279 research outputs found
One-pot near-ambient temperature syntheses of aryl(difluoroenol) derivatives from trifluoroethanol
Difluoroalkenylzinc reagents prepared from 1-(2’-methoxy-ethoxymethoxy)-2,2,2-trifluoroethane and 1-(N,N-diethylcarbamoyloxy)-2,2,2-trifluoroethane at ice bath temperatures, underwent Negishi coupling with a range of aryl halides in a convenient one pot procedure. While significant differences between the enol acetal and carbamate reagents were revealed, the Negishi protocol compared very favourably with alternative coupling procedures in terms of overall yields from trifluoroethanol
Speckled Catshark Halaelurus boesemani
The Speckled Catshark (Halaelurus boesemani) is a relatively small (to 48 cm total length), data-poor
catshark. It is known from a limited number of specimens collected from four locations along an ~900
km stretch of Somali coastline. It occurs on continental and insular shelves at depths of 29-91 m. Its
entire distribution has been subject to at least four decades of unregulated commercial benthic
trawling; shelf-occurring catsharks are very susceptible to capture in this fishing gear. The new Somali
Fisheries Law bans benthic trawling, but it is suspected that past declines have already occurred given
the long history of unregulated fishing across its entire range. Furthermore, enforcement of this new
regulation will be a challenge. While specific data are lacking, a population size reduction of 30-50% is
suspected over the past three generations (~45 years) based on actual levels of exploitation (bycatch)
and the species is assessed as Vulnerable A2d. It is of concern that there have been no records since
1991, although it is acknowledged that research and monitoring have been limited in Somalia. Further
investigation of this species is required to accurately define its range, biology, extent of catches in local
fisheries and levels of declines. This assessment should be revisited as soon as this is available
Smallbelly Catshark Apristurus indicus
The Speckled Catshark (Halaelurus boesemani) is a relatively small (to 48 cm total length), data-poor
catshark. It is known from a limited number of specimens collected from four locations along an ~900
km stretch of Somali coastline. It occurs on continental and insular shelves at depths of 29-91 m. Its
entire distribution has been subject to at least four decades of unregulated commercial benthic
trawling; shelf-occurring catsharks are very susceptible to capture in this fishing gear. The new Somali
Fisheries Law bans benthic trawling, but it is suspected that past declines have already occurred given
the long history of unregulated fishing across its entire range. Furthermore, enforcement of this new
regulation will be a challenge. While specific data are lacking, a population size reduction of 30-50% is
suspected over the past three generations (~45 years) based on actual levels of exploitation (bycatch)
and the species is assessed as Vulnerable A2d. It is of concern that there have been no records since
1991, although it is acknowledged that research and monitoring have been limited in Somalia. Further
investigation of this species is required to accurately define its range, biology, extent of catches in local
fisheries and levels of declines. This assessment should be revisited as soon as this is available
Troubled Waters: Threats and Extinction Risk of the Sharks, Rays and Chimaeras of the Arabian Sea and Adjacent Waters
The extinction risk of sharks, rays and chimaeras is higher than that for most other vertebrates due to low intrinsic population growth rates of many species and the fishing intensity they face. The Arabian Sea and adjacent waters border some of the most important chondrichthyan fishing and trading nations globally, yet there has been no previous attempt to assess the conservation status of species occurring here. Using IUCN Red List of Threatened Species Categories and Criteria and their guidelines for application at the regional level, we present the first assessment of extinction risk for 153 species of sharks, rays and chimaeras. Results indicate that this region, home to 15% of described chondrichthyans including 30 endemic species, has some of the most threatened chondrichthyan populations in the world. Seventy-eight species (50.9%) were assessed as threatened (Critically Endangered, Endangered or Vulnerable), and 27 species (17.6%) as Near Threatened. Twenty-nine species (19%) were Data Deficient with insufficient information to assess their status. Chondrichthyan populations have significantly declined due to largely uncontrolled and unregulated fisheries combined with habitat degradation. Further, there is limited political will and national and regional capacities to assess, manage, conserve or rebuild stocks. Outside the few deepsea locations that are lightly exploited, the prognosis for the recovery of most species is poor in the near-absence of management. Concerted national and regional management measures are urgently needed to ensure extinctions are avoided, the sustainability of more productive species is secured, and to avoid the continued thinning of the regional food security portfolio
Putting sharks on the map: A global standard for improving shark area-based conservation
Area-based conservation is essential to safeguard declining biodiversity. Several approaches have been developed for identifying networks of globally important areas based on the delineation of sites or seascapes of importance for various elements of biodiversity (e.g., birds, marine mammals). Sharks, rays, and chimaeras are facing a biodiversity crisis with an estimated 37% of species threatened with extinction driven by overfishing. Yet spatial planning tools often fail to consider the habitat needs critical for their survival. The Important Shark and Ray Area (ISRA) approach is proposed as a response to the dire global status of sharks, rays, and chimaeras. A set of four globally standardized scientific criteria, with seven sub-criteria, was developed based on input collated during four shark, biodiversity, and policy expert workshops conducted in 2022. The ISRA Criteria provide a framework to identify discrete, three-dimensional portions of habitat important for one or more shark, ray, or chimaera species, that have the potential to be delineated and managed for conservation. The ISRA Criteria can be applied to all environments where sharks occur (marine, estuarine, and freshwater) and consider the diversity of species, their complex behaviors and ecology, and biological needs. The identification of ISRAs will guide the development, design, and application of area-based conservation initiatives for sharks, rays, and chimaeras, and contribute to their recovery
Elemental analysis of vertebrae discerns diadromous movements of threatened non-marine elasmobranchs
River sharks (Glyphis spp.) and some sawfishes (Pristidae) inhabit riverine environments, although their long-term habitat use patterns are poorly known. We investigated the diadromous movements of the northern river shark (Glyphis garricki), speartooth shark (Glyphis glyphis), narrow sawfish (Anoxypristis cuspidata), and largetooth sawfish (Pristis pristis) using in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on vertebrae to recover elemental ratios over each individual's lifetime. We also measured elemental ratios for the bull shark (Carcharhinus leucas) and a range of inshore and offshore stenohaline marine species to assist in interpretation of results. Barium (Ba) was found to be an effective indicator of freshwater use, whereas lithium (Li) and strontium (Sr) were effective indicators of marine water use. The relationships between Ba and Li and Ba and Sr were negatively correlated, whereas the relationship between Li and Sr was positively correlated. Both river shark species had elemental signatures indicative of prolonged use of upper-estuarine environments, whereas adults appear to mainly use lower-estuarine environments rather than marine environments. Decreases in Li:Ba and Sr:Ba at the end of the prenatal growth zone of P. pristis samples indicated that parturition likely occurs in fresh water. There was limited evidence of prolonged riverine habitat use for A. cuspidata. The results of this study support elemental–environment relationships observed in teleost otoliths and indicate that in situ LA-ICP-MS elemental characterization is applicable to a wide range of elasmobranch species as a discriminator for use and movement across salinity gradients. A greater understanding of processes that lead to element incorporation in vertebrae, and relative concentrations in vertebrae with respect to the ambient environment, will improve the applicability of elemental analysis to understand movements across the life history of elasmobranchs into the future
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