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Human pressures on marine ecosystems have caused extensive degradation of marine habitats and several local extinctions. Overexploitation and destructive fishing practices are responsible for biodiversity loss in many coastal ecosystems. The definition of conservation programs in marine fish requires comprehensive knowledge on large-scale geographical distribution, while considering distribution/abundance patterns in relation to key environmental variables. Due to their life-cycle traits, the two European seahorses (Hippocampus guttulatus and H. hippocampus), as with other congeneric species, are particularly sensitive to the effects of anthropogenic activities and habitat changes. However, information on the ecological distribution of these two species is scattered, patchy, and mainly focused on small-scale studies. In this paper, we followed an international standard protocol for systematic reviews (the PRISMA protocol) to provide a detailed assessment of the two species’ geographical distribution in relation to the environmental characteristics. According to the 134 analyzed studies, Hippocampus guttulatus is more common in confined areas, while H. hippocampus is found in marine shelf waters. With several interspecific differences, seagrasses were the most used holdfasts of both species. The EUNIS codes (European nature information system) referring to a specific and unique habitat were discussed as a potential tool for defining the ecological distribution of the two species. The obtained results and their future implementation could help plan conservation actions.

Lack of detailed knowledge on ecological niche, life cycles, spatial distribution, reproductive biology and space use strongly affects the selection of useful tools and measures in the conservation of threatened marine species. Especially for sedentary and slow species, behaviour and movement capacities are supposed to be the most important functional traits. Indeed, behavioural variability concerning available space and the close presence of individuals is considered a crucial trait for the population dynamics assessments, especially when disturbances of various causes are present in the environment. The present study aimed to investigate the site fidelity and degree of movement of Hippocampus guttulatus, an emblematic and threatened Mediterranean seahorse species. With this aim, a number of seahorses were tagged and monitored throughout two years within a limited area of the lagoon of Mar Piccolo of Taranto (Southern Italy). The studied individuals were initially morphometrically measured for size, sex and life-cycle stage and subsequently monitored through repeated four-month surveys each year. Obtained results indicated high site fidelity regardless of habitat type. Movement pattern was in line with the data on congeneric species, although values were slightly higher. The analyses showed differences in movement degree among different sexes and life-cycle stages and indicated greater mobility of adult females compared to males and juveniles. The investigated parameters showed a great variability suggesting that even small-scale environmental factors can influence the species mobility. Finally, a change in the population structure has been observed, with the loss of large individuals in 2016 and reduced recruitment in 2017. These findings indicated the possible presence of stressors that could lead to the alteration of the seahorse population at Mar Piccolo of Taranto. [ABSTRACT FROM AUTHOR]

The long-snouted seahorse (Hippocampus guttulatus Cuvier, 1829) is a representative species of the Romanian coast, due to its charismatic appearance and extraordinary biology. Although it is not a commercial fish in Romania, it is subjected to harvesting to be sold as curio or for the aquarium business, and many times is by-caught in trawl or pound net fishery. The current research aimed at the examination of the gut content of wild seahorse specimens, in order to determine the prey preferences of the species along the Romanian Black Sea coast. In the wild, large prey items (Amphipoda, Balanus larvae) were identified as the preferred prey of adult specimens, indicating that size and availability are important factors in prey selection. Adult seahorses appear to prefer larger prey both in wild and controlled environments, as previous research has indicated. [ABSTRACT FROM AUTHOR]

Breeding in captivity for research or exhibition (e.g. in aquaria) can replace the capture of wild specimens of endangered species and allow controlled reinforcement of wild populations. With this aim, diet analysis and establishing the adequate prey are determinant factors for breeding success. However, non-invasive approaches such as faecal DNA analysis are advisable for analysing the diet of these species. Therefore, the aim of the present study was to demonstrate the usefulness of faecal DNA analysis by specific PCR amplification of prey DNA for assessing the diet of the seahorse Hippocampus guttulatus. In a comparison of the suitability of different genes ( COI, 18Sr RNA and 28Sr RNA), 18Sr RNA was found to be the most suitable for designing specific primers for the prey types fed to seahorses ( Artemia, Palaemonetes and Mysidae). The technique was assessed in feeding experiments in which prey ingestion was recorded daily, and faeces were collected for DNA extraction and presence/absence PCR analysis. Amplification of the prey DNA in faeces was consistent with the sequence of prey supplied (prey eaten the day before was always detected). Differences in the time between feeding and detection in faeces suggested prey-specific gut passage times, which were shorter for Palaemonetes than for Mysidae. This fact highlights the importance of feeding trials to avoid overestimating the consumption of prey with long gut retention when PCR-based methods are used. This molecular technique is thus applicable for studying the feeding behaviour of captive seahorses and could be adapted for use in other marine species. [ABSTRACT FROM AUTHOR]

