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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 are fused into the stages of development as proposed by Grier (1981). posteriorly, each with a roughly hollow cylindrical form Since the fish were previously frozen, some ovarian and and a lamellar configuration. Histological examination of testicular structures were not clearly indentifiable, such as the ovary revealed that although some stages of atretic follicles and postovulatory follicles (POFs) or development seemed to be present within the gonad, there spermatogonia. Female and male maturity phase was based was clearly a dominant population of bigger vitellogenic on Brown-Peterson et al. (2011). follicles greater than 650 µm (Fig. 2), which composed the The number of follicles in the ovary was estimated by leading cohort of follicles (potential fecundity). A smaller separating follicles (Lowerre-Barbieri & Barbieri, 1993), mode of reduced follicles was present within the follicle combining the gravimetric method with a computer-aided size frequency distribution. image analysis system that enumerated and measured Although no hydrated follicles were identified, there was follicle diameters in a sub-sample of 0.050 g (± 0.002 g) evidence of follicle maturation such as the presence of approximately. Measurements (number of follicles > 1000) Germinal Vesicle Migration (GVM). Despite the low were performed using QWin software (Leica Imaging Systems) on a PC connected to a video camera on a stereo microscope. Three ovarian sub-samples from anterior, middle and posterior sections of the gonad were examined in order to investigate follicle distribution and homogeneity of follicle density within the ovary (Murua & Saborido- Rey, 2003). Sub-samples were preserved in 3.6% buffered formalin with rose Bengal dye to enhance features and increase the contrast. Fecundity (F) was then estimated using the equation: F = GW × N / SW (1) where SW is the sub-sample weight and N is the total number of follicles in the leading cohort of the sub-sample. Fecundity was calculated as the product of the mean number of follicles per unit of ovarian weight by the total ovarian weight (GW).

Stomachs contents Figure 2. Schedophilus medusophagus. Follicle size frequency The stomach contents of the specimens were also analysed. distribution in ovary. Where possible, prey were separated and identified to Figure 2. Schedophilus medusophagus. Distribution de la species level. fréquence de taille du follicule dans l’ovaire. 274 SHALLOW RECORDS OF SCHEDOPHILUS MEDUSOPHAGUS FROM ATLANTIC

quality of the ovarian tissue sampled (due to ini- tial frozen preservation), it was possible to confirm the maturity status of the female as Actively Spawning, due to the presence of GVM within the ovary (Fig. 3). The morphology of the testes was lobular with spermatogonia development evident along the germinal epithelium. Spermatogenesis is cystic in this species, with developing germ cells enclosed within germinal cysts formed by enveloping Sertoli-cell processes. Within each cyst the maturation of germ cells is synchronous. The male maturity status was established as Actively Spawning since the testes exhibited 50 This paper ── Holt & Byrne (1903) Steven (1955) ─ BRFC Website ─ Marine Life News (Autumn, 2008) ─ Steven (1955) ─ Lagardère & Fourneau (2009) ─ ─ Harambillet et al. (1976) 475044 Lagardère & Fourneau (2009) This paper This paper 48.352.023.8 Gunther (1860) Holt & Byrne (1903); Regan (1902) Gunther (1882) 50.043.0 Amanieu & Cazaux (1963) 36.6 (1972) Went O’Riordan (1981) 44.6 News Marine Wildlife (Spring 2010) ± spermatozoa in the lumen of the lobules (Fig. 4). TL (cm)TL Reference Fecundity estimation. Homogeneity of follicle size distribution was checked in order to avoid bias in diameter estimation in relation to tissue sampling location within the ovary. No signifi- cant differences were found in follicle diameter between ovary sub-sample locations (ANOVA, F = 2.31, df = 2, n = 8, p-value = 0.14). For fecundity estimation it was assumed that the leading cohort of follicles (> 650 µm) corresponded with the potential fecundity. Since the identification of Post Ovulatory Follicles ─ Method & Depth (m) stranded after storm ─ salmon net by hand at surface after stormset net washed ashore in shallow water 50.1stranded netted alive Pellegrin (1912); Dubalen (1930) rod & line from shore shrimp trawl (3 m) gill-net gill-net gill-net (4 m) rod & line (5 m) gill-net (4-5 m) gill-net (6 m) (POFs) in the ovary was not confirmed, the potential fecundity estimations could be under - estimated if the female had already spawned at least once during the spawning season. However, no evidence of batch fecundity was observed. Taking these factors into consideration, the estimated potential fecundity was 355,004 eggs and the estimated relative potential fecundity (N follicles.g-1 of female) was 409 eggs.g-1.

