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The dispersal of marine larvae determines the level of connectivity among populations, influences population dynamics, and affects evolutionary processes. Patterns of dispersal are influenced by both ocean currents and larval behavior, yet the role of behavior remains poorly understood. Here we report the first integrated study of the ontogeny of multiple sensory systems and orientation behavior throughout the larval phase of a coral reef fish—the neon goby, Elacatinus lori. We document the developmental morphology of all major sensory organs (lateral line, visual, auditory, olfactory, gustatory) together with the development of larval swimming and orientation behaviors observed in a circular arena set adrift at sea. We show that all sensory organs are present at hatch and increase in size (or number) and complexity throughout the larval phase. Further, we demonstrate that most larvae can orient as early as 2 days post-hatch, and they swim faster and straighter as they develop. We conclude that sensory organs and swimming abilities are sufficiently developed to allow E. lori larvae to orient soon after hatch, suggesting that early orientation behavior may be common among coral reef fishes. Finally, we provide a framework for testing alternative hypotheses for the orientation strategies used by fish larvae, laying a foundation for a deeper understanding of the role of behavior in shaping dispersal patterns in the sea. [ABSTRACT FROM AUTHOR]

Abstract Quantifying the mechanisms of tracer dispersion in the ocean remains a central question in oceanography, for problems ranging from nutrient delivery to phytoplankton, to the early detection of contaminants. Until now, most of the analysis has been based on Lagrangian concepts of transport, often focusing on the identification of features that minimize fluid exchange among regions, or more recently, on network tools which focus instead on connectivity and transport pathways. Neither of these approaches, however, allows us to rank the geographical sites of major water passage, and at the same time, to select them so that they monitor waters coming from separate parts of the ocean. These are instead key criteria when deploying an observing network. Here, we address this issue by estimating at any point the extent of the ocean surface which transits through it in a given time window. With such information we are able to rank the sites with major fluxes that intercept waters originating from different regions. We show that this allows us to optimize an observing network, where a set of sampling sites can be chosen for monitoring the largest flux of water dispersing out of a given region. When the analysis is performed backward in time, this method allows us to identify the major sources which feed a target region. The method is first applied to a minimalistic model of a mesoscale eddy field, and then to realistic satellite-derived ocean currents in the Kerguelen area. In this region, we identify the optimal location of fixed stations capable of intercepting the trajectories of 43 surface drifters, along with statistics on the temporal persistence of the stations determined in this way. We then identify possible hotspots of micro-nutrient enrichment for the recurrent spring phytoplanktonic bloom occurring here. Promising applications to other fields, such as larval connectivity, marine spatial planning or contaminant detection, are then discussed. Highlights • We propose a new Lagrangian method for the design of an optimal monitoring network for the detection of a dispersed tracer. • We analyze its properties with a steady model flow. • We validate it with an array of 43 real drifters. • We apply the method to the case of iron dispersal in the Kerguelen region (Southern Ocean). • We discuss other possible applications, like fish larvae dispersal and contaminant retrieval. [ABSTRACT FROM AUTHOR]

Abstract: Dispersal of young fish through wind‐driven currents has a growing research focus in large freshwater lakes; however, the influence of behaviour on such dispersal has not been tested. Fish may orient to different environmental cues and use swimming behaviours to navigate towards or retain their position within important habitats. To examine the ability of larval and juvenile fishes of the Laurentian Great Lakes to perceive and orient to nearshore or offshore habitats, we carried out a series of behavioural trials in a flume in which fish choose between different combinations of nearshore and offshore water, and well water. Water and a natural assemblage of larval and juvenile nearshore fish (Dominant species: white sucker, Catostomus commersonii, and spottail shiners, Notropis hudonius) used in the experiment were collected from northern Lake Michigan near Beaver Island. Results of our study suggest that young fish are capable of distinguishing and responding to different water sources, indicating a potential to orient within their environment, such as through the use of olfactory cues. We did not see a difference in fish response to changing concentrations of water cues, possibly suggesting that the threshold for fish response occurs at lower concentrations than were tested in our experiments. This preliminary study into orientation of Great Lakes fishes demonstrates the capacity of these fish to orient to cues in water sources and indicates the need to consider active movement in future studies of larval dispersal and habitat choice in the large freshwater lakes. [ABSTRACT FROM AUTHOR]

Recruitment of Chondrostoma nasus and similar fish species in rivers is related to spatiotemporal linkages between larval hatching and nursery habitats. Active swimming behaviour contradicts the assumption that passive particle tracing models can serve as a proxy for larval dispersal models. A racetrack flume with an inshore area of near-natural slope was created to observe individual larval trajectories. A new three-step, raster-based analysis was developed to distinguish four types of movement patterns: active upstream, active downstream, active-passive, and passive. Both larval developmental stage-specific and release site-specific occurrences of these movement patterns were experimentally found for nine flow velocity classes (≤0.225 m·s−1). These current-induced movement patterns, and evaluated durations within them, were used to develop a biased and correlated random walk model that includes rheoreaction - a key behavioural response of fish to flow within rivers. The study introduces the concept and application of a rheoreaction-based correlated random walk model, which coupled with a 3D hydrodynamic model, allows prediction of the spatiotemporal effects of various river discharges, morphologies, and restoration scenarios on larval fish dispersal. [ABSTRACT FROM AUTHOR]

The present study investigated the larval fish dispersal along an estuarine-ocean gradient to explore connectivity between ocean and estuaries. During spring 2009, a combined ocean-estuarine survey was conducted along the Lima estuarine salinity gradient and in two transects off the adjacent coast (northwestern Iberian Peninsula), until the 100 m isobaths. Salinity, total particulate matter, particulate organic matter, total dissolved carbon, and dissolved organic carbon reached higher values at the ocean, and chlorophyll a and nutrients increased at the estuary. From the total 56 taxa identified, 14 were present along the gradient, including estuarine species (ES), marine stragglers (MS), and migrants (MM). Canonical correspondence analysis showed that species were separated along the gradient according to their ecological functional classification. MM associated with high salinity were separated from ES correlated with lower salinities and high chlorophyll a concentrations of inner estuary. Flounder ( Platichthys flesus) showed a typical spatial gradient of MM, with abundance increasing from the ocean towards inner estuary. The dispersal of larvae along the Lima estuarine-ocean gradient was indicative of connectivity between habitats, emphasizing the need to consider this feature in management plans, mainly for species exploited by commercial fisheries. [ABSTRACT FROM AUTHOR]

Atlantic Menhaden Brevoortia tyrannus exhibit particularly complex recruitment dynamics as a coastal-spawning species with seasonal migrations along the North American Coast from Nova Scotia, Canada, to Florida, United States. Despite a coast-wide reduction in juvenile production from the 1970s to the 1990s, Atlantic Menhaden continues to support one of the oldest and largest commercial fisheries on the US east coast. We used a stochastic partial differential equation model to estimate spawning location and larval dispersal on the Atlantic Coast over two time periods, with data from the Northeast Fisheries Science Center ichthyoplankton surveys conducted in 1977-1987 and 2000-2013. Within the study area, Atlantic Menhaden spawning appears to occur primarily near shore over a large spatial range, from southern New England to North Carolina over the majority of the year, but at greatest levels during November and December. Larger, older larvae were found over a similar spatial and temporal range, dispersing farther from shore. Between the two periods, we observed an increase in secondary, spring-time spawning events. We observed no major, directional spatial shift in spawning or dispersal. However, estimated spawning activity increased near Delaware Bay. Both small and large larvae were most abundant in the Southern portion of the study area during both periods. Yet, total spatial coverage of all larvae varied greatly among years until the mid-2000s, when the Atlantic Menhaden population was believed to have recovered reduction in juvenile production from the 1970s to the 1990s. In most recent years, we observed consistent and large areas of spawning and larval dispersal. [ABSTRACT FROM AUTHOR]

