Fine scale spatial correlations between planktonic ciliates and dinoflagellates

Fine scale spatial distributions of planktonic ciliates whichprey on dinoflagellates were investigated in a small estuary.The horizontal distributions of Favella sp., Balanion sp. andStrobilidium sp. were positively correlated with the patchydistribution of dinoflagellates. The vertical distribution ofFavella was positively corrdated with the distribution of dinoflagellates.Throughout the diel cycle, the vertical distribution of Faveilawas similar to the vertical distribution of dinoflagellates.We speculate that behavioral responses are responsible for theassociation of diliates with their prey in the water column.Vertically coincident ciliate and algal populations should respondsimilarly to turbulent mixing and water displacement causedby wind stress, bathymetry, or frontal convergences. This wouldresult in horizontal patches in which the ciliates and algaeremain associated. This fine scale spatial coupling betweenciliates and their prey should result in higher ciliate growthrates and greater impact of ciliate grazing on phytoplanktonpopulations than would be predicted from average ciliate oralgal densities. Coincident patches of algae and ciliates mayalso provide higher food concentrations for larger grazers whichcan use both resources. ^{Contribution No. 5532, W.H.O.I.}     

Temporal pattern of feeding response of Chaoborus larvae to starvation

The effect of starvation on the feeding rate of larval Chaoborus(Diptera. Chaoboridae) was investigated using Daphnia roseaas prey. The starvation period varied from 12 h to 22 days.The starved Chaoborus were individually incubated with 10 Daphniaunder controlled light and temperature conditions. Observationswere made on prey mortality every 2 h for the first 12 h andonce after 24 h. Feeding rates gradually increased to a maximumbetween 7–11 days of starvation. After this period, feedingrates declined to previous low levels. Generally, feeding rateswere significantly higher during the first 2–4 h of feeding.Thereafter, feeding rates were lower and exhibited no consistentpattems with length of feeding time.     

Feeding, prey selection and prey encounter mechanisms in the heterotrophic dinoflagellate Noctiluca scintillans

The heterotrophic dinoflagellate Noctiluca scintillans has anegligible swimming ability and feeds predominantly on immobileprey. How, then, does it encounter prey? Noctiluca scintillansis positively buoyant and, therefore, we hypothesized that itintercepts prey particles during ascent and/or that microscaleshear brings it into contact with prey. Noctiluca scintillanshas a specific carbon content 1–2 orders of magnitudeless than that typical for protists and, thus, an inflated volume.It also has a density slightly less than that of the ambientwater and therefore ascends at high velocities (-1 m h^–1).In stagnant water, clearance rates of latex spheres (5–80µm) increased approximately with prey particle size squared.This scaling is consistent with N.scintillans being an interceptionfeeder. However, absolute clearance rates were substantiallylower than those predicted by modeling N.scintillans both asa spherical and as a cylindrical collector. The latter modelassumes that prey particles are collected on the string of mucusthat may form at the tip of the tentacle. Feeding, growth andprey selection experiments all demonstrated that diatoms arecleared at substantially higher rates than latex beads and otherphytoplankters, particularly dinoflagellates. We propose thatdiatoms stick more efficiently than latex beads to the mucusof N.scintillans and that dinoflagellates reduce fatal contactbehaviorally. We conclude that N.scintillans is an interceptionfeeder and that the high ascent velocity accounts for encounterswith prey. However, the flow field around the cell-mucus complexis too complicated to be described accurately by simple geometricmodels. Fluid shear (0.7–1.8 s^–1 had a negativeimpact on feeding rates, which were much less than predictedby models. Noctiluca scintillans can survive starvation forlong periods (>3 weeks), it can grow at low concentrationsof prey (-15 µg C l^–1), but growth saturates onlyat very high prey concentrations of 500–1000 µgC l^–1 or more. We demonstrate how the functional biologyof N.scintillans is consistent with its spatial and seasonaldistribution, which is characterized by persistence in the plankton,blooms in association with high concentrations of diatoms, andsurface accumulation during quiescent periods or exponentialdecline in abundance with depth during periods of turbulentmixing.     

