Across-Shelf Transport of Bivalve Larvae: Can the Interface between a Coastal Current and Inshore Waters Act as an Ecological Barrier to Larval Dispersal?

Using an integrated physical and biological approach, we examined across-shelf advection and exchange and the associated transport of bivalve larvae in the presence of a strong coastal current separated from the coast by a stratified inshore environment. We tested the hypothesis that the interface of the coastal current and inshore waters can act as an ecological barrier to across-shelf transport of larvae but can be overcome by wind- or tidally-induced transport. Our study region in the Gulf of Maine encompasses a coastal current that diverges from the coast as it moves downshelf. The region inshore of this current is home to several species that exhibit limited recruitment in spite of extensive upshelf larval sources. Analysis of surface water temperatures and wind velocities revealed episodic decreases in temperature along the coast correlated with alongshelf (but not upwelling) winds, indicating wind-forced onshore movement of the cold coastal current. Such wind-driven onshore migrations are more common along the northern portion of the study region where the coastal current is near the coast, tidal currents are strong, and wind directions are more conducive to onshore migration, but rarer further south where the interface between inshore waters and the coastal current is further offshore and suitable wind events are less common. The distribution of bivalve larvae was consistent with the physical measurements. There was little across-shelf variation in larval abundance where the current abuts the coast, indicating strong across-shelf exchange of larvae, but strong across-shelf variation in larval density where the stratified inshore waters separate the current from the coast, indicating weak across-shelf transport of larvae. Our results suggest that the interface between the coastal current and inshore waters may constitute a major ecological barrier to larval dispersal in the southern part of the region that may only be overcome by rare, strong wind-forced events.     

Recruitment constraints in Singapore's fluted giant clam (Tridacna squamosa) population—A dispersal model approach

Recruitment constraints on Singapore''s dwindling fluted giant clam, Tridacna squamosa, population were studied by modelling fertilisation, larval transport, and settlement using real-time hydrodynamic forcing combined with knowledge of spawning characteristics, larval development, behaviour, and settlement cues. Larval transport was simulated using a finite-volume advection-diffusion model coupled to a three-dimensional hydrodynamic model. Three recruitment constraint hypotheses were tested: 1) there is limited connectivity between Singapore''s reefs and other reefs in the region, 2) there is limited exchange within Singapore''s Southern Islands, and 3) there exist low-density constraints to fertilisation efficacy (component Allee effects). Results showed that connectivity among giant clam populations was primarily determined by residual hydrodynamic flows and spawning time, with greatest chances of successful settlement occurring when spawning and subsequent larval dispersal coincided with the period of lowest residual flow. Simulations suggested poor larval transport from reefs located along the Peninsular Malaysia to Singapore, probably due to strong surface currents between the Andaman Sea and South China Sea combined with a major land barrier disrupting larval movement among reefs. The model, however, predicted offshore coral reefs to the southeast of Singapore (Bintan and Batam) may represent a significant source of larvae. Larval exchange within Singapore''s Southern Islands varied substantially depending on the locations of source and sink reefs as well as spawning time; but all simulations resulted in low settler densities (2.1–68.6 settled individuals per 10,000 m²). Poor fertilisation rates predicted by the model indicate that the low density and scattered distribution of the remaining T. squamosa in Singapore are likely to significantly inhibit any natural recovery of local stocks.     

