Distribution by Scientific Domains

Kinds of Anchovy

  • european anchovy

  • Selected Abstracts

    Environmental ,loopholes' and fish population dynamics: comparative pattern recognition with focus on El Niño effects in the Pacific

    Andrew Bakun
    Abstract A process of comparative pattern recognition is undertaken for the purpose of garnering insights into the mechanisms underlying some currently puzzling conundrums in fishery resource ecology. These include (a) out-of-phase oscillations between anchovies and sardines, (b) the remarkable fish productivity of the Peru,Humboldt marine ecosystem, (c) sardine population increases in the eastern Pacific during El Niños, (d) basin-wide synchronies in large-amplitude abundance variations, (e) characteristic spawning of large tuna species in poorly productive areas, (f) contrary trends in Pacific tropical tuna abundance during the 1970s and early 1980s. It is found that each of the items appears to become less enigmatic when the conceptual focus shifts from conventional trophodynamics to the idea that ,loopholes' in the fields of biological controls (i.e. of predators of early life stages), produced by poor ocean productivity or by disruptive environmental perturbations, may in fact lead to remarkable reproductive success. Implications include the following: (1) El Niño, rather than being an unmitigated disaster for Peruvian fisheries, may in the long run be a prime reason for the remarkable fishery productivity of the Peru,Humboldt large marine ecosystem. (2) Globally-teleconnected climatic trends or shifts might produce globally-coherent population expansions even when local environmental expressions may be quite different. (3) It may be unreasonable to expect any management methodologies to be able to keep the fish populations of highly climatically-perturbed systems such as the Peruvian LME always at stable high levels; an alternative approach, for example, might be to take optimal advantage of the transient opportunities afforded by the high fish productivity of such inherently erratic systems. [source]


    ABSTRACT Histamine formation in Sardina pilchardus and Engraulis encrasicolus as a function of storage temperature was studied. Fish were caught off the Adriatic Coast and were carried immediately to the laboratory. A portion of dorsal muscle from each fish was soon analyzed, while two other portions were examined after storage at two different temperatures (25 and 4C) for 24 and 72 h, respectively. The analyses were carried out by high-performance liquid chromatography (HPLC)-UV and confirmed by HPLC-diode array detector. Histamine concentrations were always higher than the European Community admissible levels in samples stored at 25C. In fish stored at 4C, histamine was detected only in E. encrasicolus. PRACTICAL APPLICATIONS Time experiments were conducted to quantify the histamine formation in scombroid species at two different temperatures. The first assay (24 h, 25C) could reproduce the modality of sale adopted by fishermen or retailers in summer on the one hand, and the maintenance at ambient temperature of semipreserved sardines or anchovies during salting and ripening on the other hand. The second experiment (72 h, 4C) was based on the domestic cold preservation of fish before the consumption, which sometimes occurs some days after purchasing. Even if ice storage is recommended, time/temperature abuse conditions often occur in the fish merchandising chain. The results of this research showed that high histamine concentrations could be found in the analyzed species not only at an abused temperature, but also at a common storage temperature of fish at home. [source]

    Characterization of the Swimming Muscle of the Anchovy Engraulis anchoita (Hubbs & Martini 1935)

    C. V. Devincenti
    The lateral muscle characteristics of individual female anchovies (Engraulis anchoita) were studied by histochemical and ultrastructural techniques. Red, pink and white fibres were discerned on the basis of the activity of the metabolic enzymes succinic dehydrogenase, phosphorylase and myofibrilar ATPase, and the usage of Sudan and periodic-acid Schiff staining techniques. Red fibres were located at the surface, white fibres deep inside and pink fibres in between. The red fibres appeared flattened or ribbon-shaped in transverse section and they were located in rows separated by myosepta of connective tissue. The red and pink fibres were multi-innervated whereas the white fibres were terminally innervated. The relative proportion of the red muscle increased toward the caudal region, the white muscle diminished toward that region, whereas the proportion of pink muscle did not vary according to region, being scarce throughout. The distribution of capillaries was also investigated, and as a result, the vascular supply proved to be scarce in both white and pink muscle. [source]

    From small-scale habitat loopholes to decadal cycles: a habitat-based hypothesis explaining fluctuation in pelagic fish populations off Peru

