ANNALES • Ser. hist nat. 10 2000 • 2 (21) original scientific paper UDC 597.3(2623-17) received; 29. 11. 2000 OCCURRENCE OF THE BASKING SHARK, CETORHINUS MAXIM US (GUNNERUS, 1 765), IN THE WATERS OFF PIRAN (GULF OF TRIESTE, NORTHERN ADRIATIC) Lovrenc UPE!, Tihomir MA KO VEC & Martina ORLANDO Marine Biological Station, National institute of Biology, Si-6330 Piran, Parnate 41 Valier ¿IZA Piran Aquarium, 51-6330 Piran ABSTRACT Two juvenile basking sharks (Cetorhinus maxirnus) were accidentally caught in the waters off Piran, Slovenia, in the summer of2000. One specimen was entrapped in special nets for small sharks (Musteius), while the other was caught in a flatfish net Some information about the data on this shark species is dealt with in this article. Key words: Cetorhinus maximus, basking shark, occurrence, Gulf of Trieste, Northern Adriatic RITROVAMENTO DELLO SQUALO ELEFANTE, CETORHINUS MAXIMUS (GÜNNERUS, 1765) AE LARGO DI PíRANO (GOLFO DJ TRIESTE, NORD ADRIATICO) SiNTESi Due g i ova ni esemplari di squab elefante (Cetorhinus maximus) sono statt accidentalmente catturati al largo di Pirano, Slovenia, ne!¡'estate del 2000. I! primo esemplare è rimasto intrappolato in speciaü reti per piccofi squafi (Musteius), montre il secundo è stato catturato con la rete per sogiiole e passere. Nell'articolo vengono presentati alcuni da ti inerenti questa specie di squalo. Parole chiave: Cetorhinus maximus, squalo elefante, ritrovamento, Slovenia, Nord Adriático 211 ANNALES • Ser. hist. nat. 10 • 2000 • 2 (21 ) (.ovfcnc UP£| a;.: OCCURRENCE Of THE BASKING SHARK. CfTORIilNUS MAX/MUS {CUNNERUS, l/f>S), IN THF WATERS OFF PI RAW INTRODUCTION The basking shark Cetorhinus maximus (Gunnerus, 1765} is the biggest Mediterranean shark (Fig. 1 ), for it can reach more than 9 m in length, according to some authors even more than 15 m (Quéro, 1984). It is a typical pfanktivorous shark, actively foraging to locate productive zooplankton patches (Sims & Merrett, 1997). in the Adriatic Sea, the basking shark is considered to be a relatively rare and occasional species (jardas, 1996). According to some of the available reports from the 19ln century (Naccari, Nardo, Mertens, Perugia, Ninni, Trois, Doderlein, Faber, Brusina, Stossich, Valle), this species was considered to be quite accidental in the Adriatic at that time as well (Brusina, 1888, Bartul & Mate, 1999) At least 30 records on the occurrence of the basking shark have been published to date in the scientific literature as caught or sighted in the eastern part of the Adriatic, but the bulk of them have been made during the 20th century (Soldo & jardas, 2000). Compagno (1984) considered this shark Jo be more vulnerable to overfishing than other shark species. According to the UK Basking shark Proposal of the Department of the Environment, Transport and the Regions (www.wildlife-c.ountryside.detr.ROv.uk/gwd/shark), the basking shark has been subjected to unsustainable fisheries, which resulted in population collapse in the last decades. Basking shark is included in the list of animal species in the Slovenian Decree on Protection of Threatened Animal Species (1993). This shark also appears in the List of endangered or threatened species in the Mediterranean according to Annex II in the new SPA protocol (UNEP(OCAj/MFD WG. 149/3)). The present article Is our contribution to the Slovenian ichthvological bibliography, which happens to be extremely scarce as far as shark data are concerned. METHODS Basking sharks were measured and photographed immediately aftet the fishing boat clocked in the Piran harbour. Body measurements were taken with hand meter to the closest cm according to the guidelines