The feeding habits of the peacock wrasse, Symphodus (Crenilabrus) tinca (Linnaeus, 1758), from the southern coast of Tunisia were investigated with respect to fish size and season. Stomach contents of 1334 specimens, 8.1-23.1 cm total length, were analyzed. Of the total, 1166 were empty (87.4%). This percentage varied over the year, with a maximum during the spawning period (May- July) and minimum in February and August. Crustaceans and mollusks constituted the main prey in both the small and large size classes. As fish grew, the proportion of isopods in the stomachs decreased and the proportion of shrimps and benthic organisms increased. Diet composition varied seasonally, with crustaceans the most important prey item in all seasons especially summer and autumn. Higher feeding activity in winter may be related to the reproductive cycle of the wrasse and the abundance of benthic organisms. Results indicate that the peacock wrasse feeds on a wide range of prey items and is an opportunistic predator.Istraživan je sastav hrane i intenzitet ishrane lumraka, Symphodus (Crenilabrus) tinca (Linnaeus, 1758) sakupljenog na južnim obalama Tunisa. Analiziran je sadržaj želuca kod 1334 primjerka ukupne veličine 8.1-23.1 centimetara, od kojih je 1166 (87.4%) primjeraka imalo prazan želudac. Intenzitet ishrane kolebao je tijekom godine od maksimuma za vrijeme sezone mriješćenja (svibanj-srpanj) do minimuma u veljači i kolovozu. U hrani su prevladavali rakovi i mekušci svih veličina. Shodno veličini ustanovljeno je da je kod većih primjeraka zastupljenost izopoda u ishrani manja, dok su rakovi i bentički organizmi više zastupljeni. Intenzitet ishrane kolebao je prema godišnjem dobu, iako su rakovi bili najvažniji plijen tijekom cijele godine, a posebno u ljeto i jesen. Viši intenzitet hranjenja u zimskom razdoblju može se pripisati periodu mrijesta lumbraka i povećanoj prisutnosti bentičkih organizama. Rezultati ukazuju da se lumbrak hrani širokim rasponom plijena, te je oportunistički predator

Abderrahmane BOUAIN

Amira OUANNES-GHORBEL

English

OUANNES-GHORBEL, Amira

BOUAIN, Abderrahmane

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ISSN: 0001-5113AADRAYACTA ADRIAT.,47 (2): 175 - 182, 2006UDC: 596:591.13 (611) (262)The diet of the peacock wrasse, Symphodus (Crenilabrus) tinca (Labridae), in the southern coast of TunisiaAmira OUANNES-GHORBEL1* and Abderrahmane BOUAIN2 1 Institut National des Sciences et Technologies de la Mer, Centre de Sfax,B.P. 1035, 3018 Sfax, Tunisia2 Faculté des Sciences de Sfax, 3028 Sfax, Tunisia*Corresponding author, e-mail: amira.ouannes@instm.rnrt.tnThe feeding habits of the peacock wrasse, Symphodus (Crenilabrus) tinca (Linnaeus, 1758), from the southern coast of Tunisia were investigated with respect to fish size and season. Stomach contents of 1334 specimens, 8.1-23.1 cm total length, were analyzed. Of the total, 1166 were empty (87.4%). This percentage varied over the year, with a maximum during the spawning period (May-July) and minimum in February and August. Crustaceans and mollusks constituted the main prey in both the small and large size classes. As fish grew, the proportion of isopods in the stomachs decreased and the proportion of shrimps and benthic organisms increased. Diet composition varied seasonally, with crustaceans the most important prey item in all seasons especially summer and autumn. Higher feeding activity in winter may be related to the reproductive cycle of the wrasse and the abundance of benthic organisms. Results indicate that the peacock wrasse feeds on a wide range of prey items and is an opportunistic predator.Key words: Labridae, Symphodus (Crenilabrus) tinca, Mediterranean Sea, southern coast of            Tunisia, feeding habitsINTRODUCTIONThe peacock wrasse, Symphodus (Crenila-brus) tinca (Linnaeus, 1758) is a common fish in the Mediterranean and the eastern Atlantic from Spain to Morocco (QUIGNARD & PRAS, 1986). In Tunisia, it