Northernmost record of a whale shark Rhincodon typus from the Sea of Okhotsk

The whale shark Rhincodon typus is the world's largest fish and it occurs in tropical, subtropical and warm temperate waters. Here, the northernmost record of R. typus is reported, when it was found in the Sea of Okhotsk for the first time. This occurrence can be explained by the unusually high sea surface temperature during the summer of 2012.     

Functional analysis of the musculo‐skeletal system of the gill apparatus in Heptranchias perlo (Chondrichthyes: Hexanchidae)

Musculo‐skeletal morphology is an indispensable source for understanding functional adaptations. Analysis of morphology of the branchial apparatus of Hexanchiform sharks can provide insight into aspects of their respiration that are difficult to observe directly. In this study, I compare the structure of the musculo‐skeletal system of the gill apparatus of Heptranchias perlo and Squalus acanthias in respect to their adaptation for one of two respiratory mechanisms known in sharks, namely, the active two‐pump (oropharyngeal and parabranchial) ventilation and the ram‐jet ventilation. In both species, the oropharyngeal pump possesses two sets of muscles, one for compression and the other for expansion. The parabranchial pump only has constrictors. Expansion of this pump occurs only due to passive elastic recoil of the extrabranchial cartilages. In Squalus acanthias the parabranchial chambers are large and equipped by powerful superficial constrictors. These muscles and the outer walls of the parabranchial chambers are much reduced in Heptranchias perlo , and thus it likely cannot use this pump. However, this reduction allows for vertical elongation of outer gill slits which, along with greater number of gill pouches, likely decreases branchial resistance and, at the same time, increases the gill surface area, and can be regarded as an adaptation for ram ventilation at lower speeds.     

First record of a dicephalic specimen of tope Galeorhinus galeus (Elasmobranchii: Triakidae)

The first case of dicephalia in tope Galeorhinus galeus analysed in developing foetuses removed from a pregnant female caught off the Mar del Plata coastal waters, Argentine Sea, is reported here.     

Observations of coastal aggregations of the broadnose sevengill shark (Notorynchus cepedianus) in Chilean waters

The presence of four sharks was documented in coastal waters of Antofagasta (Chile) using an unmanned aerial video camera. Fishers took advantage of this aggregation to catch and sold three adult broadnose sevengill sharks Notorynchus cepedianus. Species identity was determined by using the cox1 gene. One additional video was later recorded 3000 km south of Antofagasta, and shows a large female interacting with a salmon farming facility. Shallow water records of N. cepedianus were previously undocumented in Chilean waters, yet historically have provided an opportunistic event to fishers in Chile.     

Occurrence of the Chilean devil ray Mobula tarapacana (Elasmobranchii: Batoidea: Myliobatiformes) in the Sea of Okhotsk: first record from cold temperate waters

The northernmost record for Chilean devil ray Mobula tarapacana, a circumglobal species that occurs in tropical, subtropical and limited warm temperate waters, is described. An adult female was caught incidentally in the Sea of Okhotsk on 17 September 2011. This specimen is the first confirmed occurrence of devil rays Mobula spp. in cold temperate waters.     

Observations on the biological traits of the rare shark Oxynotus centrina (Chondrichthyes: Oxynotidae) in the Hellenic Seas

New records of the rare angular rough shark Oxynotus centrina from the Hellenic Seas are presented. Its occurrence is reported for the first time in the Corinthian Gulf. Some aspects of the species' biology are described and compared with previous studies.     

Seasonal variation in occurrence of the sevengill shark,Notorynchus cepedianus,in two inshore habitats of southern New Zealand

Despite being a large, relatively abundant predator, the distribution and seasonal occurrence of the broadnose sevengill shark, Notorynchus cepedianus, in New Zealand is poorly understood. During 71 sampling trips conducted from July 2013 to May 2015, sharks were attracted to coastal sampling sites in southern New Zealand at ōtākou/Otago Harbour and Te Whaka ā Te Wera/Paterson Inlet, Stewart Island, using chum. Using a logistic regression model, water temperature was identified as a key predictor of encountering sevengill sharks. In addition, location, cloud cover and sea state were also identified as influential predictors. At ōtākou, a clear seasonal pattern of sevengill shark sightings emerged. Sharks were detected on 86% of survey trips in summer, whilst no sharks were detected in winter or spring. At Te Whaka ā Te Wera, sharks were sighted throughout all seasons, but a decline in shark encounters occurred during winter. This study represents the first systematic data on seasonal habitat use by sevengill sharks in New Zealand.     

