Spawning biomass of Argentine anchovy (Engraulis anchoita) from 1996 to 2004 using the Daily Egg Production Method

The Daily Egg Production Method (DEPM) was used to compute spawning biomass of Engraulis anchoita off Argentina. Estimates of the daily egg production (P0) for the northern stock ranged from 594 to 936 eggs m−2, whereas the annual means of the Patagonian stock ranged from 185 to 605 eggs m−2. The mean values estimated for the Argentine anchovy DEPM parameters were characterized by inter-annual differences greater than inter-regional differences with the exception of P0. For the northern population, the estimates of mean weight of mature females ranged from 15 to 26 g, the relative batch fecundity from 414 to 600 eggs g−1, the spawning frequency (S) from 0.078 to 0.179, and the females ratio from 0.519 to 0.622 of the spawning stock. The estimates corresponding to the Patagonian stock were similar being 15 to 24 g, 418 to 583 eggs g−1, 0.079 to 0.244, and 0.394 to 0.590, respectively. The annual estimates of the spawning biomass for the northern and Patagonian populations ranged between 1.6–3.5 and 0.3–1.5 million metric tons, respectively. A weakness in the application of DEPM was the low precision in the estimation of the daily egg production and the spawning fraction. Alternative methodologies to increase the precision of P0 and S are discussed. In spite of the high variance of the spawning biomass estimates, the use of DEPM offers valuable information to adjust acoustic estimates and provides time series of anchovy population size and biological parameters for basic research.

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

Marine and Freshwater Research ◽

10.1071/mf98104 ◽

1999 ◽

Vol 50 (3) ◽

pp. 197 ◽

Cited By ~ 8

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.

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

ICES Journal of Marine Science ◽

10.1093/icesjms/fsp169 ◽

2009 ◽

Vol 66 (9) ◽

pp. 1999-2011 ◽

Cited By ~ 13

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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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 ◽

10.1093/icesjms/fsp066 ◽

2009 ◽

Vol 66 (4) ◽

pp. 617-622 ◽

Cited By ~ 13

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.

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Atlantic mackerel daily spawning dynamics and implications for batch fecundity estimations

ICES Journal of Marine Science ◽

10.1093/icesjms/fsy033 ◽

2018 ◽

Vol 75 (5) ◽

pp. 1647-1654

Author(s):

K Ganias ◽

D Marmara ◽

A Solla ◽

D Garabana ◽

R Dominguez-Petit

Keyword(s):

Egg Production ◽

Time Window ◽

Production Method ◽

Time Of Day ◽

Batch Fecundity ◽

Atlantic Mackerel ◽

Spawning Frequency ◽

Scomber Scombrus ◽

Daily Spawning

Abstract The present study contributes to a better understanding of the daily spawning dynamics of southern NEA mackerel (Scomber scombrus) with implications for the estimation of batch fecundity. It shows that there is a time window during the day, mainly in the afternoon, during which the advanced oocyte mode in imminent spawners separates from the remaining, smaller oocytes. This synchronicity in the separation of the spawning batch amongst imminent spawners corroborates evidence for the existence of daily spawning synchronicity in the population. This is particularly important for applications of the daily egg production method, DEPM, because such pattern facilitates both the ageing of eggs for the estimation of the daily egg production at sea and the ageing of postovulatory follicles for the estimation of spawning frequency. For NEA mackerel, batch fecundity could only be measured when a clear hiatus was established between the spawning batch and the smaller oocytes. Hydrated females that do not show such hiatus would not be valid for batch fecundity measurements suggesting that the “hydrated oocytes method” is not fully applicable for this stock. Knowing the time of day at which the batch is separated, will facilitate the sampling of valid females for the estimation of batch fecundity.

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Use of the daily egg production method to estimate the stock size of Western Australian sardines (Sardinops sagax)

Marine and Freshwater Research ◽

10.1071/mf9960819 ◽

1996 ◽

Vol 47 (6) ◽

pp. 819 ◽

Cited By ~ 18

Author(s):

WJ Fletcher ◽

NCH Lo ◽

EA Hayes ◽

RJ Tregonning ◽

SJ Blight

Keyword(s):

Western Australia ◽

Egg Production ◽

Production Method ◽

Purse Seine ◽

Batch Fecundity ◽

Stock Size ◽

Production Values ◽

Sardinops Sagax ◽

Western Australian ◽

Spawning Biomass

The daily egg production method was used to estimate the spawning biomass of the sardine Sardinops sagax in the Albany region of Western Australia. Plankton surveys covering 10000 - 14000 km² were completed in July of 1991 and 1992 in three to five days using up to three boats. Adult sardines were obtained from the local purse-seine fleet. The spawning area was similar in both years at approximately 3800 km² (1100 nmile²), but the number of eggs collected was larger in 1991 with egg production values of 6.5 per 0.05 m2 day-1 compared with 3.9 per 0.05 m2 day-1 in 1992. The average batch fecundity values were similar (approximately 11000 eggs female-1) as were the proportions spawning (0.13 in 1991; 0.09 in 1992). The calculated biomass estimates were 23 121 t (CV = 0.51) and 16 121 t (CV = 0.44) in 1991 and 1992 respectively.

