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- A crown for each monarch: a distinguishable pattern using photo-identificationPublication . Correia, Miguel; Antunes, Daniela; Andrade, José Pedro; Palma, JorgePhoto-identification has been proven to be a successful individual recognition tool in seahorse species (e.g., long-snout seahorse Hippocampus reidi (Ginsburg, 1933) and long-snouted seahorse Hippocampus guttulatus (Cuvier, 1829)). Its use was deemed valuable for the assessment of wild populations and to understand variations in abundance over time when capture-recapture methods are needed. In this study, a computer software with a pattern recognition algorithm (I3S® Contour 3.0) was used for individual identification of short-snouted seahorses Hippocampus hippocampus (Linnaeus 1758) in the laboratory. Using this methodology, differences in the shape of each individual’s coronet were tested as a unique and distinguishable characteristic. Two different contours were used as reference and tested to assess the effectiveness of this method in individual identification. A total of 94 captive-bred H. hippocampus, 45 adults (> 1 year old) and 49 young adults (4 months old), were tested. Positive matches were obtained in 55.1 % of the young adults and 84.4 % of the adults using contour 1; and in 77.6 % and 97.8 % for young adults and adults, respectively, using contour 2. All un-matched photos were later successfully matched by visual comparison, using additional traits (e.g., spot patterns) and gender. This methodology yielded very promising results and could be further used in wild individuals to allow population size estimates.
- A synthesis of European seahorse taxonomy, population structure, and habitat use as a basis for assessment, monitoring and conservationPublication . Woodall, Lucy C.; Otero-Ferrer, Francisco; Correia, Miguel; Curtis, Janelle M. R.; Garrick-Maidment, Neil; Shaw, Paul W.; Koldewey, Heather J.Accurate taxonomy, population demography, and habitat descriptors inform species threat assessments and the design of effective conservation measures. Here we combine published studies with new genetic, morphological and habitat data that were collected from seahorse populations located along the European and North African coastlines to help inform management decisions for European seahorses. This study confirms the presence of only two native seahorse species (Hippocampus guttulatus and H. hippocampus) across Europe, with sporadic occurrence of non-native seahorse species in European waters. For the two native species, our findings demonstrate that highly variable morphological characteristics, such as size and presence or number of cirri, are unreliable for distinguishing species. Both species exhibit sex dimorphism with females being significantly larger. Across its range, H. guttulatus were larger and found at higher densities in cooler waters, and individuals in the Black Sea were significantly smaller than in other populations. H. hippocampus were significantly larger in Senegal. Hippocampus guttulatus tends to have higher density populations than H. hippocampus when they occur sympatrically. Although these species are often associated with seagrass beds, data show both species inhabit a wide variety of shallow habitats and use a mixture of holdfasts. We suggest an international mosaic of protected areas focused on multiple habitat types as the first step to successful assessment, monitoring and conservation management of these Data Deficient species.
- Effects of anthropogenic noise as a source of acoustic stress in wild populations of Hippocampus guttulatus in the Ria Formosa, south PortugalPublication . Palma, Jorge; Magalhães, Marisa Gonçalves; Correia, Miguel; Andrade, José PedroThis study evaluated the effects of underwater noise as a source of acoustic stress in the wild populations of Hippocampus guttulatus in the Ria Formosa, south Portugal. Two different scenarios of underwater noise were tested: transient motor boat sound (63.4-127.6 dB) and constant sound produced by the motor of the boat directly above the animals (up to 137.1 dB). Observations were obtained in the wild between 4 and 10 m depth throughout a 3 min period, using a video camera and a hydrophone set, and compared with a control sample. A significant increase (P < 0.05) in the respiratory rate was observed in 87% of the observed fish. Opercular movements per minute (OMPM) increased from 35.7 +/- 10 (control sample) to 41.2 +/- 15.5 after the first minute, to 45.5 +/- 13.3 after the second (both under transient sound) and to 49.7 +/- 12.5 after the third (under constant sound exposure). Differences in means between the control fish and fish observed during the second (P < 0.01) and third minute of observation (P < 0.0001) were significant. Concordantly, a significant increase (P < 0.05) in the OMPM of fish observed in the first minute and the third minute was noted. In addition to the OMPM increase, 37.5% of the animals abandoned the observation location presumably in an attempt to avoid the negative sound stimuli. The noise caused by boat traffic generated an immediate physiological response, expressed as an increase in OMPM, and a behavioural response resulting in site abandonment, which together can be considered as a negative impact on the seahorse populations. This work contributes to an increasing number of studies that have shown that boat traffic can induce ecological and environmental consequences to aquatic species. Future research should evaluate how navigation exclusion areas could have a positive impact on the seahorse populations inhabiting shallow coastal areas.
