SCRS/2004/072 Col. Vol. Sci. Pap. ICCAT, 58(2): 502-509 (2005)

PRELIMINARY INVESTIGATIONS ON ATLANTIC BLACK SKIPJACK (EUTHYNNUS ALLETTERATUS RAF. 1810) IN THE EASTERN MEDITERRANEAN SEA

Abdullah Ekrem Kahraman1

SUMMARY

Atlantic black skipjack (Euthynnus alletteratus Raf.,1810) caught in Turkish and North Cypriot waters is one of the members of the Scombridae, having a wide distribution in the world, especially in the Atlantic Ocean, the Mediterranean, and adjacent seas. It is a fish with commercial value for the Turkish and North Cypriot fisheries. E.alletteratus are mostly caught by purse-seiners in Turkish waters. In North Cypriot waters, Atlantic black skipjack are caught by trolling. In this study, the length frequency distribution and length-weight relationship of 63 specimens between 58 cm (2808 g) and 82.5 cm (7192 g) caught in Turkish waters in 2003- 2004 was determined. In addition, total of 41 specimens caught in North Cypriot waters in 2001 were sampled. The fishing methods, the areas of catch, the seasons of catch, and the legislative measures in Turkish and North Cypriot waters were also investigated.

RÉSUMÉ

La thonine (Euthynnus alletteratus Raf. 1810) est capturée dans les eaux turques et au Nord de Chypre ; cette espèce appartient à la famille des Scombridés et se trouve largement répartie dans le monde, notamment dans l’océan Atlantique, la Méditerranée et ses mers adjacentes. Ce poisson est doté d’une valeur commerciale pour les pêcheries turques et du Nord de Chypre. La thonine est essentiellement capturée par les senneurs dans les eaux turques. Dans les eaux du Nord de Chypre, la thonine est capturée à la ligne traînante. La présente étude a déterminé la distribution des fréquences de taille et le rapport longueur-poids de 63 spécimens entre 58 cm (2.808 g) et 82,5 cm (7.192 g) capturés dans les eaux turques entre 2003 et 2004 . En outre, 41 spécimens capturés dans les eaux du Nord de Chypre ont été échantillonnés. Les modes de pêche, les zones des captures, les saisons de pêche et les mesures législatives en vigueur dans les eaux turques et du Nord de Chypre font également l’objet d’une étude.

RESUMEN

La bacoreta (Euthynnus alletteratus Raf.,1810), capturada en las aguas turcas y del Norte de Chipre, es un escómbrido con una amplia distribución en todo el mundo, sobre todo en el océano Altántico, el mar Mediterráneo y mares adyacentes. Es un pez con valor comercial para las pesquerías turcas y del Norte de Chipre. En las aguas turcas la bacoreta se captura sobre todo con cerco, mientras que en las aguas del Norte de Chipre se captura principalmente con curricán. En este estudio, se determina la distribución de la frecuencia de tallas y las relaciones talla-peso de 63 especimenes de entre 58 cm (2.808 g) y 82,5 cm (7.192 g) capturados en las aguas turcas entre 2003 y 2004. También se muestrearon 41 especimenes capturados en las aguas del Norte de Chipre en 2001. Además se investigaron los métodos de pesca, zonas de captura, estación de captura y medidas legislativas vigentes en las aguas turcas y del Norte de Chipre.

KEYWORDS

Euthynnus alletteratus, Mediterranean, Distribution, Fishing methods, Legislative measures

1 Istanbul University, Faculty of Fisheries, Ordu cad. No:200 34470 Laleli, Istanbul, Turkey, [email protected]. 502 1. Introduction

Atlantic Black Skipjack (Euthynnus alletteratus Raf.1810), a member of Scombrids, is found in the warm and tropical waters of the Atlantic Ocean and all over the Mediterranean Sea. In the eastern Atlantic, they are reported as far north as Skaggerak and as far south as South Africa. In the western Atlantic, they are known to inhabit the waters between Cape Cod and Brazil. They are usually found in coastal waters and also caught in the Aegean and in the Mediterranean Sea (Anon. 1986; 1995).

