The daily egg production method: A valid tool for application to European hake in the Bay of Biscay?

2010 ◽  
Vol 104 (1-3) ◽  
pp. 100-110 ◽  
Author(s):  
H. Murua ◽  
L. Ibaibarriaga ◽  
P. Álvarez ◽  
M. Santos ◽  
M. Korta ◽  
...  
Keyword(s):  
Egg Production ◽  
Production Method ◽  
Bay Of Biscay ◽  
European Hake

scholarly journals Assessing natural mortality of Bay of Biscay anchovy from survey population and biomass estimates

2016 ◽  
Vol 73 (2) ◽  
pp. 216-234 ◽  
Author(s):  
Andrés Uriarte ◽  
Leire Ibaibarriaga ◽  
Lionel Pawlowski ◽  
Jacques Massé ◽  
Pierre Petitgas ◽  
...  
Keyword(s):  
Egg Production ◽  
Linear Models ◽  
Production Method ◽  
Natural Mortality ◽  
Bay Of Biscay ◽  
Stock Assessments ◽  
Long Time ◽  
Using Data ◽  
Log Linear ◽  
Firm Evidence

The closure of the anchovy (Engraulis encrasicolus) fishery in the Bay of Biscay between 2005 and 2010 because of low biomass levels provided an opportunity to estimate natural mortality using data from egg (daily egg production method, DEPM) and acoustic surveys implemented for the assessment of this population since 1987. Assuming that natural mortality (M) is constant over time and that catchability in both surveys is equal for all ages, M could be estimated using log-linear models on the series of surveys of population numbers at age and seasonal integrated stock assessments. The analysis suggests M values of around 0.9 for a common natural mortality at all ages. However, we found firm evidence that natural mortality at ages 2 and older (M2+) is markedly higher than at age 1 (M1), which indicates senescent mortality, a possibility suggested a long time ago for this type of short-lived species.

scholarly journals Daily egg production of anchovy in European waters

2004 ◽  
Vol 61 (6) ◽  
pp. 944-958 ◽  
Author(s):  
Stylianos Somarakis ◽  
Isabel Palomera ◽  
Alberto Garcia ◽  
Luis Quintanilla ◽  
Constantin Koutsikopoulos ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Egg Production ◽  
Stock Assessment ◽  
Production Method ◽  
Bay Of Biscay ◽  
Spawning Habitat ◽  
Independent Information ◽  
Stock Biomass ◽  
Spawning Stock ◽  
The Mediterranean

Abstract Since the late 1980s, the Daily Egg Production Method (DEPM) has been applied to several anchovy stocks in European waters. DEPM surveys in the Bay of Biscay were well standardized and focused on providing fisheries-independent information for stock assessment purposes. Those targeting Mediterranean stocks were largely experimental and often opportunistic, with the main aim of developing and testing the method, rather than providing estimates of spawning stock biomass (SSB) for stock assessment. Consequently, the DEPM has been applied once, twice, or a maximum of three times in certain Mediterranean areas with no among-area standardization. Different techniques for several aspects of the method have been used in the Mediterranean, and the parameters estimated vary greatly among stocks and year of application. Evidence is provided that variability in biological production among sub-basins and/or years, a characteristic of Mediterranean Sea, may directly affect anchovy egg production. The daily specific fecundity of anchovy stocks can vary greatly among years, areas, or seasons in response to changing environmental and trophic regimes. When the correlation between regression-derived estimates of daily egg production and associated estimates of daily specific fecundity for anchovy in the Mediterranean, the Bay of Biscay, and upwelling areas are compared, a significant isometric relationship emerges for the Mediterranean and the Bay of Biscay, implying density-dependent use of spawning habitat. In upwelling areas, estimates of daily egg production are relatively high for a narrow range of generally low daily specific fecundities. There is a strong linear relationship between anchovy SSB and spawning area in European waters that does not differ significantly between the Bay of Biscay and the Mediterranean Sea.