Stomachs contents There was little content in both of the stomachs analysed. The first stomach contained two cope- pod remains (probably calanoids), eggs, an unidentifiable tissue and different types of (Galicia, NW Spain) pigmented scales. The second stomach contained scales, an unidentifiable tissue (cephalopoda?) and one digested siphonophore. Location Cornwall (SW England) NE Ireland Arcachon, SW France Ballinakill Co Derryinver, Harbour, Galway (W Ireland) caught from shoreline (barely alive) 42.0 Eoin McGreal NPWS (pers. comm.) Ría de Vigo Discussion

The presence of adults and mature specimens of Schedophilus medusophagus . Compilation des signalements historiques en eaux côtières peu profondes dans l’Atlantique.

Schedophilus medusophagus . Historical compilation of shallow inshore Atlantic records waters. in S. medusophagus in shallow coastal waters is unusual. The current inshore records represent a vertical, but also a horizontal displacement from Table 1. Table 1. Tableau Date February 1859 ─ August 1878 Polperro, near Looe (UK) ─ March 190801.05.1954Antrim Portrush, (N Co Ireland) 03.06.19541963 Capbreton, Biscay (NW France) 18.10.1971 W shore of Isles Bryher, of Scilly (UK) 27.09.1972 Ho, Devon (UK) Westward 27.04.1980March 1983Achill Dooega Island Strand, Co Mayo (W Ireland)2000 Plage de Biarritz la (SW France) Milody, off Ballydavid Strand, Co Kerry (SW Ireland) Cefn Siddan Beach, (UK) Swansea, S Wales stranded alive 09.10.2008 off Maplethorpe, Linconshire (UK) 20.05.200822.05.200817.02.2009 16.03.2010 Huchet, Moliets (SW France) 28.04.2010 Huchet, Moliets (SW France) 19.06.2010 Corrubedo (Galicia, NW Spain) Ría thede Cedeira (Galicia, NW Spain) S Lihou Island (W Guernsey) previously described mesopelagic natural R. BAÑÓN, A. ALONSO-FERNÁNDEZ, D.T.G. QUIGLEY, A. MIRANDA, J.C. ARRONTE 275

Figure 4. Schedophilus medusophagus. Histological slide of testes in actively spawning phase. SPZ, spermatozoa. Figure 4. Schedophilus medusophagus. Lame histologique des testicules dans la phase active de ponte. SPZ, spermatozoïdes.

