Geographical, Seasonal Occurrence and Incidental ¢Shing Captures Of
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J.Mar.Biol.Ass.U.K. 2001), 81,183^184 Printed in the United Kingdom Geographical, seasonal occurrence and incidental ¢shing captures of basking shark Cetorhinus maximus Chondricthyes: Cetorhinidae) Julio Valeiras* , Alfredo Lo¨ pezO and Manuel Garc|¨aP *Instituto Espan¬ ol de Oceanograf|¨a, Puerto Pesquero, s/n, Apartado 285, 29640 Fuengirola Ma¨ laga), Spain. O E-mail: [email protected]. Instituto de Investigaciones Marinas, Eduardo Cabello, 6, 36208 Vigo, Spain. PInstituto Espan¬ ol de Oceanograf|¨a, Apartado 1552, 36280 Vigo, Spain. Co-ordinator for Marine Mammal Study CEMMA), Apartado 165, 36380 Gondomar Pontevedra), Spain This is the ¢rst report on the presence of basking sharks Cetorhinus maximus in Galician waters north-west Iberian Peninsula) from sightings, strandings and incidental catches by ¢shing gear. Morphometric, biological, geographic and temporal data on 19 basking sharks recorded from 1988 to 1998 are presented. Average total length is 401.4 cm. Male:female ratio is 0.6. Seventy per cent of records are from incidental ¢shing catches in bottom gill nets. Approximately 74% of sharks were recorded during February, March and April, which may suggest that the species occurs seasonally in this area. Cetorhinus maximus is a plankton feeding shark Lamniformes: Galicia north-west Iberian Peninsula) between the estuary of Cetorhinidae) distributed world-wide in boreal to warm the River Min¬ o41852.500N08852.500W) and the r|¨aof temperature waters. In the north-east Atlantic, this species Ribadeo 43833.200N07802.000W). occurs from the Arctic to North Africa, including the Iberian Nineteen con¢rmed and documented records recorded from Peninsula waters, Canary Islands and Mediterranean Sea 1988 to 1998 were studied. Data on date, geographical position, Compagno, 1984). total length, fate circumstances and biological samples were Several authors have recorded occurrence of basking sharks in obtained when possible. Total length distance between nose and Atlantic Iberian Peninsula waters, but data are scarce. Navaz y top of upper lobe of caudal ¢n) of 16 basking sharks was Sanz 1961) reported the captures of six juveniles and two adults recorded N19), which reached a minimum of 250 cm to a from 1946 to 1958 o¡ the San Sebastian coasts Cantabric Sea). De maximum of 860 cm. Average length was 401.4 cm. A percen- Buen 1935) included the basking shark in the ¢sh catalogue of tage of 87.5% of observed specimens displayed less than 450 cm Spanish and Portuguese coasts, and Lozano Rey 1928) recorded a total length, which means that most of the sharks were in a juve- stranding in spring of 1915 in Pontevedra north-west Spain). nile stage Compagno, 1984). Recorded presence or absence of Solo¨ rzano et al. 1988) indicated occasional ¢shing captures in pterigopods resulted in the sex identi¢cation of ¢ve females and some Galician ports including A Corun¬ a and Ribeira north-west three males N8). The male/female ratio ranges 0.6. Spain). In 1945, a whaling boat landed a 7 m total length male in Speci¢c external and internal examinations were made on Ponteceso harbour Co-ordinator for Marine Mammal Study, three specimens: code Cma9, Cma11 and Cma18 Table 1). unpublished data). Specimens Cma9 March 1995) and Cma11 April 1997) Its biology is poorly known and many aspects on movements, presented denticle gill rakers. Specimen Cma18 November reproduction and ecology are not clear Castro et al., 1999). In 1998) had a lack of gill rakers. Specimen Cma11 contained Ireland and Great Britain, it is locally common in spring and between 20 and 30 l of red stomach content, exclusively made summer at the same time of high plankton abundance Sims & up of partially digested zooplankton. This could agree with the Quayle, 1998). Most of the records at Biscay Gulf are in May and seasonal migration model developed by Parker & Boeseman June Que¨ ro et al., 1995). According to di¡erent authors, large Kunzlik, 1988). According to these authors, Cetorhinus maximus changes in the frequency of observations throughout the year can lacks denticle gill rakers at the start of a non-feeding hibernation suggest seasonal movements between low and high latitudes or period until it experiences the annual growth of these essential maybe seasonal movements from shallow to deeper waters. structures for the plankton feeding period. The species has been the target of regional ¢sheries for Male Cma9 presented several indeterminate parasitic cope- centuries in waters of great shark density, such as the west coast pods ¢xed to the ventral surface of the right pectoral ¢n. The of Ireland, Iceland, Norway and Scotland Kunzlik, 1988), and spiral valve of specimen Cma11 was heavily parasitized by it is still the target of Norwegian ships in North Atlantic waters cestodes. Pectoral, anal