scholarly journals Growth, mortality and spawning stock biomass of the striped red mullet Mullus surmuletus, in the Egyptian Mediterranean waters

2009 ◽  
Vol 10 (2) ◽  
pp. 5 ◽  
Author(s):  
S.F. MEHANNA
Keyword(s):  
Growth Parameters ◽  
Growth Parameter ◽  
Reference Points ◽  
Age And Growth ◽  
Parameter Estimates ◽  
Red Mullet ◽  
Stock Biomass ◽  
Reading Technique ◽  
Spawning Stock ◽  
Mullus Surmuletus

Population parameters such as age, growth, mortality and maturity-at-age are crucial parameters for accurate stock assessment and management plans to ensure the sustainable development of fisheries. Also, they are essential for the calculation of spawning stock biomass (SSB) and equilibrium yield as well as biological reference points including Fmax, F0.1 and F30%SSB. Age and growth parameters were estimated for the striped red mullet, Mullus surmuletus, sampled from commercial landings of the trawl fishery in the Egyptian Mediterranean waters, using the otolith reading technique. M. surmuletus has a longevity of 5 years, but over 70% of fish were less than 2 years old. The growth parameter estimates were K= 0.47 yrs-1, L∞= 31.74 cm, and to= -0.3 yrs. Natural mortality (M) was 0.43 yrs-1, fishing mortality (F) was 0.73 yrs-1, survival rate (S) was 0.31 and exploitation ratio was 0.63 yr-1. Length-at-50% maturity was estimated at 15.1 cm TL, while the length at first capture was estimated at 11.6 cm TL. SSB analysis showed that effort reduction is strongly recommended such that F be reduced by 40% to rebuild spawner biomass to acceptable levels. Per-recruit analysis revealed that F should be reduced by about 27% to achieve the maximum Y/R. All approaches point to the need for drastic reduction in fishing pressure by about 30-40% in the Egyptian Mediterranean fisheries.

scholarly journals Consequences of bias in age estimation on assessment of the northern stock of European hake (Merluccius merluccius) and on management advice

2007 ◽  
Vol 64 (5) ◽  
pp. 981-988 ◽  
Author(s):  
Michel Bertignac ◽  
Hélène de Pontual
Keyword(s):  
Age Estimation ◽  
Growth Parameters ◽  
Reference Points ◽  
Fishing Mortality ◽  
Merluccius Merluccius ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Management Advice ◽  
The Impact ◽  
European Hake

Abstract Bertignac, M., and de Pontual, H. 2007. Consequences of bias in age estimation on assessment of the northern stock of European hake (Merluccius merluccius) and on management advice. – ICES Journal of Marine Science, 64: 981–988. The results of a pilot tagging study on hake (Merluccius merluccius), conducted in the northern part of the Bay of Biscay in 2002, indicate that growth rates for this stock may be currently underestimated because of biased estimates of age. The impact that such a bias may have on the stock dynamics and the trends of the key population parameters, recruitment, spawning-stock biomass (SSB), and mortality are investigated. Assuming new growth parameters, a new age–length key is derived and used to produce and catch-at-age data and abundance indices, which are then used to assess the stock. Bias in estimating age affects the absolute levels of fishing mortality and stock biomass estimates, and also impacts the trend in SSB. However, trends in fishing mortality and recruitment are comparable, and the stock status with respect to precautionary reference points is broadly the same. As expected, the simulation also shows that the stock may be more reactive to changes in fishing levels, which affect medium-term forecasts. Long-term sustainable yields may also be impacted.

scholarly journals A two-stage biomass model to assess the English Channel cuttlefish (Sepia officinalis L.) stock

2014 ◽  
Vol 71 (9) ◽  
pp. 2457-2468 ◽  
Author(s):  
Michaël Gras ◽  
Beatriz A. Roel ◽  
Franck Coppin ◽  
Eric Foucher ◽  
Jean-Paul Robin
Keyword(s):  
Reference Points ◽  
Sea Surface ◽  
Sepia Officinalis ◽  
Sustainable Utilization ◽  
English Channel ◽  
Two Stage ◽  
Stock Biomass ◽  
Exploitation Rate ◽  
Spawning Stock ◽  
Age Structured

