Chondrichthyans (sharks, skates, rays and chimaeras) are captured in many marine fisheries. Management and research efforts directed at chondrichthyan fishing are often neglected because of low ...product value, taxonomic uncertainty, low capture rates, and harvesting by multiple fisheries. In South Africa's diverse fishery sectors, which include artisanal as well as highly industrialised fisheries, 99 (49%) of 204 chondrichthyan species that occur in southern Africa are targeted regularly or taken as bycatch. Total reported dressed catch for 2010, 2011 and 2012 was estimated to be 3 375 t, 3 241 t and 2 527 t, respectively. Two‑thirds of the reported catch was bycatch. Regulations aimed at limiting chondrichthyan catches, coupled with species‑specific permit conditions, currently exist in the following fisheries: demersal shark longline, pelagic longline, recreational line, and beach‑seine and gillnet. Limited management measures are currently in place for chondrichthyans captured in other South African fisheries. Catch and effort dataseries suitable for stock assessments exist for fewer than 10 species. Stock assessments have been attempted for five shark species: soupfin Galeorhinus galeus , smoothhound Mustelus mustelus , white Carcharodon carcharias , spotted ragged‑tooth Carcharias taurus , and spotted gully Triakis megalopterus . Fishery‑independent surveys and fishery observer data, which can be used as a measure of relative abundance, exist for 67 species. Compared with most developing countries, South African shark fishing is relatively well controlled and managed. As elsewhere, incidental capture and bycatch remain challenges to the appropriate management of shark species. In 2013, South Africa's National Plan of Action for the Conservation and Management of Sharks (NPOA‑Sharks) was published. Implementation of the NPOA‑Sharks should help to improve chondrichthyan management in the near future.
The Paleo-Tokyo Bay (Kanto Plateau) that persisted during the transgression periods in the Middle-Late Pleistocene is known for its rich marine fauna that accommodated both the warm and cold water ...taxa brought by the Kuroshio and Oyashio Currents, respectively. However, little is known on the paleoichthyofauna in this area and the processes shaping the marine ichthyofauna of modern southern Kanto. We used fossil fish otoliths and teeth discovered in the Sha’ana Tuffaceous Sand Member belonging to the Chibanian Miyata Formation, exposed at Sha’ana-dai, Miura City, Kanagawa Prefecture, Japan, to reconstruct the paleoichthyofauna and its associated paleoenvironment and explore the content of fish assemblages during this period. The Sha’ana Tuffaceous Sand Member was composed of upper sandy mud and lower muddy sand horizons at the exposure. A total of 1,675 fish remains were collected from this site, of which 1,389 were assigned to 62 distinct taxa (20 orders, 31 families). The taxonomic composition revealed taxa from various environments, including shallow continental shelf, epi- to meso-pelagic settings, and the majority were from a generally temperate climatic zone. Paleoenvironmental analyses suggested that the fish assemblages were from the continental shelf (approximate depth of 100–200 m) in a temperate sea where both warm Kuroshio and cold Oyashio Currents had an influence on the biota. The analysis also showed that two boreal fishes, namely Clupea pallasii and Theragra chalcogramma, once had a wider distribution that extended to the southwestern areas of the Paleo-Tokyo Bay. This study provides a more complete view of the related paleobiogeography of marine fishes during the Chibanian and is essential for reconstructing the evolutionary processes of the rich ichthyofauna in the southern Kanto.
Chondrichthyes (sharks, rays, ratfish and their extinct relatives) originated and diversified in the Palaeozoic but are rarely preserved as articulated or partly articulated remains because of their ...predominantly cartilaginous endoskeletons. Consequently, their evolutionary history is perceived to be documented predominantly by isolated teeth, scales and fin spines. Here, we aim to capture and analyse the quality of the Palaeozoic chondrichthyan fossil record by using a variation of the skeletal completeness metric, which calculates how complete the skeletons of individuals are compared to estimates of their original entirety. Notably, chondrichthyan completeness is significantly lower than any published vertebrate group: low throughout the Silurian and Permian but peaking in the Devonian and Carboniferous. Scores increase to a range similar to pelycosaurs and parareptiles only when taxa identified solely from isolated teeth, scales and spines are excluded. We argue that environmental influences probably played an important role in chondrichthyan completeness. Sea level significantly negatively correlates with chondrichthyan completeness records and resembles patterns already evident in records of ichthyosaurs, plesiosaurs and sauropodomorphs. Such observed variations in completeness highlight the impact of different sampling biases on the chondrichthyan fossil record and the need to acknowledge these when inferring patterns of chondrichthyan macroevolution.
