Incorporation of human-wildlife interactions in ecosystem-based management to enhance conservation of endangered guitarfish

Growing human use of the marine environment increases the proximity of humans to marine wildlife and thus likely increases human-wildlife interactions. Such interactions influence perceptions of nature and promote or undermine conservation. Despite their importance, human-wildlife interactions are rarely considered in ecosystem-based marine spatial planning (MSP). Ideally, these interactions should be identified and considered in ecosystem-based management (EBM), which is often purported to be the basis for MSP. We used Marxan software and data from a citizen science project documenting location, species, age, sex, and activity type to identify regions along Israel's coast with a high probability of encounters between people and 2 species of guitarfish. We considered the geographic distribution of these encounters and the various activities undertaken by the reporting observers. We ran 4 scenarios in Marxan. Two had conservation goals of 30% and 50% guitarfish habitat protection. In the third and fourth scenarios, we added a 50% conservation goal of human leisure activities to each guitarfish conservation goal. We also conducted a gap analysis between our guitarfish conservation goals and the Israel Nature and Parks Authority's master plan for marine protected areas. We found the park authority was close to meeting the 30% goal but was far from meeting the conservation goal of 50% of guitarfish habitat conservation. Different human uses were more likely to interact with different life stages of guitarfish, and different recreational activities occurred in different areas. Identifying areas of specific human use showed which activities should be addressed in conservation management decisions. Our addition of certain recreational uses to the model of habitat conservation showed how enhancing human dimensions in conservation planning can lead to more holistic ecosystem-based conservation necessary for effective marine planning.

Diet of the critically endangered blackchin guitarfish Glaucostegus cemiculus revealed using DNA metabarcoding

We present the first assessment of the diet of the blackchin guitarfish Glaucostegus cemiculus (Geoffroy Saint-Hilaire, 1817) for West Africa using DNA metabarcoding on stomach contents of individuals captured in the Bijagós Archipelago, Guinea-Bissau. The diet was dominated by crustaceans, particularly caramote prawn Penaeus kerathurus (frequency of occurrence [FO] = 74%, numerical frequency [NF] = 54%) and fiddler crab Afruca tangeri (FO = 74%, NF = 12%). Bony fishes were present in 30% of the stomachs. We highlight the importance of conservation action for intertidal habitats and their associated benthic invertebrates for the survival of the critically endangered blackchin guitarfish.

Annual Recurrence of the Critically Endangered Bowmouth Guitarfish (Rhina ancylostomus) in Djibouti Waters

The bowmouth guitarfish (Rhina ancylostomus) is among the most endangered of marine vertebrates, and evidence of severe declines and localized extinctions has been reported. Yet its life history and ecology suffer from a lack of scientific attention due to the scarcity and unpredictable movements of the species. By collecting opportunistic records from 2015 to 2023 during diving activities, this study describes for the first time the occurrence of a predictable aggregation of R. ancylostomus in the Gulf of Tadjoura (Djibouti). These data provide a key record of this species in the area, whose presence is strongly associated with sandy seabeds and corals at approximately 35 m depth. Based on the opportunistic sightings of R. ancylostomus during diving activity, Ras Eiro and Ras Korali appear to be the currently known core habitats for this species and may serve as breeding or feeding grounds. Overall, our data show that the Gulf of Tadjoura is a globally important conservation hotspot, and therefore its protection should be prioritized.

Comparative analyses of the complete mitochondrial genomes of two southern African endemic guitarfish, Acroteriobatus annulatus and A. blochii

Shark-like rays (order Rhinopristiformes) are among the most threatened cartilaginous fish globally. Despite this, unresolved taxonomic issues still exist within the group. To date, no studies have used complete mitochondrial genomes to assess the phylogenetic placement of Acroteriobatus within the non-monophyletic family Rhinobatidae. The current study reports the first complete mitochondrial genomes for Acroteriobatus annulatus and A. blochii. Similar to other rhinopristiforms, the complete sequences of A. annulatus (16,773 bp) and A. blochii (16,771 bp) were circular molecules with gene organisations identical to that of the typical vertebrate mitogenome. The A + T content was higher than the G + C content, with a bias towards A and C nucleotides observed in all complete mitogenomes. The stem-and-loop secondary structures of the putative origin of light-strand replication were found to have highly conserved synthesis and stem regions, with all substitutions and indels restricted to the loop structure. The ratios of non-synonymous to synonymous substitution rates indicated that purifying selection has been the dominant driver of evolution in rhinopristiform mitogenomes. Phylogenetic reconstructions placed Acroteriobatus as a sister-group to Rhinobatos, confirming its affiliation with the family Rhinobatidae. However, based on its apparent polyphyly with the aforementioned genera, the familial assignment of Pseudobatos is not fully resolved and requires further investigation.