Abstract The English Channel cuttlefish (Sepia officinalis) is the most abundant cephalopod resource in the Northeast Atlantic and one of the three most valuable resources for English Channel fishers. Depletion methods and age-structured models have been used to assess the stock, though they have shown limitations related to the model assumptions and data demand. A two-stage biomass model is, therefore, proposed here using, as input data, four abundance indices derived from survey and commercial trawl data collected by Ifremer and Cefas. The model suggests great interannual variability in abundance during the 17 years of the period considered and a decreasing trend in recent years. Model results suggest that recruitment strength is independent of spawning–stock biomass, but appears to be influenced by environmental conditions such as sea surface temperature at the start of the life cycle. Trends in exploitation rate do not reveal evidence of overexploitation. Reference points are proposed and suggestions for management of the sustainable utilization of cuttlefish in the English Channel are advanced.

A state-space approach to incorporating environmental effects on recruitment in an age-structured assessment model with an application to southern New England yellowtail flounder

2016 ◽  
Vol 73 (8) ◽  
pp. 1261-1270 ◽  
Author(s):  
Timothy J. Miller ◽  
Jonathan A. Hare ◽  
Larry A. Alade
Keyword(s):  
New England ◽  
State Space ◽  
Reference Points ◽  
Assessment Model ◽  
Cold Pool ◽  
Model Framework ◽  
Yellowtail Flounder ◽  
Southern New England ◽  
Stock Biomass ◽  
Spawning Stock

The state-space model framework provides a natural, probabilistic approach to stock assessment by modeling the stochastic nature of population survival and recruitment separately from sampling uncertainty inherent in observations on the population. We propose a state-space assessment model that is expanded to simultaneously treat environmental covariates as stochastic processes and estimate their effects on recruitment. We apply the model to southern New England yellowtail flounder (Limanda ferruginea) using data from the most recent benchmark assessment to evaluate evidence for effects of the mid-Atlantic cold pool and spawning stock biomass on recruitment. Based on Akaike’s information criterion, both the cold pool and spawning stock biomass were important predictors of recruitment and led to annual variation in estimated biomass reference points and associated yield. We also demonstrate the effect of the stochasticity of the mid-Atlantic cold pool on short-term forecasts of the stock size, biomass reference point, and stock status.

scholarly journals Growth Parameters and Spawning Season Estimation of Four Important Flyingfishes in the Kuroshio Current Off Taiwan and Implications From Comparisons With Global Studies

2022 ◽  
Vol 8 ◽  
Author(s):  
Shui-Kai Chang ◽  
Tzu-Lun Yuan ◽  
Simon D. Hoyle ◽  
Jessica H. Farley ◽  
Jen-Chieh Shiao
Keyword(s):  
Growth Parameters ◽  
Growth Models ◽  
Growth Parameter ◽  
Optimal Growth ◽  
Kuroshio Current ◽  
Parameter Estimates ◽  
Special Importance ◽  
Von Bertalanffy ◽  
Multiple Model ◽  
The Kuroshio

Growth shapes the life history of fishes. Establishing appropriate aging procedures and selecting representative growth models are important steps in developing stock assessments. Flyingfishes (Exocoetidae) have ecological, economic, and cultural importance to many coastal countries including Taiwan. There are 29 species of flyingfishes found in the Kuroshio Current off Taiwan and adjacent waters, comprising 56% of the flyingfishes taxa recorded worldwide. Among the six dominant species in Taiwan, four are of special importance. This study reviews aging data of these four species, documents major points of the aging methods to address three aging issues identified in the literature, and applies multi-model inference to estimate sex-combined and sex-specific growth parameters for each species. The candidate growth models examined included von Bertalanffy, Gompertz, Logistic, and Richards models, and the resulting optimal model tended to be the von Bertalanffy model for sex-combined data and Gompertz and von Bertalanffy models for sex-specific cases. The study also estimates hatch dates from size data collected from 2008 to 2017; the results suggest that the four flyingfishes have two spawning seasons per year. Length-weight relationships are also estimated for each species. Finally, the study combines the optimal growth estimates from this study with estimates for all flyingfishes published globally, and statistically classifies the estimates into clusters by hierarchical clustering analysis of logged growth parameters. The results demonstrate that aging materials substantially affect growth parameter estimates. This is the first study to estimate growth parameters of flyingfishes with multiple model consideration. This study provides advice for aging flyingfishes based on the three aging issues and the classification analysis, including a recommendation of using the asterisci for aging flyingfishes to avoid complex otolith processing procedures, which could help researchers from coastal countries to obtain accurate growth parameters for many flyingfishes.

