Reef ◽  
Annual Variation ◽  
Growth Parameters ◽  
Natural Mortality ◽  
Barrier Reef ◽  
Fishing Mortality ◽  
Nursery Areas ◽  
Reef Lagoon

Movement, growth and natural mortality rate of the red spot king prawn, Penaeus longistylus, occurring in waters of the Great Barrier Reef off Townsville, Queensland, were investigated in a series of tagging experiments. Adult P. longistylus did not migrate after leaving nursery areas. Their growth rate was slower than that of the conspecific species P. plebejus, and significant inter-annual variation in growth parameters was observed. The natural mortality rate, assessed by sequential tagging experiments that eliminated the possibility of confounding with the rate of fishing mortality, was estimated to be 0.072 (week-1).

scholarly journals Optimal fishing mortality assignment for southern hake Merluccius australis in Chile

2020 ◽  
Vol 48 (4) ◽  
pp. 613-625
Author(s):  
Felipe Lopez ◽  
Jorge Jimenez ◽  
Cristian Canales
Keyword(s):  
Mortality Rate ◽  
Economic Benefit ◽  
Mortality Rates ◽  
Fish Population ◽  
Fishing Effort ◽  
Economic Benefits ◽  
Historical Background ◽  
Total Catch ◽  
Fishing Mortality ◽  
Objective Functions

Since 1979, southern hake (Merluccius australis) has been exploited in Chile from the Bio Bio to the Magallanes regions, between the parallels 41°28.6'S and 57°S. There is evidence of a constant fishing effort and a sustained reduction of the fish population, consistent with a progressive decrease in total annual catches. Management strategies based on the maximum sustainable yield (MSY) and quota assignment/ distribution criteria have not been able to sustain acceptable biomass levels. A non-linear optimization model with two objective functions was proposed to determine an optimal total catch quota for more sustainable exploitation of this fishery. The first function maximizes the total catch over time in response to an optimal assignment of fishing mortality rates per fleet; the second function maximizes the total economic benefit associated with the total catch. The dynamics of the fish population were represented with the equations of a predictive age-structured model. Decision variables were fishing mortality rates and annual catch quotas per fleet, subject to constraints that guarantee a minimum level of biomass escape over a long-term period. The input parameters were obtained from the last stock evaluation report carried out by the Instituto de Fomento Pesquero (IFOP) of Chile. The historical background data of the fishery and the regulatory framework were relevant aspects of the methodology. Five scenarios were evaluated with the two objective functions, including a base scenario, which considered the referential mortality rate as input data as the average mortality rate per fleet from 2007 to 2012. Total economic benefits fluctuate between 102 and USD 442 million for total catches in the range of 108 to 421 thousand tons, which were obtained from maximizing the economic and biological objective functions. Economic benefit/catch ratios were reduced for scenarios with higher constraints on catch limits, and they were more efficient from a biological point of view. Situations with lighter constraints showed in general higher economic benefits and better performance ratios than those with stronger restrictions. The use of optimization models may provide a useful tool to evaluate the effect of regulations for adequate conservation and economical utilization of a limited resource.

The Effect of Reduction of Fishing Effort on Yield

1962 ◽  
Vol 19 (4) ◽  
pp. 521-529 ◽  
Author(s):  
Syoiti Tanaka
Keyword(s):  
Mortality Rate ◽  
Sudden Change ◽  
Japan Sea ◽  
Fish Population ◽  
Fishing Effort ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Yield Curves ◽  
Before And After ◽  
Steady Level

When a fish population has been depleted by heavy exploitation, with the yield from the population maintaining an unfavourable level, it is usual to expect that the situation will be improved by reduction of fishing effort. Following a sudden reduction of fishing mortality, p, from p1 to p2 at time τ = 0, the yield at once decreases and then increases gradually until it reaches another steady level higher than the former level.The present paper deals, using Baranov's model, with the transition stage of the population following a sudden change in p, as well as with the steady state before and after the change. Relations between equilibrium yield and fishing mortality rate (effort-yield curves) are calculated for various values of the parameters, λ0 (= l0/u, where l0 is the length of a recruit and u is the yearly increase in length), q (natural mortality rate), and b (remaining life span of a fish at the time of recruitment) (Fig. 2). It is noteworthy that for species that grow slowly after recruitment, i.e. when λ0 is large, reduction of fishing would have scarcely any effect on the yield (Fig. 4).Yield curves for the period of transition from the present to various lower levels of fishing are calculated for the case in which λ0 = 4, q = 0.15, b = 10 and p1 = 1.35. These represent parameters for the present state of the stock of sohachi flounders Cleisthenes herzensteini (Schmidt), in the southwestern area of the Japan Sea (Fig. 5).Possible density effects on growth rate and natural mortality rate, which are briefly discussed, appear to diminish considerably the effectiveness of any reduction in fishing effort (Fig. 6).