    FISH AND FISHERIES, Issue 4 2004
    Arnaud Bertrand
    Abstract The Peru-Humboldt Current system (HCS) supports the world's largest pelagic fisheries. Among the world's eastern boundary current systems, it is the most exposed to high climatic stress and is directly affected by El Niño and La Niña events. In this volatile ecosystem, fish have been led to develop adaptive strategies in space and time. In this paper, we attempt to understand the mechanisms underlying such strategies, focusing on the El Niño 1997,98 in Peru from which an extensive set of hydrographic, capture and acoustic survey data are available. An integrated analysis of the data is crucial, as each has substantial shortcomings individually; for example, both catch data and acoustic surveys may easily lead to wrong conclusions. Existing hypotheses on anchovy and sardine alternations lead us to a ,habitat-based' synthetic hypothesis. Using our data, an integrated approach evaluated how fish responded to habitat variation, and determined the consequences in terms of fish-population variability. Various factors occurring at a range of different spatio-temporal scales were considered: interdecadal regime (warm ,El Viejo'/cool ,La Vieja' decadal scale); strength and the duration of the El Niño Southern Oscillation event (interannual scale); population condition before the event (interannual scale); fishing pressure and other predation (annual scale); changes in reproductive behaviour (intra-annual scale); presence of local upwelling (local scale). During El Niño 1997,98, anchovy was able to exploit a small-scale temporal and spatial ,loophole' inside the general unfavourable conditions. Moreover, sardine did not do better than anchovy during this El Niño and was not able to take advantage of the ,loophole' opened by this short-term event. Our results question the traditional view that El Niño is bad for anchovy and good for sardine. [source]

    Growth and movement patterns of early juvenile European anchovy (Engraulis encrasicolus L.) in the Bay of Biscay based on otolith microstructure and chemistry

    Abstract Various hypotheses have been put forward to explain the mechanisms in the Bay of Biscay that result in a good recruitment of European anchovy. Anchovy larvae from the spawning area in the Gironde River plume are advected towards off-shelf waters, where juveniles are commonly observed. Otolith microstructural and chemical analysis were combined to assess the importance of this off-shelf transport and to determine the relative contribution of these areas for anchovy survival. Chemical analysis of otoliths showed that anchovy juveniles in the Bay of Biscay can be divided into two groups: a group that drifts towards off-shelf waters early in their life and returns later, and a group that remains in the low salinity waters of the coastal area. The first group presents significantly faster growth rates (0.88 mm day,1) than those remaining in the coastal waters (0.32 mm day,1). This may be due to off-shelf waters being warmer in spring/summer, and to the fact that the lower food concentration is compensated for by higher prey visibility. Furthermore, the group of juveniles that drifted off the spawning area and had faster growth rates represents 99% of the juvenile population. These findings support the hypothesis that anchovy in the Bay of Biscay may use off-shelf waters as a spatio-temporal loophole, suggesting that transport off the shelf may be favourable for recruitment. [source]

    Acoustic characterization of biological backscatterings in the Kuroshio-Oyashio inter-frontal zone and subarctic waters of the western North Pacific in spring

    Abstract The acoustic characteristics of biological backscattering in the western North Pacific were studied to verify expert knowledge on species composition in the echosigns. The survey was conducted in the Kuroshio-Oyashio inter-frontal zone and the subarctic waters in April 2003. The species composition of backscatterings was identified by using midwater trawl, Isaacs-Kidd midwater trawl and Bongo net. The differences of mean volume backscattering strengths between 120 and 38 kHz (,MVBS120,38) were calculated for the backscatterings. Six types of backscatterings were classified based on the results of net samples and the ,MVBS120,38. The ,MVBS120,38 of each group was as follows: copepods 13.7,17.3 dB, krill 11.6,15.3 dB, Japanese anchovy ,1.6 to 1.1 dB, a myctophid, Diaphus theta,0.8 dB, sand lance 6.1 dB and larvae and juveniles of pelagic and mesopelagic fish ,9.6 to ,4.0 dB. The results suggest that biological backscatterings in the Kuroshio-Oyashio inter-frontal zone and subarctic waters of the western North Pacific in spring can be characterized by using ,MVBS. [source]

    Time series analyses reveal transient relationships between abundance of larval anchovy and environmental variables in the coastal waters southwest of Taiwan

