Anchovy Engraulis Encrasicolus Research Articles

Diet of Cape fur seals Arctocephalus pusillus pusillus at three mainland breeding colonies in Namibia. 1. Spatial variation

The diet composition of Cape fur seals Arctocephalus pusillus pusillus was investigated from three breeding colonies in Namibia between January 1994 and April 2002 using scat analysis. Otolith numbers were corrected for those lost during digestion before determining the percentage numerical abundance of prey in each sample. Otolith diameters were corrected for erosion during digestion and then converted to fish length and mass to determine the percentage mass of prey in samples. In all, six main groups of teleost prey were identified, consisting of at least 48 species and 19 families. Cape Cross seals mainly consumed Cape horse mackerel Trachurus trachurus capensis, whereas lanternfish Lampanyctodes hectoris were negligible in their diet. At Van Reenen Bay and Atlas-Wolf Bay, the two southerly colonies, lanternfish were numerically prevalent in scats but not important in terms of mass. Cape hake Merluccius spp. and goby Sufflogobius bibarbatus featured in scats from all three colonies. The species in the pelagics prey group were of lesser dietary importance, with round herring Etrumeus whiteheadi being most prevalent in the south at Van Reenen Bay and anchovy Engraulis encrasicolus and sardine Sardinops sagax most prevalent in scats from Cape Cross. The difference in the prevalence of prey in seal diets seems to be related to fish distributions.

Tropical South-East Atlantic response to ENSO as an ecosystem indicator for the southern Benguela

The response of the tropical South-East Atlantic Ocean to the El Niño Southern Oscillation (ENSO) was studied for the period 1950–1999. Interaction between the ocean thermocline 'see-saw' and the overlying zonal wind circulation was examined. The two are closely linked through equatorial upwelling dynamics, with the thermocline leading during most of the period. Composite differences in climatic structure in respect of ENSO phase were analysed. Cases were selected based on indices of Pacific sea surface temperature and South-East African rainfall. Prior to an El Niño-induced drought, anomalous easterly flow over the Atlantic strengthens the cold tongue extending from Angola. How these climatic conditions affect fisheries abundance in the southern Benguela was investigated. Higher anchovy Engraulis encrasicolus catches tend to follow an El Niño event, and higher sardine Sardinops sagax catches tend to follow a La Niña event, through the northward and southward shift respectively of the South Atlantic anticyclone and attendant coastal upwelling. In the southern Benguela, enhanced westerlies and warmer water favour anchovy catches over sardine catches. Recognition of the climatic patterns that impact fisheries abundance represents a potential management tool.

Energy density of anchovy Engraulis encrasicolus L. in the Adriatic Sea

European anchovy Engraulis encrasicolus, with total lengths ranging from 40·0 to 132·5 mm, were sampled during October 2002 and May 2003 in the northern Adriatic Sea in order to estimate their energy densities (ED). A highly significant (P < 0·001) relationship between ED(y)(J g−1wet mass) and per cent dry mass (x) was found: y = 321x − 3316·9 (n = 161, r2 = 0·82).

Factors structuring reproductive habitat suitability of Engraulis encrasicolus in the south coast of Sicily

Egg and larval abundance, obtained from annual summer cruises carried out in the Strait of Sicily during 6 years (1997 to 2002), was used to identify the spawning and retention areas of the anchovy Engraulis encrasicolus. Larval amino acid composition was used to analyse the nutritional condition of the larvae collected during the 2002 survey. As the anchovy spawns along the south Sicilian coast, but mainly in the north‐west and middle parts of the coast, the higher number and larger size larvae in the south‐east end of the Sicilian coast indicated that larvae were transported by the main branch of the Atlantic‐Ionian Stream and retained in the south‐east end of the Sicilian coast (Cape Passero). This retention process, however, did not always favour the nutritional condition of the larvae, because the larvae were not transported to an area with a higher primary production or with a higher stability. In 2002 larval amino acid concentration was higher in the spawning areas than in those areas where the larvae were transported to, indicating a lower nutritional condition of the larvae in the nursery areas. The lack of enrichment and concentration processes, and low primary production in this area which limited body growth rate may explain the low locally reproducing anchovy population in the south coast of Sicily.