The great scallop Pecten maximus supports one of the most important and valuable commercial fisheries around the British Isles and in the northwest of France, but the resource is mainly managed at the scale of each local fishing ground through a combination of European, national and local measures. To analyse the larval dispersal pathways and connectivity patterns among fishing grounds of the great scallop in the Celtic Sea and the English Channel, a particle tracking model was developed. The model combined a 3D physical circulation model that simulated currents and temperature fields and a scallop larval submodel that took into account a temperature-dependent planktonic larval duration and an active vertical swimming behaviour. Due to the lack of stock assessment at the regional scale, the location of the main fishing grounds was established by combining different sources (e.g. grey literature, unpublished scientific surveys, vessel monitoring data, fishermen) while the spawning biomass of each stock was estimated from landings data. Results indicated that each local stock could not be considered as a single independent management unit and that all stocks except that of the Bay of Brest were connected to neighbouring stocks, suggesting that the management should be defined in a metapopulation context. Three major groups of strongly interconnected stocks including two or three stocks exhibiting high retention and self-recruitment rates and some peripheral stocks with a low self-recruitment rate were defined: the North Brittany and Channel Islands, the eastern English Channel, and the SW of England. Our results were discussed in terms of the definition of management units in comparison with genetic and phenotypic data, and in terms of resource management in a transnational context. [ABSTRACT FROM AUTHOR]

Lagrangian Flow Network (LFN) is a modelling framework in which ocean sub-areas are represented as nodes in a network interconnected by links representing transport of propagules (eggs and larvae) by currents. We asses the sensitivity and robustness of four LFN-derived connectivity metrics measuring retention and exchange. The most relevant parameters are tested over large ranges and a wide region with contrasting hydrodynamics: density of released particles, node size (spatial scale of discretization), Pelagic Larval Duration (PLD) and spawning modality. We find a minimum density of released particles that guarantees reliable values for most of the metrics examined. We also find that node size has a nontrivial influence on them. Connectivity estimates for long PLDs are more robust against biological uncertainties (PLD and spawning date) than for short PLDs. For mass-spawners releasing propagules over short periods (≈ 2-10 days), daily release must be simulated to properly consider connectivity fluctuations due to variable currents. In contrast, average connectivity estimates for species that spawn repeatedly over longer durations (few weeks to few months) remain robust even using longer periodicity (5-10 days). Our results have implications to design connectivity experiments with particle-tracking models and to evaluate the reliability of their results. [ABSTRACT FROM AUTHOR]

Pacific bluefin tuna (PBF), Thunnus orientalis (Temminck and Schlegel, 1844), is highly migratory and capable of traversing large distances throughout the North Pacific Ocean. The majority of spawning activity has been reported only from the Sea of Japan and western parts of the Pacific Ocean. We have conducted larval surveys in these areas since 2009 ("late period"), and used generalized additive models (GAM) with presence/absence data to analyze larval distribution with respect to oceanographic conditions, such as sea surface temperature and chlorophyll-cz concentration. Here, we compare our survey data with some historical data collected from 1979 to 1988 ("early period"). In total, 9192 individual PBF larvae were collected from 1979 to 2015, and body lengths ranged from 2 to 11 mm. In the early period, the relatively higher probability area for the presence of PBF larvae in the Pacific Ocean was wider than that in the Sea of Japan. However, in the late period, the relatively higher probability area for presence in the Sea of Japan was wider than in the early period. The spline function of sea surface temperature for PBF larvae was lower in the early period than in the late period, though large uncertainty in the Pacific Ocean in the late period was observed. These results suggest that the change in the distribution pattern of PBF larvae may be caused by ocean warming. [ABSTRACT FROM AUTHOR]

We evaluated spatial variation in fish larval supply to a temperate, lagoon type estuary (Barnegat Bay, New Jersey) by determining species composition, size, and stage into inlets ( n = 2), thoroughfares between adjacent estuaries ( n = 3), and within the estuary ( n = 4) in seasonal, synoptic sampling on night time flood tides during 2010-2014. Larval supply, as sampled with identical plankton nets (1 m diameter, 1 mm mesh) was dominated by post-flexion stage individuals (most 5-10 but reaching 70+ mm) from species spawned in the Atlantic Ocean from a variety of sources (e.g., Sargasso Sea, outer and inner continental shelf) and in the bay. While abundance for individual species varied among locations and years, in general, the larval composition was similar across inlets, thoroughfares, and within the bay within the same seasons. Homogenization across locations was likely the result of the tidal exchanges between the ocean, the estuary, and the adjacent locations. These exchanges provide numerous, redundant sources of larvae to this estuarine nursery. The similarity in larval supply among inlets, thoroughfares, and within the estuary indicates that the longer term study location behind Little Egg Inlet is representative for this, and probably other, estuaries along the New Jersey shore. [ABSTRACT FROM AUTHOR]

Larval dispersal is the key process by which populations of most marine fishes and invertebrates are connected and replenished. Advances in larval tagging and genetics have enhanced our capacity to track larval dispersal, assess scales of population connectivity, and quantify larval exchange among no-take marine reserves and fished areas. Recent studies have found that reserves can be a significant source of recruits for populations up to 40 km away, but the scale and direction of larval connectivity across larger seascapes remain unknown. Here, we apply genetic parentage analysis to investigate larval dispersal patterns for two exploited coral reef groupers ( Plectropomus maculatus and Plectropomus leopardus) within and among three clusters of reefs separated by 60-220 km within the Great Barrier Reef Marine Park, Australia. A total of 69 juvenile P. maculatus and 17 juvenile P. leopardus (representing 6% and 9% of the total juveniles sampled, respectively) were genetically assigned to parent individuals on reefs within the study area. We identified both short-distance larval dispersal within regions (200 m to 50 km) and long-distance, multidirectional dispersal of up to ~250 km among regions. Dispersal strength declined significantly with distance, with best-fit dispersal kernels estimating median dispersal distances of ~110 km for P. maculatus and ~190 km for P. leopardus. Larval exchange among reefs demonstrates that established reserves form a highly connected network and contribute larvae for the replenishment of fished reefs at multiple spatial scales. Our findings highlight the potential for long-distance dispersal in an important group of reef fishes, and provide further evidence that effectively protected reserves can yield recruitment and sustainability benefits for exploited fish populations. [ABSTRACT FROM AUTHOR]

Temperature is an important factor affecting the distributions and life-history traits of marine animals. Deep-sea hydrothermal vents are suitable environments to examine ecologic differences related to temperature, due to the steep temperature gradients around the vents. Rearing experiments under various temperature conditions (5-30 °C) at atmospheric pressure demonstrated a difference in thermal effects on egg hatching and larva in two co-occurring, vent-associated alvinocaridid shrimps - the peripherally distributed Alvinocaris longirostris and the centrally distributed Shinkaicaris leurokolos. The duration before hatching became shorter as temperature increased, while the maximum hatching rate occurred at higher temperatures in S. leurokolos (10-20 °C) than in A. longirostris (10 °C). Hatched larvae of both species were negatively buoyant, and larva with normal abdominal length could actively swim and stay suspended in the mid- or surface water layers of the culture plates under our experimental conditions. However, no larvae settled or metamorphosed into juveniles under the rearing conditions used in this study. Larvae with shortened abdomens occurred under most of the experimental conditions, although they were less frequent at 10 °C in A. longirostris and 20 °C in S. leurokolos. The maximum survival periods at these temperatures were 88 days in A. longirostris and 30 days in S. leurokolos. These characteristics may cause differences in the distributional ranges of the two species. The present results indicate that temperature is an important factor controlling life-history traits of vent shrimps. [ABSTRACT FROM AUTHOR]