A safe haven for potential reproductive aggregations of the critically endangered Brazilian guitarfish (Pseudobatos horkelii)

Brazilian endemic batoid elasmobranch populations have declined dramatically in the past 40 years due to anthropic activities (e.g., overfishing). The Brazilian guitarfish, Pseudobatos horkelii, included in the IUCN red list of endangered species [Critically Endangered (CR)], has been captured as by-catch by trawling fishing boats to the edge of extinction. Despite governmental conservation initiatives, the species is still caught and commercialized along the Brazilian coast. In this study, the authors report three rare aggregation events for the Brazilian coast of P. horkelii, inside the only nearshore no-entry Brazilian marine protected area. Strategies for its protection are also discussed.

Evaluating artisanal fishing of globally threatened sharks and rays in the Bay of Bengal, Bangladesh

Sharks and rays are at risk of extinction globally. This reflects low resilience to increasing fishing pressure, exacerbated by habitat loss, climate change, increasing value in a trade and inadequate information leading to limited conservation actions. Artisanal fisheries in the Bay of Bengal of Bangladesh contribute to the high levels of global fishing pressure on elasmobranchs. However, it is one of the most data-poor regions of the world, and the diversity, occurrence and conservation needs of elasmobranchs in this region have not been adequately assessed. This study evaluated elasmobranch diversity, species composition, catch and trade within the artisanal fisheries to address this critical knowledge gap. Findings show that elasmobranch diversity in Bangladesh has previously been underestimated. In this study, over 160000 individual elasmobranchs were recorded through landing site monitoring, comprising 88 species (30 sharks and 58 rays) within 20 families and 35 genera. Of these, 54 are globally threatened according to the IUCN Red List of Threatened Species, with ten species listed as Critically Endangered and 22 species listed as Endangered. Almost 98% juvenile catch (69-99% for different species) for large species sand a decline in numbers of large individuals were documented, indicating unsustainable fisheries. Several previously common species were rarely landed, indicating potential population declines. The catch pattern showed seasonality and, in some cases, gear specificity. Overall, Bangladesh was found to be a significant contributor to shark and ray catches and trade in the Bay of Bengal region. Effective monitoring was not observed at the landing sites or processing centres, despite 29 species of elasmobranchs being protected by law, many of which were frequently landed. On this basis, a series of recommendations were provided for improving the conservation status of the elasmobranchs in this region. These include the need for improved taxonomic research, enhanced monitoring of elasmobranch stocks, and the highest protection level for threatened taxa. Alongside political will, enhancing national capacity to manage and rebuild elasmobranch stocks, coordinated regional management measures are essential.

Reproductive Anatomy of Chondrichthyans: Notes on Specimen Handling and Sperm Extraction. I. Rays and Skates

Simple Summary

Many species of rays and skates are endangered, and ex situ conservation programs developed by research centers and public aquaria could improve this situation. To reproduce these species in captivity, scientists need to know how to extract their sperm and how to conduct their artificial insemination; however, the anatomical diversity of the reproductive organs of this group of animals is a handicap. A comparison of the reproductive anatomies of 11 distinct species is presented here, emphasizing the important differences between the species when performing sperm extraction or artificial insemination. In addition, the process of obtaining sperm samples from both live and dead males is described in detail, using both cannulation and abdominal massage.

Abstract

The superorder Batoidea (rays, skates, and relatives), constitutes one of the most threatened group of vertebrates. Strengthening ex situ conservation programs developed in research centers and public aquaria could be a way of addressing this situation. However, captive breeding programs must be improved to prevent the capture of wild animals and to develop proper in situ reintroduction strategies. Sperm extraction and artificial insemination are two techniques commonly used in other threatened species, which could also be used in rays and the like. However, the different reproductive morphologies present within this group of animals may hamper both processes. Here, we present a comparison of the reproductive anatomies of 11 distinct batoid species, emphasizing the important differences between the species when performing sperm extraction or artificial insemination. Both male and female animals, belonging to the Rajidae, Dasyatidae, Torpedinidae and Myliobatidae families, from the Mediterranean Sea were studied. In addition, we describe the procedure to extract sperm using both cannulation and abdominal massage, either from live or dead batoids Finally, the obtention of motile sperm recovered from the oviducal gland of females is described. These techniques generate a new range of possibilities for the conservation of these threatened species.

Angel sharks (Squatinidae): A review of biological knowledge and exploitation

Angel sharks (Squatina spp.) are distributed in warm temperate to tropical waters around the world. Many species occur in shelf seas and exhibit seasonal inshore-offshore migrations, moving inshore to give birth. Consequently, there can be high spatial overlap of angel shark populations with fisheries and other human activities. Their dorso-ventrally flattened body shape, large size (most species attain >100 cm total length, L_T ) and demersal nature means that they may be taken in a variety of demersal fishing gears from birth. Available data indicate that angel sharks typically have a biennial reproductive cycle, with litter sizes generally <20 and the young born at c. 20-30 cm. The biological characteristics of angel sharks render them susceptible to overexploitation, as exemplified by the decline of Squatina squatina from many parts of its former range in the north-east Atlantic and Mediterranean Sea. Currently, half of the 22 recognized extant species of angel shark are classed as Threatened on the International Union for Conservation of Nature (IUCN) Red List (with a further three classified as Data Deficient). Given the biological vulnerability of angel sharks, and that many species are data-limited, the current paper provides a review of available biological information and fisheries data pertaining to this family.