Influence of oceanographic fronts and low oxygen on the distribution of ichthyoplankton in the Benguela and southern Angola currents

The study focuses on ichthyoplankton populations in the southern Angola Current, the Angola-Benguela Front and the coastal upwelling area of the northern and central Benguela Current. The horizontal and vertical distributions of eggs and larvae of sardine Sardinops sagax, anchovy Engraulis encrasicolus and horse mackerel Trachurus trachurus capensis were examined in relation to distribution patterns of temperature, salinity and dissolved oxygen. Samples were collected during February–March 2002 using a Bongo net and a multiple opening/closing net in five depth layers (0–30m, 30–60m, 60–100m, 100–140m and 140–220m). Eggs and larvae were restricted mainly to the shelf areas in the Angola-Benguela Font and southern Angola Current waters. Their vertical distributions in the Angola-Benguela Front and northern Benguela upwelling region showed a sharp decline in abundance at about 60m depth. This decline appeared to be correlated to the distribution of dissolved oxygen in the water column It is hypothesised that low oxygen concentrations have a strong impact on the development and survival of the early life-cycle stages of fish, and that recruitment of sardine and other pelagic species relies more on the upward extension of the oxygen minimum layer than was previously thought.

Structural Stability of a Stage Structured Model of Fish: The Case of the Anchovy (Engraulis Encrasicolus L.) in the Bay of Biscay

A study of stage structured model of fish population is presented. This model focuse on the anchovy population in the Bay of Biscay (Engraulis encrasicolus L.) is presented. The method of study is based on an intermediate complexity mathematical model, taking into account the spatialisation, the environmental conditions and the stage-structure of the fishes. First, to test the model, we show mathematical properties, such as unicity of the solution of structural stability. Then we provide numerical simulations, to validate the model and to test the dynamics according to the variations of the parameters.

Investigations of the age and growth of Anchovy (Engraulis encrasicolus L., 1758) in Izmir Bay.

Investigations of the age and growth of Anchovy (Engraulis encrasicolus L., 1758) in Izmir Bay.

Stage-dependent vertical distribution of pelagic fish eggs on the western Agulhas Bank, South Africa

The vertical distributions of eggs of anchovy Engraulis encrasicolus, sardine Sardinops sagax and round herring Etrumeus whiteheadi over the western Agulhas Bank, South Africa, were sampled between 0m and 100m, using an opening-closing WP-2 net, to investigate differences in developmental stages of the eggs. Distributions varied ontogenetically, and vertical dispersion indices showed that early-stage eggs of all species were less aggregated than middle- and late-stages. Most of early-stage anchovy eggs were distributed in the upper 40m, whereas those of sardine and round herring were more widely distributed down to 60m and 80m respectively. Results suggest that anchovy spawn nearer to the surface than do sardine and round herring.

Impact of environmental factors on survival of larval and juvenile Cape anchovy Engraulis encrasicolus (G.) in the southern Benguela upwelling region, determined from hatchdate distributions: implications for recruitment

March larval and May juvenile Cape anchovy of the unusually strong 1999/2000 year-class were collected off South Africa. Age estimates were obtained from daily increment counts on otoliths using light microscopy for March larvae (14–70 mm standard length, SL, n = 193, 92% success rate), and scanning electron microscopy for May juveniles (52–110 mm SL, n = 80, 22% success rate). Differences between March and May hatchdate distributions were related to the prevailing temperatures. March larval hatchdate distributions showed slight modes in October/November 1999 and January/February 2000, each a month later than May juvenile hatchdate distributions (September/October and November/December). Thus, mortality rates of larvae hatched after mid-December seem to have been higher. Large areas of warm water (19–26°C sea surface temperature) on the Agulhas Bank, mid-November 1999 to March 2000, indicated conditions conducive to spawning and reduced offshore advection of spawning products. A period of strong upwelling, March to May 2000, is likely to have increased availability of planktonic food for older larvae; also causing offshore dispersal of younger larvae and food patches required by these, possibly leading to starvation mortality of younger larvae during strong upwelling. The critical period thus seemed to be later than at first-feeding.