    Abstract We investigated environmental effects on larval anchovy fluctuations (based on CPUE from 1980 to 2000) in the waters off southwestern Taiwan using advanced time series analyses, including the state-space approach to remove seasonality, wavelet analysis to investigate transient relationships, and stationary bootstrap to test correlation between time series. For large-scale environmental effects, we used the Southern Oscillation Index (SOI) to represent the El Niño Southern Oscillation (ENSO); for local hydrographic conditions, we used sea surface temperature (SST), river runoff, and mixing conditions. Whereas the anchovy catch consisted of a northern species (Engraulis japonicus) and two southern species (Encrasicholina heteroloba and Encrasicholina punctifer), the magnitude of the anchovy catch appeared to be mainly determined by the strength of Eng. japonicus (Japanese anchovy). The main factor that caused the interannual variation of anchovy CPUE might change through time. The CPUE showed a negative correlation with combination of water temperature and river runoff before 1987 and a positive correlation with river runoff after 1988. Whereas a significant negative correlation between CPUE and ENSOs existed, this correlation was driven completely by the low-frequency ENSO events and explained only 10% of the variance. Several previous studies on this population emphasized that the fluctuations of larval anchovy abundance were determined by local SST. Our analyses indicated that such a correlation was transient and simply reflected ENSO signals. Recent advances in physical oceanography around Taiwan showed that the ENSOs reduced the strength of the Asian monsoon and thus weakened the China Coastal Current toward Taiwan. The decline of larval anchovy during ENSO may be due to reduced China Coastal Current, which is important in facilitating the spawning migration of the Japanese anchovy. [source]

    Transport and environmental temperature variability of eggs and larvae of the Japanese anchovy (Engraulis japonicus) and Japanese sardine (Sardinops melanostictus) in the western North Pacific estimated via numerical particle-tracking experiments

    Abstract Numerical particle-tracking experiments were performed to investigate the transport and variability in environmental temperature experienced by eggs and larvae of Pacific stocks of the Japanese anchovy (Engraulis japonicus) and Japanese sardine (Sardinops melanostictus) using high-resolution outputs of the Ocean General Circulation Model for the Earth Simulator (OFES) and the observed distributions of eggs collected from 1978 to 2004. The modeled anchovy individuals tend to be trapped in coastal waters or transported to the Kuroshio,Oyashio transition region. In contrast, a large proportion of the sardines are transported to the Kuroshio Extension. The egg density-weighted mean environmental temperature until day 30 of the experiment was 20,24°C for the anchovy and 17,20°C for the sardine, which can be explained by spawning areas and seasons, and interannual oceanic variability. Regression analyses revealed that the contribution of environmental temperature to the logarithm of recruitment per spawning (expected to have a negative relationship with the mean mortality coefficient) was significant for both the anchovy and sardine, especially until day 30, which can be regarded as the initial stages of their life cycles. The relationship was quadratic for the anchovy, with an optimal temperature of 21,22°C, and linear for the sardine, with a negative coefficient. Differences in habitat areas and temperature responses between the sardine and anchovy are suggested to be important factors in controlling the dramatic out-of-phase fluctuations of these species. [source]

    From egg to juvenile in the Bay of Biscay: spatial patterns of anchovy (Engraulis encrasicolus) recruitment in a non-upwelling region

    Abstract In this study the spatial distribution of eggs, larvae and juveniles of European anchovy (Engraulis encrasicolus) was followed in 2004 and 2005 during three consecutive cruises each year in spring,summer to test what the limits of retention are in a non-upwelling area. Eggs, small larvae and large juveniles were mainly distributed over the shelf, whereas large larvae and small juveniles were found mainly off the shelf. Although overall distributions were similar, the 2 yr differed in that there was more of a coastal distribution of individuals in 2004, whereas in 2005 more individuals were found off the shelf. There were no significant differences in the length,weight relationships for individuals found on and off the shelf or between years. The correspondence in circulation patterns and the lack of difference in the length,weight relationships suggest that a single population is present, larvae drifting off the shelf due to currents and returning as mobile juveniles. Quantile regression analysis of the long-term recruitment index suggests that transport off the shelf may favour good recruitments. This would suggest that in non-upwelling regions the retention area resulting in good recruitment may not be restricted to the shelf. [source]

    The influence of environment and spawning distribution on the survival of anchovy (Engraulis encrasicolus) larvae in the Bay of Biscay (NE Atlantic) investigated by biophysical simulations