Trophodynamics of the plankton community at Dogger Bank: predatory impact by larval fish

The trophodynamics of a coastal plankton community were studied,focusing on fish larvae and their copepod prey. The major objectiveswere to describe distributional overlap and evaluate the predatoryimpact by larval fish. The study was carried out across DoggerBank in the North Sea, August-September 1991. Sampling transectscrossed tidal fronts off the Bank and plankton at all trophiclevels showed peak abundance within frontal zones. Also Verticallythere was a significant overlap in distributional patterns ofthe plankton. Seven species of fish larvae were abundant, ofthese sprat (Sprattus sprattus) dominated. The abundance ofone group of fish larvae peaked in the shallow water close tothe Bank, whereas other species, including sprat, were foundin deeper water. Prey preference and predation pressure of fishlarvae were assessed using information on prey sizes and growthrates of larvae and the copepod prey. We estimated larval removalof preferred prey sizes to 3–4% day^–1, counterbalancedby a 3–7% day^–1' replenishment from copepod productionand growth. Additional predation pressure on copepods by aninvertebrate predator was estimated to 1–3%day^–1.In conclusion, the dynamics of fish larvae and other zooplankterswere closely linked. At peak abundances of fish larvae (>35mg dry weight m^–2), the accumulated predation on specificsize ranges of copepods, exerted by larvae and other predators,could exceed the ability of copepod replenishment and intra-/interspecificcompetition among predators might take place.     

Vertical migration and habitat partitioning of six euphausiid species in the northern Benguela upwelling system

The vertical distribution of the adults of six species of euphausiids,Thysanöessa gregaria, Nematoscelis megalops, Euphausiaamericana, E.gibboides, E.hanseni, Stylocheiron longicorne,as well as the larval stages of E.hanseni, were studied duringa 48 h cycle at a fixed station in the northern Benguela upwellingsystem. All the species, except T.gregaria and S.longicorne,proved to perform diel vertical migration, but both migratoryand non-migratory species appeared to be segregated in spaceduring night-time hours, regardless of potential prey (phytoplanktonand copepods). It is suggested that water column structure andhydrographic discontinuities caused by a warm, depth-localizedintrusion, as well as the reproductive strategies of particularspecies, are responsible for this pattern. Eggs and larval stagesof E.hanseni were concentrated near the surface, and the effectof the short-term pulses of the intrusion on their abundanceis discussed.     

Effects of temporary food limitation on survival and development of brachyuran crab larvae

As a consequence of the combined effects of prey patchinessand diel or tidal vertical migrations in the water column, decapodcrustacean larvae may experience temporal or spatial variabilityin the availability of planktonic food. In a laboratory study,we evaluated effects of temporarily limited access to prey onthe larvae of three species of brachyuran crabs, Chasmagnathusgranulata, Cancer pagurus and Carcinus maenas. Stage-I zoeaewere fed ad libitum for 4 or 6 h per day (20 or 25% treatments;6 h tested in C. pagurus only), and rates of larval survivaland development were compared with those observed in continuouslyfed control groups (24 h, 100%). In C. granulata, we also testedif intraspecific variability in initial biomass of freshly hatchedlarvae originating from different broods has an influence onearly larval tolerance of food limitation. Moreover, we exposedembryos and larvae of this estuarine species to moderately decreasedsalinities to identify possible interactions of osmotic andnutritional stress. Finally, we evaluated in this species theeffect of food limitation on survival from hatching throughall larval instars to metamorphosis. In all three species, limitedaccess to prey had only weak or insignificant negative effectson survival through the Zoea-I stage. The strength of the effectsof temporary food limitation varied in C. granulata significantlyamong broods. However, no significant relationships were foundbetween initial larval biomass (C content) and either survivalor development duration. Strongly decreased survival to metamorphosiswas found when food limitation continued throughout larval development.Thus, early brachyuran crab larvae are well adapted to transitorylack of planktonic food. The capability of the Zoea-I stageof C. granulata to withstand nutritional stress also under conditionsof concomitant salinity stress allows them to exploit variousbrackish environments within estuarine gradients. However, continuedexposure to limited access to planktonic prey may exceed thenutritional flexibility of C. granulata larvae.     