Larval dispersal is disproportionately important for marine population ecolgy and evolution, yet our inability to track individuals severely constrains our understanding of this key process. We analyze otoliths of a small reef fish, the common triplefin ( Forsterygion lapillum), to reconstruct individual dispersal histories and address the following questions: (1) How many discrete sets of dispersal histories (dispersal cohorts) contribute to replenishment of focal populations; (2) When do dispersal cohorts converge (a metric of shared dispersal histories among cohorts); and (3) Do these patterns predict spatiotemporal variation in larval supply? We used light traps to quantify larval supply, and otolith microstructure and microchemistry (using laser ablation inductively coupled plasma mass spectrometry; LA- ICP- MS) to reconstruct daily environmental histories of individuals in their 30-d lead-up to settlement. Our results indicate that a variable number of dispersal cohorts replenish focal populations (range of 2-8, mean of 4.3, standard deviation of 2.8). Convergence times varied (from 0 to >30 d prior to settlement), and larval supply was negatively correlated with cohort evenness but not with the number of cohorts, or when they converged, indicating disproportionately large contributions from some cohorts (i.e., sweepstakes events). Collectively, our results suggest that larval reef fishes may variably disperse in shoals, to drive local replenishment and connectivity within a metapopulation. [ABSTRACT FROM AUTHOR]

We investigated the first-feeding success of two species: southern bluefin tuna ( Thunnus maccoyii) and yellowtail kingfish ( Seriola lalandi) to determine if similar culture parameters can be used for both, especially when S. lalandi are held in the same tanks as prey for T. maccoyii. The feeding performance (proportion and intensity) was examined in three short-duration (4 h) experiments: prey density, prey size and larval density. Increasing prey density from 0.5 to 25 rotifers mL−1 increased the proportion of T. maccoyii and S. lalandi larvae feeding. Prey size alone did not affect feeding in either species. Seriola lalandi had a decreased proportion of larvae feeding when larval density reached 50 larvae L−1 concurrent with a gradual increase in feeding intensity between 2 and 50 larvae L−1. In T. maccoyii, there was no pattern to the effect of larval density on the proportion of larvae feeding. The overall feeding performance of larvae was higher in T. maccoyii than S. lalandi. Increased prey density improved the first-feeding ability of T. maccoyii and S. lalandi larvae. The effect of larval density on S. lalandi feeding requires further investigation, to ensure that they remain feeding when provided as prey in T. maccoyii culture. The identification of factors in this study, which increase first-feeding success, will improve the culture of both species. [ABSTRACT FROM AUTHOR]

Amphidromous gobies are circumtropically distributed in mountainous coasts typical of volcanic islands. More than nine goby species recruit seasonally from the Pacific coasts to the Hsuikuluan River estuary eastern Taiwan from the spring to the summer. Using two seasons of field observations and sample collections, we explore the recruitment of amphidromous gobies from the Pacific Ocean into the Hsuikuluan River and their upstream migratory behaviors from the estuary to the lower reaches of the river. A metamorphosis check in the otolith which corresponds to the drop of Sr/Ca ratios from higher > 4 × 10 to lower levels < 4 × 10 is found in most species after recruitment to fresh waters. The marine and freshwater stages for these goby species can therefore be confirmed from otolith microstructure and Sr/Ca ratio analysis, and age in days of these gobies is estimated from otolith daily increments. Rhinogobius gigas recruits to the estuary at 30-40 days after hatching, while the marine planktonic stage ranged from approximately 2-7 months for Awaous melanocephalus, Eleotris fusca, Glossogobius aureus, Sicyopterus japonicus (Tanaka, 1909), Stenogobius genivittatus, and Stiphodon elegans (Steindachner, 1879). The catch data from an artisanal fish trap show lunar and semi-lunar periodicity for the upstream migration of R. gigas and S. japonicus after a brief stay in the estuary. These two species accounted for more than 99 % of the upstream migratory gobies collected in the fish trap. The short marine larval stage and presumed retention at the inshore area help to explain the endemism of R. giga. In contrast, S. japonicus has a lengthy marine stage of 6-7 months, which obviously could allow dispersal over a wide geographic range. [ABSTRACT FROM AUTHOR]

Aim To study the combined effects of climate change on connectivity between marine protected areas ( MPAs) and larval supply to the continental shelf. Location The Mediterranean Sea, where sea surface temperatures are expected to strongly increase by the end of the 21st century, represents an archetypal situation with a dense MPA network but resource overexploitation outside. Methods Using an individual-based mechanistic model of larval transport, forced with an emission-driven regional climate change scenario for the Mediterranean Sea, we explored the combined effects of changes in hydrodynamics, adult reproductive timing and larval dispersal on the connectivity among MPAs and their ability to seed fished areas with larvae. Results We show that, over the period 1970-2099, larval dispersal distances would decrease by 10%, the continental shelf area seeded with larvae would decrease by 3% and the larval retention fraction would increase by 5%, resulting in higher concentration of larvae in smaller areas of the continental shelf. However, connectance within the MPA network would increase by 5% as more northern MPAs would become suitable for reproduction with increasing temperatures. We also show that the effects of changes in adult reproductive timing and larval dispersal on connectivity patterns are additive. Main conclusions Climate change will influence connectivity and the effectiveness of MPA networks, and should receive more attention in future conservation planning and large-scale population dynamics. [ABSTRACT FROM AUTHOR]

The myctophid species Benthosema glaciale and Ceratoscopelus maderensis were predominant in the catches of 10 mesopelagic fish surveys conducted in the Slope Sea, south and southeast of Nova Scotia. The area surveyed included both cold northeastern (Labrador Slope Water - LSW) and warm southwestern (Warm Slope Water - WSW) components of this water mass. The sub-polar-temperate species, B. glaciale, was found to be only about 15% as abundant in WSW as in LSW. Nonetheless, it occurred throughout WSW and reproduced there, maturing at a younger age than in LSW. The temperate species, C. maderensis, the predominant myctophid caught in WSW, had a life cycle of one yr. in most cases, but a small proportion lived for a second year and these occurred primarily in LSW. These larger animals matured sexually and contributed to spawning in the LSW/WSW boundary area, but their reproductive contribution elsewhere in LSW and in continental slope waters remains to be established. Both species had diverse diets, the taxonomic compositions of which overlapped substantially. [ABSTRACT FROM AUTHOR]