    Abstract A growth and survival model of the early life stages was run along virtual drift trajectories tracked in a hydrodynamic model to simulate the annual recruitment process of anchovy (Engraulis encrasicolus) in the Bay of Biscay (NE Atlantic). These biophysical simulations concerning three different years were analysed in order to investigate the influence of environment and spawning dynamics on the survival of larvae and juveniles. The location of space,time survival windows suggested major environmental mechanisms involved in simulated recruitment variability at the different scales , retention of larvae and juveniles in favourable habitats over the shelf margins and turbulence effects. These small-scale and meso-scale mechanisms were related to the variations in wind direction and intensity during spring and summer. Survival was also variable according to the origin of the drift trajectories, that is spawning distribution in space and time. The observed spawning distribution (according to field surveys) was compared with the spawning distribution that would maximize survival (according to the biophysical model) on a seasonal scale, which revealed factors not considered in the biophysical model (e.g. spawning behaviour of the different age classes). The variation of simulated survival according to spawning distribution was examined on a multi-annual scale and showed a coherent pattern with past and present stock structures. The interaction processes between the population (influence on spawning) and its environment (influence on survival) and its implications on recruitment and stock dynamics are discussed. [source]

    Advection of anchovy (Engraulis encrasicolus) larvae along the Catalan continental slope (NW Mediterranean)

    Abstract The Gulf of Lions is one of the main anchovy (Engraulis encrasicolus) spawning areas in the NW Mediterranean. During the spring, low-salinity surface water from the outflow of the Rhône is advected by the shelf-slope current along the continental slope off the Catalan coast. In June 2000, a Lagrangian experiment tracking these low-salinity surface waters was conducted to assess the importance of this transport mechanism for anchovy larvae and to determine the suitability of the tracked surface waters for survival of anchovy larvae. The experiment consisted of sampling the tracked water parcel for 10 days with three drifters launched at the core of the shelf-slope current where low-salinity surface waters were detected. The survey was completed by sampling the surrounding waters. Anchovy larvae from the spawning area in the Gulf of Lions were advected towards the south in the low-salinity waters. The size increase of anchovy larvae throughout the Lagrangian tracking closely followed the general growth rate calculated by otolith analysis (0.65 mm day,1). However, advection by the current was not the only mechanism of anchovy larval transport. A series of anticyclonic eddies, originated in the Gulf of Lions and advected southwards, seemed to play a complementary role in the transport of larvae from the spawning ground towards the nursery areas. These eddies not only contributed to larval transport but also prevented their dispersion. These transport and aggregation mechanisms may be important for anchovy populations along the Catalan coast and require further study. [source]

    Modelling potential spawning habitat of sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) in the Bay of Biscay

    Abstract Large amplitude variations in recruitment of small pelagic fish result from interactions between a fluctuating environment and population dynamics processes such as spawning. The spatial extent and location of spawning, which is critical to the fate of eggs and larvae, can vary strongly from year to year, as a result of changing population structure and environmental conditions. Spawning habitat can be divided into ,potential spawning habitat', defined as habitat where the hydrographic conditions are suitable for spawning, ,realized spawning habitat', defined as habitat where spawning actually occurs, and ,successful spawning habitat', defined as habitat from where successful recruitment has resulted. Using biological data collected during the period 2000,2004, as well as hydrographic data, we investigate the role of environmental parameters in controlling the potential spawning habitat of anchovy and sardine in the Bay of Biscay. Anchovy potential spawning habitat appears to be primarily related to bottom temperature followed by surface temperature and mixed-layer depth, whilst surface and bottom salinity appear to play a lesser role. The possible influence of hydrographic factors on the spawning habitat of sardine seems less clear than for anchovy. Modelled relationships between anchovy and sardine spawning are used to predict potential spawning habitat from hydrodynamical simulations. The results show that the seasonal patterns in spawning are well reproduced by the model, indicating that hydrographic changes may explain a large fraction of spawning spatial dynamics. Such models may prove useful in the context of forecasting potential impacts of future environmental changes on sardine and anchovy reproductive strategy in the north-east Atlantic. [source]

    Simulation and quantification of enrichment and retention processes in the southern Benguela upwelling ecosystem