The fork length (FL) and total weight (TW) values of E. alleteratus are generally observed to be 45-80 cm, and 2500-7000 g respectively. The maximum length is about 100 cm (Anon. 1990).

The studies about the length and weight frequency distributions, length-weight, age-length and age-weight relationships, growth parameters, mortality rates, the first maturity length, fecundity, condition factor, gonosomatic indices, sex ratio, and spawning period of this species were made by Calkins and Klawe 1963; Landau 1965; Rodriguez-Roda, 1979; Klawe et al. 1970; Cayre and Diouf 1983; Yesaki 1994; Antoine et al. 1983; Johnson 1983; Hattour 1994; Allman and Grimes 1997; Kahraman and Oray 2001.

In Turkish and North Cypriot waters, Atlantic Black Skipjack has an economical value in the fishing sector. Till now, not much research has not been conducted on this fish. Kahraman (1999) completed a PhD study on it.

In this study, the areas and the seasons of catch, and the fishing methods of Atlantic black skipjack in Turkish and North Cypriot waters were investigated. A total of 63 specimens caught in Turkish waters, mainly from Northern Aegean Sea, and a total of 41 speciemens caught in North Cypriot waters were studied. Furthermore, the catch restrictions and the economic importance of Atlantic black skipjack were discussed.

1.1 Fishing grounds

E.alleteratus are caught near the coasts of southeastern United States, in the Gulf of Mexico, in the Carribbean Sea, and in the Mediterranean Sea (Anon. 1990). Fishing grounds in Turkish waters are in the Bay of İskenderun, the Bay of Antalya, the area between the Bay of Güllük and Turgutreis, around Foça, Aliaga, Badem Islands, in the Bay of Edremit, between Cape Kadırga and Babakale, and around Gökçeada and Bozcaada Islands (Kahraman 1999).

Figure 1 shows that the fishing grounds in Northern Cyprus are along the whole north coast including Cape Kormacit, and also on the northeast coast, especially between Cape Andreas and Boğaz.

1.2 Fishing Methods

The fisheries of E. alleteratus are more or less coastal, using trap nets, beach seines, surrounding gillnets, small purse seines, trolling and pole-and-lines (Anon. 1990). The fishing season is generally between February and June. In April and May, fishing is carried out intensively. Especially in Turkish waters, they are mostly caught by purse-seiners as by-catch (Kahraman and Oray 2001).

In Turkey, around 28-30 of purse-seiners catch this species as by-catch. The length of the purse seiners is between 22 and 62 m, the width being 6,2 - 16 m, with 300-2024 HP. The purse-seiners are of sheet iron material and the gross tonnage of the vessels range from 24,5 to 694 tons (Karakulak, 1999). The vessels carry two auxiliary boats for transportation, and have double nets for fishing operations (Alıçlı 1992).

Depending on the size of the vessels, the number of fishermen working on the boats are between 12 and 35 persons. All purse-seiners are donated with fish finders known as sonar and echo-sounders, and satellite borne remote sensing equipments such as satellites, GPS, etc. (Karakulak 1999).

The purse seines used in this fisheries are between 1450-2000 m in length and 180-275 m in depth. Their mesh sizes are being between 28-70 mm (Kahraman 1999).

During the day time, E.alletteratus are generally caught in depths of 90-365 m. (Kahraman 1999).

In North Cypriot waters, gill and trammel nets are generally used by artisanal fishermen on boats between 8-12 m. In this fishery, the mesh sizes of these nets are between 16 and 45 mm. E.alletteratus are mainly caught by trolling operated by these fishermen.

503 2. Materials and methods

In this study, a total of 63 specimens from Turkish waters (mainly from Çanakkale) in 2003-2004 and the total of 41 specimens caught from North Cypriot waters (obtained from Yedidalga fishing port) in 2001 were examined. The fork length (FL, in centimeters) and total weight (TW, in grams) values of all specimens were measured. In assessing the metric characters, the standard methods of FAO were applied.