Parasitic species can affect host behaviour in various ways. Freshwater mussels of the superfamily Unionoidea have a glochidia larva that is parasitic on fish. Our aim was to evaluate whether fish exposed to glochidia have distinct behaviour that could affect the upstream dispersal of the parasite., Many freshwater mussels are highly endangered, and understanding the relationships with their hosts is important for their conservation. However, research on the behavioural effects of parasitism on fish host activity and/or the upstream dispersal of mussel larvae in nature has received little attention., Specifically, we examined a fish (the chub, Squalius cephalus) that hosts the larval stage of a freshwater bivalve ( Anodonta anatina) and investigated alterations in host behaviour induced by the parasite. One laboratory and two field experiments were conducted using passive integrated transponder systems and radio-telemetry., Infected fish were generally less active in the laboratory and, in the field, dispersed less far upstream. Moreover, radio-telemetry revealed a habitat shift by the infected fish, which were found further from the riverbank., We suggest that behavioural changes in the fish that are induced by glochidia do not facilitate the long-distance dispersal of the mussel but rather cause reductions in fish activity and slight habitat shifts. Possible consequences of such behavioural alterations are discussed. [ABSTRACT FROM AUTHOR]

Dominant drivers of larval survival are considered to include oceanographic dispersal, sea temperatures, and food availability in the phase of first-feeding. However, research progress on larval herring survival dynamics indicates that multiple factors might act on differing larval developmental stages. Hypothesizing that in inshore systems of the western Baltic Sea bottlenecks of herring development occur before the point of first-feeding, we analysed an extensive time-series of weekly abundances of early stage larvae in Greifswald Bay, an important spawning area for Western Baltic herring. Additionally, we investigated whether distinct hatching cohorts contribute differently to established survival indices on the level of (i) later larval stages in Greifswald Bay and (ii) 1+ group juveniles in the overall western Baltic Sea. Results revealed that abundances of the earliest larval stage explain 62% of the variability of later stage larvae and 61% of the variability of surviving juveniles, indicating pre-hatching survival bottlenecks. Hatching cohorts occurring later during the spawning season contribute most to the surviving year class. Earlier hatching cohorts were not found to result in significant amounts of growing larvae, indicating a bottleneck phase at the critical period when larvae start feeding. [ABSTRACT FROM PUBLISHER]

The dispersal patterns of marked larvae of the nase carp (Chondrostoma nasus L.) were observed alongside dissimilar shoreline configurations in the main channel of the free-flowing Austrian Danube and compared with those of floating particles to investigate the mode of dispersal (active–passive). Individuals of different larval stages and floats at similar densities were released at an artificial rip-rap with groynes and a rehabilitated gravel bar. In both habitats, marked individuals were recaptured during the sampling period of 4 d after release. Relevant shoreline attributes for larval dispersal, such as the accessibility of nursery habitats, connectivity between adjacent habitats, and retention potential, were more pronounced at the gravel bar than at the rip-rap. At the gravel bar, larvae moved upstream and downstream within the connected bankside nurseries and displayed longer residence times. Larvae settled in groyne fields along the rip-rap as well; however, longitudinal dispersal was disrupted by groynes, forcing larvae to enter the main channel. Rather than settling in subsequent groyne fields, we assume that these larvae are displaced downstream and potentially lost from the local population. [ABSTRACT FROM PUBLISHER]

The spatial distribution of fish larvae was studied in the Canaries- African Coastal Transition Zone, outside the strong upwelling season. An onshore-offshore transition in the larval fish community structure was observed, from a coastal assemblage dominated by small pelagics (sardine, anchovy, mackerel), bounded by the upwelling front, to an offshore assemblage dominated by mesopelagic species (mainly Myctophidae, Phosichthydae, Gonostomatidae). Distribution of the neritic larvae was deeply influenced by the intense mesoscale activity found in the area, both horizontally (larvae were advected offshore but were always retained within the upwelling area) and vertically (larvae were deepened in the vicinity of two anticyclonic eddies). A combined effect of the upwelling front and a cyclonic-anticyclonic eddy dipole is likely the successful retention mechanism for these larvae. These results support the current belief that retention may be higher than previously thought in upwelling areas. Oceanic larvae were also collected in higher abundances near the front and an anticyclonic eddy. Neritic and oceanic larvae frequently showed a differentiated position in the water column, although they sometimes coexisted. Finally, larval connectivity between Islands within the Canary archipelago is suggested. The present study thus contributes to the understanding of the complex dispersal and retention processes in the Canaries- African Coastal Transition Zone. However, results also highlight the poor knowledge of this region compared with the other three main Eastern Boundary Upwelling Systems in terms of ichthyoplankton dynamics. The importance of routine monitoring programs of commercial and non-commercial species in the area is emphasized. [ABSTRACT FROM AUTHOR]

The polychaete Pectinaria koreni exhibits a complex life cycle characterized by non-overlapping generations and widespread larval dispersal. To explore how 'local' metapopulation genetic structure varies spatially and temporally during population turnover, we combined observations on demography, larval dispersal through hydrodynamic modelling and population genetics of successive age cohorts in the Baie de Seine (eastern English Channel, France). Mature adults (March), newly settled (July) and later-stage juveniles (September) were sampled in 2003 on the edge and in the main demes of the metapopulation. Demes displayed an asynchronous dynamics due to variations in habitat quality affecting reproductive timing (e.g. three distinct spawning events observed) and in local larval supply linked to temporal fluctuations of hydrodynamism. Two-source populations were identified among dense areas with the greatest larval retention and self-recruitment rates: one with a single recruitment event, stable temporal genetic variation and a strong spatial genetic re-homogenization during turnover, and the other with two recruitment events and significant allele frequency changes over time. Sink habitats displayed single recruitment event and experienced strong inter-generational (juveniles vs adults) genetic changes due to genetic drift associated with strong winter mortalities. Altogether, results suggested that adult spawning asynchrony and sweepstakes reproductive success, together with genetic drift, played a greater role than hydrodynamics itself in determining effective recruitment rates at some sites and generating genetic patchiness. [ABSTRACT FROM AUTHOR]

Vásquez, S., Correa-Ramírez, M., Parada, C., and Sepúlveda, A. 2013. The influence of oceanographic processes on jack mackerel (Trachurus murphyi) larval distribution and population structure in the southeastern Pacific Ocean. – ICES Journal of Marine Science, 70: 1097–1107.The distribution of jack mackerel larvae in the main oceanic spawning area of the southeastern Pacific Ocean was investigated through three consecutive spring bio-oceanographic surveys (2003–2005). In this study, otolith microstructure analysis revealed a spatial age gradient with the smallest/youngest larvae specimens found primarily in the offshore area and the largest/oldest found in the coastal area, implying offshore-inshore larval drift. This suggests a connection between the oceanic spawning area and the historical coastal nursery ground (north of 30°S). In order to understand the oceanographic processes that drive this larval transport, we inferred circulation patterns from two data sources: mesoscale eddy trajectories identified by applying the Okubo-Weiss parameter to satellite geostrophic currents, and 20 years of satellite tracking data of drifters. Our results showed that eddy trajectories lead to net northwestward offshore transport (the opposite direction of larval connectivity). In addition, mean circulation associated with the subtropical anticyclonic gyre and recurrent energetic meandering structures seem to be the major mechanisms driving the spatial dynamics of the early jack mackerel life history, determining a net transport to nursery grounds. These mechanisms could play a key role in recruitment, which supports the continuity of the jack mackerel population. [ABSTRACT FROM PUBLISHER]

