Predatory Sea Stars Research Articles

Selective Feeding by a Predatory Sea Star Across a Depth Gradient in Northern Patagonia, Chile

Sea stars often function as keystone predators in food webs of intertidal and subtidal communities, especially in temperate and sub-polar regions. In South America the sea starCosmasterias luridais distributed along both the Atlantic and Pacific coasts of Patagonia and is one of the most conspicuous and abundant benthic predators in the shallow subtidal zone (<25 m). Its feeding strategy and prey selection are, however, still poorly known. This study describes the feeding behavior ofC. luridaat a site in the Seno del Reloncaví (Chile), assessing its abundance, size and prey selection in the field relative to observed prey abundance and size along a bathymetric gradient. We hypothesized thatC. luridais a generalist predator, feeding on suitable prey according to their availability. However, we found that this predator only consumed a limited number (7 of 48) of potential prey species, primarily the slipper limpetsCrepipatellaspp. and the musselsAulacomya aterandMytilus chilensis. Electivity analysis revealed a clear preference for one mussel (A. ater) but not the other (M. chilensis) as well as depth-dependent selectivity for the slipper limpets, which changed from avoidance to preference with increasing depth. Sea star densities varied with depth, peaking between depths of 5 and 10 m, but the size of sea stars and the size of their prey did not vary significantly along a depth gradient. No significant correlations were found with the most commonly selected prey. These results would indicate that while this predator may be a generalist–opportunist, its feeding behavior is context-dependent and its high selectivity for certain species suggests that this sea star plays a key role structuring subtidal benthic communities in Patagonia.

“Urchin pinning”: Behavioural observations reveal how hungry urchins actively prey upon their sea star predators

AbstractGreen sea urchins (Strongylocentrotus droebachiensis) are dominant components of benthic ecosystems that form aggregations and can transform entire kelp forests into barren systems. While these urchins are known to unwittingly consume practically anything in their path while grazing, detailed descriptions of active predatory behaviour on known predators (i.e., predator–prey reversal) are undocumented. Here, we use laboratory observations to describe the behavioural tactics used by starved S. droebachiesis to actively attack and consume sea stars, Crossaster papposus—a known predator of S. droebachiensis. We observed urchins preying on three separate sea stars, with one being substantially consumed by urchins within 24 hr. Urchins exhibited a direct mode of attack on sea stars by individually mounting and consuming the tips of the arms. Interestingly, we did not observe any conflict between individual urchins for attacking the sea star despite there being ≈80 starving urchins in the tank (and only 10–12 arms on the sea stars). Some sea stars did not attempt to escape urchin predation at all, while others attempted to escape by fleeing and lifting arms on top of the urchins. Given that sensory perception in sea stars is largely derived from the arm tips, we suggest that urchins directly attack and consume many sea star arm tips in an attempt to “pin” sea stars before consuming them. As such, we term this predatory behaviour “urchin pinning.” These observations ultimately provide the first detailed behavioural documentation of how urchins actively prey on a known predator and provide a basis for a wealth of future research.

Getting Out of Arms' Way: Star Wars and Snails on the Seashore.

AbstractMany shell-bearing gastropods exhibit pre-capture behaviors when encountering predatory asteroid sea stars. As shown in this meta-analysis of 48 studies on 24 sea star and 100 gastropod and chiton species, almost three-quarters of prey escape by moving or tumbling away, whereas the remaining species clamp tightly to the substratum or otherwise resist. The aim of the present paper is to correlate these behaviors with predicted shell traits, including those with gravitational stability for species that escape on the substratum and those that clamp, and those with a strongly sculptured shell in species that resist sea star attacks. Escaping species and those that clamp have gravitationally stable shells, with the center of gravity located above the broad aperture and large foot. Species that resist have significantly more sculptured shells. All of these traits would also work well in encounters with other slow-moving predators, such as gastropods and planarians. Although the sea stars are generalist predators, and the gastropods have many enemies besides sea stars, cool-water gastropods are well adapted to predatory sea stars on temperate and polar coasts, where most hard-bottom sea stars with molluscan diets occur. The prominence of escape among cool-water gastropods seems contradictory, given that locomotor speed rises with increasing temperature; but tropical gastropods rely more on armor than on escape, because of the prevalence of faster, more powerful predators in warm water. The black pigment of shells of many temperate prey species of sea stars might confer crypsis against these predators.