Spatiotemporal modelling for the annual egg production method of stock assessment using generalized additive models

1998 ◽  
Vol 55 (12) ◽  
pp. 2608-2621 ◽  
Author(s):  
N H Augustin ◽  
D L Borchers ◽  
E D Clarke ◽  
S T Buckland ◽  
M Walsh
Keyword(s):  
Environmental Variables ◽  
Egg Production ◽  
Survey Design ◽  
Stock Assessment ◽  
Generalized Additive Models ◽  
Production Method ◽  
Additive Models ◽  
Atlantic Mackerel ◽  
Egg Density ◽  
Survey Designs

Generalized additive models (GAMs) are used to model the spatiotemporal distribution of egg density as a function of locational and environmental variables. The main aim of using GAMs is to improve precision of egg abundance estimates needed for the annual egg production method. The application of GAMs requires a survey design with good coverage in space and time. If the only results available are from less optimal survey designs, they can be improved by using historical data for spawning boundaries. The method is applied to plankton egg survey data of Atlantic mackerel (Scomber scombrus) in 1995. The GAM-based method improves the precision of estimates substantially and is also useful in explaining complex space-time trends using environmental variables.

scholarly journals DEVELOPMENT STAGE, AGEING AND NATURAL MORTALITY OF ANCHOVY EGGS (Encrasicholina SPECIES) FROM BACAN

2017 ◽  
Vol 4 (2) ◽  
pp. 52
Author(s):  
Retno Andamari ◽  
Andriko N. Susanto ◽  
David A. Milton
Keyword(s):  
Egg Production ◽  
Production Method ◽  
Development Stage ◽  
Large Series ◽  
Natural Mortality

ln order to study the possible application of the Daily Egg Production Method (DEPM) for estimating anchovy (Encrasicholina spp.) biomass at Bacan. Maluku, we collected a large series of plankton samples.

Variability in total egg production and implications for management of the southern stock of European hake

2010 ◽  
Vol 104 (1-3) ◽  
pp. 111-122 ◽  
Author(s):  
Sonia Mehault ◽  
Rosario Domínguez-Petit ◽  
Santiago Cerviño ◽  
Fran Saborido-Rey
Keyword(s):  
Egg Production ◽  
European Hake

scholarly journals Evidence of underestimation of European hake growth in the Bay of Biscay, and its relationship with bias in the agreed method of age estimation

2006 ◽  
Vol 63 (9) ◽  
pp. 1674-1681 ◽  
Author(s):  
Hélène de Pontual ◽  
Anne Laure Groison ◽  
Carmen Piñeiro ◽  
Michel Bertignac
Keyword(s):  
Age Estimation ◽  
Good Condition ◽  
Estimation Method ◽  
Somatic Growth ◽  
Biological Knowledge ◽  
Data Sets ◽  
Bay Of Biscay ◽  
Age Validation ◽  
Management Advice ◽  
European Hake

Abstract In 2002, a pilot experiment on hake tagging was carried out using methodology specifically developed to catch and handle fish in good condition. By the end of 2005, 36 hake and five tags had been returned to the laboratory (a 3.1% return rate) with a maximum time at liberty of 1066 days. The somatic growth of the recoveries proved to be twofold higher than that expected from published von Bertalanffy growth functions for the species in the Bay of Biscay. The growth underestimation was related to age overestimation, as demonstrated by two independent analyses. The first was based on a blind interpretation of marked otoliths conducted independently by two European experts involved in the routine age estimation of hake. The result shows that the age estimates were neither accurate (inconsistent with oxytetracycline mark positions) nor precise. The second approach compared the predicted otolith growth with the observed growth, and the discrepancy between the two data sets was large. Both types of analyses invalidate the internationally agreed age estimation method and demonstrate a need for further research. Although based on limited data, the study highlights the need to improve biological knowledge of the species in order to improve assessment and management advice. It also strengthens the argument for age validation.

scholarly journals Species- and size-related patterns in stable isotopes and mercury concentrations in fish help refine marine ecosystem indicators and provide evidence for distinct management units for hake in the Northeast Atlantic

2014 ◽  
Vol 71 (5) ◽  
pp. 1073-1087 ◽  
Author(s):  
T. Chouvelon ◽  
F. Caurant ◽  
Y. Cherel ◽  
B. Simon-Bouhet ◽  
J. Spitz ◽  
...  
Keyword(s):  
Fish Species ◽  
Trophic Level ◽  
Trophic Ecology ◽  
Marine Ecosystem ◽  
Feeding Strategies ◽  
Bay Of Biscay ◽  
Management Units ◽  
Δ13c And Δ15n ◽  
Northeast Atlantic ◽  
European Hake

