A Bayesian approach for overcoming inconsistencies in mortality estimates using, as an example, data for Acanthopagrus latus

2004 ◽  
Vol 61 (7) ◽  
pp. 1202-1211 ◽  
Author(s):  
Norman G Hall ◽  
S Alex Hesp ◽  
Ian C Potter
Keyword(s):  
Life History ◽  
Bayesian Approach ◽  
Growth Parameters ◽  
Probability Distributions ◽  
Total Mortality ◽  
Growth Parameter ◽  
Life History Parameters ◽  
Acanthopagrus Latus ◽  
Marine Embayment ◽  
Mortality Estimates

Reliable estimates of natural (M) and total mortality (Z) are essential for effective fisheries management. However, estimates of M, which are frequently determined from life history parameters, are imprecise and often inconsistent with the values of Z derived from life history parameters and other analyses. This is exemplified by the mortality estimates derived for Acanthopagrus latus in a large marine embayment. Thus, such estimates, calculated for M for this population from a growth parameter and from growth parameters and water temperature, were both 0.70·year–1, whereas those for Z, calculated from maximum recorded age, relative abundance analysis, and a simulation based on maximum age and sample size, ranged from 0.18 to 0.30·year–1. These results are clearly inconsistent. A Bayesian approach was therefore developed that combines the posterior probability distributions of the various mortality estimates and thereby produces integrated and consistent estimates for M and Z. The application of our Bayesian approach to the data for A. latus yielded lower values for M than for Z. Our approach is equally applicable to other fish species.

Effect of trawling on juvenile red snapper (Lutjanus campechanus) habitat selection and life history parameters

2008 ◽  
Vol 65 (11) ◽  
pp. 2399-2411 ◽  
Author(s):  
R. J. David Wells ◽  
James H. Cowan, ◽  
William F. Patterson ◽  
Carl J. Walters
Keyword(s):  
Life History ◽  
Red Snapper ◽  
Lutjanus Campechanus ◽  
Daily Growth ◽  
Life History Parameters ◽  
Probability Of Survival ◽  
Natural Reef ◽  
Mortality Estimates ◽  
Lower Production ◽  
Ontogenetic Habitat Shifts

This study documents ontogenetic habitat shifts of red snapper ( Lutjanus campechanus ) and highlights possible impacts of shrimp trawling on age-0 fish life history parameters on the northern Gulf of Mexico (GOM) continental shelf. Red snapper were collected quarterly during 2004 and 2005 over sand, low-relief shell rubble, high-relief shell rubble, and natural high-relief reef habitats within a de facto nontrawl area and in similar habitats on the open shelf where commercial shrimp trawling occurred. Age-0 red snapper were most dense over sand and low-relief shell rubble habitats and moved to higher-relief shell rubble and natural reef habitats by age-1. Habitat-specific daily growth rates of age-0 fish were highest over sand (range 0.65–1.03 mm·day–1). Densities of age-0 red snapper were highest over trawled sand, but higher over nontrawled shell rubble by 6 months of age (age-0.5+). Red snapper collected over sand and low-relief shell rubble areas exposed to trawling had truncated size distributions, higher mortality estimates, and lower production potential (the latter evaluated with G–Z and P–B ratios) compared with fish over nontrawled areas of similar habitat. Results suggest that juvenile red snapper residing over nontrawled areas may have a higher probability of survival than fish in areas exposed to commercial shrimp trawling.

Using r-K Selection Theory to Predict Natural Mortality

1980 ◽  
Vol 37 (12) ◽  
pp. 2266-2271 ◽  
Author(s):  
Donald R. Gunderson
Keyword(s):  
Body Weight ◽  
Life History ◽  
Growth Parameters ◽  
Stepwise Multiple Regression ◽  
Natural Mortality ◽  
Instantaneous Rate ◽  
Life History Parameters ◽  
Selection Theory ◽  
Weight Index ◽  
Body Weight Index