During the reseach period, the length and weight frequency distributions of all samples obtained from Turkish (mostly from the northern Aegean Sea) waters were studied. In order to determine the length and weight of these specimens, a calliper of 100 cm and a digital balance were used. The length frequency distributions were arranged in 1 cm intervals. Furthermore, some length and weight parameters such as the aritmetic average, minimum, and maximum values were estimated.

The relationships between length and weight values were obtained by using logaritmic regression equation for Turkish waters. As the numbers of samples were small, the samples obtained from the North Cypriot waters could not be taken into consideration.

In this research, the fishing grounds and fishing methods of E.alletteratus both in Turkish and North Cypriot waters were studied.

3. Results

In this study, a total of 63 specimens caught from Turkish waters, most of which mainly obtained from Çanakkale, between January 2003- April, 2004 were examined. Also, a total of 41 specimens from Yedidalga fishing port in the Bay of Güzelyurt in North Cypriot waters between January and March, 2001 were examined.

The minimum, maximum, and the average fork length values of Turkish waters were measured as 58 cm, 82,5 cm, and 69,75 (± 0,81) cm, respectively. The length class of 75-75,9 cm was frequently observed (approximately 11,1%). The minimum, maximum, and the average total weight values were determined as 2808, 7192, and 4997 g, respectively.

The minimum, maximum, and the average fork length values of North Cypriot waters were measured as 34 cm, 63,5 cm, 40,11 (± 0,83) cm, respectively. The length class of 39-39,9 cm was frequently observed (approximately 25%). Also, it was determined that the minimum, maximum, and the average total weight values were determined to be 550 g, 3500 g, and 958,53 g, respectively.

In order to determine the relationship between the length and weight values, regression and correlation were applied for Turkish waters. The correlation coefficient (r) value which is around (1) indicates that the relationships between the length and weight values are strong and positive.

In Figure 2, the distribution of length frequency of the specimens obtained from Turkish waters, and in Figure 3, the length-weight relationships of these specimens are shown.

As the samples obtained from the North Cypriot waters were too small both in numbers and in length to assess statistcally or quantitatively, the length frequency distribution and regression & correlation analysis could not be done for these specimens.

4. Discussion

The fisheries of E. alleteratus are more or less coastal. They are caught by trap nets, beach seines, surrounding gillnets, small purse seines, trolling and pole-and-lines (Anon. 1990).

In Turkey, around 28-30 of purse-seiners catch this fish as by catch (Kahraman 1999). On the other hand, in North Cypriot waters, E.alletteratus are caught by trolling used by artisanal fishermen with boats between 8-12 m. The gill and trammel nets (mesh sizes: between 16 and 45 mm) are used for various fish species.

In this study, the maximum fork length and weight values of Turkish and North Cypriot waters were measured as 82,5 cm, 63,5 cm, and 7192 g, 3500 g, respectively. In the Mediterranean Sea, the fish which was to be 100 504 cm total length and 12000 g were measured (Anon. 2004). It is seen from the data on length and weight measurements of Atlantic Black Skipjack from North Cypriot waters were smaller than those of the individuals caught in Turkish waters.

The annual catch of E. alletteratus is estimated to be between 500 and 1500 tons, and the average catch size is around 70 cm FL. Until 1999, the minimum catch size of Atlantic black skipjack was 30 cm FL (Anon. 1997). As a result of investigations, a minimum size of 60 cm was determined (Kahraman and Oray 2001). The Ministry of Agriculture fixed the minimum size for Atlantic Black Skipjack as 60 cm FL (Anon. 2002). Most black skipjack caught from the catch areas were already above 60 cm (Kahraman 1999).

Over the last 10 years, the total world catch of E. alletteratus has decreased, dramatically. The world catch was about 26000 tons in 1990, decreasing to 7500 tons in 1995, and 9500 tons in 1999. The annual catch between 1992 and 2001 estimated for the world and the Mediterranean Sea is shown in Table 1 as metric tons (MT).

The total catch of Atlantic Black Skipjack in Turkey is estimated to be between 500 and 750 MT/ year (Anon. 2003). The real amount is probably 2,5 or 3 times more (average 1 500 MT) (Kahraman and Oray, 2001).