Observations on the distribution of meroplankton during an upwelling event

The distribution of the larvae of benthic invertebrates wasinvestigated relative to hydrographic structures as a test ofthe hypothesis that larvae behave as if they are passive particles.Observations of larval and oceanographic distributions weremade off Duck, North Carolina, USA in August 1994. Conditionswere characterized by wind-driven coastal upwelling; flow wasgenerally offshore near the surface and onshore below the pycnocline.Within 5 km of the shore the pycnocline was bent upward by theupwelling and it intersected the surface along most of the transects.In zooplankton samples, 20 taxa of larvae were counted (10 bivalveveligers, nine gastropod veligers and one polychaete larvae).Using cluster analysis, larvae were separated into groups withsimilar patterns of distribution and similar affinities to waterproperties. The larvae in Cluster 3 did not display a consistentdistribution pattern beyond that they tended to be found inwarmer surface waters. An earlier paper described the distributionof larvae in the same location during a downwelling event [A.Shanks et al. (2002) J. Plankton Res., 24, 391–416]. Twoof the clusters identified during this previous study were quitesimilar in composition to Clusters 1 and 2 in this study. Inboth studies, Cluster 1 larvae were found below the pycnocline,but during the upwelling event they were transported shorewardwith the advection of the subpycnocline waters by the upwellingcirculation. Within 5 km of the shore, Cluster 1 larvae werefound at depths shallower than the base of the pycnocline andwere often found in patches of high larval concentration. Thepatches were located where the waters were upwelling. Cluster2 larvae were found within 5 km of the shore in both studiesand tended to be highly concentrated in convergences or divergences.Larvae in Cluster 1 generally appeared to be dispersing as passiveparticles, except within the zone of upwelling where they mayhave been swimming against the upwelling flow leading to higherlarval concentrations. Cluster 2 larvae appeared to be consistentlyconcentrated in areas of vertical currents, suggesting thatthey may be attempting to maintain a preferred depth in theface of the vertical flow which would lead to high larval concentrationand nearshore larval distributions despite extensive cross-shelfmovement of water. Despite their slow swimming speeds, the larvaein Clusters 1 and 2 were not swept offshore by the upwellingevent.     

The surf zone: a semi-permeable barrier to onshore recruitment of invertebrate larvae?

The supply of larvae to the shore is important for population replenishment and intertidal community dynamics but its variability at most scales is not well understood. We tested the relationship between nearshore mussel larval abundance and intertidal settlement rates over several years at multiple spatiotemporal scales in Oregon and New Zealand. Abundance of competent larvae nearshore and intertidal recruitment rates were simultaneously quantified using collectors mounted at different depths on moorings 50-1100 m from shore, and at adjacent rocky intertidal sites. Total mussel larval abundance and oceanographic conditions were also measured in some locations. At all scales, abundance of nearshore mussel larvae was unrelated to intertidal recruitment rates. In the intertidal, patterns of mussel recruitment were persistent in space, with sites of consistently high or low recruitment. In contrast, nearshore competent larval abundance showed generally similar abundances among sites except for a high, and spatially-inconsistent, variability in Oregon during 1998 only. On moorings, recruitment tended to be greater on midwater collectors than shallower or deeper. Finally, on moorings larval abundance in traps and recruitment on collectors was unrelated. These results suggest that (1) among sites, the size of the nearshore larval pool is relatively uniform while onshore recruitment varies and is unrelated to larval abundance, (2) temporal variability in nearshore larval availability is not strongly expressed onshore, (3) vertical stratification of competent larvae nearshore is strong and may influence transport and recruitment, and (4) within-coast variability in onshore recruitment is strongly driven by processes occurring locally within the surf zone that need to be studied to understand coastal recruitment dynamics.     

Role of Upwelling on Larval Dispersal and Productivity of Gooseneck Barnacle Populations in the Cantabrian Sea: Management Implications

The effect of coastal upwelling on the recruitment and connectivity of coastal marine populations has rarely been characterized to a level of detail to be included into sound fishery management strategies. The gooseneck barnacle (Pollicipes pollicipes) fishery at the Cantabrian Coast (Northern Spain) is located at the fringes of the NW Spanish Upwelling system. This fishery is being co-managed through a fine-scale, interspersed set of protected rocks where each rock receives a distinct level of protection. Such interspersion is potentially beneficial, but the extent to which such spacing is consistent with mean larval dispersal distances is as yet unknown. We have simulated the spread of gooseneck barnacle larvae in the Central Cantabrian Coast using a high-resolution time-series of current profiles measured at a nearshore location. During a year of high upwelling activity (2009), theoretical recruitment success was 94% with peak recruitment predicted 56 km west of the emission point. However, for a year of low upwelling activity (2011) theoretical recruitment success dropped to 15.4% and peak recruitment was expected 13 km east of the emission point. This is consistent with a positive correlation between catch rates and the Integrated Upwelling Index, using a 4-year lag to allow recruits to reach commercial size. Furthermore, a net long-term westward larval transport was estimated by means of mitochondrial cytochrome c oxidase subunit I (COI) sequences for five populations in the Cantabrian Sea. Our results call into question the role of long distance dispersal, driven by the mesoscale processes in the area, in gooseneck barnacle populations and point to the prevalent role of small-scale, asymmetric connectivity more consistent with the typical scale of the co-management process in this fishery.     

