Report of the Workshop on Survey Design and Mackerel and ... Reports/Expert... · the 2013 mackerel and horse mackerel egg survey. ... For indeterminate spawners it is not possible

ICES WKMSPA REPORT 2012 SCICOM STEERING GROUP ON ECOSYSTEM SURVEYS SCIENCE AND TECHNOLOGY

ICES CM 2012/SSGESST:05

REF. SCICOM, WGISUR, ACOM & WGWIDE

Report of the Workshop on Survey Design and Mackerel and Horse Mackerel Spawning Strategy (WKMSPA)

16-17 April 2012

Galway, Ireland

International Council for the Exploration of the Sea Conseil International pour l’Exploration de la Mer

H. C. Andersens Boulevard 44–46 DK-1553 Copenhagen V Denmark Telephone (+45) 33 38 67 00 Telefax (+45) 33 93 42 15 www.ices.dk [email protected]

Recommended format for purposes of citation:

ICES. 2012. Report of the Workshop on Survey Design and Mackerel and Horse Mackerel Spawning Strategy (WKMSPA), 16-17 April 2012, Galway, Ireland. ICES CM 2012/SSGESST:05. 28 pp.

For permission to reproduce material from this publication, please apply to the Gen-eral Secretary.

The document is a report of an Expert Group under the auspices of the International Council for the Exploration of the Sea and does not necessarily represent the views of the Council.

© 2012 International Council for the Exploration of the Sea

ICES WKMSPA REPORT 2012 | i

Contents

Executive summary ................................................................................................................ 1

1 Opening of the meeting ................................................................................................ 2

2 Adoption of the agenda ................................................................................................ 2

3 Spawning strategies of mackerel and horse mackerel and implications for the survey design (ToR a) ...................................................................................... 3

3.1 Batch fecundity and oocyte growth rate in mackerel ...................................... 4 3.2 Horse mackerel batch fecundity estimates ........................................................ 7

4 Daily egg production method (DEPM; ToR b) ......................................................... 9

4.1 The Daily Egg Production Method and potential application to mackerel and horse mackerel in the Northeast Atlantic ................................. 9

5 Determining DEPM parameters from the historic mackerel and horse mackerel egg survey sampling (ToR c) .................................................................... 12

5.1 SSB estimation using the DEPM method ........................................................ 12

5.2 Daily egg production estimates and peak spawning of Northeast Atlantic mackerel and horse mackerel 2004 – 2010 ........................................ 12

5.3 Calculation of spawning fraction for mackerel and horse mackerel ........... 14

6 Recommendations for the future survey design of the triennial mackerel and horse mackerel egg surveys .............................................................. 16

7 References ..................................................................................................................... 19

Annex 1: List of participants............................................................................................... 21

Annex 2: Agenda ................................................................................................................... 24

Annex 3: Notes from the discussion on survey design.................................................. 25

Annex 4: Recommendations ............................................................................................... 27

Annex 5: Working documents ............................................................................................ 28

ICES WKMSPA REPORT 2012 | 1

Executive summary

The ICES Workshop on Survey Design and Mackerel and Horse Mackerel Spawning Strategy (WKMSPA), chaired by Cindy van Damme (IMARES, The Netherlands) and Finlay Burns (MSS, UK), met in Galway from 16–17 April 2012, to discuss spawning strategies of mackerel and horse mackerel and recommend on the survey design for the 2013 mackerel and horse mackerel egg survey.

Latest results on mackerel and horse mackerel fecundity type were presented and discussed. Both mackerel and horse mackerel are probably indeterminate spawners. For indeterminate spawners it is not possible to reliably estimate potential fecundity, since they keep recruiting oocytes to the vitellogenic stock after spawning has com-menced. Potential fecundity is necessary to use the Annual Egg Production Method (AEPM) to estimate SSB from egg production. The Daily Egg Production Method (DEPM) uses batch fecundity and is thus a more accurate method to estimate SSB from egg production in indeterminate spawners.

During the workshop daily egg productions, peak spawning and spawning areas of mackerel and horse mackerel from the last 3 triennial (2004, 2007, 2010) were pre-sented, as well as batch fecundity for both species. Using the WGWIDE SSB and AEPM SSB estimates from these years the spawning fraction was calculated. The calculated spawning fractions were within the ranges found in other studies.

The workshop recommended, based on the calculated spawning fractions, that for the 2013 mackerel and horse mackerel survey:

• The survey design should not be changed to be able to continue the AEPM time-series.

• Participants in a dedicated period (of assumed peak spawning) will at-tempt to collect extra adult samples for estimation of adult parameters in DEPM. First priority in those dedicated periods will be egg sampling cov-ering the whole spawning area.

• Creation of peak spawning areas based on previous WGMEGS spawning results in the perceived peak spawning period for collection of additional adult samples for estimation of DEPM adult parameters.

• Attempt a comparison between AEPM and DEPM based on the 2013 sur-vey results.

2 | ICES WKMSPA REPORT 2012

1 Opening of the meeting

The Workshop on Survey Design and Mackerel and Horse Mackerel Spawning Strat-egy (WKMSPA), met 16–17 April 2012 in Galway, Ireland. 20 participants from 10 countries (representing 12 different institutes) participated in the meeting. The par-ticipant list is in Annex 1.

The terms of reference for the meeting were:

a) Review the actual research results on the spawning strategies on mackerel and horse mackerel with their possible implications on the survey design and the historical time-series;

b) Obtain expert information on the sampling program for eggs as well as adult parameters (batch fecundity, batch frequency, duration of spawning, dura-tion of POFs, spawning fraction) for a possible DEPM survey for both spe-cies;

c) Investigate the estimation procedure for historical data and future data based on the DEPM method for the SSB;

d) Give recommendations on the future format of the Triennial mackerel and horse mackerel egg survey.