Vertebrate microfossil bonebeds (VMBs)—localized concentrations of small resilient vertebrate hard parts—are commonly studied to recover otherwise rarely found small-bodied taxa, and to document ...relative taxonomic abundance and species richness in ancient vertebrate communities. Analyses of taphonomic comparability among VMBs have often found significant differences in size and shape distributions, and thus considered them to be non-isotaphonomic. Such outcomes of “strict” statistical tests of isotaphonomy suggest discouraging limits on the potential for broad, comparative paleoecological reconstruction using VMBs. Yet it is not surprising that sensitive statistical tests highlight variations among VMB sites, especially given the general lack of clarity with regard to the definition of “strict” isotaphonomic comparability. We rigorously sampled and compared six VMB localities representing two distinct paleoenvironments (channel and pond/lake) of the Upper Cretaceous Judith River Formation to evaluate biases related to sampling strategies and depositional context. Few defining distinctions in bioclast size and shape are evident in surface collections, and most site-to-site comparisons of sieved collections are indistinguishable (p≤ 0.003). These results provide a strong case for taphonomic equivalence among the majority of Judith River VMBs, and bode well for future studies of paleoecology, particularly in relation to investigations of faunal membership and community structure in Late Cretaceous wetland ecosystems. The taphonomic comparability of pond/lake and channel-hosted VMBs in the Judith River Formation is also consistent with a formative model that contends that channel-hosted VMBs were reworked from pre-existing pond/lake assemblages, and thus share taphonomic history.
This paper blends conservation science with legal and policy analysis to assess the primary threats to global shark populations and explores innovative approaches to conservation building upon the ...philosophy of Earth law, including the Rights of Nature legal framework. Using a case study of Panamá’s national Rights of Nature law, this paper highlights approaches to improve the protection and restoration of shark populations and their habitats. By examining the ecological, social, and economic aspects of conservation holistically, this study offers an interdisciplinary perspective on the urgency for shark protection and presents Rights of Nature as a valuable approach to shark conservation, with potential applications to other species globally.
Southern Africa has one of the richest and most diverse chondrichthyan faunas in the world, comprising all 13 orders, 49 families, 111 genera and approximately 204 species. This represents nearly 20% ...of all known chondrichthyans, and includes 117 shark, 79 batoid and 8 chimaera species. A greater diversity of chondrichthyan species is seen on the east coast (n = 175) compared to the west coast (n = 96), especially among the families Carcharhinidae and Dasyatidae. The cumulative number of species added to the fauna has increased over the past 112 years from 28 to 204. A golden age of southern African chondrichthyan research occurred between 1967 and 1976 when 46 species were added to the fauna, 16 of which were newly described. A total of 5 families, 23 genera and 130 species have been described from southern Africa. Three families, 17 genera and 75 species are still considered valid. In all, 59 researchers have authored new species descriptions of southern African chondrichthyans, with 95 of 130 species being described by just 14 authors. The most new species described were by JLB Smith with 18, followed by J Müller and FGJ Henle, who collaborated to author 12 new species descriptions. A review of the conservation status of 189 chondrichthyan species indicates that 29% have been assessed as Vulnerable or higher (more threatened), a much higher percentage than the 17.4% of chondrichthyans globally. Of particular concern is that 13% are species endemic to southern Africa. Despite increased chondrichthyan awareness and popularity, most research and conservation efforts centre on a few charismatic species, while the future of little-known species remains ‘lost’ from the public and scientific consciousness.
