Leonard J. V. Compagno

Extinction risk and conservation of the world’s sharks and rays

The rapid expansion of human activities threatens ocean-wide biodiversity. Numerous marine animal populations have declined, yet it remains unclear whether these trends are symptomatic of a chronic accumulation of global marine extinction risk. We present the first systematic analysis of threat for a globally distributed lineage of 1,041 chondrichthyan fishes—sharks, rays, and chimaeras. We estimate that one-quarter are threatened according to IUCN Red List criteria due to overfishing (targeted and incidental). Large-bodied, shallow-water species are at greatest risk and five out of the seven most threatened families are rays. Overall chondrichthyan extinction risk is substantially higher than for most other vertebrates, and only one-third of species are considered safe. Population depletion has occurred throughout the world’s ice-free waters, but is particularly prevalent in the Indo-Pacific Biodiversity Triangle and Mediterranean Sea. Improved management of fisheries and trade is urgently needed to avoid extinctions and promote population recovery. DOI: http://dx.doi.org/10.7554/eLife.00590.001

Sharks of the order Carcharhiniformes

This book is a general review, taxonomic revision, and phylogenetic analysis of the carcharhinoids, the largest group of living sharks, which comprises almost 60 percent or 200 of known shark species. Students of shark biology have been hampered by the lack of just such a comprehensive and rigorous account of shark morphology. With this work L.J.V. Compagno offers not only the most comprehensive and detailed account of this important but neglected group to date but also one of the most comprehensive modern anatomical and phylogenetic studies on cartilaginous fishes available. It will become an essential reference not only for researchers on carcharhinoids but also for those who study other families of sharks and for paleontologists interested in this ancient group of fishes. The book begins with a general account of carcharhinoid sharks. Chapters Two through Eleven include detailed discussions of character systems used in taxonomic and phylogenetic analysis of carcharhinoids. Chapter Twelve defines the Order Carcharhiniformes, lists its families, and includes a taxonomic key to the families. Chapters Thirteen through Twenty review the eight carcharhinoid families, and Chapter Twenty-One is an extended discussion of the phylogeny of carcharhinoids, with cladistic analysis of taxa at various levels.

Alternative life-history styles of cartilaginous fishes in time and space

Cartilaginous fishes, the sharks, rays and chimaeras (class Chondrichthyes), are a very old and successful group of jawed fishes that currently contains between 900 and 1100 known living species. Chondrichthyians show a high morphological diversity during most of their evolutionary career from the Paleozoic to the present day. They are relatively large predators which have remained a major, competitive element of marine ecosystems despite the varied rivalry of numerous other marine vertebrate groups over at least 400 million years. Although restricted in their ecological roles by morphology, reproduction and other factors, the living cartilaginous fishes are highly diverse and show numerous alternative life-history styles which are multiple answers to exploiting available niches permitted by chondrichthyian limitations. Chondrichthyians living and fossil can be divided into at least eighteen ecomorphotypes, of which the littoral ecomorphotype is perhaps the most primitive and can serve as an evolutionary origin for numerous specialist ecomorphotypes with benthic, high-speed, superpredatory, deep-slope and oceanic components. Reproductive modes in cartilaginous fishes are of six types, ranging from primitive extended oviparity through retained oviparity and yolk-sac viviparity (previously ovoviviparity) to three derived forms of viviparity. Reproductive modes are not strongly correlated with ecomorphotypes and with the phylogeny of living elasmobranchs. The success and importance of cartilaginous fishes is largely underrated by marine biologists and by the public, and requires new and ‘heretical’ emphasis to overcome the present inadequacies of chondrichthyian research and the problems of overexploitation that cartilaginous fishes face.

Predation by White Sharks Carcharodon carcharias (Chondrichthyes: Lamnidae) Upon Chelonians, with New Records from the Mediterranean Sea and a First Record of the Ocean Sunfish Mola mola (Osteichthyes: Molidae) as Stomach Contents

The occurrence of marine turtles in the diet of white sharks, Carcharodon carcharias, is reviewed worldwide. Four records of chelonians eaten by white sharks in the Mediterranean Sea are described, which on the basis of carapace remnants confirmed both the loggerhead Caretta caretta and green turtle Chelonia mydas to be preyed upon in those waters. The condition of these remains indicates that large white sharks can ingest turtles essentially intact. As well as falling prey to white sharks, we suspect that some interactions involve turtles being ‘grab-released’ in a non-predatory mannner and their survivability from such low-intensity bites or other mouthings may be quite high. The white shark may be the chief marine predator of adult chelonians in the Mediterranean Sea, albeit the impact of this predation upon turtle populations is nominal compared to other sources of mortality. Further, we give an account describing an adult ocean sunfish, Mola mola, in the stomach of a white shark taken in Italian waters.

A preliminary investigation of the feeding ecology of skates (Batoidea: Rajidae) off the west coast of southern Africa

The diets of 14 species of skates (Rajiformes: Rajidae) collected along the coast of South-Western Africa between Walvis Bay and Cape Agulhas over a depth range of 50–1 016 m were analysed. Two distinct communities of skates could be recognized on the basis of depth zonation, the boundary between these communities being at approximately 380 m water depth. These two skate communities have similar species components: the so-called biscuit skate community (the shallow one) has two crustacean specialists (Cruriraja parcomaculata, Raja wallacei), one fish specialist (R. alba) and two generalists (R. pullopunctata, R. cf. clavata); the so-named grey skate community has two crustacean specialists (Raja caudaspinosa, R. confundens) and two generalists (Bathyraja smithii, R. leopardus). The grey skate community appears to be a more complex and dynamic assemblage with higher diversity (at least 13 species) than the biscuit skate community (five species). In both communities the most common prey items were crustacea...

