Captive breeding and early development of tank-reared lyretail anthias Pseudanthias squamipinnis (Peters, 1855): Assessments of hatching success, larval survival, and ontogeny

Driven by wildlife conservation and economic demands, captive breeding has expanded globally, intensifying wildlife-human interactions. In specialty animal breeding, particularly for species with short domestication histories and underdeveloped breeding protocols, clinically important antibiotics are commonly misused, posing potential ecological and health risks that remain largely unexplored. We collected fecal samples from three groups of musk deer (Moschus berezovskii): those exposed to clinically important antibiotics, those not exposed for six months, and wild musk deer, and analyzed their microbiomes and resistomes using metagenomic and culture-based methods. We found that captivity significantly expanded and reshaped the fecal resistome of musk deer. The antibiotic-exposed musk deer harbored a significantly higher diversity and abundance of antibiotic resistance genes (ARGs) compared to those non-exposed to antibiotics and wild deer. We observed a higher abundance of clinically important ARGs within Enterobacteriaceae in fecal samples of captive musk deer. This observation was further supported by the antibiotic susceptibility profiles of 124 Escherichia coli strains isolated from antibiotic-exposed musk deer. Seven identical mobile genetic element-associated ARGs were detected in distinct bacterial hosts across fecal samples from musk deer and farm workers, indicating potential conjugative transfer between the two groups. Our results suggest that captive breeding of specialty animals is an overlooked but significant reservoir for disseminating clinically important ARGs, and underscore the transmission risk at the animal-human interface.

The global decline in wild populations and the growing demand for bioresources have spurred efforts to enhance wildlife populations through captive breeding programmes. However, the success of these initiatives remains limited. Using data from a long-term captive breeding programme conducted by a national salmon hatchery in Japan, I examined the influence of an individual's origin on mortality in captivity. My results showed that wild individuals had higher mortality rates in captivity than captive-bred individuals. These findings suggest that efforts to enhance wildlife populations through captive breeding can result in the loss of wild individuals with high fitness in the wild and the ability to enhance their offspring's fitness in the wild, underscoring the need for approaches that lower the mortality of wild individuals in captivity.

Surrogate broodstock development offers a practical route to reproduce species that resist captive breeding, shorten generation time, and conserve valuable genetic resources. We review current methods for isolation and enrichment of primordial germ cells and gonial cells, recipient sterilization options, transplantation routes and stages, cryopreservation practices, and the role of genome editing to create optimized hosts. Evidence from salmonids, cyprinids, and marine teleosts shows that donor germ cells retain genetic identity while the recipient gonadal environment determines gamete type, but recipient germline status, donor cell dose, and phylogenetic distance jointly set the proportion of donor-derived progeny. Sterile recipients such as triploids or dead-end knockouts produce near-exclusive donor output, whereas fertile recipients yield mixed cohorts unless donor dominance is enforced by high cell dose or host ablation. Practical applications span restoration of endangered stocks, rapid dissemination of elite germplasm, reduced broodstock cost, and accelerated trait validation through edited germline cells. Remaining challenges include variable colonization efficiency in distant xenotransplants, cryo viability for oogonia, regulatory and ethical constraints, and the need for routine parentage verification and welfare safeguards. We conclude with recommended best practice elements for applied programs and priorities for research to broaden species coverage, improve efficiency, and ensure responsible deployment of surrogate broodstock for conservation and commercial aquaculture.

ABSTRACT Amidst the global biodiversity crisis, conserving endangered species like musk deer ( Moschus spp.) is crucial. China holds the highest musk deer diversity worldwide, with abundant populations, wide distribution, and significant musk production. We reviewed the morphology, population trends, distribution, conservation status, captive breeding, and related challenges of musk deer to inform targeted conservation strategies. Currently, wild musk deer populations are primarily distributed in western, central, and northeastern regions of China. Over the past seven decades, illegal hunting and habitat fragmentation have caused severe population declines, reducing most populations by over 97% since the 1950s. To alleviate pressure on wild populations and promote sustainable resource use, China initiated captive breeding of musk deer in 1958, resulting in a 5.6‐fold increase in captive musk deer from the 1990s to the 2020s. However, challenges like serious diseases hinder further expansion of artificial musk production. Given the limitations of both in situ and ex situ conservation, it is advised to establish or optimize natural reserves in musk deer habitat. Strengthening law enforcement, population monitoring, ecological research, captive breeding, reintroduction, and public awareness is essential for global musk deer conservation.