Blue mussel (Mytilus edulis L.) association with conspecifics affects mussel size selection by the common seastar (Asterias rubens L.)

Prey selection by predators is of interest to community ecologists. By choosing some prey over others, predators affect prey population dynamics and the strength of food webs. According to Optimal Diet Theory (ODT), as prey density increases predators will select more profitable prey. Thereby, prey population dynamics can also affect predator behaviour. Prey profitability involves the prey energetic value, energetic costs associated to predation (time spent searching, capturing and handling prey) and certain characteristics such as body size, abundance and behaviour. We examined the effect of the blue mussel (Mytilus edulis) association with conspecifics at different densities on prey selection and behaviour by the seastar Asterias rubens. Contrary to ODT prediction, when mussels were tightly clumped in high densities, the size range of the mussels consumed by A. rubens did not differ of the size range of the mussel population. Mussel association at high density caused seastars to feed locally, reducing their exposition to risks. Moreover, preying without selecting for a specific mussel size did not result in a decrease of net profit, rather it was increased. We concluded that under certain circumstances, not selecting prey results in an increase of net profit at prey size.We discuss our results in the context of the mussel industry where the effect of prey selection on the prey population dynamics is of importance. Mussel size selection by seastars, as described in previous works, will impact the size distribution of mussels within cultured populations affecting growth of the population and reproductive output among others, thus increasing the impact of seastar predation beyond that of just removing mussels from the population. However, this study shows that seastars prey upon availability at high densities, typically encountered in cultivated populations, and therefore their effect on mussel population is restricted to removal of mussels without affecting the size distribution of the population.

Trophic redundancy and predator size class structure drive differences in kelp forest ecosystem dynamics.

Ecosystems are changing at alarming rates because of climate change and a wide variety of other anthropogenic stressors. These stressors have the potential to cause phase shifts to less productive ecosystems. A major challenge for ecologists is to identify ecosystem attributes that enhance resilience and can buffer systems from shifts to less desirable alternative states. In this study, we used the Northern Channel Islands, California, as a model kelp forest ecosystem that had been perturbed from the loss of an important sea star predator due to a sea star wasting disease. To determine the mechanisms that prevent phase shifts from productive kelp forests to less productive urchin barrens, we compared pre‐ and postdisease predator assemblages as predictors of purple urchin densities. We found that prior to the onset of the disease outbreak, the sunflower sea star exerted strong predation pressures and was able to suppress purple urchin populations effectively. After the disease outbreak, which functionally extirpated the sunflower star, we found that the ecosystem response—urchin and algal abundances—depended on the abundance and/or size of remaining predator species. Inside Marine Protected Areas (MPAs), the large numbers and sizes of other urchin predators suppressed purple urchin populations resulting in kelp and understory algal growth. Outside of the MPAs, where these alternative urchin predators are fished, less abundant, and smaller, urchin populations grew dramatically in the absence of sunflower stars resulting in less kelp at these locations. Our results demonstrate that protected trophic redundancy inside MPAs creates a net of stability that could limit kelp forest ecosystem phase shifts to less desirable, alternative states when perturbed. This highlights the importance of harboring diversity and managing predator guilds.

Predator identity dominates non-consumptive effects in a disease-impacted rocky shore food web.

Predicting the effects of predator diversity loss on food webs is challenging, because predators can both consume and induce behavioral responses in their prey (i.e., non-consumptive effects or NCEs). Studies manipulating predator diversity and investigating NCEs are rare, especially in marine systems. Recently, a severe outbreak of sea star wasting syndrome (SSWS) on the west coast of North America resulted in unprecedented declines of the sea star Pisaster ochraceus. We investigated the consequences of Pisaster loss on an abundant grazer, the black turban snail Tegula funebralis, through NCEs. We combined a laboratory experiment and field surveys to examine the importance of identity vs. diversity in a predator assemblage (Pisaster, crabs, and octopuses) on Tegula behavior, feeding, and growth. Laboratory and field results indicated that predator identity, not diversity, drives Tegula behavior and causes NCEs. Mesocosm treatments with Pisaster caused greater NCEs on Tegula than assemblages without Pisaster. Tegula's distribution in the field, which is driven primarily by anti-predator behavior, was strongly associated only with Pisaster abundance, and not with the abundance of crabs, octopuses, and other predatory sea stars (Leptasterias spp.). We conclude that Pisaster primarily drives Tegula vertical distribution and may be having strong NCEs on Tegula on northern California rocky shores. Furthermore, predator diversity in northern California does not provide functional redundancy, in terms of NCEs on Tegula, to buffer the system from Pisaster loss. Thus, predator-induced vertical distributions and grazing suppression may not be maintained in areas where Pisaster populations are reduced or slow to recover from SSWS.