2 Adoption of the agenda

The agenda addressed all ToRs and was adopted without changes. The agenda can be found in Annex 2.


3 Spawning strategies of mackerel and horse mackerel and implications for the survey design (ToR a)

Priede and Watson (1993; 1997) compared the use of the Daily Egg Production Method (DEPM) and Annual Egg Production Method (AEPM) for the estimation of spawning-stock biomass (SSB) in mackerel during the 1989 and 1992 egg surveys. While results for both methods differed only slightly by 15% during the 1989 survey (Priede and Watson, 1993), the 1992 comparison yielded almost a doubling of the SSB in the AEPM as compared to the DEPM (Priede and Watson, 1997). While Greer Walker et al. (1994) found characteristics for both fecundity types in mackerel they concluded that mackerel fecundity was determinate. The same conclusion was drawn by Priede and Watson (1997) by stating that “… whilst biologically fecundity in mackerel is indeterminate, for the purposes of stock biomass estimation, by applying certain corrections, fecundity can be regarded as determinate. As a result the mack-erel egg survey continued to be designed as an AEPM survey.

Most Scombridae are considered indeterminate spawners, e.g. blue mackerel Scomber australasicus (Ward et al., 2009) and chub mackerel Scomber japonicus (Watanabe et al., 1999). For these species a DEPM survey is carried out to estimate SSB (Watanabe et al., 1999, Ward et al., 2009).

Results from the triennial egg surveys are inconclusive as to the fecundity type of horse mackerel Trachurus trachurus but they indicate indeterminacy. For southern horse mackerel IPIMAR performs a DEPM survey (ICES, 2011). Other studies con-cluded that horse mackerel has an indeterminate fecundity type (Karlou-Riga and Economidis, 1997; Abaunza et al., 2003; Gordo et al., 2008; Ndjaula et al., 2009). Other Carangidae are also considered indeterminate spawners, e.g. Chilean jack mackerel Trachurus murphyi (Ruiz et al., 2008).

Recent experiments carried out by IMR, Norway, with captive mackerel and horse mackerel have been successful in development of oocytes and gonads, but spawning of both species has been problematic. No proof was available from these experiments to show the definite fecundity type of both species.

During the meeting a comparative study was presented on fecundity type regulation in marine fish (Damme et al. in prep). It describes the mechanisms behind fecundity type regulation and concluded that food availability is the most important parameter determining fecundity type in marine fish. If fish have no food available during the spawning season they have a determinate fecundity type. If females do have food available during the spawning season, theoretically they have an indeterminate fe-cundity type. Also fecundity type is flexible, depending upon local environmental conditions, especially availability of food and therefore feeding. PCA analysis in the study placed mackerel and horse mackerel on the indeterminate side of the graph also suggesting they have an indeterminate fecundity type.

There is no experimental evidence of mackerel and horse mackerel being indetermi-nate spawners. In experiments both, mackerel and horse mackerel, developed oocytes but did not spawn. However, we do know from the observations during surveys that both species feed during the spawning season and hence they most probably have an indeterminate fecundity type. Priede and Watson (1997) calculated that mackerel have to feed in order to realize their maximum reproductive potential during spawn-ing. This also points to indeterminacy.


Indeterminate spawners keep recruiting oocytes from the previtellogenic stock dur-ing the spawning season. It is therefore not possible to estimate potential fecundity prior to spawning. AEPM, such as the present mackerel and horse mackerel egg sur-vey design, requires reliable estimates of potential fecundity to estimate SSB from the total annual egg production. Hence they can only be used to estimate SSB for deter-minate spawning species. DEPM can be used to determine SSB from egg productions for indeterminate as well as determinate spawners, since it uses batch fecundity and spawning fraction. The DEPM method requires intensive, high resolution sampling of both the eggs and adults at the peak of spawning.

3.1 Batch fecundity and oocyte growth rate in mackerel

During the meeting a study was presented on batch fecundity and oocyte growth in mackerel (Thorsen et al. in prep).

Oocyte growth rates

The current AEPM that is used to estimate SSB is based on the assumption that Mackerel is a determinate spawner. This implies that in the prespawning fish all the maturing oocytes that are going to be spawned in the coming season can be distin-guished from the immature pool of oocytes. This implies that there is a size gap be-tween the maturing pool and the immature pool of oocytes. In Mackerel no such size gap exists in the prespawning fish. However, Greer Walker et al. (1994) estimated from samples taken in the field that the growth rate of the maturing oocytes was not large enough for the oocytes to grow from an immature size to a prespawning size within the time frame of a spawning season (60 to 90 days). This was their main ar-gument for concluding that the Mackerel for practical purposes could be regarded as a determinate spawner.

Between 2008 and 2009 IMR (Norway) conducted an experiment with captive mack-erel. Ovary samples from the period of maturation first showed low growth rates (1 to 1.5 µm/day), but when temperature was raised two weeks before spawning the growth rate increased 8 fold to about 10 µm/day. Such a temperature increase is a likely scenario in the wild situation. With this higher growth rate it is not unlikely that immature oocytes (< 185 µm) could reach a prespawning size of 600 to 700 µm within the time frame of a spawning season of 60 to 90 days. Higher temperatures might increase the growth rate even further.


Figure 3.1.1. Oocyte diameter leading cohort (95 % percentile) of mackerel in captivity. Upper coloured areas show water temperature. In the narrow orange zone temperature was gradually raised from 9 to 14 °C. Error bars show standard deviation.

