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- From settlers to subspecies: genetic differentiation in Commerson’s dolphins between South America and the Kerguelen IslandsPublication . Kraft, Sebastian; Pérez-Alvarez, MJosé; Olavarría, Carlos; Moraga, Rodrigo; Baker, C. Scott; Steel, Debbie; Tixier, Paul; Guinet, Christophe; Viricel, Amelia; Brickle, Paul; Costa, Marina; Crespo, Enrique; Durante, Cristian; Loizaga, Rocio; Poulin, ElieCommerson’s dolphins (Cephalorhynchus commersonii) are separated into the subspecies C. c. commersonii, found along southern South America (SA) and the Falkland Islands/Islas Malvinas (FI/IM), and C. c. kerguelenensis, restricted to the subantarctic Kerguelen Islands (KI). Following the dispersal model proposed for the genus, the latter is thought to have originated from SA after a long-distance dispersal event. To evaluate this biogeographic scenario, a distribution-wide, balanced sampling of mitochondrial DNA (mtDNA) control region sequences was designed. New tissue samples from southern Chile, Argentina, FI/IM, and KI were added to published sequences from SA and KI, for a total of 256 samples. Genetic diversity indices, genetic and phylogeographic structure, and migration rates were calculated. One haplotype was shared between subspecies, with which all haplotypes of C. c. kerguelenensis formed a distinct group in the haplotype network. A new haplotype for C. c. kerguelenensis is reported. Differentiation in haplotype frequencies was found among localities within the distribution of C. c. commersonii, yet the phylogeographic signal was only statistically significant between subspecies. Coalescent-based historical gene flow estimations indicated migration between the northern and southern portions of the species’ range in SA as well as between SA and the FI/IM, but not between these and the KI. The net nucleotide divergence between dolphins from SA and the FI/IM was lower than the recommended threshold value suggested for delimiting subspecies, unlike that found between C. c. commersonii and C. c. kerguelenensis. The results are consistent with the model of post-glacial colonization of KI by South American C. commersonii, followed by an ongoing divergence process and subspecies status. Thus, C. c. kerguelenensis may represent the most recent diversification step of Cephalorhynchus, where isolation from their source population is driving a process of incipient speciation.
- Residency and space use estimation methods based on passive acoustic telemetry dataPublication . Kraft, Sebastian; Gandra, Miguel; Lennox, R. J.; Mourier, J.; Winkler, Alexander; Abecasis, DavidAcoustic telemetry has helped overcome many of the challenges faced when studying the movement ecology of aquatic species, allowing to obtain unprecedented amounts of data. This has made it into one of the most widely used methods nowadays. Many ways to analyse acoustic telemetry data have been made available and deciding on how to analyse the data requires considering the type of research objectives, relevant properties of the data (e.g., resolution, study design, equipment), habits of the study species, researcher experience, among others. To ease this decision process, here we showcase (1) some of the methods used to estimate pseudo-positions and positions from raw acoustic telemetry data, (2) methods to estimate residency and (3) methods to estimate two-dimensional home and occurrence range using geometric or hull-based methods and density-distribution methods, a network-based approach, and three-dimensional methods. We provide examples of some of these were tested using a sample of real data. With this we intend to provide the necessary background for the selection of the method(s) that better fit specific research objectives when using acoustic telemetry.
- Small coastal marine protected areas offer recurring, seasonal protection to the common stingray (Dasyatis pastinaca)Publication . Kraft, Sebastian; Winkler, Alexander; Abecasis, DavidMarine protected areas (MPAs) are a crucial tool in safeguarding marine biodiversity. However, elasmobranchs are often not the primary protection target of MPAs, and their contribution to protect these species remains to be better understood. In this study we examine the movement patterns of common stingrays in the Professor Luiz Saldanha marine park, a Portuguese temperate coastal MPA. Using acoustic telemetry, we tagged 31 common stingrays and analyzed their spatial and temporal distribution within the MPA and adjacent areas using a long-term data set. Our findings indicate that this species exhibits seasonal site fidelity, with greater presence during the colder months and reduced presence during warmer months. Space use areas did not exceed the size of the fully protected area, and nocturnal and crepuscular activity was significantly higher than during daytime. Additionally, we observed that most individuals seasonally migrated between this MPA and the nearby Sado estuary, likely to reproduce in the latter. These results demonstrate the site fidelity of common stingrays to an area within the marine park, however the protection provided is only seasonal. Seasonal protection of the movement corridor between the marine park and the estuary would improve the management of this species.