Contrasting chemotactic escape responses of the common Antarctic gastropod Margarella antarctica to four species of sympatric sea stars

Escape responses of marine gastropods from sea star predators have long been established in laboratory studies. The degree of the response, which may include shell elevation and rotation and/or rapid flight, can vary with sea star taxa, providing insights into the degree to which a particular sea star species represents an in situ predatory threat. Little is known of such predator-prey interactions among benthic macroinvertebrates along the western Antarctic Peninsula. The present laboratory study employed video analysis to measure chemotactic escape responses (mean speed of flight following contact with the tip of a sea star's arm) in the common Antarctic top shell snail Margarella antarctica to the sea stars Neosmilaster georgianus, Remaster sp., Granaster nutrex, and Odontaster validus. Identical assays in response to contact with the thalli of the macroalga Gigartina skottsbergii provided a control. Significant flight responses to contact with two of the four sea star taxa were detected [N. georgianus (6.2 cm min−1), Remaster spp. (4.4 cm min−1)]. There was no significant difference between gastropod speed in response to contact with the control macroalga (1.9 cm min−1) and to the sea stars G. nutrex (3.1 cm min−1) and O. validus (1.1 cm min−1). Measured patterns of sea star-induced gastropod flight responses are discussed in the context of natural diets and feeding modes of the sea stars.

Shifts in seawater chemistry disrupt trophic links within a simple shoreline food web.

Marine intertidal systems have long served as focal environments for ecological research, yet these environments are changing due to the entry of human-produced carbon dioxide into seawater, which causes 'ocean acidification' (OA). One component of OA is a decline in seawater pH, an alteration known to disrupt organism behaviors underlying predator-prey interactions. To date, however, studies examining OA's effects on feeding relationships consider predominantly simple direct interactions between consumers and their food sources. Here, we extended these established approaches to test how decreased seawater pH might alter cascading effects that span tiered linkages in trophic networks. We employed a model shoreline food web incorporating a sea star predator (Leptasterias hexactis), an herbivorous snail prey (Tegula funebralis), and a common macroalgal resource for the prey (Mazzaella flaccida). Results demonstrate direct negative effects of low pH on anti-predator behavior of snails, but also weakened indirect interactions, driven by increased snail consumption of macroalgae even as sea stars ate more snails. This latter outcome arose because low pH induced 'foolhardy' behaviors in snails, whereby their flight responses were supplanted by other activities that allowed for foraging. These findings highlight the potential for human-induced changes in seawater chemistry to perturb prey behaviors and trophic dynamics with accompanying community-level consequences.

Impacts of gastropods on epiphytic microalgae on the brown macroalga Himantothallus grandifolius

AbstractChemically defended benthic macroalgae that dominate shallow, hard bottom communities along the western Antarctic Peninsula support very high densities of mesograzers, particularly amphipods but also small gastropods. Previous studies have demonstrated that the macroalgae and amphipods form a mutualistic relationship. The chemically defended macroalgae provide the amphipods with a refuge from predation while the macroalgae benefit from the amphipods greatly reducing surface fouling by smaller algae. One of the three most important macroalgae in terms of overstory cover, Himantothallus grandifolius, forms huge blades that can carpet the benthos. Field observations suggest that gastropods may be higher in relative abundance in proportion to amphipods on H. grandifolius than on other overstory macroalgae. The present study documents the finding that natural abundances of gastropods on H. grandifolius maintained in mesocosms reduce fouling by microscopic algae, primarily diatoms. However, amphipods are probably also important in keeping the macroalga clean of diatoms in nature. In a smaller scale experiment, three gastropod species were differentially effective at reducing diatom coverage on H. grandifolius. The hypothesis that gastropods benefit from associating with H. grandifolius in potentially gaining a refuge from sea-star predation was also tested but not supported by the experimental results.

