original scientific paper UDK 597.587.2:591.16(262.3-1 Î ) EARLY LIFE HISTORY STAGES OF FAMILY SCOMBRiDAE IN THE EASTERN ADRIATIC Jakov DULČIČ Ph.D., biot. set., institute of Oceanography and Fisheries, HR-21000 Split, P.O.BOX 500 Dr. biol. znan., institut za oceanografiju i ribarstvo, HR-21000 Spilt, P.O.BOX 500 ABSTRACT Use of early life history stages offish in systematic arid ecological studies has increased in recent years, It is now recognized that eggs and larvae present a wide atray of characters that .ire largely independent of adult characters and suitable for a systematic analysis. Fisheries recruitment studies focus on the survival of eggs and larvae as the most important factor influencing variations in population abundance. A requisite to these studies is detailed information on the appearance of fish eggs and larvae in order to identify them in plankton samples. Family Scombrkiae is a of a great interest to the Croatian fishery. This paper reviews all available information on the early developmental stages of the family Scombridae found in the eastern Adriatic. Key words: early developmental stages, Scombridae, eastern Adriatic Ključne besede: zgodnji razvojni stadiji rib, Scombridae (skuše), vzhodni Jadran INTRODUCTION The importance of eariy-life-history studies to fisher­ies investigations and phylogenetic research has in­creased dramatically during the last decade. Eariy-life­history stages are now routinely used in fisheries studies to investigate the interannual variation in recruitment (Wooster, i 983), and in studies of the phyiogeny of fishes {Moser et al., 1984). The study of fish eggs and larvae is a key component in research into the biology, systematica and even population dynamics of fishes, in that it provides information on spawning areas and peri­ods of many species. By combining the location of the eggs, larvae and adults of a species with information on the surrounding environment, possible environmental effects on spawning (egg and larval transport, etc.) can be inferred. Studies of this type contribute to our under­standing of the early stages of development of fishes, which for certain species are still completely unknown. Consideration of the factors thai affect egg and larval survival is fundamental, since it is the early stages of de­velopment that will eventually determine the existence of good or bad year classes. This is one of the main thrusts of ichthyoplankton studies in those areas in which the requisite basic information is available (egg and larval surveys in spawning areas during the spawn­ing season, etc.) for the species of interest. family Scombridae is of great interest to the Croatian fishery. It forms a significant component of the total catch, it is not possible to get new data on catch for every species now, but GrubiSiC (1982) reported that it is between 200 and 700 tons per year for Spanish mack­erel (Scomber japonicus), 20 and 30 tons for plain bo­nito (Auxis rochei), around 350 tons for tunny (Thunnusthynnus) and around 5 tons for mackerel (Scomber scombrus). The object of this paper is to compile and present all available information on both the early development stages of the eggs and larvae of the family Scombridae found in the eastern Adriatic and possible spawning ar­eas and seasons of some species from the family. MATERIAL AND METHODS The present paper sets out descriptions of the eggs, yolk-sac larvae and larvae of the family Scombridae lakov S3UIČSČ: EARLY t. IFF HISTORY STAGES O F FAMILY SCOMBRIDAE I N TH E F ASTERN ADRlATiC , 9-16 likely to be collected in plankton samples in the eastern Adriatic, together with information on the possible spawning areas and seasons for some species. The egg and larval descriptions have mostly been taken from the existing literature. In some cases the descriptions were done by the author himself based on material collected during surveys; in other instances the descriptions were published by other researchers, either for eggs and larvae actually collected in the eastern Adriatic itself or for egg and larval material collected in other areas but for species that also inhabit the waters of the eastern Adriatic. Notochord (NL) lenght was measured for preflexion and standard lenght (SL) for flexion larvae. RESULTS AN D DISCUSSIO N Scomber scombrus Linnaeus, 1758. E s gg Spherical, 1.0-1.38 mm in diameter, yolk unseg­mented, oil globule 0.28-0.36 mm in diameter (Fig. 1). These measures were obtained from the material col­lected during the surveys in March 1990 in the area of Biitvenica (middle Adriatic) (DuldC, unpublished data). The eggs of mackerel were found during winter and spring cruises; in February in greater quantities on pro­file island Vis - Palagru2a archipelago and in smaller quantities along the Italian coast from Cape Gargano to Brindisi (Gamuiin & Hure, 1983). The existence of the winter spawning ground adjacent to Palagru2a archipel­ago was confirmed for the mackerel (Gamuiin & Hure, 1983). it is uncertain whether the smai! number of eggs recorded along the Italian coast indicate a widespread distribution of the Palagru2a spawning ground, isolated catches of eggs in mid-spring off the island Vis to Rovinj indicate the movement of the scomber along the east coast. The most intensive spawning was also recorded in Rijeka Bight, Kvarner and northern Kvarnerid (Lissner, 1939). The egg of the mackerel was first fully described by Cunningham (1889) from artificially fertilized eggs ob­tained by fishermen off Plymouth. Buchanan-Woilaston (1911) gave the average diameter of eggs from the southern North Sea as 1.186 mm, and that of the oil Fig. i: Scomber scombrus L, (A) Egg, 1-2 mm in diame­globule as 0.319 mm. Ehrenbaum (1921) gave the fol-ter {original drawn by author); (B) Yolk-sac larva, 2.4 lowing mean sizes for the egg: southern North Sea - end mm (original drawn by author); (C) Larva, 3.7 mm; (D) of May 1,276 mm; mid-July - 1.101 mm; north west of Larva, 5.2 mm; (F) Larva, 7.0 mm; (F) Larva, 8.0 mm; Dogger Bank - end of June - 1.139 mm; northern North (C) Larva, 14.0 mm (after Russell, 1976).Sea - 1.210 mm. Sella & Ciacchi (1925) found that the Si. 1: Scomber scombrus L. (A) ikra, 1-2 mm v premeru mean diameter of mackerel egg in the Mediterranean (originalna risba); (B) ličinka z rumenjakovo vrečo 2,4 (Ligurian Sea) is 1.139 mm (1.071 mm - 1.193 mm) and mm (originalna risba); (C) ličinka, 3,7 mm; (D) ličinka, the mean diameter of oii globuie is 0,32 mm (0.285 mm 5,2 mm; (F) ličinka, 7,0 mm; (F) ličinka, 8,0 mm; (G) - 0.360 mm). ličinka 14,0 mm (po Russelu, 1976). lakov DUICIC : EARLY UFE HISTORY STAGES O F FAMILY SCOMBRIDA i IN TH E EASTERN ADRIATIC, 9-1 C> Yolk-sac larvae DulciC (unpublished data) found mackere! yolk-sac larvae (n=3; range 3.7-4.1 mm length; oi! globule is between 0,21-0.23 mm in diameter) in the area of Kvarner and Rijeka Bight in April (stations 44°" 51'33"N 14° 12'E - depth 46 m and 45° 14'N 14° 25' 30" E ­depth 62.5 m). Cunningham (1892) described the newly hatched yolk-sac larva and succeeded in keeping some alive for 4 days until the yolk was almost entirely ab­sorbed. Subsequently, Holt (1893, 1898) also described the larva. When newly hatched, yolk-sac iarva is 3,3-3,9 mm long. Holt (1893) recorded a preanai length of 1.67 mm in a specimen 3.63 mm long. The pigmentation is characteristic. There is a group of melanophores on the head (Fig. 1). Double rows of irregularly distributed melanophores occur along the dorsal and ventral con­tours of the posterior half of the body starting a certain distance behind the anus. The ventral row is the more regular and continuous. Peritoneal black, pigment oc­curs on the upper half of the abdomen, and there are a few small melanophores on the snout and below the eye. In life there is a patch of yellow pigment behind the eye, and there are yellow chromatophores as well as melanophores on the oil globule. The eye is unpig­mented (Fig. 1). Larvae Karlovac (1962) presented data about the food of mackerel iarva. The length of larvae were betwen 4.73 mm and 15.69 mm. In the eastern Adriatic mackerel lar­vae occur in the areas of island Dugs otok, Blitvenica, island Vis and Palagruza archipelago during January, February, March, April and June (Karlovac, 1962). Kar­lovac (1967) found mackerel larvae at the stations in the 8raC channel, Regner (1982) found mackerel larvae at the station StonCica (43° 00' N 160 20'E) in the middle Adriatic in January and March with frequency 0.26%, and DulCiC (1992) only in January with frequency 0.04%. Holt (1898) described a specimen 7 days old in which the yolk was fully absorbed; it can thus be re­garded as an early larva. This was 4,46 mm long with a