There is no any information about the catch statistics of this species caught in North Cypriot waters. As seen in Table 1, catch figures of Atlantic Black Skipjack do not include the catch of North Cypriot waters.

Atlantic black skipjack has a high export potential in Turkey. Turkish exports generally go to Japan, France, Spain, and Italy as mostly fresh or canned fish (Table 2). Sometimes, frozen and fileted products are also exported. France and Italy are the countries which receive the most exports.

The investigations on this species in Turkish and North Cypriot waters are still being carried out.

Acknowledgements

I would like to thank to Prof. Dr. Oray for his help in sampling and improving the English text, to Dr. Karakulak and Dr. Alıçlı for their useful comments. I also thank to the fishermen in Turkey and North Cyprus.

5. References

ALIÇLI, T.Z. 1992. Bir Gırgır Teknesinin Av Miktarı Üzerine Araştırmalar. İ.Ü. Fen Bilimleri Enstitüsü, Yüksek Lisans Tezi, s. 54.

ALLMAN, R.J., C.B. Grimes. 1997. Growth and mortality of Little tunny (Euthynnus alletteratus) larvae off the Mississippi River Plume and Panama City, Florida. Proceedings of the 48th Annual Tuna Conference, Tuna for the 21st Century, Inter-American Tropical Tuna Commission La Jolla, California, May 19-22, 1997.

ANON. 1986. Fishes of the north-eastern Atlantic and the Mediterranean, UNESCO, Volume II, 984.

ANON. 1990. Field manual for statistic and sampling Atlantic tunas and tuna-like fishes, 3. Ed. ICCAT, 79-80, Madrid, Spain.

ANON. 1995. Illustrated multilingual guide to the world’s commercial warmwater fish, p.108.

ANON. 1997. Republic of Turkey, Ministry of Agriculture and Rural Affairs, the Circular No. 31/1 Regulating the Fisheries Ankara.

ANON. 2001. The registers of fish exportation amount between 1989 and 2001, Istanbul Exporters Union, Istanbul.

ANON. 2002. Republic of Turkey, Ministry of Agriculture and Rural Affairs, the Circular No. 34/1 Regulating the Fisheries in 2000-2002, Ankara.

ANON. 2003. FAO Fishery Statistics Capture Production, Vol.92/1, 2001, Fao Fisheries Series No.63, FAO Statistics Series No.173, p.221 ISSN 1020-6663. Rome.

505 ANON. 2004. Euthynnus alletteratus Raf. 1810, www.fishbase.org

ANTOINE, L.M., J.J. Mendoza, P.M. Cayre. 1983. Progress of age and growth assessment of Atlantic Skipjack tuna, Euthynnus pelamis, from dorsal fin spines. U.S. Department of Commerce, NOAA Technical Report NMFS 8: 91-97.

CALKINS, T.P., W.L. Klawe. 1963. Synopsis of biological data on the Black Skipjack tuna, Euthynnus lineatus Kishinouye, 1920. FAO Fisheries Reports (H. Rosa, Jr., Editor), No. 6, Vol. 2, 130-146.

CAYRÉ, P.M., T. Diouf. 1983. Estimating age and growth of Little tunny, Euthynnus alleteratus, off the Coast of Senegal, using dorsal fin spine sections. U. S. Department of Commerce, NOAA Technical Report, NMFS 8: 105-110.

HATTOUR, A. 1984. Analyse de L’Age, de la Croissance et des Captures des Thons Rouges (Thunnus thynnus) et des Thonines (Euthynnus alletteratus L.) Pêches dans les Eaux Tunisiennes. Bull. Inst. Nat. Scient. Tech. Océanogr. Péche Salammbô, 11: 27-61.

JOHNSON, A.G. 1983. Comparison of dorsal spines and vertebrae as ageing structures for Little tunny, Euthynnus alletteratus, from the Northeast Gulf of Mexico. U.S. Department of Commerce, NOAA Technical Report NMFS 8: 111-115.