Black Bass Diversity: Multidisciplinary Science for Conservation

2015 ◽  
Keyword(s):  
Growth Rates ◽  
Growth Parameter ◽  
Population Characteristics ◽  
Age And Growth ◽  
Minimum Length ◽  
Parameter Estimates ◽  
Black Bass ◽  
Annual Total ◽  
The Mean ◽  
Flint River

<em>Abstract</em>.—The largest native population of Shoal Bass <em>Micropterus cataractae</em> inhabits the Flint River, Georgia and remains relatively unstudied. We examined demographic characteristics of the population in the lower Flint River that is bounded by reservoirs during 2009–2011. We anchor tagged 741 Shoal Bass to evaluate the percentage of caught fish that were harvested. Shoal bass (<em>n</em> = 187) were sacrificed for age and growth analysis. Ages of sampled fish ranged from age 1 to 11. Von Bertalanffy growth parameter estimates were <EM>L</EM><sub>∞</sub> = 564 mm, <EM>K</EM> = 0.312, and<em> t</em><sub>0</sub> = –0.089. Male and female growth rates were similar, with the mean Shoal Bass requiring 2.4 years to reach 305 mm and 5.1 years to reach 457 mm. Growth rates of Shoal Bass were greater than those of previously studied populations and Largemouth Bass <em>M. salmoides</em> in the Flint River and an impoundment bounding the upper end of the study site. Annual total pooled mortality was 49%. Forty-one percent of caught Shoal Bass were harvested by anglers (range 31–60%). Our results suggest that with current population characteristics, an increase in the minimum length limit would not increase yield to the recreational fishery.

scholarly journals Linking the performance of a data-limited empirical catch rule to life-history traits

2020 ◽  
Vol 77 (5) ◽  
pp. 1914-1926
Author(s):  
Simon H Fischer ◽  
José A A De Oliveira ◽  
Laurence T Kell
Keyword(s):  
Time Series ◽  
Life History ◽  
Life Histories ◽  
Life History Traits ◽  
Growth Parameter ◽  
Reference Points ◽  
Total Allowable Catch ◽  
Fish Stocks ◽  
Wide Range ◽  
Spawning Stock

Abstract Worldwide, the majorities of fish stocks are data-limited and lack fully quantitative stock assessments. Within ICES, such data-limited stocks are currently managed by setting total allowable catch without the use of target reference points. To ensure that such advice is precautionary, we used management strategy evaluation to evaluate an empirical rule that bases catch advice on recent catches, information from a biomass survey index, catch length frequencies, and MSY reference point proxies. Twenty-nine fish stocks were simulated covering a wide range of life histories. The performance of the rule varied substantially between stocks, and the risk of breaching limit reference points was inversely correlated to the von Bertalanffy growth parameter k. Stocks with k&gt;0.32 year−1 had a high probability of stock collapse. A time series cluster analysis revealed four types of dynamics, i.e. groups with similar terminal spawning stock biomass (collapsed, BMSY, 2BMSY, 3BMSY). It was shown that a single generic catch rule cannot be applied across all life histories, and management should instead be linked to life-history traits, and in particular, the nature of the time series of stock metrics. The lessons learnt can help future work to shape scientific research into data-limited fisheries management and to ensure that fisheries are MSY compliant and precautionary.

scholarly journals An alternative reference point in the context of ecosystem-based fisheries management: maximum sustainable dead biomass

2015 ◽  
Vol 72 (8) ◽  
pp. 2257-2268 ◽  
Author(s):  
Hans-Joachim Rätz ◽  
John Casey ◽  
Steven J. Holmes ◽  
Josep Lloret ◽  
Hendrik Dörner ◽  
...  
Keyword(s):  
Fisheries Management ◽  
Reference Points ◽  
Production Model ◽  
Fish Stock ◽  
Compensatory Mechanism ◽  
Fishing Mortality ◽  
Dead Biomass ◽  
Selection Pattern ◽  
Stock Biomass ◽  
Spawning Stock

