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31 International Council for the C.M. 1985/H:~/Ref B Exploration of the Sea Pelagic Fish Committe

ACOUSTIC ABUNDANCE ESTIMATION OF MACKEREL, PILCHARD IN WATERS. APRIL 1984.

by

1 x. Pastor ) and A. Delgado de Molina2) , 1) Instituto Espanol de Oceanografia Centro Costero de Baleares - Muelle de Pelaires, s/n 07015 Pal~a de Mallorca,

2) Instituto Espanol de Oceanografia Centro Costero de Canarias P.O. Box 1373 38080 Santa Cruz de Tenerife, Spain

ABSTRACT

, e Results of the acoustic survey "Canarias AI 484" are reported in this paper. This survey was carried out on board the research vessel "Cornide de Saavedra" in April 1984 in the waters off Canary Islands. The ~ain objective of the sur­ vey was to estimate the abundance by year class for mackerel (Scomber japonicus), and p~}Chard (Sardina pilchardus). Abundance by length class for bogue (Boops boops) was also estimated. Canary Islands are of volcani~ origin, and there is not continental shelf aroundthem. Therefore, the surveyed area covered was the first five miles around each island. Total biomass estimate for small pelagic species was 73.000 tons, of wich 38.000 tons correspond to mackerei, 29.000 tons to bogue and 6.000 tons to pilchard. The areas of highest abundance were found around the islands of Fuerte'lentura and , ant those of lowest abundance were around the islands of Hierro and La Palma.

I Ir\.' b'

--_.--....._._-- 2

RESUHE

Les resultats de la campagne acoustique "Canarias AI 484" sont presentes dans ce papier. Cette campagne a ete realisee au bord du B/R "Cornide de Saavedra" a april du 1984 dans les eaux des Iles Canar~5 Les principaux objectifs de cette campagne on ete obtenir l'estimation de llaboundance par classes dlage pour ma­ quereaux et sardine. Llaboundance par classe de taille pour bogue ha ete aussi estimee. L'aire couverte.ha ete les cine milles au large de la c6te de les iles on il n'y a que du talud insulaire. La biomase total estimee a ete pour les petits poissons pelagiques 73.000 tons, dans les quelles 38.000 tons sont de maqueraux, 29.000 tons bogue et 6.000 tons sardine. Les aires du major aboundanee ont ete ren- ~ eontres autour des iles et Lanzarote, et les d'aboundance mineure autour des iles Hierro et La Palma.

INTRODUCTION

The resources of small pelagic species of the CanaryIslands are mainly formed.by populations of mackerel, horse mackerel, pilchard, bogue and anchovy. These spe- eies constitute the second fishing resource of major industrial importance in the islands. They are exploited by a loca~ fleet of small purseiners with the help of small boats with artificial light.

~. The annual catches of these small pelagic species are approximately 5.000 tons, of wich 3.000 are caught in the western islands (the provinee of Sta. Cruz de Tenerife) and the remainder in the eastern islands (province of Las Palmas).

The tunna fishery is the main fishing resource of Canary Islands. The devel~p­ ment of this fishery is bound to the availability of the coastal pelagic species, because the live beat used in this activity is basically formed by mackerel and pilchard. Of these speci~ the mackerel constitutes approximately 60 % of the total catches.

From the biological point of view, these species have been studied with certain regularity (OELGADO OE MOLINA et al., 1983), and some pr~liminary experiments of acoustic evaluations have been carried out (BRAVO OE LAGUNA, personal eommunica­ tion) and (ANON, 1984). 3

.. During the spring of 1984 a survey was carried out on board R/V "Cornide de Saa­ vedra" ·.... i th the aim of obtaining an acoustic estimate of the biomass and distri':' bution of those resources.

The cruise was carried out during the period between 16th and 26th of April. The survey tracks run by the vessel covered the area within the first five miles nearest to the coast, with the exception of the'half mile closest to the coast, due to safety reasons during navigation. The shoals near the archipielago (Concepci6n, el Banquete and Amanay) were also covered.

MATERIAL AND METHODS

Figures 1, 2 and 3 show the area covered by the "Cornide de Saavedra" during the cruise, the survey grid and tge pelagic fishing stations.

