Captive rearing is a common practice for the stocking, conservation, and supplementation of fish species worldwide, but captive-reared fish can exhibit altered phenotypes leading to reduced fitness in nature compared to wild conspecifics. In salmonids, certain studies have found limited genetic differentiation between wild and captive-reared fish. However, documented changes in gene expression in hatchery fish have led scientists to investigate epigenetic mechanisms, such as DNA methylation, as a source of these differences. In this binational collaborative piece, we synthesize the knowledge and efforts of academics and government scientists to highlight how interactions between captive rearing and the epigenome elicit parallel phenotypic changes across salmonid species. We examine the known and potential links between DNA methylation and the phenotypic effects of captive rearing including changes in behavior, color, gut microbiomes, and developmental abnormalities. We review efforts to minimize these phenotypic and epigenetic effects including attempts to modify the hatchery environment and rearing protocols. We provide a framework to integrate epigenetic considerations into hatchery rearing protocols by weighing the heritable nature of DNA methylation with the goals of different captive rearing programs and explore whether minimizing the phenotypic and epigenetic effects of captive rearing is worthwhile. We examine heritability and persistence of epigenetic effects, and we propose the exploitation of heritable bet-hedging as an epigenetic buffer to increase post-release survival. We also suggest novel applications of epigenomic biomarkers as a non-lethal method for post-release monitoring. Ultimately, collaborative multi-disciplinary research across species is needed to understand the comprehensive effects of captive rearing, reduce the ecological impacts of captive fish in the wild, and increase population resilience. Integrating epigenetics into fish hatchery management will provide new opportunities for optimizing and improving captive rearing.

The transport and release of captive-reared fish into the natural environment are crucial components of stocking and reintroduction programs but these procedures can cause significant stress. A “soft” release strategy, in which fish are allowed to acclimate to the novel environment prior to release, can reduce transport-induced stress compared to a traditional immediate or “hard” release. We investigated whether soft release can effectively mitigate transport stress in juvenile lake sturgeon. We transported sturgeon for 6 h via stocking trailer and then assigned them to three simulated release treatments in the hatchery: hard release, 24 h soft release and 48 h soft release. We compared these treatments to a baseline treatment (non-transported fish). We blood sampled all fish upon release to evaluate stress physiology via cortisol, glucose and lactate. We measured the metabolic rate of baseline, hard release and 24 h soft release fish and the activity levels of all fish at 24 h and 48 h post-transport. We then re-sampled blood from all fish one-week post-release to evaluate recovery. We found that transport altered sturgeon physiology. Hard-released fish exhibited higher metabolic rates and lactate levels upon release than 24 h soft-released fish, while cortisol and glucose did not differ between treatments. Metabolic rate, lactate and activity data suggest that fish recovered from transport stress within 24 h under soft release conditions. Our results suggest that holding lake sturgeon in a predator-free enclosure for 24 h before release promotes physiological recovery and may therefore enhance post-release survival in the wild.

The use of live gene banks to preserve genetic diversity is on the rise as global biodiversity declines. Gamete cryopreservation can be used in addition to live gene banks to preserve genetic diversity while minimizing domestication effects; however, it remains unclear whether fitness-related traits are affected by this process. The established Live Gene Bank for endangered Inner Bay of Fundy Atlantic salmon (Salmo salar) was used to assess whether sperm cryopreservation affects sperm metrics, fertilization, survival, alevin DNA methylation signatures, offspring morphometrics, and age at sexual maturity. A split clutch design was used to reduce parental effects between cryo- and fresh-derived offspring. Cryopreservation significantly reduced sperm motility and fertilization success, as well as embryo and alevin survival. Cryo-derived individuals at 50% hatch were shorter and had smaller yolk-sac area compared to fresh-derived individuals. Cryo-derived individuals were significantly larger at first feeding than fresh-derived individuals; however, there were no differences in length, mass, or condition factor at later life-stages. Furthermore, there was no difference in age at sexual maturity. At the alevin timepoint, there was 493 differentially methylated regions. This study demonstrates that cryopreservation appears to have minimal impact on the tested fitness-related traits, suggesting that individuals may have similar post-release survivorship and growth. However, observed differences in DNA methylation could affect gene expression and other fitness related traits. These differences could be inherited, which could reduce genome stability and integrity effecting conservation program goals to maintain genetic diversity. Thus, further research is needed to assess generational DNA methylation impacts.

