Out of their depth: The successful use of cultured subtidal mussels for intertidal restoration

Ecosystem restoration has proliferated across the globe to combat widespread ecosystem decline. Translocations of viable individuals into degraded habitats form a core component of restoration efforts, but the selection of source populations poses challenges because phenotypic differences between source populations and depleted populations result in low post‐translocation survival. Intertidal mussel restoration is typically reliant on subtidal source populations despite their weaker shells, lighter weights, and poorer respiratory abilities compared to intertidal mussels. Intertidal mussel restoration using subtidal mussels has recorded very low survival, leading to suggestions that subtidal mussels are unfit for the intertidal zone, effectively eliminating the possibility of translocation‐based intertidal mussel restoration. In this study, small‐scale intertidal mussel restoration was tested using subtidal cultured mussels transplanted to paired plots, half in the lower intertidal and half in the upper subtidal. The results demonstrate the first scientific evidence of the successful restoration of intertidal mussel reefs using subtidal mussels at this scale. Specifically, one location recorded very high survival after 12 months (95.1 ± 0.6%; mean ± SE), comparable to the survival recorded in the subtidal zone (97.6 ± 0.3%). Translocations to the intertidal at the other two locations experienced mortality during the Austral summer (final survival: 81.3 ± 1.6% and 56.6 ± 7.4%), which directly correlated with exposure to extreme temperatures (>40°C). These results reveal that despite phenotypic differences, subtidal cultured mussels are potential sources for successful intertidal restoration. However, care should also be taken to avoid locations prone to high temperatures, particularly in light of a warming global environment. Ultimately, to achieve the massive upscaling in restoration called for by the UN Decade on Ecosystem Restoration, we encourage restoration managers to think broadly about potential source populations, avoid rejections based solely on phenotypic differences, and explore every potential avenue for restoration success.

K E Y W O R D S conservation, heat stress, New Zealand, Perna canaliculus, shellfish, translocation