Batch fecundity

If the DEPM is going to be used for future estimates of SSB, data on batch fecundity will need to be collected. To estimate batch fecundity the best method is usually to count the number of hydrating oocytes in preweighed subsamples. At the workshop the intention was to use data and samples from the previous triennial surveys to make DEPM calculations. To get batch fecundity data, counts were performed on pictures that had earlier been used for fecundity counts. Since samples used for fe-cundity counts are from prespawning fish only (no spawning markers present), such samples would in all likelihood be rare and will only include samples where the first batch is about to be formed. In order to locate such samples oocyte size frequency histograms were created of all analysed fecundity samples and analysed for ovaries where a batch of hydrating oocytes could be seen being formed (Figure 3.1.2). Includ-ing all the sample material from the 2010 survey a total of 8 fish were found that were suitable to be used for batch fecundity.


Figure 2. Oocyte size frequency histogram showing formation of a new egg batch. Red arrow indicate size threshold used for this fish to separate between oocytes belonging to the batch and the remaining oocytes.

Batch fecundity counts were then worked up from the same pictures as had been used for fecundity counts. On average 23 hydrating oocytes were observed (12 to 57) in these samples corresponding to an average relative batch fecundity of 37 (4 to 88). To calculate the average batch number the relative potential fecundity was divided by the relative batch fecundity to obtain a mean value of 31 (14 to 46). Walker et al 1994, suggests that the spawning period for Mackerel is 60 to 90 days with a spawn-ing interval of 2 days. These 31 estimated batches would then correspond to a spawn-ing period of 62 days, which is in agreement with this. However, when evaluating the batch fecundity numbers it should be kept in mind that all the batches counted were probably the first batch and it is a plausible assumption that the first batch differs in size from the average batch size. For cod (Kjesbu, 1989), the batches in the beginning and the end of the spawning season are considerable smaller than in the middle.

Batch fecundity counting was performed on 25 µl samples originally intended for potential fecundity counting (Table 3.1.1). As already mentioned these samples gave counts from 12 to 57 (average 23). Counts this low are less than ideal with regards to precision. Batch fecundity samples taken in future will therefore have to be larger, - 100 µl was suggested.


Table 3.1.1. Relative batch fecundity and relative potential fecundity of Mackerel from the 2010 survey.

SAMPLE

REFERENCE

BATCH

OOCYTE

COUNT (N)

BATCH

DIAMETER

THRESHOLD (µM)

RELATIVE BATCH

FECUNDITY (N/G FISH)

RELATIVE

FECUNDITY (N/G FISH)

NUMBER OF

BATCHES (N)

A069 57 450 34

A079 11 600 4

C115 25 700 65 903 14

G006 32 600 88 1844 21

G010 12 610 12 538 46

G023 16 610 21 816 39

G112 22 610 45 1351 30

O018 12 710 31 1048 34

Average 23 611 37 1083 31

3.2 Horse mackerel batch fecundity estimates

During the meeting a working document was presented on batch fecundity in horse mackerel from the last 3 triennial egg surveys (Damme et al. in prep).

Fecundity type and fecundity regulation in horse mackerel was investigated based on the samples from the triennial egg survey 2004, 2007 and 2010. Body condition and fecundity of horse mackerel was estimated using a gravimetric and image analysis system. Horse mackerel spawning occurs at night-time. Fulton’s K and lipid content peaked before but decreased just prior to the spawning season. K, lipid content and hepatosomatic index increased after the start of spawning, although they decreased again at the end of spawning. GSI was very low before the onset of spawning but increased during spawning and decreased at the end of spawning.

Fecundity increased after the onset of spawning and decreased at the end of the spawning season. Fecundity increased with increasing K, but no relationship was found with lipid content. However, both K and lipid content are not reliable indices to use as a proxy for fecundity.

The increase in GSI, fecundity and body condition after the onset of spawning sup-port the idea that horse mackerel is an income breeder, utilizing food resources dur-ing the spawning season for reproduction, and has an indeterminate fecundity. However, the sharp decline in K and lipid content prior to the spawning season sug-gest that the first batch of oocytes is developed on stored energy.

Batch fecundity was significantly different between the years (ANOVA, p < 0.001) and highest batch fecundity was found in 2007 (Table 3.2.1). Batch fecundity was comparable to other studies off the Portuguese coast (Abaunza et al., 2008, Goncalves et al., 2009) and in the Mediterranean (Karlou-Riga and Economidis, 1997).


Table 3.2.1. Horse mackerel batch fecundity and oocyte diameters in the different years (standard deviation in brackets).

Year Mean oocyte diameter (µm) Relative batch fecundity (N oocytes per gram)

2004 352.1 (69.4) 193.4 (172.7)

2007 385.9 (90.6) 406.2 (275.7)

2010 316.9 (54.2) 284.6 (199.3)


4 Daily egg production method (DEPM; ToR b)

4.1 The Daily Egg Production Method and potential application to mackerel and horse mackerel in the Northeast Atlantic

The daily egg production method (DEPM) developed in the late 1970s at the South-west Fisheries Center, La Jolla, CA, NMFS - USA, for the assessment of northern an-chovy. This is an indeterminate spawner with pelagic eggs (Parker, 1980; Hunter and Goldberg, 1980; Lasker, 1985). It has subsequently been applied to many indetermi-nate fish species, mainly pelagics but also to other species (see reviews in Alheit, 1993; Hunter and Lo, 1997; Stratoudakis et al., 2006; Bernal et al., 2012). Several scombroids and carangidae are considered indeterminate spawners and have been the object of studies either to obtain their reproductive parameters of daily specific fecundity or to apply the DEPM (Dickerson et al., 1992; Karlou-Riga and Economidis, 1997; Macewicz and Hunter, 1993; Priede and Watson, 1993; Ruiz et al., 2009; Ward et al., 2009; Watanabe et al., 1999; Yamada et al., 1998), including the European Southern horse mackerel (Gonçalves et al., 2009). The persisting evidence that European mackerel and horse mackerel are also indeterminate spawners (Greer Walker et al., 1994; Gordo et al., 2008) suggest that the DEPM could be a suitable tool for assessing their SSB.