Theory on r-K selection is used as a basis for examining correlations between instantaneous rate of natural mortality (M), gonad-body weight index, age at maturity, longevity, and Bertalanffy growth parameters (k, L∞) for 10 species of marine fish. All correlations were consistent with r-K selection theory. The gonad-body weight index was found to be more highly correlated with M than any of the other life history parameters examined (r2 = 0.62), and stepwise multiple regression showed that additional variables added little to the predictive ability of the model. The gonad-body weight index appears to be quite useful in predicting M, and development of an analogous index on an energetics basis might enhance its utility in this regard.Key words: natural mortality, r-K selection, life history parameters

scholarly journals Properties of age compositions and mortality estimates derived from cohort slicing of length data

2014 ◽  
Vol 72 (1) ◽  
pp. 44-53 ◽  
Author(s):  
Lisa E. Ailloud ◽  
Matthew W. Smith ◽  
Amy Y. Then ◽  
Kristen L. Omori ◽  
Gina M. Ralph ◽  
...  
Keyword(s):  
Growth Parameters ◽  
Age Groups ◽  
Total Mortality ◽  
Frequency Distributions ◽  
Accuracy And Precision ◽  
High K ◽  
Length Data ◽  
High Age ◽  
Low K ◽  
Mortality Estimates

Abstract Cohort slicing can be used to obtain catch-at-age data from length frequency distributions when directly measured age data are unavailable. The procedure systematically underestimates the relative abundance of the youngest age groups and overestimates abundance at older ages. Cohort-sliced catch-at-age data can be used to estimate total mortality rate (Z) using a regression estimator or the Chapman–Robson estimator for right truncated data. However, the effect of cohort slicing on accuracy and precision of resulting Z estimates remains to be determined. We used Monte Carlo simulation to estimate the per cent bias and per cent root mean square error of the unweighted regression, weighted regression, and Chapman–Robson mortality estimators applied to cohort-sliced data. Incompletely recruited age groups were truncated from the cohort-sliced catch-at-age data using previously established recommendations and a variety of plus groups was used to combine older age groups. The sensitivity of the results to a range of plausible biological combinations of Z, growth parameters, recruitment variability, and length-at-age error was tested. Our simulation shows that cohort slicing can work well in some cases and poorly in others. Overall, plus group selection was more important in high K scenarios than it was in low K scenarios. Surprisingly, defining the plus group to start at a high age worked well in some cases, although length and age are poorly correlated for old ages. No one estimator was uniformly superior; we therefore provide recommendations concerning the appropriate estimator and plus group to use, depending on the parameters characterizing the stock. We further recommend that simulations be performed to determine exactly which plus group would be most appropriate given the scenario at hand.

scholarly journals A stepwise stochastic simulation approach to estimate life history parameters for data-poor fisheries

2016 ◽  
Vol 73 (12) ◽  
pp. 1874-1884 ◽  
Author(s):  
Marc O. Nadon ◽  
Jerald S. Ault
Keyword(s):  
Life History ◽  
Stock Assessment ◽  
Probability Distributions ◽  
Size Composition ◽  
History Data ◽  
Life History Parameters ◽  
Life History Data ◽  
Novel Approach ◽  
Cost Efficient ◽  
Species Specific

Coastal fisheries are typically characterized by species-rich catch compositions and limited management resources, which typically leads to notably data-poor situations for stock assessment. Some parsimonious stock assessment approaches rely on cost-efficient size composition data, but these also require estimates of life history parameters associated with natural mortality, growth, and maturity. These parameters are unavailable for most exploited stocks. Here, we present a novel approach that uses a local estimate of maximum length and statistical relationships between key life history parameters to build multivariate probability distributions that can be used to parameterize stock assessment models in the absence of species-specific life history data. We tested this approach on three fish species for which empirical length-at-age and maturity data were available (from Hawaii and Guam) and calculated probability distributions of spawning potential ratios (SPR) at different exploitation rates. The life history parameter and SPR probability distributions generated from our data-limited analytical approach compared well with those obtained from bootstrap analyses of the empirical life history data. This work provides a useful new tool that can greatly assist fishery stock assessment scientists and managers in data-poor situations, typical of most of the world’s fisheries.