This case report explains the cause of death of a roloway monkey (Cercopithecus roloway), a critically endangered primate native to the Upper Guinea forests of West Africa, that was kept for captive breeding and conservation at the Accra Zoological Garden′s primate breeding center in Ghana. Sweetpea, a “15‐year‐old” female Roloway monkey, was found dead on September 21, 2018, without prior signs of illness. Gross and histopathological findings revealed acute fibrinous pneumonia, septicemia, and myocardial necrosis, while bacterial culture of lung tissue and thoracic fluid yielded β‐hemolytic Streptococcus spp., implicating it as the likely cause of death. Whereas species‐level identification was not performed due to resource limitations, isolation of this species in pure culture supports its implication in this case, leaning on the published knowledge of its primary role in bacterial septicemia and pneumonia and other soft tissue infections in monkeys, even in captivity. Roloway monkeys (Cercopithecus roloway) are critically endangered primates native to the Upper Guinea forests of West Africa. This report describes the sudden death of a 15‐year‐old female at the Accra Zoological Garden and the subsequent diagnostic investigation, which revealed β‐hemolytic Streptococcus spp. as the causative agent of acute pneumonia and septicemia. This case underscores the need for structured health monitoring in captive breeding programs and highlights veterinary and husbandry measures crucial to conservation efforts. Additionally, a uterine leiomyosarcoma was detected, which may explain Sweetpea′s failure to reproduce despite long‐term pairing. This case highlights the importance of surveillance for beta‐hemolytic streptococci in captive monkeys, more so the endangered species.

Initial studies on captive breeding of Chromis limbaughi: Paving the way for its conservation and sustainable production

First report on the use of various fishing gears and transport schemes for the captive breeding of shortfin scad (Decapterus macrosoma) as a potential species for aquaculture

The mudminnow ( Umbra krameri ) has its westernmost distribution area in Austria near Vienna (Wanzenböck 1995, for historical and current distribution maps see the Power Point presentation in the Suppl. material 1). The species is considered the most threatened fish species in Austria and was believed to be extinct in the second half of the 20th century (Böhm 1978, Hacker 1983, Herzig-Straschil 1994). In 1992 it was rediscovered in the Fadenbach, a backwater system within the Danube Floodplain National Park and shortly thereafter in a wetland south of Vienna (Jesuitenbach) (Wanzenböck and Spindler 1995, Spindler and Wanzenböck 1995). Over the past four decades, several conservation measures have been implemented in the National Park in order to protect the mudminnow, including studies on habitat preferences (Sehr and Keckeis 2017), monitoring programs (Jung et al. 2018, Jung et al. 2024), habitat restoration projects (Spindler 2006) and captive breeding efforts. Furthermore, a reintroduction attempt was carried out in the Hanság wetland, a drainage-ditch system on the Austrian-Hungarian border. Captive bred mudminnows, whose parental generation originated from the Fadenbach population, were stocked there (Benesch 2004, Benesch 2008). The Fadenbach-population was the only one that had been regularly monitored over the past decades starting immediately after its discovery. During the 1990s, mudminnow densities were relatively high, but showed large fluctuations most likely due to high winter mortality (Fig. 1). In 2013 even higher densities were recorded and the population appeared to have extended its range within the Fadenbach system (Keckeis and Sehr 2014), most likely due to the creation of so called “survival ponds” – deeper sections within the backwater system. Between 2018 and 2023 severe droughts led to a dramatic decline. Currently, the population remains at a very low level and the species has disappeared from the upper reaches of the Fadenbach system. The recent droughts and persistently low water levels are part of a long-term trend: in the area, mean groundwater levels have dropped by approximately 1.5 metres since 1940 (Fig. 2) mainly due to river regulation (diking), agricultural irrigation, incision of the Danube river bed and a decline in precipitation. Therefore, a new conservation initiative was launched by the Danube Floodplain National Park with the project “PonDiversity” which focuses on the European pond turtle ( Emys orbicularis ), water pineapple ( Stratiotes aloides ) and mudminnow. The project includes comprehensive surveys of the mudminnow habitats within the National Park using electrofishing, an assessment of existing captive stocks established in the 1990s and genetic analysis of both, wild and captive populations. In a second phase, habitat restoration measures and improved captive breeding programmes will be implemented based on the outcome of population genetic studies. The reintroduced population in the Hanság area survived for around 15 years - at least until 2018 - but was no longer detected in 2023 (Jung et al. 2024). Its current status must be regarded as uncertain, as no extensive surveys have been carried out so far. In contrast to the Fadenbach- and Hanság-populations, the Jesuitenbach-population has recently shown a significant increase with highest densities recorded in 2024 (Jung et al. 2025). A possible explanation for this development is the decline of roach and pike populations during the recent dry periods, which may have led to reduced competition and predation pressure without deteriorating habitat conditions for the mudminnow. The population increase provided an opportunity to establish an ex situ population of Jesuitenbach mudminnows at Zoo Schönbrunn.