The Canary Islands, of volcanic origin, practically lack continental shelf, • and at a short distance from the coast the depth reaches some hundred metres. For this reason, the usual limit of the isobats of 200 of 500 m. was not used in this survey. In its place, an area of five miles·around each one of the is­ lands was stablished as the survey area; where it is foreseeable that most of the coastal pelagic resources are concentrated. This hypothesis was confirmed, in general, during the courses navigated between the islands.

125 survey tracks were established in a zig-zag grid. The vertices of the tracks were 10 nautical miles apart of each other. The most interna! points of the tracks were p1aced as near of the coast as possible for the vessels size, at a distance which ranged between 0.1 and 0.5 miles. Despite this, the first half mile area around each island must be,considered as poorly covered. The area surveyed was of 3.643 nm2 •

The acoustic equipment used during the survey was formed by an E~ 400 SIMRAD - - echosounder of 38 kHz and a QD digital integrator~he settings of the instru------ments during the cruise are shown in table I. Integration values were recorded at the end of each mile. The number of miles navigated in the surveyed area was 1.024. The value of the coverage index, N/V-S- = 17.0 is considered accep- 4

table, and minimizes the errors wich can be made with respect to the estimation of the indexes of relative abundance (AGLEN, 1983).

The fishing stations were carried out with a pe1agic gear of 10 m. of vertical opening and at a towing speed of 3 or 4 knots. Fishing stations were used for echoes identification and biological sampling. They were carried out whenever fish concentrationes appeared. Table II shows the characteristics and the re­ sults of the fishing stations.

Prior to the start of the survey, the acoustic instruments were calibrated (( I]., by means of an standard target (coppersphere of 60 cm 0) (FOOTE, 1981). Results .=- I. ' of this calibration are shown in anexe I.

For the biomass estimation of the surveyed area, this was divided in 9 subareas, corresponding to each one of the seven major islands of the archipielago and_to the shoals of Amanay and el Banquete, in the south of Fuerteventura. The shoal of La Concepci6n, situated 55 miles north of Lanzarote, was not considered. Despite it having been surveyed, it did not provide any integration value copres­ ponding to small pelagic fish.

The transformation of the values of relative echointegration to tons of biomass corresponding to each one of the species considered- was carried out through the ~spec:ivefconversionfactors (9)~ The procedure used to calculate these factors is shown in annexe II.

The absolute density per length class was estimated for the three species that made up almost the totality of the catch in the fishing stations: mackerel, bogue and pilchard. The following expression was used:

k .. M = __~~~J _ p (DALEN AND SMEDST~, 1979) ,ij k .. ~J 1: I: j i

2 where P represents the density (tons/mn )for the length class i of the species j, ij kij is its proportion in the catches of the fishing stations carried out in that subarea. M is the total of the integration va1ue attributed to pe1agic fish in that subarea. C.. is the value of C corresponding ~o length-i of species j. J.J

~"-_._------_ .. _-_. ------_.------5

The densities per length class and species calculated in this way for each subarea are converted into biomass using the expression:

B .. ~J =

where A is the su-face for each subarea, in square nautical miles.

In order to transform the biomass in tons per length class into number of indi­ viduals per length class, the corresponding length/weight relations were applied:

mackerel w= 0.0025 L3.46146 (OELGADO OE MOLINA et al. , 1983)

bogue w= 0.0071 L3.21690 (GIRAROIN, 1978)

pilchard w= 0.0065 L3.08539 (OELGADO DE MOLINA et al. , 1983)

Abundances per length class were converted into number of individuals per age class in the case of mackerel and pilchard. Length/age relation obta~ned from thesamples taken in the ~ishing stations during the survey was applied for mackerei. This relation is shown in table III.

The number of pilchard otholits per length class obtained during the survey did not permit the calculation of a reliable ~r~th/age relation for this spe­ cies and this cruise. Therefore, the length/age relation obtained by DELGADO OE MOLINA et al., (1983) from sampies carried out over the commercial catches of the local fishing fleet was used.

A length/age relation was not available for the Canary Islands bogue. For this ~ reason, the abundance in number of individuals per length class could not be converted into abundance in individuals per age class.