Nuclear-DNA markers confirm the presence of two anchovy species in the Mediterranean

Morphometric, allozymic, and mitochondrial DNA variability previously indicated that the Mediterranean anchovy Engraulis encrasicolus includes two distinct forms, one of the inshore habitat, and the other one of the open-sea habitat. Here, we showed that the two forms significantly differ by several morphological characters. To test the hypothesis, proposed previously, that the two forms are distinct biological species, we used length-polymorphic, exon-primed intronic PCR markers from the creatine-kinase multigenic family and genetically characterized anchovy samples collected in the northwestern Mediterranean and in the eastern Atlantic. Large genetic differences were found between the two forms (Weir and Cockerham's θ ˆ = 0.397 to 0.586). In contrast, geographic variation in the open-sea form at the scale of the eastern Atlantic/northwestern Mediterranean was weak ( θ ˆ = − 0.006 to 0.042). This again demonstrated considerable restriction to nuclear gene flow between inshore and open-sea anchovy populations. In addition to previous results from allozymes, this confirmed their status as distinct biological species, namely Engraulis albidus sp. nov. and Engraulis encrasicolus L. To cite this article: P. Borsa et al., C. R. Biologies 327 (2004).

Distribution patterns of key fish species of the southern Benguela ecosystem: an approach combining fishery-dependent and fishery-independent data

Within the context of an ecosystem approach for fisheries, there is a need for quantitative information on distributions of key marine species. This information is valuable input for modelling species interactions in the southern Benguela ecosystem. In the present study, a method is described for mapping the density distribution of 15 key species: anchovy Engraulis encrasicolus, sardine Sardinops sagax, round herring Etrumeus whiteheadi, chub mackerel Scomber japonicus, horse mackerel Trachurus trachurus capensis, lanternfish Lampanyctodes hectoris, lightfish Maurolicus muelleri, albacore Thunnus alalunga, bigeye tuna Thunnus obesus, yellowfin tuna Thunnus albacares, silver kob Argyrosomus inodorus, snoek Thyrsites atun, Cape hake Merluccius spp., kingklip Genypterus capensis and chokka squid Loligo vulgaris reynaudi. The purpose was to make use of all available sources of data to extend the spatial and temporal coverage of the southern Benguela. Six sources of data were combined on a 10′ × 10′ cell grid in a Geographical Information System: acoustic and demersal surveys conducted by Marine and Coastal Management (MCM), and pelagic, demersal (including midwater trawl), hake-directed and tuna-directed longline commercial landings data collected by MCM. Comparisons of distributions between two periods (1980s and 1990s) and between two semesters (April – September and October – March) were conducted, but biases as a result of major differences in sampling strategy prevented detailed analysis for certain species. Maps of density distributions are nevertheless presented here and the method to determine them is discussed.

Influence of sample size and sampling frequency on the quantitative dietary descriptions of a predatory fish in the Benguela ecosystem

