ACTA ADRIAT., 47 (2): 175 - 182, 2006 ISSN: 0001-5113 AADRAY UDC: 596:591.13 (611) (262) The diet of the peacock wrasse, Symphodus (Crenilabrus) tinca (Labridae), in the southern coast of Tunisia Amira OUANNES-GHORBEL1* and Abderrahmane BOUAIN2 1 Institut National des Sciences et Technologies de la Mer, Centre de Sfax, B.P. 1035, 3018 Sfax, Tunisia 2 Faculté des Sciences de Sfax, 3028 Sfax, Tunisia *Corresponding author, e-mail: amira.ouannes@instm.rnrt.tn 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 (MayJuly) 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 habits INTRODUCTION The peacock wrasse, Symphodus (Crenilabrus) 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 Tunisia (BRADAI, 2000; OUANNES-GHORBEL, 2003). Very little is known about the feeding ecology of the peacock wrasse. It is an obligatory 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, 2006 by 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 studies described the peacock wrasse diet in the Black Sea, where mollusks and copepods are its main prey (BUDAEV & ZWORYKIN, 1998). MATERIALS AND METHODS The 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 & JORIn this study, we used vacuity index (VI%), i.e., the number of empty stomachs divided by the total number of stomachs multiplied by 100; percent frequency of occurrence (%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 nonempty 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. GENSEN (1999). RESULTS Feeding intensity Of 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) tinca OUANNES-GHORBEL & BOUAIN: The diet of the peacock wrasse, Symphodus tinca, in the southern coast of Tunisia 177 (87%) and females (87.9%) throughout the year and was higher in young specimens (93.7%) than in adults (87.4%). Isopoda and Mollusca were frequently eaten but in smaller amounts. Other prey groups were comparatively low and of less importance. Diet composition Diet in relation to fish size Thirteen prey species belonging to 11 embranchments were identified (Table 1). Table 2 shows their frequency of occurrence, numerical and biomass composition, and IRI. Crustaceans 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). Crustaceans and mollusks were the only prey eaten by young fish and the most important prey ingested by adults (Table 3). Among the crustaceans, isopods were the most important 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. Table 1. List of prey recorded in the stomach contents of the peacock wrasse, Symphodus (Crenilabrus) tinca Embranchment Superclass/Class Order/Suborder Group/Family Genus species Annelida Polychaeta Errantia Nereidae Nereis hombergi Nereis sp. Nereis Mollusca Cephalopoda Bivalvia Gastropoda Decapoda Anisomyaria Mesogastropoda Sepiidae Pteriidae Turbinidae Turritellidae Phasionellidae Trochidae Patellidae Sepia officinalis Pinctada radiata Turritella sp. Phasionella tenuis - Cirripedia Decapoda Brachyura Macrura Amphipoda Copepoda Isopoda - Portinidae Carididae Gammaridae Sphaeromidae - Portinus mediterraneus Penaeus kerathurus Sphaeroma sp. - Echinoidea Echinida Regularia Echinidae Paracentrotus lividis Cnidaria Anthozoa - - - Bryozoa - - - - Foraminifera - - - - Chrysophyta Diatomeae - - - Angiospermae Monocotyledoneae Potamogetonaceae - Posidonia oceanica Pheophycophytes Pheophyceae Fucales Cystoseireae Cystoseira sp. Vertebreta Osteichtyes Teleostei Perciformes - - Archeogastropoda Arthropoda Crustacea Eucarida Peracurida 178 ACTA ADRIATICA, 47 (2): 175-182, 2006 Table 2.Frequency of occurrence ( %F), numerical composition (%Cn), biomass composition (%Cw), and index of relative importance (IRI) of dietary groups of the peacock wrasse Prey %F Annelida %Cn %Cw IRI %IRI 6.0 3.1 7.7 64.8 0.4 Mollusca Bivalvia Gastropoda Cephalopoda 17.5 3.6 13.9 0.6 32.6 2.1 29.1 0.21 8.2 1 4.4 0.2 714.0 11.2 465.7 0.2 4.3 0.1 2.8 0.1 Crustacea Brachyura Macrura Amphipoda Isopoda Cirripedia 89.2 2.41 64.5 1.8 22.3 3.6 43.9 1 22.6 0.6 17.8 1.3 66.1 1.2 41.1 1.1 20.6 1 9812.0 5.3 4108.7 3.1 856.3 8.3 59.4 0.1 24.9 0.1 5.2 0.1 Antozoa 0.6 0.2 0.1 0.2 0.1 Bryozoa 19.9 6.9 7.1 278.6 1.7 Foraminifera 3.6 7.1 0.4 27 0.2 Diatomeae 0.6 0.21 0.1 0.2 0.1 15.7 5.4 3.7 142.9 0.9 1.2 0.5 6.7 2.8 2.8 Algae Teleostei