The European Mudminnow ( Umbra krameri )—a species adapted to slow-flowing, oxygen-poor backwaters and marshes with dense vegetation—was declared extinct in Austria in 1975. However, it has since been rediscovered at two isolated sites: Fadenbach in the Nationalpark Donau-Auen and Jesuitenbach. Captive breeding programs have since been initiated to support reintroduction and safeguard remaining genetic diversity. To inform conservation strategies, we assessed genetic diversity, structure, and effective population sizes (Ne) using polymorphic microsatellite markers. Preliminary results reveal significant genetic differentiation between the two wild populations and between captive stocks and their presumed source in Fadenbach. Overall genetic diversity is low, and Ne estimates suggest a high risk of inbreeding, genetic drift, and further loss of adaptive potential. Although sample sizes are limited, these findings point to critical conservation concerns, especially for the Fadenbach population. Importantly, this study emphasizes the utility of genetic monitoring as a central tool for evidence-based conservation planning—supporting adaptive management, preventing further genetic erosion, and promoting the long-term survival of this critically endangered species in Austria and beyond.

The European weatherfish Misgurnus fossilis , once widespread across Eurasia, is now critically endangered in Flanders (Belgium), prompting the establishment of a captive breeding programme as part of conservation efforts. During rearing, juvenile weatherfish suffered heavy infections from the ectoparasitic flatworm Gyrodactylus fossilis , leading to mortality events. Although G. fossilis is a natural parasite of M. fossilis , high host densities in hatchery conditions facilitated pathological infection intensities, while adult fish maintained at lower densities showed no visible pathology. This suggests that husbandry practices strongly modulate dynamics of this host–parasite system in captivity. To place these observations in a historical context, we screened both captive-bred fish and archival material (1881–1973, i.e. prior to the anthropogenic introduction of Asian congeners in Misgurnus ) for ectoparasites. Morphological and molecular characterisation revealed infections of three monopisthocotylan flatworms: G. fossilis, Gyrodactylus misgurni (Gyrodactylidae), and Actinocleidus cruciatus (Dactylogyridae). All represent new records for Belgium, with G. misgurni and A. cruciatus considered native due to their occurrence in historical material. Notably, these parasites’ abundance has declined compared to historical collections, raising concerns about their own conservation status. Since parasites contribute substantially to species-richness, ecosystem functioning, and even the health of their host individuals and populations (e.g., their immunological development and resilience) their co-decline alongside endangered hosts represents a hidden and meaningful dimension of biodiversity loss. Our findings highlight both risks and opportunities associated with parasite conservation in ex situ programmes focused on fishes or other vertebrate hosts. High juvenile stocking densities increased parasite burdens and mortality, while improved husbandry practices allowed stable co-existence of host and parasite populations. This indicates that carefully managed captive breeding facilities may act as refugia not only for M. fossilis but also for its specialist parasites, maintaining ecological interactions and genetic diversity that would otherwise be lost. While parasites are often overlooked or actively eliminated in wildlife management, they play essential roles in ecosystems and represent species of conservation concern in their own right. These results emphasise the possibility of including parasites in conservation planning. For the weatherfish and its parasites, ex situ conservation thus provides an experimental framework for developing integrated strategies that safeguard both host and parasite persistence. Future reintroduction initiatives should therefore consider whether to also re-establish native parasite populations, a decision that requires informed discussion among conservation stakeholders. By demonstrating the feasibility of host–parasite co-conservation, this study advances the idea that conservation programmes can optimise resource allocation while preserving the evolutionary and ecological relationships of multiple species simultaneously. This research was funded by an International Coordination Action grant of the Research Foundation – Flanders (G0ADU24N), by the AfroWetMaP project of the Belgian Federal Science Policy Office (4255-FED-tWIN-G3 program, Prf-2022-049) and by the European Life-program (Life-B4B). We gratefully acknowledge the support of Olivier Pauwels, curator of the vertebrate collections at the Royal Belgian Institute of Natural Sciences.