The Effects of Anthropogenic Structures on Habitat Connectivity and the Potential Spread of Non-Native Invertebrate Species in the Offshore Environment

Offshore structures provide habitat that could facilitate species range expansions and the introduction of non-native species into new geographic areas. Surveys of assemblages of seven offshore oil and gas platforms in the Santa Barbara Channel revealed a change in distribution of the non-native sessile invertebrate Watersipora subtorquata, a bryozoan with a planktonic larval duration (PLD) of 24 hours or less, from one platform in 2001 to four platforms in 2013. We use a three-dimensional biophysical model to assess whether larval dispersal via currents from harbors to platforms and among platforms is a plausible mechanism to explain the change in distribution of Watersipora and to predict potential spread to other platforms in the future. Hull fouling is another possible mechanism to explain the change in distribution of Watersipora. We find that larval dispersal via currents could account for the increase in distribution of Watersipora from one to four platforms and that Watersipora is unlikely to spread from these four platforms to additional platforms through larval dispersal. Our results also suggest that larvae with PLDs of 24 hours or less released from offshore platforms can attain much greater dispersal distances than larvae with PLDs of 24 hours or less released from nearshore habitat. We hypothesize that the enhanced dispersal distance of larvae released from offshore platforms is driven by a combination of the offshore hydrodynamic environment, larval behavior, and larval release above the seafloor.     

The Role of Hydrodynamic Processes on Anchovy Eggs and Larvae Distribution in the Sicily Channel (Mediterranean Sea): A Case Study for the 2004 Data Set

Knowledge of the link between ocean hydrodynamics and distribution of small pelagic fish species is fundamental for the sustainable management of fishery resources. Both commercial and scientific communities are indeed seeking to provide services that could “connect the dots” among in situ and remote observations, numerical ocean modelling, and fisheries. In the Mediterranean Sea and, in particular, in the Sicily Channel the reproductive strategy of the European Anchovy (Engraulis encrasicolus) is strongly influenced by the oceanographic patterns, which are often visible in sea surface temperature satellite data. Based on these experimental evidences, we propose here a more general approach where the role of ocean currents, wind effects, and mesoscale activity are tied together. To investigate how these features affect anchovy larvae distribution, we pair ichthyoplankton observations to a wide remote sensing data set, and to Lagrangian numerical simulations for larval transport. Our analysis shows that while the wind-induced coastal current is able to transport anchovy larvae from spawning areas to the recruiting area off the Sicilian south-eastern tip, significant cross-shore transport due to the combination of strong northwesterly mistral winds and topographic effects delivers larvae away from the coastal conveyor belt. We then use a potential vorticity approach to describe the occurrence of larvae cross-shore transport. We conclude that monitoring and quantifying the upwelling on the southern Sicilian coast during the spawning season allows to estimate the cross-shore transport of larvae and the consequent decrease of individuals within the recruiting area.     

Characteristics of the Norwegian Coastal Current during Years with High Recruitment of Norwegian Spring Spawning Herring (Clupea harengus L.)

Norwegian Spring Spawning herring (NSSH) Clupea harengus L. spawn on coastal banks along the west coast of Norway. The larvae are generally transported northward in the Norwegian Coastal Current (NCC) with many individuals utilizing nursery grounds in the Barents Sea. The recruitment to this stock is highly variable with a few years having exceptionally good recruitment. The principal causes of recruitment variability of this herring population have been elusive. Here we undertake an event analysis using data between 1948 and 2010 to gain insight into the physical conditions in the NCC that coincide with years of high recruitment. In contrast to a typical year when northerly upwelling winds are prominent during spring, the years with high recruitment coincide with predominantly southwesterly winds and weak upwelling in spring and summer, which lead to an enhanced northward coastal current during the larval drift period. Also in most peak recruitment years, low-salinity anomalies are observed to propagate northward during the spring and summer. It is suggested that consistent southwesterly (downwelling) winds and propagating low-salinity anomalies, both leading to an enhanced northward transport of larvae, are important factors for elevated recruitment. At the same time, these conditions stabilize the coastal waters, possibly leading to enhanced production and improved feeding potential along the drift route to Barents Sea. Further studies on the drivers of early life history mortality can now be undertaken with a better understanding of the physical conditions that prevail during years when elevated recruitment occurs in this herring stock.     

