A total of 10 384 tons of sardine (191 million fish) was estimated to be present in northwest and northern Spanish waters by the Spanish spring acoustic survey PELACUS0315, carried out
from 13th March to 16th April 2015. These values are virtually identical to those recorded in
2014, which shows a stable trend at the lower level of the time series.
Sardine distribution was wider than previous years, but the energy allocated to this species
was in general very low. Sardine was presented throughout the whole sampled area, but the
energy attributed to this species was in general very low. Higher sardine concentrations were
detected in Galicia and in the Vasque Country area. Most fish in the entire surveyed area were
assigned as belonging to the age 1 (29% of the abundance and 20% of the biomass), age 2
(28% of the abundance and 26% of the biomass) and age 3 (27% of the abundance and 29% of
the biomass) years classes.
By sub-area, IXa subdivision represents 21.1%, VIIIc West 0.3%, VIIIcEast-West 25.4% and
VIIIcEast- East 53.1% of the total abundance. Galicia populations (IXaN and VIIIcW subdivisions)
were dominated by age 1 fish whilst the Cantabrian area was mainly composed by older
individuals.
The distribution of sardine eggs indicates a coastal distribution, agreeing with that observed in
previous years. Sardine eggs showed a widespread distribution in the surveyed area, with
higher percentage of positive stations than in earlier years

Carrera-López, P. (Pablo)

Riveiro, I. (Isabel)

English

Carrera, P. (Pablo)