Spatial and temporal variation in the diet and feeding intensity of snoek, Thyrsites atun, a top predator of the southern Benguela, was investigated to provide information on data requirements for accuracy of annual diets as inputs to ecosystem models. Appropriate sample sizes to produce accurate daily or event-scale diet descriptions were investigated by means of a posteori tests. Cumulative prey diversity curves showed that 55 (± 25) stomachs containing food are required to accurately quantify presence and absence data of prey species. Differences in the percentage contribution of dominant prey in consecutive and cumulative 10-stomach classes, indicates that a minimum of 75–80 (± 25) stomachs containing food are necessary to describe the proportion by weight of primary prey. Diets of snoek (proportions by weight) sampled inshore (shallower than 50 m and within 25 km of the coast) off the Cape Peninsula during six consecutive weeks (i.e.one day per week) in autumn 2001 were highly variable. Comparing diet for the six-week period with that of diets from consecutive 10-sample weekly units revealed 95% similarity at 70 samples per week. Seasonal diets between Cape Columbine and Cape Hangklip also varied, but there was no evidence of a predictable seasonal pattern in diet that could be related to prey life history; two-way nested ANOSIM revealed that seasonal prey proportions across years were statistically less similar than those within years. Snoek spawn offshore in winter/spring. Statistical differences between inshore (< 50m) and offshore (>150m) prey composition were largely influenced by the absence of anchovy Engraulis encrasicolus and much larger proportions of Cape hake Merluccius spp. and lanternfish Lampanyctodes hectoris in the offshore diet. Feeding intensity (in terms of proportions of fish with prey and mean stomach fullness) was strongly seasonal and highest during the spawning season. Sampling programmes for the southern Benguela should account for spatial and temporal variation in diet and feeding intensity of predators if accurate annual dietary descriptions are to be achieved. The results of this study indicate that a minimum of 70 snoek stomachs (containing food) should be collected at each sampling event.

Contributions of the Benguela ecology programme to pelagic fisheries management in South Africa

In 1982, the Benguela Ecology Programme (BEP) created a formal, multi-institutional research partnership in South Africa. During the next two decades, the BEP directed many aspects of pelagic ecosystem research in the southern Benguela upwelling region, aiming to improve fisheries management, particularly that of anchovy Engraulis encrasicolus. Although much reduced in scale, the BEP is now in its fifth phase. Its early critics believed that much of the money invested in its ecosystem-type research had not benefited fisheries management, whereas its supporters maintain that many aspects of current pelagic fisheries management are founded on the BEP legacy. Ecosystem research underpinned the design of hydroacoustic surveys, and resulted in the development of expert system models aimed at predicting recruitment strength of anchovy. Current efforts to develop an ecosystem approach to management of the pelagic fishery in South Africa draw on the knowledge and understanding generated by more than 20 years of ecosystem research. However, despite this strong foundation, there is still uncertainty about the causes of interannual variability in pelagic fish recruitment. It is suggested that this time span is too short, and ecosystem monitoring and research should persist for decades to reap their full rewards. The BEP enabled productive partnerships to be established between academic and State researchers and fisheries managers, and improved linkages and communication to the fishing industry.

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

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.

Modelling the transport success of anchovy Engraulis encrasicolus eggs and larvae in the southern Benguela: the effect of spatio-temporal spawning patterns

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 250:247-262 (2003) - doi:10.3354/meps250247 Modelling the transport success of anchovy Engraulis encrasicolus eggs and larvae in the southern Benguela: the effect of spatio-temporal spawning patterns Jenny Huggett1,*, Pierre Fréon1,2, Christian Mullon2,3, Pierrick Penven2 1Marine and Coastal Management, Private Bag X2, Roggebaai 8012, South Africa 2Institut de Recherche pour le Développement, 213, rue La Fayette, 75480 Paris, France 3Department of Oceanography, University of Cape Town, Private Bag, Rondebosch 7701, Cape Town, South Africa *Email: jhuggett@mcm.wcape.gov.za ABSTRACT: Recruitment success of anchovy Engraulis encrasicolus in the southern Benguela is thought to depend largely on the passive transport of eggs and larvae from their warm-water spawning area, located in the southern part of their distribution range (Agulhas Bank), to their cold-water nursery grounds located 500 km away on the west coast of South Africa. In order to test this hypothesis, the output of a 3D hydrodynamic model was coupled to a particle-tracking model, allowing the quantification of different factors such as the timing and precise location of spawning activity, the frequency of spawning activity within a month, the level of aggregation of the spawning stock, and the interannual variability of transport due to mesoscale processes. Results from the model indicate that spawning season and area have a major effect on transport success. The most favourable period for spawning was September to March, peaking in November, and the western Agulhas Bank was the most favourable spawning area. A low success rate of passive transport to the core inshore nursery area in the model suggests that additional processes such as swimming or advection are required for larvae to reach this area. In general, there was good agreement between observed spawning patterns and the optimal temporal and spatial strata where particle transport was most successful, suggesting that the spawning strategy of anchovy is mainly the result of an adaptation to the circulation patterns in the region. Nonetheless, some discrepancies were observed between the success of transport and actual spawning patterns, and temperature may also be an important factor to take into consideration to fully explain how this originally temperate species is able to survive in an area of highly contrasting temperatures. KEY WORDS: Individual-based model · Transport success · Anchovy · Ichthyoplankton · Recruitment · Reproductive strategy · Southern Benguela · Engraulis encrasicolus Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 250. Online publication date: March 26, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Wind mixing, food availability and mortality of anchovy larvae Engraulis encrasicolus in the northern Adriatic Sea