Limited gene flow in Uca minax (LeConte 1855) along a tidally influenced river system

For crab larvae, swimming behaviors coupled with the movement of tides suggests that larvae can normally move upstream within estuaries by avoiding ebb tides and actively swimming during flood tides (i.e., flood-tide transport [FTT]). Recently, a 1-D transport model incorporating larval behavior predicted that opposing forces of river discharge and tidal amplitude in the Pee Dee River/Winyah Bay system of South Carolina, USA, could limit dispersal within a single estuary for downstream transport as well as become a dispersal barrier to recruitment of late stage larvae to the freshwater adult habitats of Uca minax (LeConte 1855). We sequenced 394-bp of the mitochondrial cytochrome apoenzyme b for 226 adult U. minax, from four locales along a 49-km stretch of the Pee Dee River/Winyah Bay estuary, above and below the boundary of salt intrusion. Results of an analysis of molecular variance (AMOVA) and an exact test of population differentiation showed a small, but statistically significant (α=0.05) population subdivision among adults of the 4 subpopulations, as well as all subpopulations being significantly differentiated (α=0.05). This pattern fitted with model predictions, which implies that larval transport within the tidally influenced river system is limited.     

Behavior of larval Hemigrapsus sanguineus (de Haan) in response to gravity and pressure

Hemigrapsus sanguineus is an invasive species of crab (family: Grapsidae) in the north Atlantic basin. The species has spread rapidly since it was first discovered in North America in the late 1980s; however, the mechanisms of this range expansion remain unclear. This study attempts to predict the vertical distribution and, thus, ultimate transport of H. sanguineus larvae by examining larval responses to gravity and pressure. Geotaxis was determined by measuring the response of individual larvae to gravity in the absence of other tactic stimuli. Barokinesis was determined by measuring changes in swimming speed of larvae upon step-wise changes in pressure. Geotactic response of the larvae changes ontogenetically; early stage larvae are negatively geotactic (orienting towards the surface), while late stage larvae are positively geotactic (orienting towards the bottom). Larvae show a response to pressure that would aid in depth regulation. Early-stage larvae increase activity upon a change in pressure and orient their movement to gravity. However, the larvae show a relatively low sensitivity to pressure change. The evidence predicts an export-and-return model of larval transport, similar to that of Uca spp. in the Middle Atlantic Bight. This model supports the hypothesis that H. sanguineus larvae have the potential for high dispersal and will continue to invade new regions through larval transport.     

Larval dispersal,recruitment, and adult distribution of the brooding stony octocoral<Emphasis Type="Italic"> Heliopora coerulea</Emphasis> on Ishigaki Island,southwest Japan

Larval dispersal and recruitment are important factors that determine the distribution of adult corals. The relationships between larval dispersal, recruitment, and the adult distribution of the blue octocoral, Heliopora coerulea, were investigated on Shiraho Reef, Ishigaki Island, southwest Japan. Heliopora coerulea is a surface brooder that releases planulae in June or July on Shiraho Reef. We observed planulae between 1998 and 2000 and found that they did not swim actively; instead, they crawled into their settlement positions after becoming grounded on the substratum. Planulae occurred throughout the water column and were dispersed by tidal and wind-driven currents around the parent population on the reef flat. Recruitment was observed only within 350 m of the parent populations, including areas between the branches of the adult colony. The planulae of H. coerulea had a narrow dispersal range as a result of their mostly benthic, shorter larval duration, and the influence of weaker currents. Thus, the dispersal distance of larvae is determined by their position in the water column, the currents that deliver the larvae, and the competency period of the larvae. The narrow dispersal range of H. coerulea was consistent with recruitment of sexually derived larvae onto their natal reef.     

Ontogenic migration of Pleuronectes flesus larvae in the eastern English Channel

Along the French coast of the eastern English Channel there is a strong separation in the hydrology, zooplankton community and ichthyoplankton assemblages, between a coastal ecosystem of continental influence and an offshore ecosystem of Atlantic influence. During April and May 1995, two surveys (60 stations) were conducted to describe the early life history of fishes in this area, and especially the influence of hydrodynamics on Pleuronectes flesus larval transfer from the spawning grounds to the nurseries. Ontogenic changes in larval distributions were described by variograms and path analysis. P. flesus eggs and young larvae were found in the southern offshore area. Their distributions were mainly influenced by sediment and cold temperature found in the central part of the Channel. Older larvae were found at more northern stations, showing a clumped distribution near estuaries, in areas of low salinity. Apparently, young stages of this species were transported from the south central spawning area to coastal waters by residual currents. Behavioural changes in older larvae facilitate the move to nurseries along the French coast.     