Repositorio Institucional Digital del IEO

Working document for the WGHANSA 24-29/06/2015, IPMA Lisboa, Portugal   PRELIMINARY RESULTS OF THE PELACUS0315 SURVEY: ESTIMATES OF SARDINE ABUNDANCE AND BIOMASS IN GALICIA AND CANTABRIAN WATERS  Isabel Riveiro & Pablo Carrera  1 Instituto Español de Oceanografía. Centro Oceanográfico de Vigo. PO Box 1552, Vigo, Spain.  Abstract  A total of 10 384 tons of sardine (191 million fish) was estimated to be present in northwest and northern Spanish waters by the Spanish spring acoustic survey PELACUS0315, carried out from 13th March to 16th April 2015. These values are virtually identical to those recorded in 2014, which shows a stable trend at the lower level of the time series. Sardine distribution was wider than previous years, but the energy allocated to this species was in general very low. Sardine was presented throughout the whole sampled area, but the energy attributed to this species was in general very low. Higher sardine concentrations were detected in Galicia and in the Vasque Country area. Most fish in the entire surveyed area were assigned as belonging to the age 1 (29% of the abundance and 20% of the biomass), age 2 (28% of the abundance and 26% of the biomass) and age 3 (27% of the abundance and 29% of the biomass) years classes. By sub-area, IXa subdivision represents 21.1%, VIIIc West 0.3%, VIIIcEast-West 25.4% and VIIIcEast- East 53.1% of the total abundance. Galicia populations (IXaN and VIIIcW subdivisions) were dominated by age 1 fish whilst the Cantabrian area was mainly composed by older individuals. The distribution of sardine eggs indicates a coastal distribution, agreeing with that observed in previous years. Sardine eggs showed a widespread distribution in the surveyed area, with higher percentage of positive stations than in earlier years.   Introduction  PELACUS 0315 is the latest of the long-time series (started in 1984) of spring acoustic surveys carried out by the Instituto Español de Oceanografía to monitor pelagic fishery resources in the north and northwest shelf of the Iberian Peninsula (ICES divisions IXa – South Galicia and VIIIc – Cantabrian Sea). Since 2013, the survey is carried out in the R/V Miguel Oliver.   We present the results on the distribution of egg and adult fish together with the estimated values of adult fish abundance and biomass obtained in the survey, for sardine and anchovy. We also compare the new values with those obtained in previous years.  Material and methods  The methodology was similar to that of the previous surveys.  Survey was carried out from 13th March to 15th April in the R/V Miguel Oliver and sampling design consisted in a grid with systematic parallel transects equally separated by 8 nm and perpendicular to the coastline (Figure 1) with random start, covering the continental shelf from 30 to 1000 m depth and from Portuguese-Spanish border to the Spanish -French one. Acoustic records were obtained during day time together with egg samples from a Continuous Underwater Fish Egg Sampler (CUFES), with an internal water intake located at 5 m depth. CTD casts and plankton and water samples were taken during night time over the same grid in alternating transects. Besides, pelagic trawl hauls were performed in an opportunistic way to provide ground-truthing for acoustic data.   Acoustic equipment consisted in a Simrad EK-60 scientific echosounder (18, 38, 120 and 200 KHz). The elementary distance sampling unit (EDSU) was fixed at 1 nm. Acoustic data were obtained only during daytime at a survey speed of 10 knots. Data were stored in raw format and post-processed using SonarData Echoview software (Myriax Ltd.). The integration values are expressed as nautical area scattering coefficient (NASC) units or sA values (m2  nm -2) (MacLennan et al., 2002).    Figure 1.  2015 Survey track  Two different pelagic gears were used, depending of the depth of the area. Hauls were mainly performed in depths between 47 m and 800 m, with an average duration of 27 minutes (and usually with a minimum duration of 20 minutes).  A two steps method was used to assess the pelagic fish community. First, hauls were classified on account the following criteria: weather condition, gear performance and fish behaviour in front of the trawl derived from the analysis of the net sonar (Simrad FS20/25), catch composition in number and length distribution. Each haul was categorised and ranked as follows:   0 1 2 3 Gear performance Fish behaviour Crash Bad geometry Fish escaping Bad geometry No escaping God geometry No escaping Weather conditions Swell >4 m height Wind >30 knots Swell:  2 -4 m Wind: 30-20 knots Swell: 1-2m Wind 20-10 knots Swell <1 m Wind < 10 knots Fish number total fish caught <100 Main species >100 Second species <25 Main species > 100 Second species< 50 Main species > 100 Second species > 50 Fish length distribution No bell shape  Main species bell shape  Main species bell shape Seconds: almost bell shape Main species bell shape Seconds: bell shape  These criteria were used as a proxy for ground-truthing. Hauls considered as the best representation of the fish community (i.e. those with higher overall rank on account the four criteria) were used to allocate the backscattering energy got on similar echotraces located in the same area.  