Essential waters: Young bull sharks in Fiji's largest riverine system

Rays in the Shadows: Batoid Diversity, Occurrence, and Conservation Status in Fiji

Over recent decades, elasmobranchs (sharks, rays, and skates) have been increasingly recognized among the world's most threatened marine wildlife, leading to heightened scientific attention. However, batoids (rays and skates) are relatively understudied, especially in Large Ocean States of the Pacific. This synthesis compiles insights on batoid diversity and occurrence in Fiji's waters by integrating a literature review, participatory science programs such as the Great Fiji Shark Count (GFSC) Initiative, Projects Abroad Fiji (PA), Manta Project Fiji (MPF), and iNaturalist, along with environmental DNA. Nineteen batoid species from seven families were identified: 19 species from the literature, 12 from participatory science programs, and six from eDNA analysis. Notably, this study provides the first photographic evidence for the bentfin devil ray (Mobula thurstoni, Lloyd, 1908) in Fiji. GFSC data indicated the highest species diversity in the Western Division, with spotted eagle rays (Aetobatus ocellatus, Kuhl, 1823) and maskrays (Neotrygon sp.) being observed most. In-person interviews conducted by PA provided information on the occurrence of wedgefishes and potentially sawfishes. MPF records and iNaturalist uploads were dominated by reef manta rays (M. alfredi, Krefft, 1868), while the pink whipray (Pateobatis fai, Jordan and Seale, 1906) yielded the most DNA sequences. Overall, 68.4% of the species face an elevated extinction risk based on the International Union for the Conservation of Nature Red List criteria. Although caution is warranted with older literature-based records for the giant guitarfish (Glaucostegus typus, Anonymous [Bennett], 1830), giant stingaree (Plesiobatis daviesi, Wallace, 1967), and the lack of sawfish verification, this synthesis highlights the effectiveness of a combined methodological approach in establishing a reference point for the diversity and occurrence of this understudied taxon in Fiji.

A novel intrauterine satellite transmitter to identify parturition in large sharks

Determining where and when animals give birth is critical for establishing effective conservation management that protects vulnerable life stages (e.g., pregnant females and newborns) and places (e.g., nursery grounds). To date, this information has been elusive in the case of highly migratory sharks in the wild. Here, we report on the deployment a of novel intrauterine satellite tag implanted in two highly mobile apex predators, the tiger shark (Galeocerdo cuvier) and the scalloped hammerhead (Sphyrna lewini), that remotely documented the location and timing of birth by a highly migratory oceanic animal in the wild. This novel technology will be especially valuable for the protection of threatened and endangered shark species, where protection of pupping and nursery grounds is a conservation priority.

First photographic evidence of oceanic manta rays (Mobula birostris) at two locations in the Fiji islands

Until the revision of the genus Manta in 2009, when a second manta species (Manta alfredi) was resurrected based on morphological and meristic data, all available records in Fijian literature were recorded as Manta birostris. Subsequently, documented sightings were recorded as M. alfredi. Another reclassification of the genus Manta was undertaken in 2018 when both manta ray species (Manta alfredi, Manta birostris) were moved to Mobula based on phylogenetic analysis. Here, we present the first unequivocal evidence of oceanic manta ray (Mobula birostris) occurrence in Fijian waters. In November 2018, two individuals were sighted foraging in Laucala Bay, a large lagoon adjacent to Suva, the capital city of Fiji. Subsequently, three more individuals were sighted in December 2018, two individuals in July 2020, at least six individuals were observed in November 2021, and eight individuals in May/June 2022, all foraging in the same geographical area. Unique ventral identification patterns could be obtained for nine individuals, and all nine individuals have been re-sighted since first identification, with one individual being documented in 2018, 2020, 2021 and 2022. Two additional individuals were recorded in the Yasawa Island Group in the west of Fiji while passing through and foraging in a channel between Drawaqa and Naviti Island in April and September 2020. We provide photographic identification of ten M. birostris individuals from two sites and discuss our findings in the context of local environmental parameters and other recorded sightings in the South Pacific region. In light of the global extinction risk of M. birostris and the recent reclassification from Vulnerable to Endangered on the Red List of Threatened Species, the expansion of their known distribution range to Fijian waters and the recurrence of individuals over consecutive years in the same location adds valuable information for the development of effective and data-driven conservation strategies.

The role of context in elucidating drivers of animal movement

Despite its consequences for ecological processes and population dynamics, intra-specific variability is frequently overlooked in animal movement studies. Consequently, the necessary resolution to reveal drivers of individual movement decisions is often lost as animal movement data are aggregated to infer average or population patterns. Thus, an empirical understanding of why a given movement pattern occurs remains patchy for many taxa, especially in marine systems. Nonetheless, movement is often rationalized as being driven by basic life history requirements, such as acquiring energy (feeding), reproduction, predator-avoidance, and remaining in suitable environmental conditions. However, these life history requirements are central to every individual within a species and thus do not sufficiently account for the high intra-specific variability in movement behavior and hence fail to fully explain the occurrence of multiple movement strategies within a species. Animal movement appears highly context dependent as, for example, within the same location, the behavior of both resident and migratory individuals is driven by life history requirements, such as feeding or reproduction, however different movement strategies are utilized to fulfill them. A systematic taxa-wide approach that, instead of averaging population patterns, incorporates and utilizes intra-specific variability to enable predictions as to which movement patterns can be expected under a certain context, is needed. Here, we use intra-specific variability in elasmobranchs as a case study to introduce a stepwise approach for studying animal movement drivers that is based on a context-dependence framework. We examine relevant literature to illustrate how this context-focused approach can aid in reliably identifying drivers of a specific movement pattern. Ultimately, incorporating behavioral variability in the study of movement drivers can assist in making predictions about behavioral responses to environmental change, overcoming tagging biases, and establishing more efficient conservation measures.