- Trends in seahorse abundance in the Ria Formosa, South Portugal: recent scenario and future prospectsPublication . Correia, Miguel José Teodoro; Andrade, José Pedro; Koldewey, HeatherIn the last decade, seahorse population census in the Ria Formosa identified stable populations of Hippocampus guttulatus and H. hippocampus at the highest densities described for these species worldwide. However, recent studies in the Ria reported a significant decrease in seahorse numbers of 94% for H. guttulatus and 73% for H. hippocampus. Therefore, this study aimed to identify aspects responsible for the variation in seahorse abundance, first by looking at the current trend of seahorse population by comparing it with previous surveys. Secondly, new techniques were tested to improve the survey efficiency of seahorse population and new tools were developed to promote seahorse population recovery, with potential application in seahorse population management programs. In this study, it was observed that both seahorse species abundance increased since the previous survey (2008/2009) although at lower numbers than in the 2001/2002 surveys and a significant correlation between the percentage coverage and H. guttulatus density was found. The new underwater visual census tested, proved to be more effective and accurate in a low seahorse density scenario. In this study, seasonal variations in seahorse density were observed in all sites and were probably related to human activities, natural events, and holdfast availability. In addition, a new photo-identification method was tested and results indicate it as a suitable tool for capture-recapture studies and less invasive that other commonly used methods. To cope with habitat degradation, artificial holdfast units (AHU) were designed and first tested in laboratory to assess seahorse preference. The preferred AHU was then deployed in 4 locations in the Ria Formosa, that differed in depth, water current and seahorse abundance in the vicinities of the selected site. Results showed seahorse settlement at high densities and validated the usefulness of the AHU as a habitat recovery tool.
- Successful use of geochemical tools to trace the geographic origin of Long-Snouted Seahorse Hippocampus guttulatus raised in captivityPublication . Cabral, Ana Elisa; Ricardo, Fernando; Patinha, Carla; Silva, Eduardo Ferreira da; Correia, Miguel; Palma, Jorge; Planas, Miquel; Calado, RicardoThe global market of dried seahorses mainly supplies Traditional Chinese Medicine and still relies on blurry trade chains that often cover less sustainable practices targeting these pricey and endangered fish. As such, reliable tools that allow the enforcement of traceability, namely to confirm the geographic origin of traded seahorses, are urgently needed. The present study evaluated the use of elemental fingerprints (EF) in the bony structures of long-snouted seahorses Hippocampus guttulatus raised in captivity in two different locations (southern Portugal and Northern Spain) to discriminate their geographic origin. The EF of different body parts of H. guttulatus were also evaluated as potential proxies for the EF of the whole body, in order to allow the analysis of damaged specimens and avoid the use of whole specimens for analysis. The contrasting EF of H. guttulatus raised in the two locations allowed their reliable discrimination. Although no single body part exactly mimicked the EF of the whole body, seahorse trunks, as well as damaged specimens, could still be correctly allocated to their geographic origin. This promising forensic approach to discriminate the geographic origin of seahorses raised in captivity should now be validated for wild conspecifics originating from different locations, as well as for other species within genus Hippocampus.
- Field studies of seahorse population density, structure and habitat use in a semi-closed north-eastern Mediterranean marine area (Stratoni, north Aegean Sea)Publication . Correia, Miguel; Paulo, Diogo; Samara, Elina; Koulouri, Panayota; Mentogiannis, Vasilis; Dounas, CostasThe present study was carried out in the marine area of Stratoni, Greece, where two seahorse species are present (Hippocampus hippocampus and H. guttulatus). Two surveys were conducted (September 2016, May 2019) to gather information regarding seahorse species’ abundance, distribution and habitat characteristics. Four different seahorse natural and artificial habitat types were identified. Results revealed that the abundance of H. hippocampus was relatively high, especially at sites with artificial structures, while the presence of H. guttulatus was rare. Data collected can provide baseline information for future population assessments.
- The paradox of retained genetic diversity of Hippocampus guttulatus in the face of demographic declinePublication . Stacy, Rupert; Palma, Jorge; Correia, Miguel; Wilson, Anthony B.; Andrade, Jose; Castilho, RitaGenetic diversity is the raw foundation for evolutionary potential. When genetic diversity is significantly reduced, the risk of extinction is heightened considerably. The long-snouted seahorse (Hippocampus guttulatus) is one of two seahorse species occurring in the North-East Atlantic. The population living in the Ria Formosa (South Portugal) declined dramatically between 2001 and 2008, prompting fears of greatly reduced genetic diversity and reduced effective population size, hallmarks of a genetic bottleneck. This study tests these hypotheses using samples from eight microsatellite loci taken from 2001 and 2013, on either side of the 2008 decline. The data suggest that the population has not lost its genetic diversity, and a genetic bottleneck was not detectable. However, overall relatedness increased between 2001 to 2013, leading to questions of future inbreeding. The effective population size has seemingly increased close to the threshold necessary for the population to retain its evolutionary potential, but whether these results have been affected by sample size is not clear. Several explanations are discussed for these unexpected results, such as gene flow, local decline due to dispersal to other areas of the Ria Formosa, and the potential that the duration of the demographic decline too short to record changes in the genetic diversity. Given the results presented here and recent evidence of a second population decline, the precise estimation of both gene flow and effective population size via more extensive genetic screening will be critical to effective population management.