The DEPM produce SSB estimates from the quotient between the daily egg produc-tion and the daily specific fecundity (D.F. or number of eggs released by unit mass of the spawning population)To estimate the Daily Egg Production, eggs must be sorted and staged to estimate the Daily Egg production per surface unit (P0). Usually this is made by fitting an exponential decay model of egg abundance by age over the spawning grounds (for a constant egg mortality Z) under the assumption of the con-stant egg production during the survey time and across the surveyed areas. The se-cond assumption can be relaxed through a spatial explicit estimate of P0 using General Additive Models (GAMs). Five and four stages are currently applied in the staging of mackerel and horse mackerel eggs in the western areas with a stage-duration of a day or more each. In addition, they do not seem to have a defined daily peak spawning time, which makes it difficult to estimate egg mortality for these spe-cies. Therefore, currently only stage I abundance, corrected for its duration at in-situ temperatures, can be used to estimate daily egg stage I egg production as a proxy for P0. Alternatives would include the refinement of egg staging to obtain multiple stag-es of shorter duration that would allow for a proper ageing of eggs and obtaining of P0 and Z estimates (as made for the southern horse mackerel stock), or inclusion of external estimates — or assumptions — of mortality (as for instance those provided by Portilla et al., 2007) to correct the average daily abundances of stages I.

The Daily Fecundity (DF) is estimated as the product of the sex ratio in weight (R’), the daily relative batch fecundity (F/Wf, or batch fecundity divided by the mean weight of females) and the fraction of mature females spawning per day (S). DEPM adult sampling is cluster sampling of the different schools (Picquelle and Stauffer, 1985) which defines the way to estimate the population mean and variance of the adult parameters. The purpose of the adult sampling is to obtain a representative (unbiased) sample of the spawning population (adults) in all survey periods. All pa-rameters are the weighted means of sample’s parameters.

For F the hydrated oocyte method is usually followed (Hunter et al., 1985), although other advanced maturing oocytes prior to hydration can also be used such as the


oocytes showing nuclear polar migration. This can be of particular utility to mackerel and horse mackerel as current sampling methods do not provide a lot of oocytes at the hydrated stage.

The Spawning fraction (S) is usually measured by the prevalence (%) of mature fe-males with histological indicators of either imminent spawning (during the day of sampling; day 0 spawning cohort), recent past spawning (i.e. less than 24 hours ago, or between 10 and 33 hours ago, etc., corresponding to day_1 spawning cohort) or even from other older spawning cohorts (Hunter and Macewicz, 1985). The require-ment is to know the duration of the process of late maturation prior to ovulation (oo-cytes with nuclear migration or hydrated; Hunter et al., 1985) and of the degeneration rate of the postovulatory follicle in time (Ganias, 2012); this would require some tank or field experiments to assess those biological rates in time. Such studies are lacking for the European mackerel and horse mackerel but studies from other areas could be used to start trying to age the different stages of maturing oocytes or of degeneration of POFs. In any case, at the beginning of the studies of S it is convenient to compare estimates from several potential estimators based on different spawning markers (Rogers et al., 2009; Dickerson et al., 1992; Gonçalves et al., 2009) and a combination of several daily cohorts can produce an increase in the precision of the final estimate.

Spatial heterogeneity in adult fecundity parameters is to be taken into account either by stratification or by spatial modelling of these parameters. Seasonal and spatial differences of the adult parameters have often been reported not only for small pelagics but also for Scombroids and Carangidae which requires some spatial ap-proaches for unbiased estimates. DEPM surveys are conducted preferably during the peak of the spawning season, because adult parameters peak by then and this facili-tates the estimation of these parameters. However the DEPM can be carried out dur-ing other periods as far as it measures concurrent fecundity parameters.

During the workshop a presentation on the DEPM application for the southern horse mackerel stock was presented. A brief description of the methodology as contained within the presentation is contained below and an abstract of the presentation can also be found in Annex 5.

Developments in the DEPM application for the southern stock (ICES division IXa) horse mackerel

The DEPM was applied to the southern stock of horse mackerel since 2007. Since this first DEPM application, several biological aspects relating to the adult and egg phases have been investigated and have been improved. Results were presented on (i) changes in the survey design (sampling grid and gear) used for sampling the entire spawning area; (ii) description of the morphology and development of the eggs of the species T. picturatus, a species that co-occurs in the same distribution area and spawns at the same period as Trachurus trachurus (iii); batch fecundity estimation using two spawning markers (hydrated oocytes and migratory nucleus stage oocytes) and (iv); daily synchronicity investigation.

Since EPM has been applied the sampling design has been adapted. In the initial years the survey grid was wider but progressively changed in order to increase the spatial resolution while guaranteeing coverage of the whole spawning area. From 2007 onwards a semi-adaptive sampling design, along-transects 12 nml apart, using vertical plankton hauls, has been in place; in regions of recurrent higher egg densities the spacing interval between sampling stations is reduced.


Eggs from a fertilization experiment allowed the morphological description of Tra-churus picturatus comparatively to T. trachurus. Eggs of both species are very similar and are present in the southern area during peak spawning for the target species. Measurements on the artificially obtained eggs showed that T. picturatus eggs were slightly larger however, the dimensions of the eggs of both species overlap. T. trachu-rus egg development was described using multinomial modelling

In order to estimate the parameters for DEPM, sampling was also increased for adult fish collection. In 2010 a total of 44 fishing hauls were obtained, 20 from de research vessel and the extra sampling came from commercial vessels. Despite the fact that the number of samples available was higher than before obtaining hydrated females is always a challenge due to fish behaviour and the relatively short duration of this phase. To overcome this difficulty, for fecundity estimation a methodology (de-scribed for other species) involving the use of hydrated oocytes and migratory nucle-us stage oocytes was implemented. Counts and measurements were accomplished using image analysis routines.