by Compagno (1984) [Fig. 2). Unfortunately, both specimens were sold at the fish market in Piran. The collection of photographs of both juveniles Is kept at the Marine Biological Station in Piran. RESULTS AND DISCUSSION On May 22ncl 2000, a juvenile male basking shark was C3ught in a special "cagnolara" net for small sharks (mainly species from the genus Mustelus) in the waters some 7 nm NW off Piran (Fig. 3). it was 299 cm long and weighing approximately 120 kg. After some minutes of exposure, the fish was cut by fisherman into pieces and sold at the Piran fish market. On July 19'" 2000, another male basking shark was caught with a special "passaiera" flatfish net in the waters 6.4 nm off the town of Piran (Fig. 4), The shark was accidentally entangled in the net and successively transported to the Piran harbour, where it was sold at the fish market. This shark was 249 cm long and weighed approximately 70 kg. The data on morphometry measurements of both specimens are presented in table 1. f ig. ): Basking shark Cetorhinus maxirnus (Drawing by A. De Maddalena). SI. t : Morski pes orjak (Cetorhinus maxirnus} (Risba: A. De Maddalena). '! I 1 1 — ANNALE S • Ser, hist. nat. 10 2000 2 (21) Lovrenc LlPEI if al.- OCCURRENCE OF THE BASKING SHARK. CETORHiNVS MAXIMU5 (GtfNK'ERiJS, 1765J, IN THE WATERS Off PIRAN .... 211J16 Tab. 1: Biometric measurements (in cm) of two juvenile basking sharks caught in the Gulf of Trieste in May (1) and fuly 2000 (2). Tab. 1: Biometrične meritve (v cm) dveh ujetih mladičev morskega psa orjaka v Tržaškem zalivu maja (1) in julija 2000 (2). Morphometric characteristics (cm) 1 j 2 1. Total length 299 249 2. fork length 254 - 3. Precaudal length 236 195 4. First dorsal length 29 25 6. First dorsal anterior margin 32,5 26 5 First dorsal height 26 21 7. Second dorsal length 9 9 8. Second dorsal anterior margin 11 10 9. Second dorsal height 10 7 10. Dorsal caudal margin 63 55 11, Pectoral anterior margin 43 38 12. Pectoral posterior margin 28 21 13. Pelvic anterior margin - 16 14. Pelvic length 23 20 15. Pelvic height 23 14 16. Anal anterior margin 9 17. Anal length - 5,5 18. Anal height - 6 The size of the newborn basking sharks is unknown and the smallest recovered specimen measured 165 cm (Compagno, 1984). By comparing our data with the data of Izawa & Shibata (1993), the smaller specimen in our study could be estimated as approximately 6 months old. Juveniles below 3 m were reported to be extremely rare in the scientific literature (sensu Compagno, 1984). At least six other juveniles (250, 265, 310, 320, 350 and 392 cm) have been previously reported according to the up-to-date records of basking sharks in the Adriatic Sea (Soldo & jardas, 2000). One of these juveniles, the 3.92 m specimen, was also caught in the small "passalera" net used for flatfish about 400 metres off the coast of Trieste (Bussani, 1974). Sims el al. (1997) reported that basking sharks smaller than 3 m in size occurred in the summer. Bigger specimens were more frequent in springtime in the waters off Plymouth, directly after the increase of zooplankton density in May. According to Bussani's report (1986) on the Ichthyo-t'auna of the marine sanctuary Miramare near Trieste, these sharks are quite often caught in flatfish nets. It is interesting that the gut dissection of a 6m long shark caught in the sanctuary and referred to in his report (unfortunately no data regarding the year of the capture and others details of the shark were mentioned) proved that, the basking shark feeds on small cfupeids (Sprattus sprattus). in May 1991, Roberta Odonco (pers. comm.) observed, at the very same locality off Miramare, a 6 m long basking shark feeding on a huge school of Aiherina spp. 17 Fig. 2: Morphometric measurements (sensu Compagno>, 1984). St. 2: Morfometrične mer/fve (priv/ete po Compagno, 1984). 