Abstract Under the 2013 Reform of the European Union's Common Fisheries Policy (CFP), fisheries management aims to ensure that, within a reasonable time frame, the exploitation of marine biological resources restores and maintains populations of harvested stocks above levels that can produce the maximum sustainable yield (MSY). The CFP also calls for the implementation of an ecosystem-based approach to fisheries management (EBFM). In this paper, we present the concept of maximum sustainable dead biomass (MSDB) and its associated management reference points for fishing mortality and spawning-stock biomass as alternatives to those associated with MSY. The concept of MSDB is illustrated by a dynamic pool production model of a virtual fish stock which takes into account variations in natural mortality (M), fishing mortality (F), and exploitation pattern. Our approach implies a compensatory mechanism whereby survivors may benefit from compensatory density dependence and is implemented through progressive substitution of M with F for varying rates of total mortality (Z). We demonstrate that the reference points for fishing mortality and spawning-stock biomass associated with MSDB are less sensitive to increasing compensation of M with F than those associated with MSY and more sensitive to changes in selection pattern. MSDB-based reference points, which are consistent with maximum stock productivity, are also associated with lower fishing mortality rates and higher stock biomasses than their MSY-based counterparts. Given that selection pattern can be influenced through fishery input measures (e.g. technical gear measures, decisions on areas, and/or times of fishing), whereas variations of M in response to F are not controllable (indeed poorly understood), that the results of many fish stock assessments are imprecise, that maximum stock productivity corresponds to MSDB and that MSY-based reference points may best be considered as limits, we propose that MSDB-based reference points provide a more appropriate basis for management under an EBFM.

scholarly journals Rapid growth of wahoo (Acanthocybium solandri) in the Coral Sea, based on length-at-age estimates using annual and daily increments on sagittal otoliths

2013 ◽  
Vol 70 (6) ◽  
pp. 1128-1139 ◽  
Author(s):  
Mitchell T. Zischke ◽  
Shane P. Griffiths ◽  
Ian R. Tibbetts
Keyword(s):  
Rapid Growth ◽  
Growth Parameter ◽  
Age And Growth ◽  
Parameter Estimates ◽  
Annual Increment ◽  
Important Species ◽  
Daily Increments ◽  
Growth Increments ◽  
Coral Sea ◽  
Age Estimates

Abstract Zischke, M. T., Griffiths, S. P., and Tibbetts, I. R. 2013. Rapid growth of wahoo (Acanthocybium solandri) in the Coral Sea, based on length-at-age estimates using annual and daily increments on sagittal otoliths. – ICES Journal of Marine Science, 70: 1128–1139. The wahoo (Acanthocybium solandri) is an economically important species incidentally caught in oceanic fisheries targeting tuna and coastal fisheries targeting mackerels. The age and growth of wahoo was examined using whole and sectioned otoliths from 395 fish (790–1770 mm LF) sampled from the Coral Sea. Growth increments were more reliably assigned on whole otoliths than sectioned otoliths. Edge analyses revealed that growth increments were deposited annually, primarily between October and February. Furthermore, analysis of presumed daily microincrements showed that ∼90% of fish had deposited the first “annual” growth increment by the 365th day, thereby indirectly validating annual increment formation. Wahoo were aged at between 108 d and 7 years, with 76% of fish being <2-year old. The specialized von Bertalanffy growth function provided the best fit to length-at-age data, with parameter estimates (sexes combined) of L∞ = 1499 mm LF, K = 1.58 year−1, and t0 = −0.17 years. The growth performance index for wahoo in the Coral Sea (φ′ = 4.55) was one of the highest of all pelagic fish, with their growth and maximum size most similar to dolphinfish. This study suggests that wahoo are one of the fastest growing teleosts and provides growth parameter estimates that may facilitate future stock assessments and guide fisheries management.

scholarly journals Interactions between ageing error and selectivity in statistical catch-at-age models: simulations and implications for assessment of the Chilean Patagonian toothfish fishery