Table 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) %Cn %Cw Large (TL = 134-231 mm) Prey %F %IRI Mollusca 12.5 26.9 9.5 2.7 18 33 8.12 6.9 Crustacea 100 73.1 90.5 27.3 88 42.3 65 88.1 Antozoa - - - - 0.7 0.2 0.1 0.1 Bryozoa - - - - 22 7.3 7.4 3.1 Foraminifera - - - - 4 7.5 0.5 0.3 Diatomeae - - - - 0.7 0.2 0.1 0.1 Alguae - - - - 17.3 5.8 3.8 1.6 Teleostei - - - - 1.3 0.4 7 10.1 Seasonal variation Crustaceans 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 %F %Cn %Cw %IRI 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. OUANNES-GHORBEL & BOUAIN: The diet of the peacock wrasse, Symphodus tinca, in the southern coast of Tunisia 179 Fig. 2. Seasonal variation of Symphodus (Crenilabrus) tinca diet based on %Cn values of the major prey groups DISCUSSION In 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 Tunisia fed principally on crustaceans (isopods and shrimps) and mollusks (gastropoda) (OUANNESGHORBEL, 2003) which are well represented in the benthic fauna of Gabes Gulf (BRADAI, 2000). All other prey (Polychaeta, Algae, Amphipoda, Antozoa, Bivalvia, Bryozoa, Brachyura, Cephalopoda, 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 optimize energy for gonad development (OUANNESGHORBEL et al., 2002). Since benthic fauna was well represented in their stomachs, we suppose that adults change their behavior and relationship 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 species), Mollusca (three species of Gastropoda, eight of Bivalvia), Crustacea (two species of 180 ACTA ADRIATICA, 47 (2): 175-182, 2006 Decapoda, one species of Amphipoda), Annelida (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, density, and availability of prey (QUIGNARD, 1966; OUANNES-GHORBEL, 2003). With growth, the proportion of small crustacean isopods diminished while the proportion 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, 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 opportunistic predator of many benthic animal groups in the Gabes Gulf shallow meadow bed. Crustaceans 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 analyzed guts, particularly in adult specimens. 1977; STONER & LINGVISTON, 1984). REFERENCES AZOUZ, A. 1971. Etude des biocénoses benthiques et de la faune ichtyologique des fonds chalutables de la Tunisie (Study of the biocenosis and ichthyological fauna from fishing bottoms of Tunisia. Nothern and southeastern area). Région nord et sud-est. Thèse, Univ. Caen, 243 pp. BEN OTHMAN, S. 1971. Observations hydrologiques, dragages et chalutage dans le sudest 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 reference to a preliminary study of the food of Gobiusculus flavescens (Gobiidae). Mar. Biol., 50: 263-273. BRADAI, M.N. 2000. Diversité du peuplement ichthyque 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 southern coasts of Tunisia). Thèse, Fac. Sci. Sfax, 206 pp. OUANNES GHORBEL, A., M.N. BRADAI & A. Période de reproduction et maturité sexuelle de Symphodus (Crenilabrus) tinca (Labridae), des côtes de Sfax BOUAIN. 2002. OUANNES-GHORBEL & BOUAIN: The diet of the peacock wrasse, Symphodus tinca, in the southern coast of Tunisia (Tunisie) (Breeding period and sexual maturity of Symphodus (Crenilabrus) tinca (Labridae), 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 Labridae (Poissons Téléostéens Perciformes) des côtes européennes. Systématique et biologie (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. 181 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: Triglidae). 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. Ontogenetic patterns in diet and feeding morphology in sympatric sparid fishes from sea-grass meadows. Copeia, 1984: 174-178. TIRASIN, M.E. & T. JORGENSEN. 1999. An evaluation 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. ROSS, S.T. 1977. Received: 11 July 2005 Accepted: 23 March 2006 182 ACTA ADRIATICA, 47 (2): 175-182, 2006 Sastav hrane i intenzitet ishrane lumbraka, Symphodus (Crenilabrus) tinca (Labridae), na južnim oblama Tunisa Amira 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.tn SAŽETAK 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. Ključne riječi: Labridae, Symphodus (Crenilabrus) tinca, južna obala Tunisa, hranidbene navike, rakovi, mekušci