The fossil record of chondrichthyans in Argentina is still poorly known. The aim of the present contribution is to describe teeth representing a chondrichthyan assemblage from Man Aike Formation ...(late Eocene) exposed in the Lago Argentino area, at Santa Cruz province, Argentina. This report includes Striatolamia macrota, Macrorhizodus praecursor, Carcharias sp., a possible member of the family Pristiophoridae, for the Argentine territory. Previous Eocene reports of Striatolamia macrota from Argentina are based on incorrect determination of specimens. The shark association, especially the abundance of lamniforms, may be indicative of litoral and shallow (less than 30 m depth) temperate to cold waters, as suggested by micropaleontological content.
•For the first time a late Eocene chondrichthyan assemblage is described from Santa Cruz province, Argentina.•Striatolamia macrota, Macrorhizodus praecursor, Carcharias sp., and Pristiophoridae are reported.•Species here described are frequent in fish faunas from the North Atlantic seas.
Many sharks, skates, and rays (elasmobranchs) are highly threatened by the activities of commercial fisheries, and a clear understanding of their distributions, diversity, and abundance can guide ...protective measures. However, surveying and monitoring elasmobranch species can be highly invasive or resource‐intensive, and utilization of non‐invasive environmental DNA‐based methods may overcome these problems. Here, we studied spatial and seasonal variation in the elasmobranch community of the Western English Channel using environmental DNA (eDNA) collected from surface and bottom waters periodically over an annual cycle (2017–2018). In total we recovered 13 elasmobranch species within eDNA samples, and the number of transformed eDNA reads was positively associated with species (hourly) catch data resolved from 105‐year time series trawl data (1914–2018). These results demonstrate the ability of eDNA to detect and semi‐quantitatively reflect the prevalence of historically dominant and rare elasmobranch species in this region. Notably, eDNA recorded a greater number of species per sampling event than a conventional trawl survey in the same area over the same sampling years (2017–2018). Several threatened species were recovered within the eDNA, including undulate ray, porbeagle shark, and thresher shark. Using eDNA, we found differences in elasmobranch communities among sampling stations and between seasons, but not between sampling depths. Collectively, our results suggest that non‐invasive eDNA‐based methods can be used to study the spatial and seasonal changes in the diversity and abundance of whole elasmobranch communities within temperate shelf habitats. Given the threatened status of many elasmobranchs in human‐impacted marine environments, eDNA analysis is poised to provide key information on their diversity and distributions to inform conservation‐focused monitoring and management.
Sharks, skates, and rays are highly threatened by commercial fisheries, and reliable information on species distributions and diversity can guide protective measures. Here, we evaluated the ability of environmental DNA (eDNA) to quantify the diversity of sharks, skates, and rays of the English Channel. We found eDNA was able to reflect the relative abundance of species and detect threatened species, suggesting a future role of eDNA in monitoring and management of this species group.
The lLate Miocene Chagres Formation from northern Panama contains the youngest outcrops of the Panama Canal Basin. Here we report two chondrichthyan assemblages that include 30 taxa from both the Rio ...Indio and Chagres Sandstone Members of the Chagres Formation. We report 18 new fossil records for Panama and four for tropical America, constituting the most diverse chondrichthyan association for the Cenozoic of Panama. We performed a paleobathymetry analysis based on the modern water depth preference of extant chondrichthyan taxa. The assemblage from the Rio Indio Member is characterized by taxa with neritic affinities, suggesting depths <100 m, whereas the assemblage from the Chagres Sandstone Member is dominated by taxa with oceanic affinities, suggesting 200–300 m water depths. The Chagres Sandstone Member could have accumulated at the edge of a platform–upper slope, bordered by a deep oceanic margin.
•We describe a new chondrychthyan fauna from the Chagres Formation, Panama.•The chondrychthyan assemblage includes 30 taxa from Rio Indio and Chagres Sandstone member with 18 new records for Panama and four for tropical America.•The Rio Indio is characterized by taxa with neritic affinities and the Chagres Sandstone is dominated by taxa with oceanic affinities.