With the rapid decline of aquatic biodiversity, conservation tools such as captive breeding for reintroduction are becoming more common. A major challenge, however, lies in determining which species should be prioritized for such efforts. One effective method is to assess species' life history and ecological traits, which are often associated with extinction risk and can provide critical insights for guiding species prioritization. In this study, we assessed all small-bodied minnow and darter species in North America (i.e., Canada, the United States and Mexico) to determine if life history and ecological traits could predict their conservation status. We analysed 13 life history and ecological traits in relation to the IUCN conservation status for 220 species of minnow and 183 species of darters. For minnows, traits such as substrate, climatic zone, diet, feeding location, total length and maximum water temperature were associated with a higher risk of being threatened. For darters, the traits associated with an increased risk of being threatened were climatic zone and total length. Taken together, this study identifies key life history and ecological traits that influence the conservation status of small-bodied fishes and provides actionable insights for prioritizing species for captive breeding programmes. These findings can guide conservation practitioners in developing species-specific, proactive recovery strategies to prioritize species at risk and enhance conservation efforts before they become threatened in the wild.

Habitat degradation is a growing concern to the survival of the redside dace [Clinostomus elongatus (Kirtland, 1840)], a minnow species (family: Leuciscidae) native to the Great Lakes of North America and their connecting water systems. Increased water turbidity due to suspended particulates from pollution, urbanized habitat and forest fires is of particular concern. The effect of increased water turbidity on the distribution of olfactory sensory neurons was examined in the present study. A calretinin antibody labelled olfactory sensory neurons lining the lamellae of the peripheral olfactory organ situated within the nasal cavity. An S100 antibody labelled the sparse crypt cell olfactory sensory neurons located on both the olfactory lamellae and in a previously undescribed crypt cell location: the epithelial lining of the nasal cavity. In redside dace held in turbid water for 72 h, small patches of olfactory lamellae were devoid of calretinin immunolabelled olfactory sensory neurons. While S100 immunolabelled crypt cell density was unchanged in the lamellar olfactory epithelium, the density of crypt cells increased in adjacent epithelium lining the nasal cavity. These cellular changes in the peripheral olfactory organ under conditions of increased water turbidity may affect important capacities related to survival such as foraging and reproductive activity.

Species recovery efforts may require establishment of ex situ populations to supply augmentation or reintroduction projects. The Eastern Massasauga (Sistrurus catenatus) is a small rattlesnake with an ex situ breeding program maintained by a consortium of conservation breeding centres. Small population size in human care has restricted the supply of animals for in situ conservation, thus, the development of improved ex situ breeding protocols was recommended. The objectives of our retrospective study were to (1) describe and compare reproductive traits between two groups of Massasauga litters born in human care: wild-bred litters (i.e., conceived in the wild) and zoo-bred litters, (2) test for factors associated with improved reproductive output in zoo-bred litters, and, (3) make recommendations for standardizing ex situ breeding protocols. Data were collected on Massasauga birth events that occurred from 2000 to 2020 at 13 North American zoos and partner facilities. Six outcomes related to litter size and survival of offspring were compared between zoo-bred (n = 43) and wild-bred litters (n = 51). Odds ratios were used to test for correlations between nine predictor variables and four response variables in zoo-bred litters. We found higher mean litter size and number of live young per litter in wild-bred litters (12 and 10, respectively) compared to zoo-bred litters (6 and 2). Wild-bred litters more often contained live young and less often contained unfertilized ova (98% and 34% of litters, respectively) than did zoo-bred litters (58% and 81%). Experimentation on the effectiveness of alternative mating practices is warranted to improve reproductive output in human care, thereby increasing capacity to support in situ conservation.

The circadian clock has evolved to synchronize animal behaviour and physiology with the external environment. Present in almost all cells, the clock is made up of a transcription-translation feedback loop that is responsive to cues such as light/dark cycles (photoperiod) and the time of feeding. Chinook salmon (Oncorhynchus tshawytscha) is a fish species whose clock is thought to be adapted in natural populations according to their latitude, where photoperiod variation can be extreme in northern spring/summer conditions. Here, we probed for the expression of circadian clock genes in four tissues of juvenile Chinook salmon under different environmental conditions. We find that the circadian clock is optimal when photoperiod is coupled with regular feeding during daylight hours. We further tested the effects of constant light and time-restricted feeding, environmental factors that are known to affect daily gene expression rhythms, on the expression of clock genes, appetite-regulating hormones, and metabolic regulators in the intestine of juvenile Chinook. We find that overall constant light is chrono-disruptive irrespective of the timing of food. The resulting disruption in gene expression produces aberrant rhythms, and affects glucose homeostasis, despite an increase in growth. Our data suggests photoperiod and time-restricted feeding could be optimized in Chinook aquaculture and raise the question of whether and how photoperiod changes are compensated in northern-adapted populations.