RESULTS

The total biomass estimated for small pelagic fishes during the survey was 73.00~ tons, of-wich approximately 53 % correspond to mackerel (Scomber japonicus),- 40 % to bogue (Boops boops) and 7 % to pilchard (Sardina pilchardus).

Figure 4 shows the general distribution of abundance in the archipielago. Figu­ res 1, 2 and 3 show the survey tracks, fishing-stations and abundance distribu­ tion for each of the three areas into wich the archipielago was divided for car-

--_._-,-,------6

tographic purposes.

In table IV the' following parameters are shown for each of the subareas: number • of sailed miles, average integrator value (mm), average density, area, estimated biomass and percentage of the global bicmass present in that subarea.

The total abundance in number of individuals per length class for each one of the three species assessed during the survey is shown in table V.

Tables VI and VII show the abundance in number of individuals per age class for mackerel and pilchard, and the percentage of each class with respect to the total evaluated. Average length per age class is also shown.

More than 60 % of the biomass estimated was found in the waters around the islands .~ of Fuerteventura and Lanzarote, including the shoals of EI Banquete and Bajo de Amanay, situated south of Fuerteventura. The largest integration values were spe­ cially recor?ed in the Strait of La Bocayna, between these two islands, and were confirmed by~ a pelagic fishing station, in wich a catch of 638 kg/hour was obtai­ ned, cor~esponding to a mixture of 64 % mackerei, 33 % bogue and 3 % pilchard. The poorest areas corresponded to the islands of Hierro y La Palma. . . It has been observed a tendency of the fish concentratiorsto be located mainly to the north and north-east of each of the islands, without hardly any exceptions being recorded. No hydrographie or meteorological observations were made during the survey, so this fact can not be put in relation with enviromental causes.

~ The catches obtained in the fishing stations have shown a great diversity in lengths for each of the species considered, without the length obviously bearing relation to the bathymetry nor to the distance from the coast where the pelagic trawling station was carried out. This observations is in accordance with that obtained from samplings of the commercial catc~es during the same period of the yera, wich show very variable average lengths be~~een ports for the different pelagic species (DELGADO DE MOLINA, personal communication) •

...... Figures 5 and 6 show the length distribution per species corresponding to each one of the fishing stations, and figure 7-- show the length distributions of the three species in the whole of the surveyed area. 7

- Althought the highest concentrations were found in the most coastal regions of the surveyed area, small pelagic fish concentrations were recorded in same • cases in areas relatively far from the coast. For example, in fishing station number 1, O-class pilchards were caught 5 miles from the coast, with a bottom depth above 1.000 m. and the pelagic trawling gear working at a depth of 20 m. from the surface. A similar situation has been described in Galician waters (PASTOR et al, 1985)

The biological sarnplings carried out' on 154 mackereis resulting frcm different catches shcwed that practical1y all the individuals langer than 20 cm. were fe­ males, and 82 % of them. were found in a post-spawning phase. The individuals of a shorter length were ~lasslfied, in genera~, as undetermined sex•

• DISCUSSION '-. The total abundance estimated for small pelagic species in the waters off Canary Islands during this survey was approximately 73.000 tons. This result is not different from the biomass estimated in 1976 during the cruise PELAGOS 76 (70.000 tons) (BRAVO DE LAGUNA, personal communication), using a different acoustic equipment and a conversion constant C calculated by the method of counting individualized fish on the echogram (PASTOR, personal communication). For both surveys, and also in the catches of the commercial fleet from the provin­ ces of Las Palmas and Santa Cruz de Tenerife, the highest proportion of pelagic species corresponds to mackerei, this being from 50 to 70.% of the total in every case.

These concordant results could show that the estimation obtained is quite consis­ tent. However, it must be borne in mi nd that evaluations by acoustic methods are usually conservative, due to the limitations wich the actual method involves: the

first five to ten metres nearest to'the1.surface and the waters next to the coast are uncover'ed, and possible alterations in the behavieur of the fish can occur in the upper waters in ,relation with the passing of the research vessel (OLSEN et al., 1982). In the particular case of the Canary Islands, the question cf the area nearest to the coast can have an important meaning. The experience of the local fishing fleet and the experimental survey carried out in January 1984 on board de R/V "Islas Canarias", CANARIAS 8401 (ANON., 1984), indicates that the presence of scho~ls of fish is frequent very near te the coast, where vessels ....---. '-" the size cf R/V "Cornide de Saavedra" (60 m. long, 3.5 m draft) cannot-- reach.