- Genetic analysis as a tool to improve the monitoring of stranded cetaceans in ChilePublication . Kraft, Sebastian; Rodríguez, Francisca; Olavarría, Carlos; Poulin, Elie; Pérez-Álvarez, María JoséCetacean strandings are regularly recorded along the coast of Chile. However, crucial information such as species and sex of the individuals involved in these events can often be difficult to assess. In this context, the use of molecular tools as a complementary method can improve a stranding database, particularly by correcting misidentifications and providing new data for unidentified samples. This new information is especially important in the case of species that are poorly known or of high conservation interest. In this study, we evaluate how molecular tools can support and complement the field work records of strandings in Chile by identifying, corroborating, or correcting the identification of the species and sex of the recorded individuals. We obtained samples through a collaboration with the government agency that is in charge of assisting with cetacean strandings and collected the relevant information. Multidisciplinary approaches like this, and inter-institutional collaborations, can improve the study of cetacean strandings and the decisions in management and conservation policies around them. Cetacean strandings are a valuable source of information for several studies from species richness to conservation and management. During the examination of strandings, taxonomic and sex identification might be hindered for several reasons. Molecular techniques are valuable tools to obtain that missing information. This study evaluates how gene fragment amplification protocols can support the records of strandings done in the field in Chile by identifying, corroborating, or correcting the identification of the species and sex of the recorded individuals. Through a collaboration between a scientific laboratory and government institution in Chile, 63 samples were analyzed. Thirty-nine samples were successfully identified to the species level. In total, 17 species of six families were detected, including six species of conservation interest. Of the 39 samples, 29 corresponded to corroborations of field identifications. Seven corresponded to unidentified samples and three to corrected misidentifications, adding up to 28% of the identified samples. Sex was successfully identified for 58 of the 63 individuals. Twenty were corroborations, 34 were previously unidentified, and four were corrections. Applying this method improves the stranding database of Chile and provides new data for future management and conservation tasks.
- Redescription of the Chilean angel shark Squatina armata (Philippi, 1887) (Squatiniformes, Squatinidae)Publication . Kraft, Sebastian; Fernández-Cisternas, Ítalo; Araya, Miguel; Concha, Francisco J.Angel sharks ( Squatina spp. Dum & eacute;ril, 1805) are a group of coastal benthic sharks distributed worldwide, currently including threatened and understudied species. Two species are formally described along the East Pacific coast, the California angel shark S. californica Ayres, 1859 and the Chilean angel shark S. armata (Philippi, 1887). The latter species occurs in the southeastern Pacific and has historically been understudied. Additionally, the original description of S. armata lacks sufficient data to confidently identify individuals of this species compared to modern descriptions, and no type specimen is currently available to ensure specimen identification. Detailed morphological descriptions for identifying species are an essential resource for solving taxonomic issues in groups of morphologically similar species and to promote the conservation of critically endangered species. Therefore, a neotype from the type locality is here designated for S. armata , and a detailed and standardized morphological characterization based on modern taxonomic works is provided. This work contributes in improving the knowledge on the Chilean angel shark taxonomy and provides an improved frame of reference for identifying angel sharks in the East Pacific, especially in areas where species may occur in sympatry.
- Tagging mortality in acoustic telemetry studies: insights from a multispecies analysisPublication . Martínez Ramírez, Lucas; Bentes, Luis; Dias Almeida Cardoso, André Filipe; Erzini, Karim; Gandra, Miguel; Kraft, Sebastian; Winkler, Alexander; Abecasis, DavidThe widespread adoption of acoustic telemetry has transformed our understanding of marine species' behavior and movement ecology. However, accurately interpreting telemetry data, especially concerning tagging mortality, is essential for drawing valid conclusions. In this study, we scrutinized tagging mortality in 223 individuals across 14 species and evaluated the impact of tagging methodologies, including capture method and size effects. Results reveal high tagging survival rates overall, attributable to the resiliency of the studied species and the rigorous animal welfare protocols followed during tagging procedures. Our results highlight the importance of tailoring array designs to the specific mobility patterns of the studied species for accurate survival assessments. This research contributes to generalizing mortality assessments and clearing the path for more precise and reliable telemetry studies in the future.
- Horizontal and vertical movements of the critically endangered Rostroraja alba in a coastal marine protected areaPublication . Kraft, Sebastian; Winkler, Alexander; Abecasis, DavidElasmobranchs are slow-growing marine predators whose populations have declined due to their susceptibility to overfishing, especially affecting species of large size. Rostroraja alba is a large skate that is currently classified as critically endangered. 2. To address the effects of overfishing and promote the recovery of marine species and habitats, marine protected areas (MPAs) are a commonly implemented management strategy. A critical aspect of their success is using information on species' movement patterns; however, this is frequently not assessed for elasmobranchs. 3. In this study, acoustic telemetry was used to monitor 30 R. alba in the Professor Lu & iacute;s Saldanha Marine Park (Portugal) to assess their long-term movements in the context of a coastal MPA and to evaluate the contribution of this kind of spatial management to the conservation of this species. 4. Immature individuals were more frequently captured than adults, which postulates this area as a potential nursery. The average residency was moderate and relatively consistent throughout the year, as was area use. No marked size or sex-based differences in movement were noted. Individuals were more active and occurred in shallower waters at night and twilight, and occasional quick vertical movements into the water column, isolated or in sequence, were also noted. 5. In general, the LSMP seems to offer stable protection to immature R. alba, with no strong seasonal variation. These results provide relevant input for adaptive management measures of this and other similar MPAs and highlight the contribution of these efforts to the protection of nursery areas.