The Humboldt Current System ( HCS) sustains the world′s largest small pelagic fishery. While a cooling of this system has been observed during recent decades, there is debate about the potential impacts of rising atmospheric CO2 concentrations on upwelling dynamics and productivity. Recent studies suggest that under increased atmospheric CO2 scenarios the oceanic stratification may strongly increase and upwelling-favorable winds may remain nearly constant off Peru and increase off Chile. Here we investigate the impact of such climatic conditions on egg and larval dispersal phases, a key stage of small pelagic fish reproduction. We used larval retention rate in a predefined nursery area to provide a proxy for the recruitment level. Numerical experiments are based on hydrodynamics downscaled to the HCS from global simulations forced by pre-industrial ( PI), 2 × CO2 and 4 × CO2 scenarios. A biogeochemical model is applied to the PI and 4 × CO2 scenarios to define a time-variable nursery area where larval survival is optimum. We test two distinct values of the oxycline depth that limits larval vertical distribution: One corresponding to the present-day situation and the other corresponding to a shallower oxycline potentially produced by climate change. It appeared that larval retention over the continental shelf increases with enhanced stratification due to regional warming. However, this increase in retention is largely compensated for by a decrease of the nursery area and the shoaling of the oxycline. The underlying dynamics are explained by a combination of stratification effects and mesoscale activity changes. Our results therefore show that future climate change may significantly reduce fish capacity in the HCS with strong ecological, economic and social consequences. [ABSTRACT FROM AUTHOR]

Larval Japanese eel (leptocephali) are passively transported from their spawning sites of the North Equatorial Current to the Kuroshio and its branch waters for 4-6 months before reaching the East Asian coasts. The larvae mainly stay within water depths between 50-150 m. The dispersal dynamics of larvae thus should reflect the sub-surface oceanic currents on the East Asia continental shelf. An analysis of Japanese glass eel catch data in East Asian countries during 1985 to 2009, and for Taiwan from 1968 to 2008, indicates that the overall annual catch is generally correlated across countries of East Asia, and between north and west areas of Taiwan. The Kuroshio and its branch waters disperse glass eels throughout East Asian habitats, and the glass eel distribution matches the flow directionality of oceanic currents. Recruitment in western Taiwan occurs with a sequential southwestern to northwestern direction, suggesting that the Taiwan Strait Current penetrates the western coast of Taiwan in the sub-surface layer in winter. The monthly averaged sub-surface 50 m circulation pattern in the vicinity of Taiwan and modeled tracer experiments also support the northward winter sub-surface current in Taiwan Strait. These results suggest that the larval Japanese eel could serve as a valuable bio-tracer of sub-surface currents, and the earlier recruitment dynamics of Japanese glass eels in Taiwan could be a good predictor for the subsequent catch in other East Asia areas. [ABSTRACT FROM AUTHOR]

Determining the extent of dispersal in exploited marine fishes is essential for understanding their population dynamics and optimising management. The West Australian dhufish, Glaucosoma hebraicum, is a highly sought-after, large and long-lived reef-dwelling species, endemic to south-western Australia. Stock assessments indicate that this indicator species is overexploited. The fishery is managed using a zone-based system, which implicitly assumes a high degree of demographic independence among zones. While tagging studies indicate limited movement of adult G. hebraicum, there is no understanding of the spatial scale of dispersal of its larvae and thus the true extent of interdependence of management zones. We analysed 13 microsatellite DNA loci to characterise the extent of gene flow, and conducted particle tracking simulations to model larval transport in this species. Genetic data demonstrated that some local recruitment was likely, but that on a broad scale gene flow between the management zones was extensive, and the entire fishery represents a single genetic stock. Hydrodynamic modelling predicted that the majority of dhufish larvae recruit from within the management zone where they are spawned, and that inter-annual variation in current velocities has limited effect on the extent of larval transport. Because management zones are likely to be largely independent in terms of both larval and adult recruitment, heavy localised fishing pressure has the potential to reduce the abundance and reproductive capacity of this species in highly fished areas, but it should have limited impact on neutral genetic diversity. [ABSTRACT FROM AUTHOR]

We assessed by numerical modeling the coastal fish larval dispersion along the southern coast of Mallorca (Balearic Islands, NW Mediterranean) with the objective of determining the factors that contribute to successful recruitment. We assumed that fish larvae dispersal is mainly regulated by physical transport. Currents are mainly wind driven in this area; therefore, changes in wind forcing have a first-order impact on larval transport. The synoptic wind patterns were systematically analyzed based on self-organizing map analysis. The wind fields were clustered using a neural network pattern recognition approach into two modes, producing opposite along-shelf flow. The seasonal changes between spring and summer in the dominance of either mode modulate the along-shelf circulation, producing flow shifts under some circumstances. This variability in the wind regime was consistent throughout the 10 years analyzed (2000-2009). Using the Princeton Ocean Model (POM) and a particle-tracking algorithm, we analyzed the effect of wind-forced currents in the connectivity among near-shore habitats. We show that, at the spatial scale considered, the coastal morphology and stochastic wind forcing favor local recruitment (mean of 30% self-recruitment). Maximum transport distances of 20-30 km were typically associated with particles left to drift for 21 days. The implications for the performance of the four marine protected areas near SW Mallorca Island are discussed. Our results suggest that, although wind episodes determine the fate of short-time spawning events, on a seasonal basis, regular larval supply to coastal zones is ensured by wind stochasticity. [ABSTRACT FROM AUTHOR]

For many marine fish species, recruitment is strongly related to larval survival and dispersal to nursery areas. Simulating larval drift should help assessing the sensitivity of recruitment variability to early life history. An individual-based model (IBM) coupled to a hydrodynamic model was used to simulate common sole larval supply from spawning areas to coastal and estuarine nursery grounds at the population scale in the eastern Channel on a 14-yr time series, from 1991 to 2004. The IBM allowed each particle released to be transported by currents from the hydrodynamic model, to grow with temperature, to migrate vertically giving stage development, and possibly to die according to drift duration, representing the life history from spawning to metamorphosis. Despite sensitivity to the larval mortality rate, the model provided realistic simulations of cohort decline and spatio-temporal variability of larval supply. The model outputs were analysed to explore the effects of hydrodynamics and life history on the interannual variability of settled sole larvae in coastal nurseries. Different hypotheses of the spawning spatial distribution were also tested, comparing homogeneous egg distribution to observation and potential larval survival (PLS) maps. The sensitivity analyses demonstrated that larval supply is more sensitive to the life history along larval drift than to the phenology and volume of spawning, providing explanations for the lack of significant stock-recruitment relationship. Nevertheless, larval supply is sensitive to spawning distribution. Results also suggested a very low connectivity between supposed different sub-populations in the eastern Channel. [ABSTRACT FROM AUTHOR]

Abstract: Intense fishing of a stock of sandeels (Ammodytes marinus) on the sand banks off the Firth of Forth, northeast Scotland, during the 1990s led to a decline in catch per unit effort to uneconomic levels and collateral failures of piscivorous seabird breeding success at nearby colonies. A prohibition on fishing in 1999 was followed by a short-term recovery of stock biomass, but then a sustained decline to very low levels of abundance. Demographic survey data show that despite the decline in stock, recruit abundance was maintained implying an increasing larval survival rate, and that the stock decline was not due to recruitment failure. To verify this hypothesis we analysed a 10-year long data set of weekly catches of sandeel larvae at a nearby plankton monitoring site to determine the patterns of larval mortality and dispersal. We found that the loss rate of larvae up to 20d age decreased over time, corresponding with the trend in survival rate implied by the stock demography data. The pattern of loss rate in relation to hatchling abundance implied that mortality may have been density dependent. Our study rules out increased larval mortality as the primary cause of decline in the sandeel stock. [Copyright &y& Elsevier]

