ANNALES • Ser. hist. nat. • 14 • 2004 • 2
short scientific article	UDC 597.5:591.9(262.05-13)
received: 2004-11-25
ON THE OCCURRENCE OF JOHN DORY ZEUS FABER LINNAEUS, 1758 (OSTEICHTHYES: ZEIDAE) IN A PERIMEDITERRANEAN LAGOON: THE TUNIS SOUTHERN LAGOON (NORTHERN TUNISIA)
Jamila BEN SOUISSI, Hamadi MEJRI & Jeanne ZAOUALI
Département des Ressources Animales, Halieutiques et des Technologies Agro-alimentaires, Institut National Agronomique de Tunisie,
43 avenue Charles Nicolle, 1082 Tunis, Tunisie
Amor EL ABED
Institut des Sciences et Technologies de la Mer, 2025 Salammbô, Tunisie
Olivier GUÉLORGET & Christian CAPAPÉ
Laboratoire d'Ichtyologie, case 104, Université Montpellier II, Sciences et Techniques du Languedoc, F-34 095 Montpellier cedex 05, France E-mail: capape@univ-montp2.fr
ABSTRACT
As a consequence of environmental restoration, the Tunis Southern Lagoon, which adjoins the Gulf of Tunis was invaded by several teleost species, including John Dory, Zeus faber (Linnaeus, 1758), which is the first record of this species in a perimediterranean lagoon. Preliminary data about the diet and feeding habits and mass growth of Z. faber in the area are given.
Key words: Osteichthyes, Zeidae, Zeus faber, first record, perimediterranean lagoon, Tunis Southern Lagoon
SEGNALAZIONE DEL PESCE SAN PIETRO ZEUS FABER LINNEO, 1 758 (OSTEICHTHYES: ZEIDAE) NELLA LAGUNA MERIDIONALE PERIMEDITERRANEA
DI TUNISI (TUNISIA SETTENTRIONALE)
SINTESI
Nella laguna méridionale di Tunisi, ai margini del golfo omonimo, dopo un intervento di rinnovo ambientale sono state segnalate diverse specie di pesci ossei. Tra loro anche il Pesce San Pietro Zeus faber (Linneo, 1758), indi-viduato per la prima volta in una laguna perimediterranea. Gli autori presentano i primi dati sulla sua alimentazione e sulle sue abitudini alimentari in quest'area e sulla crescita delle sue dimensioni.
Parole chiave: Osteichthyes, Zeidae, Zeus faber, primo dato, laguna perimediterranea, laguna méridionale di Tunisi
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INTRODUCTION
The John Dory Zeus faber Linnaeus, 1758 is widely distributed in the Atlantic from Norway to Madeira (Quero, 1986) and southward from the Azores to southern Africa (Blache et a!., 1970; Quero et a!., 1981; Seret & Opic, 1990). The species is reported throughout the Mediterranean and also in the western Black Sea (Tor-tonese, 1970; Quero, 1986; Fischer et a!., 1987). It is commonly captured in Tunisian waters, especially in the Gulf of Tunis (Le Danois, 1925; Gruvel, 1926; Bourgois & Farina, 1961; Maurin, 1962; Ben Mustapha, 1966; Lubet & Azouz, 1969;Azouz, 1974;Bradai, 2000). During the investigations conducted since 2001 in the close Tunis Southern Lagoon, 65 fish species were collected, including Z. faber, recorded for the first time in a perimediterranean lagoon (sensu Quignard & Zaouali, 1980, 1981; Quignard (pers. comm.)). Several specimens recorded in the area offer an opportunity to present preliminary data on this unusual occurrence in the present article.
MATERIAL AND METHODS
The Tunis Southern Lagoon adjoins the Gulf of Tunis and formerly covered 1,120 ha, with depths ranging from 0.15 to 1.1 m (average depth of about 0.6 m). As a consequence of an ecological restoration, the surface has been considerably reduced and now covers 720 ha, with a regular depth of about 2.10 m throughout the lagoon, except in restricted areas where it reaches 4 m maximum (Ben Souissi et a!., in press). It appears as an
elongated ellipse directed SW-NE: 36o17'53.4" and 36o47'48.0" N, and 10o12'22.2" and 10o16'41.4" E. Its northern border is the navigation channel, which is 10 km long and max. 12 m deep (see Mejri et a!., this issue).
Investigations were regularly conducted between 2001 and 2004, three times at least per week, and numerous specimens of both teleost and elasmobranch species were examined soon after they were landed by fishermen (Ben Souissi et a!., in press; Mejri et a!., this issue). They were mainly caught by gill-nets and trammel nets, occasionally by cast-nests, landing-nets, anglers and diving. Fresh and sometimes alive specimens were examined.