| INTRODUCTION
Ecosystems globally have been decimated as a result of climate change, human extraction, and land-use changes, resulting in the declaration of 2021-2030 as the UN Decade on Ecosystem Restoration (UN Resolution 73/284). The translocation of living organisms from one area to another is a strategy increasingly used to restore degraded ecosystems and conserve threatened areas (Gann et al., 2019;IUCN, 1987;Weeks et al., 2011). Translocation facilitates the restoration of struggling or non-functional populations with individuals from successful stocks, ultimately aiming for the survival and self-sustainability of the newly restored population (IUCN/SSC, 2013). To achieve high survival and self-sufficiency, source populations need to be biologically similar to extant or historical recipient populations (Griffith et al., 1989;Pérez et al., 2012). Genetic differences between source and recipient populations have been widely recognized as a significant impediment to translocation success (Gaffney, 2006;Weeks et al., 2011); however, increasing attention is being paid to the role phenotypic differences may play in successful restoration efforts (Fariñas-Franco et al., 2016;Watters et al., 2003).
Motivated by substantial declines in global mussel populations (Lotze et al., 2006), mussel restoration has expanded in recent decades (Toone et al., 2021) and is often centered around translocation efforts (e.g., Fariñas-Franco & Roberts, 2014;Sea et al., 2022). However, mussel restoration via translocations has had mixed success with some restored reefs never reaching self-sufficiency (e.g., de Paoli et al., 2015;Kristensen et al., 2015;Wilcox et al., 2018). The intertidal zone is a historically common habitat for mussels; however, unsuccessful outcomes from intertidal restoration projects are typical, as reefs restored with translocated mussels frequently fail to establish successful populations including blue mussels, Mytilus edulis, in the Netherlands (Capelle et al., 2014;de Paoli et al., 2015;Schotanus, Walles, et al., 2020) and Wales (Dare & Edwards, 1976) as well as ribbed mussels, Geukensia demissa, in the United States (Stiven & Gardner, 1992). This is particularly concerning as intertidal mussel reefs perform a number of important ecosystem services not similarly accomplished by subtidal populations, including habitat generation for intertidal organisms (Borthagaray & Carranza, 2007;Saier, 2002), shoreline stabilization (Meadows et al., 1998), and easily accessible food provision for humans (Keough et al., 1993). Additionally, intertidal mussel restoration may be a more attractive option for organizations or communities with limited resources because intertidal restoration can supplant the need for equipment like SCUBA gear or boats, reducing the overall cost of restoration (Bayraktarov et al., 2016).
A common feature of unsuccessful intertidal restoration projects has been the use of subtidal mussels (both wild-harvested and aquaculture-grown) as source populations. In contrast, relatively high intertidal survival of mussels has been achieved when intertidal mussels were used as the source population for restoration in the Netherlands (de Paoli et al., 2017) and the United States (Derksen-Hooijberg et al., 2018). The rationale behind the use of subtidal source populations is clear (i.e., the loss of one intertidal population to support another is, at best, net-neutral); however, concerns are raised by the morphological differences between subtidal and intertidal mussels. For example, subtidal mussels typically have thinner and weaker shells (Beadman et al., 2003), lighter weights (Hickman, 1979), and greater meat-shell ratios (Fern andez-Reiriz et al., 2016) than their intertidal counterparts as well as physiological differences, such as poorer respiratory abilities (Tagliarolo et al., 2012) and reduced hypoxia tolerance (Altieri, 2006). These morphological and physiological differences expressed in response to growth in specific tidal levels may hinder the ability of subtidal mussels to survive in the intertidal. This is demonstrated by green-lipped mussels (Perna canaliculus) which, when translocated from the lower intertidal to the upper intertidal along the same mussel reef, have slower growth, a lower gonadosomatic index, and stress-induced spawning, whereas individuals translocated from the upper intertidal to another position on the upper intertidal do not experience these same negative impacts (Petes et al., 2007).
The exact factors that lead to lower survival among subtidal versus intertidal mussels that are translocated into the intertidal are unclear, but well-documented morphological and physiological differences are likely. Predation and its interaction with mussel phenotypic characteristics has been identified as a key element of mussel reef population dynamics (Nehls et al., 1997;van der Heide et al., 2014) and a common source of mortality for intertidal mussel restoration (Capelle et al., 2014;Ens & Alting, 1996;Schotanus, Walles, et al., 2020). Preferential predation can lead to disparate impacts on different populations (Navarrete & Menge, 1996;Smallegange & Van Der Meer, 2003). For example, predators like sea stars will preferentially consume mussels that are smaller (Hummel et al., 2011;O'Neill et al., 1983) and easier to access (Agüera et al., 2020), suggesting that weaker-shelled mussels (i.e., mussels grown in the subtidal) may be more susceptible to predation than hardier, intertidally grown, mussels. Additionally, intertidal mussels face the added pressure of wave action which can dislodge newly restored mussels, leading to low survival Schotanus, Walles, et al., 2020). The stress of wave dislodgement may be particularly acute for mussels grown subtidally as they have thinner byssus threads than intertidal mussels (Alder et al., 2022). The morphological and physiological differences of subtidal source populations have been suggested as potential causes of the low success rate of intertidal mussel restoration efforts (de Paoli et al., 2015). However, there has not been any focused experimental work to quantity whether subtidal mussels are wholly unfit for intertidal restoration or simply more susceptible to certain stressors and therefore able to be restored intertidally in areas where these stressors are diminished.
This study aims to determine if mussels sourced from the subtidal can be used for restoration to the intertidal in the absence of high predation and wave stress. Specifically, a range of success metrics, including survival, growth, and condition, are compared between cultured subtidal mussels transplanted to paired plots, half in the lower intertidal and half in the upper subtidal at three sites. Ultimately, we hypothesized that subtidal mussels are incompatible with the intertidal and will therefore experience lower survival than the same mussels restored to the upper subtidal.

| Study area
Kenepuru Sound is an inner branch of the Marlborough Sounds, a complex drowned river valley system at the northern end of New Zealand's South Island (Figure 1). Kenepuru Sound once supported extensive subtidal and intertidal green-lipped mussel populations (P. canaliculus, hereafter "mussels"), until overharvesting in the 1970s and 1980s resulted in a 97% decline in total local mussel populations Urlich & Handley, 2020). Notably, intertidal mussel reefs in Kenepuru Sound historically recorded elevated levels of juveniles compared to subtidal reefs, suggesting the intertidal zone may provide important recruitment refugia that could stimulate natural F I G U R E 1 Source location of the longline subtidal cultured mussels used for restoration (Elaine Bay) and the three deployment locations in Kenepuru Sound. recovery elsewhere if restored (Stead, 1969). Due to the labyrinthine nature of the Marlborough Sounds, Kenepuru Sound has a very reduced wave fetch, greatly limiting the severity of any shoreline wave action (Heath, 1974). Additionally, prior subtidal mussel restoration in Kenepuru Sound recorded lower abundances of the eleven-armed sea star, Coscinasterias muricata, a major local predator of mussels, compared to other parts of the Marlborough Sounds, suggesting that predation pressure is minimal in Kenepuru Sound .
Due to the low wave action and predation pressure in Kenepuru Sound, as well as the prevalence of historical mussel populations, three intertidal locations were chosen for experimental mussel restoration in the Sound (Double Bay; Goulter Bay; Nopera; Figure 1). All three locations were rocky, south-facing, and previously supported substantial intertidal mussel populations (Flaws, 1975;Stead, 1969), although only scattered, remnant, mussels were present at the time of restoration.