    Abstract Important environmental processes for the survival and recruitment of early life stages of pelagic fishes have been synthesized through Bakun's fundamental triad as enrichment, concentration and retention processes (A. Bakun, 1996, Patterns in the Ocean. Ocean Processes and Marine Population Dynamics. San Diego, CA, USA: University of California Sea Grant). This conceptual framework states that from favourable spawning habitats, eggs and larvae would be transported to and/or retained in places where food originating from enrichment areas would be concentrated. We propose a method for quantifying two of the triad processes, enrichment and retention, based on the Lagrangian tracking of particles transported within water velocity fields generated by a three-dimensional hydrodynamic model. We apply this method to the southern Benguela upwelling ecosystem, constructing putative maps of enrichment and retention. We comment on these maps regarding main features of the circulation in the region, and investigate seasonal variability of the processes. We finally discuss the results in relation to available knowledge on the reproductive strategies of two pelagic clupeoid species abundant in the southern Benguela, anchovy (Engraulis encrasicolus) and sardine (Sardinops sagax). Our approach is intended to be sufficiently generic so as to allow its application to other upwelling systems. [source]

    Assessing the variability of hydrographic processes influencing the life cycle of the Sicilian Channel anchovy, Engraulis encrasicolus, by satellite imagery

    Abstract Three oceanographic surveys carried out in the Sicilian Channel during the spawning season (June to July) of anchovy (Engraulis encrasicolus) showed a close relationship between anchovy reproductive strategy and important hydrographic structures. A time series of satellite-derived sea surface temperature images of the Sicilian Channel were analysed by means of empirical orthogonal functions and the dominant empirical modes were studied in detail. The first empirical mode captured much of the original variance and reproduced the trajectory of the Atlantic Ionian Stream (AIS), the principal hydrodynamic feature of the area. The time coefficients of modes 1 and 2 had seasonal signals which, when combined, accounted for the enhancement of the thermal front, clearly visible off Cape Passero (southernmost coast of Sicily) during summer. As the area constituted the principal nursery ground of the Sicilian Channel anchovy, the combination of the time coefficients of these modes was considered a potential indicator of the food particle concentration usually associated with oceanic fronts, which provided the energy requirements for larval growth. Mode 3 described the north/south displacements of the mean AIS trajectory, which modified the surface temperature regime of the anchovy spawning habitat. Therefore, the time coefficients of this mode were used as a potential indicator of anchovy spawning habitat variability. The capability of time coefficients of modes 2 and 3 to modify the main pattern depicted by mode 1 were tested successfully against in situ oceanographic observations. [source]

    Relative importance of gulf and shelf waters for spawning and recruitment of Australian anchovy, Engraulis australis, in South Australia

    W. F. Dimmlich
    Abstract Gonosomatic indices and egg and larval densities observed from 1986 to 2001 suggest that the peak spawning season of the Australian anchovy (Engraulis australis) in South Australia occurs during January to March (summer and autumn). This coincides with the spawning season of sardine (Sardinops sagax) and the period when productivity in shelf waters is enhanced by upwelling. Anchovy eggs were abundant throughout gulf and shelf waters, but the highest densities occurred in the northern parts of Spencer Gulf and Gulf St Vincent where sea surface temperatures (SST) were 24,26°C. In contrast, larvae >10 mm total length (TL) were found mainly in shelf waters near upwelling zones where SSTs were relatively low (<20°C) and levels of chlorophyll a (chl a) relatively high. Larvae >15 mm TL were collected only from shelf waters near upwelling zones. The high levels of larval abundance in the upwelling zones may reflect higher levels of recruitment to later stages in these areas compared with the gulfs. The sardine spawns mainly in shelf waters; few eggs and no larvae were collected from the northern gulfs. The abundance of anchovy eggs and larvae in shelf waters increased when sardine abundance was reduced by large-scale mortality events, and decreased as the sardine numbers subsequently recovered. We hypothesize that the upwelling zones provide optimal conditions for the survival of larval anchovy in South Australia, but that anchovy can only utilize these zones effectively when the sardine population is low. At other times, northern gulf waters of South Australia may provide a refuge for the anchovy that the sardine cannot utilize. [source]

    Fine scale spatial pattern of Pacific sardine (Sardinops sagax) and northern anchovy (Engraulis mordax) eggs

