Inferring the Summer Distribution of Migratory Pacific Hake (Merluccius productus) from Latitudinal Variation in Mean Lengths-at-Age and Length Frequency Distributions

1992 ◽  
Vol 49 (4) ◽  
pp. 708-721 ◽  
Author(s):  
Barry D. Smith ◽  
Gordon A. McFarlane ◽  
Mark W. Saunders
Keyword(s):  
Fish Population ◽  
Vancouver Island ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Merluccius Productus ◽  
The Mean ◽  
Summer Distribution ◽  
The Right ◽  
Mean Variance ◽  
Length Frequency Data

Average summer distribution of abundance and biomass for the migratory population of Pacific hake (Merluccius productus) is described by age, length, and latitude, based on a model proposing that (1) changes in mean length-at-age with latitude and (2) the nonnormal (skewed to the right) appearance of length-at-age distributions near southwest Vancouver Island could be caused by length-dependent migration velocities and changing migration velocity with latitude. Our model uses mean length-at-age data collected annually near four latitudes from California to Vancouver Island, length frequency data collected annually near southern Vancouver Island from 1978 until 1988, and hydroacoustic data collected triennialiy from 1977 until 1986. We conclude that (1) hake slow their northward migration from the spawning grounds off southern California as they approach the productive feeding grounds off southwestern Vancouver Island, (2) older (larger) hake migrate further north than younger (smaller) hake, and (3) older hake are more abundant in Canadian waters than younger hake. Although all three conclusions have previously been partly substantiated, we show that seemingly undramatic patterns in the mean, variance, and distribution of lengths-at-age can be remarkably revealing about the distribution of a migrating fish population.

Reference points for the length-based indicator Lmax5% for use in the assessment of data-limited stocks

2019 ◽  
Vol 76 (7) ◽  
pp. 2125-2139 ◽  
Author(s):  
Tanja Miethe ◽  
Yves Reecht ◽  
Helen Dobby
Keyword(s):  
Life Histories ◽  
Stock Assessment ◽  
Reference Points ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Simulation Tools ◽  
Spawning Potential Ratio ◽  
The Mean ◽  
Commercial Sources ◽  
Length Frequency Data

Abstract In the absence of abundance indices from scientific surveys or commercial sources, reliable length frequency data from sampled commercial catches can be used to provide an indirect assessment of fishing mortality. Length-based indicators are simple metrics which describe length frequency distributions. The length-based indicator Lmax5%, the mean length of the largest 5% of individuals in the catch, combined with appropriately selected reference points, can be used to evaluate the presence of very large individuals in the catch and hence determine exploitation level. Using analytical per-recruit models, we derive reference points consistent with a spawning potential ratio of 40%. The reference points depend on the life history parameters for natural mortality, maturity, and growth (M, Lmat, L∞, k, CVL∞). Using available simulation tools, we investigate the sensitivity of the reference points to errors in these parameters and explore the usefulness of particular reference points for management purposes for stocks with different life histories. The proposed reference points are robust to uncertainty in length at first capture, Lc, and take into account the maturation schedule of a species. For those stocks with high M/k ratios (>1), Lmax5%, combined with the appropriate reference point, can be used to provide a data-limited stock assessment.

Length-weight relationship, growth and mortality ofAnadara granosain Penang Island, Malaysia: an approach using length-frequency data sets

2014 ◽  
Vol 95 (2) ◽  
pp. 381-390 ◽  
Author(s):  
Mohammad Reza Mirzaei ◽  
Zulfigar Yasin ◽  
Aileen Tan Shau Hwai
Keyword(s):  
Growth Parameters ◽  
Total Mortality ◽  
Growth Function ◽  
Data Sets ◽  
Frequency Data ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Weight Relationship ◽  
Logarithmic Relationship ◽  
Length Frequency Data

Length-weight relationship, growth parameters and mortality rates ofAnadara granosain the intertidal zone of Balik Pulau, Penang Island, West Coast of Malaysia were investigated based on monthly length-frequency data (December 2011 to November 2012). A total of 548 individuals ranging from 11.25 to 33.13 mm size were subjected to analysis. Logarithmic relationship between the length and weight was LogW = 2.328LogL − 2.537 (R2 = 0.922) for combined sexes. From this equation it was clear that the exponent ‘b’ value forA. granosashowed a negative allometric growth (b < 3). A von Bertalanffy growth function with an asymptotic length (L∞) of 35.40 mm and a growth constant (K) of 1.1 year−1was established from length frequency distributions. Thet0(−0.140) was estimated by substituting theL∞andKin the Pauly's equation. The sizes attained byA. granosawere 10.13, 14.36, 17.89, 20.82, 23.56 and 25.29 mm at the end of 2, 4, 6, 8, 10 and 12 months, respectively. The estimated growth performance index (Ø) was 3.13 while the estimated lifespan of the cockles was about 2.72 years at the study area. The estimated value of total mortality based on length-converted catch curve wasZ = 3.02 year−1. The natural mortality (M) and fishing mortality (F) rates were 1.84 and 0.48 year−1, respectively. The exploitation level (E) ofA. granosawas 0.20, which indicated slight fishing pressure on the stock.