| Mussel deployment
In late May 2021, a total of 4.5 t of mussels grown subtidally on suspended aquaculture ropes in a mussel farm in Elaine Bay, an environmentally similar bay $20 km NW of the study sites, were harvested for translocation to the three experimental locations using an industrial mussel harvesting vessel ( Figure 1). The mussels were 4 years old (shell length 98.4 ± 1.9 mm; mean ± SE) and sourced from wild mussel larvae collected locally, outgrown on settlement ropes in the area, and then transferred to the longlines. During harvesting, the mussels were carefully stripped from the ropes to preserve clumps of mussels held together by byssus threads and then placed into 18 bulk bags with each bag weighing approximately 250 kg, as verified by an on-board scale. An initial sample of 40 mussels haphazardly selected during the harvesting process was taken to determine pre-deployment mussel length and condition data.
At each location, six plots in the upper subtidal (i.e., <0.5 m depth on low spring tides; maximum tidal range $3 m), each measuring approximately 4 m 2 with 10 m between each plot, were marked with floating buoys the day before deployment for a total of 18 plots. Between 4 and 6 h after harvesting, one 250 kg bag of mussels was emptied into each marked plot using a vessel crane. All translocated mussels were visually assessed the following day to confirm successful translocation and allowed to acclimate for 1 month. After 1 month (late June 2021), three randomly selected mussel plots at each location were translocated to the lower intertidal (approximately 1 m shallower) by hand. The remaining plots were maintained as subtidal comparisons and the mussels were redistributed within their plot to simulate translocation and control for the additional movement experienced by the intertidal plots ( Figure 2).

| Survival monitoring
Survival monitoring was conducted every 3 months after the final translocation (i.e., early October 2021, early January and April 2022, and late June 2022). The intertidal plots underwent additional monitoring during potentially stressful periods. These periods were 1-week and 1-month post-translocation (early July and early August 2021, respectively) to assess mortality potentially associated with the stress of initial translocation, and during the Austral summer months (December 2021 and February and March 2022) to assess mortality potentially associated with heat stress. All monitoring was conducted on low spring tides to preclude the need for SCUBA diving.
F I G U R E 2 Mussels restored to the intertidal (a) and subtidal (b) in Goulter Bay 1 month after translocation. Photos taken at low spring tide.
Mussel survival was quantified by haphazardly placing a 0.25 Â 0.25 m 2 quadrat four times in each restored mussel plot, a method adapted from Wilcox et al. (2018) and . Each mussel inside the quadrat was counted and assessed as either dead or alive, with either an empty whole shell or two empty half-shells comprising one dead mussel. The survival in each plot was calculated by determining the average proportion of live mussels for the four quadrants. The presence of any prominent predators, specifically the eleven-armed sea star, was noted at each monitoring point. Notably, predators like crabs and rays which crush mussel shells rather than leaving behind whole shells have not been recorded to prey on green-lipped mussels in the area , improving the reliability of empty whole shells as a proxy for mortality.

| Growth and condition monitoring
To monitor mussel growth and condition, a haphazard sample of five mussels was collected from each plot at the 3-, 6-, 9-, and 12-month monitoring points. Mussels were stored at À20 C until processing, at which time they were measured along the anterior-posterior axis of the shell to provide mussel size data and separated into flesh and shell components. The shells and flesh of each mussel were then dried at 60 C until a constant weight was recorded ($48 h). The dry condition index was then determined using the following formula: Dry Weight of Flesh Â 100/Dry Weight of Shell (Lucas & Beninger, 1985). The same length and condition process was undertaken for the sample of 40 mussels taken at the time of deployment to provide baseline data.

