scholarly journals Estimates of batch fecundity and spawning fraction for the southern stock of horse mackerel (Trachurus trachurus) in ICES Division IXa

2009 ◽  
Vol 66 (4) ◽  
pp. 617-622 ◽  
Author(s):  
Patrícia Gonçalves ◽  
Ana Maria Costa ◽  
Alberto G. Murta
Keyword(s):  
Egg Production ◽  
Production Method ◽  
Horse Mackerel ◽  
Batch Fecundity ◽  
Trachurus Trachurus ◽  
Absolute Abundance ◽  
Female Total ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Ovulatory Follicles

Abstract Gonçalves, P., Costa, A. M., and Murta, A. G. 2009. Estimates of batch fecundity, and spawning fraction for the southern stock of horse mackerel (Trachurus trachurus) in ICES Division IXa. – ICES Journal of Marine Science, 66: 617–622. Since 1995 the annual egg production method has been applied triennially to the southern stock of horse mackerel (Trachurus trachurus) in the Northeast Atlantic (ICES Division IXa). This method assumes that fecundity is determinate, but increasing evidence indicates that horse mackerel are indeterminate spawners. The daily egg production method (DEPM) does not rely on the assumption of determinate fecundity, making it the appropriate method for this species. Therefore, we reanalysed samples collected from previous surveys (2002, 2004, 2005, and 2007) to obtain estimates for batch fecundity and spawning fraction, which are important DEPM parameters. The estimates of batch fecundity are around 200 oocytes g−1 of female (total ovary-free weight). Several criteria were used to estimate spawning fraction (migratory nucleus stage, hydrated oocytes, and post-ovulatory follicles) and all showed the same trend among years, varying between 0.10 and 0.30 d−1. The estimates were significantly different among methods, but those differences were similar across surveys, indicating that a consistent bias would be reflected in the final spawning-stock biomass (SSB) estimates obtained from the DEPM. Until further information is available regarding the accuracy of the criteria used to estimate spawning fraction, the southern horse mackerel SSB estimates from the DEPM should only be taken as indicative of trends rather than measures of absolute abundance.

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.

scholarly journals A linked separable–ADAPT VPA assessment model for western horse mackerel (Trachurus trachurus), accounting for realized fecundity as a function of fish weight

2010 ◽  
Vol 67 (5) ◽  
pp. 916-930 ◽  
Author(s):  
José A. A. De Oliveira ◽  
Chris D. Darby ◽  
Beatriz A. Roel
Keyword(s):  
Egg Production ◽  
Direct Conversion ◽  
Assessment Model ◽  
Horse Mackerel ◽  
Population Estimates ◽  
Trachurus Trachurus ◽  
Large Area ◽  
Potential Fecundity ◽  
Fish Weight ◽  
Spawning Stock

Abstract De Oliveira, J. A. A., Darby, C. D., and Roel, B. A. 2010. A linked separable–ADAPT VPA assessment model for western horse mackerel (Trachurus trachurus), accounting for realized fecundity as a function of fish weight. – ICES Journal of Marine Science, 67: 916–930. The western horse mackerel stock covers a large area of the Northeast Atlantic and is characterized by the sporadic occurrence of strong year classes. The only fishery-independent data available for its assessments are the estimates of total annual egg production from triennial egg surveys. Horse mackerel are indeterminate spawners, so a direct conversion of total annual egg production to spawning-stock biomass using prespawning-season estimates of fecundity is not viable. There is also evidence that potential fecundity per kg spawning female increases with fish weight. A linked separable–ADAPT VPA (SAD) model was developed that combines data on total catch, catch-at-age, and total annual egg production with data on potential and realized fecundity to provide population estimates for western horse mackerel. The model accounts for potential fecundity as a function of fish weight and for the development of a targeted fishery on the strong 1982 year class. Simulations confirm that the SAD model is able to reproduce population estimates without bias under a range of scenarios, except where there is a trend in realized fecundity. This underscores the need for improved information on realized fecundity, or alternatively the need to develop management plans that are robust to this source of uncertainty.