    K. Alexandra Curtis
    Abstract Pacific sardine (Sardinops sagax) and northern anchovy (Engraulis mordax) eggs exhibited different spatial structure on the scale of 0.75,2.5 km in two egg patches sampled in the Southern California Bight in April 2000. Plankton samples were collected at 4-min intervals with a Continuous Underway Fish Egg Sampler (CUFES) on 5 × 5 km grids centered on surface drifters. Variograms were calculated for sardine and anchovy eggs in Lagrangian coordinates, using abundances of individual developmental stages grouped into daily cohorts. Model variograms for sardine eggs have a low nugget effect, about 10% of the total variance, indicating high autocorrelation between adjacent samples. In contrast, model variograms for anchovy eggs have a high nugget effect of 50,100%, indicating that most of the variance at the scales sampled is spatially unstructured. The difference between observed spatial patterns of sardine and anchovy eggs on this scale may reflect the behavior of the spawning adults: larger, faster, more abundant fish may organize into larger schools with greater structure and mobility that create smoother egg distributions. Size and mobility vary with population size in clupeoids. The current high abundance of sardines and low abundance of anchovy off California agree with the greater autocorrelation of sardine egg samples and the observed tendency for locations of anchovy spawning to be more persistent on the temporal scale of days to weeks. Thus the spatial pattern of eggs and the persistence of spawning areas are suggested to depend on species, population size and age structure, spawning intensity and characteristic physical scales of the spawning habitat. [source]

    Impact of freshwater input and wind on landings of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in shelf waters surrounding the Ebre (Ebro) River delta (north-western Mediterranean)

    J. Lloret
    Abstract Time series analyses (Box,Jenkins models) were used to study the influence of river runoff and wind mixing index on the productivity of the two most abundant species of small pelagic fish exploited in waters surrounding the Ebre (Ebro) River continental shelf (north-western Mediterranean): anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus). River flow and wind were selected because they are known to enhance fertilization and local planktonic production, thus being crucial for the survival of fish larvae. Time series of the two environmental variables and landings of the two species were analysed to extract the trend and seasonality. All series displayed important seasonal and interannual fluctuations. In the long term, landings of anchovy declined while those of sardine increased. At the seasonal scale, landings of anchovy peaked during spring/summer while those of sardine peaked during spring and autumn. Seasonality in landings of anchovy was stronger than in sardine. Concerning the environmental series, monthly average Ebre runoff showed a progressive decline from 1960 until the late 1980s, and the wind mixing index was highest during 1994,96. Within the annual cycle, the minimum river flow occurs from July to October and the wind mixing peaks in winter (December,April, excluding January). The results of the analyses showed a significant correlation between monthly landings of anchovy and freshwater input of the Ebre River during the spawning season of this species (April,August), with a time lag of 12 months. In contrast, monthly landings of sardine were significantly positively correlated with the wind mixing index during the spawning season of this species (November,March), with a lag of 18 months. The results provide evidence of the influence of riverine inputs and wind mixing on the productivity of small pelagic fish in the north-western Mediterranean. The time lags obtained in the relationships stress the importance of river runoff and wind mixing for the early stages of anchovy and sardine, respectively, and their impact on recruitment. [source]

    Modelling the effect of buoyancy on the transport of anchovy (Engraulis capensis) eggs from spawning to nursery grounds in the southern Benguela: an IBM approach

    C. Parada
    Abstract An individual-based model (IBM) was used to investigate the effects of physical and biological variables on the transport via a jet current of anchovy (Engraulis capensis) eggs from spawning to the nursery grounds in the southern Benguela ecosystem. As transport of eggs and early larvae is considered to be one of the major factors impacting on anchovy recruitment success, this approach may be useful to understand further the recruitment variability in this economically and ecologically important species. By coupling the IBM to a 3D hydrodynamic model of the region called Plume, and by varying parameters such as the spatial and temporal location of spawning, particle buoyancy, and the depth range over which particles were released, we could assess the influences of these parameters on transport success. A sensitivity analysis using a General Linear Model identified the primary determinants of transport success in the various experimental simulations, and model outputs were examined and compared with patterns observed in field studies. Model outputs compared well with observed patterns of vertical and horizontal egg distribution. Particle buoyancy and area of particle release were the major single determinants of transport success, with an egg density of 1.025 g cm,3 maximizing average particle transport success and the western Agulhas Bank being the most successful spawning area. This IBM may be useful as a generic prototype for other upwelling ecosystems. [source]

    The influence of mesoscale ocean processes on anchovy (Engraulis encrasicolus) recruitment in the Bay of Biscay estimated with a three-dimensional hydrodynamic mode