scholarly journals Multiyear tagging studies incorporating fishing effort data

1998 ◽  
Vol 55 (6) ◽  
pp. 1466-1476 ◽  
Author(s):  
John M Hoenig ◽  
Nicholas J Barrowman ◽  
William S Hearn ◽  
Kenneth H Pollock
Keyword(s):  
Mortality Rate ◽  
Additional Data ◽  
Survival Rates ◽  
Fishing Effort ◽  
Reporting Rate ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Recovery Rates ◽  
Sampling Survey ◽  
Tag Shedding

The Brownie models for multiyear tagging studies can be used to estimate age- and year-specific annual survival rates and tag recovery rates. The latter are composites of the exploitation rates and rates of tag reporting, tag shedding, and tag-induced mortality. It is possible to estimate the exploitation rates if the other components of the tag recovery rates can be quantified. Instantaneous rates of fishing and natural mortality can be estimated if information is available on the seasonal distribution of fishing effort. The estimated rates are only moderately dependent on the timing of the fishing; consequently, the relative effort data can be crude. Information on the timing of the catch over the course of the year can be used as a substitute for the effort data. Fishing mortality can also be assumed to be proportional to fishing effort over years; consequently, if fishing effort is known then the tag reporting rate, natural mortality rate, and a single catchability coefficient can be estimated (instead of natural mortality and a series of fishing mortalities). Although it is possible in theory to estimate both the tag reporting rate and the natural mortality rate with all of these models, in practice it appears necessary to obtain some additional data relating to tag reporting rate to obtain acceptable results. The additional data can come from a variable reward tagging study, a creel or port sampling survey, or from tagged animals that are secretly added to the fishers' catches.

Minimum Size Regulations and the Implications for Yield and Value in the Canadian Atlantic Halibut (Hippoglossus hippoglossus) Fishery

1989 ◽  
Vol 46 (11) ◽  
pp. 1899-1903 ◽  
Author(s):  
John D. Neilson ◽  
W. R. Bowering
Keyword(s):  
Mortality Rate ◽  
Size Composition ◽  
Minimum Size ◽  
Atlantic Halibut ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Hippoglossus Hippoglossus ◽  
Size Regulation ◽  
Size Limit ◽  
Yield Per Recruit

The effect of a minimum size regulation on yield and value per recruit in the Canadian Atlantic halibut fishery was examined. The model indicated that under most scenarios, the size limit would not result in increased yield per recruit. In general, yield per recruit was more sensitive to fishing mortality than age of first entry to the fishery. While reduced yields were usually associated with the minimum size limit, the value per recruit increased with increasing age at entry to the fishery until age 7. The changes in value per recruit reflected the size composition of landings following the imposition of the size limit and the different values associated with various size categories. Both yield and value per recruit were sensitive to the choice of the natural mortality rate.

scholarly journals BEBERAPA PARAMETER POPULASI UDANG PUTIH (Penaeus merguiensis de Mann) DI PERAIRAN TARAKAN, KALIMANTAN UTARA

2017 ◽  
Vol 9 (2) ◽  
pp. 85
Author(s):  
Umi Chodrijah ◽  
Ali Suman
Keyword(s):  
Mortality Rate ◽  
Total Mortality ◽  
Fishing Effort ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Population Parameters ◽  
Spawning Period ◽  
Exploitation Rate ◽  
First Maturity ◽  
Penaeus Merguiensis

Tingkat eksploitasi udang putih (Penaeus merguiensis) sangat intensif. Hal ini terindikasi dengan hasil tangkapan udang di WPP-NRI 716 selama 9 tahun terakhir meningkat. Tujuan penelitian ini untuk mengkaji beberapa parameter populasi dan aspek biologi udang putih di perairan Tarakan. Data panjang karapas dan tingkat kematangan gonad udang putih dikumpulkan dari tempat pendaratan udang di Selumit Pantai, Tarakan, Kalimantan Utara pada Januari sampai dengan November 2016. Pendugaan parameter populasi dengan aplikasi model analisis menggunakan program ELEFAN 1. Hasil penelitian menunjukkan rata-rata ukuran udang putih pertama kali tertangkap (Lc) pada panjang karapas 32,51 mm dan rata-rata ukuran pertama kali matang gonad 33,58 mm. Puncak musim pemijahan terjadi pada Maret dan Agustus. Laju pertumbuhan (K) sebesar 1,33 per tahun (betina) dan 1,55 per tahun (jantan). Laju kematian total (Z) sebesar 7,5 per tahun (betina) dan 8,85 per tahun (jantan), laju kematian alamiah (M) sebesar 1,82 per tahun (betina) dan 2,16 per tahun (jantan) serta laju kematian akibat penangkapan (F) sebesar 5,68 per tahun (betina) dan 6,69 per tahun (jantan). Laju pengusahaan (E) udang putih di perairan Tarakan adalah sebesar 0,76 per tahun. Hal ini menunjukkan tingkat pemanfaatan udang putih telah mengalami lebih tangkap (overfishing). Kondisi ini menggambarkan perlunya dilakukan pengurangan upaya sekitar 52 %.  The banana prawn (Penaeus merguiensis) have been exploited intensively. For instance, within nine years the number of shrimp production in FMA 716 increased dramatically. This research aims to identify the some population parameters of banana prawn in the Tarakan waters. This research was carried out from January to November 2016. Data were analyzed using the analytical model application with ELEFAN I. The result showed that the length at first capture (Lc) of banana prawn was 32,51 mmCL and the length at first maturity (Lm) was 33,58 mm CL. The peak season of spawning period was indicated on March and August. The growth rate (K) was 1,33 /year (female) and 1.55/year (male). Total mortality rate (Z) was 7.5/year (female) and 8,85/year (male), natural mortality rate (M) rate was 1.82/year (female) and 2.16/year (male) and fishing mortality rate ( F) were 5.68/ year (female) and 6.69/year (male). The exploitation rate (E) of banana prawn in the Tarakan waters was 0.76 per year. Therefore, level of existing fishing effort of the banana prawn should reduced about 52 % in the next year.