The specimens observed were measured to the nearest millimetre and weighed to the nearest gram. Methods of measurements and counts are given following Tor-tonese (1970), Quero et a!. (1981) and Quero (1986).
Two indices were used to provide a qualitative study of Z. faber:
-	vacuity index (VI): number of empty stomachs divided by total number of stomachs multiplied by 100.
-	frequency index (FI): number of stomachs, in which a food item was found, expressed as a percentage of total number of examined stomachs.
Tests for significance (p <0.05) were performed by using ANOVA, Student t-test and the chi-square test (Legendre & Legendre, 1979; Schwartz, 1986). Total mass vs. total length correlations were assessed by least-squares regression.
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RESULTS
The first specimen of Z. faber was recorded in Tunis Southern Lagoon in January 2002, soon after the environmental restoration in September 2001. The specimen captured on 6 October 2004 is preserved in 5% buffered formalin solution and deposited in the Ichthyological Collection of the Institute of the National Agronomique de Tunisie, catalogue number ZEI-Zef-01 (Fig. 1).
The main morphometric measurements and counts are presented in Table 1, following Dulcic & Pallaoro (2003).
Tab. 1: Morphometric measurements and counts of Z.
faber.
Tab. 1: Morfometricni in meristicni podatki pri vrsti Z.
faber.
Measurements (mm)	
Total length	300
Standard length	224
Head length	95
Interorbital space	12
Pre-orbital length	40
Eye diameter	21
Caudal fin height	104
Space between snout and vent	124
Pectoral fin length	42
Pectoral fin base	11
Dorsal fin length	217
Dorsal fin base	133
Pelvic fin length	96
Anal fin length	49
Anal fin base	89
Body height	109
Body depth	26
Pre-pectoral length	79
Pre-dorsal length	87
Pre-anal length	123
Pre-pelvic length	62
Distance between dorsal fin and caudal fin	13
origin	
Mass in grams	308
Counts	
Dorsal fin spines	10
Dorsal fin soft rays	23
Pelvic fin spines	1
Pelvic fin soft rays	7
Anal fin spines	4
Anal fin soft rays	22
Pectoral fin spines	0
Pectoral fin soft rays	13
Gill-rakers	20
Bony bucklers along base of soft dorsal fin	7
Bony bucklers along base of soft anal fin	8
The Tunisian specimen is described as follows: body oval, deep and strongly compressed; caudal peduncle as long as large; body height 2.06 times in standard length; head deep, dorsal profile convex over eye, its height 2.35 times in standard length; eye rounded rather large, 4.5 times in head height; mouth large and protractile, ending below nostrils close to eye. Pectoral fins short, pelvic fins 2.3 times as long. Body covered with small naked scales. Scutes present along belly. Colour golden grey, with a large black-edged spot on flank; membranes of spinous anal and pelvic fins black, spinous dorsal fin black.
Information provided by fishermen and our observations showed that the species is regularly caught in the area. However, it appears that, to date, captures are more abundant between January and July. They are rather rare during the summer, probably due to the warmer lagoon waters. Estimated captures per day reach 3,650 g maximum and the annual production is assessed to 800 kg.
Forty-two stomach contents of Z. faber were analysed with VI = 18.8%, gobids were the most abundant preys (63.8%); mugilid alevins (27.3%), Atherina boyeri (9.1%), Cerastoderma glaucum and gastropods (both 9%) were also observed. There are no data on the food and feeding habits of Z. faber from Tunisian waters. However, Fischer et al. (1987) noted that Mediterranean specimens preferentially feed on different teleost species, crustaceans and molluscs.
The relationship total mass (TM) vs. total length (TL) is plotted in figure 2. It shows the regular increase of total mass in specimens of less than 260 mm length; however, the larger specimens grew faster. This relation is: TM (g) = 1.531 TL (mm) - 87.592; r = 0.88; n = 42.
DISCUSSION
All measurements, counts, description and colour agree with Tortonese (1970), Quero et al. (1981) and Quero (1986). A literature review shows that the John Dory is mostly caught at depths ranging from 20 to 160 m, max. 400 m (Quero et al., 1981; Quero, 1986). This may explain why the species has never been recorded in lagoons such as the Tunis Southern Lagoon, whose depth does not exceed four metres. The abundance of the species in the Gulf of Tunis is the source of Z. faber in Tunis Southern Lagoon, which is at present submitted to a strong marine influence. By contrast, according to Medhioub & Perthuisot (1977) and Mtimet (2004), Z. faber has not been recorded in the Bahiret El Biban, a large hyperhaline lagoon adjoining the Gulf of Gabes, in southern Tunisia, where the species is also very abundant (Bradai, 2000).