Larval recruitment of the blue mussel Mytilus edulis: The effect of flow and algae

The mussel Mytilus edulis settlement and distribution was studied on plastic panels with manipulated flow regime (faired, bluff, split and angled) with or without water soluble metabolites of the green alga Cladophora rupestris. The panels were exposed vertically on a device (hydrovane) that ensures their constant orientation in the current during the peak of larval settlement at 1 m depth. In order to investigate larval distribution on the panels, half of them were coated with a silicone vacuum grease that prevents larvae from de-attachment. This grease was not toxic and did not attract or repel larvae. Low densities of larvae on the un-greased plates compared to the greased ones suggested that some of larvae left the substratum. The blue mussel larvae initially settled in regions of reduced shear velocity and then redistribute to the regions of high shear velocity. The presence of the alga increased the density of blue mussel larvae and changed their distribution on the panels. Overall, our results demonstrated that larval recruitment of M. edulis is an active process affected both by boundary-layer hydrodynamics and algal waterborne compounds.     

The influence of pre‐settlement and early post‐settlement processes on the adult distribution and relative dominance of two invasive mussel species

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Distribution and drift of the crab Carcinus maenas (L.) (Decapoda, Portunidae) larvae over the continental shelf off northern Portugal in April 1991

The coastal distribution and abundance of Carcinus maenas larvalstages were studied from plankton samples collected in a gridof 79 sampling station organized into six cross-shore transectsextending from the coast to –170 km offshore, betweenthe Mondego and Ave rivers, on the northwest coast of Portugal.The samples were collected in April 1991 with a modified Bémultinet plankton sampler, which was towed from a maximum depthof 200 m and provided a vertical resolution of up to five standardstrata at each station. Current and wind data were availablefor a period that extended beyond the period covered by theobservations All the species' larval stages were found in thesamples, but their distribution was confined to the inner andmiddle shelf stations Vertically, 88% of the larvae occurredin the top 30 m and another 11% in the 30–60 m stratum.The zonal stages I and II were concentrated (–90%) inthe surface layer, but a gradual ontogenic displacement to deeperwaters was observed from then on, the megalopa being equallydistributed between the 0–30 and the 30–60 m strata.Horizontally, there was a dear association of the first zoeawith the estuarine inlet while the older meal stages were dispersedprogressively offshore. Evidence was found that the megalopaexperienced an onshore transport that did not affect the previousstages.This transport is wnsistent with the observation of anonshore flow component at 40 m. It was not possible, however,to examine the hypothesis that this flow conveys the last larvalstage to the coast, but not the previous ones. The dependenceof the along-shore flow component on wind stress lends supportto the hypothesis that the larvae are advected from the northas the upwelling season progresses.     

Hot and salty: the temperature and salinity preferences of a temperate estuarine shrimp larva, Upogebia pusilla (Decapoda: Thalassinidea)

At a time when global climate changes are forcing life to adapt to a warming and salinity-changing environment, it is essential to understand how future changes in ocean chemistry will affect species. This study evaluates the combined effects of temperature and salinity on survival and development of Upogebia pusilla larvae. Combinations were made from three temperatures (18, 23, and 28°C) and three salinities (15, 25, and 35). Survival, larval duration and megalopa size were compared between treatments. U. pusilla larvae developed optimally in the highest salinity (35) and higher temperatures (23–28°C). Low salinities and temperatures did not support larval survival and development, with salinity being the main restricting factor for survival, while temperature affected mainly the duration of the larval stages. Larvae at higher temperatures (23–28°C) presented a higher development rate but no differences were found in megalopa size.     

Fecundity and feeding of <Emphasis Type="Italic">Galerucella calmariensis</Emphasis> and <Emphasis Type="Italic">G. pusilla</Emphasis> on <Emphasis Type="Italic">Lythrum salicaria</Emphasis>