Similarity in predator-specific anti-predator behavior in ecologically distinct limpet species, Scurria viridula (Lottiidae) and Fissurella latimarginata (Fissurellidae)

Many marine gastropods show species-specific behavioral responses to different predators, but less is known about the mechanisms influencing differences or similarities in specific responses. Herein, we examined whether two limpet species, Scurria viridula (Lamarck, 1819) and Fissurella latimarginata (Sowerby, 1835), show species- and size-specific similarities or differences in their reaction to predatory seastars and crabs. Both S. viridula and F. latimarginata reacted to their main seastar predators with escape responses. In contrast, both limpets did not flee from common crab predators, but, instead, fastened to the rock. All tested size classes of both limpet species reacted in a similar way, escaping from seastars, but clamping onto the rock in response to crabs. Limpets could reach velocities sufficient to outrun their specific seastar predators, but they were not fast enough to escape crabs. Experiments with limpets of different shell conditions (with and without shell damage) indicated that F. latimarginata with a damaged shell showed “accommodation movements” (slow movements away from stimulus) in response to predatory crabs. In contrast, intact F. latimarginata and all S. viridula (intact and damaged) clamped the shell down to the substratum. The response details suggest that the keyhole limpet F. latimarginata is more sensitive to predators (faster reaction time, longer escape distances, and higher proportion of reacting individuals) than S. viridula, possibly because the morphology of F. latimarginata (the relationship of its shell size and structure to its total body size) makes this species more vulnerable to predation. Our study suggests that chemically mediated effects of seastar and crab predators result in contrasting behavioral responses of both limpet species, independent of their habitat and morphology. Despite the different characteristics of the limpet species and the identity of predators, the limpets react in comparable ways to similar predator types.

Trait-mediated indirect effects in a natural tidepool system

We demonstrate an apparent trait-mediated indirect interaction (TMII) of predators on primary producers in a natural community by altering prey behavior over short and long time scales. Small predatory sea stars (Leptasterias spp.) caused herbivorous snails (Tegula funebralis) added to rocky intertidal tidepools to quickly flee into refuge microhabitats outside tidepools within days, and this was associated with a 58% increase in microalgal growth after 2 weeks. Similarly, removing sea stars caused snails to increase use of tidepools for 1–10 months. After adding sea stars to tidepools, snails quickly fled and then consistently increased use of refuges outside tidepools for 10 months. This was associated with average increases of 59% for microalgal growth over 1 month and 254% for macroalgal growth over 8 months inside tidepools. In 63 unmanipulated tidepools, densities of sea stars and snails were negatively correlated. High densities of snails were associated with unpalatable algal species and bare rock, while high densities of sea stars were associated with palatable algal species, suggesting that this apparent TMII may have community-level impacts. Though multiple lines of evidence suggest TMIIs were likely operating in this system, it was not possible to experimentally partition the relative contributions of TMIIs and density-mediated indirect interactions (DMIIs), so further caging experiments are necessary to distinguish their relative strengths. Overall, we suggest that predators can benefit primary producers by changing prey behavior even when predators and prey are unrestrained by cages or mesocosms, embedded in complex communities, and observed over multiple time scales.

Index to Volume 235

Index to Volume 235

Lamellose Axial Shell Sculpture Reduces Gastropod Vulnerability to Sea Star Predation.

Marine gastropods exhibit a stunning diversity of shell sculpture, but the functional significance of many sculpture types remains unknown. Unfortunately, experimental tests of the functional significance of differences between species are complicated by other morphological differences, such as shell microstructure, aperture shape, and shell thickness, that may confound interpretation. The most robust experimental tests are therefore performed using different shell forms within a species. We took advantage of the extensive intraspecific shell variation in the common intertidal gastropod Nucella lamellosa to test the adaptive significance of axial lamellae, a type of shell sculpture found in numerous marine gastropod subfamilies. We offered three forms of N. lamellosa (lamellose, artificially smooth, and naturally smooth) to the predatory sea star Pisaster ochraceus under controlled laboratory conditions. Pisaster ochraceus consumed significantly fewer lamellose snails than either artificially or naturally smooth snails. We suggest that shell lamellae deter sea star predation by impairing their ability to capture or manipulate snail prey or by increasing prey effective size. These results suggest a credible hypothesis for the adaptive significance of lamellar sculpture in marine gastropods and provide a valuable missing piece to the story about adaptive phenotypic plasticity in N. lamellosa shell form.