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.

scholarly journals Investigating the use of proxies for fecundity to improve management advice for western horse mackerel Trachurus trachurus

2006 ◽  
Vol 63 (1) ◽  
pp. 25-35 ◽  
Author(s):  
J.A.A. De Oliveira ◽  
B.A. Roel ◽  
M. Dickey-Collas
Keyword(s):  
Egg Production ◽  
Stock Assessment ◽  
Biological Indicators ◽  
Horse Mackerel ◽  
Feeding Intensity ◽  
Short Time Series ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Management Advice ◽  
Short Time

Abstract Observations of fecundity from the 2001 western horse mackerel spawning-stock biomass survey suggest that the species is an indeterminate spawner. Therefore, estimates of fecundity based on biological analyses and until recently used in the calibration of the stock assessment are now questioned. The stock is assessed by fitting a linked Separable and ADAPT VPA-based model to the catch-at-age data and to the egg production estimates. Currently, the assumption is that egg production and spawning-stock biomass are linked by a constant but unknown fecundity parameter, estimated within the model. In this study, the effects of introducing relationships linking biological indicators of fecundity, such as lipid content or feeding intensity during the spawning season, to actual fecundity are examined within a simulation framework. Simulations suggest that when the underlying relationships between fecundity and the proxy are poorly described, weak, or based on a relatively short time-series of data, the assumption of constant fecundity will result in better management advice than using the proxy.

Distribution and abundance of eggs and estimation of spawning stock biomass of anchovy, Engraulis encrasicolus (Linnaeus, 1758), in the south-eastern Adriatic Sea

2015 ◽  
Vol 95 (5) ◽  
pp. 1051-1059 ◽  
Author(s):  
Milica Mandić ◽  
Slobodan Regner ◽  
Mirko Đurović ◽  
Aleksandar Joksimović ◽  
Ana Pešić ◽  
...  
Keyword(s):  
Egg Production ◽  
Adriatic Sea ◽  
Production Method ◽  
Seasonal Distribution ◽  
The South ◽  
South Eastern ◽  
Stock Biomass ◽  
Spawning Stock ◽  
First Time ◽  
Egg Abundance

Seasonal distribution and abundance of anchovy eggs were analysed during three scientific cruises carried out from summer 2006 to summer 2007 in the Boka Kotorska Bay, and one cruise in July 2008 in the open waters of the south-eastern Adriatic Sea. Daily egg production method (DEPM) was applied for the first time for estimation of the anchovy spawning stock biomass in the south-eastern Adriatic Sea. The daily egg production was 13–581 eggs day−1 within the bay, and 42–110 eggs day−1 in the open waters. Anchovy egg abundance was highest in spring inside the Bay of Kotor (one of the innermost and eutrophic sub-bays of the Boka Kotorska Bay), which indicates that the conditions for anchovy spawning are very favourable in this part of the Adriatic Sea, even when temperatures are below the optimum. This study has shown that the Boka Kotorska Bay is an area of very intensive spawning of anchovy, and that small-size anchovies live and spawn in the bay, and after spawning migrate towards open waters. The length at which 50% of anchovy were mature (L50) was calculated as 9.28 for females and 9.02 for males. Spawning stock biomass was at a stable level during the period of investigation.

Estimation of the spawning stock biomass of blue grenadier (Macruronus novaezelandiae) off western Tasmania based upon the annual egg production method

1999 ◽  
Vol 50 (3) ◽  
pp. 197 ◽  
Author(s):  
C. M. Bulman ◽  
J. A. Koslow ◽  
K. A. Haskard
Keyword(s):  
Egg Production ◽  
Production Method ◽  
Confidence Limits ◽  
A Value ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Egg Density ◽  
Spawning Periods ◽  
Total Stock ◽  
Spawning Biomass

Egg production of the blue grenadier, Macruronus novaezelandiae, spawning stock off western Tasmania was surveyed from June through September in 1994 and 1995. In each year, daily egg production rates were calculated for each of three surveys and a normal curve was fitted to estimate annual egg production. The CV for the egg production estimate for the survey at the peak of the 1995 season was 14%. Daily egg mortality was not significant in any survey, but a value of 5% was assumed. The spawning biomass of blue grenadier on the west coast of Tasmania was estimated to be between 83 660 and 100 073 t in 1994 and between 59 727 and 71 376 t in 1995. Confidence limits of the estimates were obtained by a bootstrap where the highly skewed egg density data were resampled. Biomass was approximately inversely proportional to incubation time. Increases or decreases in mortality resulted in slightly smaller increases or decreases of biomass respectively. Uncertainty of the sex ratio between spawning and non-spawning periods caused the largest variation in biomass estimate (~30%). The proportion of the population that spawns each year remains a further uncertainty in the estimate of total stock biomass.

scholarly journals Macroscopic vs. microscopic identification of the maturity stages of female horse mackerel

2009 ◽  
Vol 66 (3) ◽  
pp. 509-516 ◽  
Author(s):  
Ana Maria Costa
Keyword(s):  
Horse Mackerel ◽  
Percentage Error ◽  
Maturity Stage ◽  
Trachurus Trachurus ◽  
Microscopic Identification ◽  
Maturity Stages ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Macroscopic Identification