    G. Allain
    The relationship between anchovy (Engraulis encrasicolus) recruitment in the Bay of Biscay and environmental variables during their planktonic phase (March to July) was investigated from 1986 to 1997. Meteorological variables (wind and temperature) are forcing effects on the sea, but they are not thought to be processes that govern larval survival directly. Food-web dynamics are believed to be more closely linked to larval survival and are related to the physical vertical water column structure. Therefore, we used a three-dimensional (3D) hydrodynamic model to characterize three major physical mesoscale processes affecting vertical structure in south-east Biscay: stratification, upwelling and river plume extent. Indices were estimated from the model outputs to characterize and quantify the space/time evolution of these structures during the period March to July. A multiple linear regression analysis was then used to analyse hierarchy in the explanatory power of the physical indices. Coastal upwelling and shelf stratification breakdown indices were the most significant explanatory variables, with positive and negative effect on recruitment, respectively. A model with these two indices explains 75% of the recruitment variability of anchovy observed in the period 1987,96. [source]

    Environmental signature in the otolith elemental fingerprint of the tapertail anchovy, Coilia mystus, from the Changjiang estuary, China

    J. Yang
    Summary The ontogenetic patterns of habitat use and the migratory history of the tapertail anchovy, Coilia mystus, collected in the Changjiang estuary around Chongming Island, China, were studied by examining the environmental signature in the otolith strontium (Sr) and calcium (Ca) fingerprints using electron probe microanalysis (EPMA). Our results suggest that the migration strategy of C. mystus is much more flexible than supposed in the literature to date. The spring spawning population of C. mystus from the studied area was found to consist of individuals with different migration histories. Although the tapertail anchovy seems to be an anadromous fish that spawns and hatches in a freshwater habitat, it can also use a freshwater environment in non-spawning seasons. The otolith EPMA of the elemental fingerprint (Sr x-ray maps and Sr : Ca ratios) is an environmental indicator that can be applied to the migratory ecology of other important diadromous species in China. [source]

    Growth of larval Pacific anchovy Engraulis japonicus in the Yellow Sea as indicated by otolith microstructure analysis

    S.-D. Hwang
    Larval Pacific anchovy Engraulis japonicus were sampled from coastal waters off the central west coast of Korea from June to November 1996. Using otolith microstructure analysis (daily growth increments), three cohorts (spring, early summer and late summer) were distinguished based on backcalculated spawning dates. Growth rates differed between cohorts, with higher growth rates for late-summer cohorts than either the spring or early-summer cohorts. Growth rate was positively related to surface water temperature, with an optimum temperature range of between 20 and 26° C occurring during the late summer (late July through to mid-September). The study highlights that early growth rates of Pacific anchovy are dependent on ecosystem (particularly water temperature) attributes during early life. [source]

    Validation of daily increment formation in otoliths of juvenile and adult European anchovy

    P. Cermeño
    The otoliths of juveniles and adults of European anchovy Engraulis encrasicolus held in aquaria were marked by immersion in oxytetracycline hydrochloride (OTC) at concentrations between 350 and 410 mg l,1 for 12 h. Counts of microincrements between fluorescent bands validated the daily otolith increment formation. The otolith increments were easily readable at ×400 with average increment widths of c. 1·1 µm. Validation was successfully demonstrated in juveniles and adults maintained for short periods in the aquaria in the summer. For European anchovy captured as juvenile and reared to adults, however, increment formation appeared less than daily. The daily periodicity of the otoliths in juvenile European anchovy implies that counting of microincrements can be used to study their birth dates. The application of this technique to adults, however, may lead to the underestimation of actual age and further research needs to be done to clarify the reasons for the apparent loss of the daily rhythm over long periods. [source]

    Persistent Organic Pollutants in Fish Oil Supplements on the Canadian Market: Polychlorinated Biphenyls and Organochlorine Insecticides