In spite of the interspecific competition pressure for food in this restricted area with other teleost species (see Ben Souissi et al., in press) or elasmobranch species
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Fig. 3: John Dory (Zeus faber) (Photo: T. Makovec). Sl. 3: Kovac (Zeus faber) (Foto: T. Makovec).
TM (g)
TL (mm)
Fig. 2: Relationship total mass (TM) versus total length (TL) in Z. faber caught in Tunis Southern Lagoon. Sl. 2: Razmerje med skupno maso (TM) in celotno dolžino (TL) pri kovaču, ujetem v Tuniški južni laguni.
(Mejri et al., this issue), Z. faber feeds and develops normally. Furthermore, the irregular captures of Z. faber in the area, less abundant in the warm season, do not allow considering it a permanent inhabitant of the area and that a sustainable population will be established in
the area. Previously, Z. faber had been included among "thalassic species sensu Guelorget & Perthuisot (1983, 1992)". This category comprises species entering lagoons only occasionally or turning out accidentally from migratory movements. They develop and reproduce only in offshore areas. They are strictly thalassic species. However, the captures of Z. faber in the area are not fortuitous events. By contrast, Z. faber is not a sedentary small size species that would be abundantly and regularly caught all year round in lagoons. Moreover, this category of species develops and reproduces only in a confined area. It is a matter of strictly paralic species. A third category concerns species of which fry and juveniles (0+) enter lagoons to find sufficient resources and develop there. These species constitute a mid-term between thalassic and paralic species; they are "mixed species" or, rather, regular migratory species. Sufficient data are still not available to be able to include Z. faber in the latter category. The exact status of Z. faber in the Tunis Southern Lagoon remains speculative, and further investigations should be carried out in order to define it.
ACKNOWLEDGEMENTS
The authors wish to thank two anonymous referees for useful and helpful comments on the manuscript.
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O POJAVLJANJU KOVAČA ZEUS FABER LINNÉ, 1758 (OSTEICHTHYES: ZEIDAE) V PERIMEDITERANSKI TUNIŠKI JUŽNI LAGUNI (SEVERNA TUNIZIJA)
Jamila BEN SOUISSI, Hamadi MEJRI & Jeanne ZAOUALI
Département des Ressources Animales, Halieutiques et des Technologies Agro-alimentaires, Institut National Agronomique de Tunisie,
43 avenue Charles Nicolle, 1082 Tunis, Tunisie
Amor EL ABED
Institut des Sciences et Technologies de la Mer, 2025 Salammbô, Tunisie
Olivier GUÉLORGET & Christian CAPAPÉ
Laboratoire d'Ichtyologie, case 104, Université Montpellier II, Sciences et Techniques du Languedoc, F-34 095 Montpellier cedex 05, France E-mail: capape@univ-montp2.fr
POVZETEK
V Tuniški južni laguni, ki meji na Tuniški zaliv, so se po njeni okoljski obnovi znašle številne vrste pravih kostnic, med njimi tudi kovač Zeus faber (Linné, 1758), kar je prvi podatek za to vrsto v kaki perimediteranski laguni. Avtorji navajajo preliminarne podatke o prehrani in prehranjevalnih navadah kovača v tem območju in o rasti njegove mase.
Ključne besede: Osteichthyes, Zeidae, Zeus faber, prvi podatek, perimediteranska laguna, Tuniška južna laguna
REFERENCES
Azouz, A. (1974): Les fonds chalutables de la région nord de la Tunisie. 2. Potentialités de la pêche, écologie et répartition bathymétrique des poissons. Bull. Inst. Natn. Sci. Tech. Océanogr. Pêche Salammbô, 3(1-4), 29-94.
Ben Mustapha, Z. (1966): Présentation d'une carte de pêche pour les côtes nord de la Tunisie. Bull. Inst. Natn. Sci. Tech. Océanogr. Pêche Salammbô, 1(1), 21-38. Ben Souissi, J., H. Mejri, O. Guélorget, A. El Abed, J. Zaouali, C. Reynaud & C. Capapé (in press): Observations on fish species recorded in Tunis Southern Lagoon after an environmental restoration (northern Tunisia, central Mediterranean). Vie Milieu. Blache, J., J. Cadenat & A. Stauch (1970): Clé de détermination des poissons de mer signalés dans l'Atlantique oriental (entre le 20ème parallèle N et le 15ème parallèle S). Faune trop., ORSTOM, 18, 1-479. Bourgois, F. & L. Farina (1961): Rapport au Gouvernement de la Tunisie concernant les essais de chalutage au large des côtes tunisiennes. Rapp. FAO/PEAT, n" 1410, 31 pp.