Recruitment of European anchovy has been traditionally thought to largely depend on the passive transport and dispersion of eggs and larvae from spawning to nursery areas. Knowledge of the factors influencing the vertical distribution of fish early stages, and consequently influencing the transport, is a crucial issue in fisheries science. The aim of this study is to assess the relevance of diel vertical migration (DVM) as a mechanism involved in the transport of European anchovy larvae toward nursery areas taking into account age/stage-dependent vertical migration (i.e., the maximum migration). We developed a simplified vertical migration sub-model for anchovy larvae included in an Individual-based (IBM) hydrodynamic coupled model. Two types of simulation experiments were conducted: (1) ‘Pure’ Lagrangian (passive) transport experiments and (2) biological behavior transport experiments with a realistic scheme for egg-buoyancy, larval growth, and DVM scheme. We detected high variability in the trajectory and final position of larvae with 14mm length between the passive and biological behavior experiments. The particles were less clustered in the passive transport experiment. In the biological experiment the particles were aggregated depending on the mesoscale oceanographic structures, evidencing a transport associated to filaments and meanders. The formation of schools was facilitated by the transport in filaments and larvae transported within filaments generally avoided the nucleus of the eddies and the central part of the North Current. Moreover, our results suggest that there is interconnectivity between all the anchovy sub-populations in the NW Mediterranean and that the Gulf of Lions and the shelf waters surrounding the Ebro River Delta are the most important areas for anchovy reproduction in this region. Additionally, we detected that the pre-recruitment is higher in those years when the larvae retention is favored. We underline that bottlenecks in larval transport modeling are related to the scarcity of knowledge in developmental biology and behavior of anchovy larvae and emergent mechanistic processes. [Copyright &y& Elsevier]

Most models developed for the movement and fate of eggs and larvae of aquatic species are based on a particle tracking approach. Although this method has many advantages due to its high flexibility, particle tracking may become computationally intensive for complex geometries and when large numbers of particles are needed to simulate the population properly. In continuous models based on advection and dispersion mechanisms, the computational burden is independent of the size of the population. We developed a continuous fate and transport model for striped bass eggs and larvae in the San Francisco Bay–Delta. The model predicts the concentration of eggs and larvae at any location over time. The method of moments was used to account for the effect of temperature and age on the transition of eggs to larvae and larvae to juveniles. Egg and larval mortality were represented as functions of temperature, and eggs also experienced settling mortality. The fate and transport model used the same one-dimensional spatial grid as the existing Delta Simulation Model II (DSM2) hydrodynamics model. DSM2 output of flow rates, water depths, and cross-sectional areas were inputted into the fate and transport model to determine transport. The model was applied to striped bass eggs and larvae data collected during years 1990–1994; agreement between the modeled and the measured data was acceptable in most cases. Exploratory simulations were performed to demonstrate how the model could be used to evaluate the effects on egg and larval survival and total juvenile production of water diversions for supply and agricultural use and changes in the long-term mean water temperature. The model can be further used to examine the impact of various operation strategies in the San Francisco Bay–Delta, where diversion losses of early life stages of fishes remain a major management issue. [Copyright &y& Elsevier]

Mortality that occurs during larval dispersal as a consequence of environmental, maternal, and genetic effects and their interactions can affect annual recruitment in fish populations. We studied larval lake sturgeon ( Acipenser fulvescens) drift for two consecutive nights to examine whether larvae from different females exposed to the same environmental conditions during dispersal differed in relative levels of mortality. We estimated proportional contributions of females to larval collections and relative larval loss among females as larvae dispersed downstream between two sampling sites based on genetically determined parentage. Larval collections were composed of unequal proportions of offspring from different females that spawned at upstream and downstream locations (~0.8 km apart). Hourly dispersal patterns of larvae produced from females spawning at both locations were similar, with the largest number of larvae observed during 22:00-23:00 h. Estimated relative larval loss did not differ significantly among females as larvae were sampled at two sites approximately 0.15 and 1.5 km from the last section downstream of spawning locations. High inter- and intra-female variation in larval contributions and relative larval loss between nights may be a common feature of lake sturgeon and other migratory fish species, and likely is a source of inter-annual and intra-annual variation in fish recruitment. [ABSTRACT FROM AUTHOR]

Abstract: This study combines observational data with a two-dimensional numerical model results to determine the fate of fish eggs released in the Gulf of Kachchh (GoK), a semi enclosed basin on the west coast of India. Fish eggs were treated as passive particles in the model, and were released from probable spawning sites identified from the field surveys. Areas with retention of larvae above 30% have been demarcated as nursery areas. Most of these nursery areas fall in ecologically significant sites which are rich in mangroves and reefs. We find that about 80% of the particles are retained in the basin for all the three prominent seasons prevailing in the GoK. Complete retention of particles in the southern Gulf region and small quantity of flushing out in the northern boundary of the Gulf could be a major reason for sustaining an abundance of larvae in the southern Gulf. Trawler catch data at various sampling points also suggest abundance of fish in the southern GoK region. Model simulation of fish larval transport in the GoK reiterates the fact that fish larval aggregation occurs in the southern GoK during active breeding phase with varying dispersal patterns from spawning sites. Marine protected areas in the Gulf demarcated based on the ecological significance of sites reasonably corroborate with the areas of likelihood of retention of fish larvae differentiated by the model. [Copyright &y& Elsevier]

Population genetic variation of Australian grayling Prototroctes maraena was examined to determine whether the dispersal strategy of this amphidromous species favours retention of larvae and juveniles in close proximity to their natal river, or mixing of populations via marine dispersal. Variation in microsatellite and mitochondrial DNA markers was unstructured and differentiation was indistinguishable from zero across four coastal rivers spanning approximately one-quarter of the continental range of the species. This result indicates that the marine larval and juvenile phase probably facilitates extensive gene flow among coastal rivers and agrees with a previous analysis of otolith chemistry that suggested larvae probably move into the sea rather than remain in estuaries. It appears likely that the dispersal strategy of P. maraena would enable recolonization of rivers that experience localized extinction provided that connectivity between freshwater habitats and the sea is sufficient to permit migration and that enough source populations remain intact to support viability of the wider population. [ABSTRACT FROM AUTHOR]

Spatial management of marine populations typically requires consideration of larval dispersal pathways. When a power plant with a cooling water intake system (CWIS) is present, managers must also account for reductions in larval supply to natural habitats due to larval entrainment in the CWIS. To evaluate the consequences of CWIS entrainment for benthic populations, we coupled a transport model for an idealized coastline to a spatially explicit metapopulation model. CWIS entrainment reduced the probability of dispersal to and from sites near the CWIS. However, the reductions in larval supply due to entrainment generally produced only minor, localized effects on adult population density because of postsettlement density-dependent mortality. Only when population densities were already reduced by other forms of adult or larval mortality did entrainment threaten population persistence. Our simulations suggest that subpopulations several kilometres upstream of CWIS make the greatest contribution to metapopulation persistence by countering the effects of CWIS entrainment, and these locations should be the focus of conservation efforts to enhance larval sources. Finally, we show that traditional statistics used to estimate the demographic effects of CWIS entrainment are generally inaccurate and unreliable because they ignore nonlinearities in population dynamics. [ABSTRACT FROM AUTHOR]