| Air and temperature exposure
To quantify exposure times and assess the average and extreme temperatures experienced by the restored intertidal mussels, temperature data was collected using a HOBO Water Temperature Pro v2 Data Logger placed in the center of each intertidal plot, nestled among the restored mussels. Data was collected by the logger every 10 min starting from the 3-month monitoring point in October 2021 until the conclusion of monitoring in June 2022. To quantify average aerial exposure times at each plot, data from a 29-day period in January 2022 were extracted, comprising a complete tidal cycle at a time when the air temperature was substantially different from the water temperature (i.e., hotter during the day and colder at night). Any 10-min data point during which the recorded temperature was 1 standard deviation hotter or colder than the average temperature recorded at that location over the 29 days was quantified as an airexposed time point. These estimated exposure times were verified by comparison with tidal charts for the area, confirming that all determined exposure points coincided with low tides. Mean temperatures for each plot were determined as well as time exposed to extreme (>40 C) temperatures.

| Statistical analyses
Analyses of Variance (ANOVAs) were used to compare the tested success metrics after normality and homogeneity of variances were confirmed with Shapiro-Wilk's tests and Levene's tests, respectively. Specifically, to compare survival and condition between mussels restored to the intertidal and subtidal zones as well as between locations and time points, three-way mixed ANOVAs were performed. While survival data often tend towards a binomial distribution and require transformation (Sokal & Rohlf, 1981), the data in this experiment were normally distributed and nonbinomial, precluding the need for additional transformation (Warton & Hui, 2011). Depth (i.e., intertidal and subtidal) and location were assessed as between-subject factors, while monitoring time point was assessed as a within-subjects factor to account for repeated measurements of the same restored mussel plots at each time point. To assess intertidal survival at monitoring points when no subtidal mussels were sampled (e.g., monitoring points other than 3, 6, 9, and 12 months), a two-way mixed ANOVA was performed with location assessed as a between-subjects factor and monitoring time point as a within-subjects factor. Differences in growth rate between depths and among locations between deployment and the final 12-month monitoring point were assessed with a two-way ANOVA. Differences in air exposure and average temperature exposure of intertidal mussels among the three locations as well as time exposed to extreme heat were all determined with one-way repeated-measure ANOVAs to account for repeated sampling of each mussel plot. All ANOVAs were followed with pairwise comparisons of significant factors using post hoc Turkey tests.
Following analysis of depth, sampling time point, and location on survival, additional analyses were conducted to test the specific impact of temperature and time exposed to extreme heat. The correlation between time exposed to extreme temperatures since the preceding monitoring point and additional mortality since the preceding monitoring point was assessed with a linear mixed model with mussel plot set as a random effect. For example, the cumulative time exposed to extreme heat between the 5-and 6-month monitoring points was directly compared with the mortality that occurred over that same time period. All data analyses were undertaken in R (v4.2.1.; R Core Team, 2022) and significance was defined at the level of p ≤ .05 with Bonferroni adjusted p values used when necessary to control for inflated error due to multiple comparisons.

| Survival
Mussels restored to the subtidal zone did not experience any significant declines in survival across the entire 12-month experiment (Table 1; p > .05; final mean survival = 97.6 ± 0.3%). However, mussels restored to the intertidal all experienced a decline in survival which varied significantly among locations and monitoring time points (interaction effect, F (16, 48) = 6.27; p < .001; Figure 3). The only intertidal mussels to have similar survival to their subtidal counterparts after 12 months (95.1 ± 0.6%; p > .05) were at Nopera. Intertidal mussels at Goulter Bay experienced the next highest intertidal survival (81.3 ± 1.6%), followed by Double Bay which recorded significantly lower intertidal survival than the other two locations (56.6 ± 7.4%; p ≤ .02). This decline in intertidal survival was entirely confined to the Austral summer, with similarly high survival for both depths at all three locations through the 5-month monitoring point (early December 2021; p > .05). However, between the 5and 6-month monitoring points (beginning of Austral summer), there were significant declines in mussel survival intertidally for Double Bay (30.0 ± 8.3%; p < .001) and Goulter Bay (9.6 ± 0.9%; p = .03). After the 6-month monitoring point, the intertidal survival at Double Bay remained lower than the plots at any other location or depth ( p ≤ .05), while intertidal Goulter Bay plots experienced significantly lower survival than any subtidal location (p < .03), but statistically similar survival to intertidal mussel plots at Nopera (p > .05). Between the 7-and 8-month monitoring points (early February to early March), there was another significant decline in survival at Goulter Bay (9.0 ± 6.8% decline; p = .04) and the first significant, but minor, decline at Nopera (3.2 ± 1.0%; p < .001). From the 8-month monitoring point until the end of the experiment, mussel survival plateaued at each location and both depths with no additional significant declines in survival ( p > .05; Figure 3). Only two eleven-arm sea stars were observed on any plots, one at an intertidal plot in Goulter Bay at the 1-week monitoring and one at an intertidal plot in Double Bay at the 3-month monitoring point. Both sea stars were under 15 cm from arm tip to opposite arm tip.
T A B L E 1 Results of three-way mixed analysis of variance (ANOVA) tests for survival and condition as well as a two-way ANOVA test for shell lengths.