is usually found around rocks and seaweed in coastal areas at depths down to 50 m (AZOUZ, 1971; BEN OTHMAN, 1971). It is the most abundant species among the twelve Labridae fishes inventoried in the southern coast of Tuni-sia (BRADAI, 2000; OUANNES-GHORBEL, 2003).Very little is known about the feeding ecol-ogy of the peacock wrasse. It is an obliga-tory carnivorous feeder preying on sea urchins, ophiuroides, mollusks, copepods, crabs, and worms (QUIGNARD & PRAS, 1986; BUDAEV & ZWORYKIN, 1998). However, little is known about how the diet of the peacock wrasse is affected 176  ACTA ADRIATICA, 47 (2): 175-182, 2006by factors such as fish size, sex, and season. QUIGNARD (1966) presented a list of prey of the peacock wrasse in French Mediterranean coastal waters and showed that sea urchins, ophiuroides, and mollusks are its main food. A few brief stud-ies described the peacock wrasse diet in the Black Sea, where mollusks and copepods are its main prey (BUDAEV & ZWORYKIN, 1998).MATERIALS AND METHODSThe peacock wrasses used in this study were taken from different localities along the southern coast of Tunisia. They were captured by artisan fishing gears in sheltered seaweed areas close to the shore, generally in depths of 1-6 m. The study included 1334 individuals (736 females and 598 males). Sampling was conducted monthly from commercial landings. For each fish, the sex was recorded, and total length (TL) and eviscerated weight were measured to the nearest 1 mm and 1 g, respectively. In the laboratory, the gut was weighed (wet weight) and its content identified to the lowest possible taxonomic level. Species abundance and wet weight to the nearest 0.001 g were recorded.The total length of the fish ranged 81-231 mm. To assess for possible differences in diet with respect to size, fish were divided into two size classes: small (TL<133 mm) and large (TL>133 mm). Indices for quantitatively expressing the relative importance of different prey items in fish diets have been described by BERG (1979), HYSLOP (1980), and TIRASIN & JOR-GENSEN (1999). In this study, we used vacuity index (VI%), i.e., the number of empty stom-achs divided by the total number of stomachs multiplied by 100; percent frequency of occur-rence (%F), based on the number of stomachs in which a food item was found, expressed as a percentage of the total number of non-empty stomachs; percent numerical abundance (%Cn), i.e., the number of each prey item in all non-empty stomachs, expressed as a percentage of the total number of food items in all stomachs; and percent gravimetric composition (%Cw), the wet weight of each kind of prey, expressed as a percentage of the total weight of the stomach contents. Main food items were identified using the index of relative importance (IRI) of PINKAS et al (1971), modified by HACUNDA (1981), IRI = %F x (%Cn + %Cw). This index has been expressed as %IRI = (IRI/Σ IRI) x 100. Prey were sorted in decreasing order according to their IRI and the cumulative %IRI was calculated.RESULTSFeeding intensityOf the total 1334 stomachs examined, 1166 were empty (VI% = 87.4). VI% reached its maximum of 100% during May-July and minimum of 71.2% in February and August (Fig. 1). VI did not differ between males Fig. 1. Monthly vacuity index (VI%) of Symphodus (Crenilabrus) tinca177OUANNES-GHORBEL & BOUAIN: The diet of the peacock wrasse, Symphodus tinca, in the southern coast of TunisiaTable 1. List of prey recorded in the stomach contents of the peacock wrasse, Symphodus (Crenilabrus) tincaEmbranchment Superclass/Class Order/Suborder Group/Family Genus speciesAnnelida Polychaeta Errantia Nereidae Nereis hombergiNereis sp.NereisMollusca CephalopodaBivalviaGastropodaDecapodaAnisomyariaMesogastropodaArcheogastropodaSepiidaePteriidaeTurbinidaeTurritellidaePhasionellidaeTrochidaePatellidaeSepia officinalisPinctada radiata-Turritella sp.Phasionella tenuis--Arthropoda CrustaceaEucaridaPeracuridaCirripedia-DecapodaBrachyuraMacruraAmphipodaCopepodaIsopoda---PortinidaeCarididaeGammaridae-Sphaeromidae---Portinus mediterraneusPenaeus kerathurus--Sphaeroma sp.