preanai length of 1.73 mm. Later larvae were described and figured by Holt (1898), Ehrenbaum (1905-09), 1921, 1923) and Alien (1917), among others. The larval pigmentation is quite distinctive and shows little change during growth of the larvae until it reaches a size of 13-14 mm when the young fish may begin to assume its mackere I-like form. The salient features of the pigmentation are the contour rows of dor­sal and ventral melanophores on either side of the body. These rows start a definite distance behind the anus, re­sulting iii a pigment-free zone dorsaily above the abdo­men and a clear space ventrally. The rows extend prac­ tically to the tail. In the earliest: stages there may be fewer melanophores in the dorsal row than in the ventral row, but as the larva grows, equal numbers may be developed in the two rows, up to about 14-15 melanophores in each. Sometimes the dorsal and sometimes the ventral row appears to have the larger melanophores, There are a few melanophores along the urostyle and on the base of the developing caudal fin. There are never any melanophores on the sides of the body between the dor­sal and ventral contour rows,There is a group of melano­phores on the crown of the head, and there may be one or two in front of the eyes and sometimes on the snout and lower jaw (Fig. 1). There is rather heavy peritoneal pigmentation confined to the upper half of the abdomen. The bending up of the urostyle is gradual and probably begins at a length of about 6 mm, when the rudiments of the caudal fin are beginning to appear. Dorsal and ven­tral interspinous areas begin to develop at a length of 8-9 mm. The following are characteristic morphological features: the presence of sharp teeth on upper and tower jaws, which become apparent already at a length of un­der 5 mm; the pointed anterior profile of the head when the mouth is closed; the flask-shaped form of the stom­ach and rectum. When the larva has reached a length of about 12-13 mm, dorsolateral melanophores begin to appear, and at a length of 16 mm these cover the upper half of the body. Myomere counts give 14 preanai ele­ments and 17 postanal elements for larvae between 5 mm and 13 mm, length (Ehrenbaum, 1924). Scomber japonicus Houttuyn, 1782 Eggs The eggs are spherical, on average ranging in diame­ter from 1.06 to 1.14 mm, with an oil globule 0.26 mm in diameter (Kramer, 1960) (Fig. 2). The yolk is unsegmented and under magnification (40x) can be seen to be filed with a large number of tiny vacuoles, The periviteiline space is narrow. In advanced stages of development both the dorsum of the embryo and the oil globule are pig­mented, the latter on the hemisphere facing the head. The spawning period of Spanish mackerel in the eastern Adri­atic is at the end of summer and first half of autumn, and possiblespawninggroundsare around the islandsof Mljet, Vis, Dugi otok, Premuda and jabuka (MiliSiC, 1994). Larvae Larvae of this species were caught during previous surveys in the eastern Adriatic (Karlovac, 1967; Regner, 1980), especially in its middle part (KaStela Bay - 43° 31 *N 16° 19'E - depth 42 m). DulciC (1991, unpublished data) found Spanish mackerel larva at the station (43° 55' 30" N )4° 49' E - depth 66.5 m) at the high sea of island Dugi otok. lakov DULČtČ: EARLY LiFL HISTORY STAGES O F FAMILY 5COMBRIDAE IN THE EASTERN ADRIATIC. 9-Hi Fig. I: Scomber japonicus Houttuyn, 1782 (A), (B), (C) Eggs, 1,06-1.14 mm h diameter; (D) Larva, 4.0 mm; (E) Larva, 5.0 mm; (F) Larva, 7,8 mm; (G) Larva, 10.0 mm; (H) Larva, 16.5 mm (after Kramer, 1960). Si. 2: Scomber japonicus Houttuyn, 1782 (A), (B), (C) ikre, 1,06-1,14 mm v premeru; (D) ličinka, 4,0 mm; (E) ličinka, 5,0 mm; (F) ličinka, 7,8 mm; (G) ličinka, 10,0 mm; (H) ličinka, 16,5 mm (po Kramer/u, 1960), After yolk absorption the larvae are deep-bodied and stubby, although body shape is more fusiform in indi­viduals approaching the juvenile stage. In preflexion lar­vae body depth at the cleiîhrum is 23-24% of NL (notochord length); body depth increases slightly to 25­26% of SL (standard length) in flexion larvae and up to 13 mm SL and then falls back in following stages, to 21% SL at 18 mm. The gut extends to somewhat less than the midpoint of the body in preflexion larvae, to the mid­point in flexion and eariy post-flexion larvae, and up to around 63% in the late larval stages. Head length also increases over development, representing 23-25% of SL in preflexion larvae and 28% of SL in post-flexion larvae and late larval stages. The principal body regions of the larvae of this species that display pigmentation are the head, peritoneum, and the midventral line of the tail (Fig. 2). Flexion and postflexion larvae also bear pigmentation on the dorsal contour of the body. Pigmentation on the midventral line of the tail in first-feeding larvae consists of two lines of melanophores that fuse info a single line from 7.5 mm SL. Pigmentation on the head becomes more abundant and outspread with larval growth, al­though it never reaches the cieithral symphysis. Pigmentation spreading outonto the lateral walls of the gut in postflexion larvae. At about 5 mm NL pigmentation appears on developing caudal fin, at about 7 mm SL on the dorsal margin of the body, and at 7.5 mm SL along the lateral line. The urostyle is turned upwards dorsally at 6 mm SL. Myomere counts give 31 elements for larvae between 5 mm and 13 mm length (Ehrenbaum, 1936). j a kov DULČIC: EARLY LIFE HISTORY STAGES O F FAMILY SCOMBR1DAE IN THE EASTERN ADRIATIC, 9-1 6 Thunnus thynnus thynnus (Linnaeus, 1758) Eggs Spherical, 1.00-1.12 mm in diameter, yolk unseg­mented, oil globule 0.25-0.28 mm in diameter, without periviteltine space, the oil globule and embryo are pig­mented (Sanzo, 1932} (Fig. 3). The spawning period is in spring in the coastal waters along the eastern Adriatic, especially in the northern Adriatic (Hrvatsko Primorje and KvarnerHMiliSic, 1994) and the middle Adriatic (Piccinetti, 1973; Piccinetti et ai., 1981). Fig. 3: Thunnus thynnus thynnus (Linnaeus, 1758) (A), (B) Eggs, 1.00-1.12 mm in diameter; (after Sanzo, 1932); (C) Yolk-sac larva, 3.00 mm; (D) Yoik-sac larva, 3.84 mm; (E) Larva, 3.90 mm; (F) Larva, 4.70 mm; (G) Larva, 6.80 mm; (Ft) Larva, 9.40 mm (originals drawn by author). SI. 3: Thunnus thynnus thynnus (Linnaeus, 1758) (A), (B) ikre, 1,00-1,12 mm v premeru; (po Sanzu, 1932); (C) Učinka z rumenjakovo vrečo, 3,00 mm; (D) ličinka z rumenjakovo vrečo, 3,84 mm; (E) ličinka, 3,90 mm; (F) ličinka, 4,70 mm; (G) ličinka, 6,80 mm; (H) ličinka, 9,40 mm (originalne risbe avtorja). lakov DULČIČr EARLY L!EE HISTORY STAGES O f FAMILY SCOMBRiDAE IN THE EASTERN ADRIATIC, 9-1« Larvae Larvae of this species were caught during previous surveys in the eastern Adriatic, at the high sea of the middle Adriatic {station Stondca, 43° 00' N 16° 20' E) in July and September with frequency 0.10% {Regner, 1982). Dulcid (1990, unpublished data) found tuna lar­vae in the Kvarner area (station 44° 5V 30" N 14° 12' E ­depth 46 m), Rijeka Bight (45° 14' N 14° 25' 30" E~ depth 62.5 m) and near island Susak (station 44° 30' 30" N 14° 11' E - depth 47 m) (n-4, range 7.40 - 9.00 mm length). Larvae were also found in the open middle Adriatic (Piccinetti, 1973; Piccinetti & Piccinetti-Man­frin, 1973, 1979; Piccinetti ef a/., 1977, 1981; Scaccini, 1953, 1959, 1961). Standard length of tuna larvae were between 5.3 and 6.3 mm (n=8) (Piccinetti, 1973). Pic­cinetti et al. (1981) found larvae in the Ionian Sea and southern Adriatic from mid-June to 20 July, and accord­ing to that they presumed that spawning grounds in the middle Adriatic are in connection with ones in the Mediterranean Sea. When newly hatched, yolk-sac larva is 3.0 mm long and the yolk-sac is almost entirely ab­sorbed at 3.8 mm Sanzo, 1932) (Fig. 3). Melanophores are distributed along the dorsal and ventral contours of the body at newly hatched yolk-sac larvae and after that there are only along ventral part. Peritoneal black pig­ment occurs on its dorsal side. There is a group of melanophores on the crown of the big head and at up­per half of peritoneum. One great spine appeared on the margine of preoperculum at 4.7 mm larval length. There is rather heavy peritoneal pigmentation at 6.8 mm larval length (Ehrenbaum, 1924). Eight spines appeared (one great in centre, four medium and three small) at 9.3 mm larval length. There are no more visible melanophores along the body (Fig. 3). Myomere counts give 18 preanai and 21 postanal elements for larvae between 5 and 13 mm length {Ehrenbaum, 1924), Auxis rochei (Risso, 1810) Larvae This species is distributed in the middle Adriatic {island jabuka) (Vilidci, 1985) and in the nothern Adriatic {MiliSic, 