Concentrations of Diazepam and Nordiazepam in 1000 Blood Samples From Apprehended Drivers—Therapeutic Use or Abuse of Anxiolytics?

2012 ◽  
Vol 26 (3) ◽  
pp. 198-203 ◽  
Author(s):  
Alan W. Jones ◽  
Anita Holmgren
Keyword(s):  
Total Concentration ◽  
Forensic Toxicology ◽  
Parent Drug ◽  
Driving Under The Influence ◽  
Primary Metabolite ◽  
Blood Samples ◽  
Frequency Distributions ◽  
The Mean ◽  
Capillary Column Gas Chromatography ◽  
The Right

Using an in-house forensic toxicology database, we selected 1000 cases of driving under the influence of drugs (DUIDs) over a 12-month period if diazepam (D) and nordiazepam (ND) were both present in the blood samples. Quantitative analysis of D and ND in blood was done by solvent extraction (butyl acetate) and capillary column gas chromatography (GC) with a nitrogen–phosphorous (N-P) detector. The limits of quantitation of this analytical method for D and ND in blood were 0.05 mg/L. The correlation between D and ND concentrations in blood was statistically significant ( r = .58, P < .001), as expected for a parent drug and its primary metabolite. However, the frequency distributions were markedly skewed to the right with mean (median) and highest concentrations of 0.37 (0.20) and 6.1 mg/L for D and 0.39 (0.20) and 5.6 mg/L for ND. The mean (median) total concentration (D + ND) was 0.76 mg/L (0.50 mg/L), and the concentration ratios D/ND and ND/D were 1.29 (median 0.95) and 1.41 (median 1.06), respectively. In 90 cases (9%), the concentration of D in blood exceeded 0.83 mg/L, which corresponds to an upper therapeutic limit in plasma (∼1.5 mg/L), assuming a plasma/blood distribution ratio of 1.8:1.

scholarly journals Growth, Mortality and Exploitation Levels of Sphyraena sphyraena (Pisces: Sphyraenidae) and Apsilus fuscus (Pisces: Lutjanidae) in Ghanaian Waters

2021 ◽  
Vol 2 (1) ◽  
pp. 16-23
Author(s):  
Joseph Aggrey-Fynn ◽  
Divine Worlanyo Hotor
Keyword(s):  
Growth Parameters ◽  
Total Mortality ◽  
Growth Function ◽  
Frequency Data ◽  
Length Frequency ◽  
Fish Stocks ◽  
Von Bertalanffy Growth Function ◽  
Inshore Waters ◽  
The Mean ◽  
Length Frequency Data

Sphyraena sphyraena (Linnaeus, 1758) and Apsilus fuscus (Valenciennes, 1830) are commercially important fish species in Ghana. The stocks are exploited mainly by the artisanal and semi-industrial fisheries. Growth and mortality rates, and exploitation levels of the two stocks in inshore waters of Ghana were assessed as a contribution to fill the knowledge gap on the species. Samples were obtained from three landing sites along the coast of Ghana from February to July, 2017. Length-frequency data were used to estimate growth, mortality and exploitation ratios. The modal class for S. sphyraena was 37.0–39.9 cm total length (TL) and 34.0–35.9 cm TL for A. fuscus. The length and weight relationships established that growth in S. sphyraena was negative allometric, whereas that of A. fuscus was isometric. The estimated growth parameters from the length frequency data fitted with the von Bertalanffy growth function were asymptotic length (L∞) of 69.9 cm TL for S. sphyraena and 53.5 cm TL for A. fuscus. The growth constant (K) was calculated as 1.64 yr-1 for S. sphyraena and 0.50 yr-1 for A. fuscus. The mean length-at-first capture (Lc) was found to be lower than the mean length at sexual maturity (Lm) for both species. The sex ratio showed a dominance of females over males in S. sphyraena, and 1:1 for A. fuscus. The total mortality rate (Z) for S. sphyraena was more than for A. fuscus. The estimated natural mortality (M) was 1.88 yr-1 for S. sphyraena and 0.74 yr-1 for A. fuscus whilst fishing mortality (F) rate was 3.04 yr-1 for S. sphyraena and 0.93 yr-1 for A. fuscus. The exploitation ratio showed that both fish stocks were exploited over the optimum levels. The estimated population parameters of the species obtained from the study, therefore, might be useful for the sustainable management of the stocks.