-Echinoidea Echinida Regularia Echinidae Paracentrotus lividisCnidaria Anthozoa - - -Bryozoa - - - -Foraminifera - - - -Chrysophyta Diatomeae - - -Angiospermae Monocotyledoneae Potamogetonaceae - Posidonia oceanicaPheophycophytes Pheophyceae Fucales Cystoseireae Cystoseira sp.Vertebreta OsteichtyesTeleostei-Perciformes----(87%) and females (87.9%) throughout the year and was higher in young specimens (93.7%) than in adults (87.4%). Diet compositionThirteen prey species belonging to 11 embranchments were identified (Table 1). Table 2 shows their frequency of occurrence, numeri-cal and biomass composition, and IRI. Crusta-ceans were the most important ingested prey, constituting 59.4% of the total IRI. Among the crustaceans, Macroura (shrimps) were the most important contribution to the diet (%IRI = 24.9). Isopoda and Mollusca were frequently eaten but in smaller amounts. Other prey groups were comparatively low and of less importance.Diet in relation to fish sizeCrustaceans and mollusks were the only prey eaten by young fish and the most impor-tant prey ingested by adults (Table 3). Among the crustaceans, isopods were the most impor-tant contribution to the diet for young fish; shrimps were most important for adults. Other prey groups in the adult stomach contents were of comparatively low and lesser importance.178  ACTA ADRIATICA, 47 (2): 175-182, 2006Table 2.Frequency of occurrence ( %F), numerical composition (%Cn), biomass composition (%Cw), and index of relative importance (IRI) of dietary groups of the peacock wrassePrey %F %Cn %Cw IRI %IRIAnnelida 6.0 3.1 7.7 64.8 0.4Mollusca Bivalvia Gastropoda Cephalopoda17.53.613.90.632.62.129.10.218.214.40.2714.011.2465.70.24.30.12.80.1Crustacea Brachyura Macrura Amphipoda Isopoda Cirripedia89.22.4164.51.822.33.643.9122.60.617.81.366.11.241.11.120.619812.05.34108.73.1856.38.359.40.124.90.15.20.1Antozoa 0.6 0.2 0.1 0.2 0.1Bryozoa 19.9 6.9 7.1 278.6 1.7Foraminifera 3.6 7.1 0.4 27 0.2Diatomeae 0.6 0.21 0.1 0.2 0.1Algae 15.7 5.4 3.7 142.9 0.9Teleostei 1.2 0.5 6.7 2.8 2.8Table 3. Frequency of occurrence (%F), numerical composition (%Cn), biomass composition (%Cw), and index of relative importance (%IRI) of dietary groups for small and large peacock wrasse Small (TL = 81-133 mm) Large (TL = 134-231 mm)Prey %F %Cn %Cw %IRI %F %Cn %Cw %IRIMollusca 12.5 26.9 9.5 2.7 18 33 8.12 6.9Crustacea 100 73.1 90.5 27.3 88 42.3 65 88.1Antozoa - - - - 0.7 0.2 0.1 0.1Bryozoa - - - - 22 7.3 7.4 3.1Foraminifera - - - - 4 7.5 0.5 0.3Diatomeae - - - - 0.7 0.2 0.1 0.1Alguae - - - - 17.3 5.8 3.8 1.6Teleostei - - - - 1.3 0.4 7 10.1Seasonal variationCrustaceans were the dominant prey in all seasons, especially in summer and autumn (%Cn>84.2; Fig. 2). In summer, small quantities of Mollusca and Bryosoa were also eaten whereas crustaceans were the only prey eaten in autumn, together with a small amount of accidentally ingested algae. Other prey groups were present in the winter and spring diets, in which Mollusca constituted the most frequently ingested prey.179OUANNES-GHORBEL & BOUAIN: The diet of the peacock wrasse, Symphodus tinca, in the southern coast of TunisiaDISCUSSIONIn general, the diversity of ingested prey groups and species indicates that peacock wrasse is an opportunistic predator, feeding especially on the benthic organisms of shallow meadows of posidonia beds, with a wide range of prey size and morphology. Young and adult peacock wrasse on the southern coast of Tuni-sia fed principally on crustaceans (isopods and shrimps) and mollusks (gastropoda) (OUANNES-GHORBEL, 2003) which are well represented in the benthic fauna of Gabes Gulf (BRADAI, 2000). All other prey (Polychaeta, Algae, Amphipoda, Antozoa, Bivalvia, Bryozoa, Brachyura, Cepha-lopoda, Cirripedia, Diatoma, Foraminifera, and Teleostei) were eaten only by adults, but