A study was carried out in June/July 1996 in the River Po outflow in the northern Adriatic to investigate spawning of anchovy Engraulis encrasicolus and survival of larvae in relation to food availability and wind mixing. Hydrographic- and bongo net sampling was carried out on 2 grid sur- veys; one after a period of low winds and settled weather, and the other after an intervening period of strong winds, which resulted in a decrease in water column stratification. The spawning areas of an- chovy and the larval distributions were associated with the river outflow plume (most clearly on the second survey grid, after the period of higher winds). Potential food particles for anchovy larvae, pri- marily copepod nauplii and copepodite stages, were also concentrated in the area influenced by the river outflow. Although there was a nearly 50% reduction in the mean water column abundance of potential food particles between the 2 survey grids, mostly due to a decline in abundance outside the immediate river plume area, there was no significant change in mortality of anchovy larvae between the 2 grids; the exponential decline in numbers of eggs and larvae to 10 mm in length being equivalent to overall mortality rates of 43.2% d -1 on the first survey and 44.7% d -1 on the second. The resilience of larval survival under potentially less favourable feeding conditions, following the period of wind mixing, was ascribed, in part, to the maintenance of local water column stratification by the superficial low salinity input from the River Po. This stratification in the immediate outflow area was associated with the presence of concentrated layers of potential food particles (typically >50 particles l -1 and 1.5 to 2.8 times the mean water column abundance) in the upper 10 m of the water column, coincident with peak numbers of anchovy larvae. However, since there was no evidence for lower larval survival in areas, less influenced by the immediate river outflow plume, a simple direct relationship between enhanced water column stability, improved feeding conditions and larval survival was not supported.

Allozyme, mitochondrial-DNA, and morphometric variability indicate cryptic species of anchovy (Engraulis encrasicolus)

Previous surveys of population structure in the Atlantic-Mediterranean anchovy Engraulis encrasicolus L. have reported heterogeneity in morphology, allozyme frequencies, and mitochondrial DNA haplotype frequencies at a regional scale. In particular, two stocks of anchovy have been detected in the Adriatic Sea. In this paper, the available data is reviewed with the aim to relate genetic variation to geography at the widest possible geographical scale, for investigating the evolutionary mechanisms underlying stock structure in anchovy. Correspondence analysis of allozyme frequencies (24 samples, three polymorphic loci) compiled from the literature indicates three distinct entities in the Mediterranean Sea. Open-sea or oceanic anchovy populations are genetically different from inshore-water populations within a region (Nei's ^GST = 0.035–0.067), while broadscale geographical variation is weak for each of these two habitat-specific forms (^GST = 0.005–0.006). Mitochondrial-DNA haplotype frequencies support the distinction between an inshore form and an oceanic form (^GST = 0.067–0.107), with virtually no genetic differences among oceanic populations across the Gulf of Biscay, the western Mediterranean and the Ionian Sea (^GST = −0.001). If natural selection on marker loci is unimportant, these results indicate the occurrence of two parapatric, genetically distinct, habitat-specific forms that are widely distributed throughout the Mediterranean Sea. Persistent allele and haplotype-frequency differences between these forms indicate reproductive isolation and the presence of an E. encrasicolus species complex in the Mediterranean.