Life history traits of the exploited limpet Patella candei (Mollusca: Patellogastropoda) of the north-eastern Atlantic

2011 ◽  
Vol 92 (6) ◽  
pp. 1379-1387 ◽  
Author(s):  
P. Henriques ◽  
R. Sousa ◽  
A.R. Pinto ◽  
J. Delgado ◽  
G. Faria ◽  
...  
Keyword(s):  
Life History ◽  
Mortality Rate ◽  
Sexual Maturity ◽  
Life History Traits ◽  
Growth Parameters ◽  
Total Mortality ◽  
Recruitment Pattern ◽  
Length Relationship ◽  
North Eastern ◽  
Exploitation Rate

Life history traits of Patella candei were studied for the first time, including weight versus length relationship, growth, age structure, sexual maturity, recruitment pattern, mortality rates and yield and biomass-per-recruit of an exploited population in Madeira Island, north-eastern Atlantic using monthly length–frequency data from January to December 1999. The growth pattern of P. candei showed positive allometric nature of growth (b > 3, P < 0.05). The estimated growth parameters showed an asymptotic length (L∞) and growth coefficient (K) estimated at 80.81 mm and K at 0.32 year−1 with a growth performance index (φ′) calculated as 3.32 based on the collected data. This species is moderately long-lived reaching up to 9.36 years and achieving sexual maturity at 36.7 mm of shell length. The recruitment pattern was continuous, displaying a major peak event per year, occurring in January (25.12%). The estimated total mortality rate (Z) was 1.79 year−1 while natural mortality rate (M) was 0.55 year−1 and fishing mortality rate (F) was 1.24 year−1. The probability of capture shows that the length at first capture (Lc) was 42.7 mm, the exploitation rate (E) 0.693 and the maximum allowable limit of exploitation (Emax) was 0.779 for the highest yield. The exploitation rate was less than the predicted Emax values, showing that the stock of P. candei was found to be under-exploited in the investigated area; however, its slow growth and long life make it extremely vulnerable to over-exploitation.

Comparative rates of growth of the Port Jackson shark throughout its southern Australian range

2012 ◽  
Vol 63 (8) ◽  
pp. 687 ◽  
Author(s):  
Christopher Izzo ◽  
Kate R. Rodda
Keyword(s):  
Life History ◽  
Growth Parameters ◽  
South Australia ◽  
Growth Curves ◽  
Von Bertalanffy ◽  
Life History Parameters ◽  
Growth Functions ◽  
Port Jackson ◽  
Rates Of Growth ◽  
Size At Birth

Port Jackson sharks are distributed throughout southern Australia, with evidence suggesting that potential subpopulations exist. If subpopulations are evident, then phenotypic variation among groups should result in differences in life-history parameters. The present study tested for patterns of spatial variability of life-history parameters among regional Port Jackson shark populations. Rates of growth from Port Jackson sharks caught in the gulf waters of South Australia were calculated on the basis of counts of vertebral increments. Growth parameters were obtained by fitting the length-at-age data to von Bertalanffy and Gompertz growth functions. While the derived growth curves fit the length-at-age data well (r2 ranged from 0.87 to 0.91), parameters showed considerable differences between the two functions, with the von Bertalanffy function providing the more realistic estimates of growth (combined sexes: k = 0.081 year–1, L∞ = 1232 mm total length and t0 = –1.937 years). Life-history parameters for South Australian Port Jackson sharks were collated with the available data for the species, facilitating comparisons among regional populations. Growth curves among populations varied significantly; however, considerable overlap in the length ranges of size at birth and sizes at maturity among populations were evident. Overall, the data presented here do not provide definitive support for the presence of subpopulations across the distribution of the Port Jackson shark, suggesting that molecular analysis maybe required to directly test for structuring.

Population ecology, life history and diet of the shorthead drum Larimus breviceps in a tropical bight in southeastern Brazil

2013 ◽  
Vol 94 (3) ◽  
pp. 615-622 ◽  
Author(s):  
Eduardo Bessa ◽  
Flávia Borges Santos ◽  
Maíra Pombo ◽  
Márcia Denadai ◽  
Mariana Fonseca ◽  
...  
Keyword(s):  
Life History ◽  
Population Biology ◽  
Total Mortality ◽  
Sampling Period ◽  
Abundant Species ◽  
Southeastern Brazil ◽  
Older Individuals ◽  
Life History Parameters ◽  
Mortality Index ◽  
Random Samples