In this study, the spot pattern in Hippocampus guttulatus was analysed using a computer programme algorithm that allowed individual comparison. This methodology was first tested in a controlled environment using 51 adult and 55 juvenile H. guttulatus. Positive matches were obtained in 86·3 and 83·6% of the adults and juveniles, respectively. In a second experiment, monthly surveys were carried out in five selected locations in the Ria Formosa Lagoon, south Portugal, over the course of a year and a total of 980 photographs were analysed. Photographed H. guttulatus were re-sighted one to nine times during the course of the survey period with an overall re-sight record of over 30%. Photo-identification was therefore shown to be a useful tool for non-invasive mark-recapture studies that can be successfully used to survey the population abundance of H. guttulatus aged 6 months or older in consecutive years. This could be of great value when considering the assessment of H. guttulatus populations and understanding changes over time. [ABSTRACT FROM AUTHOR]

Abstract: Knowledge of the biology and ecology of seahorses (Hippocampus spp.) is scarce, but has been increasing in recent years due to their conservation status. Captivity breeding programmes can be a valuable source of information on the reproductive biology of seahorses. A captive broodstock of Hippocampus guttulatus Cuvier 1829 was established in 2006 and kept under natural-like photoperiod and temperature. Female maturation was studied during the whole reproductive season in 2007. Most egg clutches were released from May (17°C; 15L:9D) to October (18°C; 13L:11D), with peak releases occurring in June–August (20°C; 16L:8D–14L:10D). Throughout the study, four egg morphotypes were found; two regression equations were proposed for estimating egg/yolk volume based on measurements of egg and yolk biometrics. Female weight was positively correlated with yolk volume/egg volume ratio (Y v/E v) (r s =0.523, n =21, P <0.05) but not with E v or Y v. Egg dry weight (567±141μg) was correlated with Y v (r s =0.384, n =31, P <0.05). Mean clutch size and clutch biomass were 242±142 eggs and 137±87mg dry weight, respectively. Clutch size was positively correlated to female weight (r s =0.479, n =25, P <0.05). Inter-clutch intervals (days) were affected by temperature (°C) as described by the following equation: Interval =357.55e−0.1283 Temp. Estimated inter-clutch intervals at 16, 18 and 20°C were 45.9, 35.5 and 27.5 days, respectively. Egg total lipids accounted for 31.9±3.1% dry weight. Absolute lipid content in eggs was correlated with egg dry weight (r s =0.907, n =41, P <0.001) and Y v (r s =0.384, n =41, P <0.5). In decreasing order of relative percentage, the most important fatty acids, were 18:1n9, 16:0, 18:2n6, 20:5n3, 18:0 and 22:6n-3. The level of n-3 HUFA was 18.5±0.7% (38.4±3.3mg/g dry weight). The profile of fatty acids in eggs resembled that displayed by the broodstock diet (enriched adult Artemia). [Copyright &y& Elsevier]