Poor habitat quality is one of the most important reasons for reintroduction failure of reptiles; therefore, release site suitability ought to be evaluated prior to conducting conservation translocations. In temperate zone snakes, translocations have failed due to high overwinter mortality, so practitioners have recommended that release sites be located near suitable hibernacula. The presence of a Life Zone (LZ), the underground space above the groundwater table and below the frost line, may indicate the presence of suitable hibernation habitat. Identification and validation of sites with LZ, however, is challenged by the dynamic nature of groundwater and frost levels, coupled with the secretive nature of hibernating snakes. In this study, our goals were to 1) identify potential reintroduction sites for the globally imperiled Eastern Massasauga (Sistrurus catenatus) in southern Canada based on the presence of a LZ, 2) to validate the suitability of those reintroduction sites by hibernating a surrogate species (Eastern Gartersnake, Thamnophis sirtalis) in constructed hibernacula, and, 3) to determine if two separate measures of LZ were associated with the survival of individual gartersnakes to the end of hibernation. Four 1-ha study grids, each consisting of multiple groundwater and frost monitoring stations, were surveyed from 2015 to 19. Release sites were identified in each grid where a LZ of >= 10 cm was observed consistently for at least 2 full winters, and gartersnakes were successfully hibernated therein and at 2 reference sites over 3 winters. Overall, survival of subadult/adult snakes was very high (100 %; n = 20), regardless of site, whereas juvenile survival was lower (78 %; n = 93). A Kaplan-Meier test indicated that juvenile survival differed significantly among sites, and ranged from 60 % to 100 %. GLMM analysis indicated that mass at ingress had a significant positive effect on snake survival during hibernation. The temporary loss of a LZ did not impact snake survival. Contrary to our expectations, snake survival in hibernacula was negatively associated with both minimum LZ size and LZ frequency (i.e., the % of sampling occasions when LZ size >= 10 cm). Hibernating snakes can tolerate periods with a very small or non-existent LZ, but a large LZ may become unsuitable to juveniles, possibly due to a lack of moisture. Our results will guide the selection of release sites for Massasauga reintroductions, and for the development of a rigorous release site selection process for temperate zone snakes.

Standardized estimates of a species' distribution before and after translocation can inform whether a reintroduction project was effective at population establishment. Occupancy modeling has grown in popularity to estimate the distribution of cryptic animals, including viperid snakes, because it can account for variations in detection probability (P) generated by site-, survey-, and population-specific factors. We estimated occupancy and P in an endangered subpopulation of the cryptic North American pit-vipers (Eastern Massasaugas, Sistrurus catenates; hereafter Massasauga[s]) in preparation for future conservation translocations. During a 6-yr period at the Ojibway Prairie Complex and Greater Park Ecosystem, in Ontario, Canada, we conducted more than 1740 repeated standardized surveys at 40 plots (each ca. 2.4 ha) by using two methods (visual encounter and artificial cover object), across three seasons (spring, summer, and fall), and with different types of search effort (single vs. team surveys) and analyzed a suite of detection histories by using occupancy modeling. Massasaugas were detected at only 10% of survey sites (n = 4/40), and the species was presumed undetected at one additional site after accounting for P (estimated occupancy, 13%). The P for Massasaugas ranged from 0.01 to 0.73 and was most strongly influenced by search effort, season, and trap response (i.e., "trap-happy"individuals repeatedly found in the same locations). The detection probability was significantly inflated during surveys when there was at least one trap-happy snake present. Across top ranking models (based on Akaike's Information Criterion scores), team visual encounter surveys in spring and summer, and conducting at least two surveys per week, generated an average P >= 0.15 after accounting for a trap response. Conversely, fall surveys and artificial cover object surveys generated a P , 0.15. Our study provides direction to other conservation practitioners working with small populations of cryptic snakes and will inform monitoring regimes for future conservation translocations.