Distribution of offshore demersal cartilaginous fish (Class Chondrichthyes) off the west coast of southern Africa, with notes on their systematics

The geographic and the bathymetric distribution of offshore demersal cartilaginous fish off the west coast of southern Africa are reviewed. The results were collected during 12 cruises of F.R.S. Africana between 1986 and 1990. The area covered was between Walvis Bay (23°S, 14°E) and the Agulhas Bank west of Cape Agulhas (36°S, 20°E) over a depth range of 33–1 016 m. In all, 55 species of cartilaginous fish were collected, including 32 sharks, 17 rays and six chimaeras, on 869 stations and representing 3 092 station records. Computer-generated maps and station lists are presented for the species in the sample, and the distribution records, including records from the literature, are reviewed and discussed for these species and 12 more demersal species not collected during the survey. The survey revealed many range extensions for described species. West Coast demersal cartilaginous fish show zonation by depth and latitude, and groups of species with similar depth and latitudinal distributions were apparent. ...

Recent strandings and sightings of whale sharks in South Africa

Available information on whale shark strandings around the coast of South Africa during the period 1984–1995 was collated. Stranded animals ranged in size from 3–11 m TL, most were immature and the sex ratio was even. Aerial observations and sightings by divers indicate that whale sharks are most abundant in South African waters during the austral summer and autumn months.

A preliminary investigation of the feeding ecology of squaloid sharks off the west coast of southern Africa

The diets of 15 species of squaloid sharks caught between Walvis Bay and Cape Agulhas over a depth range of 50–1 016 m are analysed. The most common prey items were fish and cephalopods. Hake Merluccius spp. were common in the diets of Centrophorus squamosus, Squalus acanthias, and S. cf. mitsukurii. Myctophids were extensively preyed on by Centroscyllium fabricii, Deania calcea, D. profundorum, Etmopterus cf. brachyurus, E. compagnoi, S. acanthias and S. megalops, among others. The most common cephalopods in shark stomachs were Histioteuthis miranda, Lycoteuthis ?diadema, Octopus vulgaris and Todarodes angolensis. Crustaceans were uncommon prey of most species, except for Centroscyllium fabricii and Etmopterus cf. granulosus. Centroscymnus coelolepis was the only squaloid with cetacean remains in the stomach. That species appears to parasitize its cetacean victims.

AN OVERVIEW OF CHONDRICHTHYAN SYSTEMATICS AND BIODIVERSITY IN SOUTHERN AFRICA

SUMMARY Southern Africa, including South Africa, Namibia, and Mozambique, has a highly diverse fauna of cartilaginous fishes (Class Chondrichthyes), including sharks, rays or ‘flat sharks’, and chimaeras or ‘silver sharks’. All orders, most families, and approximately 210 species of cartilaginous fishes occur in the area, of which 54 are endemics. The paper gives an overview of known diversity of cartilaginous fishes in the area and discusses their classification, distribution, habitats and ecomorphotypes. It also gives a history of chondrichthyan systematics in southern Africa from Linnaeus to the present, analyses the systematic status of the fauna, and discusses future directions for research.

A review of the systematics of the sleeper shark genus Somniosus with redescriptions of Somniosus (Somniosus) antarcticus and Somniosus (Rhinoscymnus) longus (Squaliformes: Somniosidae)

Past treatments of the sleeper shark genus Somniosus generally recognize three species: S. microcephalus, S. pacificus, and S. rostratus. Based on morphometrics and meristics, we conclude that this genus includes two subgenera (Somniosus and Rhinoscymnus) and five species. Subgenus Somniosus differs from Rhinoscymnus by being much larger when adult and in having more numerous tooth rows in the lower jaw, hooklike rather than leaf-shaped dermal denticles, more numerous spiral valve and vertebral counts, and a poorly calcified vertebral column. Subgenus Somniosus includes S. (Somniosus) microcephalus and S. (S.) pacificus of the Northern Hemisphere and S. (S.) antarcticus of the Southern Hemisphere. Although Somniosus antarcticus has been synonymized with S. microcephalus and identified as S. pacificus in past literature, it differs from S. microcephalus in having a shorter interdorsal space, a more posterior first dorsal fin, lower dorsal fins, more numerous tooth rows in the lower jaw, more numerous spiral valve counts, and fewer precaudal vertebrae. Somniosus antarcticus also differs from S. pacificus by having a shorter prebranchial length, lower dorsal fins, more numerous spiral valve counts, and slightly more precaudal vertebrae. Subgenus Rhinoscymnus includes S. (Rhinoscymnus) rostratus from the eastern North Atlantic and Mediterranean Sea (senior synonym of S. bauchotae) and S. (R.) longus from the western Pacific Ocean. Somniosus longus has been synonymized with S. rostratus, but differs in having a relatively longer second dorsal fin, a slightly larger eye, more lower tooth rows, and slightly higher spiral valve counts. Both Somniosus (Somniosus) antarcticus and S. (Rhinoscymnus) longus from the Pacific Ocean were redescribed. A key to the species and the geographical distribution of all species are provided.