and spermatogenesis development as in most teleosts (West, 1990; Tyler & Sumpter, 1996; Murua & Saborido- Rey, 2003). Although the follicle size-frequency distribution was continuous within the ovary, females exhibited a dominant population of bigger vitellogenic follicles. This leading cohort of follicles may represent the potential fecundity for the subsequent spawning season. Moreover, the existence of a smaller cohort of follicles would indicate the presence of the upcoming stock of Figure 3. Schedophilus medusophagus. Histological slide of ovary in actively spawning phase. AT, atretic oocyte; GVM, follicles that will be released in the next spawning season. germinal vesicle migration; OD, oil droplet; PG, primary growth; Taking all these facts into account, S. medusophagus may VIT, vitellogenic oocyte. be considered group-synchronous, with a highly Figure 3. Schedophilus medusophagus. Lame histologique des synchronous population of larger follicles (Murua & ovaires dans la phase active de ponte. AT, ovocytes atrétiques ; Saborido-Rey, 2003). Other centrolophid species such as GVM, migration de la vésicule germinale ; OD, gouttelettes Hyperoglyphe antarctica (Carmichael, 1819) clearly d’huile ; PG, croissance primaire ; VIT, ovocyte vitellogénique. showed a determinate fecundity strategy and a group- synchronous ovarian development (Baelde, 1996). Testicular tissue was found to be lobular type habitat of the species. Although the current phenomenon is (Takashima & Hibiya, 1995), i.e. spermatogonia were difficult to explain, infrequent and exceptional behaviours randomly distributed along the entire length of the tubule in can provide insights into the ecology and physiology of a reproductively active fish, equivalent to the unrestricted particular species (Houghton et al., 2008). spermatogonial type proposed by Grier (1981). This type of The historical data indicated a diverse origin for these testis organization does not differ from the organization shallow inshore records, including some strandings. found in the centrolophid H. perciformis (Filer & Sedberry, Inshore specimens were reported during most months of the 2008). However, in the latter species, a small proportion of year except January, July, November and December. intersexual individuals have been found. Although more Although no seasonal trend was found in the historical data specimens of S. medusophagus are required to clearly state set, most of the specimens were recorded during the first ovarian and testes development organization, this is the first half of the year, which may also indicate some type of histological analysis of the reproductive traits in this periodicity. No latitudinal trend was found either. species. Our first tested hypothesis suggests spawning migration The obtained potential fecundity estimation could have as a possible cause for the capture of specimens in shallow been underestimated since it was not possible to identify waters. Reproductive analyses showed typical oogenesis postovulatory follicles due to the low quality of the samples 276 SHALLOW RECORDS OF SCHEDOPHILUS MEDUSOPHAGUS FROM ATLANTIC preserved. However, in spite of these limitations, the result The stomach content analysis did not reveal sufficient of the relative fecundity, 409 eggs.g-1, does not differ much evidence to support the hypothesis of an inshore feeding from the average counts found in H. antarctica of 480 + migration, because relatively few prey items were recorded. 125 eggs.g-1 (Baelde, 1996). The presence of efficient food-shredding toothed saccular The most important result obtained from the outgrowths in the alimentary tract of centrolophid species reproductive analyses in the present study was that the two may explain why stomach contents are generally specimens examined were sexually mature and in an unidentifiable (Haedrich, 1967) as well as the paucity of Actively Spawning phase, suggesting a possible spawning prey items. Although catches at night could support the migration. Their occurrence, mainly during the first half of hypothesis of a nocturnal coastal feeding migration, they do the year, could support a possible inshore migration related not rule out the alternative hypothesis of an inshore to a spawning season. In Galician waters, this kind of reproductive migration. reproductive offshore-inshore migratory behavior has only Since the current study did not find any conclusive been noted in the lumpsucker Cyclopterus lumpus Linnaeus evidence to support either of the two proposed hypotheses, 1758, a species in which this reproductive pattern is well other possible explanations need to be explored. For documented. Mature or spawning specimens of C. lumpus example, Blanchard & Vandermeirsch (2005) suggested are occasionally found in coastal inshore waters of Galicia that increasing water temperatures may lead to the albeit only during the reproductive season, in the first half translocation of deep-water species into shelf seas. In of year (Bañón et al., 2008). However, in order to support Galician waters, the sea surface temperature increased by the case for a potential offshore-inshore reproductive 0.8ºC during the period 1960-2006 (Bañón, 2009). migration in S. medusophagus, one would expect a higher The recorded data do not clarify if it is an emerging number of records of mature specimens in shallow coastal phenomenon that could be due to either recent ecological or waters among the historical data set. Since no previous physiological changes. Further investigations of shallow information regarding the sexual cycle of S. medusophagus inshore records of S. medusophagus are required in order to is currently available and there are relatively few records of clarify whether or not it is a consequence of real changes or coastal shallow-water specimens, it is not possible to just the occasional arrival of vagrant specimens. definitively confirm the connection of such shallow coastal records with a spawning season. Spawning migrations are Acknowledgements designed to maximize reproductive success fitting spawning with optimal environmental conditions for eggs The authors would like to thank M. Muñoz for helpful and larvae (Leggett, 1977). Unfortunately such optimal histological advice. We are also deeply grateful to M. conditions for S. medusophagus eggs and larvae remain Guiance and P. Varela for technical support and assistance unknown. with histological work. We are also indebted to David Feeding migrations could also be another possible Villegas (IIM-CSIC) for his collaboration with the map and explanation for this phenomenon. A temporary lack or to Eoin McGreal (National Parks & Wildlife Service shortage of their usual offshore prey may explain the (NPWS), Letterfrack, Connemara, Co Galway) for migration and/or occasional occurrence of this species in unpublished details on a specimen recently stranded on the coastal waters. S. medusophagus feeds mainly on Galway coast. gelatinous plankton and small crustaceans (Haedrich, References 1986). Alonso-Fernández A., Dominguez-Petit R., Bao M., Rivas C. Most mesopelagic species show extensive vertical & Saborido-Rey F. 2008. Spawning pattern and reproductive migrations into the epipelagic zone at night, where they strategy of female pouting Trisopterus luscus (Gadidae) on the prey on plankton and on other mesopelagic species, and Galician shelf of north-western Spain. Aquatic Living thereafter they migrate down several hundred meters to Resources, 21: 383-393. their daytime depths (Salvanes & Kristofersen, 2001). If we Amanieu M. & Cazaux C. 1963. Nouveaux animaux observes assume that all of our specimens were taken at night, we dans la Région d’Arcachon en 1962-1963. Poissons. Procès- could possibly relate these anomalous occurrences to a Verbaux de la Société Linnéenne de Bordeaux, 100: 1-6. potential nocturnal coastal feeding migration analogous to Badcock J. 1970. The vertical distribution of mesopelagic fishes collected on the SOND Cruise. Journal of the Marine a diel vertical migration (DVM). It is interesting to note that Biological Association of the United Kingdom, 50: 1001-1044. both of the specimens recently recorded from the Bay of Baelde P. 1996. Biology and dynamics of the reproduction of blue- Biscay as well as the recent Guernsey Island specimen were eye trevalla, Hyperoglyphe antarctica (Centrolophidae), off captured at night. Likewise, pelagic juvenile specimens of Tasmania, southern Australia. Fishery Bulletin, 94: 199-211. S. medusophagus have been captured at the surface mainly Bañón R., Garazo A. & Fernández A. 2008. Note about the at night (Bone & Brook, 1973). presence of the lumpsucker Cyclopterus lumpus (Teleostei, R. BAÑÓN, A. ALONSO-FERNÁNDEZ, D.T.G. QUIGLEY, A. MIRANDA, J.C. ARRONTE 277

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