Once backscattering energy was allocated, spatial distribution for each species was analysed on account both the NASC values and the length frequency distributions (LFD). These were obtained for all the fish species in the trawl (either from the total catch or from a representative random sample of 100-200 fish). For the purpose of acoustic assessment, only those size distributions which were based on a minimum of 30 individuals and which presented a bell shape (normal) distribution were considered. Random subsamples were taken when the total fish caught was higher than 100 specimens. Differences in probability density functions (PDF) were tested using Kolmogorov-Smirnoff (K-S) test. PDF distributions without significant differences were joined, giving a homogenous PDF stratum. Spatial structure and surface (square nautical miles) for each stratum were calculated using EVA and SURFER packages. Fish abundance was calculated with the 38 kHz frequency as recommended at the PGAAM (ICES 2002). Nevertheless, echograms from 18 and 120 kHz frequencies were used to visually discriminate between fish and other scatter-producing objects such as plankton or bubbles, and to distinguish different fish according to the strength of their echo. Also these frequencies have been used to create a mask allowing a better discrimination among fish species and plankton. The threshold used to scrutinize the echograms was –70 dB. Backscattered energy (sA) was allocated to fish species according to the proportions found at the fishing stations (Nakken and Dommasnes, 1975). For this purpose, the following TS values were used: sardine and anchovy, -72.6 dB (b20); horse mackerels (Trachurus trachurus, T. picturatus and T. mediterraneus), –68.7 dB, bogue (Boops boops), –67 dB, chub mackerel (Scomber colias), -68.7, mackerel (Scomber scombrus), –84.9 dB and blue whiting (Micromesistius poutassou), -67.5 dB. When possible, direct allocation was also used. Biomass estimation was done on each strata (polygon) using the arithmetic mean of the backscattering energy (NASC, sA) attributed to each fish species and the surface expressed in square nautical miles.   Besides each fish was measured and weighed to obtain a length-weight relationship. Otoliths were also extracted from anchovy, sardine, horse mackerel, blue whiting, chub mackerel, Mediterranean horse mackerel and mackerel in order to estimate age and to obtain the age-length key (ALK) for each species for each area.   Results  A total of 2315 nautical miles were steamed, 1190 corresponding to the survey track.  In the area surveyed, a total of 66 fishing stations were performed (Figure 2).   Figure 2: PELACUS0315 Fish proportion (abundance) at each fishing station  On the other hand, 355 CUFES stations, comprising 3 nautical miles each were taken, as shown in Figure 3. Due to problems during installation of CUFES, the first days of the survey, corresponding to the southern area of Galicia (IXaN, excluding Rias Baixas), were not sampled.   Figure 3. PELACUS0315 CUFES stations.   Results Acoustic Sardine distribution and assessment  Sardine was presented throughout the whole sampled area, but the energy attributed to this species was in general very low. Higher sardine concentrations were detected in Galicia (IXa North subdivision) and in the Vasque Country area (Figure 4).     Figure 4. Sardine: spatial distribution of energy allocated to sardine during 2013-2015 PELACUS surveys. Polygons are drawn to encompass the observed echoes, and polygon colour indicates sardine density in nm2 within each polygon.  According to the behaviour observed over the last years, sardine seemed to occur dispersed and not in dense schools, mixed with other species, mainly mackerel (which represented more than 70 percent of the biomass in the PELACUS catches) and horse mackerel.  The total sardine abundance in PELACUS0315 for the IXa and VIIIc subdivisions was estimated at 191×106 individuals corresponding to 10384 tons (200x106 individuals and 10815 tons for the whole area surveyed, including VIIIb ICES subdivision) (Table 1).    2013 2014 2015 Table 1. Sardine acoustic assessment   Sardine ranged in length from 13 to 26 cm, with a mode at 18 cm (Figure 5) which corresponds to quite large fish. Most fish in the entire surveyed area were assigned as belonging to the age 1 (29% of the abundance and 20% of the biomass), age 2 (28% of the abundance and 26% of the biomass) and age 3 (27% of the abundance and 29% of the biomass) years classes (Table 2, Figure 4).   By sub-area, IXa subdivision represents 21.1%, VIIIc West 0.3%, VIIIcEast-West 25.4% and VIIIcEast- East 53.1% of the total abundance. Galicia populations (IXaN and VIIIcW subdivisions) were dominated by age 1 fish whilst the Cantabrian area was mainly composed by older individuals (age 2 and 3) (Figure 5).    Figure 4. Sardine: fish length distribution in biomass and abundance during the PELACUS0315 survey (including VIIIb subdivision).      