in much smaller amounts and especially in winter. The intensified feeding of adults throughout winter can be attributed to the development of sexual maturity (OUANNES-GHORBEL et al., 2002); adults feed at high intensity in winter to opti-mize energy for gonad development (OUANNES-GHORBEL et al., 2002). Since benthic fauna was well represented in their stomachs, we suppose that adults change their behavior and relation-ship in the bottom biocenoses. QUIGNARD (1966), reporting on the food composition of peacock wrasse (6.0-35.0 cm TL) from the southern coast of France, confirmed its opportunistic behavior. In his study, stomach contents were dominated by the benthic organisms Ophuiora (three spe-cies), Mollusca (three species of Gastropoda, eight of Bivalvia), Crustacea (two species of Fig. 2. Seasonal variation of Symphodus (Crenilabrus) tinca diet based on %Cn values of the  major prey groups180  ACTA ADRIATICA, 47 (2): 175-182, 2006Decapoda, one species of Amphipoda), Annel-ida (one species), Amphineura (one species), and Foraminifera (one species), the same main prey species found in our study. Differences in food composition between the southern coast of France and the southern coast of Tunisia are due mainly to different distribution, abundance, den-sity, and availability of prey (QUIGNARD, 1966; OUANNES-GHORBEL, 2003).With growth, the proportion of small crus-tacean isopods diminished while the propor-tion of larger prey (shrimps) increased. In this respect, trophic ontogeny in peacock wrasse can be explained in terms of fish morphology. The width and mouth gape are linearly related to fish size (ROSS, 1978; STONER, 1980) and larger body and mouth sizes permit fish to capture a broader range of prey sizes (WARE, 1972; ROSS, 1977; STONER & LINGVISTON, 1984). The monthly vacuity indices (IV%) did not show a clear difference between males and females. The low IV% in February and August can be contributed to spawning; in the southern coast of Tunisia, peacock wrasse spawns during April and June (OUANNES-GHORBEL et al., 2002). The animal’s feeding intensity increased before and after this period. In conclusion, peacock wrasse is an oppor-tunistic predator of many benthic animal groups in the Gabes Gulf shallow meadow bed. Crus-taceans and mollusks were the major prey, although many benthic organisms (Polychaeta, Algae, Amphipoda, Antozoa, Bivalvia, Bryozoa, Brachyura, Cephalopoda, Cirripedia, Diatoma, Foraminifera, and Teleostei) were found in ana-lyzed guts, particularly in adult specimens.REFERENCESAZOUZ, A. 1971. Etude des biocénoses benthiques et de la faune ichtyologique des fonds chalu-tables de la Tunisie (Study of the biocenosis and ichthyological fauna from fishing bot-toms of Tunisia. Nothern and southeastern area). Région nord et sud-est. Thèse, Univ. Caen, 243 pp. BEN OTHMAN, S. 1971. Observations hydrolo-giques, dragages et chalutage dans le sud-est tunisien (Hydrological observations, drags and trawl in southeastern Tunisia). Bull. Inst. Natl. Sci. Tech. Océanogr. Pêche, Salammbô., 2(2): 103-120. BERG, J. 1979. Discussion of the methods of investigating the food of fishes with refer-ence to a preliminary study of the food of Gobiusculus flavescens (Gobiidae). Mar. Biol., 50: 263-273.BRADAI, M.N. 2000. Diversité du peuplement ich-thyque et contribution à la connaissance des sparidés du golfe de Gabès (Biodiversity of ichthyological settlement and contribution to the knowledge of sparids from the Gulf of Gabès). Thèse Doc. d’état, Fac. Sci. Sfax, 600 pp. BUDAEV, S.V. & D.D. ZWORYKIN. 1998. Difference in shoaling behaviour between ocellated (Symphodus ocellatus) and long-striped (S. tinca) wrasses and its relation to other behavioural patterns. Mar. Freshw. Behav. Physiol, 31(2): 115-121.HACUNDA, J.S. 1981. Trophic relationships among demersal fishes in coastal area of the Gulf of Main. Fish. Bull., 79: 775-788.HYSLOP, E.J. 1980. Stomach contents analysis. A review of methods and their application. J. Fish. Biol., 17: 411-429.OUANNES-GHORBEL, A. 2003. Etude écobiologique des Labridés (Poissons - Téléostéens) des côtes sud de la Tunisie (Ecobiological study of labrids (Pisces – Teleosts) from the south-ern coasts of Tunisia). Thèse, Fac. Sci. Sfax, 206 pp.OUANNES GHORBEL, A., M.N. BRADAI & A. BOUAIN. 