Microscale patchiness of plankton within a sharp pycnocline

Microscale distributions of plankton around the pycnocline werestudied over a 24 h period in the southern Kattegat, using agradient sampler which collects 20 samples over a 3 m depthinterval. Moderately elevated concentrations of phyto- and zooplanktonwere observed at the pycnocline. Microscale variance was highestfor adult copepods. Nauplii and copepodites were equally wellrepresented by sampling with ordinary vertical 5 1 water bottlesas with the horizontal 1.5 1 bottles of the gradient sampler.Adult copepods were underestimated by the vertical bottles.No vertical migration of dinoflagellates was observed over the3 m interval covered by the gradient sampler. Microscale correlationsbetween copepods and phytoplankton within the gradient samplerwere weak. Copepodites (mainly Oithona sp.) and the dinoflagellateProrocentrum micans showed the best correlation.     

Differential use of zooplankton prey by Ancient murrelets and Cassin's auklets in the Queen Charlotte Islands

The distribution at sea and the food of two similar sized plankton-feedingalcids were examined during the 1981 breeding seasons in thenorthwestern Queen Charlotte Islands, British Columbia. Thetwo alcids, the Ancient murrelet (Synthliboramphus antiquus)and the Cassin's auklet (Prychoramphus aleuticus) have differentchick-rearing strategies. Both species fed predominantly atthe shelf break, although the Cassin's auklet also foraged overseamounts. The feeding distributions of the species appear tobe related to those of their prey. Zooplankton sampling indicatedthat each alcid selects a small and different portion of thezooplankton available in surface waters. The Ancient murrelet'smain foods were euphausiids (Thysanoessa spinifera and Euphausiapacifica) and larval and juvenile fishes. The Cassin's aukletchicks fed chiefly on calanoid copepods (Neocalanus cristatus).euphausiids (mostly Thysanoessa longipes in 1981, but in otheryears also Thysanoessa spinifera), and larval and juvenile fishes.The Cassin's auklets took smaller prey than the Ancient murrelet.Differences in the diets of the two alcid species were associatedwith differences in morphology and chick-rearing strategies.     

Simultaneous measurements of small-scale physical dynamics and zooplankton distributions

Haury et al., (Deep Sea Res., 37, 447–461, 1990) describedhow turbulence and vertical shear generated by the passage ofa storm affected the vertical distributions and community structureof plankton in Monterey Bay, CA. The data presented came froma larger set of five plankton recorder collections of zooplankton,taken together with temperature, salinity, turbulent kineticenergy dissipation rate, and vertical current shear data onthe research submarine Dolphin. Here we report on the analysisof the whole data set, which represents a wide range of physicaldynamic conditions. While the overall community structure remainedrelatively constant over the sampling period, the relationshipsbetween taxonomic categories and between categories and thephysical dynamics were complex and variable; factors relatedto depth were the most important. During periods of weak winds(low kinetic energy conditions) some of the biological variabilityappeared to be related to the level of turbulent dissipation.Other relationships were not detected due to the limitationsof the plankton sampler and its interactions with the highlyvariable biological and physical conditions. In view of thesedifficulties, we recommend that future field investigationsof the relationships between physical parameters and zooplanktondistributions make greater use of acoustic and other remote-sensingtechnologies, preferably in combination with numerical simulationstudies to help guide and interpret the field work.     

Feeding by marine fish larvae: developmental and functional responses

Synopsis The relationship between prey consumption rate and prey concentration (functional response), and its change with growth (developmental response) were examined in the laboratory for three species of marine fish larvae: bay anchovy Anchoa mitchilli (Engraulidae), sea bream Archosargus rhomboidalis (Sparidae) and lined sole Achirus lineatus (Soleidae). The major objective was to determine relative predatory abilities of the larvae by fitting feeding rate data to developmental and functional response models. Feeding success, prey capture success, attack rates, handling times and search rates were estimated. Prey consumption rates and attack rates of bay anchovy usually were highest, but at the lowest prey level (50 per liter) first-feeding sea bream larvae had the highest consumption rate. Sea bream could consume prey at near-maximum rates at prey levels lower than those required by the other species. As larvae grew, time searching per attack decreased rapidly for all species, especially at low prey levels. Handling time also decreased, but most rapidly for bay anchovy. Search rates were highest for bay anchovy and lowest for lined sole. Bay anchovy had the best apparent predation ability, but when previous results on larval growth rates, survival rates and growth efficiencies were considered, sea bream larvae were the most efficient predators and the least likely of the three species to be limited by low prey levels.     