Fecundity and feeding of two introduced sibling biological control species, Galerucella calmariensis and G. pusilla (Coleoptera: Chrysomelidae) on purple loosestrife, Lythrum salicaria L. (Lythraceae) were compared at constant temperatures of 12.5, 15, 20, 25, and 27.5 °C. Larval feeding was also carried out at 30 °C, but at this temperature, larvae developed only to the L2 stage and none pupated. Thus, data for this temperature were not used in the analysis. There were significant species × temperature interactions in fecundity. Of the two species, Galerucella pusilla laid more eggs. Although egg production of both species was lowest at 12.5 °C and increased to 20 °C, at higher temperatures, the two species reacted differently. From 25 to 27.5 °C, egg production decreased for G. pusilla, but G. calmariensis fecundity peaked at 27.5 °C. Significant temperature × species × life-stage interactions were also observed in feeding. For each species, the amount of feeding varied with temperature and stage of development. Galerucella pusilla adults consumed more foliage at 15, 20, and 27.5 °C. However, at 12.5 °C G. calmariensis adults fed more than G. pusilla. G. pusilla larvae consumed an average of 25% less foliage than G. calmariensis. The lower larval consumption of G. pusilla suggests that when food is limited, G. pusilla larvae may have a higher survival rate because of its ability to complete larval development with less food and produce more progeny due to its greater fecundity. When food is not limited neither species would have a competitive advantage and both species could coexist temporally and spatially. However, since G. calmariensis larvae consumed more leaf material, the larval stage of this species would have a greater impact on purple loosestrife than G. pusilla.     

Effects of macroalgal exudates and oxygen deficiency on survival and behaviour of fish larvae

Filamentous algae may create anoxic, i.e. oxygen free, conditions during night and fish larvae that commonly spend their first months in the littoral may therefore be subject to anoxia. We conducted two different experiments; firstly, we measured behaviour of pike larvae (Esox lucius L.), such as frequency of prey attacks and time in vegetation, in the presence of a chemical predator cue and oxygen deficiency. In the second experimental set-up, pike larval survival was monitored in water with added macro-algal exudates (excreted from Pilayella littoralis) and a low oxygen level (3 mg l^− 1). Our results showed that oxygen concentration and the chemical predator signal, caused by three-spined sticklebacks, had strong significant effects on the larval prey attacks. The prey attacks were strongly reduced at 3 mg oxygen l^− 1. However, survival of the larvae was not affected by low oxygen and macro-algal exudates. Pike larvae are very tolerant to hypoxia and exudates excreted by the littoral vegetation, whereas prey attacks are strongly decreased in hypoxia when a predator is around. This may have negative consequences for pike larval growth and recruitment in eutrophicated environments.     

A modelling study of the respective role of hydrodynamic processes and larval mortality on larval dispersal and recruitment of benthic invertebrates: example of Pectinaria koreni (Annelida: Polychaeta) in the Bay of Seine (English Channel)

The dispersal of Pectinaria koreni larvae released from theeastern Bay of Seine (English Channel) was studied using a two-dimensionalhydrodynamic model which integrates tides, wind-driven currentsand eddy diffusion, in order to examine the influence of environmentalforcing and mortality on larval population dynamics. A broadagreement between predicted larval dispersal for two spawningevents observed in 1987 and field data suggests that numericalmodelling may be useful to analyse processes involved in thetransport and the dynamics of larval populations. Larval mortalitymay be as important as hydrodynamic processes on larval lossesfor the adult population. Tides and eddy diffusion had someeffects on larval dispersal, but wind forcing and the timingof spawning in relation to the meteorological environment arepredicted to be the main source of variability in larval dispersalrates. Although wind-induced larval transport may produce interannualvariations in larval retention and recruitment, predicted retentionrates were always sufficient to ensure the maintenance of theadult population, regardless of hydrodynamic conditions. Thelong-range transport of larvae from the eastern Bay of Seineto distant populations was conditioned by constant strong winds,lasting 15 consecutive days, and should be considered an extremelyrare event.     

Travel with your kin ship! Insights from genetic sibship among settlers of a coral damselfish

Coral reef fish larvae are tiny, exceedingly numerous, and hard to track. They are also highly capable, equipped with swimming and sensory abilities that may influence their dispersal trajectories. Despite the importance of larval input to the dynamics of a population, we remain reliant on indirect insights to the processes influencing larval behavior and transport. Here, we used genetic data (300 independent single nucleotide polymorphisms) derived from a light trap sample of a single recruitment event of Dascyllus abudafur in the Red Sea (N = 168 settlers). We analyzed the genetic composition of the larvae and assessed whether kinship among these was significantly different from random as evidence for cohesive dispersal during the larval phase. We used Monte Carlo simulations of similar‐sized recruitment cohorts to compare the expected kinship composition relative to our empirical data. The high number of siblings within the empirical cohort strongly suggests cohesive dispersal among larvae. This work highlights the utility of kinship analysis as a means of inferring dynamics during the pelagic larval phase.