---,------_.__...._- ."-- -.•...__ ." ' 8

This would indicate that the evaluation carried out by this boat could be an underestimation of the coastal.pelagic resources present in the area.

Another possible source of error to consider must be the process of calculation of TS/kgr and C-values for the different species evaluated. The expression used for the TS corresponding to a specimen, wich gives origin to this calculation, originates from experiments carried out with herrings (Clupea sprattus) in the North Sea (ANON, 1983). It is possible that its application to other clupeiforms, such as the pilchard, does not create serious problems, but its utilization in species such as mackerel and the bogue, with unknown TS values, could produce important errors in the abundance estimation.

REFERENCES

AGLEN, A., 1983., Random errors of acoustic fish estimates in relation to the survey grid density applied. Symposium cn fisheries acoustics. Bergen, Nerway, 21-24 June 1982. Fao Fish Rep., (300): p.293.

ANON., 1982. Repert of the international acoustic survey on blue whiting in the Norwegian sea, july/august. ICES, C.M./H: 5.

ANON., 1983. Report of the 1983 planning group on ICES-coordinated herring and sprat acoustic surveys. ICES, C.M./H: 12.

ANON., 1984. Preliminary report of an acoustic fish survey experiment using newly developed sensor processor. Tenerife 17-25 january 1984. Inter­ nal document of the Centro Costero de Canarias of the Instituto Espa­ nol de Oceanograf!a.

DALEN, J.; SMEDSTAD, O.M. Investigations on demersal fish in the Barents sea in winter 1978. Counc. Meet. Int. Expler. Sea.

DELGADO DE MOLINA, A.; GARCIA SANTAMARIA, M.!.; RODRIGUEZ RODRIGUEZ, E; LOPEZ ABELLAN, J.L., 1983. Memoria deI Plan Regional de Evaluacion de Recur­ sos Pesqueros. Provincia de Santa Cruz de tenerife. Volumen 2. Pelagi­ cos costeros. Junta de Canarias. Instituto Espanol de Oceanografia. Centro Costero de Canarias 9

FOOTE, J.G.; KNUDSEN, H.P.; VESTNES, G.; BREDE, R.; NIELSEN, R.L., 1981. Impro­ • ved calibration of hydroacoustic equipment with copper spheres, ICES, C.M./B; 20.

GIRARDIN, M., 1978 Les Sparidae du Golfe du Lion. Ecologie et biogeographie. Univer­ site Scientifique Technique du Langedoc, Montpellier.

OLSEN, K; L0VIK, A; ANGELL, J; PETTERSEN, F., 1982. Observed fish reaction to a survey vessel with special reference to herring, cod and capelin. ICES Symposium on Fisheries Acoustics, Bergen, 1982 no. 21.

PASTOR, X.; PORTEIRO, C.; LAVIN, A., ],985. 'Acoustic abundanqe estimation of pilchard (Sardina pilchardus) in Galician and Cantabric waters. August 1983. ICES, ~ C.M./H: 52/Ref.B

STROMME, T.F. ; SAETE~SDAL, G.S., 1983. Survey of the offshore sub-surface communi- ty from Togo to Cameroon and the shelf from Equatorial guinea to the Con­ ga. Reports on surveys with the R/V !lDr. Fridtjof Nansen", Institute Mari- ne Research, Bergen, Norway.

ANNEX I

RESULTS OF CALIBRATION OF ACOUSTIC EQUIPMENT. (TENERIFE, APRIL 1984)

, 40 log R 20 log R e Constant (TVG) (2TL40, 2TL20) 99.21 64.50 dB Lass of transmission at depth r 27.13 27.13 dB Attenuation TVG at depth r 72.08 37.51 dB Selected gain - 20 - 20 dB Measured gain - 20 - 20 dB Power output HIGH HIGH Signal duration 1 1 ms Bandwidth 3.3 3.3 kHz Echo level 0.24 0.59 Vp-p 20 log U/2V2 -21.42 -13.61 dB

5L + VR 131.37 131.60 dB 10

Frecuency 38 kHz Water temperature 17 °C. Sound velocity (c) 1516 m/sec. Sphere depth (t) 29.5 msec. r = t x c / 2 = 22.36 m.