1994). Piccinetti 0973 ) found 28 larvae (60.9%) in the wider area of the middle Adriatic during summers in 1972 and 1973, Standard length was between 2.8 and 49 mm. Five larvae were also found in the southern Adriatic. According to the numerous findings of larvae in the middle Adriatic, Piccinetti {1973) supposed that this species spawn in that area. Milisid (1994) reported that bullet tuna spawn in spring in the Rijeka Bight, Kvarner and in the southern Adriatic. Piccinetti & Piccinetti-Manfrin (1979) recorded a great number of bullet tuna larvae in the wider area of the middle Adriatic and in the part of the southern Adriatic, including the jabuka pit, during 1972, 1973 and 1975-1977 period. Duliic (unpublished data) found larva of bullet tuna at station in the Rijeka Bight (45° 14' N 14° 25' 30iJ E - depth 62.5 m) in july 1990. Standard length was 12.7 mm, When newly hatched, yolk sac larva is 3.0 mm long (Sanzo, 1932), Preanai region is about 2/5 of total length at a length of 5.0 mm. There are 5 spines on the preop­erculum (Ehrenbaum, 1924) (Fig. 4), Only two or three melanophores are on the dorsal and six or seven on the ventral side of body at a short distance from the base of the caudal fin. When larva reached 5,7 mm, seven spines appeared on the preoperculum. There is a heavy pigmentation on the head and on the peritoneum at lar­val length of 12 mm. Myomere counts give 20 preanai elements and 19 postanal elements for larvae between 5 and 13 mm length {Ehrenbaum, 1924). Fig. 4: Auxis rochei (Risso, 1810) (A) Larva, 5.0 mm; (B) Larva, 5.7 mm; (C) Larva, 7.5 mm; (D) Larva, 12.0 mm (afterSanzo, 1932). SI. 4: Auxis rochei (Risso, 1810) (A) ličinka 5,0 mm; (B) ličinka, 5,7 mm; (C) ličinka, 7,5 mm; (D) ličinka, 12,0 mm (poSanzu, 1932). lakov DUlClC : EARLY UFE HISTOR Y STAGES O f FAMILY SCOMtiRtDAE IN TH E EASTERN ADRIATIC , !M 6 Genetic species identification of tunas is useful since Nishikawa, 1985), but these changes with developmen­morphological identification especially of the larval and tal stage and can be difficult, to apply with confidence juvenile stages can be difficult, Pigment patterns are (Nishikawa & Rimmer, 1987; Richards etai, 1990). used to distinguish larvae (Matsumoto et a!., 1972; POVZETEK Raziskovanje zgodnjih razvojnih stadijev rib je v zadnjih letih doživelo precejšen razmah, tako kot tudi siste­matične in ekološke študije o njih. Danes se zavedamo, da je preživetje iker in mladic najpomembnejši dejavnik, ki vpliva na spremembe v številčnosti populacije neke ribje vrste. Prvi pogoj za takšno preučevanje so podrobni podatki o pojavljanju iker in mladic v vzorcih planktona. Družina skuš (Scombridae) je izredno pomembna za ribištvo v državah ob jadranskem morju. V tem članku so obdelani vsi razpoložljivi podatki o zgodnjih razvojnih stadijih družine skuš v vzhodnem delu jadranskega morja. LITERATURE Allen, E.j. 1917, Post-larval teleosteans collected near Plymouth during the summer of 1914. j. mar. biol. Ass, U.K., 56: 471-486. Buchanan-Wollaston, H.j. 1911. Report on the results of the fish-egg cruise made by S.S."Huxley" in June 1909. Rep. N. Sea. Fish. Invest. Comm., 1906-1908: 207-234. Cunningham, j.T. 1889. Studies of the reproduction and development of teleostean fishes occurring in the neigh­bourhood of Plymouth, j. mar. biol, Ass. U.K., 1:10-54, Duicic, j. 1992. Istra2ivanje sastava i brojnosti ihtioplanktona u srednjem jadranu, Morsko ribarstvo, .3: 73-78. Ehrenbaum, E. 1905-09. Eier und larven von Fischen der Deutschen Bucht. Iii. Fische mit festsitrenden. Giern. Wiss. Meeresunt. Helgoland, vol VI: p. 127. Ehrenbaum, E. 1921. Ueber die Makrele, Laichver­hältruisse larven und jugendformen. Nahrung und Feinde. Arh. Deutsch Wiss. Kommn. Meeresforsch., In Wiss. Meeresuntersuch. Helgoland, N.F., 15, {1923-30) No. 2:1-30. Ehrenbaum, E. 1923. Ueber die Makrele. Laichver­hältruisse larven und jugendformen. Wiss. Meeresunt, Helgoland, vol. 15: pp. 32, Ehrenbaum, E. 1924. Scombriformes, Rep. Dan, Ocean. Exp. 1908-1910, vol 2 All ; pp. 42. Ehrenbaum, E. 1936. Naturgeschichte und wirtseliaftli­che Bedeutung der Seefische Nordeunges. Stuttgart, Gamulin, T. & Hure, j. 1983. MrijeSCenje i mrestiliSta pelagiL:nih riba u jadranskom moru (Sardina pilchardus, Engraulis encrasicolus, Scomber scombrus, Sardinella aurita, Sprattus sprattus). Acta Ad Hat. 24 (1/2): 97-131. Grubišic, F. 1982. Ribe, rakovi i školjke Jadrana. ITRO- Naprijecl, Zagreb-GRO l.iburnija, Rijeka: 240 pp. Holt, E.W.L. 1893. Survey of fishing grounds, west coast of Ireland, 1890-91: on the eggs and larval and post-lar­val stages of teleosteans. Scient. Trans. R. Dublin Soc., Ser. 2, 5: 121 pp, Holt, E.W.L. 1898. Notes on the reproduction of teleo­steans fishes in tine south-western district, J, mar. biol. Ass. U.K., 5: 107-155. Karlovac, J. 1962. Ispitivanje sadržaja probavnog trakta kod planktonskog stadija skuše (Scomber scombrus) u jadranu. Izvješcia rib-biol. eksp. "Hvar" 1948-1949, Vol. iV, No. 41, Split. Karlovac, J. 1967. Etude de I'ecoiogie de la sardine, Sardina pilchardus Walb., dans la phase planctonique de sa vie en Adriatique moyenne. Acta Adriat., 2: 1-101. Kramer, Q, 1960. Development of eggs and larvae of the Pacific mackerel and distribution and abundance of larvae 1952-56. Fish. Bull. U.S. 60: 393-438. Lissner, H, 1939. Ueber die Makrele des Adriatischen Meeres. Thafassia, vol .3, 8: 82 pp. Matsumoto, W.M., Ahlstrom, E.H., Jones, S., Kuawe, W.L., Richards, W,}. & Ueyanagi, S. 1972. On the classification of larval tuna identification particularly in the genus Thunnus. Fish. Bull. U.S. 70: 1-12. Milišid, N, 1994. Sva riba jadranskoga mora, NIVA d.0.0. Split, 448 pp. Moser, H.G., Richards, W.}, Cohen, D.M., Fahey, M.P., Kendall, A.W. )r. & Richardson, S.L. (editors) 1984. Ontogeny and systematics of fishes. Spec. Publ. 1, Am. Soc. Ichthyol. Herpetol. Allen Press, Laurence KS: 760 p. Nishikawa, Y. & Rimmer, D.W. 1985. Identification for larvae of three species of genus Thunnus by melano­ fakov DULâL : EARL Y LIFE HISTOR Y STAGES O F FAMILY SCOMBR I L>AE I N TH E EASTERN ADRIATIC , 9-1H phore patterns. Bulletin of the Far Seas Fisheries Re­search Laboratory 22; 119-125. Nishikawa, Y. & Rimmer, D.W. 1987. identification of larva! Tunas, Biilfishes and other Scombroid Fishes (suborder Scombroidei): an illustrated Guide, Hobart: CSIRO Marine Laboratories Report 186 p. Piccinetti, C. 1973, Stades larvaires et juveniles de thons en Adriatique. Ichtbyologia, 5:129-134. Piccinetti, C. & Piccinetti Manfrin, G. 1973. Forme lar­vali di Tunnidi in Adriatico. Atti V Congr. Naz. Soc. It. Biol. Mar., Ed. Salentino, Nardo: 163-168. Piccinetti, C & Piccinetti Manfrin, G, 1978. Larve di Tunnidi in Adriatico. Nova Thalassia, 3:163-173. Piccinetti, C. & Piccinetti Manfrin, G. & Dicenta, A. 1977. Premieres peches quantitative de larves de thonidés en Adriatique. Rapp. Comm. int. Mer Médit. 24 (S): 43-44. Piccinetti, C. & Piccinetti Manfrin, G. & Dicenta, A. 1981. Nouvelles donnés sur ia réproduction des thonidés en Mediteranée. Rapp. Comm. int. Mer Médit. 27{5): 165-166. Regner, S. 1980. The larval stages of fish in KaStela Bay. Acta Adriaî. 21(2): 123-136. Regner, S. 1982. Îstra2ivanja sastava i brojnosti larvalnih stadija riba u planktonu otvorenog mora srednjeg Jad­rana. Studia Marina 11-12: 45-60. Richards, W.J., Rotthoff, T. & Kim j-M. 1990. Problems identifying tuna larvae species (Pisces: Scombridae: Thunnus) from the Gulf of Mexico. Fish. Bull. U.S. 88: 607-609. Sanzo, L. Î932. Scombridae. Uova, stadi larvaii e giovanili di Telecstei. Mem. R. Com. Talassogr. !tal. Scacdni, A. 1953. La campagna di studio delia biología e delia pesca del giovani tonni nel!'Adriático compiuto da I Laboratorio di Biología Marina di Fano nel I'state 1952. Boll. Pesca. 1: p.18. Scaccirti, A. 1959. Bio-écologie des jeunes thons dens les mers italiennes. Proc. gen. Fish. Comm. Médit. 5(70): 449-495. Scaccini, A. 1961. Considération sur les déplacements et ia distribution des jeunes thons en Adriatique. Proc. Gen. fish. Comm. Médit. 