KAHRAMAN, A.E. 1999. The determination of age and growth parameters of Atlantic Little tunny (Euthynnus alleteratus Raf., 1810) caught in Turkish waters, Istanbul University, Institute of Science, Fisheries Program, PhD Thesis, Istanbul.

KAHRAMAN, A.E., I.K. Oray. 2001. Age and growth of Atlantic Little Tunny (Euthynnus alletteratus Raf., 1810) in Turkish waters. Collective Volume of Scientific Papers, Vol. LII, ICCAT, International Commision for the Conservation of Atlantic Tunas, SCRS/00/049, 719-732, Spain.

KARAKULAK, F.S. 1999. A study on the fishery and biology of bluefin tuna (Thunnus thynnus L., 1758) caught in Turkey, Istanbul University, Institute of Science, Fisheries Program, PhD Thesis, Istanbul.

KLAWE, W.L., J.J. Pella, W.S. Leet. 1970. The distribution, abundance, and ecology of larval tunas from the entrance to the Gulf of California. Bulletin Inter American Tropical Tuna Commission, Vol. 14, 507-544.

LANDAU, R. 1965. Determination of age and growth rate in Euthynnus alleteratus and Euthynnus affinis using vertebrae. Rapports et Procès Verbaux des Réunions. Publié par les Soins de Jean Furnesting Commission Internationale pour L’Exploration Scientifique de la Méditerranée, Vol. XVIII, Fas. I, 241-244.

RODRIGUEZ-RODA, J. 1979. Edad y Crecimiento de la Bacoreta, Euthynnus alleteratus (Raf.) de la Costa Sudatlántica de España. Inv. Pesq. Vol. 43(3), 591-599.

YESAKI, M. 1994. A review of the biology and fisheries for Kawakawa (Euthynnus affinis) in the Indo-Pacific Region. Interactions of Pacific Tuna Fisheries, Vol.2, FAO Fisheries Technical Paper 336/2, 388-408.

506 Table 1. The annual catch for Atlantic Black Skipjack (Anon. 2003).

Country 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Turkey 500 750 Cyprus 21 11 23 10 19 30 10 16 14 13 Israel 126 119 119 215 119 103 73 90 113 100 Morocco 370 44 43 231 588 196 203 75 101 87 Spain 156 161 156 155 270 350 417 390 2 322 Tunisia 664 242 204 696 824 333 1113 752 1453 1036 USA 565 357 159 150 90 451 300 514 220 357 Portugal 73 45 72 72 218 320 171 14 50 Venezuela 1409 1889 2115 1627 1840 2064 2815 2389 2040 1948 France 13 8 54 59 22 215 21 86 21 Ghana 11608 359 994 513 113 2025 359 306 707 730 Senegal 1521 1496 1628 1133 1066 1662 1604 460 1146 1613 Brazil 935 985 1225 1059 834 507 920 930 615 615 ______Medit. Total 1766 1266 1205 1894 2128 1608 2375 2096 2533 2071 World Total 18964 9429 8160 7429 9948 11495 11406 10350 11222 8453

Table 2. The annual export register of E.alletteratus in Turkey (kg) (Anon. 2002).

Country 1997 1998 1999 2000 2001

Japan 14 123 53 529 31 150 17 084 49 353 France 16 702 7 676 6 808 14 500 103 296 Spain 6 207 12 230 4 800 - 16 320 Italy - 12 025 1 000 1 000 84 405 USA - - - - 17 681

Total (kg) 37 172 85 510 43 758 32 584 271 055 Total ($) - 445 071 846 681 170 693 1 518 409

507

Figure 1. Fishing Grounds of Black Skipjack in Turkish and in Northern Cyprus.

508 14 n= 63 12

10

8

6 % Frequency 4

2

0

55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 FL (cm)

Figure 2. The distribution of length frequency of E.alletteratus caught in Turkish waters.

8 y = 0,0001x2,4683 n=63 7 R2 = 0,97 6 5 4

TW (Kg) 3 2 1 0 50 60 70 80 90 FL (cm)

Figure 3. The length-weight relationship E.alletteratus caught in Turkish waters.

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