Sphere integration

Upper limit 20 m. Lower limit 24 m. Threshold 10 mV. Output in mm. (M) 323

ANNEX II

OBTENTION OF THE INSTRUMENTS CONSTANT C. 1 AND C-VALUES FOR MACKEREL, SARDINE AND BOGUE.

J.• Instruments constant C. 1

C· i- cr /M x ;2 x 'Y x 3.43 x 10° (ANON, 1982) where M = 323 mm TS 33.6 dB. sph. = - 3 cr (back scattering strength) = 10-3.36 = 4.36 x 10-4 = 0.• 436 x 10- 18 10 ~ (solid angle of the transducer) = 10- / = 0.0158

6 0.436 x 10-3 x 3.43 x 10 c. = = 0.5861 1 2 323 x 22.36 x 0.0158 2._Calculations of TS/Kg and C-value ror mackerel.

TS . h = 20 log.L - 71.2 (ANON; 1983) f 15

• w = 0.0025 L3.46146 (OELGADO OE MOLINA et al., 1983)

1000 TS/Kg = 20 log L- 71.2 + 10 log ----~~~~------­ 0.0025 L3.46146

TS/Kg = 20 log L- 71.2 + 30 - 10 log 0.0025 - 34.61 log L

TS/Kg = 14.61 log L- 15.18

TS/Kg 33.16 dB 17 = - 3.43 C = antilog 0.1 (TS - 20 log r - 10 log y + 30 - TS/Kg) (STROMME et al, 1983) ) M _ 3.43 ,.,. C = ----- antilog 0.1 (- 33.6 - 26.9 + 18 + 30 + 33.16) 323

C = 1.21155 C 0.071268 L 17 =

3. Ca1culations of TS/Kg and C-value for bogue.

W =0.0071 L 3.2169 (GIRARDIN, 1978)

TS/Kg = -12.16 log L- 19.71

TS/Kg 34.67 dB 17 =-

C 1.714318 C 0.100842 L 17 = =

4. Calculations of TS/Kg and C-value rar pilchard.

W = 0.0065 L3.08539 (OELGADO OE MOLINA et al, 1983)

TS/Kg = - 10.85 log L- 19.33

TS/Kg 32.68 dB 17 = -

C 1.08415 C 0.063773 L 17 = = 12

•

ECHOSOUNDER EK 400 - 38

Transducer 30 x 15 ceramic

Transmitter power' HIGH

TVG/Gain 20 log RIO dB

Pulse len~th 1.0 ms

Bandwidth 3.3 kHz·

INTEGRATOR DIGITAL QX + QD

Gain OdB x 100

Threshold 10 mV

Table I.- Settings of the acoustic instruments during the survey. ---_.- .... - -' . FISHING TIME STARTING POSITION CATClI.~g) • DATE DEP1_\';;) DOMINANT IIJEIGHT (Kg) • STATION. GMT LAT.N. LONG.W. TOTAL Kg/h SPECIES BOT1'(!)~' liEAR Kg/h %

1B/04 1 21.25 +1000 20 20°33.42 16°21.85 24.9 21.1 Scomber japonicus 18.1 66.5 Norte Tenerife Sardina pilchardus 5.3 19.4

19/04 2 23.30 350 15 28°21.15 16°35.42 NO CATCH Norte Tenerife

20/04 3 13.05 200 20 . 28°06.10 11°22.54 NO CATCH Oeste La Gomera

20/04 4 19.50 400 20 28°04.69 16°41.05 4.7 3.9 Liosacus cutaneus 2.0 42.5 Sur Tenerife Scomber japonicus 0.3 6.4 . .. Tunicados 2.1 51.1

