Evidence of egg laying grounds for critically endangered flapper skate (Dipturus intermedius) off Orkney, UK

Funding information: Surveys were supported by a grant from WWF Netherlands. The writing of this paper was funded via the SeaMonitor project; supported by the European Union’s INTERREG VA Programme (Environment Theme) and managed by the Special EU Programmes Body (SEUPB) (Grant IVA5060).Essential fish habitats (EFHs) are critical for fish life-history events, including spawning, breeding, feeding or growth. Here we provide evidence of EFH for the Critically Endangered flapper skate (Dipturus intermedius) in the waters around the Orkney Isles, Scotland based on citizen-science observation data. The habitats of potential egg laying sites were parametrised as >20m depth, with boulders or exposed bedrock, in moderate current flow (0.3 - 2.8 knots) with low sedimentation. This information provides a significant contribution to our understanding of EFH for flapper skate. Publisher PDFPeer reviewe

A holistic and comprensive data approach validates the distribution of the critically endangered flapper skate (Dipturus intermedius)

Morphological similarities between skates of the genus Dipturus in the north-eastern Atlantic and mediterranean have resulted in longstanding confusion, misidentification and misreporting. Current evidence indicates that the common skate is best explained as two species, the flapper skate (Dipturus intermedius) and the common blue skate (D. batis). However, some management and conservation initiatives developed prior to the separation continue to refer to common skate (as ‘D. batis’). This taxonomic uncertainty can lead to errors in estimating population viability, distribution range, and impact on fisheries management and conservation status. Here, we demonstrate how a concerted taxonomic approach, using molecular data and a combination of survey, angler and fisheries data, in addition to expert witness statements, can be used to build a higher resolution picture of the current distribution of D. intermedius. Collated data indicate that flapper skate has a more constrained distribution compared to the perceived distribution of the ‘common skate’, with most observations recorded from Norway and the western and northern seaboards of Ireland and Scotland, with occasional specimens from Portugal and the Azores. Overall, the revised spatial distribution of D. intermedius has significantly reduced the extant range of the species, indicating a possibly fragmented distribution range.acceptedVersio

A holistic and comprehensive data approach validates the distribution of the critically endangered flapper skate (Dipturus intermedius)

Morphological similarities between skates of the genus Dipturus in the north-eastern Atlantic and Mediterranean have resulted in longstanding confusion, misidentification and misreporting. Current evidence indicates that the common skate is best explained as two species, the flapper skate (Dipturus intermedius) and the common blue skate (D. batis). However, some management and conservation initiatives developed prior to the separation continue to refer to common skate (as ‘D. batis’). This taxonomic uncertainty can lead to errors in estimating population viability, distribution range, and impact on fisheries management and conservation status. Here, we demonstrate how a concerted taxonomic approach, using molecular data and a combination of survey, angler and fisheries data, in addition to expert witness statements, can be used to build a higher resolution picture of the current distribution of D. intermedius. Collated data indicate that flapper skate has a more constrained distribution compared to the perceived distribution of the ‘common skate’, with most observations recorded from Norway and the western and northern seaboards of Ireland and Scotland, with occasional specimens from Portugal and the Azores. Overall, the revised spatial distribution of D. intermedius has significantly reduced the extant range of the species, indicating a possibly fragmented distribution range

Assessing the potential of acoustic telemetry to underpin the regional management of basking sharks (Cetorhinus maximus)