Survival
Shell length Condition

| Air and temperature exposure
The average percent time exposed to air over a full lunar cycle for the intertidal mussel plots was 11.0 ± 1.7% with no significant differences recorded among the three locations ( p > .05). The average temperature recorded on the intertidal mussel plots across all three locations over the 12-month experiment was 17.54 ± 0.01 C with no significant differences in average temperature among the locations (p > .05). However, location did significantly impact exposure to extreme temperatures ( p = .005) which is not reflected in the average temperature as locations that experienced more exposure to extreme hot temperatures (i.e., during daytime in the summer) also experienced more exposure to extreme cold temperatures (i.e., during nighttime in the winter). Specifically, intertidal mussel plots at Double Bay were exposed to more extreme heat (≥40 C) over the course of 12 months (15.4 ± 3.8 h) than mussel plots at both Goulter Bay (3.0 ± 2.1 h; p = .01) or Nopera (0.2 ± 0.15 h; p = .002) which were not different from one another ( p > .05). Additionally, the time exposed to extreme heat since the previous monitoring point had a clear correlation with the mortality that occurred over the same time period with an average increase in mortality of 3.3% for each hour exposed to extreme heat (adjusted-R 2 = .49; p < .001; Figure 5).

| DISCUSSION
To our knowledge, the results of this study are the first scientific evidence of mussel restoration to the intertidal using subtidal source stock to successfully achieve high survival (>75%) over a full 12 months, comparable to levels of survival recorded in successful subtidal mussel restoration (e.g., Benjamin et al., 2023; Benjamin, F I G U R E 4 Mussel condition index (mean ± SE) at each location and depth over the 12-month monitoring period.
F I G U R E 5 Impact of time exposed to extreme heat (>40 C) since the prior monitoring point and change in mussel mortality over that same time period. Each point indicates a single restored intertidal mussel plot at a specific monitoring point, while the dashed line visualizes the linear mixed model with a shaded 95% confidence interval. Fariñas-Franco & Roberts, 2014). Intertidal mussel reefs provide unique ecosystem services (Borthagaray & Carranza, 2007;Keough et al., 1993;Meadows et al., 1998) and are relatively less expensive to restore and monitor than subtidal reefs which require SCUBA divers or vessels (Bayraktarov et al., 2016). However, previous attempts at restoring intertidal mussel reefs have been stymied by high mortality from predation and wave stress (Capelle et al., 2014;Ens & Alting, 1996;. This high mortality is particularly acute when subtidal mussels are used as source stock, leading to suggestions that subtidal mussels are morphologically or physiologically unfit for restoration to the intertidal, despite often being the only available source stock (de Paoli et al., 2015). Contrary to our initial hypothesis, the results of this study reveal that subtidal mussels are not wholly unfit for use in intertidal restoration as subtidal mussel had comparably high survival rates when restored to both the intertidal and subtidal zones at one of the three tested locations (Nopera). Choosing restoration locations carefully to mitigate these stressors (e.g., the low predation and wave action in Kenepuru Sound) can, therefore, result in high survival, even when using subtidal source stock. Notably, the subtidal source stock used for this study were aquaculturegrown mussels which are particularly thin-shelled when compared even to their benthic subtidal counterparts (Hickman, 1979), suggesting high survival should also be achievable using hardier, benthically sourced mussels, in areas where this is a possibility. Additionally, the mussels used in this study were adult mussels, but younger mussels are known to demonstrate more phenotypic plasticity (Schotanus et al., 2019), suggesting they may also serve as a valuable source stock for intertidal restoration.
Despite the high survival recorded at both depths at one location (Nopera), mussels restored intertidally to the other two locations (Goulter Bay and Double Bay) each resulted in lower survival than mussels restored subtidally to the same locations. A stressor other than wave action and predation was likely responsible for this excess mortality, specifically extreme heat during the summer months which closely correlated with the extent and timing of observed intertidal mortality. The results of this study cannot confirm whether the heat-related mortality observed in the intertidally restored mussels was a factor of their subtidal origin as there was no available population of natural intertidal mussels for comparison or reciprocal transplantation. Nevertheless, at temperatures over 40 C even