6(45): 293-294. Selia, M. & Ciacchi, O. 1925. Uova e larve deilo sgom­bro del Mediterráneo (Scomber scombrus) ottenuti per fecondazione artificale, con notizie biologiche. Mem. R. Com. Talass. It. CXiV: p. 52, Wooster, W.S. 1983. From year to year: internationai variability of the environment and fisheries oí the Gulf of Alaska and the eastern Bering Sea. Rep. WSG-WO 83-3, Wash. Sea Grant Prog,, Univ. Wash., Seattle, NA 98195: 208 p. izvirno znanstveno deio UOK 594.5(262.3 Tržaški z.)'T995/1996" 597(262.3 Tržaški z.)"1 995/1996" POJAVLJANJE NEKATERIH VRST GLAVONOŽCE V iN RIB V SLOVENSKEM MORJU Bojan MARČETA dipl. biolog, Institut za biologijo, SI-1000 Ljubljana, Večna pot 111 B.Sc. in biology, Institute of biology, SI-1000 Ljubljana, Večna pot 111 IZVLEČEK V obdobju od aprila 1995 do septembra 1996 smo v slovenskem morju s pridneno povlečno mrežo ulovili 8 vrst glavonožcev in 56 vrst rib, ki jih navajam v seznamu. Časovno pojavljanje navajam za 8 pridnenib vrst glavonožcev, 4 vrste rib hrustančnic in 42 vrst rib kostnic. Natančnejše podatke o pojavljanju navajam za lignja (Loligo vuigaris), moškatno hobotnico (Eledone moschata), navadnega morskega psa (Mustelus mustelus), morskegagoloba (MySiobatis aquila), osliča (Meriuccius merluccius), mola (Merlangius merlangus), moliča (Trisopterus minutus), kovača (Zeus faber), volčiča (Serranus hepatus), špageta (Cepoia rubescens), bradača (Mullus barbatus), bukvo (Boops boops), špara (Diplodus annularis), ribona (Pagellus erythrinus), menolo (Spicara ilexuosa) in morsko ploščo (Piatichthys flesus), Ključne besede: Tržaški zaliv, Cephalopoda, Selachii-Chonclrichthyes, Osteichthyes, dinamika pojavljanja, seznam vrst Key words: Guif of Trieste, Cephalopoda, Selachii-Cbondrichthyes, Osteichthyes, occurrence, species checklist UVOO Slovenski del Tržaškega zaliva je bi! na področju raziskav rib, verjetno zaradi zanimivejšega preostalega dela Jadrana, vseskozi zapostavljen. Biološko razisko­vanje ribištva se je v tem delu Jadrana pričelo šele ob koncu osemdesetih let. Razlog za takratno raziskovanje je bil politične narave. Sporazum z Italijo o skupnem izkoriščanju osrednjega dela Tržaškega zaliva je pov­zročil nezadovoljstvo med lokalnimi ribiči, čemur je sledila odločitev o raziskavi zalog pridnenib rib in dru­gih užitnih organizmov (Štirn & Bolje, 1989). Žal je omenjeno raziskovanje po nekaj letih zamrlo. Pozneje je osamosvojitev Slovenije botrovala ponovnemu zagonu na področju ekoloških raziskav lovnih organiz­mov. Mlada obmorska država se je zavedela, da se bo morala po zgledu drugih držav, ki izkoriščajo morske dobrine, lotiti lastnega raziskovanja lovnih virov. Od začetka leta 1995 v ta namen deluje dvočlanska raz­iskovalna skupina na Inštitutu za biologijo v Ljubljani. Vsakemu slovenskemu morskemu ribiču je znano sezonsko nihanje števila lovnih organizmov v našem morju, ža! pa je natančnejših podatkov o tem malo. V raziskovalni nalogi Šttma & Boljeta (1989) so zbrani edini dosedanji podatki o dinamiki pojavljanja prid­nenib lovnih organizmov v našem morju. Pomanjkljivi so tudi podatki o številu vrst glavonožcev in rib v našem morju. Edini seznam vrst, ki obravnava tudi to območje, je deio Matjašiča ef al. (1975). Dinamika pojavljanja glavonožcev in rib je poleg seznama ulovljenih vrst osnova za nadaljnje ekološke raziskave teli skupin v slovenskem morju. V članku navajam rezultate o vrstah, ulovljenih s pridneno povlečno mrežo (PPM), in o dinamiki njiho­vega pojavljanja v ribolovnem morju Republike Slo­venije. Osnovni namen dela je bil ugotoviti, (i) katere vrste glavonožcev in rib se ulovijo s PPM in (ii) kakšna je njihova letna dinamika pojavljanja. Bojan MARČETA; POJAVLJANJE NEKATERIH VRST GLAVONOŽCEV !N Rig V SLOVENSKEM MORJU. 17-30 datum vzorčenja število dolžina potegov trajanje povprečna vzorcev (km) 28. 6. 1995 2 6,50 25. 7. 1995 3 13,00 3. 8. 1995 2 11,13 22. 8. 1995 3 13,75 18. 9. 1995 3 21,52 12. 10. 1995 3 6,57 22.11.1995 3 8,26 20.12. 1995 3 9,10 22.1.199 6 3 8,54 27. 2. 1996 3 8,86 10. 4. 1996 3 8,48 16, 6. 1996 2 5,63 16. 7. 1996 2 6,11 21.8.1996 3 7,67 24. 9. 1996 3 7,80 41 142,92 vzorčenja hitrost (Nm) (min.) (Nm/h) 3,50 60 3,53 7,00 184 2,00 6,00 158 2,25 7,43 206 2,16 11,62 356 1,96 3,55 119 1,79 4,46 120 2,23 4,91 120 2,46 4,61 125 2,22 4,79 122 2,36 4,58 121 2,29 3,04 60 3,04 3,30 80 2,48 4,14 124 2,01 4,21 120 2,11 77,14 2075 tip PPM/dolžina zgornje vrvi ustja PPM MEDITS/28,2 m KOM /36,8 m KOM /36,8 m KOM /36,8 m KOM /30 m KOM /36,8 m KOM/39 m KOM /39 m KOM /39 m KOM /52 m KOM /39 m MEDITS/28,2 m KOM /36,8 m KOM /39 m KOM /39 m Tabela 1: Podatki o potegih s pridneno po vlečno mrežo, na katerih temelji raziskava o pojavljanju glavonožcev in rib v slovenskem morju. Legenda: PPM = pridnena povlečna mreža, MEDITS = PPM, izdelana za raziskovalne namene (MEDITS, 1995, 1996), KOM = PPM lokalnega ribiča. Table 1: Data on pulls with bottom trawling gear, on which the research into the occurrence of cephalopod and fish species in the Slovene part of the Adriatic Sea is based. datum vzorčenja - sampling date, število vzorcev - No. samples, dolžina potegov ~ length of pulls, trajanje vzorčenja « sampling duration, povprečna hitrost = average speed, tip PPM/dolžina zgornje vrvi ustja PPM = PPM type/length of upper rope mouth of PPM. Key: PPM = bottom trawling gear, MEDITS = PPM made for research purposes (MEDITS, 1995, 1996), KOM = PPM of a local fisherman. MATERIAL I N METODE Material V raziskavi sem zajel glavonožce in ribe, ki so pred­met ribolova s PPM. V PPM so se ulovili predvsem pred­stavniki pridnenih vrst. V ulovu je bilo vselej tudi manjše število osebkov nekaterih peiaških vrst. Pelaške vrste sem upošteval v seznamu vrst, izpustil pa sem jih iz dinamike pojavljanja. Za določanje vrst sem uporabil naslednje ključe: Roper et al, (1984) - za glavonožce ter Šoijan (1965) in Whitehead et at. (1986a, 1986b, 1989) - za ribe. Obravnavano območje Vzorčili smo v delu ribolovnega morja Republike Slovenije, v katerem je dovoljena uporaba PPM. Ob­močje je proti obali omejeno s črto, ki je od obale od­daljena eno navtično miljo. Proti odprtemu morju je ob­močje omejeno z mejo teritorialnih voda Republike Slo­venije. Dno na tem območju je v glavnem ravno, globina morja pa je v večjem delu od 22 do 24 metrov. Z a vzhodni del je značilno ilovnato-muljasto dno (seve­rovzhodno od strunjanskega polotoka), v zahodnem de­lu je dno muljasto-peščeno, med oba tipa dna pa se vriva območje muljasto-detritnega dna (Štirn & Bolje, 1989). Vzorčna mesta in časovna razporeditev vzorčenja Vzorčili smo v obdobju od 24. 4. 1995 do 24. 9. 1996. Za raziskavo dinamike pojavljanja glavonožcev in rib sem uporabi! podatke 41 vzorcev iz obdobja od 28. 6. 1995 do 24. 9. 1996 (tabela 1), Potege s PPM smo opravili na treh transektih, ki so bili postavljeni bolj ali manj pravokotno na obalo. Transekt 1 je bil v vzhodnem delu (severozahodno od Koprskega zaliva ocl točke 45° 35,55' N, 13°40,30' L proti točki 45°34,37' N, "!3° 39,18* E); transekt 2 je bil v osrednjem delu (severno od rtiča Ronek od točke 45°36,40' N, 13°35,00' E proti točki 45035,00' N, 13°35,65' E} in transekt 3 v zahod­nem delu (severozahodno od Piranskega zaliva ocl točke 45°32,88' N, 13°30,45' E proti točki 45°33,90' N, 13° 28,98' E) (slika 1). V enem vzorčevalnem dnevu smo praviloma opravili tri potege s PPM. Vzorčili smo enkrat na mesec, včasih pa je zaradi slabega vremena prišlo do večjih razmikov med dvema vzorčevalnima dnevoma ali do manjšega števila vzorcev v enem dnevu. Potege s PPM do do 18. 9, 1996 smo opravili na območjih tran­sekt ov, vendar pa so bili potegi daljši (tab. 1). Bojan MARČETA: POJAVLJANJE NEKATERIH VRST GI.AVONOŽCE V IN RIB V SLOVENSKEM MORjU, 1 ?-30 Slika i: Zemljevid obravnavanega območja z označe­nimi (ransekti, na katerih smo vzorčili s pridneno po­vlečno mrežo. Fig. 1: Map of the dealt with area with marked transects in which sampling was carried out with bottom trawling gear. Metode vzorčenja Vsa vzorčenja smo opravili v svetlem delu dneva, junija smo vzorčili v okviru mednarodnega programa za raziskovanje pridnenih komercialnih organizmov v Sre­dozemlju {MEDITS}. Pri tem smo uporabili metodiko, ki jo predpisuje omenjeni program {MEDITS, 1995, 1996). Z a metodološko Izhodišče lastnih vzorčenj smo se držali protokola programa MEDITS, ki pa smo ga morali nekoliko prirediti. Obe vzorčenji sta se razlikovali pred­vsem po tipu uporabljene PPM, času trajanja vzorčenja {MEDITS: 30 minut.; naše vzorčenje: 40 minut) in hitrosti vleke {MEDITS: 3,3 Nm/h; naše vzorčenje: 2,2 Nm/h). Natančnejši podatki o vzorčenju so v tabeli 1. Lovili smo z dvema ploviloma in mrežama, V okviru programa MEDITS smo vzorčili z ribiško ladjo dolžine 32 metrov in močjo motorja 500 kilovatov. Obakrat smo uporabili PPM {diagonala očesa saka - 20 mm), izde­lano v raziskovalne namene {MEDITS, 1995). Lastna vzorčenja smo opravili z najetim ribiškim čolnom dol­žine 11,46 metrov in močjo motorja 80 kilovatov, ki tudi sicer lovi na tem območju s PPM. Uporabili smo srednje težko mrežo, izdelano 2a komercialni ribolov (diagonala očesa saka - 37 mm). V času raziskave je ribič spreminjal dolžino kri! mreže, kar pa sem pri izra­čunih vselej upošteval. Analiza vzorcev ter ocena abundance in biomase Vrstno sestavo vzorcev sem ugotavljal s pregledo­vanjem celotnih vzorcev. Ribe in glavonožce sem raz­vrstil po vrstah. Z a vsako vrsto sem prešte! osebke