The population biology, life history parameters and diet of the shorthead drum Larimus breviceps were assessed in Caraguatatuba Bight, a shallow non-estuarine environment. Two homogeneous areas, South and North, were selected, avoiding major sources of continental waters. Monthly from October 2003 to October 2004, three random samples were taken by trawling from 800 to 1600 m outward from the waterline. Larimus breviceps was the third most abundant species during the study period, and was considerably more abundant from February to May 2004. Smaller individuals were also more abundant during this period, which we therefore considered the main recruitment period of the species. The predominance of individuals of a limited size range (6–12 cm total length) seems to indicate that the area functions as a nursery for L. breviceps, sheltering late-juvenile individuals. This feature complicated the estimation of life history parameters, but by taking into account the peculiarities of the area and the identification of similar modal progressions during the sampling period, we obtained reasonable values for the parameterization of the von Bertalanffy Growth Model (L∞ = 32.25 cm, K = 0.72, tmax 4.38 y, Z = 12.104). The total mortality index does not reflect mortality rates only, but also the migration of older individuals to other, probably deeper, areas. The diet was based mainly on Crustacea, specifically Decapoda shrimps, with slight seasonal alterations.

Life history characteristics of the silky shark Carcharhinus falciformis from the central west Pacific

2018 ◽  
Vol 69 (4) ◽  
pp. 562 ◽  
Author(s):  
Michael I. Grant ◽  
Jonathan J. Smart ◽  
William T. White ◽  
Andrew Chin ◽  
Leontine Baje ◽  
...  
Keyword(s):  
Life History ◽  
Growth Parameters ◽  
Growth Models ◽  
Significant Risk ◽  
Growth Parameter ◽  
Parameter Estimates ◽  
West Pacific ◽  
Average Litter Size ◽  
Silky Shark ◽  
Carcharhinus Falciformis

In the central west Pacific region, silky sharks (Carcharhinus falciformis) are commonly taken in fisheries, forming up to 95% of incidental elasmobranch bycatch. The present study examined the life history of silky sharks (n=553) from Papua New Guinean waters. Age was analysed using sectioned vertebrae, and a multimodel approach was applied to the length-at-age data to fit growth models. Females ranged in length from 65.0- to 253.0-cm total length (TL), with the oldest estimated at 28 years. Males ranged in length from 68.4 to 271.3cm TL and were aged to a maximum of 23 years. The logistic model provided the best fitting growth parameter estimates of length at birth L0=82.7cm TL, growth coefficient g=0.14year–1 and asymptotic length L∞=261.3cm TL for the sexes combined. Females reached sexual maturity at 204cm TL and 14.0 years, whereas males reached maturity at 183cm TL and 11.6 years. The average litter size from 28 pregnant females was 8 (range of 3–13). The growth parameters and late ages of sexual maturation for silky sharks in the central west Pacific suggest a significant risk from fisheries exploitation without careful population management.

scholarly journals Natural mortality estimation using tree-based ensemble learning models

2020 ◽  
Vol 77 (4) ◽  
pp. 1414-1426 ◽  
Author(s):  
Chanjuan Liu ◽  
Shijie Zhou ◽  
You-Gan Wang ◽  
Zhihua Hu
Keyword(s):  
Life History ◽  
Ensemble Learning ◽  
Random Forests ◽  
Growth Parameters ◽  
Training Dataset ◽  
Natural Mortality ◽  
Statistical Regression ◽  
Learning Models ◽  
Empirical Methods ◽  
Life History Parameters

Abstract Empirical studies are popular in estimating fish natural mortality rate (M). However, these empirical methods derive M from other life-history parameters and are often perceived as being less reliable than direct methods. To improve the predictive performance and reliability of empirical methods, we develop ensemble learning models, including bagging trees, random forests, and boosting trees, to predict M based on a dataset of 256 records of both Chondrichthyes and Osteichthyes. Three common life-history parameters are used as predictors: the maximum age and two growth parameters (growth coefficient and asymptotic length). In addition, taxonomic variable class is included to distinguish Chondrichthyes and Osteichthyes. Results indicate that tree-based ensemble learning models significantly improve the accuracy of M estimate, compared to the traditional statistical regression models and the basic regression tree model. Among ensemble learning models, boosting trees and random forests perform best on the training dataset, but the former performs a slightly better on the test dataset. We develop four boosting trees models for estimating M based on varying life-history parameters, and an R package is provided for interested readers to estimate M of their new species.

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