To investigate the daily spawning cycle the histological slides were analysed for POFs (recent and old), HO and MN (early and advanced) and the stage I eggs, from all the plankton samples (all surveys), were aged according to the multinomial tem-perature/development model and hour of sampling. The results obtained so far do not show evidence of a daily spawning pattern. However, fishing trawls were not yet obtained for the whole 24 hours period and the duration of the oocyte and POFs phases are not known; further investigation on these issues is crucial to spawning frequency estimation.


5 Determining DEPM parameters from the historic mackerel and horse mackerel egg survey sampling (ToR c)

5.1 SSB estimation using the DEPM method

Using the DEPM method SSB is calculated using the following formula:

𝑆𝑆𝐵 =𝐷𝑎𝑖𝑙𝑦𝐸𝑔𝑔𝑃𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛

𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛𝐷𝑎𝑖𝑙𝑦𝐹𝑒𝑐𝑢𝑛𝑑𝑖𝑡𝑦 (𝐷𝐹′𝑡)= 𝑘

𝐴𝑃0𝑅′𝑆′(𝐹′ 𝑊′𝑓)⁄

where

A = Spawning area

P0 = Daily egg production,

R’ = Sex ratio,

S’ = Spawning fraction,

F’ = Batch fecundity,

Wf = female weight and

k = conversion factor from grams to tonnes.

During the workshop batch fecundity estimates of mackerel and horse mackerel from the last 3 triennial surveys were available (Section 3). Also daily egg production was estimated from these surveys (Section 5.2). Sex ratio for both species is considered to be 1:1. Rather than doing a DEPM SSB calculation with an unreliable spawning frac-tion, the group opted to calculate the spawning fraction that would match the WGWIDE SSB estimates and the AEPM SSB estimates (Section 5.3).

5.2 Daily egg production estimates and peak spawning of Northeast Atlantic mackerel and horse mackerel 2004 – 2010

The daily egg production curves for both the Northeast Atlantic mackerel (southern and western areas) and western horse mackerel were presented for the previous three triennial egg surveys (2004, 2007 and 2010; Figures 5.2.1 – 5.2.3) together with the corresponding stage 1 abundance maps highlighting the periods of peak spawning during these surveys. In order to collect DEPM adult parameters during the 2013 mackerel and horse mackerel egg survey, first the peak spawning period as well as high density spawning areas need to be identified for both species. Peak spawning for the most recent survey in 2010 was used as the reference point for estimating peak spawning in western mackerel as over the 3 survey years peak spawning has oc-curred during different temporal periods.


Figure 5.2.1. Daily egg production curves for mackerel in the western area 2004–2010.

Figure 5.2.2. Daily egg production curves for mackerel in the southern area 2004–2010.


Figure 5.1.3. Daily egg production curves for western horse mackerel in the 2004–2010.

For 2010 peak spawning equated to period 2, between 8 March and 11 April and in the area between 43° – 58°30N. This is fortunate in that it also covers the peak of spawning in the southern area. For the western horse mackerel peak spawning was in period 5 for all 3 survey years which equates to a calendar period of June and in the area between 47° – 54°30N.

5.3 Calculation of spawning fraction for mackerel and horse mackerel

The spawning fraction of mackerel necessary for the estimated egg productions was calculated from both the WGWIDE SSB estimates and the AEPM SSB estimates for the years 2004, 2007 and 2010. The spawning fractions were comparable to spawning fractions from other DEPM studies (Table 5.3.1).

A similarly deduced procedure was used to obtain the spawning fraction for horse mackerel for the same years and the results it yielded were very low (Table 5.3.2).


Table 5.3.1. Spawning fraction estimation for Northeast Atlantic mackerel (western and southern stock combined). Period refers to the different periods sampled in each year (ICES 2005, 2008, 2011).

Table 5.3.2. Spawning fraction estimation for western horse mackerel. Period refers to the different period samples each year (ICES 2005, 2008, 2011).

Year Period WGWIDE SSB (T) AEPM SSB (T) Daily egg production (eggs/m2) Survey area (m2) Batch fecundity (N/g) Sex ratio Spawning fraction (using WGWIDE SSB) Spawning fraction (using AEPM SSB)2004 3 1765752 2748307 11170886199137.60 485261035200.23 37 0.5 0.34 0.222004 4 1765752 2748307 13146083650322.70 607359885790.19 37 0.5 0.40 0.262004 5 1765752 2748307 10929964152857.20 708044012911.88 37 0.5 0.33 0.212007 2 2543583 3646000 18878541343622.00 613096291937.51 37 0.5 0.40 0.282007 3 2543583 3646000 5546790955360.10 628718998655.69 37 0.5 0.12 0.082007 4 2543583 3646000 13282080889507.20 819056092357.85 37 0.5 0.28 0.202010 2 2992033 4289000 36573190828642.10 618808984600.10 37 0.5 0.66 0.462010 3 2992033 4289000 7779443128030.27 849818780009.80 37 0.5 0.14 0.102010 4 2992033 4289000 4762779949552.74 1189318858754.24 37 0.5 0.09 0.06