Abstract Costa, A. M. 2009. Macroscopic vs. microscopic identification of the maturity stages of female horse mackerel. – ICES Journal of Marine Science, 66: 509–516. The consequences to fisheries management of erroneous macroscopic identification of maturity stages are evaluated. The percentage error in macroscopic identification of maturity stages of female horse mackerel (Trachurus trachurus) from the Portuguese coast was determined and analysed by maturity stage, between the periods January–June and July–December, between research surveys and commercial landings, and between per year and month and by length class, to assess its implications in determination of spawning season, maturity ogives, and spawning-stock biomass. The highest percentage errors in macroscopic identification were between late ripening and partly spent stages, in fish >30 cm, and for all fish collected in 1998 and 2005. Late ripening was generally macroscopically underestimated, and the partly spent stage overestimated. The implications for the information provided to the ICES assessment working group are analysed.

scholarly journals Fecundity regulation in horse mackerel

2013 ◽  
Vol 71 (3) ◽  
pp. 546-558 ◽  
Author(s):  
Cindy J. G. van Damme ◽  
Anders Thorsen ◽  
Merete Fonn ◽  
Paula Alvarez ◽  
Dolores Garabana ◽  
...  
Keyword(s):  
Lipid Content ◽  
Egg Production ◽  
Gonadosomatic Index ◽  
Production Method ◽  
Spawning Season ◽  
Horse Mackerel ◽  
Hepatosomatic Index ◽  
Batch Fecundity ◽  
Production Methods ◽  
Unbiased Estimates

Abstract Egg production methods have been used successfully in the provision of advice for fisheries management. These methods need accurate and unbiased estimates of fecundity. We explore the reproductive strategy of horse mackerel and estimation of fecundity. Fecundity and fecundity regulation in relation to condition was investigated over a number of years. Fulton's K, lipid content, and hepatosomatic index increased after the start of spawning, though decreased again at the end of spawning. The increase in the gonadosomatic index, fecundity, and body condition after the onset of spawning suggests that horse mackerel utilizes food resources during the spawning season and might be an income breeder. However, the decline in K and lipid before the spawning season suggests that the first batch of oocytes is developed on stored energy. Fecundity varied between years and within a spawning season. Over latitude, variations in fecundity were small. K and lipid content are not reliable indices as proxy for fecundity. Batch fecundity appears to be heterogeneous across the spawning season but homogeneous across latitude. The homogeneity of batch fecundity over latitude could indicate that the daily egg production method is an appropriate approach for estimating the abundance of a wide ranging species, as horse mackerel.

scholarly journals First thorough assessment of de novo oocyte recruitment in a teleost serial spawner, the Northeast Atlantic mackerel (Scomber scombrus) case

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Thassya C. dos Santos Schmidt ◽  
Anders Thorsen ◽  
Aril Slotte ◽  
Leif Nøttestad ◽  
Olav S. Kjesbu
Keyword(s):  
Egg Production ◽  
De Novo ◽  
Seasonal Pattern ◽  
Production Method ◽  
Spawning Period ◽  
Northeast Atlantic ◽  
Atlantic Mackerel ◽  
Scomber Scombrus ◽  
Stock Biomass ◽  
Spawning Stock

AbstractThe understanding of teleost fecundity type (determinate or indeterminate) is essential when deciding which egg production method should be applied to ultimately estimate spawning stock biomass. The fecundity type is, however, unknown or controversial for several commercial stocks, including the Northeast Atlantic mackerel (Scomber scombrus). Aiming at solving this problem, we applied state-of-the-art laboratory methods to document the mackerel fecundity type, including any de novo oocyte recruitment during spawning. Initially, active mackerel spawning females were precisely classified according to their spawning status. The number and size of all phasei-specific oocytes (12 phases), with a special attention to previtellogenic oocytes phases (PVO [PVO2 to PVO4a–c]), were also thoroughly investigated. Examinations of relative fecundity (RFi) clarified that the latest phase of PVOs (PVO4c) are de novo recruited to the cortical alveoli–vitellogenic pool during the spawning period, resulting in a dome-shaped seasonal pattern in RFi. Hence, we unequivocally classify mackerel as a true indeterminate spawner. As PVO4c oocytes were currently identified around 230 µm, mackerel fecundity counts should rather use this diameter as the lower threshold instead of historically 185 µm. Any use of a too low threshold value in this context will inevitably lead to an overestimation of RFi and thereby underestimated spawning stock biomass.

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