Area No Mean Area PDFRias Baixas 51 33.47 149 P08-P09-P11 S01 25 921 6Muros 29 43.96 122 S02 16 1283 10Total 80 37.27 271 40 2204 8Costa da Morte 8 0.99 61 P32-P33-P34 S02 0 11 028 0.26 177 P37 S03 0 8 0Total 36 0.42 239 1 19 0152 7.26 1174 P32-P33-P34 S02 27 1966 2Central  54 11.05 409 17 952 223 6.23 172 4 219 1Total 229 8.05 1754 48 3138 2Laredo 20 0.52 159 P43 S04 0 18 0Euskadi_off 14 17.57 102 P46-P49-P52 S05 5 443 417 186.82 123 96 4561 37Total 51 67.30 383 101 5023 13Euskadi 16 16.93 128 P46-P49-P52 S05 9 431 3Total 16 16.93 128 9 431 380 37 271 40 2204 8316 17 2376 150 8161 316 17 128 9 431 3412 20.74 2775 199 10795 4Zone Fishing st. No (million fish) Biomass (tonnes) Density (Tn/nmi-2)IXaVIIIc-WArtabroVIIIc-Ew WestEast  VIIIc-EeEuskadi_coastVIIIbTotal  IXaTotal VIIIcTotal VIIIbTotal Spain1010.5 1111.5 1212.5 1313.5 1414.5 1515.5 1616.5 1717.5 1818.5 1919.5 2020.5 2121.5 2222.5 2323.5 2424.5 2525.5 2626.5 27050001000015000200002500030000350000500100015002000250030003500NumberBiomassLength group (0.5 cm)Numbers (10^3)Biomass(mt)   Table  2. Sardine abundance in number (thousand fish) and biomass (tons) by age group and ICES sub-area in PELACUS0315.     Figure 5. Sardine: relative abundance at age in each sub-area estimated in the PELACUS0315. The pie chart shows the contribution of each sub-area and each age group to the total stock numbers.      AREA VIIIcEAGE 1 2 3 4 5 6 7 8 9 10 TOTALBiomass (Tonnes) 1384 2435 2602 597 376 291 344 106 25 8161% Biomass 17.0 29.8 31.9 7.3 4.6 3.6 4.2 1.3 0.3 100Abundance (N in '000) 34150 48892 46882 7856 4200 2966 3596 1022 219 149784% Abundance 22.8 32.6 31.3 5.2 2.8 2.0 2.4 0.7 0.1 100Medium Weight (gr) 40.5 49.8 55.5 76.0 89.6 98.2 95.7 103.7 113.2 80.2Medium Length (cm) 17.6 18.9 19.5 21.7 23.0 23.7 23.5 24.2 24.9 21.9AREA VIIIcWAGE 1 2 3 4 5 6 7 8 9 10 TOTALBiomass (Tonnes) 15 3 1 0.1 19% Biomass 78.7 13.9 6.9 0.4 100Abundance (N in '000) 443 61 28 1 533% Abundance 83.0 11.5 5.2 0.2 100Medium Weight (gr) 34.6 44.1 48.5 61.4 23.6Medium Length (cm) 16.7 18.1 18.7 20.3 9.2AREA IXaNAGE 1 2 3 4 5 6 7 8 9 10 TOTALBiomass (Tonnes) 721 225 366 297 238 145 150 51 12 2204% Biomass 32.7 10.2 16.6 13.5 10.8 6.6 6.8 2.3 0.5 100Abundance (N in '000) 21084 4150 5092 3523 2685 1546 1579 509 112 40279% Abundance 52.3 10.3 12.6 8.7 6.7 3.8 3.9 1.3 0.3 100Medium Weight (gr) 34.2 54.2 71.9 84.4 88.6 93.7 94.8 100.0 104.1 71.2Medium Length (cm) 16.7 19.3 21.3 22.5 22.9 23.4 23.4 23.9 24.2 21.0TOTAL SPAINAGE 1 2 3 4 5 6 7 8 9 10 TOTALBiomass (Tonnes) 2120 2663 2970 894 614 436 494 157 36 10384% Biomass 20.4 25.6 28.6 8.6 5.9 4.2 4.8 1.5 0.4 100Abundance (N in '000) 55677 53103 52002 11380 6885 4512 5176 1532 331 190596% Abundance 29.2 27.9 27.3 6.0 3.6 2.4 2.7 0.8 0.2 100Medium Weight (gr) 38.1 50.1 57.1 78.6 89.2 96.6 95.4 102.4 110.1 71.8Medium Length (cm) 17.2 18.9 19.7 22.0 23.0 23.6 23.5 24.1 24.6 19.7PELACUS0315 00.20.40.60.811 2 3 4 5 6+00.20.40.60.811 2 3 4 5 6+00.20.40.60.811 2 3 4 5 6+00.20.40.60.811 2 3 4 5 6+123456+IXa-NVIIIc-WVIIIc-EwVIIIc-EeThe distribution of sardine eggs (obtained from the analysis of 355 CUFES stations) indicates a coastal distribution, agreeing with that observed in previous years (Figure 6). Total number of sardine eggs detected in Spanish waters was 7588, which represents an important increase from the 2014 value (4214 in 358 CUFES stations). Sardine eggs showed a widespread distribution in the surveyed area, with higher percentage of positive stations than in previous years (45% in 2015, 33% in 2014, 28% in 2013).    Figure 6. Sardine: distribution of sardine eggs (CUFES samples) in 2013-2015 PELACUS surveys. Blue circles indicate positive stations with diameter proportional to egg density.    2013 2015 2014 Acknowledgements  We would like to thank all the participants and crew of the PELACUS surveys.  References  Anon., 2006. Report of the Working Group on the Assessment of Mackerel, Horse Mackerel, Sardine, and Anchovy. ICES CM 2006/ ACFM: XX.  Carrera, P. and Porteiro, C. 2003. Stock dynamics of the Iberian sardine (Sardina pilchardus, W.) and its implication on the fishery off Galicia (NW Spain). Sci. Mar. 67, 245-258.  Foote, K.G., Knudsen, H.P., Vestnes, G., MacLennan, D.N. and Simmonds, E.J. 1987. Calibration of acoustic instruments for fish density estimation:  a practical guide. ICES Coop. Res. Rep. 144, 57 pp.  MacLennan, D.N., Fernándes, P.G. and Dalen, J. 2002. A consistent approach to definitions and symbols in fisheries acoustics. ICES J. Mar. Sci. 59, 365-9.   Marques, V., Silva, A., Angélico, M. M., Dominguez, R. and Soares, E. 2010. Sardine acoustic survey carried out in April 2010 off the Portuguese Continental Waters and Gulf of Cadiz, onboard RV “Noruega”. WD presented at the WG on Anchovy and Sardine, Lisbon, 24-28 June 2010, 10 pp.    

Preliminary results of the PELACUS0315 survey: estimates of sardine abundance and biomass

Riveiro, Isabel

Carrera, Pablo

Digital.CSIC

http://www.repositorio.ieo.es/e-ieo/bitstream/10508/9452/1/WD%20PELACUS0315%20sardine.pdf

Preliminary results of the PELACUS0315 survey: estimates of sardine abundance and biomass

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