Year Period WGWIDE SSB (T) Daily egg production (egg/m2) Survey area (m2) Batch fecundity (N/g) Sex ratio Spawning fraction (using WGWIDE SSB)2004 4 1929200 2330000000000 378359885790 107 0.5 0.022004 5 1929200 5250000000000 438544012912 184 0.5 0.032004 6 1929200 13170000000000 313753336232 353 0.5 0.042007 3 2299980 5845487034468 560323283712 302 0.5 0.022007 4 2299980 13594494162055 567756092358 557 0.5 0.022007 5 2299980 19439818706270 405461514599 530 0.5 0.032010 3 2157310 10188819291823 690972828346 197 0.5 0.052010 4 2157310 2027804921750 570738326823 358 0.5 0.012010 5 2157310 13626512893141 501268438534 386 0.5 0.03


6 Recommendations for the future survey design of the triennial mackerel and horse mackerel egg surveys

Based on the presentations and the calculation of the spawning fractions, the group decided to continue with the AEPM survey in 2013, but to try to carry out enhanced DEPM sampling for both mackerel and horse mackerel in the peak spawning periods. (For a full report on the discussion see Annex 3).

The main conclusions from the group were:

• Spawning fraction calculations give reasonable results. • The survey design doesn’t change in 2013, in order to continue the AEPM

time-series. WGWIDE needs at least 4 to 5 data points before a new time-series of a new method can be used in the assessment.

• The AEPM will be carried out during all survey periods. The extra DEPM adult sampling in a core area will only be carried out during the peak spawning period. For mackerel this will be period 3 and for horse mackerel period 5 during the 2013 survey.

• Try to do AEPM and DEPM estimates for comparisons based on the sam-ples from the 2013 survey.

The workshop recommends that:

1 ) Survey design doesn’t change in 2013 to be able to continue the AEPM time-series. Participants in a dedicated period will try to collect extra adult samples for investigation of estimation of DEPM adult parameters. First priority in the dedicated period is egg sampling coverage of the spawning area.

2 ) Creation of peak spawning areas based on previous WGMEGS spawning results in the perceived peak spawning period for collecting additional adult sampling for the estimation of DEPM adult parameters.

3 ) Attempt a comparison between AEPM and DEPM based on the 2013 sur-vey results.

4 ) Opportunistic collection of adult samples during other dedicated surveys in 2013 (Blue whiting acoustic surveys, Q1 IBTS, southern acoustic sur-veys) and commercial vessels to be analysed for DEPM adult parameters.

5 ) Review existing fecundity samples collected in previous surveys for DEPM adult parameters.

Core sampling areas within the respective perceived peak spawning periods will form the enhanced DEPM sampling area within which the programme of additional adult sampling for adult DEPM parameters will take place (Figures 6.1 and 6.2).


Figure 6.1. Core sampling areas and enhanced DEPM sampling area during peak spawning – period 3 - for mackerel in the western and southern areas for 2013.


Figure 6.2. Core sampling areas and enhanced DEPM sampling area during peak spawning – period 5 — for western horse mackerel for 2013.


7 References

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Alheit, J. 1993. Use of the Daily Egg Production Method for estimating Biomass to cupleoid fishes: A review and Evaluation. Bulletin of Marine Science, Vol 53(2):750–767.

Bernal, M., Somarakis, S., Witthames, P.R., Damme, C. J. G. van, Uriarte, A., Lo, N. C. H., and Dickey-Collas, M. 2012. Egg production methods in marine fisheries; an introduction. Fish.Res.117–118; 1–5.

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Damme, C. J. G. van, Dickey-Collas, M., Thorsen, A., Fonn, M., Alvarez, P., Garabana, D., O Hea, B., Perez, J. R., and Witthames, P. R. in prep. Fecundity regulation in income breed-ing horse mackerel.

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Ganias, K. 2012. Thirty years of using the postovulatory follicles method: overview, problems and alternatives. Fish. Res., 117–118, 63–74.

Goncalves, 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 J. Mar. Sci., 66: 617–622.

Gordo, L. S., Costa, A., Abaunza, P., Lucio, P., Eltink, A. T. G. W., and Figueiredo, I. 2008. De-terminate vs. indeterminate fecundity in horse mackerel. Fisheries Research, 89: 181–185.

Greer Walker, M., Witthames, P. R., and Bautista de los Santos, I. 1994. Is the fecundity of the Atlantic mackerel (Scomber scombrus: Scombridae) determinate? Sarsia, 79: 13–26.

Hunter, J. R., and Goldberg, S. R. 1980. Spawning incidence and batch fecundity in northern anchovy, Engraulis mordax. Fish. Bull. vol. 77 no.3.

Hunter J., and Lo, N. C. H. 1997. The daily egg production method of biomass estimation: some problems and potential improvements. In “Improvements of the Daily Egg Production Method techniques”. Ed. by L. Motos. Ozeanografika nº 2, pp 41–69.

Hunter, J. R., Lo, N. C. H., and Leong, R. J. H. 1985. Batch Fecundity in Multiple Spawning Fishes. In An Egg Production Method for..... . Ed by R. Lasker. US Dep. Commer., NOAA Techn. Rep. 36, p.67–78.

Hunter, J. R., and Macewicz, B. J. 1985. Measurement of Spawning Frequency in Multiple Spawning Fishes. In An Egg Production Method for...., Ed by R. Lasker. p. 79 93, US Dep. commer., NOAA Techn. Rep. 36.

ICES. 2005. Report of the Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS). ICES CM 2005/G:09.

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ICES. 2011. Report of the Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS). ICES CM 2011/SSGESST:07.

Karlou-Riga, C., and Economidis, P. S. 1997. Spawning frequency and batch fecundity of horse mackerel, Trachurus trachurus (L.), in the Saronikos Gulf (Greece). J. Appl. Ichtyol., 13: 97–104.


Kjesbu, O. S. 1989. The spawning activity of cod, Gadus morhua L. Journal of Fish Biology 34, 195–206.