2002. Période de reproduction et maturité sexuelle de Symphodus (Crenila-brus) tinca (Labridae), des côtes de Sfax 181OUANNES-GHORBEL & BOUAIN: The diet of the peacock wrasse, Symphodus tinca, in the southern coast of Tunisia(Tunisie) (Breeding period and sexual matu-rity of Symphodus (Crenilabrus) tinca (Lab-ridae), from the coast of Sfax (Tunisia). Cybium, 26(2): 1-4. PINKAS, L., M.S. OLIPHANT & I.L.K. IVERSON. 1971. Food habits of albacore, bluefin tuna and bonito in California waters. Fish. Bull., 152: 1-105.QUIGNARD, J.P. 1966. Recherches sur les Labri-dae (Poissons Téléostéens Perciformes) des côtes européennes. Systématique et biolo-gie (Pisces,Teleosts, Perciformes) from the European coasts. Systematics and biology. Ed. Cause et Castelnau. Montpellier, 247 pp.QUIGNARD, J.P. & A. PRAS. 1986. Labridae. In: Fishes of the north-eastern Atlantic and the Mediterranean. Vol. II, Whitehead P.J.P., Bauchot M.L., Hureau J.-C., Nielsen J. & E. Tortonese (Editors). UNESCO, 2: 919-942.ROSS, S.T. 1977. Patterns of resource partitioning in sea robins (Pisces: Triglidae). Copeia, 1977: 561-571.ROSS, S.T. 1978. Trophic ontogeny of the leopard searobin, Prionotus scitulus (Pisces: Trigli-dae). Fish. Bull., 76: 225-234.STONER, A.W. 1980. Feeding ecology of Lagodon rhomboides (Pisces: Sparidae): Variation and functional responses. Sympatric sparid fishes from sea-grass meadows. Fish. Bull., 78: 337-352.STONER, A.W. & R.J. LINGVISTON. 1984. Ontoge-netic patterns in diet and feeding morpholo-gy in sympatric sparid fishes from sea-grass meadows. Copeia, 1984: 174-178. TIRASIN, M.E. & T. JORGENSEN. 1999. An evalua-tion of the precision of diet description. Mar. Ecol. Prog. Ser., 182: 243-252.WARE, D. 1972. Predation by rainbow trout (Salmo gairdneri): the influence of hunger, prey density and prey size. J. Fish. Res. Board Can., 29: 1193-1201.Received: 11 July 2005Accepted: 23 March 2006182  ACTA ADRIATICA, 47 (2): 175-182, 2006Sastav hrane i intenzitet ishrane lumbraka, Symphodus (Crenilabrus) tinca (Labridae), na južnim oblama TunisaAmira OUANNES-GHORBEL1* i Abderrahmane BOUAIN2 1 Nacionalni institut znanosti i tehnologije mora, Centar  Sfax, P. P. 1035, 3018 Sfax, Tunis 2 Fakultet  znanosti u  Sfax-u, 3028 Sfax, Tunis*Kontakt adresa, e-mail: amira.ouannes@instm.rnrt.tnSAŽETAKIstraživan je sastav hrane i intenzitet ishrane lumraka, Symphodus (Crenilabrus) tinca (Linnaeus, 1758) sakupljenog na južnim obalama Tunisa. Analiziran je sadržaj želuca kod 1334 primjerka ukupne veličine 8.1-23.1 centimetara, od kojih je 1166 (87.4%) primjeraka  imalo prazan želudac. Intenzitet ishrane kolebao je tijekom godine od maksimuma za vrijeme sezone mriješćenja (svibanj-srpanj) do minimuma u veljači i kolovozu. U hrani su prevladavali rakovi i mekušci svih veličina. Shodno veličini ustanovljeno je da je kod većih primjeraka zastupljenost izopoda u ishrani  manja, dok su rakovi i bentički organizmi više zastupljeni. Intenzitet ishrane kolebao je prema godišnjem dobu, iako su rakovi bili najvažniji plijen tijekom cijele godine, a posebno u ljeto i jesen. Viši intenzitet hranjenja u zimskom razdoblju može se pripisati periodu mrijesta lumbraka i povećanoj prisutnosti bentičkih organizama. Rezultati ukazuju da se lumbrak hrani širokim rasponom plijena, te je oportunistički predator. Ključne riječi: Labridae, Symphodus (Crenilabrus) tinca, južna obala Tunisa, hranidbene navike,                                  rakovi, mekušci

Sastav hrane i intenzitet ishrane lumbraka, Symphodus (Crenilabrus) tinca (Labridae), na južnim oblama Tunisa

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