Relating the ontogeny of functional morphology and prey selection with larval mortality in Amphiprion frenatus

Survival during the pelagic larval phase of marine fish is highly variable and is subject to numerous factors. A sharp decline in the number of surviving larvae usually occurs during the transition from endogenous to exogenous feeding known as the first feeding stage in fish larvae. The present study was designed to evaluate the link between functional morphology and prey selection in an attempt to understand how the relationship influences mortality of a marine fish larva, Amphiprion frenatus, through ontogeny. Larvae were reared from hatch to 14 days post hatch (DPH) with one of four diets [rotifers and newly hatched Artemia sp. nauplii (RA); rotifers and wild plankton (RP); rotifers, wild plankton, and newly hatched Artemia nauplii (RPA); wild plankton and newly hatched Artemia nauplii (PA)]. Survival did not differ among diets. Larvae from all diets experienced mass mortality from 1 to 5 DPH followed by decreased mortality from 6 to 14 DPH; individuals fed RA were the exception, exhibiting continuous mortality from 6 to 14 DPH. Larvae consumed progressively larger prey with growth and age, likely due to age related increase in gape. During the mass mortality event, larvae selected small prey items and exhibited few ossified elements. Cessation of mass mortality coincided with consumption of large prey and ossification of key elements of the feeding apparatus. Mass mortality did not appear to be solely influenced by inability to establish first feeding. We hypothesize the interaction of reduced feeding capacities (i.e., complexity of the feeding apparatus) and larval physiology such as digestion or absorption efficiency contributed to the mortality event during the first feeding period. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

Vertical Distribution and Feeding Activity of Metamorphosing Sole, Solea Solea, Before Immigration to the Bay of Vilaine Nursery (Northern Bay of Biscay, France)

To evaluate the impact of metamorphosis on the vertical distribution and feeding activity of sole, Solea solea, larvae passing from offshore spawning grounds to the Bay of Vilaine, sampling series at fixed stations were carried out in April 1991 and April 1993 at depths from 50 to 30 m. Comparisons between plankton and bottom samplin series indicated differences in vertical distribution of larvae in pre-metamorphic and metamorphic steps. Metamorphosing larvae displayed a tendency to concentrate in the lower part of the water column, mainly during the day. Gut contents, analysed for prey identification, fullness index and carbon content, indicated that metamorphosing larvae fed mostly on plankton. Variations in fullness index were observed not only during the day, but also depended on tide and wind-induced mixing conditions. Larvae sampled in mixed spring-tide waters had highly variable carbon estimates, resulting in unclear diel activity. More larvae fed actively at neap-tide, which allowed the observation of a diurnal feeding activity through hourly changes in carbon estimates. It is concluded that immigrating sole were not yet able to settle but prepared themselves for demersal life (i) without undergoing starvation and (ii) by modifying the patterns of vertical distributions. The presence of a larval swimbladder suggests they can adjust their vertical movements, depending on tidal cycles, which could in turn favour coastal accumulation of metamorphosing larvae and pulses of new settlers entering the nursery grounds.     