- Seasonal movement dynamics of the commercially important thornback ray (Raja clavata) in a coastal marine protected areaPublication . Kraft, Sebastian; Winkler, Alexander; Abecasis, DavidElasmobranchs are a group of slow growing species whose populations are in decline mostly due to their susceptibility to overfishing. A common approach to protect marine species is to establish marine protected areas (MPAs). Data on the spatial ecology of species is key information for MPA implementation and management. However, this information is usually lacking, particularly for elasmobranchs. In this study, thornback rays were tagged with acoustic transmitters to track their movement patterns in a marine protected area in Portugal. Individuals were detected for up to 1323 days, and transient and resident behaviours were observed. Residents exhibited a seasonal pattern of presence, peaking during late winter and spring. Weekly occurrence range size reached its maximum from mid-summer to mid-autumn. Diel changes in movement, mainly as increases in activity, were detected during night and twilight. These findings highlight the seasonal and daily dynamics of thornback rays and how these can influence their protection in an MPA. The area where the LSMP is established appears to be dominated by males, indicating that most of the protection provided to this species is towards this sex. These results provide valuable insights for the conservation and adaptive management of this commercially relevant species.
- Fully protected marine areas linked to reduced home ranges of fishesPublication . Ohayon, Sarah; Abecasis, David; Almeida, Pedro R.; Alós, Josep; Aspillaga, Eneko; Belo, Ana Filipa; Costa, José Lino; Di Franco, Antonio; Di Lorenzo, Manfredi; Ferguson, Adrian; Guidetti, Paolo; Kraft, Sebastian; La Mesa, Gabriele; Olsen, Esben Moland; Parsons, Darren; Pickholtz, Renanel; Quintella, Bernardo R.; Silva, Ana Filipa; Taylor, Brett M.; Villegas‐Ríos, David; Belmaker, JonathanHome range size is a fundamental trait that can affect the probability of fish being harvested and, at the same time, may be affected by fishing. The relationship between home range size and fishing will impact the effectiveness of fully protected areas (FPAs), as it will influence the number of fish moving into fished areas, affecting both spillover and edge effects. One hypothesis is that individuals within FPAs will present reduced home range size relative to individuals in fished areas. This pattern can be driven by demographic selection (e.g. fishing of individuals with large home ranges leaving the FPAs), improved habitat requiring less foraging movements, or behavioural changes associated with reduced fishing threats. To test the relationship between home range size and protection, we compiled 1143 individual-level home range sizes based on acoustic tracking, covering 17 species from 11 FPAs in 7 countries, with information on distance from FPA borders. A dichotomic analysis (in/out of FPAs) did not support a significant change in the home range size between FPAs and fished areas. However, continuous analysis across the FPA borders demonstrated reduced home range size within the FPAs. We did not find an effect of FPA age or size on this pattern. While we cannot pinpoint the underlying mechanism for the pattern revealed, we suggest behavioural changes as the main driver for reduced home range within FPAs. This mechanism will lead to more resident populations within FPAs, reducing fishing mortality within FPAs yet limiting spillover benefits to adjacent fisheries.
- Long-term co-occurrence and gregariousness in the migratory common stingray using network analysisPublication . Kraft, Sebastian; Winkler, Alexander; Abecasis, David; Mourier, J.Aggregations and social interactions play an important role in the movement ecology of many animals, including elasmobranchs. Several of these species have shown the capability of carrying out complex social behaviours, and the importance of sociality in this taxon is being realized. Although it is a growing field of study in the case of these organisms, these processes still need to be better understood, especially to support management and conservation policies. In this study, a long-term acoustic telemetry data set collected on Dasyatis pastinaca in a coastal marine protected area was analysed. A co-occurrence network analysis was done to investigate preferential associations among individuals, revealing non-random associations among them. The analysis revealed a few strong and consistent associations that were maintained across inter-migratory periods, as this species performs seasonal migrations to a nearby estuary, suggesting temporal stability of the observed associations. Moreover, individuals had similar average positions and a generally high overlap of space use in both periods, indicating some level of site fidelity to the fully protected area. Groups of up to 64% of tagged individuals were co-detected at a same receiver, particularly in the western side of the array. Despite our limited sample size, likely underestimating associations, these results show that in addition to their large-scale movement pattern, D. pastinaca is likely to also present active partner preference and spatial structure at a finer spatial scale. The nature of such results is relevant to support the protection of these species.