21/04 5 23.45 50 25 21°57.00 14°31.24 105.5 105.5 Boops boops 88.9 84.3 EI Banquete Scomber japonicus 16.1 15.3 Suroeste Fuerteventura --- . 22/04 6 .03.29 BO 40 28°03.40 28°01.62 17.9 28.2 Scomber japonicus 22.0 71.9

EI Banquete '/ Boops boops 2.5 9.0 Suroeste Fuerteventura I Sardina pilchardus 0.1 0.4

24/04 7 11.50 . 60", 20 29°20.61 13°29.76 31.3 41.7 Scomber japonicus 23.7 56.9 La Graciosa Tunicados 11.9 43.0

24/04 8 13.10 100. 20 29°21.41 13°25.15 26.5 25.6 Sardina pilchardus 13.3 51.8 Alegranza Scomber japonicus 9.5 31.2 Tunicados 2.9 11.0

'24/04 9 20.5:1 50 20 28°49.00 13°49.04 340.7 638.8 Scomber japonicus 408.0 64.0 canal Lanzarote- Boops boops 211.3 33.1 Fuerteventura Sardina pilchardus 18.2 2.9

Table 11.- Characteristics and results of the pelagic fishing·stations. 14 •

• 0 I II III IV V VI n 2

9 100 3 10 100 2 11 100 4 12 100 6 13 100 . 15 14 100 9 15 71 29 6 16 57 43 8 17 100 ) 7 18 67 33 3 19 50 50 2 - 20 25 (50) 25 2 21 20 60 20 5 22 (12) 38 38 12 4 23 (20) 20 (40) 20 2 24 17 33 33 17 4 25 20 60 20 4 26 17 33 (33) (17) I 3 27 17 33 33 (17) 5 . 28 17 17 33 (33) 6 29 60 10 20 10 11 j 30 29 14 43 14 8 31 20 40 20 20 5 32 (20) 40 20 (20) 3 33 (25) 25 (25) (25) 1 34 25 (25) (25) (25) 1 35 (33) (33) (33) - 36 (50) (50) - 37 50 (50) 1 38 50 (50) 1

131

Tab1e III.- Length/age relation for mackerel obtained during the survey.

~- ~-~ I • •

. SUB A ß E AS

1 2 3 4 5 6 7 8 9 TOTAL PALMA HIERRO GOMERA TENERIFE G.CA~ARIA FUERTEV. LANZAROTE B.AMANAY BANQUETE. . SAILED MILES 88 129 66 212 171 158 162 . 9 29 1024 - INTEGRATION VALUE (M) 0.6 0.8 32.7 10.4 14.7 19.8 30.7 90.9 8.9 15.8

2 DENSITY (tons/nm) 0.6 0.8 34.9 11.1 17.5 24.6 38.0 112.7 11.1 20.0 ..... U1 2 AREA (nm ) 379.6 314.4 245.0 647.6 620.5 641.8 640.2 41.3 112.3 3642.7

BIOMASS (tons) 208.1 232.7 7309.9 6123.2 12337.5 15663.4 24145.3 5708.5 1520.3 73248.9

% 0.2 0.3 10.0 8.4 16.8 21.4 33.0 7.8 2.1 100 •

~. ,.

Table IV.- Abundan~e'of small pelagics per subarea and total. Number of sailed miles, 'average 'integration, density, area evaluated and percentage of the total biomass'correspondlng to each subarea are also shown.

/ ,------

16 •

• L BOGUE PILCHARD MACKEREL . 9 1 797 - 19 612 10 6 403 1 735 90 077 11 18 436 24 904 106 059 12 39 442 104 267 150 831 13 82 356 113 312 196 191 14 221 135 18 049 ,245 770 15 218 525 - 249 089 16 117611 - 164 337 17 25 485 1 147 141 944 18 7 231 2 130 18 650 ) 19 994 4 983 1 082 e 20 1· 072 6 616 771 21 687 3 629 684 22 - 2 033 1 869 23 - 1 990 24 - 1 310 25 208 663 26 4 984 27 635 28 1 097 29 1 302 30 1 143 I 31 402 32 232 33 215 34 - 35 - - 36 - 37 65 38 61