Since 2011, our team has been engaged in the conservation biology of the European mudminnow ( Umbra krameri ), focusing on both ex-situ and in-situ methods. Our work includes (captive) breeding, egg incubation, and larval and juvenile rearing under controlled conditions and in natural habitats. Induced reproduction has been attempted in closed systems through the application of various hormonal treatments; however, these efforts have not resulted in success. In contrast, controlled natural reproduction has proven effective for producing offspring. An innovative spawning cage has been developed. This device facilitates the natural spawning of paired individuals, egg incubation, and larval rearing either directly at the original habitat of the parents or in reconstructed sites designated for population reinforcement. This method may result in higher survival rates compared to laboratory-based reintroduction. The spawning cage also allows the assessment of adverse environmental factors (e.g., sudden temperature fluctuations) during natural reproduction in the wild, providing insight into the reproductive success of local populations. Experiments on sperm cryopreservation, spawning substrate preference and feeding behaviour have been conducted under controlled conditions in recent years. Although only a small number of broodstock females are used annually, more than 8,700 individuals of various life stages (larvae, juveniles, adults) have been successfully released back into their original habitat or pilot areas. Currently, we carry out population maintenance and breeding in the artificial ornamental ponds of the Botanical Garden of the Hungarian University of Agriculture and Life Sciences (Gödöllő, Hungary), as most of the natural habitats of the species have dried out in recent years. Furthermore, a multifunctional device has been designed to integrate broodstock spawning, egg incubation, and larval rearing, thereby contributing to the sustainable reinforcement of U. krameri populations. Conservation efforts are currently ongoing.

Once widespread in Flanders (northern part of Belgium), the European weatherfish ( Misgurnus fossilis L., 1758) has been fading away since the 1950s and has reached a critically endangered status. To save this species from extinction, a Species Protection Plan was launched in 2021 focussing on a regional wide innovative eDNA survey, habitat restoration and genetic strengthening of the relic populations by means of a captive breeding program financially supported by LIFE (B4B). a regional wide innovative eDNA survey, habitat restoration and genetic strengthening of the relic populations by means of a captive breeding program financially supported by LIFE (B4B). Although a climate change induced shift in general water management - with attention for more ecologically driven river discharge dynamics (Eflows), rewetting and improving lateral connectivity - provides the right momentum, the road to recovery for this species remains bumpy. On the good side, the species distribution in Flanders seems a bit less dramatic since the eDNA campaign revealed 14 more relic populations, bringing the total currently to 23. Also the breeding program started to pay off with a production of ca. 100.000 individuals in 2025 and the first proof of subsequent natural reproduction in at least one population. On the other hand, classical fishery in most investigated relic populations had a very low success rate, potentially pointing to very low densities. Because of the high demand by different users for the little remaining open space, also habitat restoration remains very challenging in Flanders. Even within the nature conservation sector, the objectives are diverse and sometimes incompatible, leading to delays or even failure to initiate certain restoration projects. Last but not least, the settlement and spread of invasive oriental weatherfish species brings with it new threats and challenges. All the more reason to pool our knowledge and expertise at a European scale, for which SWAMP (Specialist Weatherfish Action and Monitoring Partnership) was recently established. Only by joining forces can we save this enigmatic species from fading further into oblivion (Suppl. material 1).