Abstract Recent European environmental policies argue for the development of indicators of the ecological status of ecosystems that are easy to implement and powerful enough to detect changes quickly. For instance, some indicators that are currently proposed for monitoring foodweb structure and functioning are based on the size of organisms, using size as a proxy for trophic level. However, these indicators do not necessarily accurately reflect the underlying trophic structure and dynamics to follow. Ecological tracers (i.e. chemical parameters measured in consumer tissues to infer the trophic ecology of organisms) may serve as complementary indicators of trophic level, and may also help distinguish different populations of a species when more commonly used methods (e.g. genetic, age determination) present their own limitations. Here, we analysed the potential of muscle δ13C and δ15N values and of muscle mercury (Hg) concentrations to depict size-related trophic habits of different fish species. We expected that intra- and interspecific variation in these ecological tracers could be helpful in refining currently proposed indicators of marine ecosystems, and also help in discriminating management unitsfor some species. Four fish species were selected for their economical and/or ecological importance in the Bay of Biscay (Northeast Atlantic): whiting Merlangius merlangus, European hake Merluccius merluccius, Atlantic horse mackerel Trachurus trachurus and anglerfish Lophius piscatorius. Muscle δ13C and δ15N values segregated the species and enabled us to discriminate species-specific feeding strategies with increasing size of individuals. Fish body size was not always linearly correlated with δ15N or trophic level. In contrast, Hg concentrations and size-related Hg patterns were more similar from species to species. Interestingly, muscle δ15N values together with Hg concentrations segregated the two putative stocks of European hake within the Bay of Biscay. Hence, we propose the combined use of ecological tracers as a promising method for accurately assigning a consumer to a trophic guild, investigating Hg trophodynamics in foodwebs, and helping discriminate distinct ecological populations within a species when defining management units.

Improving the precision of the daily egg production method using generalized additive models

1997 ◽  
Vol 54 (12) ◽  
pp. 2727-2742 ◽  
Author(s):  
D L Borchers ◽  
S T Buckland ◽  
I G Priede ◽  
S Ahmadi
Keyword(s):  
Egg Production ◽  
Survey Methods ◽  
Functional Dependence ◽  
Generalized Additive Models ◽  
Substantial Reduction ◽  
Large Degree ◽  
Production Method ◽  
Additive Models ◽  
Sample Survey ◽  
Stochastic Variation

Generalized additive models (GAMs) are used to model spatial variation in egg density and increase the precision of biomass estimates from the daily egg production method. Application of GAMs to survey data from the western mackerel (Scomber scombrus) and horse mackerel (Trachurus trachurus) stocks result in a substantial reduction in coefficients of variation of egg abundance. In developing GAM methods for the daily egg production method, we generalize Pennington's method, in which presence-absence is modelled separately from nonzero observations, and use a new form of the bootstrap that accommodates clustered count data without requiring explicit modelling of the form of clustering. In addition to increasing estimation precision, the use of GAMs has several advantages over stratified sample survey methods. To a large degree they allow the data to determine the form of functional dependence of the response on explanatory variables; they accommodate a wide variety of forms of stochastic variation of the response; they provide maps of the predicted density within the survey area; they provide an objective means of interpolating into unsampled areas; and estimation does not assume random sampling with respect to location.

A reanalysis of North Sea plaice spawning-stock biomass using the annual egg production method

2009 ◽  
Vol 66 (9) ◽  
pp. 1999-2011 ◽  
Author(s):  
Cindy J. G. van Damme ◽  
Loes J. Bolle ◽  
Clive J. Fox ◽  
Petter Fossum ◽  
Gerd Kraus ◽  
...  
Keyword(s):  
North Sea ◽  
Egg Production ◽  
Stock Assessment ◽  
Population Analysis ◽  
Spatial Dynamics ◽  
Production Method ◽  
Southern Bight ◽  
The North ◽  
Stock Biomass ◽  
Spawning Stock

Abstract van Damme, C. J. G., Bolle, L. J., Fox, C. J., Fossum, P., Kraus, G., Munk, P., Rohlf, N., Witthames, P. R., and Dickey-Collas, M. 2009. A reanalysis of North Sea plaice spawning-stock biomass using the annual egg production method. – ICES Journal of Marine Science, 66: 1999–2011. Uncertainty about the quality of current virtual population analysis-based stock assessment for North Sea plaice (Pleuronectes platessa) has led to various abundance indices. We compared biomass estimates from the annual egg production (AEP) method with current stock assessments based on catch-at-age to validate the current and historical perception of exploitation. The AEP method was also used to investigate the dynamics of the spatial components of plaice in the North Sea. We corrected for fecundity down-regulation and changes in sex ratio. Estimates from both methods were similar in trend and absolute biomass. On the Dogger Bank, there was a dramatic decline in biomass from 1948 and 1950 to 2004, and in the Southern Bight, the stock appeared to increase from 1987 and 1988 to 2004, although not reaching the historically high levels of 1948 or 1950. The timing of spawning of North Sea plaice does not appear to have changed throughout the period of high exploitation. We conclude that the AEP method is a useful way to hindcast the spatial dynamics of heavily exploited flatfish stocks.

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