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Macewicz, B., and Hunter, J. R. 1993. Spawning frequency and batch fecundity of jack mack-erel, Trachurus symmetricus, off California during 1991. CalCOFI Report, 34: 112–121.

Ndjaula, H. O. N., Hansen, T., Kruger-Johnsen, M., and Kjesbu, O. S. 2009. Oocyte develop-ment in captive Atlantic horse mackerel Trachurus trachurus. ICES J. Mar. Sci., 66: 623–630.

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Portilla, E., McKenzie, E., Beare, D., Reid, D. 2007. Estimating natural interstage egg mortality of Atlantic Mackerel (Scomber scombrus) and horse mackerel (Trachurus trachurus) in the Northeast Atlantic using a stochastic model. Can. J. Fish. Aquat. Sci., 64: 1656–1668.

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Yamada, T., Aoki, I., and Mitani, I. 1998. Spawning time, spawning frequency and fecundity of Japanese chub mackerel, Scomber japonicus in the waters around the Izu Islands, Japan. Fisheries Research 38, 83–89. doi:10.1016/S0165-7836(98)00113-1.


Annex 1: List of participants

Name Address Telephone/Fax E-mail

Cindy van Damme Chair

Wageningen IMARES PO Box 68 1970 AB Ĳmuiden Netherlands

[email protected]

Finlay Burns Chair

Marine Scotland Science Marine Laboratory 375 Victoria Road PO Box 101 Aberdeen AB11 9DB UK

+44 1 224 295 376

[email protected]

Paula Álvarez AZTI-Tecnalia Herrera Kaia Portualde z/g 20110 Pasaia (Gipuzkoa) Spain

+34 943 004800 +34 943 004801

[email protected]

Maria Manuel Angélico

INRB - IPIMAR Avenida de Brasilia 1449-006 Lisbon Portugal

[email protected]

Thomas Brunel Wageningen IMARES PO Box 68 1970 AB Ĳmuiden Netherlands

+31 317 487 161

[email protected]

Høgni Debes Faroe Marine Research Institute Nóatún 1 PO Box 3051 110 Tórshavn Faroe Islands

[email protected]

Björn Gunnarsson

Institute of Marine Research, Reijkjavik Iceland

[email protected]

Merete Fonn Institute of Marine Research Nordnes PO Box 1870 5817 Bergen Norway

[email protected]

Patricia Gonçalves

INRB - IPIMAR Avenida de Brasilia 1449-006 Lisbon Portugal

[email protected]

Ruben Hoek Wageningen IMARES PO Box 68 1970 AB Ĳmuiden Netherlands

[email protected]

mailto:[email protected]



Selene Hoey Marine Institute Rinville Oranmore Co. Galway Ireland

[email protected]

Kathryn Hughes

National University of Ireland, Galway Martin Ryan Institute University Road Galway Ireland

+353 091 524411 extn 5883 +353 851310995 (mobile)

[email protected]

Svein A. Iversen Institute of Marine Research Nordnes PO Box 1870 5817 Bergen Norway

+47 55 23 84 07 mobile +47 90 19 65 99 +47 55 23 85 55

[email protected]

Matthias Kloppmann

Johann-Heinrich von Thünen-Institute, Federal Research Institute for Rural Areas, Forestry and Fisheries Institute for Sea Fisheries Palmaille 9 22767 Hamburg Germany

[email protected]

Steve Milligan Centre for Environment, Fisheries and Aquaculture Science (Cefas) Lowestoft Laboratory Pakefield Road Lowestoft Suffolk NR33 0HT UK

+44 1502 562244 +44 1502 513865

[email protected]

Brendan O'Hea Marine Institute Rinville Oranmore Co. Galway Ireland

+353 91 387 200 [email protected]

José Ramón Pérez

Instituto Español de Oceanografía Centro Oceanográfico de Vigo Cabo Estai - Canido PO Box 1552 36200 Vigo (Pontevedra) Spain

+34 986492111 [email protected]



Anders Thorsen Institute of Marine Research Nordnes PO Box 1870 5817 Bergen Norway

[email protected]

Jens Ulleweit Johann-Heinrich von Thünen-Institute, Federal Research Institute for Rural Areas, Forestry and Fisheries Institute for Sea Fisheries Palmaille 9 22767 Hamburg Germany

+49 40 3890 5217 +49 40 3890 5263

[email protected]

Andrés Uriarte AZTI-Tecnalia Herrera Kaia Portualde z/g 20110 Pasaia (Gipuzkoa) Spain

+34 943004816 / 800

[email protected]


Annex 2: Agenda

Monday 16th April

9:00 Start; General announcements; Introduction; etc.

9:30 Introduction to layout of the workshop

10:00 Coffee break

10:15 Presentation: Spawning strategies mackerel and horse mackerel (Cindy)

11:00 Presentation: Mackerel fecundity and batch fecundity (Anders)

11:45 Presentation: Horse mackerel fecundity and batch fecundity (Cindy)

12:30 Lunch

13:00 Presentation: Mackerel and horse mackerel annual and daily egg productions (Finlay)

13:45 Presentation: DEPM and egg parameters and adult parameters data collection (Andres)

14:00 Presentation: DEPM SSB estimation (Maria, Patricia)

15:00 Tea break

15:15 Presentation: Characterizing the spawning habitat of Northeast Atlantic mack-erel (Thomas)

15:30 AEPM and DEPM (including variance) estimation of mackerel and horse mack-erel based on the historical data (presented in the earlier presentations)

17:30 End of the day

Tuesday 17th April

9:00 Presentation: Results of the AEPM and DEPM estimations (from Monday after-noon)

10:00 Coffee break

10:15 Discussion on survey method AEPM, DEPM (or other possibilities) for the fu-ture mackerel and horse mackerel egg surveys

12:30 Lunch

13:00 Possible effects of change in survey methods for the assessment (presentation? from WGWIDE participant(s))

15:00 Tea break

15:15 Discussion and deciding on future method for mackerel and horse mackerel egg surveys

17:30 End of workshop


Annex 3: Notes from the discussion on survey design

Discussion on the design of the 2013 mackerel and horse mackerel egg survey:

• Can’t change the survey design: WGWIDE 12 years (at least 4 to 5 data points) needed to be able to do an assessment.