Laboratory studies of predation by the ctenophore Mnemiopsis leidyi on the early stages in the life history of the bay anchovy, Anchoa mitchilli

The lobate ctenophore, Mnemiopsis leidyi, consumed eggs andlarvae of the bay anchovy, Anchoa mitchilli, in laboratory experiments.This ctenophore exhibited a type I functional response to increasesin egg densities without reaching saturation at high prey densities.Clearance rate increased with increasing experimental containervolume. There was a 3-fold increase in the volume of water clearedby 2.0–2.5-cm ctenophores and a >5-fold increase for4.5–5.0-cm ctenophores in 15–1 versus 100–200–1containers. Clearance rate was dependent on tenophore lengthbut was probably underestimated for the larger animals due tocontainer effects. The presence of various densities of alternateprey, Acartia hudsonica or Anemia sp. nauplii, in addition toAnchoa mitchilli eggs did not affect the clearance rates onthe eggs alone. Comparison of clearance rates of 2.0–2.5-cmctenophores on various ages of starved and fed bay anchovy larvaeindicated that predation may be higher on yolk-sac larvae thanon eggs but decreases as the larvae grow. After 3 days posthatch starved anchovy larvae become more vulnerable to predationthan fed larvae. The ctenophore, M.leidyi has the potentialto inflict substantial predation pressure on early stages inthe life history of bay anchovy. ¹ Present address: University of Maryland, Center for Environmentaland Estuarine Studies, Chesapeake Biological Laboratory, POBox 38, Solomons, MD 20688-0038, USA     

Effects of vertical-horizontal coupling on the horizontal distribution of chlorophyll a

The distributions of chlorophyll a and salinity were sampledon successive days along horizontal transects in central LongIsland Sound. Changes in the variance spectra over a periodof three days following a wind event suggest that there wasan input of variance at wave numbers of the order 6 ? 10^–3radians per meter. There was an associated increase in coherencysquared between chlorophyll and salinity. During this periodvertical structure in both chlorophyll and salinity was reestablished.It appears that horizontal structure was generated by the interactionof this vertical structure with a vertical shear in horizontalcurrents at semidiurnal and lower frequencies and possibly byshort period internal waves with frequencies near the V?is?l?frequency.     

Selective feeding by protozoa: model and experimental behaviors and their consequences for population stability

Selective feeding by zooplankton can have profound consequencesfor the stability of grazer and prey populations, as demonstratedby the behavior of plankton dynamics models. We present an analyticalapproach—calculation of prey ratio trajectories—thatreveals unambiguously whether selective feeding behavior isstabilizing (i.e. provides a refuge for preferred prey speciesat low prey concentrations) or destabilizing (i.e. results inelimination of prey populations). Prey ratio trajectories werecalculated for three modeled selective feeding behaviors. Constantselection was consistently destabilizing, while selection behaviorsthat changed inresponse to either prey ratio or prey abundancecould be stabilizing. Batch culture experiments with four protozoangrazer species (three ciliates, one heterotrophic dinoftagellate)demonstrated that protozoa fed selectively in every case, weaklypreferring the larger of the two algal species offered. Stabilizingselection was observed only in the experiment with Favella sp.,however, meaning that only this species altered its selectionbehavior in response to changing experimental conditions. Becauseprotozoa are the major grazers of phytoplankton in many planktonicsystems, our findings indicate that the use of selective feedingbehaviors to stabilize plankton dynamics models needs carefulevaluation. The modeling and graphical techniques presentedhereare a tool for linking further exploration of selective feedingbehaviors with the development of planktondynamics models.     

Growth,Grazing, and Starvation Survival in Three Heterotrophic Dinoflagellate Species

To assess the effects of fluctuating prey availability on predator population dynamics and grazing impact on phytoplankton, we measured growth and grazing rates of three heterotrophic dinoflagellate species—Oxyrrhis marina, Gyrodinium dominans and Gyrodinium spirale—before and after depriving them of phytoplankton prey. All three dinoflagellate species survived long periods (> 10 d) without algal prey, coincident with decreases in predator abundance and cell size. After 1–3 wks, starvation led to a 17–57% decrease in predator cell volume and some cells became deformed and transparent. When re‐exposed to phytoplankton prey, heterotrophs ingested prey within minutes and increased cell volumes by 4–17%. At an equivalent prey concentration, continuously fed predators had ~2‐fold higher specific growth rates (0.18 to 0.55 d^?1) than after starvation (?0.16 to 0.25 d^?1). Maximum specific predator growth rates would be achievable only after a time lag of at least 3 d. A delay in predator growth poststarvation delays predator‐induced phytoplankton mortality when prey re‐emerges at the onset of a bloom event or in patchy prey distributions. These altered predator‐prey population dynamics have implications for the formation of phytoplankton blooms, trophic transfer rates, and potential export of carbon.     

