Basking Shark Cetorhinus Maximus Research Articles

Regionally endothermic traits in planktivorous basking sharks Cetorhinus maximus

Few fast-swimming apex fishes are classified as ‘regional endotherms’, having evolved a relatively uncommon suite of traits (e.g. elevated body temperatures, centralised red muscle, and thick-walled hearts) thought to facilitate a fast, predatory lifestyle. Unlike those apex predators, Endangered basking sharks Cetorhinus maximus are massive filter-feeding planktivores assumed to have the anatomy and physiology typical of fully ectothermic fishes. We combined dissections of stranded specimens with biologging of free-swimming individuals and found that basking sharks have red muscle located medially at the trunk, almost 50% compact myocardium of the ventricle, and subcutaneous white muscle temperatures consistently 1.0 to 1.5°C above ambient. Collectively, our findings suggest basking sharks are not full ectotherms, instead sharing several traits used to define a regional endotherm, thus deviating from our current understanding of the species and questioning the link between physiology and ecology of regionally endothermic shark species. With successful forecasting of population dynamics and distribution shifts often improved by accurate physiological data, our results may help explain movement patterns of the species, which could ultimately facilitate conservation efforts.

Legacy and emerging contaminants in the endangered filter feeder basking shark Cetorhinus maximus

The status of contamination by chemical pollutants on large filter feeding sharks is still largely unknown. This study investigated for the first time the presence of legacy, emerging contaminants and trace elements in multiple tissues of basking sharks. In general, skin showed higher concentration of legacy and emerging contaminants probably due to pollutants being adsorbed onto the dermal denticles of the skin rather than accumulated in the tissue itself. Contaminants measured in both subcutaneous tissue and muscles appeared to strongly correlate with each other, indicating that the former might be a good proxy of muscle contamination in basking sharks. Considering the migratory nature of this species, longevity and feeding ecology, this species represents the perfect candidate to act as early warning bioindicator of regional contamination. In this context, non-lethal subcutaneous biopsies could allow the early detection of any temporal variation in the bioaccumulation of pollutants in the Mediterranean Sea.

A new species of the enigmatic shark genus Nanocetorhinus (Chondrichthyes) from the Oligocene of Austria with palaeoceanographic implications

Abstract Deep-neritic sediments of the Eferding Formation (Egerian, Upper Oligocene) of Upper Austria from the Kamig kaolinite quarry revealed minute teeth of the putatively planktivorous shark genus Nanocetorhinus. This is the oldest unambiguous record of this rarely documented genus, which was known so far only from Miocene deposits of Europe, North America and Japan. Based on previous studies, which showed a positive correlation between sediments of nutrient rich waters and plankton blooms with a majority of ichthyoliths of Keasius and Nanocetorhinus, we argue for a filter-feeding and migratory lifestyle of the latter. Thus, it is supposed that Nanocetorhinus migrated seasonally for foraging, in a similar way to the extant basking shark Cetorhinus maximus. This mode of life and the wide paleogeographic distribution of the open marine genus Nanocetorhinus requires a deep and fully marine connection between the Paratethys and the Proto-Mediterranean Sea during late Oligocene times, which might have been established via the Slovenian Corridor.

Negative allometric growth during ontogeny in the large pelagic filter-feeding basking shark

Many pelagic shark species change body and fin shape isometrically or by positive allometry during ontogeny. But some large apex predators such as the white shark Carcharodon carcharias or the tiger shark Galeocerdo cuvier show distinct negative allometry, especially in traits related to feeding (head) or propulsion (caudal fin). In particular, changes in propulsion are attributed to a shift in swimming mode. The more heterocercal caudal fin of younger individuals with its large caudal fin span seemingly aids in hunting small, agile prey. In contrast, the less heterocercal caudal fin with a larger fin area in larger individuals aids a long-distance slow swimming mode. We were interested if negative allometric effects can be observed in a planktivorous shark, the basking shark Cetorhinus maximus, a large species adapted to long-distance slow swimming. To address this question, we compared three size classes, specifically < 260 cm (juveniles), 299–490 cm (subadults), and from adults > 541 cm total length. Comparing literature data, we found negative allometric growth of the head and of the caudal fin, but a more rapid decrease of relative caudal fin size than of relative head length. Hereby, we provide the first evidence for early negative allometric growth of the caudal fin in a large pelagic filter-feeding shark. Our study further demonstrates that ecomorphological approaches may add valuable insight into the life history of animals that are challenging to study in their natural habitat, including large roving sharks such as the basking shark.