and caudal ¢ns of female Cma18 Anonymous, 1995). In the Cantabrian Sea, the basking shark presented many of the parasitic copepods, Dinemoura producta has been harpooned o¡ the Basque coast Lozano Rey, 1928). Mu« ller, 1785), ¢xed to the epidermis. Basking shark bycatches are not very well known, but it is In two cases, causes of death were not veri¢ed. Incidental incidentally caught by ¢xed bottom nets Castro et al., 1999) ¢shing catches N12) occurred in ¢xed entanglement bottom and drifting nets Anonymous, 1997). Stocks of basking shark nets called `trasmallo' or `min¬ o'), used by an artisanal coastal have experienced a strong decrease due to over¢shing and £eet Figure 1). Incidental catches caused the death or injuries to incidental catches and the species populations are considered to sharks and made signi¢cant damage to the ¢shing gear. After- be extremely vulnerable Castro et al., 1999; Compagno, 1984). wards, of the 12 incidental catches, three cases led to sales at Information available for this work was obtained from sight- landing markets, the release of two live sharks and the discard ings, strandings and incidental catches from the coastal area of of three dead sharks at sea. Although the ¢nal destinations of Journal of the Marine Biological Association of the United Kingdom 2001) 184 SHORT COMMUNICATIONS Table 1. Records of Cetorhinus maximus in Galicia north-west Iberian Peninsula) 1988^1998). Fish Code Date Location Latitude^Longitude Sex TL cm) Type of record Cma1 10/02/88 Carril Pontevedra) 42836.800N08846.400WI 350I Cma2 11/02/92 Raxo¨ -Poio Pontevedra) 428250N08842.600W F 298 CL Cma3 14/03/92 P. Cangas. Foz Lugo) 43837.200N07819.200W I 860 ST Cma4 28/04/92 Islas Sisargas A Corun¬ a) 438300N098000W I 400* S Cma5 03/04/93 Corme A Corun¬ a) 43808.500N098110WI 350C Cma6 19/04/93 O Grove Pontevedra) 428300N08851.750WI 345U Cma7 13/02/94 Louro, Muros A Corun¬ a) 428450N098050WI^ ST Cma8 01/03/95 Pta. Restrelo, Fisterra A Corun¬ a) 428540N098150WI^ ST Cma9 29/03/95 Portos|¨ nACorun¬ a) 42845.400N088570W M 445 CD Cma10 20/03/96 Rodeira, Cangas Pontevedra) 42815.500N08846.500W M 388 CD Cma11 07/04/97 Ensenada de Baiona Pontevedra) 42807.300N08853.300WI 347C Cma12 01/07/97 Puerto de O Grove Pontevedra) 428300N08851.750WI 400C Cma13 01/09/97 R|¨ a Vigo Pontevedra) 428130N088500W I 700* S Cma14 23/04/98 Bueu Pontevedra) 42819.500N088470WF350*CL Cma15 25/04/98 Lonja de Cambados Pontevedra) 42831.100N08848.750WI ^ CD Cma16 27/04/98 Islas C|¨ es Pontevedra) 42813.250N088550WM300C Cma17 15/05/98 Lonja de Riveira Pontevedra) 42833.800N08859.500W F 320 CS Cma18 18/11/98 Islas Sisargas A Corun¬ a) 438210N088500W F 319 CS Cma19 01/12/98 Lonja de Vigo Pontevedra) 428140N08843.500W I 250 CS C, capture in ¢shing gear; CD, capture and discard; CL, capture and free live; CS, capture and sell whole or part of the shark; F, female; I, indeterminate; M, male; S, sighting at sea; ST, stranding at coast; U, unknown; *, estimated total length. the sold sharks were not clear, information indicates the use of Anon., 1997. Informe de la primera reunio¨ n del grupo de their meat for ¢sh meal and their sale in south Spanish markets. trabajo sobre tiburones del subcomite¨ ICCAT sobre capturas Although most of the records have been reported, some di¡er- fortuitas. ICCATCollective.Scienti¢c Papers , XLVI, 319^391. ences in frequency of records between years could be explained by Berrow, S.D., 1994. Incidental capture of elasmobranchs in the the di¤culty of detecting ¢ndings. An increase in records in 1997 bottom-set gill-net ¢shery o¡ the south coast of Ireland. Journal of the Marine Biological Association of the United Kingdom, and 1998 could be the result of improved sampling resources and 74,837^847. better collaboration with ¢shermen as well as an increased aware- Castro, J.I., Woodley, C.M. & Brudek, R.L., 1999. A prelimi- ness of endangered marine animals. Despite this, monthly distribu- nary evaluation of the status of shark species. FAO Fisheries tion indicates that 73.7% of records occurred during the months: Technical Paper, 380,1^72. February, March and April. This could suggest a seasonal pattern Compagno, L.J.V., 1984. Sharks of the world. Part 1. of local abundance, which could be related to seasonal movements Hexanchiformes to Lamniformes. FAO Fisheries Synopsis,no. in North Atlantic waters. Most of the records from the Biscay Gulf 125, 234^236. [FAO Species catalogue, vol. 4.] are in May and June Que¨ ro et al., 1995). In Ireland and Great De Buen, F., 1935. Fauna ictiolo¨ gica. Cata¨ logo de peces ibe¨ ricos: Britain, the frequency of observations increased in the spring Sims de la planicie continental, aguas dulces, pela¨ gicos y de los & Quayle, 1998). In agreement with these authors, this could be abismos proximos. Instituto Espan¬ ol de Oceanograf|¨ a.Notas y ¨ explained by a displacement of population during summer to Resumenes, Serie II, 88^89,29^30.