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

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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Stock assessment of the blue grenadier Macruronus novaezelandiae resource off south-eastern Australia

Marine and Freshwater Research ◽

10.1071/mf99136 ◽

2001 ◽

Vol 52 (4) ◽

pp. 701 ◽

Cited By ~ 31

Author(s):

A. E. Punt ◽

D. C. Smith ◽

R. B. Thomson ◽

M. Haddon ◽

X. He ◽

...

Keyword(s):

Egg Production ◽

Stock Assessment ◽

Production Method ◽

Integrated Analysis ◽

Absolute Abundance ◽

Commercial Catch ◽

Eastern Australia ◽

Class Strength ◽

Catch Rates ◽

Spawning Biomass

The fishery can be divided into two subfisheries (‘spawning’ and ‘non-spawning’). Commercial catch rates for the ‘non-spawning’ subfishery declined from the late 1980s to 1997, whereas those for the ‘spawning’ subfishery exhibit no obvious temporal trend. An ‘Integrated Analysis’ assessment, of the feasibility of reconciling these differing trends, uses catch (landed and discarded), catch rate, length-at-age, and catch-at-age data and estimates of absolute abundance based on the egg-production method. It emphasizes uncertainty due to model assumptions and the data included in the assessment. Use of the discard data allows more precise estimation of the magnitude of recent recruitments. Spawning biomass is estimated to have declined from a peak in 1989–91 to 1999 although fishing mortality has consistently been <6%for each subfishery. One main reason for the reduction in population size is the weakness of year-classes spawned from 1988 to 1993. Differences in catch rates between the two subfisheries can therefore be explained by interactions between the components of the population harvested by the two ‘subfisheries’, and the trends in year-class strength. A risk analysis is used to evaluate the consequences of different future levels of harvest for different assessment assumptions. Overall, the spawning biomass is predicted to increase over the next five to ten years as a result of the strong 1994 and 1995 year-classes, although the extent of this increase remains uncertain.

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Reproductive biology of blue mackerel, Scomber australasicus, off southern and eastern Australia: suitability of the Daily Egg Production Method for stock assessment

Marine and Freshwater Research ◽

10.1071/mf07158 ◽

2009 ◽

Vol 60 (2) ◽

pp. 187 ◽

Cited By ~ 3

Author(s):

P. J. Rogers ◽

T. M. Ward ◽

L. J. McLeay ◽

M. Lowry ◽

R. J. Saunders ◽

...

Keyword(s):

Reproductive Biology ◽

Egg Production ◽

Stock Assessment ◽

Fork Length ◽

Production Method ◽

Spawning Season ◽

Batch Size ◽

Batch Fecundity ◽

Eastern Australia ◽

Mature Fish

The present study investigated the reproductive biology of blue mackerel (Scomber australasicus) off southern and eastern Australia and assessed the suitability of the Daily Egg Production Method (DEPM) for future stock assessment. This analysis revealed that S. australasicus is a serial spawner with asynchronous oocyte development and indeterminate fecundity. S. australasicus spawns between November and April off southern Australia and between July and October off eastern Australia. In southern Australia, ~50% of males and females were mature at 236.5 and 286.8 mm fork length (FL), respectively. Size at ~50% maturity could not be estimated reliably for eastern Australia owing to the smaller proportion of mature fish in samples. Mean spawning frequencies ranged from 2 to 11 days off southern Australia. Batch fecundity was related to fish size and mean batch size was 69 894 ± 4361 oocytes per batch and 134 oocytes per g of weight. The timing and duration of the spawning season, size at maturity, spawning frequency and batch fecundity of S. australasicus off southern Australia were consistent with those of S. japonicus in the northern Pacific Ocean. The present study’s estimates of adult reproductive parameters of S. australasicus off southern Australia were suitable for the application of the DEPM for estimating spawning biomass. Collecting representative samples of mature fish from waters off eastern Australia during the spawning season is a high priority for future stock assessment of this species.

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

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f98-143 ◽

1998 ◽

Vol 55 (12) ◽

pp. 2608-2621 ◽

Cited By ~ 23

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.

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

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315408003019 ◽

2008 ◽

Vol 89 (4) ◽

pp. 829-837 ◽

Cited By ~ 15

Author(s):

Marcelo Pájaro ◽

Gustavo J. Macchi ◽

Ezequiel Leonarduzzi ◽

Jorge E. Hansen

Keyword(s):

Regional Differences ◽

Egg Production ◽

Basic Research ◽

Production Method ◽

Mean Values ◽

Spawning Frequency ◽

Spawning Stock ◽

The Mean ◽

Annual Means ◽

Spawning Biomass

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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