Tagging Returns, Age Studies and Fluctuations in Abundance of Lake Winnipeg Whitefish, 1931–1951

1954 ◽  
Vol 11 (3) ◽  
pp. 284-309 ◽  
Author(s):  
W. A. Kennedy
Keyword(s):  
Growth Rate ◽  
Mortality Rate ◽  
Weather Conditions ◽  
Fishing Effort ◽  
Coregonus Clupeaformis ◽  
Lake Winnipeg ◽  
Equal Strength ◽  
Age Studies ◽  
Annual Mortality ◽  
Age Determinations

On the basis of 2,003 lake whitefish, Coregonus clupeaformis, tagged in 1938, of which 126 were recovered during the next five years, there is evidence that fish released together tend to stay together for years, and that the proportion of a population captured during a certain time by a unit amount of fishing effort can fluctuate greatly (a plausible explanation is the effect of variations in weather conditions). On the basis of age determinations of 12,975 whitefish in samples taken annually from 1937 to 1951, growth rate was determined, the total annual mortality rate among fully exploited fish was calculated to be 64 per cent over several years, and it appeared that all year-classes had been of about equal strength in recent years. The generally accepted idea that fluctations in fishing success correspond to fluctuations in abundance of whitefish is probably erroneous. Possibly the Lake Winnipeg whitefish are underfished.

scholarly journals Yield per recruit of the peacock bass Cichla monoculus (Spix and Agassiz, 1831) caught in Lago Grande at Manacapuru (Amazonas – Brazil)

2014 ◽  
Vol 74 (1) ◽  
pp. 226-230 ◽  
Author(s):  
CP Campos ◽  
CEC Freitas
Keyword(s):  
Growth Parameters ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Minimum Size ◽  
Small Scale ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Yield Per Recruit ◽  
Peacock Bass ◽  
Actual Size

We evaluated the stock of peacock bass Cichla monoculus caught by a small-scale fishing fleet in Lago Grande at Manacapuru. The database was constructed by monthly samplings of 200 fish between February 2007 and January 2008. We measured the total length (cm) and total weight (gr) of each fish. We employed previously estimated growth parameters to run a yield per recruit model and analyse scenarios changing the values of the age of the first catch (Tc), natural mortality (M), and fishing mortality (F). Our model indicated an occurrence of overfishing because the fishing effort applied to catch peacock in Lago Grande at Manacapuru is greater than that associated with the maximum sustainable yield. In addition, the actual size of the first catch is almost half of the estimated value. Although there are difficulties in enforcing a minimum size of the catch, our results show that an increase in the size of the first catch to at least 25 cm would be a good strategy for management of this fishery.

scholarly journals Estimating fishing and natural mortality rates, and catchability coefficient, from a series of observations on mean length and fishing effort

2017 ◽  
Vol 75 (2) ◽  
pp. 610-620 ◽  
Author(s):  
Amy Y Then ◽  
John M Hoenig ◽  
Quang C Huynh
Keyword(s):  
Mortality Rate ◽  
Total Mortality ◽  
Fishing Effort ◽  
Residual Variance ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Norway Lobster ◽  
Rapid Growth Rate ◽  
Complex Models ◽  
The Mean

Abstract Gedamke and Hoenig (2006) (Transactions of the American Fisheries Society, 135: 476–487) developed a non-equilibrium version of the Beverton and Holt estimator of total mortality rate, Z, based on mean length and thereby increased the usefulness of length-based methods. In this study, we extend their model by replacing period-specific Z parameters with the year-specific parameterization Zy = qfy + M where q is the catchability coefficient, fy is the fishing effort in year y, F (=qf) is the fishing mortality rate, and M is the natural mortality rate. Thus, the problem reduces to estimating just three parameters: q, M and residual variance. We used Monte Carlo simulation to study the model behaviour. Estimates of q and M are highly negatively correlated and may or may not be reliable; however, the estimates of corresponding Z’s are more precise than estimates of F and are generally reliable, even when uncertainty about the mean lengths is high. This length-based method appears to work best for stocks with rapid growth rate. Contrast in effort data may not be necessary for reliable estimates of Z’s. This approach forms a bridge between data-limited models and more complex models. We apply the method to the Norway lobster Nephrops norvegicus stock in Portugal as an example.

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