in jih stehtal. Glavonožcem sem meril dolžino plašča (Roper et a!., 1984), ribam pa celotno telesno dolžino (Sparre & Vanema, 1992). Površino potega s PPM sem izračuna! po obrazcu: a = s x h x X z [km2] kjer je s pot, ki jo je opravilo plovilo, h dolžina zgornje vrvi ustja koče in X2 faktor zmanjšanja ustja mreže. Po Shindo {1972) sem uporabil faktor zmanjšanja 0,66. Dolžino poti sem odčital z GPS na osnovi treh točk za vsak vzorec. Prva točka je bila mesto začetka vleke, druga točka je bila časovno na sredini vleke in tretja na koncu vleke, Biomaso za posamezno vrsto sem izračunal po obrazcu: b = (Cw/a)/X | [kg km"2] kjer je Cw teža organizmov posamezne vrste v vseh vzorcih, opravljenih na isti dart, a površina vseh potegov s PPM in Xt faktor uhajanja rib z območja ustja mreže (Sparre & Vanema, 1992). Po zgledu Stirn in Bolje (1989) sem uporabil faktor uhajanja rib 0,4, Abundanco osebkov posamezne vrste sem izračunal po obrazcu: Ab = (Ex/a)/X| [;EX km"?] kjer je Ex število osebkov posamezne vrste v vseh vzorcih, opravljenih na isti dan. REZULTATI iN RAZPRAVA Seznam ulovljenih vrst Seznam 64 ulovljenih vrst temelji na 55 vzorcih. Ulovili smo 8 vrst glavonožcev in 56 vrst rib. Od rib hrustančnic (Selachii - Chondrichthyes) smo ulovili 4 vrste, od rib kostnic (Osteichthyes) pa .52 vrst (tabela 2). Med glavonožci je bilo 7 pridnenih vrst in 1 pol­pelaška. Tri vrste rib hrustančnic so bile pridnene, ena pa bentopelaška. Od rib kostnic je bilo 37 pridnenih, 11 pelaških, 3 bentopelaške in 1 polpelaška vrsta. Seznam vretenčarjev severnega Jadrana (Matjašič et al., 1975) dopolnjujem z eno vrsto giavonožca (Sepia orbignyana) in osmimi vrstami rib {Raja asterias, Mullus surmuletus, Pagellus bogaraveo, Deltentosteus quadri­maculatus, Parablennius tentacularis, Trigloporus lasto­viza, Phrynorhombus regius in Monochirus hispidus). Seznam ugotovljenih vrst se v glavnem ujema s seznamom, ki ga navaja Bolje (1992). Večji odmik je bil pri ribah hrustančnicah. V vzorcih, ki jih je obdelal Bolje, so bili še Scyliorhinus canicula, Squalus acan­thias, Raja miraletus, Torpedo marmorata. V mojem seznamu rib kostnic manjkajo vsi predstavniki družine Scorpaenidae, ki jih je ugotovi! Bolje. Vsi omenjeni od­miki so verjetno povezani z raziskovalnim območjem, saj je Bolje vzorčil tudi bolj jugozahodno. Bojan MAKČFJA: POJAVLJANJE NEKATERIH VRST ClAVONOŽCEV l\> RJFi V SLOVENSKEM MORJU, 17-30 Taxa Iv-nr.i 1-/J'/I'U') ).f;: i j FLIÎIIIINK, 1826 2 5 D •Sninicliciae 7i-iv.\7i.i i.p <:) 7 P Loii^iniciat.' A/fateurbx medij il.ovn.-ii-Mjš, i 75,::;i 1S9LI 9!) D i Loligo mtt&m LimurcL, ! 79(1 853 'J 5 H' i 0< topoiiirl.ici Octi'fjus vit!iijri<. Cuvier, 1797 ! 2 Di tlcchiw inoich.a.i 1799) 1641 8 6 p i CHONDRICHTHYÉS AldSlm/uS ti>(;$t?h/E l'I kn 11,1 l-r_;s. 77171 21't 4 3 f)2 iîapiLu1 Rij.1 Jilero Dtfisrochf, 1 809 3 5 D 1 l'J.iyiiifi'ii p.mmjç] l.i^r:,vru> ! 777 1 D J MyliOb;iiidae MyliObjtti .qailz t.-::-. 1 7311; 7 14 BP OSTfICHTHYES OiipeiiJae Mou f.ill.a (Uicepcufe, 1»nii 1 2 P' j.-iir/ifj !jUdlârtkn W1',;fi.:.1 7921 81 17 P' P5 Ipr.lUiK. (1 limitai:-, 3 "7ljj 24 M Lngr.iitliiSisii ErtgmuH'; enoasicolm (l.kMiaem. 1 7.r,8ii h 12 pi, Ciin^rid.'ie Ciiili.'Pii'Onp'rJJAMedi, 1 738? IJiuwus, 1758) \y Syn^niMhkkip 1-hppocanipiiS fjiniilosfs Lnv.irh, 1717 1 2 D SyitH'ldlltKS .ICI):', [ ivili.lL'U'i, T7I8 0 A-Îii/Îliixitu mliWurcims (LinnSPiis, 1 7 7i7) 303 41 I'l") .Viivi.iii^nr: nv.-T/'.in^fi1 (Linnaeus. J758) -?670 86 D» Tritoplčrus miliums {Linnntiis. 17r>i!) 0 " Z^idai1 Zeus fjber imnjcw;, 1758 «23 ,i2 D'« Siirr^nkliit.' SerMnus ht'p,>iii5 O.inn-i'.nis, 175,») .M 5 D 86 V''1 Momiiidyi? 77; i. v 7'j rei*i.-,' Uhi.ix (LmnTKniji, ! 7 !>ë) ! 2 BP Cepoiiiku* Cnpol.i nii}:-',<:i:ii: Lînnneiis. 1 777 Z4<> 52 Of. TuKbllP/s nierlilen-tueus !Sioir>il^chner, S (168)6 1« i>n Tr.)tiKk.ms Hiiclmms il.innA^us, 1777; Si 31 pu Sdncnittae tJ»ibn'i;:-.. 1 777. 1 D I'l Mirliidiin Miilh'S L 1 758 !95 M> D15 Malini turmuli'lus Liniirteus, i / 7Ij 1 2 Boop* /JCiOfJ.i it. ; 77'i l 41 iî D, PP" Ocmex détins :Lt;-.".7i:u7 1758) 1 2 RI ti I.Vplodiis anr.iib/j', 1 : ,'i ifiniie'ii.s, 17777 8.1.) r>9 D if' Ulhotwjihus yponriyros, 17.78) BP P' 7J7fri\7.7 ifti'.iriîVi'.'i-, 1761',) 2 2 DII' Pj'huIIiiî eiythrimis (Ijitnnnis, ! 7f,8) 1984 74 DP> P.Wiu* fijy.ws ii.inn;ieu7 1 77 7 I 2 D"' fy.jnu. .l(li,ltJ Linr.uiiiis I 758 1 i Dl< > 5p/a\rJ :lr\i/oyi «Jiini-^tiui:, i il 117 95 Wi ' $ymphorji.ts cinwiy, (liorn;tJcrri>, 17Jl ;J' i r» 7 0 Tnlcbiim^i* Trjdi'iw df.KO Liniuic"..".. J 77ii ^ 7 D18 UF.inostopiiLu1 7 sr-ib^i l.ii'in.'ieus, : ^ 7 i i ? . m» .Scni^briil^i­ 7 0i,':,7fV j.iyippitvs HoutUiyn, 1782 2 5 P'j iî ScomlX'r senmbrus 1 77o 2 r PJO Goliiiffnir: Dçlieolosleus q-.LKlrm>.K (;lj8) 1 2 0 Mup^lii^i .iirji.j ill; 17 11 !J. i'iî Al.htii inirLto ^iifîiiii'i.î i innat'Lis, î 77;J . 15 10 l'î.i Altmrinn boyeri Rissp, ' 17i 2 p liii'.i-iir.: InyJj l',\-<:i!t,i i.inn.n»;... 1 771 o iri^ppoivs IjilovrTr.î irii'.inniili [ 7lnq. f 2 0 Sco)jhihiitfiii(!rffi Fis !,';i i i/>h š 1 yiii i i7:infint:it'.' 1 788) 4 D iîoîlliftiti' 7iiiiiMi;Ml,,'v;ii: Ij!LY/I.Î iW^lbaunn, 1 777 lf, l î Dii-î J-' 1 i l i r i.-.! i i iii7 :, :.' i'ijlichthys iics'15 i.|nn,i.i'ui, 1 7771 15 Î7 0 « Sotercta? B'il!los .'•rii'iM l'ii/i.'.in'', rh.n:;'-.,!. 1)106 5 7 î 0[>lliitl.lP tijf.'iiiiiM ,i'i7i.,>,'rinii:i Liin'iiiiiii. 1758 1 DJ<- Tabela 2: Seznam vrst, ulovljenih s pridneno povlečno mrežo v slovenskem morju. Seznam vrst temelji na 55 vzorcih iz obdobja od 24. 4. 1995 do 24. 9. 1996. Število ulovljenih osebkov in pogostnost pojavljanja vrste v vzorcih pa temeljijo na 41 vzorcih (28. 6. 1995 do 24. 9. 1996). D = pridneno (bentoške ali demerzalne vrste); P = pelaško; PP -polpelaško; BP = bentopelaško. Table 2: List offish species caught with bottom trawling gear in the Slovene part of the Adriatic Sea. The list is based on 55 samples taken from April 24th 1995 to September 24th 1996. Numbers of caught individuals and frequency of occurrence in samples are based on 41 samples (jane 28th 1995 to September 24th 1996). št. osebkov = No. individuals pogostnost (%) = frequency (%) bivališče -habitat D -demersal species P = pelagic> PP -semipelagic, BP -benthopelagic. i Roper in soci., 1984; 28ninstetter, 1989; •iStehmann & Burkel, 1989; ''McEachran & Capape, 1989; -^Whitehead, 1989a; ^'Whitehead, 1989b; 7Bauchot & SakUviha, !986 ; »Svetoviriov, 1986a; fSvetovicJov, 1986b; 'OQtiero, 1986;11 Tovtonese, 1986a; «Tortonese , 1986b; »Smith-Van«. , 1986; N l.abbis h Nin g Chao , 1986; 15Hureau, 1986a;16Bauchot & Hureau, 1986; 17Tortonese, 1986c ; 18 Tor ­tonese, 1986ci; ^Hureau , 1986b; 20Coi!cil:te, 1986; ^Fnc ­ke, 1986; ^Ben-Tuvia , 1986; ^Quigrtar d & p raS j 1936;24 Nielsen , 1986a; ^Nielsen , 1986b; 2e Quer o ef al„ 1986;2 "Caruso , 1986, Pojavljanj e pridneni h vrs t 1. Mai a sip a (Sepia elegans Siainviile , 1 827} Posamezn e mal e sip e so bite v poletni h vzorcih , o d junij a d o septembra {tabela 3). Tud i v vzorci h Boijet a (1992 ) mal e sip e v zimske m času ni bilo, iz česar sklepam, da se pojavlja le v toplejšem delu leta, 2. Navadna sipa (Sepia officinalis Linnaeus, T 758) Navadne sipe so bile v spomladanskih, poletnih in jesenskih vzorcih, in sicer od aprila do junija, od septembra do oktobra 1995 in od aprila do septembra 1996 (tab. 3), Občasno pojavljanje navadne sipe v vzorcih si razlagam z uporabo prelahkih PPM. Po na­vedbah ribičev se Število sip poveča v zimskem in spo­mladanskem času, kar je venetno povezano 2 njihovo selitvijo proti obalnim območjem, kjer naj bi se spo­mladi in poleti drstile (Bolje, 1992). Navadna sipa se na obravnavanem območju :verjetno pojavlja vs e jet0 Dolžina plaSča: 72 mm (39-117, 50*26, NMO). Bosan MARČETA: COJA VI ) A N JE NEKATERIH VRST CLAVONOŽCE V !N SI8 V SLOVENSKEM MORIU, 1 7-JO 3. Bodičasta sipa (Sepia orbignyana Ferussac, 1826) Po eno bodičasto sipo smo uloviii 22. 8. 1995 in 10. 4. 1996 {tab. 3). Avgusta smo bodičasto sipo ulovili severozahodno od Piranskega zaliva, aprila pa severo­zahodno od Koprskega zaliva. 4. Sipica (Sepiola sp.) Posamezne sipice so bile v spomladanskih vzorcih (tab. 3) na območjih vseh treh transektov. Bolje (1992) je imel v ulovih vrsto Sepiola rondeleti, ki je bila v vseh vzorcih redka, v februarskih vzorcih pa je ni bilo. 5. Pritlikavi ligenj (Alloteuthis media (Linnaeus, 1758)) Pritlikavi ligenj se je pojavljal vse leto, največje število osebkov pa je bilo od zgodnje jeseni clo pozne pomladi (tab. 3). Zaradi majhnosti je bilo število pritli­kavih lignjev v ulovih vselej podcenjeno, Dolžina plašča: 56 mm (15-166, SD=17, N-152). 