Impacts of sea star predation on mussel bed restoration

Predation by sea stars has the potential to cause elevated levels of mortality in reestablished populations of bivalves relative to levels of recruitment. Recent efforts to restore beds of the nearly extirpated green‐lipped mussel within the Hauraki Gulf, New Zealand, resulted in high abundances of sea stars occupying those beds and it is unknown whether predation poses a potential limitation to the success of restoration in this bivalve species. The contribution of predation by sea stars to the mortality of mussels across four experimental mussel beds over a 2‐year period was estimated using data from regular assessments of sea star abundance and an experimentally determined consumption rate of sea stars upon mussels. In addition, the potential size selection of mussels by sea stars was assessed to determine if large sea stars selected for recent settlers. Sea stars' abundance within the mussel beds grew to an average of 0.57 sea stars/m2 within 9 months, remaining at similar levels throughout the study. These predominantly large sea stars were estimated to have consumed 30.1% of the mussels over a 25‐month period, representing a contribution of 40.4% of the mussel mortality. Sea stars predominantly selected for larger mussels, and their predation likely contributes little to any lack in mussel recruitment. Sea star predation is clearly a limiting factor on the survival of transplanted adult mussels and the present study highlights the need to continually assess predation risk to determine if remediation is necessary for the persistence of the restored beds.

Predation on competing mussel species: Patterns of prey consumption and its potential role in species coexistence

Theoretical and empirical studies have demonstrated that predators can modulate coexistence between prey species and can modify broad patterns of community structure. Although the keystone predator effect (i.e., local coexistence and species diversity mediated by predator consumption) is commonly reported, negative effects of predators on species coexistence are also common. The balance depends critically on the asymmetry of competition, predator preferences for different prey, and the effective mortality rates exerted by predator populations on prey per capita growth rates. Here we studied the role of predation on two competing mussels, the dominant competitor Perumytilus purpuratus that dominates in abundance at most shores, and the subordinate Semimytilus algosus, which is common, but persistently abundant only at a smaller set of shores. We examined the potential for keystone effects by quantifying and evaluating the patterns of mussel consumption rates of sea star (Heliaster helianthus) and crab (Acanthocyclus gayi) predators in laboratory experiments, and under natural field conditions. Field sites with contrasting mussel abundance and recruitment (i.e., different local prey population growth rates) were chosen. Laboratory experiments showed that crabs would first consume Semimytilus over Perumytilus in mixed mussel clumps, while the larger sea star predators made no distinction between mussel species. Regardless of the order in which mussel species were first ingested, consumption rates of the two mussel species through the experiment were not different for either predator species. A similar temporal pattern was partly observable in the field through specific differences in the order of mussel consumption; however, experimental mussels of both species where consumed after the first two months of exposure to predators at both sites. Thus, in this system predation could not foster coexistence between mussel species and it may instead favor the occurrence of local extinction of the subordinate competitor, especially at sites where the smaller and more selective crab predators are relatively more abundant and recruitment of the subordinate species is low. Existing patterns of locally abundant Semimytilus beds are probably related to high site-specific recruitment rates of this species and should be further explored.

Discriminating Eaters: Sea Stars Asterias rubens L. Feed Preferably on Mytilus trossulus Gould in Mixed Stocks of Mytilus trossulus and Mytilus edulis L.

Sea stars Asterias rubens are important natural enemies of the blue mussel Mytilus in the North Atlantic. We asked whether these predators distinguish between the cryptic species M. edulis and M. trossulus that occur sympatrically in the White Sea. In mixed experimental stocks, the odds of being eaten by sea stars were about four times greater for M. trossulus. We also showed that A. rubens preferred smaller mussels to larger ones, irrespective of their species affinity. Our findings support earlier indirect observations showing that sea stars recognize M. trossulus as a more preferable prey than M. edulis. Dramatic differences in the vulnerability to sea star predation may explain the segregation of habitats between the two mussel species in contact zones; M. trossulus usually tends to occupy habitats where the sea star predators are scarce.