741 385 282 805 1 401 065

Table V.- Abundance in number of individuals (n x 10-3 ) per le~gth class for bogue, pilchard and mackerel estimated in-the .surveyed area• . ~ 17 •

• I I 0 I II III IV V VI , N 1 080 226 297 838 10 343 6 004 3 782 2 297 532

% 77.1 21.3 0.7 0.4 0.3 0.2 0.03

L(cm) 13.15 16.35 19.26 25.50 26.21 28.33 21.27 -

Table VI.- Distribution.of ~~€stimated abundance of. mackerelin:~umber of indivi- 3 •) duals (N x 10- ) per age class•

0 I II III

- N 262 267 10 463 7 938 2 138

% 92.7 3.7 2.8 0.8

L(cm) 12.46 18.93 20.46 21.21

Table VII.- Distribution of the estimated abundance of pilchard in number of 3 individuals (N x 10- ) per age class.

------_.- -._----- ..... _.._-.- .... __. • '.-+!S. .J...... L. -1 ....L._ -----.l"---r----l-.. ,,-+1_. --.l.. ...J..I...... :lt=-" .L- --L ~f_.. .- .-' · 1 I I ~ "

r'

,- I W-+------I-'.:--"""'---41-+\fi'--=:==-=--:lirt------f--29' l!1'-+------f'-1;---~L---:f-4;&1'--=--=--=-~:;Ai~------_+-Z!-( l ...) I .-._'i \, ..... --, I ,/ '" ) r------,,- . J I /' ,...... -.-.~.... I ./ ,.-_..J. ~ .'\ ~ • ... lIf I ".._.-- I ' () -.; ! A.-,. \ -.~ A \ ,'11"-':,·' ._./ ...... ' ,f .... \ 'j" '_.J ".....-"_...... if·-t'~1·- '. I J .::--.~ Jit ::: ' ,/ I /r I . , _~:V/A ,/. 2I-+--f--~[;;:.~f+"-"'-='"'2tJ_-----t------...L.I-·--=f..:..-.--+f·!!j~f-211~_J_-i-"_·-~,,!,::;-;:.../-· 4\-1·h·...i!o··....-o..:-~~..:··~·.;,..:·..'-----__t_------.!.'-·_--;,..:..:...f·__~r:.....+_l ' I I \.t,. f , I I • • '')_,r.....Aj I ! I : i \,-.__ ''''_~''''''''-'''' I ,. .... i .,_ ,/ f \. (.i J ,r ' \ ...... _.-._.-...... i) ,.' / ,. / ~ .j~/ / \ ./J I .. .. , « ;' j ;' ,i f ! 1;2) r .; :1 J(fiJ 1 ~ ,(' ( ,. i ) )/: I ~' ! ) ! I It • I .. 0< 25 ESCASO I ~ ~ 26-51) MEDIO f .f.{ " ESTACIONES OE PESt-' PELAGICA ; ,. :: I m5G-JJO AII....llANTE l! .. 100 MUY ABUNDANTE ...' ,. !! I• i " Z1'--+------,------,..-----+------;,..--.L..!-l--.,..------+-u'ZJ'-+------.-----.,..------f------r----'-'..:.I-L__...r-__ ---I.~-.-r fS- ~ Jt 14- .'. 1!>··..... 1:"- '" Fig. 1.- Survey grid, pe1agic fishing stations and relati~ abundance distribution for pelagics in area 1.

... ~ ...,.... _.- z·· ~I .,!1-. ...J'fL-'__-r-_'C.L' -,l(_.__--:=-'1" T.L' -t-w •• .( ..' 11', l' I w'+----_-L- .. • • / e·,· 2 .'~) ·r 2 I " ,., ...

,'-+------f------+-Zt"r-r------f------+zo·

•

! I

~~'------\lt-....;,._---_+_::r

.. .. .- D < ZS ESCASO • ~ U-SO MEDIO A ESTACIONES OE PESCA PELAGICA m50"00 AllI.OlOAHlE Eil > 100 MU'/ A9JHOANIE

17'1't------r------,r.,------t,-.-----'.. I-•17- -.-----"r•.------1S :.,-:':I7::-.-----..:r..-----r------1'Sf-.------.r.,------r------1-:-

Fig. 2.- Survey grid, pelcgic fisting stations and relative abundance distribution for pelagics in Area 2. r ,. •

• .. • /

• •

I\Jo •

,..1------t-t------::~~~~~~~_:;::t:2r lr+I ------+------.:~r_~~:r:-:::;.::j_..