213 ANNALES Ser. hist. nal. • 10 • 2000 • 2 <21) Lovienc tIPtf« OCCUftMN-CE OF THE BASKING SHARK. Ci70»f«NUS MAXtMVS «iONN£ftUS. i IN THE WATERS OFF PIRAN .~,2J1-2M. Tab. 2: Some recent records of the basking shark in the Adriatic (Legend: GT - Gulf of Trieste, NA - Northern Adriatic, MA - Middle Adriatic, SA - Southern Adriatic). Tab. 2: Novejši podatki o pojavljanju morskega psa orjaka v Jadranskem morju (Legenda: GT ■ Tržaški zaliv, NA -severni Jadran, M A - srednji Jadran, SA - južni Jadran). V ear Locus Area Length (cm) Source 1 968 Ston SA 250 Soldo & jardas (2000) 1974 Trieste C.T 392 Bussani (1974) 1980 Molat MA 550 Miličic (1994) 1981 IČK.i NA 265 Soldo & lardas (2000) 1985 Opatija NA 647 Miličfc! (1994) 1991 Ičici NA app.600 Kovačič [1993) 1991 Miramare near Trieste CT app.600 Perco (1993) 1994 Mola di Bari SA 430 Bello (1999) 1995 island of Ugijan MA 700 Dulčic (1997) 1997 Bitonto (Apulia) SA juvenile Bel So (1999) 1999 Osobljava (Pcljesac) SA 722 Soldo et a!. (1999) ¡2000 Pula NA 770 Dulčic1 (pers. comm.) 2000 Bfitvenica MA 850 Dulčič (pers. comm.) 2000 Pit an GT 299 This report 2000 Piran GT 249 This report Fig. 3: Juvenile basking shark caught on 22nd May 2000 in the wafers off Piran (Photo: T. Makovec). SI. 3: Mladič morskega psa orjaka, ujel 22. maja 2000 v vodah nedaleč od Pirana (Foto: T. Makovec). Fig. 4: Juvenile basking shark caught on 19th July 2000 in the wafers off Piran (Photo: 7. Makovec). SI. 4: Mladič morskega psa orjaka, ujet 19. julija 2000 v vodah nedaleč od Pirana (Foto: T. Makovec). 214 ANNALES • Scr. his), nat. • 10 ■ 2000 • 2 (21) lovrcpcuro «i/.. OCCURBfNCt Of- "I HE 8ASWC SHARK. CfTOftmNtJSMAMMUT «CONNORS, 37631. IN THE WATERS OFF PiKAN .... 2(1-21 ft To our opinion, the number of records would be much higher if the information regarding sightings and captures of basking sharks reached ichthyologists. Bello (1999) reported about a butchered juvenile Basking shark caught off the Apulian coast in the Southern Adriatic (Tab. 7). in d comprehensive Survey, Barrull & Mate (1999) collected data on 16S basking sharks from documented records in the scientific literature covering the entire Mediterranean. Analysing the collected data, the authors reached the conclusion that basking sharks were more frequently caught in May and June. The two smallest specimens, both caught, off the western Italian coasts, measured 150 cm, whereas the larger Mediterranean shark caught measured !300 cm (Barrull & Mate, 1999). In order to establish the ratio of specimens lower than 3 m in size, we complemented these data with those of Soldo & jardas (2000) and our records. From 149 records of the measured basking sharks (e.g. where data 30.0 - on size exist) recorded from the Mediterranean in the 1795-2000 period, almost half of them (44.3%) .ire smaller than 400 cm {F'rg. 5) and almost a fifth of them (18.8%) smaller than 300 cm. On the basis of the high number of juveniles lower than 300 cm recorded in their study, Barrulf & Mate (1999) believe that there is a possibility that. Site basking shark gives birth in the Mediterranean. ACKNOWLEDGEMENTS We wish to express our sincere thanks to Alen Soldo for his critical reading of the manuscript. We would also like to take this opportunity to express our thanks to Alessandro De Maddalena (Milan) for his drawing of the basking shark and providing us some references, and to Roberto Odorico who shared with us his experiences regarding this shark species in She studied area. n = 149 O) CTv o*> Ol T- C71