6. Navadni ligenj (Loligo vulgaris Lamarck, 1798) Navadni ligenj se je pojavljal vse leto (tab. 3), v več­jem številu pa konec poletja in jeseni (slika 2). Največji delež biomase vzorca so lignji dosegli novembra (35%), ko je bil največji tudi delež osebkov (21%). Zaradi polpeiaškega načina življenja je bilo število lignjev v vzorcih verjetno podcenjeno. Dolžina plašča: 109 mm {33-405, SD-59, N=425). 7. Navadna hobotnica {Octopus vulgaris Cuvier, 1797) Eno navadno hobotnico smo ulovili 18. 9. 1995 severozahodno od Koprskega zaliva. Ulov hobotnice s PPM je prej izjema kot pravilo, saj se hobotnica na­vadno zadržuje bližje obali, 8. MoŠkatna hobotnica (Eiedone moschata (Lamarck, 1799)) Moškatna hobotnica se je pojavljala vse leto (tab, 3), Njena abundanca in biomasa sta bili največji v poletnih in jesenskih mesecih (slika 3). Največji delež biomase v vzorcih je moškatna hobotnica dosegla julija (41%) in septembra 1995 (44%), medtem ko je bi! njen delež leta 1996 največji avgusta (31%). Dolžina plašča: 80 mm (35-140, 5D=17, N-297). 9. Navadni morski pes (Mustelus mustelus (Linnaeus, 1758)} Navadni morski pes se je pojavljal v toplejših me­secih (slika 4, tab. 3). Takrat se je zgodilo, da so ribiči z enim potegom zajeli tudi do nekaj deset osebkov, med­tem ko v drugih potegih navadnega morskega psa ni bilo ali pa so bili le posamezni osebki. Delež biomase na­vadnega morskega psa je bil največji avgusta 1995, ko ie dosegel 41 odstotkov ulova. Naslednje leto je bil največji delež biomase navadnega morskega psa v juniju, ko je dosegel 14 odstotkov. Odsotnost navadnega morskega psa v vzorcih, dobljenih v hladnejšem delu leta, si razlagam z manjšim številom osebkov in premajhnim številom opravljenih vzorcev. Glede na to, da je Bolje (1992) navadnega morskega psa ulovil tudi pozimi, me­nim, da se vrsta pri nas pojavlja vse leto. Celotna dol­žina: 379 mm (278-805, SD-'i 21, N = 25). 10. Zvezdasta raža (Raja asteria s Delaroche, 1809) V obeh letih smo zvezdasto ražo ulovili junija (tab. 3) v območju severozahodno od Piranskega zaliva, Obakrat smo uporabili težjo PPM, kar je verjetno vzrok, da zvezdaste raže ni bilo v drugih vzorcih. Verjetno se, podobno kot druge ribe hrustančnice, tudi zvezdasta raža pojavlja v toplejših mesecih. To potrjujejo tudi rezultati Boljeta (1992), ki je zvezdasto ražo ulovil samo julija. 11. Morski bič (Dasyatis pastinaca {linnaeus, 1 758)) Enega morskega biča smo ulovili dne 21. 8. 1996. V takratnem ulovu je bilo tudi več morskih golobov in navadnih morskih psov, iz česar sklepam, da se posa­mezni morski biči pojavljajo skupaj z drugimi vrstami hrustančnic. 12. Morski golob (Myiiobatis aquila (Linnaeus, 1 758)) Morskega goloba smo ujeli v drugi polovici poletja in zgodaj jeseni (slika 5, tab. 3). Njegovo pojavljanje se je v glavnem ujemalo s pojavljanjem navadnega mor­skega psa. Največji delež biomase v ulovu je morski golob dosegel avgusta 1995, ko je dosegel 9 odstotkov. 13. Ugor (Conger conger ([Artedi, 1738] Linnaeus, 1 758)) Enega ugorja smo ulovili dne 24. 4, 1995 severo­zahodno od Piranskega zaliva. Po navedbah ribičev ugorja pred letom 1994 ni biki v ulovih s PPM, leta 1994 in 1995 pa so pogosto ulovili posamezne osebke. 14. Veliko morsko silo (Syngnathus acus Linnaeus, 1758} Eno veliko morska šilo smo ulovili dne 21. 8. 1996, Po navedbah ribičev se posamezni osebki velikega mor­skega šila občasno ulovijo v PPM. Bojan M AR ČE i'Ar POJAVLJANJE NEKATERIH VRST GlAVONOŽCEV IN RIB V SLOVENSKEM MORJU, 17-30 Slika 2: Abundanca (o) in biomasa (x) lignja (Loligo vul­garis Lamarck, 1798) na območju ribolova s pridneno povlečno mrežo v slovenskem morju (os = število osebkov). Fig. 2: Abundance (o) and biomass (x) of Common Squid (Loligo vulgaris Lamarck, 1798) caught with bot­tom trawling gear in the Slovene part of the Adriatic (os -No. individuals). iCTlCT» tfl ? ? ! j 1 S S IS ^ ® «6 «j ii'n'N » K e ii 8 « dnav: Slika 4: Navadni morski pes (Mustelus mustelus (Lin­naeus, 1758)). Fig. 4: Smoothhound (Mustelus mustelus (Linnaeus, 1758)). Slika 3: Moškatna hobotnica (Eledone moschata (La­marck, 1799)), Glej podnapis pod sliko 2 za razlago. Fig, 3: Musky Octopus (Eledone moschata (Lamarck, 1799)) (see fig. 2 for explanation). ILp t-v*(0 1758). Slika 13: Bukva (Boops boops (Linnaeus, 1758)). Fig. 12: Red Mullet (Mullus barbatus Linnaeus, 1758). Fig. 13: Bogue (Boops boops (Linnaeus, 1758)). » s $ SUka 14: Spar (Diplodus annularis (Linnaeus, 1758)). Fig. 14: Annular Sea Bream (Diplodus annularis (Linna­eus, 1758)). Slika 16: Menola (Spicara flexuosa Rafmesque, 1810). Fig. 16: Menola (Spicara flexuosa Rafmesque, 1810). Slika 15: Ribon (Pagellus erytbrinus (Linnaeus, 1758)). Fig. 15: Common Pandora (Pagellus erytbrinus (Linna­eus, 1758)). 303 î 2C0 t 150 C3 II » os o!jan, Tv 1965, Ribe jadrana. Zavod za izdavanje ud2benika SR Srbije, Beograd, pp. 1-451. Štirn, J, & Bolje, A., 1989, Fondi pridnenih rib in drugih užitnih organizmov obalnih vod SFRJ v Tržaškem zalivu. Zaključno poročilo. Raziskovalna naloga. Droga Portorož in iBU, MBP, Ljubljana, Piran, pp. 1-243. Tortonese, E v 1986a, Serranidae. V: P. j. P. Whitehead, M. -L. Bauchot, j. -C. Hureau, j. Nielsen & E. Tortonese (uredniki), Fishes of the North-eastern Atlantic and the Mediterranean. Vol. II, UNESCO, UK, pp. 780-792 Tortonese, E v 1986b, Cepolidae. V: P. j. P. Whitehead, M. -L. Bauchot, J. -C. Hureau, j. Nielsen & E. Tortonese (uredniki), Fishes of the North-eastern Atlantic and the Mediterranean. Vol. 1!, UNESCO, UK, pp. 810-811. Tortonese, E., 1986c, Centracanthidae. V: P. j. P. Whitehead, M. -L. Bauchot, j. -C. Hureau, j. Nielsen & E. Tortonese (uredniki), Fishes of the North-eastern At­lantic and the Mediterranean. Vol, II, UNESCO, UK, pp. 908-911. Tortonese, E., 1986d, Trachinidae. V: P. J. P. White­head, M. -L. Bauchot, j. -C. Hureau, J. Nielsen & E, Tortonese (uredniki), Fishes of the North-eastern Atlantic and the Mediterranean. Vol. II, UNESCO, UK, pp. 951­ 954. Vukovič, A., Lipej, L., Mozetič, P., Planine, R., Turk, V., 1995, Program spremljanja kakovosti obalnega morja v Republiki Sloveniji. Poročilo za leto 1994. NI8, M8P Piran, Ljubljana, Piran, pp. 1-8. Whitehead, P. J. P, 1989a, Clupeidae. V: P. j. P. Whitehead, M. -L. Bauchot, j. -C, Hureau, j. Nielsen & E. Tortonese (uredniki), Fishes of the North-eastern At­lantic and the Mediterranean. Vol. I, UNESCO, UK, pp. 268-281. Whitehead, P. J. P, 1989b, Engraulidae. V: P. j. P, Whitehead, M, -L. Bauchot, J. -C. Hureau, j, Nielsen & E. Tortonese (uredniki), Fishes of the North-eastern At­lantic and the Mediterranean. Vol. I, UNESCO, UK, pp. 282-283, Whitehead, P. J. P., Bauchot, M. -L., Hureau, j. -€., Nielsen, J., Tortonese, E. (eds.), 1989, Fishes of the North-eastern Atlantic and the Mediterranean. Vol, I. Unesco. Whitehead, P. ). P., Bauchot, M. -L., Hureau, J. -C , Nielsen, J., Tortonese, E. (eds.), 1986a, Fishes of the North-eastern Atiantic and the Mediterranean. Vol. /i. Unesco. Whitehead, P. J. P., Bauchot, M. -L., Hureau, j. -C., Nielsen, J., Tortonese, E. (eds.), 1986b, Fishes of the North-eastern Atiantic and the Mediterranean. Vol. III. Unesco, original scientific paper UDK 597.5:591,13(262.3-1 1) FOO D AN D FEEDING HABITS O F THE DAMSELFiSH CHROMIS CHROMIS (TELEOSTEI: POMACENTRIDAE) IN THE EASTERN ADRIATI C Jakov DULČiČ Ph.D., fisheries biologist, Institute of Oceanography and Fisheries - Split, HR-21000 Split, Set. i, Meštroviča 63 dr., ribiški biolog, !OR, HR-21000 Split, Set. 1. Meštroviia 63 ABSTRACT The stomach contents of 964 damseifish Chromis chromis collected in the eastern central Adriatic in 1992 and 1993 were examined to assess the diet, as influenced by season and fish size, Damseifish is carnivorous from the juvenile stage onward, feeding on a narrow range of plankton and benthic prey items, Higher intensity of feeding activity in spring could be related to temperature and/or gonadal maturation. During all seasons copepods constituted the most important food resource by weight, number and frequency of occurrence. Appendicularia and cladocerans were the second most important food category. Dietary overlap was relatively high, indicating that the feeding spectrum of damseifish changed little across seasons, but for size groups was small, indicating greater changes in feeding spectrum. Ključne besede: črnik, Chromis chromis, prehrana, prehranjevalne navade, ceponožci, vzhodni Jadran Key words: damseifish, Chromis chromis, food, feeding habits, copepods, Eastern Adriatic INTRODUCTION Despite its abundance, very little is known about the trophic ecology of damseifish in the Mediterranean Sea. The damseifish, Chromis chromis {Linnaeus, 1758) is The present study deals with food and feeding habits of a small fish found in shoals in mid-water above or near the damseifish off the Eastern Adriatic. The purpose was rocky reefs or above sea grass (Posidonia) meadows