The Bali Starling (Leucopsar rothschildi), an endemic species of Bali, faces severe threats from habitat loss, poaching, and environmental changes, necessitating effective conservation strategies. This study presents a mathematical model to describe the population dynamics of the Bali Starling within the breeding center at USS Tegal Bunder, TNBB, integrating optimal control theory to improve conservation efforts. The model incorporates key biological factors such as growth, transfer, and habituation processes, and utilizes Pontryagin’s Maximum Principle to determine an optimal control strategy that balances population sustainability with resource efficiency. Numerical simulations compare controlled and uncontrolled scenarios, highlighting the impact of different control cost weights (q) on population management. The results suggest that moderate control interventions (q = 0.06 − 0.10) are most effective, ensuring sustainable population growth while min- imizing intervention costs. These findings provide valuable insights for optimizing captive breeding programs and offer a scientific basis for adaptive conservation strategies to protect endangered species like the Bali Starling.

Climate change has emerged as a dominant driver of global biodiversity loss, profoundly altering zoological diversity, species distribution, and ecosystem functioning. Rising temperatures, erratic precipitation, ocean acidification, and habitat fragmentation disrupt physiological processes, migration patterns, and trophic interactions across taxa. This review explores the impact of climate change on zoological diversity and species distribution. Terrestrial, aquatic, and marine ecosystems exhibit varying degrees of vulnerability, with endemic and specialised species facing heightened extinction risks. Polar fauna such as seals and polar bears, tropical primates, coral reef communities, and migratory birds demonstrate clear evidence of climate-induced population decline and range shifts. Evolutionary responses, including genetic adaptation and phenotypic plasticity, are observed in some taxa but remain insufficient to counter rapid environmental changes. Advances in remote sensing, GIS-based species modelling, and molecular techniques such as genomics and environmental DNA (eDNA) have enhanced understanding of climate impacts and enabled predictive biodiversity mapping. Conservation measures encompassing ecosystem-based adaptation, habitat restoration, captive breeding, and wildlife corridor establishment contribute to mitigating biodiversity loss. Policy frameworks under the Convention on Biological Diversity (CBD), IUCN, and IPCC emphasise integrating nature-based solutions with national climate strategies. Despite significant progress, uncertainties in predictive models, data scarcity, and limited integration between ecological and socio-economic systems impede effective conservation planning. Future research must prioritise long-term ecological monitoring, multi-scale data synthesis, and cross-sectoral policy implementation to enhance resilience. Integrating indigenous ecological knowledge with scientific innovations will strengthen adaptation measures and ensure sustainable biodiversity management in the face of accelerating climatic shifts.

Maturity determination and its potential application for fish captive breeding.

Pituitary transcriptome analysis of spotted scat (Scatophagus argus) with ovaries before and after yolk formation.

The Manapany day gecko Phelsuma inexpectata has experienced drastic population declines over the past decade in its native range on Réunion Island. We detail the establishment of a headstarting programme aimed at improving juvenile survival. Between January 2021 and November 2022, 40 wild-caught hatchlings were raised in captivity until they reached adult size and then reintroduced into their original populations. Geckos were kept in outdoor exo-terrariums within a predator-proof facility. To ensure a consistent food supply for captive geckos, we set up captive breeding of the tropical house cricket, Gryllodes sigillatus. The geckos developed well in captivity and all 40 geckos reached adulthood. Our headstarting programme represents the first local captive management initiative for a Phelsuma gecko.

Captive breeding of the Queensland yellowtail angelfish, Chaetodontoplus meredithi (Kuiter, 1990): Spawning, early ontogeny, larval rearing, and temperature-salinity impacts on hatching and survival

Gonadal morphogenesis and sexual differentiation in rhea (Rhea americana).