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A new ageing method for eggs of fish species with daily spawning synchronicity

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f01-168 ◽

2001 ◽

Vol 58 (12) ◽

pp. 2330-2340 ◽

Cited By ~ 19

Author(s):

M Bernal ◽

D L Borchers ◽

L Valdés ◽

A Lago de Lanzós ◽

S T Buckland

Keyword(s):

Egg Production ◽

Production Method ◽

Biological Information ◽

Northern Spain ◽

Egg Development ◽

Spawning Period ◽

Spawning Frequency ◽

Resampling Method ◽

Daily Spawning ◽

Ageing Methods

A new method for ageing staged eggs of fish is presented. The method is intended for species that show spawning synchronicity and for which the egg phase can be classified into development stages, each of which lasts less than a day, such as sardines and anchovies. It combines biological information on the daily frequency of spawning and egg development rates, via a probabilistic resampling method. A general methodology that allows the use of models of daily spawning frequency and egg development as a function of temperature is provided and applied to sardine egg data from three surveys in northern Spain. Unlike previous ageing methods, the proposed method allows for the variability of egg ages in a way that reflects the extent of the assumed daily spawning period, and estimates of the uncertainty in the stage-to-age conversion can be obtained. These estimates of uncertainty can be incorporated into subsequent analyses that involve age as a covariate, such as in the daily egg production method (DEPM), thus allowing more reliable estimates of the variance of egg production.

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Daily egg production of anchovy in European waters

ICES Journal of Marine Science ◽

10.1016/j.icesjms.2004.07.018 ◽

2004 ◽

Vol 61 (6) ◽

pp. 944-958 ◽

Cited By ~ 106

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.

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Evaluating the use of the Daily Egg Production Method for stock assessment of blue mackerel, Scomber australasicus

Marine and Freshwater Research ◽

10.1071/mf08134 ◽

2009 ◽

Vol 60 (2) ◽

pp. 112 ◽

Cited By ~ 7

Author(s):

T. M. Ward ◽

P. J. Rogers ◽

L. J. McLeay ◽

R. McGarvey

Keyword(s):

Egg Production ◽

Early Stage ◽

Stock Assessment ◽

Production Method ◽

Spawning Area ◽

Eastern Australia ◽

Genetic Techniques ◽

Ovulatory Follicles ◽

Improved Methods ◽

Spawning Biomass

The present study evaluates the suitability of the Daily Egg Production Method (DEPM) for stock assessment of blue mackerel, Scomber australasicus and assesses methodological options for future applications. In southern Australia, estimates of mean daily egg production were higher for Californian Vertical Egg Tow (CalVET) nets than bongo nets, and in eastern Australia, were higher in October 2003 than July 2004. Estimates of spawning area for southern Australia were three times higher for bongo nets than CalVET nets. Similar estimates of spawning area were obtained using standard (manual) gridding and natural neighbour methods. Large samples and reliable estimates of all adult parameters were obtained for southern Australia. Relatively few spawning adults were collected off eastern Australia. Preliminary best estimates of spawning biomass for southern and eastern Australia were 56 228 t and 29 578 t, respectively, with most estimates within the ranges of 45 000–68 000 t and 20 000–40 000 t respectively. The DEPM is suitable for stock assessment of S. australasicus. Several technical refinements are required to enhance future applications, including: genetic techniques for identifying early stage eggs; a temperature–egg development key; improved methods for sampling adults off eastern Australia; and measurements of the degeneration rates of post-ovulatory follicles at several temperatures.

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Growth, reproductive cycle, and movement of berried European lobsters (Homarus gammarus) in a local stock off southwestern Norway

ICES Journal of Marine Science ◽

10.1093/icesjms/fsl020 ◽

2006 ◽

Vol 64 (2) ◽

pp. 288-297 ◽

Cited By ~ 44

Author(s):

Ann-Lisbeth Agnalt ◽

Tore S. Kristiansen ◽

Knut E. Jørstad

Keyword(s):

Reproductive Cycle ◽

Egg Production ◽

Reproductive Potential ◽

Fishing Ground ◽

Fishing Mortality ◽

Homarus Gammarus ◽

Spawning Stock ◽

Release Area ◽

Local Stock ◽

Spawning Biomass

Abstract Agnatt, A-L., Kristiansen T. S., and Jorstad K. E. 2007. Growth, reproductive cycle, and movement of berried kuropean lobsters (Homarus gammarus) in a local stock off southwestern Norway. – ICES Journal of Marine Science, 64: 288–297. The Norwegian fishery for the European lobster (Homarus gammarus) collapsed between 1960 and 1980, to <10% of its pre-1960 level, and since then the spawning stock seems to be too low to generate good recruitment. In 1998, a project to evaluate the feasibility and effect of protecting berried female lobsters as a management restriction was initiated. The study area selected was previously an important fishing ground in Kvitsøy off southwestern Norway, and 125 000 hatchery-reared juveniles were released between 1990 and 1994. From spring 1998 to spring 2000, a total of 942 wild and 480 cultured berried females was purchased from fishers, individually tagged with a streamer-tag, and released. The proportion of berried females in the landings varied annually from 19 to 58% for wild females, and from 22 to 44% for cultured females. By spring 2000, 23% of the tagged females had been recaptured at least once, and 3% twice or more. Average moult increment was 7 mm carapace length (CL), independent of pre-moult size in both wild and cultured females. Reproduction (spawning) and growth (moulting) alternated in a 2 y cycle for >90% of the females. A small number moulted and spawned a few weeks after hatching. More than 95% of the recaptures were taken within a radius of 1 km of the release area. Egg production varied considerably between seasons. Reproductive potential (RP) of landed berried females underestimated egg production compared with what was actually produced (AE). For the entire period, RP was estimated to be about 15.0 million eggs, and AE to be 17.2 million eggs. Cultured females contributed 27% of AE. To reduce the fishing mortality in a heavily fished and depleted population is vital. A ban on landing berried females would be a valuable first step in attempting to increase the spawning biomass.

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