at to examine the feeding habits and intraspecific resource depths ranging from 3 to 35 m. It occurs in the partitioning across seasons and during developmental Mediterranean and from Portugal southwards to Angola life stages of damseifish in the Eastern Adriatic. (Quignard & Pras, 1986). In the Eastern Adriatic, the damseifish is abundant MATERIAL AND METHODS (Grubišič, 1982; Milišič, 1994), but it is of no commer­cial value along the eastern coast (except on the central A total of 964 specimens of damseifish were ob-Adriatic islands of Solt.a, Hvar, Korcula and Lastovo, tained during four seasonal beach seine survey cruises, where it is much appreciated). In coastal fishery of Dal-from summer 1992 to spring 1993. Samples were taken matia, damseifish form a small but significant compo-near the island of Trstenik in the central Adriatic (Fig. 1}. nent of the coastal beach seine and gill net catch that is Damseifish were fixed in 4% formalin immediately after used as delicious food and as bait for lobsters. We have capture. The fish were processed promptly after no new data on catch, but. Grubišič (1982) reported that collection. Processing included measurements and it is around 30 tons per year. weighing to nearest 0.1 cm and 0.01 g respectively and There are some data about the biology and ecology gut removal prior to which both ends of the stomach of this species from the eastern Adriatic. Dulčič et at. were tied off. The contents of the dietary material were (1994a) presented data on the length-weight relationship identified to the specific level where possible, but most in damseifish during spawning in the Eastern Adriatic. items were identifiable only to the generic level. Pres­Dulčič et al. (1994b) analysed the vertebra! number of ence of inorganic matter and detritus in the stomachs damseifish. Age, growth and mortality of damseifish was recorded, but excluded from the analysis. After were presented by Dulčič & Kraljevič (1995). identification, preys were weighed to the nearest 0.01 g. Jakov DULČl C FOO D AN O FEEDING HABITS O f TH E DAMSELEISH, ..., 31-36 Fig. 1: Location of sampling station in the eastern central Adriatic, where damselfish (Chromis chromis) were collected (Trstenik Island). Slika 1: Zemljevid obravnavanega območja z označeno vzorčevalno postajo (otok Trstenik), kjer so bili ulovljeni črniki (Chromis chromis)> The contribution of the prey categories to (he diet of damselfish was calculated as (1) the percentage of wet weight (Cw) of a prey category (pooled) to the weight of the total stomach contents, (2) the percentage abun­dance (Cn) of individuals of a prey category to the total number of prey individuals in the stomachs, (3) the fre­quency of occurrence (f) of stomachs in which a prey category occurred to the total number of stomachs ex­amined (Hyslop, 1980). George & Hadley (1979) em­ployed the "relative importance index" (Rl) which is based on the "absolute importance index" (Ai) as fol­lows: Al = % frequency occurrence + % total numbers + % total weight; Rl = 100 Al / niL A[, where n is the number of i different food types. Seasonal variations were analyzed using Fischer's least significant difference (LSD) test (Zar, 1984). The analysis of changes in feeding habits in different seasons and in different length classes was performed by the use of the full ness index (Hureau, 1970): %jr = fullness in­dex: weight of digested food/fish weight x 100. Proportional food overlap between size classes and seasons for the species was calculated using the overlap index of Schoener (1970): Cih = 1-0. 5 ® Pij - Phj), where Pij and Phj are the proportions of prey j found in the diets of groups i and h respectively. This index has a minimum of 0 (no overlap of prey) and a maximum of 1 (all items in equal proportions). Schoener's index values above 0.60 are usually considered to be "biologically significant" (Zaret & Rand, 1971; Wallace, 1981), in­dicating a high dietary overlap (Langton, 1982). RESULTS AND DISCUSSION Fish lengths in the sample ranged from 8 to 1 34 mm caught (Fig. 2). Data sampled in 3 areas were aggre­gated for the analysts since there was no significant dif­ference between them (ANCOVA). The specimens were divided into two size groups, to examine feeding habits of the fish developmental stages. Group 1 comprised fishes smaller than 65 mm (juvenile stage) and Group 2 fishes longer than 65 mm (adult stage). The proportion of empty stomachs among fish up to 65 mm long is 6.9%, while this proportion in longer fish is 5.0%. Feeding intensity expressed by the fullness index (jr) was higher in smaller (jr—6,83) than in larger fish (Jr-3.80). In Group 1, polychaetes, ostracods, copepods and mysids constitued the bulk of the diet, while copepods, appendicularins and ciadocerans were dominant in Group 2 (Table 1). Stomachs of larger individuals con­tained ail mentioned prey taxa ingested by smaller fish, but in different proportions. Copepods were the do­minant prey of damselfish in both size-classes, Clause-ca/anus pergens being the dominant species. As fish grew older there was a difference in the "relative index" (Rl) of polychaetes, copepods, ostracods and mysids. Polychaetes exhibited a greater presence in the sto­machs of smaller fish, corroborating the view that small damselfish select prey of low mobility. n — nI I t n H Í1 J—ill | ' ' i 'Hnn ] I | 1 L-^^f.,,,,^ , I 1 L .1 — r | ^ t M 30 tO 51 SO » SO <13 )CC !!0 IÎD 130 UG TOTAL LEfv&lH [mm) Fig. 2: Length frequency distribution of damselfish (Chromis chromis) collected in the eastern central Adriatic for dietary studies in 1992 and 1993 (n = 964). Slika 2: Velikostna porazdelitev dolžine črnikov (Chro­mis chromis), ulovljenih v vzhodnem srednjem Jadranu v obdobju 1992-1993 (n = 964). ANNALES <>/'96 lakov PUlClČ : FOO D AN D FEEDING HASH'S O f TH E DAMSELFISH, ., H (-3 6 Siz e groups m m > mm SeJ'.tm Winter Summer Con ! rib lit ion of the f A I Ri f A l RI O/ntnb'.itli-yn 17.t the ( At RI f C w C « C-w ci 5 c w C, v At RI prey allegorie s prey categories Polych.ieta 34.3 7.7 30. S 72,S 13.03 2 4 0.1 0.5 3 0.25 Poiydwt a 1-1,1 0.2 1 ,3 15.6 2.49 Appendicular « 76.2 27 13.8 117 9,93 Appendicular ia 53.8 22.1 2.7.5 103.-1 19.72 83.6 32.) 16.7 138,4 22,1! Ostracocla 3(1.9 27,4 19,5 85.8 15.<12 10.8 0.3 3.2 14.9 1.27 Osiraearb 11.5 0.0 3.2 15.5 2.48 Copepocta 94.7 55,6 12.7 163 29.30 93.1 37 7 2T..7 156.5 13.29 Copepocta 100 58.2 33.8 192 36.61 75.6 34.2 24 6 134.4 21.SO Paracalanus parvus 76.2 7.6 SA 89.2 7.57 Ckripedia truiuplii) 3.7 0.7 2 6.4 1 .02 Claiisocatanus per gem 36.8 23 S 3 65.1 11.70 51.7 10,1 6.1 67.9 5.77 Decapods (iarvae) 25.2 5.6 7.4 38.2 6.10 C. furca(us 21.1 15 3.4 39.5 7.10 37.5 6,2 4.3 47.6 4, M iViy.^ddi-.ej 6.2 0.2 2.1 8.5 1.36 C.helgolandictis lî. G 1.1 I. I 13.8 5.17 Cbdocer a 100 12.7 26.8 139.5 26.tO »4.1 22.4 12 i 18.5 18.9.3 Cparapergens l 5,6 5,2 2.9 23.7 2.01 Gastropoda 11.8 0.9 17 29.7 47 4 C.tetwicvrnis 19 TO.S 2,-4 31.9 5.73 3.3 0.1 0.1 3.5 0.30 (larvae) Eitcaliinus efangatus 1 OS 5 1.2 16 7 3 2.3 0.1 0.1 2.5 0.21 Sivatvia (larvae) S.9 0.9 7.3 (4.1 2.2.5 Eulerpina acutiformte 65 mm % of empl y stomachs 6.9 5.0 % Jr 6.83 3.80 Table 1: Contribution of the prey categories for dam-Table 3; Fullness index (Jr) in specimens analyzed by selfish stomach contents according to size groups. seasons. Tabela 1: Delež posameznih kategorij plena v želodcih Tabela 3: Hureaujev indeks (Jr) primerkov; raziskanih v črnika glede na velikost. različnih letnih časih. 