Ecological restoration of mussel beds onto soft‐sediment using transplanted adults

The success of restoration initiatives to restore bivalve beds relies on sufficient recruitment of larvae to offset mortality of re‐established populations. Individuals of the nearly extirpated green‐lipped mussel are capable of surviving within the current environment of the Hauraki Gulf, New Zealand; however, it is uncertain what potential factors might inhibit the establishment and persistence of restored mussel beds. Four experimental mussel beds were established within a shallow soft‐sediment embayment and assessments of population dynamics were conducted approximately every 6 months over a 2‐year period. Deployed mussels quickly congregated into contiguous mussel beds that persisted throughout the study; however, only 26.2% of mussels that were initially established survived until the end of the study. The cause of this overall loss of mussels can be attributed to a near lack of observed recruitment, with only three individual recruiting mussels observed throughout the entire study. Despite similar mortality rates within the restored mussel beds to that of natural populations, these populations will be unsustainable long term given the lack of recruitment. Potential causes of the observed mortality and lack of recruitment are discussed, including environmental factors affecting non‐natal mussel stock and sea star predation. This research provides a foundation for the development of best‐practice methods in the restoration of green‐lipped mussels. However, further investigation into recruitment pathways and sources of mortality for adult mussels will be necessary to overcome the observed limitations if future restoration is to be successful.

Antibacterial defenses and palatability of shallow-water Antarctic sponges

Marine sponges are exposed to predation as well as to a wide array of potentially harmful microorganisms, and therefore they often possess chemical activity against putative predators and/or pathogens. Some crude extracts from sponges are effective in avoiding microbial colonization or potential infections, and in protecting them against predation. Here, the antibacterial activity of 18 sponge species of Antarctic shallow-waters was tested against four Antarctic and four human pathogenic bacteria. Moreover, all sponge extracts were tested for feeding repellence against the seastar Odontaster validus, one of the main predators living in those habitats. All the sponges showed antibacterial activity against at least one bacterial isolate, although not all of them were active against pathogenic bacteria. The antibacterial effect against sympatric bacteria was stronger than to pathogenic bacteria. In contrast, feeding deterrence was low, with similar activities in both hydrophilic and lipophilic extracts. Only four sponges (Myxilla lyssostyla, Phorbas areolatus, Polymastia invaginata and Iophon sp.), presented repellent chemical defenses. Therefore, we conclude that chemical defenses are widespread in Antarctic shallow-water sponges, and in fact, these sponges are better protected against bacteria than against the seastar predator. We conclude that Antarctic sponges represent a valuable source of biological active compounds with pharmacological and potential ecological relevance.

Feeding in deep-sea demosponges: Influence of abiotic and biotic factors

In shallow benthic communities, sponges are widely recognized for their ability to contribute to food webs by cycling nutrients and mediating carbon fluxes through filter feeding. In comparison, little is known about filter feeding in deep-sea species and how it may be modulated by environmental conditions. Here, a rare opportunity to maintain live healthy deep-sea sponges for an extended period led to a preliminary experimental study of their feeding metrics. This work focused on demosponges collected from the continental slope of eastern Canada at ~ 1000m depth. Filtration rates (as clearance of phytoplankton cells) at holding temperature (6°C) were positively correlated with food particle concentration, ranging on average from 18.8 to 160.6 cells ml−1h−1 at nominal concentrations of 10,000–40,000 cells ml−1. Cell clearance was not significantly affected by decreasing seawater temperature, from 6°C to 3°C or 0°C, although two of the sponges showed decreased filtration rates. Low pH (~ 7.5) and the presence of a predatory sea star markedly depressed or inhibited feeding activity in all sponges tested. While performed under laboratory conditions on a limited number of specimens, this work highlights the possible sensitivity of deep-sea demosponges to various types and levels of biotic and abiotic factors, inferring a consequent vulnerability to natural and anthropogenic disturbances.

Is attachment substrate a prerequisite for mussels to establish on soft-sediment substrate?

It is unknown whether the presence of hard substrate is a necessary prerequisite for the attachment and establishment of mussels, especially on soft-sediment habitats where hard substrates are scarce. Therefore, we examined the importance of natural attachment substrates in the form of mussel shell and adult conspecifics for the establishment of juvenile and adult green-lipped mussels (Perna canaliculus) on soft-sediment. In field experiments where shell material was added as substrate to soft-sediment it made no difference to the subsequent retention of adult mussels. Laboratory experiments showed that juvenile mussels preferentially sought out, and attached to adult mussels compared to remaining on unmodified soft-sediment. Furthermore, juvenile mussels attached to live adult mussels had higher survival in the presence of a common sea star predator compared to juveniles on unmodified soft-sediment or attached to mussel shell. The results suggest that establishment of mussel beds on soft-sediment requires only adult mussels, which receive sufficient anchorage through attachment to neighbouring adults and in so doing, providing a stable, complex substrate suitable for improving the survival of establishing juvenile mussels by protecting them from sea star predators.