Chinook salmon ( Oncorhynchus tshawytscha) have complex life histories with two distinct male alternative reproductive tactics (ARTs). The larger and older "hooknose" males battle for position to spawn with nesting females whereas the precociously maturing "jack" males use a sneaking tactic to gain access to females. Although dietary niche is known to differ between ARTs of other fish taxa, no research to date has examined these differences in a salmonid. Here, we used S15N and S13C stable isotope analyses to compare the dietary niches of female, hooknose male, and jack male Chinook salmon sampled from a Lake Ontario tributary. We found that all three life histories shared similar S15N values, whereas jack males had greater S13C values compared to hooknose males, with females having intermediate values. Jack males also had notably little overlap in their isotopic niche space with hooknose males and females, indicating that jack males occupy a distinct isotopic niche in Lake Ontario. We discuss habitat partitioning and differences in dietary niche as explanatory factors. Altogether, these data unveil novel distinctions in isotopic niche within the complex life history strategies of Chinook salmon in Lake Ontario that can inform management decisions and provide avenues for future research.

Due to the alarming rates of freshwater fish extinctions, urgent action is needed to develop captive breeding programs for imperiled species and enhance existing practices to improve reproductive outcomes. Here, we investigated the effects of enrichment on gamete production, quality, and spawning coloration following hormone injection (i.e. carp pituitary, gonadotropin) in the endangered redside dace Clinostomus elongatus , a sexually dimorphic, presumably obligate nest parasite. C. elongatus were reared in either a non-enriched environment (i.e. barren) or an enriched environment (i.e. substrate, plants, and spawning nest-building hosts) for 1 yr prior to hormone induction. We found no differences in the proportion of free-flowing gamete expression between male and female C. elongatus in the non-enriched and enriched environments. However, males reared in enriched environments had higher sperm motility, while among females, there was no significant difference in egg diameter. Furthermore, enrichment was found to influence spawning coloration, with males and females reared in enriched environments displaying redder hues compared to those reared in non-enriched environments prior to hormone induction. However, post hormone injection, no significant differences in red coloration were observed between non-enriched and enriched males and females, indicating that hormone induction improved coloration in non-enriched fish. This study highlights the effect of enrichment on gamete production, quality, and spawning coloration and provides information for captive breeding C. elongatus . These findings provide valuable insights into the potential of enrichment and induction techniques to enhance reproductive outcomes when captively breeding endangered species of fishes.

Reintroduction is an important tool in the conservation and recovery of aquatic species at risk. However, components of the reintroduction process such as transportation have the potential to induce physiological stress and the extent to which preparatory techniques can mitigate this stress is poorly understood in small-bodied fishes. To address this concern, we studied the effect of transport on two fitness-related performance measures: maximum metabolic rate and thermal tolerance in redside dace (Clinostomus elongatus), an imperilled small-bodied stream fish native to eastern North America. Prior to transportation, we manipulated the body condition of redside dace over a 12-week period, by providing either low (1% of their total body mass) or high (2% of their total body mass) rations. The goal of this manipulation was to influence body condition, as higher body condition can enhance physiological performance. Subsequently, redside dace were transported for varying durations: 0, 3, and 6 h. Following transportation, we measured maximum metabolic rate (µmol/h) and thermal tolerance (CTmax, °C). Our results indicate that neither transport nor body condition had a significant effect on maximum metabolic rate or thermal tolerance (CTmax). These findings provide preliminary evidence that redside dace can physiologically tolerate transport based on the endpoints measured and this information may possibly be extended to other small-bodied fish, for which information is lacking.

ObjectiveWe examined whether an extended acclimatization period prior to release (soft release) can allow transported fish to recover from the physiological stress associated with transport compared with conventional release methods, which provide fish with no acclimatization period prior to release (hard release).MethodsWe monitored an Atlantic Salmon Salmo salar stocking team during a standard reintroduction operation and compared their conventional hard-release method (i.e., immediate release after transport with no acclimatization period) to a soft-release method (i.e., 2 and 4 days in-river acclimatization prior to release). Following a 2.5-h transport event, hard-release fish were immediately blood-sampled for their physiological stress response (cortisol, glucose, and lactate). Soft-release fish were blood-sampled for their physiological stress response following 2 or 4 days of in-river acclimatization.ResultWhile hard- and soft-release fish demonstrated significantly higher cortisol, glucose, and lactate concentrations compared with control fish, cortisol concentrations remained elevated for both the hard- and soft-release groups. However, glucose and lactate concentrations were significantly lower in soft-release fish compared with hard-release fish.ConclusionSoft-release provides fish an extended acclimatization period that was found to impact transport-related physiological stress in fish. Our findings will inform management agencies and practitioners focused on improving the success of salmonid stocking and reintroduction programs.