33 jakov DULÔC : FOO D AN D FEEDING HABITS OF THE DAMS ELFISH 31-36 Season Winter Spring Summer Autumn Winter 0.70 0.67 0.93 Spring 0.80 0.71 Summer 0.69 Autumn Size group 8 - 65 mm > 65 mm 8 - 65 mm 0.58 > 65 mm Table 4: Proportional food overlap coefficients (Scho­ener index) of damselfisb between seasons. Tabela 4; Količnik prekrivanja v prehrani (Schoenerjev indeks) črnika v posameznih letnih časih. Feeding intensity was lowest in winter, indicated by the higher frequency of empty stomachs in each group {14% for Croup 1 and 11 % for Group 2). Copepods constited the bulk of diet throughout the year (Table 2), exhibiting their highest values by number during spring and summer. Cladocerans and Appendicu­lar ia were the second important food categories. They were eaten regularly during all seasons. Seasonal changes in Rl were examined to detect which prey accounted for the differences in the diet, This analysis indicated a great importance of copepods in all seasons. Food quantity in analyzed guts, expressed as the fullness index (Jr), was highest in spring (jr = 5.67) and a significant drop was recorded for winter (Jr = 1.91) (Table 3). Fischer's LSD test indicated that the mean fullness index was significantly higher in spring and summer. The application of ANOV A and multiple range tests to the seasonal data indicated significantly higher values in spring (ANOVA: F = 12.424, P <0.001). Values of Schoener's (1970) index of dietary overlap were obtained from a comparison (by weight) between the different size groups (0.58) and seasons (Table 4), Almost all the values were > 0.60, indicating high die­tary overlap. Thus, the feeding spectrum of damselfish depends little across season of capture. The small vari­ations of the principal prey items between the different seasons contributed to the high level of inter-season proportional overlap. Damselfish in the eastern Adriatic fed primarily on crustaceans, mostly copepods (such as Paracalanus parvus, Clausocalanus pergens and Centropages typicus) and cladocerans (Podon intermedius), but also con­sumed Appendicular!», Gastropoda (larvae) and Bivalvia (larvae), fish eggs and fish larvae, mainly at larger lengths. Polychaetes, Ctrripedla (nauplii), Mysidacea and Decapoda (larvae) were also occasionally found in the stomachs. These results are generally in accordance with the observation of Duka & Shevchenko (1980) off the Mediterranean coast of island Lampedusa and for damselfish from the Black Sea. Same authors mentioned that copepoda (Calanoida, Cyclopoida - 15 species) were the most abundant food items, that Appendicularia (Oikopleura dioica) ranked second in the Mediterra­nean, and that damselfish eggs and Appendicularia (Oikopleura dioica) were the most abundant food items in the Black Sea. Although no quantitative data on prey consumption of damselfish were given, it is not possible to compare the data on that basis. Mapstone & Wood (1975) revealed that, damselfish feeds both on plank­tonic. and benthic organisms; eight out of 11 individuals contained predominantly planktonic and three pre­dominantly benthic organisms in the Azores. The stomachs of both size groups were significantly fuller in spring and summer, while the lowest feeding intensity coincided with winter. Many factors could re­sult in the reduction of feeding activity in fish (Nikolsky, 1976). Many of the demersal fishes show a decrease in the feeding rate as the temperature drops (Tyler, 1971), In the study area, the lower temperature of the water oc­curs during winter (February) and beginning of spring (Zore-Armanda et. ah, 1991). Because of the reduced abundance of prey and the lowered metabolism of the fish, predation on plankton and benthos was probably at a minimum during winter. Regner (1985) presented, for the central Adriatic, that copepods showed larger num­ber of annual maxima predominantly during the warmer part of the year: in spring, summer and autumn. This oc­currence of a larger number of maxima may be due either to natural fluctuations or to the enrichment of coastal area by nutrients (eutrophication) as well as to the sufficient food available over a larger part of the year. Favourable environmental conditions during the warmer months and abundant food supply support the expanded fish community without competitive interac­tions. However, the effect of temperature may be con­founded with the effects on other abiotic factors and/or in change in food availability (Worobec, 1984). Warren & Davis (1967) discussed the profound effects of tem­perature and seasons on food consumption rates, More food is consumed in summer than in winter, this was demonstrated (Davis & Warren, 1965) from the experi­ments with Coif us perplexus. Reproduction, which takes place at the end of spring and during summer (Duičič & Kraljevič, 1995), seems to have effect on feeding intensity (gonadal maturation). Feeding behaviour of most of fish species considerably oscillates during the year as a consequence of a physi­ological changes during reproduction, jardas & Pallaoro (1991) found that feeding intensity of Scorpaena porcus expressed by the index of gut fullness showed markedly lower values during spawning, whereas it was at almost the same level during the rest of the year, with slight in­tensity increase in the postspawning period. Similarly to damselfish, high degrees of stomach fullness were re­ported for other demersal fish in the same area, such as |,ikov DtJlCl é FOO D AN D FEEDING HABITS O f THE DAMSELFISH, ,.., 31-M fig. 3: School of Damselfish (Chromis chromis) (Photo: M. Richter). Slika 3: fata irnikov (Chromis chromis) (Foto: M. Richter). Scorpaena porcus (jardas & Pallaoro, 1991), indicating an abundance of food in this region even though this region contributes to oligotrophy area according to Buijan & Zore-Armanda (1976), The abundance of food in this region is connected with the upwelling in the area of Palagru^a sill which is in vicinity of the studied area (Regner ef a/,, 1987), This occurs certainly more strongly during years with increased Mediterranean in­flow at the time of strong advection of the intermediary water and also during the upwelling periods in spring and summer (Buijan, 1965). In the open central Adriatic the zooplankton (dry weight) shows a distinct spring maximum in March and April (Vufietid, 1973). Upwel­ling may be caused later in the spring-summer period by dominant coastward wind direction (the maestrai). The spring maximum of the zooplankton is characterized by the presence of typical deep sea species; the maximal population densities at the beginning and by the end of summer are attained by the typical neritic species (VuCetiC, 1 973). The maximal quantities of zooplankton occurs firstly in the open sea and then farther towards the coast. Dietary overlap is lower between summer and win­ter, when the metabolic demands are higher than for the rest of the year. This fact indicates that intraspecific competition for food between fish of the two groups is small, probably because of the different bathymetrical distribution of damsetfishes at different size. The study of the bathymetrical distribution of the two groups revealed that younger specimens tended to inhabit smaller depths (DulCic, unpublished data), Fig. 4: Male and female damselfish. The male is waiting for the proper moment to fecundate the eggs (Photo: M. Richter). Slika 4: Samec in samica črnika. Samec čaka, da se samica umakne, da lahko oplodi !zmetana jaca (Foto: M. Richter). POVZETEK Črnik Chromis chromis (Linnaeus 1758) je majhna riba, ki jo najdemo v plitvih vodah nad ali v bližini čeri ali pa nad travniki morske trave pozejdonke (Posidonia oceani ca), in sicer v globini od 3 do 35 metrov. Živi v Sre­dozemskem morju in v vodah južno od Portugalske do Angole (Quignard & Pras 1986). V vzhodnem Jadranu ječrni k številčen (Crubišič, 1982; Milišič 1994), vendar tam komercialno ni zanimiv (razen na otokih Šol ti, Hvaru, Korčuli in Lastovem v srednjem Jadranu, kjer je zelo cenjen). V dalmatinskem obalnem ribištvu so črniki majhen, a pomemben sestavni del ulova z mrežami, uporabni predvsem kot slastna jed in vaba za jastoge. Da bi ocenili, s čim se črniki prehranjujejo glede na različne letne čase in velikost, je bila raziskana vsebina želodcev 964 osebkov, ujetih v vzhodnem srednjem Jadranu v letih 1992 in 1993. Črnik je mesojeda riba že od svojega mladostnega stadija naprej, hrani pa se le z določenimi planktonskimi in bentoškimi organizmi. Večjo prehranjevalno intenzivnost v spomladanskem času bi lahko pripisali temperaturnim spremembam in dozorelosti Jakov OULČiČ : K>O D AN D FEEDINC HABITS OF "J H F DAM5FEF1SH, ..., 31-36 spolnih žlez. Po biomasi, številu in pogostosti pojavljanja v celoletnem obdobju so bili ceponožci najpomembnejši vir hrane. Drugi najpomembnejši prehranjevalni vir so bili repati plaščarji in morske bolhe. Prehransko prekrivanje je bilo razmeroma izrazito, kar pomeni, da so razlike v prehranjevalnem spektru črnikov prek vseh štirih letnih časov majhne, medtem ko je bilo za velikostne skupine neznatno, kar kaže na večje spremembe v prehranjevalnem spektru. REFERENCES Buijan, M. (1965) Anomalies of temperature and chlonnity of sea water on the station StonCica (middle Adriatic}. Pomorski zbornik 6: 949-995. Buijan, M. & Zore-Armanda, M. (1976) Ocea no-graphical properties of the Adriatic Sea, Oceanogr. Mar. Biol. Ann. Rev. 14: 11-98. Davis, G.E. & Warren, C.E. (1965) Trophic relations of a sculpin in laboratory stream communities. /, Wildl. Mgmt. 29: 846-871, Duka, L.A, & Shevchcnko, N.F. (1980) Morphology and nutrition of Chromis chromis (Linne) in the Medi­terranean and Black Seas. Ekhol. Morya 3: 26-33. (in Russian) Dulcic, J., Kraijevic, M. & Cetink, P. (1994a) Length-weight relationship in damselfish (Chromis chromis L. 1758) from the eastern Adriatic during spawning. 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