Basking shark Cetorhinus maximus, (Lamniformes: Cetorhinidae), at northern and western Iberian Peninsula waters (NE Atlantic)

Basking shark Cetorhinus maximus, (Lamniformes: Cetorhinidae), at northern and western Iberian Peninsula waters (NE Atlantic)

Are close-following and breaching behaviours by basking sharks at aggregation sites related to courtship?

Basking sharks Cetorhinus maximus tend to aggregate in summer at favoured locations along Britain and Ireland's west coast. Sharks have been described approaching and close-following one another, often to one side. This has been interpreted as putative pre-mating behaviour. At aggregation sites around the Inner Hebrides we used boat-based observation and in-water and overhead drone video-photography to document behaviour and to determine the sex of individuals. It was confirmed that a shark will frequently move purposely towards another from a distance and swim to maintain a position either directly behind or closely to one side of a conspecific for short periods. Contrary to expectation, we found no relationship between the sex of a shark or its size and close-following. This suggests that following behaviours are not mainly related to courtship. Further, abrasions on the nose suspected to be related to male behaviour were found to occur on both sexes, although abrasions on pectoral fins, similarly suggestive of mating-related behaviour, were predominantly on females. Breaching by basking sharks has also been proposed as a means of attracting the opposite sex. We observed breaching by solitary sharks but commonly by sharks within aggregations, and at other times by more than one shark on the same day at the same time; but there was not any clear evidence to indicate that breaching is primarily related to mating. More likely individuals show close following chiefly for feeding-related hydrodynamic advantage. It remains plausible however that mature sharks make use of feeding aggregations to initiate pre-courtship behaviour.

Occurrence of basking shark Cetorhinus maximus in southern Portuguese waters: a two-decade survey

Occurrence of basking shark Cetorhinus maximus in southern Portuguese waters: a two-decade survey

Estimating the geographic range of a threatened shark in a data-poor region: Cetorhinus maximus in the South Atlantic Ocean

Abstract The distribution of the planktivorous basking shark Cetorhinus maximus is influenced by zooplankton abundance at small scales and temperature at medium scales in the North Atlantic. Here, we estimate the distribution of basking sharks on South Atlantic continental shelves, and the relative importance of chlorophyll concentration, as a proxy for zooplankton abundance, and temperature in determining habitat suitability for basking sharks at large scales. We used maximum entropy (MaxEnt) and maximum likelihood (MaxLike) species distribution modelling to test three hypotheses: the distribution of basking sharks is determined by (1) temperature, (2) chlorophyll concentration, or (3) both chlorophyll and temperature, while considering other factors, such as oxygen and salinity. Off South America, basking shark habitat included subtropical, temperate and cool-temperate waters between approximately 20°S and 55°S. Off Africa, basking shark habitat was limited to cool-temperate waters off Namibia and southern South Africa. MaxLike models had a better fit than MaxEnt models. The best model included minimum chlorophyll concentration, dissolved oxygen concentration, and sea surface temperature range, supporting hypothesis 3. However, of all variables included in the best model, minimum chlorophyll concentration had the highest influence on basking shark distribution. Unlike the North Atlantic distribution, the South Atlantic distribution of basking sharks includes subtropical and cool-temperate waters. This difference is explained by high minimum chlorophyll concentration off southern Brazil as compared to North Atlantic subtropical areas. Observations in other regions of the world support this conclusion. The highest habitat suitability for basking sharks is located close to nearshore areas that experience high anthropogenic impact.

Basking sharks and oceanographic fronts: quantifying associations in the north‐east Atlantic

Summary Understanding the mechanisms that link oceanographic processes and marine vertebrate space use is critical to our knowledge of marine ecosystem functioning, and for effective management of populations of conservation concern. The basking shark Cetorhinus maximus has been observed in association with oceanographic fronts – physical interfaces at the transitions between water masses – exploiting foraging opportunities resulting from zooplankton aggregation. However, the scale, significance and variability of these associations have not previously been established. Here, we quantify the influence of thermal and chlorophyll‐a fronts on basking shark habitat use in the north‐east Atlantic. We use animal‐mounted archival tracking together with composite front mapping via Earth Observation (EO) remote sensing to provide an oceanographic context to shark movements. We investigate levels of association with fronts occurring over two spatio‐temporal scales, (i) broad‐scale, seasonally persistent frontal zones and (ii) contemporaneous thermal and chl‐a fronts. Using random walk simulations and logistic regression within an iterative generalized linear mixed modelling (GLMM) framework, we find that seasonal front frequency is a significant predictor of shark presence. Oceanographic metrics time‐matched to shark tracks indicate that sharks show a preference for productive regions and associate with contemporaneous thermal and chl‐a fronts more frequently than could be expected at random. Moreover, we highlight the importance of front persistence and cross‐frontal temperature step, which appear to interact to affect the degree of prey aggregation along thermal fronts in this shelf‐sea system. Our findings confirm that surface frontal activity is a predictor of basking shark presence in the north‐east Atlantic, both over seasonal timescales and in near real‐time. These insights have clear implications for understanding the preferred habitats of basking sharks in the context of anthropogenic threat management and marine spatial planning in the region.