• Collect the samples for batch fecundity: pipette samples can be used for es-timating batch fecundity. Also sample hydrated females. Pipette samples should be increased from 25 to 100 µl.

• Not a full DEPM study, but select one period both for batch fecundity and work up the samples for spawning fraction.

• Predict peak spawning to select the period were extra adult samples will be taken.

• Collect samples from stages 2–3–4–5–6 • Take an adult sample each day or each transect? • Set a quota of adult hauls for a geographic area with high spawning. • Spawning fraction is the biggest problem. • Different spawning fraction estimations in different areas? Split up in more

than one selected areas based on the previous surveys. • Long transects to the west could be problematic for intensive adult sam-

pling, even in period 2. • Plan for extra adult sampling, but priority is to get the spawning area cov-

erage, extra adult sampling will have a lower priority. • Collecting samples from other surveys or commercial vessel: Late March

Southern area acoustic survey, blue whiting survey catches mackerel, IBTS survey bottom-trawl survey catches mackerel (late February-mid March). Spain, Portugal possible to have observers on the commercial vessel, Ger-many and Netherlands has observers, but problem could be taking for-maldehyde on board (small tubes could be OK).

• The number of extra adult samples does not need to be huge (some studies have only 50 for estimation of spawning fraction). The adult processing ef-fort in the lab will increase.

• Sampling and logistics not problematic. The extra analyses of the spawn-ing markers will require 30 fish from each haul for estimation of spawning fraction.

• Split work between institutes, instead of all doing all analysis, one institute doing fecundity the other spawning fraction.

• In the survey year fecundity and atresia needed for WGWIDE.

Conclusions

• Spawning fraction calculations are reasonable. • Survey design doesn’t change. • Extra adult sampling in a core area in one period. • Try to do AEPM and DEPM estimates for comparisons


Recommendations

1 ) Survey design doesn’t change in 2013 to be able to continue the AEPM time-series. Participants in a dedicated period will try to collect extra adult samples for investigation of estimation of DEPM adult parameters. First priority in the dedicated period is egg sampling coverage of the spawning area.

2 ) Creation of a peak spawning areas based on previous WGMEGS spawning results in the perceived peak spawning period for collection additional adult sampling for the estimation of DEPM adult parameters.

3 ) Attempt a comparison between AEPM and DEPM based on the 2013 sur-vey results.

4 ) Opportunistic collection of adult samples during other dedicated surveys in 2013 (Blue whiting acoustic surveys, Q1 IBTS, southern acoustic sur-veys) and commercial vessels to be analysed for DEPM adult parameters.

5 ) Review existing fecundity samples collected in previous surveys for DEPM adult parameters.


Annex 4: Recommendations

RECOMMENDATION ADRESSED TO

1. The survey design doesn’t change in 2013 to be able to continue the AEPM time-series. Participants in a dedicated period will try to collect extra adult samples for investigation of estimation of DEPM adult parameters. First priority in the dedicated period is egg sampling coverage of the spawning area.

WGMEGS, SGSIPS, WGWIDE

2. Creation of a peak spawning areas based on previous WGMEGS spawning results in the perceived peak spawning period for collection additional adult sampling for the estimation of DEPM adult parameters.

WGMEGS

3. Attempt a comparison between AEPM and DEPM based on the 2013 survey results.

WGMEGS, SGSIPS

4. Opportunistic collection of adult samples during other dedicated surveys in 2013 (Blue whiting acoustic surveys, Q1 IBTS, southern acoustic surveys) and commercial vessels to be analysed for DEPM adult parameters.

IBTSWG, WGNAPES, IEO, AZTI, WGMEGS participants, SGSIPS

5. Review existing fecundity samples collected in previous surveys for DEPM adult parameters.

WGMEGS participants, SGSIPS


Annex 5: Working documents

Working Document for ICES – Workshop on Survey Design and Mackerel and Horse Mackerel Spawning Strategy (WKMSPA), Galway, Ireland, 16–17 April 2012

Developments in the DEPM application of the horse mackerel Southern stock (ICES Division IXa)

Patrícia Gonçalves, Ana M. Costa, Maria M. Angélico

INRB/IPIMAR, Instituto de Investigação das Pescas e do Mar, Lisboa, Portugal

ABSTRACT

The DEPM was applied to the southern stock of horse mackerel since 2007. Since this first DEPM application, several biological aspects relating to the adult and egg phases have been investigated and have been improved. The main aims of this working document are to describe the adaptations and improvements performed in the DEPM approach applied to the southern stock of horse mackerel. Those improvements in-cluded: (i) changes in the survey design (sampling grid and gear used) used for sam-pling the entire spawning area; (ii) description of the morphology and development of the eggs of the species T. picturatus, a species that co-occurs in the same distribu-tion area and spawns at the same period as Trachurus trachurus (iii); increase in the number of samples used to estimate batch fecundity, using two spawning markers (hydrated oocytes and migratory nucleus stage oocytes; iv); study the daily synchro-nicity in horse mackerel in order to obtain the POFs duration for spawning fraction estimation.

Documents

Report of the Workshop on Survey Design and Mackerel and ... Reports/Expert... · the 2013 mackerel and horse mackerel egg survey. ... For indeterminate spawners it is not possible