Cah. Biol. Mar. (2012) 53 : 271-277 Unusual shallow inshore records of Cornish blackfish Schedophilus medusophagus (Stromateoidei: Centrolophidae) from Galician waters (NW Spain) Rafael BAÑÓN1, Alexandre ALONSO-FERNÁNDEZ2, Declan T.G. QUIGLEY3, Ana MIRANDA4 and Juan Carlos ARRONTE5 (1) Unidade Técnica de Pesca de Baixura (UTPB), Dirección Xeral de Recursos Mariños, Consellería do Mar, Rúa do Valiño 63-65, 15703 Santiago de Compostela, Spain. E-mail: [email protected] (2) CSIC, Instituto de Investigaciones Marinas, Eduardo Cabello 6, 36208 Vigo (Pontevedra), Spain (3) Sea-Fisheries Protection Authority, Auction Hall, West Pier, Howth, Co Dublin, Ireland (4) Instituto Español de Oceanografía, C.O. de Vigo, Aptdo. 1552, 36208 Vigo, Spain (5) Instituto Español de Oceanografía, C.O. de Santander, Promontorio San Martin s/n, 39004 Santander, Spain Abstract: Three shallow inshore records of Cornish blackfish Schedophilus medusophagus from Galician waters (NW Spain) are reported. S. medusophagus is a relatively rare mesopelagic species in the NE Atlantic. Adult specimens are mainly found in medium-depth waters (300-900 m). Their presence in shallower coastal waters is very unusual. An historical review of North Atlantic shallow inshore records was made. Reproductive and stomach content analyses were investigated and related to two proposed inshore migration hypotheses. Resulting from these investigations, the first description of gametogenesis and gonadal development organization of this species is presented. Ovary development was found to be group-synchronous, with a highly synchronous population of larger follicles. Testicular tissue was found to be lobular type. Since no conclusive evidence was found to support either of the two proposed hypotheses an additional hypothesis related to increasing sea water temperatures was proposed. Résumé: Signalement inhabituel du rouffe des méduses Schedophilus medusophagus (Stromateoidei : Centrolophidae) dans les eaux côtières peu profondes de Galice (nord-ouest de l’Espagne). Trois signalements côtiers peu profonds du Rouffe des méduses, Schedophilus medusophagus, sont rapportés dans les eaux de la Galice (NW Espagne). S. medusophagus est une espèce mésopélagique relativement rare dans l’Atlantique Nord. Les spécimens adultes sont principalement trouvés dans les eaux de profondeur moyenne (300-900 m), leur présence dans les eaux peu profondes du littoral est très inhabituelle. On a réalisé un examen historique des enregistrements côtiers peu profonds de l’Atlantique Nord. Des analyses de la reproduction et du contenu stomacal ont été effectués pour déterminer les causes probables de ces signalements côtièrs inhabituels et deux hypothèses de migration côtière sont proposées. Des hypothèses complémentaires liées aux changements climatiques sont également suggérées. Comme résultat de ces approches, la première description de la gamétogenèse et de l’organisation du développement des gonades de cette espèce est donnée. Le développement de l’ovaire est caractérisé par une population très synchrone de grands follicules. Le tissu testiculaire observé est de type lobulaire. Comme aucune preuve concluante n’a été trouvée pour soutenir l’une des deux hypothèses proposées, une hypothèse supplémentaire liée à l’augmentation des températures d’eau de mer est proposée mais des recherches complémentaires sont nécessaires. Keywords: Cornish blackfish ● Centrolophidae ● shallow water records ● reproduction ● stomach content ● Galicia Reçu le 28 juin 2011 ; accepté après révision le 7 novembre 2011. Received 28 June 2011; accepted in revised form 7 November 2011. 272 SHALLOW RECORDS OF SCHEDOPHILUS MEDUSOPHAGUS FROM ATLANTIC Introduction (NW Spain) and to investigate the possible causes that might explain this rare phenomenon. Although the sample The family Centrolophidae includes 27 species worldwide, size analyzed was too small to draw a firm conclusion, the 4 of which occur in Atlantic European waters (Quéro et al., probable origin of these unusual records was investigated 2003): Centrolophus niger (Gmelin, 1789), Hyperoglyphe based mainly on feeding and reproductive analyses. perciformis (Mitchill, 1818), Schedophilus medusophagus Coco, 1839, and Schedophilus ovalis (Cuvier, 1833). Material and Methods The Cornish blackfish Schedophilus medusophagus is a mesopelagic species found in temperate waters of the north Three specimens of S. medusophagus were caught in Atlantic and western Mediterranean (Haedrich, 1986). coastal shallow locations of Galician waters (NW Spain) by There is little information available on the vertical commercial (gillnets) and recreational fishers (rod and line) distribution and behaviour of the Cornish blackfish. The (Fig. 1). The first specimen (506 mm TL), was caught