Natural geochemical signatures in calcified structures are commonly employed to retrospectively estimate dispersal pathways of larval fish and invertebrates. However, the accuracy of the approach is generally untested due to the absence of individuals with known dispersal histories. We used genetic parentage analysis (genotyping) to divide 110 new recruits of the orange clownfish, Amphiprion percula, from Kimbe Island, Papua New Guinea, into two groups: 'self-recruiters' spawned by parents on Kimbe Island and 'immigrants' that had dispersed from distant reefs (>10 km away). Analysis of daily increments in sagittal otoliths found no significant difference in PLDs or otolith growth rates between self-recruiting and immigrant larvae. We also quantified otolith Sr/Ca and Ba/Ca ratios during the larval phase using laser ablation inductively coupled plasma mass spectrometry. Again, we found no significant differences in larval profiles of either element between self-recruits and immigrants. Our results highlight the need for caution when interpreting otolith dispersal histories based on natural geochemical tags in the absence of water chemistry data or known-origin larvae with which to test the discriminatory ability of natural tags. [ABSTRACT FROM AUTHOR]

Abstract: To examine the larval transport processes of this species and help determine why the Pacific bluefin tuna (Thunnus orientalis: PBT) spawns in a restricted area and during a limited season compared to other tropical tuna species, we used survey data of larval distributions, Lagrangian numerical simulations, and SST data analysis. A high density area of larvae was detected in the waters east of Taiwan, where larvae were likely entrained in anticyclonic eddies after hatching. The numerical simulations indicated that spawning areas east or south of Taiwan could supply PBF larvae to the estimated nursery area located in Japanese coastal waters, irrespective of annual fluctuations in oceanographic conditions. The simulation also showed that particles released to the east of the spawning area were not successfully transported to the nursery area. The trajectories of the successful particles indicated that larvae can be transported with a low energetic cost to cooler temperate waters by utilizing the strong current of the Kuroshio or the Ryukyu Current followed by the Kuroshio. The ambient temperatures around the nursery were found to be favorable with a similar temperature range as the larval distribution area only during August to September. If they do not spawn during the period April to July, the larvae will be exposed to unfavorable water temperature conditions. We hypothesize that PBT spawn in a restricted region during a limited period (April to July) to maximize the chances of their larvae entering the nursery regions in temperate waters with low energetic costs, which ensures optimal thermal conditions for growth and survival, although the spawning area may be unfavorable for the adults due to warm water temperatures. [ABSTRACT FROM AUTHOR]

Larval dispersal may have an important effect on genetic structure of benthic fishes. To examine the population genetic structure of spottedtail goby Synechogobius ommaturus, a 478 base pair (bp) fragment of the hypervariable portion of the mtDNA control region was sequenced and used to interpret life-history characteristics and larval dispersal strategy. Individuals ( n = 186) from 10 locations on the coasts of China and Korea were analysed and 44 haplotypes were obtained. The levels of haplotype and nucleotide diversity were higher in East China Sea populations than in other populations. Both the phylogenetic tree and the minimum spanning tree showed that no significant genealogical structures corresponding to sampling locations existed. AMOVA and pair-wise FST revealed significant genetic differentiation between populations from Korea and China. A significant isolation by distance pattern was observed in this species ( r = 0·53, P < 0·001). Both mismatch distribution analysis and neutrality tests showed S. ommaturus to have experienced a recent population expansion. These results suggest that the Pleistocene ice ages had a major effect on the phylogeographic pattern of S. ommaturus, that larvae might avoid offshore dispersal and that dispersal of larvae may maintain a migration-drift equilibrium. [ABSTRACT FROM AUTHOR]

Abstract: We examined the patterns of abundance and distribution of Alaska plaice, Pleuronectes quadrituberculatus, eggs, larvae and pelagic juveniles over the southeastern Bering Sea shelf to better understand factors controlling transport and recruitment of flatfish in the Bering Sea. Ichthyoplankton data were derived from plankton surveys conducted in 1997, 1999, 2002, 2003, and 2005. Temperature, salinity, depth, and abundance of microzooplankton were measured concurrently. Eggs and larvae were primarily collected from depths <200 m, with the majority occurring over bottom depths ranging 50–100 m. Eggs were present throughout the water column, though densities of preflexion stage larvae were concentrated at depths 10–20 m. There was no evidence of vertical migration for pre-flexion stages. Spawning in Alaska plaice occurs primarily east of Port Moller in April and May, and eggs and larvae appear to drift to the north and northeast, an observation based on satellite-tracked drifter information, model output, and collections of older, later-stage postlarvae. Connectivity between spawning areas and nursery habitats is likely influenced by wind forcing, so climate-mediated changes to dispersal trajectory or timing is expected to have significant impacts on recruitment in this species, though entrainment in consistent, directional currents may modify these effects. [Copyright &y& Elsevier]

The article presents a study which evaluates the relationship between the recruitment intensity and larval environmental conditions of Forsterygion lapillum reef fishes in New Zealand. The method of the study includes the quantification of the variation in recruitment of the reef fishes through utilizing a nested sampling design, which entails the deployment of a standardized collector in the rocky environment of the sampling site where the reef fishes are to be founded. It also notes the assessment of the composite measure of the settler condition in terms of residual body mass, instantaneous, and late larval growth rate. The result of the study shows that the association between the settler condition and recruitment is spatially variable.

Abstract: It is well established that progeny of inbred matings are less fit than those of outbred matings, and that inbred individuals suffer from reduced viability and fertility. Inbreeding can be avoided by dispersal of progeny or by actively avoiding mating with kin (mate choice). We investigated the effects of sex ratio, relatedness (kinship coefficient) and level of inbreeding on the reproductive success in Nile tilapia under semi-natural mass spawning conditions in two net enclosures (hapas). Fry were collected from the mouth of incubating females on a weekly basis and parentage assignment was done on 1115 offspring from 56 spawnings using seven polymorphic microsatellite markers. Results show that the degree of pairwise relatedness, measured by kinship coefficient, did not have any significant effect on the reproductive success of males. Female total fecundity was significantly affected by the level of inbreeding but not by body weight and gonadosomatic index. Male reproductive success, calculated as the proportion of offspring sired within a single spawning, was significantly affected by the level of inbreeding, body weight, GSI of males and sex ratio. Effects of inbreeding on male reproductive success were higher in the presence of higher number of males suggesting that the effects of inbreeding are magnified under stronger male–male competition. Our results show that there is no inbreeding avoidance via kin recognition and that accumulation of inbreeding in tilapia populations is counterbalanced by reduced reproductive success of inbred males and females. [Copyright &y& Elsevier]

Abstract: The Barents Sea capelin stock is, potentially, the largest capelin stock in the world, with a maximum biomass in the range of 6–8 million tonne. The main spawning grounds for this capelin stock are along the coast of northern Norway. By modeling and fieldwork, this study addresses the interaction between mesoscale physical process and newly hatched capelin larvae. The study documents a close relationship between selected spawning location, advection, retention, mortality windows and dispersal patterns. [Copyright &y& Elsevier]

The article discusses the study on the behavioural ontogeny of coral-reef fishes. It notes that speed, orientation, and vertical distribution of four coral-reef fishes such as Platax teira, Lutjanus malabaricus, Epinephelus coioides, and E. fuscoguttatus from aquaculture farms in Taiwan were measured. Results show that there are significant linear relationships between size and swimming speed in all of the four study species. Furthermore, the study also reveals the behavioural compensation in Platax teira, as well as the strong differences in the behaviour of two Epinephelus species. It concludes that behaviours and development of larval reef fishes affect larval and other reef-fish species' dispersal.