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.     

Effects of prey size structure and turbulence on feeding and growth of anchovy larvae

Foraging processes in plankton and planktivorous fish are constrained by relative prey and predator size and therefore, these are important variables to include in a foraging model. The distribution of prey biomass across different size classes can be characterized by a size spectrum slope. We present a foraging model for anchovy larvae including the most relevant processes such as prey encounter, capture- and pursuit success, all influenced by light, turbulence and prey characteristics. We modelled ingestion rates and specific growth rate by coupling the foraging model with an existing bioenergetic model, and performed a sensitivity analysis of prey ingestion in turbulent environments assuming either hemispherical or conical perceptive volume. Our results suggest that turbulence has no positive effect because of the low capture ability, small prey size and small visual volume for anchovy larvae. The predicted ingestion is too low to sustain the growth potential of larvae when assuming conical perceptive volume even under prey densities substantially higher than normally found in the field. Ingestion rate is sensitive to the total biomass and the slope of the prey size spectra, specifically because it determines the abundance of prey around the optimal size for the larvae. The model also suggests that small larvae benefit from a prey size structure with steep prey size-spectra slope while a large larva benefit from less steep slopes. The model can act as a link between size-spectra measurements from the field and the foraging conditions of larval anchovies.     

Microzooplankton, vertical mixing and advection in a larval fish patch

A large ({small tilde}30 ? 75 km) patch of larval walleye pollock,Theragra chalcogramma, was located south of the Alaska Peninsuladuring May 1986. A drifter deployed in this patch followed ananticyclonic path consistent with dynamic topography. Changesin community composition and vertical distribution of microzooplankton>40 µm were sampled for 4 days alongside this drifterto examine feeding conditions for larvae. Biological and physicalchanges during the first 2 calm days revealed substantial small-scalevariability within the larger circulation pattern. Changes duringthe last 2 days were dominated by vertical mixing due to strongwinds. Despite mixing, prey concentrations remained adequatefor feeding by larval pollock as determined by laboratory studies.A satellite-tracked drifter replaced the first drifter and wasstill located within the patch 6 days later. Overall distributionsof larvae and movements of the drifters show a net translationof 7.8 km day^–1 south-westward, but details of the studyreveal complex interactions between coastal waters and a coastalcurrent. During the 10-day period there was an increase in standardlength of the larval fish population of 0.13 mm day^–1and a decline in abundance of {small tilde}7.6% day^–1.Both calculated rates must be underestimates due to continuingrecruitment of small larvae from hatching eggs.     

Influence of environmental variables on the larval stages of anchovy, <Emphasis Type="Italic">Engraulis encrasicolus</Emphasis>, and sardine, <Emphasis Type="Italic">Sardinops sagax</Emphasis>, in Algoa Bay,South Africa

We investigated the environmental drivers of larval abundance of anchovy Engraulis encrasicolus and sardine Sardinops sagax in Algoa Bay, Eastern Cape (South Africa). This study comprised a pre-drought post-drought time period, comparing the responses of the fish larvae to different factors before and after the drought. The current study presents, for the first time, which environmental variables are affecting the anchovy and sardine larvae populations in the region. Easterly wind speed and zooplankton density were the only environmental variables that presented a significant change between the pre- and post-drought periods, increasing after the drought. Generalized additive models (GAMs) were used in order to explore the effects that environmental factors might have in the abundance of anchovy and sardine larvae in Algoa Bay. Specifically, the GAM that best explained the deviance of the anchovy larvae dynamics included the covariates rainfall, easterly wind speed, Chl a concentration, sardine larvae abundance and the interactions SST*Chla and sard*SST. The GAM best explaining sardine larvae abundance included only the easterly wind speed as a covariate. This model showed that there was a positive relationship between the higher values of wind speed and sardine larvae abundance.