scholarly journals A remark on some extensions of the mean-variance portfolio selection models

2021 ◽  
Vol 16 (3) ◽  
pp. 26-34
Author(s):  
Enrico Moretto ◽  
Keyword(s):  
Portfolio Management ◽  
Proper Time ◽  
Research Question ◽  
The Third ◽  
Management Techniques ◽  
The Common ◽  
The Mean ◽  
Mean Variance Portfolio ◽  
The Right ◽  
Mean Variance

Quantitative risk management techniques should prove their efficacy when financially turbulent periods are about to occur. Along the common saying “who needs an umbrella on a sunny day?”, a theoretical model is really helpful when it carries the right suggestion at the proper time, that is when markets start behaving hecticly. The beginning of the third decade of the 21st century carried along a turmoil that severely affected worldwide economy and changed it, probably for good. A consequent and plausible research question could be this: which financial quantitative approaches can still be considered reliable? This article tries to partially answer this question by testing if the mean-variance selection model (Markowitz [16], [17]) and some of his refinements can provide some useful hints in terms of portfolio management.

Changes in growth of juvenile southern bluefin tuna (Thunnus maccoyii): an analysis of length-frequency data from the Australian fishery

2000 ◽  
Vol 51 (2) ◽  
pp. 143 ◽  
Author(s):  
George M. Leigh ◽  
William S. Hearn
Keyword(s):  
Modal Analysis ◽  
Growth Rates ◽  
Bluefin Tuna ◽  
Frequency Data ◽  
Length Frequency ◽  
Southern Bluefin Tuna ◽  
History Of ◽  
The Mean ◽  
Western Australian ◽  
Length Frequency Data

Modal analysis is applied to historical length–frequency records of the Australian southern bluefin tunafishery, in order to quantify the variation in mean length from year to year. In the South Australian fishery in the first half of March, the mean length has ranged between 54 cm and 64 cm for 1-year-old fish, 73 cm and 85 cm for 2-year-old fish, and 85 cm and 100 cm for 3-year-old fish. The mean lengths of 2-, 3- and 4-year-old fish, and the increment from age 1 to age 3, have increased substantially over the history of the fishery. This increase in growth is probably a response to a decline in the population due to heavy fishing. In many years in the Western Australian fishery, two or more groups of 1-year-old fish were found: the mean lengths of these groups typically differed by 10 cm. Growth rates also varied markedly according to the season of the year.

scholarly journals Abundance, seasonality and size of Atlantic salmon smolts entrained on power station intake screens in the Severn Estuary

1994 ◽  
Vol 74 (3) ◽  
pp. 527-534 ◽  
Author(s):  
P.N. Claridge ◽  
I.C. Potter
Keyword(s):  
Atlantic Salmon ◽  
Standard Length ◽  
Condition Factor ◽  
Early Summer ◽  
Length Frequency ◽  
Power Station ◽  
Severn Estuary ◽  
Frequency Distributions ◽  
The Mean ◽  
One Year

Atlantic salmon smolts were sampled from the intake screens of the Oldbury power station in the inner Severn Estuary at weekly intervals between July 1972 and June 1977. These catches, and those taken over nearly three years from the nearby Berkeley power station, demonstrated that the abundance of smolts in the estuary peaked in autumn (October) and, to a far greater extent, in spring (April and May). However, small numbers of smolts were occasionally found in all other months of the year except July. Standard length-frequency distributions of smolts remained unimodal throughout the year. Lengths ranged from 76 to 187 mm, mean 130·2 ±1·87 mm (95% CL), and wet weights ranged from 5·4 to 68·0 g, mean 26·9 ±1·17 g. The mean monthly standard length of smolts increased slightly between the autumn of one year and the spring/early summer of the next year, suggesting that, on average, the former were six months younger than the latter. The condition factor was significantly greater in autumn (1·40) than in spring (1·23). It is estimated that the total number of salmon smolts entrained annually on the screens at Oldbury during the five years ranged from 92 to 791, with a mean of 405. Total estimated numbers at Berkeley ranged from 196 to 788 per annum. The numbers at Oldbury are lower than those estimated for the downstream migrants of the Twaite shad, another anadromous species, and far lower than those of the most abundant of the marine fish species that use the Severn Estuary as a nursery area.

scholarly journals A study of the life history of Brazilian sardine, Sardinella brasiliensis: IV. Distribution and abundance of sardine larvae

1977 ◽  
Vol 26 (2) ◽  
pp. 219-247 ◽  
Author(s):  
Yasunobu Matsuura
Keyword(s):  
Relative Abundance ◽  
Larval Abundance ◽  
Frequency Data ◽  
Length Frequency ◽  
Depth Zone ◽  
Average Temperature ◽  
History Of ◽  
The Mean ◽  
Egg Abundance ◽  
Length Frequency Data