Simple Summary: Populations of many marine species are threatened by a number of interacting factors, including anthropogenic activities, climate change, and biodiversity loss. The assessment of the conservation status of such populations relies heavily on several types of data, such as large-scale geographical and ecological distribution. Seahorses are charismatic fish sensitive to environmental pressures, and according to the IUCN directive 95/2020, they should be considered a model for environmental quality assessment. As in many other areas, the data on seahorse ecological distribution in Europe are scattered, patchy, and mainly focused on small-scale studies. Therefore, we undertook a systematic review using the PRISMA protocol to identify the current knowledge status, detect gaps, and propose future research priorities. We analyzed 32 years of published studies and described the distribution of Hippocampus guttulatus and H. hippocampus across 176 sites in the Atlantic Ocean, Mediterranean Sea, and Black Sea as a function of habitat, depth, and degree of confinement. The applied method evidenced the overall lack of a detailed habitat description in published studies. Seahorse conservation would benefit from an analytical description of habitats, such as data on the depth, nature of the substrate, and associated biological communities, as well as the use of a standardized habitat classification system, such as formally recognized EUNIS habitat codes. Human pressures on marine ecosystems have caused extensive degradation of marine habitats and several local extinctions. Overexploitation and destructive fishing practices are responsible for biodiversity loss in many coastal ecosystems. The definition of conservation programs in marine fish requires comprehensive knowledge on large-scale geographical distribution, while considering distribution/abundance patterns in relation to key environmental variables. Due to their life-cycle traits, the two European seahorses (Hippocampus guttulatus and H. hippocampus), as with other congeneric species, are particularly sensitive to the effects of anthropogenic activities and habitat changes. However, information on the ecological distribution of these two species is scattered, patchy, and mainly focused on small-scale studies. In this paper, we followed an international standard protocol for systematic reviews (the PRISMA protocol) to provide a detailed assessment of the two species' geographical distribution in relation to the environmental characteristics. According to the 134 analyzed studies, Hippocampus guttulatus is more common in confined areas, while H. hippocampus is found in marine shelf waters. With several interspecific differences, seagrasses were the most used holdfasts of both species. The EUNIS codes (European nature information system) referring to a specific and unique habitat were discussed as a potential tool for defining the ecological distribution of the two species. The obtained results and their future implementation could help plan conservation actions. [ABSTRACT FROM AUTHOR]

Abstract: Knowledge on seahorses is generally scarce but has been increasing in recent years due to their conservation status. Seahorse culture is a quite recent activity in most countries attempting it, and captive breeding techniques are available only for some species. With the aim of contributing to the development of breeding in captivity for conservative purposes, captive broodstock of the European long-snouted seahorse (Hippocampus guttulatus) was established with 32 wild seahorses captured in Galicia (NW Spain). This study describes the methodologies applied to the maintenance of the broodstocks, with special reference to aquaria design, feeding, growth and breeding. Procedures of seahorse identification (morphologically and genetically) as a tool for broodstock management are also considered. The results achieved during the first year demonstrate a rapid adaptation of wild seahorses to captive conditions. Seahorses were fed exclusively on enriched adult Artemia and displayed high growth rates. However, fatty acid analyses performed on unfertilised eggs of captive broodstock showed a progressive decrease in the content of essential fatty acids (DHA, EPA) with time in captivity, suggesting the need for improvement in the nutritional quality of broodstock feed. [Copyright &y& Elsevier]

Abstract: In recent years, aquaculture development has been based on the use of new tools and technologies from different scientific areas. Animal behaviour can also constitute a useful tool for aquaculture and contribute to the improvement of rearing protocols. In this study, a behavioural approach was developed for the long-snouted seahorse (Hippocampus guttulatus) culture, in order to improve broodstock husbandry and reproduction. The optimisation of laboratory conditions (such as water column depth, holdfast type and availability, animal density, sex ratio and male/female size) was analysed based on seahorse behaviour. Social and reproductive behaviours were studied in terms of space use preferences, activity levels, distribution patterns, mate competition and selection, courtship, male pregnancy and juvenile birth. In captive conditions, seahorses were diurnally active and more isolated during the night. They were mainly located in the water inlet area, near the bottom, and preferred vertical holdfasts and natural plants. H. guttulatus reproduction in captivity was achieved. Seahorse behaviour and reproductive output were affected by the different rearing conditions but not animal welfare. Animal density increased seahorse activity and influenced the number of groups, while holdfast availability affected the group size. Seahorses were generally found in male–female pairs that were not stable over time and tend to select similar size or larger mates. Male competition was rather frequent and was affected by the sex ratio. Courtship occurred during all day and no daily greetings were observed throughout male pregnancy. Water column depth and male competition resulted in mating interruption and juvenile number and size decreased in artificial conditions. Animal behaviour demonstrated to be important for the improvement of seahorse husbandry and reproduction and to constitute a potential tool for aquaculture development. [Copyright &y& Elsevier]