A preliminary study on gill metazoan parasites of Dentex dentex (Pisces: Sparidae) from the western Mediterranean Sea (Balearic Islands)

A preliminary study of the gill parasites from 61 common dentex (Dentex dentex, Pisces, Sparidae) was developed. Seven parasite species were found: one monogenean (Microcotyle erythrini), one udonellidean Udonella caligorum), one digenean trematode (Stephanostomum sp. metacercariae), three copepods (Caligus productus, Caligus diaphanus and Clavellopsis fallax) and one isopod (Gnathia vorax, praniza larvae). Only 1.6% of the fishes examined presented one parasitic species whilst the remainder had two parasitic species (13%), three (26%), four (21%), five (20%) and six different species (18%). The udonellidean U. caligorum was found as a hyperparasite or phoront of the three copepods. Prevalence and other ecological parameters as well as the spatial site of each parasite in the gill tissue are described. The multiparasitic combinations are also examined.     

The youngest record of Carcharopsis (Chondrichthyes) from the Pennsylvanian of Xinjiang Uyghur Autonomous Region,China

A chondrichthyan tooth having a serrated edge, from the Late Pennsylvanian of Xinjiang Uyghur Autonomous Region, China, was identified as Edestus sp. [Cheng, Z., Lucas, S.G., Zidek, J., 1996. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte 1996 (11), 701-707]. Because of the lack of bilateral symmetry, the tooth does not belong to Edestus or any other known edestoid. It is too incomplete for a definite identification, but its features are consistent with Carcharopsis, which also has serrated teeth, and not with any other described late Paleozoic chondrichthyan genus. If it is Carcharopsis, it is the latest occurrence of the genus, which was previously known only from the Mississippian and the Early Pennsylvanian.     

Factors determining the interaction between common bottlenose dolphins and bottom trawlers off the Balearic Archipelago (western Mediterranean Sea)

Factors determining bottlenose dolphin association with bottom trawlers were studied off the Balearic Islands, western Mediterranean, by studying dolphin distribution around the islands and their interaction with fishing operations. Results showed that bottlenose dolphins avoided the upper shelf (shallower than 50 m) in the warm season, but not in the cold season and that the slope was avoided all year round. Bottlenose dolphins approached most of the trawlers surveyed in the continental shelf, but seldom interacted with those operating in the slope in the warm season. As a consequence, the average depth of trawling operations that attracted dolphins was shallower than those not attracting dolphins. No statistical difference was observed in the average catch of hauls conducted in the presence or in the absence of dolphins. However, discriminant analysis showed differences in catch composition between hauls with and without dolphin presence, but this difference was not attributed to the palatability of the catch, but to influence of trawling depth on the catch. It is concluded that depth is the main factor ruling occurrence of interaction.     

Discovery of a multispecies shark aggregation and parturition area in the Ba Estuary,Fiji Islands

Population declines in shark species have been reported on local and global scales, with overfishing, habitat destruction and climate change posing severe threats. The lack of species‐specific baseline data on ecology and distribution of many sharks, however, makes conservation measures challenging. Here, we present a fisheries‐independent shark survey from the Fiji Islands, where scientific knowledge on locally occurring elasmobranchs is largely still lacking despite the location's role as a shark hotspot in the Pacific. Juvenile shark abundance in the fishing grounds of the Ba Estuary (north‐western Viti Levu) was assessed with a gillnet‐ and longline‐based survey from December 2015 to April 2016. A total of 103 juvenile sharks identified as blacktip Carcharhinus limbatus (n = 57), scalloped hammerhead Sphyrna lewini (n = 35), and great hammerhead Sphyrna mokarran (n = 11) sharks were captured, tagged, and released. The condition of umbilical scars (68% open or semihealed), mean sizes of individuals (±SD) (C. limbatus: 66.5 ± 3.8 cm, S. lewini: 51.8 ± 4.8 cm, S. mokarran 77.4 ± 2.8 cm), and the presence of these species over recent years (based on fishermen interviews), suggest that the Ba Estuary area is a critical habitat for multiple species that are classified as “Near Threatened” or “Endangered.” Specifically, the area likely acts as a parturition ground over the studied period, and potentially as a subsequent nursery area. We identified subareas of high abundance and found that temperature, salinity and depth acted as small‐scale environmental drivers of shark abundance. The data suggests a tendency for species‐specific spatial use, both horizontally (i.e., between sampling areas) and vertically (i.e., across the water column). These results enhance the understanding of shark ecology in Fiji and provide a scientific basis for the implementation of local conservation strategies that contribute to the protection of these threatened species.     