Abstract: A coupled physics particle-tracking model, driven by realistic meteorological forcing was used to examine the dispersal and transport of plaice eggs and larvae in the year 2000 from two spawning grounds in the Irish Sea. The model included passive transport of eggs and early stage larvae, diel vertical movements for larvae between 7 and 10.5mm in body-length and tidally synchronised, vertical movements for larger larvae (>9mm body-length). The year 2000 was chosen because of the availability of ichthyoplankton data with which to initialise the model. The majority of larvae originating from spawning in the eastern Irish Sea settled into nursery grounds along the Scottish, English and Welsh coasts, in agreement with previous findings. In contrast, a significant portion of larvae originating from spawning in the western Irish Sea was transported eastwards to these same nursery grounds. Transport across the Irish Sea resulted from the onset of tidally synchronised vertical behaviour encoded in the model for older larvae. Settlement of larvae into local nursery grounds along the Irish coast was limited. Because of the prevailing winds and currents in the region, plaice eggs and larvae are unlikely to be transported from east to west; in most years spawning in the western Irish Sea probably acts as an additional source of juveniles for nursery grounds along the Scottish, English and Welsh coasts. [Copyright &y& Elsevier]

Abstract: Allozyme electrophoresis was used to investigate the genetic stock structure of snapper, Pagrus auratus (Bloch and Schneider) on the east coast of Australia. Spatial variation in allele frequency was examined at nine polymorphic loci. The results support a single, relatively weak genetic disjunction among the P. auratus populations north of Sydney (latitude 33°52′) but south of Forster (latitude 31°58′) on the central coast of New South Wales. There was also evidence for genetic isolation by distance on the east coast. The influence of the East Australian Current (EAC) in transporting larvae to the south, coupled with the general northward migration pattern of adult snapper is believed to be responsible for maintaining a panmictic snapper population on much of the east coast of Australia. [Copyright &y& Elsevier]

We examined larval dispersal and behaviour in rainbow smelt (Osmerus mordax) from the Salmonier River estuary, Newfoundland, during 2003–2005. Riverine ichthyoplankton surveys indicate that larval transport into the estuary is restricted to a two-week period in late June. A passive drifter experiment and the spatial distribution of larvae and juveniles suggest limited dispersal and low export from the estuary. The estuary exhibited low inflow and stratification in summer and high inflow with a stable freshwater layer in fall. Summer and fall winds are primarily onshore. We hypothesised that larval vertical swimming behaviour limits dispersal and export. Larval vertical position and swimming ability were examined through lab-based experiments conducted 0–10 and 90 days after hatching. Measurements of swim speed indicate an order of magnitude (p < 0. 001) improvement in swimming capacity between larvae and juveniles. One-week after hatching, larvae displayed consistent negative geotaxis, whereas juveniles were generally deeper and displayed negative geotaxis in light and positive geotaxis in the dark. The contrasting light-mediated geotactic behavior between development stages corresponds to ontogenetic shifts in swimming abilities and seasonal changes in estuarine circulation. We suggest that the interaction between behaviour, ontogeny, and hydrography results in limited transport and a tendency for estuarine-scale recruitment, despite an extensive pelagic period. [ABSTRACT FROM AUTHOR]

A multivariate spatial Objective analysis (MVOA) assimilating high spatio-temporal resolution of hydrographic (CTD) and acoustic (ADCP) observations near Barbados provided a comprehensive view of the local surface circulation (0-100m) during early spring of two consecutive years (1996 and 1997). Significant submesoscale fluctuations of the velocity and salinity fields exhibit a very dynamic environment. In the middle of each cruise, lowsalinity water originating from the Amazon and entrained by a North Brazil Current Ring (NBCR) intruded from offshore and persisted on the west coast of Barbados throughout the rest of the survey. Principal component analysis (PCA) of velocity relative to the vertical structure and temporal factors in the study area demonstrated that the local circulation was mostly baroclinic and was dominated by a strong salinity front impinging on the island and large amplitude current reversals with a periodicity of ca. 20 d. During transition times, indicated by a change of the sign of the amplitude of the empirical orthogonal function (EOF), the flow became barotropic. This situation produced strong southward currents followed by the onset of vertical velocity shear. Most of the flow variability occurred in the upper 40 m of the water column, which was also found to be the depth of penetration of the low-salinity lenses. These results indicate that the NBCR structure was retained during both intrusions. Lagrangian trajectories using the MVOA currents were found to be consistent with in situ drifter trajectories, suggesting that the analyzed flow field is representative of the near-shore circulation. Tracking of particles released in the surface layer (0-20 m) from the reef shows a maximum residence time of 18 d indicating the possibility of larval retention within the island-scale flow field. Finally, our results suggest that MVOA, within its limitations, is a powerful tool that can be applied elsewhere to infer circulation and larval... [ABSTRACT FROM AUTHOR]

A primitive equation numerical model is used to systematically investigate wake formations at Cato Island (155°32'E, 23°15'S) under a variety of realistic flow conditions. The model faithfully reproduces the key features of data obtained in the vicinity of the island under conditions of"strong" (∼0.7 m s[sup -1]) and "weak" (∼0.3 m s[sup -l]) incident currents. For the strong inflow study, a vortex shedding wake is indicated, with an eddy shedding period of approximately 36 h. Interaction between wake and free stream currents produces strong downwelling and upwelling in regions of flow convergence and divergence, respectively. For the weak inflow case, a Lagrangian analysis of wake currents shows strong particle retention properties and vertical pumping in the wake; these results are consistent with observations of nutrient uplift and biological enhancement (the "island mass effect") in the vicinity of the island in February, 1993. Numerical sensitivity experiments demonstrate that incident flow speed, background rotation rate and coastal island geometry each have a strong controlling influence on wake formations. Increasing the background rotation rate reduces the frequency of eddy shedding, while disproportionately increasing the circulation strength within shed eddies. For the biologically important non-shedding flow scenario, Lagrangian wake characteristics are examined in detail using the float-tracking scheme of the numerical model. It is found that unsteadiness severely compromises wake retention of passively drifting particles. Coastal geometry also has a strong controlling influence on wake retention. The numerical experiments suggest that particle retention in island wakes has a "hair trigger" characteristic controlled by incident flow speed and direction. This simple but powerful observation is used as the basis for a new proposal to explain the long-standing recruitment problem of biological oceanography. Good overall agreement... [ABSTRACT FROM AUTHOR]

The plankton larval duration for 100 species of Pacific and Atlantic damselfishes was estimated from daily growth increments on the otolith of juvenile fish collected at various localities between July 1987 and September 1988. For newly-settled fishes, larval duration was determined by counting the entire number of increments present on the otolith, while for older juveniles estimates were made by counting the number of increments between the center of the otolith and a mark corresponding to settlement. We document the development of otolith formation during the period when eggs are incubated on the reef and show that daily increments are only accreted after larvae hatch and enter the planktonic phase. The planktonic larval duration for damselfish is shorter and less variable, both between and within species, compared to other groups of reef fishes such as wrasses and surgeonfishes. Larval duration ranged from 12 to 39 d. Average duration between species ranged from 13.1 to 35.2 d. The time spent in the plankton was not significantly correlated with geographic distribution when evaluated among species, however, genera with confined regional distribution have a shorter mean larval life than do widely distributed genera. Size at settlement was positively correlated with time spent in the plankton among species, but a significant correlation between these variables was only evident within one of ten species. The low variance in planktonic larval duration within species indicates that most damselfish are unable to delay metamorphosis following competency. This inability to postpone settlement limits the potential for dispersal, especially when dispersal time between suitable habitats is greater than about 30 d. [ABSTRACT FROM AUTHOR]