Data on distribution and abundance of larvae of the Brazilian sardine, Sardinella brasiliensis, are presented based on samples collected in waters off southern Brazil during 1969 to 1971. The distribution pattern and relative abundance of sardine larvae during three spawning seasons are discussed. Relative abundance, using regional census estimates, was calculated each year. In general, larval abundance in each subarea coincided with that of eggs, although the area of distribution of larvae was larger than the spawning area. Estimates of larval abundance showed that the 1970-71 spawning season was the poorest, both in larval and egg abundance, despite the enlarged size of the area surveyed. The average temperature at stations where sardine larvae occurred was 23.4º C, ranging from 14.6 to 27.4º C, and the average salinity was 35.6º /oo, ranging from 35.0 to 36.7º /oo. Distribution of the larvae in different depth zones was analysed. Larvae usually were most abundant in the 51-100 m depth zone. No tendency for a unidirectional transport of larvae was observed; apparently they move from the spawning ground in all possible directions, spreading over the continental shelf. An estimate of survival rate of larvae, based on length frequency data pooled from the three years, was calculated. Undersampling of larvae during daytime was observed. The mean night-day catch ratio, based on larvae from all length classes sampled, was 3.93.

scholarly journals Estimating growth parameters and growth variability from length frequency data using hierarchical mixture models

2019 ◽  
Vol 76 (7) ◽  
pp. 2150-2163
Author(s):  
Luke Batts ◽  
Cóilín Minto ◽  
Hans Gerritsen ◽  
Deirdre Brophy
Keyword(s):  
Mixture Models ◽  
Growth Parameters ◽  
Growth Parameter ◽  
Melanogrammus Aeglefinus ◽  
Parameter Estimates ◽  
Frequency Data ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Growth Variability ◽  
Length Frequency Data

Abstract Analysis of length frequency distributions from surveys is one well-known method for obtaining growth parameter estimates where direct age estimates are not available. We present a likelihood-based procedure that uses mixture models and the expectation–maximization algorithm to estimate growth parameters from length frequency data (LFEM). A basic LFEM model estimates a single set of growth parameters that produce one set of component means and standard deviations that best fits length frequency distributions over all years and surveys. The hierarchical extension incorporates bivariate random effects into the model. A hierarchical framework enables inter-annual or inter-cohort variation in some of the growth parameters to be modelled, thereby accommodating some of the natural variation that occurs in fish growth. Testing on two fish species, haddock (Melanogrammus aeglefinus) and white-bellied anglerfish (Lophius piscatorius), we were able to obtain reasonable estimates of growth parameters, as well as successfully model growth variability. Estimated growth parameters showed some sensitivity to the starting values and occasionally failed to converge on biologically realistic values. This was dealt with through model selection and was partly addressed by the addition of the hierarchical extension.

Movements and growth of tagged Blue Endeavour Prawns, Metapenaeus endeavouri (Schmitt 1926), in the Western Gulf of Carpentaria, Australia

1992 ◽  
Vol 43 (5) ◽  
pp. 1283 ◽  
Author(s):  
RC Buckworth
Keyword(s):  
Growth Parameters ◽  
Fishing Effort ◽  
Parameter Estimates ◽  
Von Bertalanffy ◽  
Length Frequency ◽  
Von Bertalanffy Model ◽  
The Mean ◽  
Adult Habitat ◽  
Mean Time ◽  
Length Frequency Data

Mark-recapture experiments, conducted near Groote Eylandt in the western Gulf of Carpentaria during 1984, were used to examine movements and growth of blue endeavour prawns, Metapenaeus endeavouri. The mean distance moved by tagged animals was only 12.7 (s.e.�1.0) km, but a few were recaptured > 100 km from their release sites. The mean time at liberty was 36.8 (�1.6) days, the maximum being 155 days. The distance and speed of movements were not related to the size or sex of tagged prawns. Nonuniform recapture patterns corresponded largely with fishing effort. Recaptures per unit effort (R/f analyses), used to account for nonuniform fishing effort, indicated that there was no directionality in movements. Thus, tagged specimens of M. endeavouri dispersed slowly across suitable adult habitat, with limited intermixing of adults from stocks around Groote Eylandt. Estimates of the von Bertalanffy growth parameters L∞ and K for each sex were obtained for data from summer and winter releases. The fit of the von Bertalanffy model to summer data was limited by the small number of recaptures. The fit of the model to winter data was improved by removing early recaptures, and these estimates are presented as the primary descriptors of growth in M. endeavouri. Parameter estimates did not differ significantly between seasons, but L∞ differed between sexes and K differed between sexes in winter. Predicted growth corresponded to the progression of modes in length-frequency data from commercial catches.

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