The Occurrence of White Sharks, Carcharodon carcharias, Around the Balearic Islands (Western Mediterranean Sea)

The regular presence of the white shark, Carcharodon carcharias, off the Balearic Islands (western Mediterranean) is shown from 27 captures carried out with trap nets between the 1920s and 1970s and from eight attacks on cetaceans and marine turtles from the 1990s to the present. The geographic distribution, seasonality and population structure of the species in the area are analysed and discussed in relation to environmental conditions and to the proposed distribution of this species in the Mediterranean Sea.     

On the first record of the genus Octopoteuthis (Cephalopoda: Octopoteuthidae) in the Sardinian Channel (central western Mediterranean Sea)

A specimen of the rare squid genus Octopoteuthis (Cephalopoda: Octopoteuthidae) from 1600 m in the Sardinian Channel (central western Mediterranean) is described. Meristic and morphological data are provided. The specimen was a spent female and details of the reproductive system and implanted spermatangia are reported. Genetic analysis of this specimen and comparison with those available for species in this genus were carried out. Due to issues associated with the taxonomy of the genus Octopoteuthis, it was not possible to identify the specimen to the species level. The taxonomy of the genus is discussed.     

First record of Cephalopholis taeniops (Valenciennes) in the Mediterranean Sea

Two specimens of African hind Cephalopholis taeniops (Valenciennes, 1828) are recorded for the first time in the Mediterranean Sea, in the coastal area of Gulf of Syrte, Libya. This finding represents an additional case of a tropical species of fish of West African origin in the Mediterranean Sea.     

Retracted: A new species in town: New record of Hexanchus nakamurai Teng, 1962 from the Levantine Sea

Hexanchus nakamurai is a deep-water species, with very little scientific information. This study confirms the distribution of the species in the most eastern region of the Mediterranean Sea, Levantine Sea, in addition to providing some biological information from four pregnant individuals, which is being reported for the first time in the Mediterranean Sea. A total of four individuals were bycaught, in two sets on opposite coasts, three on the 13th of May 2020 from the western coast, and an individual on the 14th June 2020 from east coast of the island of Cyprus. The four specimens, all pregnant females, measured between 107 and 116 cm in total length and between 4,330 and 4,960 g in weight. All specimens were in early pregnancy according to the level of embryo development, which confirms that the size at maturity is smaller than previously reported. In the stomachs, remains of the hake Merluccius merluccius, the cephalopod Loligo vulgaris and two unidentified species of Hirudinea (Annelida) were found. This study provides important new information on the Mediterranean distribution of a globally rare and data deficient species, including an expansion of its known range, dietary preferences and insights of its reproduction biology; the first pregnant females reported in the Mediterranean Sea.     

The morphology and ecology of Dipolydora armata (Polychaeta, Spionidae) from the western Mediterranean Sea

Bick. A. 2001. The morphology and ecology of Dipolydora armata (Polychaeta, Spionidae) from the western Mediterranean Sea. — Acta Zoologica (Stockholm) 82 : 177–187
The cosmopolitan spionid Dipolydora armata is a dominant species of epifauna on Thais haemastoma shells in the western Mediterranean Sea. Some characters, particularly number, thickness and arrangement of notopodial spines, were extremely variable among specimens. Three morphological forms were distinguished based on the general appearance of the bundles of spines; one form possesses at least one bundle of stout spines, whereas bundles of medium spines or thinner acicular spines characterise the other forms. Differences in prostomial shape, as well as in the extension and form of the caruncle, were artefacts (preservation or angle of observation). The present study supports D. rogeri as a junior synonym of D. armata. D. armata was regularly found on shells inhabited by hermit crabs ( Calcinus tubularis , Clibanarius erythropus ) and on damaged, empty shells. Abundance, dominance, size frequency, occurrence of larvae and occurrence of regenerated specimens varied, possibly as a result of fouling strategy and recurrent settlements.