2016 ◽  
Vol 73 (4) ◽  
pp. 1074-1090 ◽  
Author(s):  
Vania Henríquez ◽  
Roberto Licandeo ◽  
Luis A. Cubillos ◽  
Sean P. Cox
Keyword(s):  
Reference Points ◽  
Parameter Estimates ◽  
Model Parameters ◽  
Time Varying ◽  
Age Composition ◽  
Composition Data ◽  
Spawning Stock ◽  
Patagonian Toothfish ◽  
Stock Depletion ◽  
Age Structured

Abstract In age-structured fisheries stock assessments, ageing errors within age composition data can lead to biased mortality rate and year-class strength estimates. These errors may be further compounded where fishery-dependent age composition data are influenced by temporal changes in fishery selectivity and selectivity misspecification. In this study, we investigated how ageing error within age composition data interacts with time-varying fishery selectivity and selectivity misspecification to affect estimates derived from a statistical catch-at-age (SCA) model that used fishery-dependent data. We tested three key model parameters: average unfished recruitment (R0), spawning stock depletion (Dfinal), and fishing mortality in the terminal year (Fterminal). The Patagonian toothfish (Dissostichus eleginoides) fishery in southern Chile was used as a case study. Age composition data used to assess this fishery were split into two sets based on scale (1989–2006) and otolith (2007–2012) readings, where the scale readings show clear age-truncation effects. We used a simulation-estimation approach to examine the bias and precision of parameter estimates under various combinations of ageing error, selectivity type (asymptotic or dome-shaped), selectivity misspecification, and variation in selectivity over time. Generally, ageing error led to overly optimistic perceptions of current fishery status relative to historical reference points. Ageing error generated imprecise and positively biased estimates of R0 (range 10 to &gt;200%), Dfinal (range −20 to &gt;100%), and Fterminal (range −15 to &gt;150%). The bias in Dfinal and R0 was more severe when selectivity was dome-shaped. Time-varying selectivity (both asymptotic and dome-shaped) increased the bias in Dfinal and Fterminal, but decreased the bias in R0. The effect of ageing error was more severe, or was masked, with selectivity misspecification. Correcting the ageing error inside the SCA reduced bias and improved precision of estimated parameters .

scholarly journals 690Growth in childhood and age at menarche: Insights from individual trajectory modelling

2021 ◽  
Vol 50 (Supplement_1) ◽  
Author(s):  
Lynne Giles ◽  
Melissa Whitrow ◽  
Alice Rumbold ◽  
Michael Davies ◽  
Vivienne Moore
Keyword(s):  
Random Effects ◽  
Growth Parameters ◽  
Growth Parameter ◽  
Hazard Ratio ◽  
Age At Menarche ◽  
Parameter Estimates ◽  
Early Puberty ◽  
Random Effects Models ◽  
Childhood Growth ◽  
Menstrual History

Abstract Background The relationship between patterns of weight gain across childhood and the onset of puberty remains unclear. We aimed to derive growth parameters (size, tempo, and velocity) from models of weight across childhood and to estimate their effects on age at menarche. Methods Serial height and weight measurements from birth to age 9.5 years for 557 children who took part in the Generation 1 cohort study were used, along with girls’ menstrual history at age 12-13 years. Shape invariant random effects models were fit to log(weight+1) for all available participants’ data (282 girls, 260 boys), and AIC used to identify the best-fitting model. In time-to-event models subsequently fit to the girls’ data to estimate effects of the growth parameters on menarcheal age, a censoring age of 12 years was used to define early puberty. Results A model with 4df and fixed and random effects for size and tempo and a fixed effect for velocity was preferred. Some 19% of girls began menstruating before age 12 years. Size and tempo were each associated with an increased hazard of earlier menarche; a 0.1 unit gain in size was associated with a hazard ratio of 1.75 (95%CI 1.32–2.33), and a 0.1 unit gain in tempo with a hazard ratio of 7.84 (95%CI 3.41–18.05). Conclusions Using all participants’ data gave more precise growth parameter estimates. Key messages Understanding mechanisms that drive increased size and tempo of childhood growth may help to elucidate the links between obesity and girls’ risk of early puberty.

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