First record of Gorgona guitarfish (Pseudobatos prahli) off the Baja California peninsula with updated key to the guitarfishes of the North Eastern Pacific

The Gorgona guitarfish is a poorly documented ray found in the Eastern Pacific. It can be distinguished from its congeners due to its distinctive coloration and rostral cartilages. Here I document an extensive northern range expansion of almost 2000 km based on a juvenile specimen caught off the Baja California Peninsula. This specimen also represents the smallest documented individual of this species, along with the first quantitative morphometric data reported since the 1995 description. Additionally, an updated key to the guitarfishes of the North Eastern Pacific is included.

Presence of pregnant females of the Gorgona guitarfish, Pseudobatos prahli, in the Mexican tropical Pacific

Five specimens (four females and one male) of the Gorgona guitarfish, Pseudobatos prahli, were sighted during two dives carried out off the western Gulf of Tehuantepec. This document describes the reproductive condition of three adult females captured, two of which had uterine eggs, whereas one had embryos. The sighting and capture of specimens occurred during two Tehuano wind events; the authors, therefore, believe that variations in temperature and dissolved oxygen could have affected P. prahli, leading it to carry out temporal migrations towards coastal shallow waters.

DNA barcodes and ethnomedicinal use of Sharpnose guitarfish Glaucostegus granulatus by the locals at Keylong, Lahaul and Spiti, Himachal Pradesh

Illegal trade of fishes is common and has been in practice since ages for the support of livelihood and as dietary supplements. However, several species are protected in the Wildlife (Protection) Act, 1972 of India and their trade is restricted under CITES. In this article, we report trade of Sharpnose guitarfish (Glaucostegus granulatus) for the ethnomedicinal remedy, identified using DNA barcoding in the Keylong district of Lahaul and Spiti, Himachal Pradesh. This study provides the first DNA barcode of Sharpnose guitarfish. In order to handle wildlife offense cases we emphasize that a large reference database for other fishes in trade is needed.

Population productivity of shovelnose rays: Inferring the potential for recovery

There is recent evidence of widespread declines of shovelnose ray populations (Order Rhinopristiformes) in heavily fished regions. These declines, which are likely driven by high demand for their fins in Asian markets, raises concern about their risk of over-exploitation and extinction. Using life-history theory and incorporating uncertainty into a modified Euler-Lotka model, the maximum intrinsic rates of population increase (r_max) were estimated for nine species from four families of Rhinopristiformes, using four different natural mortality estimators. Estimates of mean r_max, across the different natural mortality methods, varied from 0.03 to 0.59 year^-1 among the nine species, but generally increased with increasing maximum size. Comparing these estimates to r_max values for other species of chondrichthyans, the species Rhynchobatus australiae, Glaucostegus typus, and Glaucostegus cemiculus were relatively productive, while most species from Rhinobatidae and Trygonorrhinidae had relatively low r_max values. If the demand for their high-value products can be addressed then population recovery for some species is likely possible, but will vary depending on the species.

Age and growth of three endemic threatened guitarfishes Pseudobatos horkelii, P. percellens and Zapteryx brevirostris in the western South Atlantic Ocean

The age and growth of three endemic threatened guitarfish species were analysed using vertebrae of Pseudobatos horkelii, P. percellens and Zapteryx brevirostris. Edge and marginal-increment analyses were used to evaluate the periodicity of the formation of the band-pairs, suggesting deposition of one band-pair per year, from late winter to late spring. The von Bertalanffy growth model was used to describe the growth of these species with the following parameters, for pooled sexes: P. horkelii L_∞ = 126.93, k = 0.19 and t₀ = -1.51; P. percellens L_∞ = 109.31, k = 0.16 and t₀ = -1.78; Z. brevirostris L_∞ = 60.37, k = 0.24 and t₀ = -1.42. Our results are essential to understanding the resilience and vulnerability of these species to harvest, which can contribute to management and conservation actions of these species.

Global priorities for conserving the evolutionary history of sharks, rays and chimaeras

In an era of accelerated biodiversity loss and limited conservation resources, systematic prioritization of species and places is essential. In terrestrial vertebrates, evolutionary distinctness has been used to identify species and locations that embody the greatest share of evolutionary history. We estimate evolutionary distinctness for a large marine vertebrate radiation on a dated taxon-complete tree for all 1,192 chondrichthyan fishes (sharks, rays and chimaeras) by augmenting a new 610-species molecular phylogeny using taxonomic constraints. Chondrichthyans are by far the most evolutionarily distinct of all major radiations of jawed vertebrates-the average species embodies 26 million years of unique evolutionary history. With this metric, we identify 21 countries with the highest richness, endemism and evolutionary distinctness of threatened species as targets for conservation prioritization. On average, threatened chondrichthyans are more evolutionarily distinct-further motivating improved conservation, fisheries management and trade regulation to avoid significant pruning of the chondrichthyan tree of life.