on study of vertical migrations of S. medusophagus is further 17th February 2009 in the Ría de Vigo at 4 m depth by complicated because they undertake it at night (Badcock, gillnet. The second specimen, approximately 500 mm TL 1970). Juveniles of this species (up to 20 cm total length (assessed through calibrated image), was caught with rod TL), tend to occur in shallower water than adults and often and line on 16th March 2010 off Balieiros beach in association with jellyfishes or man-made fish (Corrubedo) at approximately 5 m depth (specimen not aggregating devices (FADs) (Haedrich, 1986; Dulčić, preserved). The third specimen (444 mm TL), was caught 1998). However, adults live in deeper waters, mainly from on 28th April 2010 in the Ría de Cedeira at 4-5 m depth by 300 to 900 m depth (Quigley, 1984). gillnet. It was confirmed that the second specimen was The characteristics of the vertical distribution of meso- captured at night, while no confirmation for the other two and bathypelagic fishes are also poorly known. For specimens was possible due to gillnet soak time (24h example, in Stromateoid fishes, marked changes occur approximately). The first and third specimens were when maturity approaches, often associated with the collected and initially preserved frozen and subsequently migration from the surface layers to deeper layers where stored in 70% ethanol in the fish collections of the Museum adults are more frequently encountered (Haedrich, 1969). Luis Iglesias de Ciencias Naturais of Santiago de In the case of Centrolophid fishes, larvae occur in the Compostela (Galicia, Spain) with the reference numbers plankton, and juveniles and young adults are commonly 6157 and 6158 respectively. associated with pelagic medusae or floating objects, whereas adults live in deep water at the edge of the continental shelf, in submarine canyons or associated with oceanic islands (Haedrich, 1986). New and also unusual records of S. medusophagus have been reported by several authors (Onofri, 1986; Dulčić et al., 1999; Corsini-Foka & Frantzis, 2009; Milana et al., 2011). All these records have been justified in different ways, most of them connected to environmental factors. For the congeneric S. ovalis, Corsini-Foka & Frantzis (2009) suggested the colonization of vacant niches in a new area. Onofri (1986) noted the concurrence of juvenile stage S. ovalis and S. medusophagus in the Adriatic Sea during an invasion of the medusa Pelagia noctiluca (Forsskal, 1775). Dulčić et al. (1999) considered that the presence of S. ovalis and S. medusophagus in the Adriatic was due to water warming. Milana et al. (2011) also suggested that the presence of S. medusophagus in the Central Tyrrhenian Sea could be an indicator or example of the biological consequences of environmental and climatic change. The presence of adult specimens of S. medusophagus in coastal shallow inshore waters is an unusual behaviour that has been poorly documented. The aim of this paper is to Figure 1. Schedophilus medusophagus. Capture locations. describe the unusual records of three specimens of S. Figure 1. Schedophilus medusophagus. Localisation des medusophagus found in shallow inshore waters of Galicia exemplaires capturés. R. BAÑÓN, A. ALONSO-FERNÁNDEZ, D.T.G. QUIGLEY, A. MIRANDA, J.C. ARRONTE 273 Historical Records Results An historical review of specimens of S. medusophagus recorded from the North Atlantic based on published and Historical Records grey literature was made in order to determine the best known depth distribution. Out of a total of 92 compiled records since 1859 we selected 20 shallow inshore records (estimated capture depth < 20 m) Reproductive analysis (Table 1). Lagardère & Fourneau (2009) recently reported the capture of two specimens of S. medusophagus by gillnets After defrosting, gonads were removed and fixed in 3.6% in shallow inshore waters of the Bay of Biscay. Another buffered formalin. Central portions of the fixed gonads shallow inshore specimen of S. medusophagus measuring 44 were extracted, dehydrated, embedded in paraffin, cm TL was caught by gillnets off Lihou Island (Guernsey) at sectioned at 3 μm and stained with haematoxylin-eosin for 6 m depth in 2010 (Marine Wildlife News, Spring 2010). In microscopic analysis. Histological procedure details are both cases, the specimens were not analysed and no available in Alonso-Fernández et al. (2008). explanations for their capture were provided. The ovarian follicles (oocytes and surrounding follicular layer) were classified into stages of development using Reproductive analysis histological criteria (Tyler & Sumpter, 1996; Murua & Gonad development. The ovaries of S. medusophagus are Saborido-Rey, 2003). Testicular germ cells were classified oval-shaped, displaying two lobes which