First record of the basking shark Cetorhinus maximus (Lamniformes: Cetorhinidae) in Indonesia

A recent stranding of a basking shark Cetorhinus maximus in north-western Bali represents the first confirmed record of this large, filter-feeding shark species in Indonesian waters. Based on measurements of the fins and claspers, the adult male specimen was estimated to be between 5.6 and 8.1 m L, with an average estimate of 6.7 m L. It is possible that the Indonesian Throughflow is an important route for this species during transequatorial migrations.

Occurrence of the basking shark Cetorhinus maximus (Gunnerus, 1765) (Lamniformes: Cetorhinidae) in the central-eastern Mediterranean Sea

The presence of the basking shark Cetorhinus maximus (Lamniformes: Cetorhinidae) in the central-eastern Mediterranean Sea has been documented by means of 15 sightings and two accidental catches which occurred from February 2011 to January 2014 in the northwestern Ionian and southern Adriatic Sea. Specimens were observed exhibiting typical feeding behaviour, swimming slowly on the surface, during each sighting. In the case of the accidental catches, the basking shark specimens were released still alive by local fishermen. The observed specimens measured between 4 and 9 m in total length (TL). The sightings could be due to an increase in effort in the monitoring of the species occurring in the Mediterranean Sea as a consequence of a rise interest in the conservation of threatened species.

New Mediterranean Marine biodiversity records (December, 2013)

Based on recent biodiversity studies carried out in different parts of the Mediterranean, the following 19 species are included as new records on the floral or faunal lists of the relevant ecosystems: the green algae Penicillus capitatus (Maltese waters); the nemertean Amphiporus allucens (Iberian Peninsula, Spain); the salp Salpa maxima (Syria); the opistobranchs Felimida britoi and Berghia coerulescens (Aegean Sea, Greece); the dusky shark Carcharhinus obscurus (central-west Mediterranean and Ionian Sea, Italy); Randall’s threadfin bream Nemipterus randalli, the broadbanded cardinalfish Apogon fasciatus and the goby Gobius kolombatovici (Aegean Sea, Turkey); the reticulated leatherjack Stephanolepis diaspros and the halacarid Agaue chevreuxi (Sea of Marmara, Turkey); the slimy liagora Ganonema farinosum, the yellowstripe barracuda Sphyraena chrysotaenia, the rayed pearl oyster Pinctada imbricata radiata and the Persian conch Conomurex persicus (south-eastern Crete, Greece); the blenny Microlipophrys dalmatinus and the bastard grunt Pomadasys incisus (Ionian Sea, Italy); the brown shrimp Farfantepenaeus aztecus (north-eastern Levant, Turkey); the blue-crab Callinectes sapidus (Corfu, Ionian Sea, Greece). In addition, the findings of the following rare species improve currently available biogeographical knowledge: the oceanic pufferfish Lagocephalus lagocephalus (Malta); the yellow sea chub Kyphosus incisor (Almuñécar coast of Spain); the basking shark Cetorhinus maximus and the shortfin mako Isurus oxyrinchus (north-eastern Levant, Turkey).

Feeding associations between Grey Phalaropes Phalaropus fulicarius and Basking Sharks Cetorhinus maximus over a tidal-topographic front off southwest Cornwall

This paper documents a previously unreported feeding association between Grey Phalaropes Phalaropus fulicarius and Basking Sharks Cetorhinus maximus. The observations were made during effort-based visual monitoring from Gwennap Head in southwest Cornwall, in October 2008. Flocks of up to 50 Grey Phalaropes were seen to follow and aggregate around surface-feeding Basking Sharks, mostly in an area characterised by a prominent tidal-topographic front. It is proposed that Grey Phalaropes were initially attracted to visual manifestations of upwellings and convergence zones over and adjacent to this front (with enhanced surficial prey availability), and then opportunistically used the tall dorsal fins of foraging Basking Sharks as a visual cue to home in on particularly dense prey patches.