    Dorothea F.K. Rawn
    ABSTRACT:, Fish and seal oil dietary supplements, marketed to be rich in omega-3 fatty acids, are frequently consumed by Canadians. Samples of these supplements (n,= 30) were collected in Vancouver, Canada, between 2005 and 2007. All oil supplements were analyzed for polychlorinated biphenyls (PCBs) and organochlorine insecticides (OCs) and each sample was found to contain detectable residues. The highest ,PCB and ,DDT (1,1,1-trichloro-di-(4-chlorophenyl)ethane) concentrations (10400 ng/g and 3310 ng/g, respectively) were found in a shark oil sample while lowest levels were found in supplements prepared using mixed fish oils (anchovy, mackerel, and sardine) (0.711 ng ,PCB/g and 0.189 ng ,DDT/g). Mean ,PCB concentrations in oil supplements were 34.5, 24.2, 25.1, 95.3, 12.0, 5260, 321, and 519 ng/g in unidentified fish, mixed fish containing no salmon, mixed fish with salmon, salmon, vegetable with mixed fish, shark, menhaden (n,= 1), and seal (n,= 1), respectively. Maximum concentrations of the other OCs were generally observed in the seal oil. The hexachlorinated PCB congeners were the dominant contributors to ,PCB levels, while ,DDT was the greatest contributor to organochlorine levels. Intake estimates were made using maximum dosages on manufacturers' labels and results varied widely due to the large difference in residue concentrations obtained. Average ,PCB and ,DDT intakes were calculated to be 736 ± 2840 ng/d and 304 ± 948 ng/d, respectively. [source]

    Validation of macroscopic maturity stages according to microscopic histological examination for European anchovy

    MARINE ECOLOGY, Issue 2009
    Rosalia Ferreri
    Abstract The identification and classification of macroscopic maturity stages plays a key role in the assessment of small pelagic fishery resources. The main scientific international commissions strongly recommend standardizing methodologies across countries and scientists. Unfortunately, there is still a great deal of uncertainty concerning macroscopic identification, which remains to be validated. The current paper analyses reproductive data of European anchovy (Engraulis encrasicolus L. 1758), collected during three summer surveys (2001, 2005 and 2006) in the Strait of Sicily, to evaluate the uncertainty in the macroscopic maturity stage identification and the reliability of the macroscopic adopted scale. On board the survey vessels, the maturity stage of each fish was determined macroscopically by means of an adopted maturity scale subdivided in six stages. Later, at the laboratory, the gonads were prepared for histological examination. The histological slides were analysed, finally assigning the six maturity stages for macroscopic examinations. A correspondence table was obtained with the proportion and number of matches between the two methods. The results highlight critical aspects in the ascription of macroscopic maturity stages, particularly for the present research aim. Different recommendations were evaluated depending on the scope of the study conducted on maturity (e.g. daily egg production, fecundity and maturity ogive computation). The most interesting results concern the misclassification of stage IV and stages III and V (the most abundant), which confirms their macroscopic similarity. Although the results are based on a small number of samples, the advantages and disadvantages of macroscopic and histological methods are discussed with the aim to increase the accuracy of correct identification and to standardize macroscopic maturity ascription criteria. [source]

    Occupational allergy and asthma among salt water fish processing workers

    Mohamed F. Jeebhay MBChB
    Abstract Background Fish processing is a common economic activity in Southern Africa. The aim of this study was to determine the prevalence and host determinants of allergic symptoms, allergic sensitization, bronchial hyper-responsiveness and asthma among workers processing saltwater fish. Methods A cross-sectional study was conducted on 594 currently employed workers in two processing plants involved in pilchard canning and fishmeal processing. A modified European Community Respiratory Health Survey (ECRHS) questionnaire was used. Skin prick tests (SPT) used extracts of common airborne allergens, fresh fish (pilchard, anchovy, maasbanker, mackerel, red eye) and fishmeal. Spirometry and methacholine challenge tests (MCTs; tidal breathing method) used ATS guidelines. Results Work-related ocular-nasal symptoms (26%) were more common than asthma symptoms (16%). The prevalence of atopy was 36%, while 7% were sensitized to fish species and 26% had NSBH (PC20,,,8 mg/ml or ,12% increase in FEV1 post-bronchodilator). The prevalence of probable occupational asthma was 1.8% and fish allergic rhino-conjunctivitis 2.6%. Women were more likely to report work-related asthma symptoms (OR,=,1.94) and have NSBH (OR,=,3.09), while men were more likely to be sensitized to fish (OR,=,2.06) and have airway obstruction (OR,=,4.17). Atopy (OR,=,3.16) and current smoking (OR,=,2.37), but not habitual seafood consumption were associated with sensitization to fish. Conclusions Based on comparison with previous published studies, the prevalence of occupational asthma to salt water fish is lower than due to shellfish. The gendered distribution of work and exposures in fish processing operations together with atopy and cigarette smoking are important determinants of occupational allergy and asthma. Am. J. Ind. Med. 51:899,910, 2008. © 2008 Wiley-Liss, Inc. [source]