Urbanization is a widespread threat to freshwater ecosystems. After rainfall, urban streams often experience unnaturally fast water flows and acute increases in suspended sediment due to the high degree of adjacent impervious land surface. Suspended sediments may negatively affect fishes by impairing respiration, and reduced water clarity may also affect social behaviours such as schooling that are dependent on visual cues. Given these two mechanisms of harm, suspended sediments may therefore exacerbate the difficulty of swimming at high water velocities. We tested this idea using imperilled Redside Dace (Clinostomus elongatus) to examine the consequences of suspended sediment on swimming performance and schooling behaviour. Using individual fish, we assayed swimming performance (standard critical swim speed test) and tail beat frequency and amplitude under a range of ecologically relevant sediment concentrations. Next, we measured the impact of sediment on the cohesion and polarization of schools. Swimming performance of individual fish was not affected by suspended sediment levels we examined. School polarization was positively correlated with water flow overall and at the fastest flows we tested; schools were more polarized when exposed to sediment. School cohesion decreased with increasing flows and was unaffected by the suspended sediment levels we examined. Our results collectively suggest that swimming performance of Redside Dace may be resilient to ecologically relevant acute suspended sediment exposure.

Investigation of the reproductive phenology and spawning behaviour of imperilled species in relation to environmental variability is needed to understand a critical component of species life history. In this study, we used redside dace (Clinostomus elongatus), a freshwater leuciscid listed as Endangered under Canada's Species at Risk Act, to model spawning phenology and make predictions about spawning initiation using historical and climate change projected thermal cues (measured as cumulative growing degree days), and provide an ethological description of spawning behaviour. Logistic regression models applied to 4 years of average daily stream water temperature data and field behavioural observations of the onset of spawning activity indicated a 50% probability of spawning initiation when cumulative growing degree days reached 214 degrees C days and a 95% probability of spawning initiation at 288 degrees C days. Using two climate change scenarios (i.e., a mid-century 1.6 degrees C increase and an end of century 3.6 degrees C increase), spawning initiation was predicted to advance 3 days by the year 2050 and 7 days by the year 2100. Underwater video cameras placed at two sites within an urban stream captured 73 unique spawning events revealing that redside dace spawn in pairs as well as in dense, tightly packed groups (more than 20 individuals). Moreover, there is evidence of redside dace having a polygynandrous mating system, as female redside dace spawned with multiple males in 45.2% of the total spawning events recorded. Taken together, this study provides important insights into redside dace spawning initiation and behaviour, key life-history traits having conservation implications for future reproductive success and, ultimately, population dynamics.

Behavioural plasticity plays an important role in an organism's ability to adapt to captive settings, but a lack of perceived predation risk during early development in captivity can lead to diminished anti-predator behaviours. Here, we used Atlantic salmon ( Salmo salar) to test whether early developmental exposure to alarm cues (pre-exposure) led to (1) a developmentally plastic response to alarm cue in yearling and (2) an observable change in neural investment. We exposed fry to either a conspecific alarm cue (pre-exposed fish) or control water (non-exposed fish) and measured activity related to anti-predator behaviour such as time spent motionless, number of aggressive acts, and time spent associated with shelter. We found no indication of a developmentally plastic response to early alarm cue exposure, but we found that pre-exposed fish developed relatively smaller olfactory bulbs compared to non-exposed fish. Our results demonstrate the importance of and ability to exploit plastic responses in captive-reared Atlantic salmon and highlight the need to link behaviour with neuromorphological changes.

Transcriptomic research provides a mechanistic understanding of an organism's response to environmental challenges such as increasing temperatures, which can provide key insights into the threats posed by thermal challenges associated with urbanization and climate change. Differential gene expression and alternative splicing are two elements of the transcriptomic stress response that may work in tandem, but relatively few studies have investigated these interactions in fishes of conservation concern. We studied the imperilled redside dace (Clinostomus elongatus) as thermal stress is hypothesized to be an important cause of population declines. We tested the hypothesis that gene expression-splicing interactions contribute to the thermal stress response. Wild fish exposed to acute thermal stress were compared with both handling controls and fish sampled directly from a river. Liver tissue was sampled to study the transcriptomic stress response. With a gene set enrichment analysis, we found that thermally stressed fish showed a transcriptional response related to transcription regulation and responses to unfolded proteins, and alternatively spliced genes related to gene expression regulation and metabolism. One splicing factor, prpf38b, was upregulated in the thermally stressed group compared with the other treatments. This splicing factor may have a role in the Jun/AP-1 cellular stress response, a pathway with wide-ranging and context-dependent effects. Given large gene interaction networks and the context-dependent nature of transcriptional responses, our results highlight the importance of understanding interactions between gene expression and splicing for understanding transcriptomic responses to thermal stress. Our results also reveal transcriptional pathways that can inform conservation breeding, translocation and reintroduction programs for redside dace and other imperilled species by identifying appropriate source populations.