Electrosensory pore distribution and feeding in the basking shark Cetorhinus maximus (Lamniformes: Cetorhinidae)

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 12:33-36 (2011) - DOI: https://doi.org/10.3354/ab00328 NOTE Electrosensory pore distribution and feeding in the basking shark Cetorhinus maximus (Lamniformes: Cetorhinidae) Ryan M. Kempster*, Shaun P. Collin The UWA Oceans Institute and the School of Animal Biology, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia *Email: ryankempster@supportoursharks.com ABSTRACT: The basking shark Cetorhinus maximus is the second largest fish in the world, attaining lengths of up to 10 m. Very little is known of its sensory biology, particularly in relation to its feeding behaviour. We describe the abundance and distribution of ampullary pores over the head and propose that both the spacing and orientation of electrosensory pores enables C. maximus to use passive electroreception to track the diel vertical migrations of zooplankton that enable the shark to meet the energetic costs of ram filter feeding. KEY WORDS: Ampullae of Lorenzini · Electroreception · Filter feeding · Basking shark Full text in pdf format PreviousNextCite this article as: Kempster RM, Collin SP (2011) Electrosensory pore distribution and feeding in the basking shark Cetorhinus maximus (Lamniformes: Cetorhinidae). Aquat Biol 12:33-36. https://doi.org/10.3354/ab00328Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 12, No. 1. Online publication date: March 03, 2011 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2011 Inter-Research.

Recent incidental catch of sharks in gillnet fisheries of Newfoundland and Labrador, Canada

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 11:133-146 (2010) - DOI: https://doi.org/10.3354/esr00268 Recent incidental catch of sharks in gillnet fisheries of Newfoundland and Labrador, Canada Steven Benjamins1,*, David W. Kulka2,3, Jack Lawson2 1Dept. of Zoology, University of Otago, PO Box 56, Dunedin, New Zealand 2Fisheries and Oceans Canada, PO Box 5667, St. John’s, Newfoundland and Labrador, A1C 5X1, Canada 3Present address: 50 Fernlilly Place, Waverley, Nova Scotia B2R 1X2, Canada *Email: stevenbenjamins@yahoo.com ABSTRACT: Waters of Newfoundland and Labrador, Canada, are home to a variety of shark species, many of which have been previously reported as incidental catch in several gillnet fisheries. However, defensible estimates of incidental catch rates are unavailable. This mortality is of concern, given reports of considerable declines in abundance of several large shark species in this area. On the basis of several data sources (incidental catch rates derived using different methods of reporting; fish landings and net days as measures of effort, with fishing trips as sampling units), the total numbers of incidentally caught sharks were estimated in 8 gillnet fisheries for 2001, 2002, and 2003. Confidence intervals were estimated using resampling techniques. Most fisheries reported incidental catch of some sharks, although there were distinct differences between different fisheries in diversity and abundance of species encountered. Spiny dogfish Squalus acanthias was the most commonly captured species, occurring in various fisheries along the south coast of the island of Newfoundland. Large sharks, including basking shark Cetorhinus maximus, shortfin mako Isurus oxyrinchus, porbeagle Lamna nasus, and blue shark Prionace glauca, were reported in small numbers in all fisheries. Deepwater fisheries targeting e.g. Greenland halibut Reinhardtius hippoglossoides caught mainly sharks of the continental slope, such as Greenland shark Somniosus microcephalus, black dogfish Centroscyllium fabricii, and several other deepwater species. Catch rates of several species appear high and may warrant conservation action. For the majority, however, there is insufficient information on abundance, and sometimes even basic biology, to accurately assess the impact of this incidental mortality. KEY WORDS: Sharks · Incidental catch · Bycatch · Canada · Northwest Atlantic · Mortality · Dogfish · Gillnets Full text in pdf format PreviousNextCite this article as: Benjamins S, Kulka DW, Lawson J (2010) Recent incidental catch of sharks in gillnet fisheries of Newfoundland and Labrador, Canada. Endang Species Res 11:133-146. https://doi.org/10.3354/esr00268 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 11, No. 2. Online publication date: April 07, 2010 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2010 Inter-Research.