• '" ... .

E5CASO ,,' ,.' I 0<25 • ~ 26-50 IEDIO .. [STACIOHES DE PESCA PElAGICA Im 50-100 ABUNDANTE

1'1 > 100 MJY ABUNOANTE

274------r-----,~----:t.-----T----_;J;:----h27.. ,.~-I -----r------.----±~:__---r---_r;_--_;tT1"'0. J' Ir

Fig. 3.- Survey grid, pelagic fishing stations and relative abundance distribution far pelagics in area 3. I ., 3 2 1

., , / 1 .t-----:<--l-:.::)-:...... ------+------f------,t------,,.....,,--,'--,r3~ .,_., '\ .... _-""'" -, , '-.. ,,' ..... ,.: ~ ,.... '- -z... r ... , ~' ::-..-:=-:-.....~ '" I I'" # .\\ L • ,. . ,I --~..... -\././ ..--.,- ~_ ,-'J t-,· I c.. , .. _..",-- ,_",,_ _" ,,' ,J-" ... ,.- .... -_-~..~: l , '\ ] ,-- - ~ A<~~' ,..;:~..'l... 'E ~ \ 1 ,1 .,r_. .:' J .; ... -;;:/,' " .. ;- \ ,• I _ ._--... I , /' ~,_,,,,,,,,,.r ----~ i '-._.-/ (

; I I I L._, -- /, '\ -',._// " ,-- i\, \,,

O

~ 26- '0 MEDIO '0-100 ABUNDANTE 11 I" ,1 • >100 NUY ABUNDANTE

~ .... ESTACIllNES OIE "IESCA "nAGICA . 1 1

Fig. 4,- Relative abundance distribution for pelagics in all the surveyed area.

i I I j "..._.. ~_. __ I' " 22 . .,. ·t• SO P 7 SO P 8 Graciosa ,\) Alegranza /.Q n= 1419 t.O n= 381

::" & JO 30

20 20

10 n

5 20 25 JO L cm. 5 20 25 30 Lcm .,. so P 9 Lanzarote l.Q n= 9883

Xl

20 I e Xl

5 10 15 20 2S 30 L cm.

.,. ·t• sa 50 P 5 P 6 /.Q EI Banquete 40 EI Banquete Fuerteventura 8W Fuerteventura 8W n= 77 n= 89 30 Ja

20 20

10 10

" e 5 n 15 20 25 30 35 L cm. 5 10 15 .,. -,. 50 P 1 SJ P 4 Tenerife N Tenerife 8 40 n= 561 40 n= 14

]Q 30

20 20

10 10

S 10 IS 20 25 30 L cm. S 10 15 20 25 30 L cm

Fig. 5.- Length distribution for mackerel in the fishing stations. 23 '/, '/, 50 P 8 50 P 9 • Alegranza E. Bocayna Lanzarote S, ;;" n= 175 4() , 40 n= 3872

30 30

~ 20

10 10

5 10 15 25 30 Lern. 5 () 15 ~ 2S 30 Lern.

'/, '/, SO P 9 50 P 6 E. Bocayna El Banquete I{J Lanzarote S. IIJ Fuerteventura S. n= 237 n= 64 Xl Xl

• 20 20

10 '0

5 10 15 20 25 30 L cm. 5 25 30 L cm

'I. ./. SO P 1 50 P 5 Tenerife N El Banquete 40 n= 253 40 Fuerteventura SW n= 1228

JO Xl

20 20

"10 10

5 25 30 L c:m. 5 20 2S 30 L :m.

PILCHARD BOGUE

Fig 6.- Length distribution for pilchard and bogue in the fishing stations. ~/. 30 24

MACKEREL .'; n= 12347 .- 20 ~

10

5 20 25 L crn.

./. 40

) 30 BOGUE e n= 5164

20

10

10

Fig. 7.- Length distribution for mackereI, bogue and pilchard in the surveyed area.