Bradaï, M. N. (2000): Diversité du peuplement ichtyque et contribution à la connaissance des sparidés du golfe de Gabès. Ph.D. Thesis. University of Sfax, Tunisia, 600 pp.
Dulcic, J. & A. Pallaoro (2003): First record of the file-fish, Stephanolepis diaspros (Monacanthidae), in the Adriatic Sea. Cybium, 27, 321-322. Fischer, W., M. L. Bauchot & M. Schneider (1987):
Fiches FAO d'identification des espèces pour les besoins de la pêche. 'Révision' Méditerranée et mer Noire. Zone de pêche 37. Vol. II. Vertébrés. FAO, Rome, 2, 7611530.
Gruvel, A. (1926): L'industrie des pêches sur les côtes tunisiennes. Bull. Sta. Océanogr. Salammbô, 4, 1-136. Guélorget, O. & J. P. Perthuisot (1983): Le domaine paralique. Expressions géologiques, biologiques et économiques du confinement. Trav. Lab. Géol. Ecol. norm. sup. Paris, 16, 1-136.
Guélorget, O. & J. P. Perthuisot (1992): Paralic ecosystems. Biological organization and functioning. Vie Milieu, 42(2), 215-251.
Le Danois, E. (1925): Recherche sur les fonds chalutables des côtes de Tunisie (croisière du chalutier "Tanche" en 1924). Ann. Stn. Océanogr. Salammbô, 1, 1-56.
Legendre, L. & P. Legendre (1979): Ecologie numérique. 2. La structure des données écologiques. Masson, Paris. Lubet, P. & A. Azouz (1969): Etude des fonds chalutables du golfe de Tunis. Bull. Inst. Natn. Sci. Tech. Océanogr. Pêche Salammbô 1(3), 87-111.
223
ANNALES • Ser. hist. nat. • 14 • 2004 • 2
Jamila BEN SOUISSI et a!.: ON THE OCCURRENCE OF JOHN DORY ZEUS EABER LINNAEUS, 1 758 (OSTEICHTHYES: ZEIDAE..., 219-224
Maurin, C. (1962): Etude des fonds chalutables de la Méditerranée occidentale (Ecologie et Pêche). Rev. Trav. Inst. Pêch. Marit., 26(2), 163-220. Medhioub, K. & J. P. Perthuisot (1977): Le comportement géochimique des eaux de la Bahiret El Biban. Conséquences sur la pêche. Bull. Off. Natn. Pêch. Tunisie, 1(1), 23-35.
Mejri, H., J. Ben Souissi, J. Zaouali, A. El Abed, Y. Ver-gne, O. Guélorget & C. Capapé (2004): On the recent occurrence of elasmobranch species in Tunis Southern Lagoon (Northern Tunisia, Central Mediterranean). Annales Ser. hist. nat., 14(2). (in press) Mtimet, M. (2004): Rapport d'exploitation de la lagune des Bibans: année 2003. Société de Pêche El Bibanes, Tunisie, 24 pp.
Quéro, J. C. (1986): Zeidae. In: Whitehead, P. J. P., M.
L. Bauchot, J. C. Nielsen & E. Tortonese (eds.): Fishes of the North-eastern Atlantic and the Mediterranean. Vol. 2. UNESCO, Paris, p. 769-774.
Quéro, J. C., J. J. Vayne & C. Karrer (1981): Zeidae. In: Fischer, W., G. Bianchi & W. B. Scott (eds.): Fiches FAO d'identification des espèces pour les besoins de la pêche. Atlantique centre-est; zones de pêche 34, 47 (en partie). FAO, Rome, Vols. I-VII, pag. var. Quignard, J. P. & J. Zaouali (1980): Les lagunes pé-riméditerranéennes. Bibliographie ichtyologique annotée. Première partie: les étangs français de Canet à Thau. Bull. Off. Natn. Pêch. Tunisie, 4(2), 293-360. Quignard, J. P. & J. Zaouali (1981): Les lagunes pé-riméditerranéennes. Bibliographie ichtyologique annotée. Deuxième partie: les étangs français de Canet à Thau. Bull. Off. Natn. Pêch. Tunisie, 5(1), 41-96. Schwartz, D. (1986): Méthodes statistiques à l'usage des médecins et des biologistes. Flammarion, Médecine-Sciences, Paris.
Séret, B & P. Opic (1990): Poissons de mer de l'ouest africain tropical. Paris, Init.-Doc. ORSTOM Ed., p. i-vi + 1-416.
Tortonese, E. (1970): Osteichthyes, Pesci ossei, parte 1. Fauna d'Italia, 12, p. 1-565.
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