Acoustic telemetry can provide valuable space-use data for a range of marine species. Yet the deployment of species-specific arrays over vast areas to gather data on highly migratory vertebrates poses formidable challenges, often rendering it impractical. To address this issue, we pioneered the use of acoustic telemetry on basking sharks (Cetorhinus maximus) to test the feasibility of using broadscale, multi-project acoustic receiver arrays to track the movements of this species of high conservation concern through the coastal waters of Ireland, Northern Ireland, and Scotland. Throughout 2021 and 2022, we tagged 35 basking sharks with acoustic transmitters off the west coast of Ireland; 27 of these were detected by 96 receiver stations throughout the study area (n = 9 arrays) with up to 216 detections of an individual shark (mean = 84, s.d. 65). On average, sharks spent ~ 1 day at each acoustic array, with discrete residency periods of up to nine days. Twenty-one sharks were detected at multiple arrays with evidence of inter-annual site fidelity, with the same individuals returning to the same locations in Ireland and Scotland over 2 years. Eight pairs of sharks were detected within 24 h of each other at consecutive arrays, suggesting some level of social coordination and synchronised movement. These findings demonstrate how multi-project acoustic telemetry can support international, cost-effective monitoring of basking sharks and other highly mobile species. Decision support tools such as these can consolidate cross-border management strategies, but to achieve this goal, collaborative efforts across jurisdictions are necessary to establish the required infrastructure and secure ongoing support

Biodiversity Assessment, DNA Barcoding, and the Minority Majority

The majority of species on Earth are in "under-studied" groups, and indeed probably the majority of species remain undiscovered and undescribed. Species are natural units of evolution, and they are formed from branching phylogenetic processes that have a mathematical structure. So it follows that we should be able to develop a set of general principles that describe global patterns of species groups, like genera. Understanding such patterns would lend considerable power to the approach of "taxonomic surrogacy." In environmental assessments, ecology, and paleontology, it is common to substitute genus-level or family-level identification where definitive species identification is impractical. Clarity and confidence in fundamental patterns, based on a robust null model for species and genus level diversity, can accelerate species discovery: there are more species in the tropics, species-poor genera are very common, large genera are rare. Much hope has been placed in DNA barcoding as an effective tool to increase the pace of species discovery, but it is abundantly clear that certain mitochondrial DNA (mtDNA) markers are more or less variable in different clades and universal threshold values are impractical to delimit species. This study further examines the patterns of divergence in one common mtDNA barcode fragment, cytochrome c oxidase subunit 1at the genus level. We compared pairwise divergence in this fragment between two animal clades that have similar species richness but different evolutionary histories: birds and bivalves. We analyzed quality controlled alignments of over 39,000 published sequences in 1223 genera. Median pairwise differences at the genus level are positively correlated with the species richness of a genus, and this is not dependent of the number of sequences sampled. Unsurprisingly, sequence divergence in vertebrates was far more constrained than in evolutionarily more ancient non-vertebrate clades. Differences among the groups examined highlight the need for DNA barcode approaches to be considered in the context of specific biological groups. Vertebrates are better studied, but not necessarily representative of the majority of biodiversity. A technique that provides powerful insights for vertebrate species may be ineffective for the majority of organisms.</p

Preliminary insight into the reproductive traits of the flapper skate (Dipturus intermedius) using in-field ultrasonography and circulating hormone concentrations

Due to global population declines, there is a pressing need for data on the life history traits of many elasmobranch species to support the development of species-specific management plans. A lack of information on the reproductive cycle of the Critically Endangered flapper skate (Dipturus intermedius) was recently identified as a hindrance to its conservation. To address this data gap by combining non-lethal ultrasound and hormone analysis to investigate the size at maturity and reproductive cycle of the flapper skate in the Loch Sunart to the Sound of Jura Marine Protected Area off the west coast of Scotland. In-field ultrasound imagery revealed in-utero encapsulated eggs and was used to determine the presence and size of ovarian follicles. Combining these images with levels of plasma testosterone, progesterone, and oestradiol provided valuable insights into the timing of the reproductive cycle and maturity state of the flapper skate. This preliminary study suggests that male skate start to mature at 165 cm and female skate at 203 cm total length. Oestradiol appears to be the primary hormone controlling the female reproductive cycle and, along with ultrasound images, indicate that females lay pairs of eggs throughout a winter egg-laying season. This study further highlights how non-lethal investigation methods can be used to investigate the life history of oviparous elasmobranchs in the field. This information will support the identification of important life history groups and their associated habitats, helping to develop management strategies for these species