Transequatorial Migrations by Basking Sharks in the Western Atlantic Ocean

The world's second largest fish, the basking shark (Cetorhinus maximus), is broadly distributed in boreal to warm temperate latitudes of the Atlantic and Pacific oceans from shallow coastal waters to the open ocean. Previous satellite archival tagging in the North Atlantic has shown that basking sharks move seasonally, are often associated with productive frontal zones, and may make occasional dives to mesopelagic depths. However, basking sharks are thought to be restricted to temperate latitudes, and the extent to which they exploit deeper-water habitat remains enigmatic. Via satellite archival tags and a novel geolocation technique, we demonstrate here that basking sharks are seasonal migrants to mesopelagic tropical waters. Tagged sharks moved from temperate feeding areas off the coast of southern New England to the Bahamas, the Caribbean Sea, and onward to the coast of South America and into the Southern Hemisphere. When in these areas, basking sharks descended to mesopelagic depths and in some cases remained there for weeks to months at a time. Our results demonstrate that tropical waters are not a barrier to migratory connectivity for basking shark populations and highlight the need for global conservation efforts throughout the species range.

Ontogenetic vertebral growth patterns in the basking shark Cetorhinus maximus

Age and growth of the basking shark Cetorhinus maximus (Gunnerus) was examined using vertebral samples from 13 females (261 to 856 cm total length (TL)), 16 males (311 to 840 cm TL) and 11 specimens of unknown sex (376 to 853 cm TL). Vertebral samples were obtained worldwide from museums and institutional and private collections. Examination of multiple vertebrae from along the vertebral column of 10 specimens indicated that vertebral morphology and band pair (alter- nating opaque and translucent bands) counts changed dramatically along an individual column. Smaller sharks had similar band pair counts along the length of the vertebral column while large sharks had a difference of up to 24 band pairs between the highest and lowest count along the col- umn. Our evidence indicates that band pair deposition may be related to growth and not time in this species and thus the basking shark cannot be directly aged using vertebral band pair counts.

First record of basking shark ( Cetorhinus maximus) in Mexico?

On February 2003, in Punta Abreojos, Baja California Sur, Mexico, a basking shark ( Cetorhinus maximus ) was caught. This specimen represents the first confirmed record in Mexico and the southern most report in north-east Pacific for the basking shark.

Genetic tracking of basking shark products in international trade

AbstractMounting evidence that sharks are being over‐fished to supply shark fin markets is causing widespread concern about the sustainability of these practices. The basking shark Cetorhinus maximus, whose fins command high market prices, has proven especially sensitive to exploitation. To prevent further population declines, this species is now protected in the territorial waters of several countries, and is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES) requiring monitoring of trade in its products by all parties to CITES. Tracking trade in basking shark products, however, is often hampered by difficulties in identifying shark products to species of origin. Here, we present the development and application of a streamlined genetic forensics assay that does not require DNA sequencing to identify basking shark products. The dual‐primer, species‐specific polymerase chain reaction strategy provides diagnostic redundancy for robustness in legal venues. It is also effective for identifying basking shark products regardless of geographic origin, an important consideration, given the global distribution of the species and international sourcing of fins to the trade. Application of the assay confirmed the presence of basking shark fins in the Hong Kong and Japan markets, and indicated an apparent relationship between the Chinese fin trader category ‘Nuo Wei Tian Jiu’ and fins from basking sharks. The assay was also used in a law enforcement investigation to document illegal trade in basking shark fins in the United States where this species is prohibited from harvest and trade. These trade detections suggest that the high market value of basking shark fins is continuing to drive the exploitation, surreptitious and otherwise, of this highly threatened species, underscoring the need for improved trade monitoring. The streamlined assay developed here can assist in monitoring and conservation on a worldwide scale.

Redescription of Cetorhinicola acanthocapax Beveridge &amp; Campbell, 1988 (Cestoda: Trypanorhyncha) from the basking shark Cetorhinus maximus (Gunnerus)

Cetorhinicola acanthocapax Beveridge & Campbell, 1988 is redescribed based on adult specimens collected from a basking shark Cetorhinus maximus (Gunnerus) off the east coast of New Zealand. Both the mature and gravid segments are described for the first time, and the first scanning electron micrographs of the armature and scolex microtriches are provided. Novel features include the opening of the vagina anterior to the cirrus-sac and the extension of the vagina anterior to the cirrus-sac. Pectinate microtriches are present on the anterior quarter of the pars pedunculus scolecis scattered between filiform microtriches; the bothrial margins are covered with tridigitate microtriches, while the adherent surface of the bothria have pectinate microtriches. The additional morphological features described are consistent with a close association between Cetorhinicola Beveridge & Campbell, 1988 and the Eutetrarhynchoidea Guiart, 1927.