intertidally reared mussels experience increased hormonal perturbations, loss of neural control, and failure of protein synthesis (Dunphy et al., 2015(Dunphy et al., , 2018Zamora et al., 2019). These effects culminate in mass mortality events for wild intertidal mussels when extreme heat waves correspond with low tides (Capelle et al., 2021;Seuront et al., 2019;Tsuchiya, 1983). This problem is exacerbated in a warming global climate that increases the likelihood of extreme heat waves that will directly affect the internal body temperatures of bivalves (Gilman et al., 2006;IPCC, 2022). For example, the summer during this experiment was one of the hottest on record in New Zealand (NIWA, 2022), raising concerns for future intertidal mussel restoration. Despite this record-breaking heat, mussels restored intertidally in Nopera did not experience excess mortality, confirming prior research that heat stress is patchy and small variations in location, substrate, and surrounding topography can have dramatic cooling effects (Harley, 2008;Mislan & Wethey, 2015). For example, the Nopera location tested in this study was located at the base of a large hill, potentially providing additional shade coverage compared to the more open Double Bay and Goulter Bay. Ultimately, these results emphasize the importance of careful site selection for restoration projects and echo previous calls for small-scale trial restoration across a range of locations before full-scale restoration Fitzsimons et al., 2020).
In addition to high survival, the ability of restored populations to reproduce, experience recruitment, and become self-sustaining is a vital measure of restoration success (Gann et al., 2019). Historically, intertidal mussel reefs provided important recruitment refugia in the area as juvenile mussels were most commonly found in intertidal reefs (Stead, 1969). Twelve months is generally too short of a time frame to easily visually observe recruitment of new mussels to either the intertidal or subtidal restored plots; however, no juvenile mussels (<30 mm) were observed during sampling of any of the mussel plots. This is unusual in light of the relatively high larval settlement recorded in the area by the aquaculture industry (Atalah & Forrest, 2019;Toone et al., 2022); however, green-lipped mussel recruitment can be sporadic and years with low or no recruitment have been recorded (Alfaro, 2006;Alfaro et al., 2011). Ultimately the success of restoration efforts relies on natural recruitment for the maintenance and expansion of restored reefs (Fitzsimons et al., 2020); therefore, future efforts should prioritize recruitment monitoring before any long-term declaration of success. Nevertheless, condition index can be used as a proxy for the reproductive status of mussels as it generally increases seasonally before spawning (Dawber, 2004). The decline in condition index across all locations and depths in this study was expected as the mussels acclimated to life on the seabed rather than suspended on aquaculture ropes in the water column as cultured mussels typically have a higher condition index than wild mussels (Hickman & Illingworth, 1980). However, the more extreme decline in condition of mussels restored to the intertidal compared to their subtidal counterparts, in addition to their reduced growth rate of mussels, suggests that mussels restored to the intertidal may be at greater risk of reduced reproductive output than mussels restored to the subtidal, particularly if the trend continues. Future intertidal mussel restoration efforts should closely monitor spawning and recruitment over a longer timespan to ensure the self-sustainability of restored reefs.
Translocations of species can be vital to effectively restore degraded ecosystems, but they come with inherent risks as organisms from a successful population may not acclimate to a new environment (Gann et al., 2019). The knowledge of which source populations can successfully undergo translocations to target areas is essential for restoration managers, particularly if potential source populations from the same environmental conditions are limited, as is the case for intertidal mussel restoration. This study demonstrates that not only is it possible to restore mussels to the intertidal and achieve high survival, but that mussels grown in the subtidal, such as widely available cultured mussels, can be used as a source population so long as care is taken to avoid certain stressors like predation, wave action, and heat. Ultimately, to reach the goals set by the UN Decade on Ecosystem Restoration (UN Resolution 73/284), restoration practitioners cannot afford to reject potential source populations because of phenotypic differences alone and should instead think broadly about potential source populations and trial creative solutions to combat global ecosystem decline.