Advancements in the field of reintroduction biology are needed, but understanding of how to effectively conduct translocations, particularly with snakes, is lacking. We conducted a systematic review of snake translocation studies to identify potential tactics for reducing postrelease effects. We included studies on intentional, human‐mediated, wild–wild, or captive–wild translocations to any location, regardless of motive or number of snakes translocated. Only studies that presented results for at least 1 of 4 outcomes (movement behavior, site fidelity, survival, or population establishment) were included. We systematically searched 4 databases for published studies and used 5 methods to search the gray literature. Our search and screening criteria yielded 121 data sources, representing 130 translocation cases. We quantified the association between 15 translocation tactics and short‐term translocation outcomes by calculating odds ratios and used forest plots to display results. Snake translocations involved 47 species (from mainly 2 families), and most were motivated by research, were monitored for at least 6 months, occurred in North America, and took place from the 1990s onward. The odds of a positive snake translocation outcome were highest with release of captive reared or juvenile snakes, release of social groups together, delayed release, provision of environmental enrichment or social housing before release, or minimization of distance translocated. The odds of a positive outcome were lowest when snakes were released early in their active season. Our results do not demonstrate causation, but outcomes of snake translocation were associated with 8 tactics (4 of which were strongly correlated). In addition to targeted comparative studies, we recommend practitioners consider the possible influence of these tactics when planning snake translocations.

Failure of reintroduction efforts of extirpated populations is thought to be linked to maladaptive behaviors exhibited by captive-bred individuals in the environment where they are released. Soft-release conditioning tactics attempt to reduce maladaptive behaviors by providing reintroduced animals an acclimatization period prior to release. We used implanted passive integrated transponder tags and antennae to monitor the spatial and temporal dispersal behavior of captive-bred Atlantic Salmon Salmo salar that were acclimatized for 6 d prior to release (soft-release), with fish that were directly released (hard-release) into East Duffins Creek in Ajax, Ontario, Canada. In total, 232 of the 610 tagged fish (38%) dispersed from the release site. Downstream spatial dispersal did not differ significantly between the hard-release (32%, n = 98 of 310) and soft-release fish (30%, n = 91 of 300), but the hard-release fish were significantly more likely to move upstream (11%) than were the soft-release fish (3%). Timing of dispersal also significantly differed between the two groups: soft-release fish were detected dispersing, on average, approximately 15 d earlier than hard-release fish. These results suggest that soft-release tactics do affect dispersal behavior, and the findings will be of particular interest to fisheries management agencies that are charged with improving the success for stocking salmonids as part of reintroduction efforts.

A decline in sperm quality with age is a common prediction of senescence-based hypotheses and empirical studies. While widely studied across taxa, there is little known on the effect of ageing on sperm quality in amphibians, especially in captive populations used for controlled propagation and reintroduction efforts. Here, we investigated variation in sperm quality metrics (i.e., motility, concentration, and morphology) in the endangered Mississippi gopher frog (Lithobates sevosus) among males of three age categories using individuals from captive breeding populations housed at three different zoological institutions. Different aged males across the species expectant lifespan (1-9, 1-2, 3-4, and 8-9-year-old subcategories) were chosen in an attempt to identify an optimal breeding age relevant for captive breeding programs. Moreover, we explored and statistically controlled for potential differences in sperm quality which may be attributed to the type of induction hormones and source populations that differed among institutions. Results indicated that males of different ages did not differ in sperm motility or concentration. However, we did find that older males (8-9 years old) had significantly longer sperm than other age categories and younger males (1-2 years old) had significantly more atypical sperm than other age categories. Furthermore, we found no significant differences in any sperm quality metrics between the different induction hormones or source populations used at the different institutions. Within a captive breeding program, this information is especially valuable as our results indicate that males that have only recently sexually matured may not be ready to breed, while older males maintain sperm quality metrics presumably related to fertilization success.