Estimation of the number density of fish from resonance absorptivity and echo sounder data

Diachok, O., Liorzou, B., and Scalabrin, C. 2001. Estimation of the number density of fish from resonance absorptivity and echo sounder data. – ICES Journal of Marine Science, 58: 137–153. This paper provides a comparison of number densities (number per m 2 in the horizontal plane) of pelagic fish, which were derived from acoustic absorptivity measurements and nearly coincident echo sounder and trawling data. Absorptivity measurements were made with a broadband source (between frequencies of 0.6 and 5.0 kHz) as a function of time between a fixed source and a fixed receiver separated by 12 km in relatively shallow (83 m) water. The sardine (Sardina pilchardus Walbaum) was the dominant species at this measurement site. The second most common species was the anchovy (Engraulis encrasicolus Linnaeus); there were approximately twice as many sardines as anchovies. The number densities of all other species were small. Strong absorption lines were evident at the resonance frequencies of dispersed sardines. The frequencies of these absorption lines changed in accordance with the vertical migration of sardines at twilight. A correction for the influence of anchovies on the absorption line, which was dominated by dispersed sardines at night, was applied to the absorption-based estimate. Initial echo sounder based estimates of number densities, which were based on a ‘‘universal’’ pressure independent equation of target strength, were corrected for pressure dependence, attenuation by near surface bubbles, and avoidance. The corrected absorption based number density of sardines (1.4 m 2 ) was in excellent agreement with the average corrected echo sounder based estimate (1.0 m 2 ). These results suggest the possibility of

A review of zooplankton investigations of the Black Sea over the last decade

Investigations performed in the last decade indicate that there have been important changes in the zooplankton composition and structure in the Black Sea. However, contrasting events taking place in different regions of the Black Sea indicate a non-uniform structure of its ecosystem. Several fodder zooplankton species have either disappeared from or substantially decreased in number at different sampling sites of the Black Sea over the last one or two decades. Some other species adapted to thrive in eutrophic conditions have either appeared or increased in quantity. Meanwhile the biomass of the fodder zooplankton has also fluctuated considerably through the years. However, there seems to be a reverse trend in the long-term variation of fodder zooplankton between the shallow western and deep eastern areas. Over the last few decades the abundance of fish larvae has decreased significantly when compared either to past records or with larval abundances of other seas. This was shown to be due mainly to malnutrition of larvae. One of the most striking changes in the ichthyoplankton has been the shift in the spawning areas of the main fish species, the anchovy Engraulis encrasicolus from the northwestern to the southeastern Black Sea. Even the invading ctenophore Mnemiopsis were found to be starving. The condition of other species ( Calanus euxinus and Pleurobrachia pileus) disclosed the fact that cyclonic regions where chlorophyll and nutrient concentrations are high, provide better nutrition than anticyclonic regions.

Relating fish recruitment to stock biomass and physical environment in the Black Sea using generalized additive models

Relationships between recruitment, parental stock biomass and physical environment variables in four Black Sea species: sprat Sprattus sprattus, whiting Merlangius merlangus, anchovy Engraulis encrasicolus and horse mackerel Trachurus mediterraneus, were investigated using generalized additive models (GAMs). Sea surface temperature, wind speed, wind stress, wind mixing, sea level atmospheric pressure and river run-off data were used as indices of interannual variability of the Black Sea environment. The environmental variables were studied by means of the principal component analysis, which tended to account for the major patterns in the time series and approximate the main environmental forcing agents in the sea. Recruitment responses to the considered environmental predictors in the four cases were compared and possible interpretations were discussed. Significant correlations appear between fish recruitment, stock biomass and physical environment. Patterns of the recruitment response to wind variables and sea level atmospheric pressure were found similar in the four species. The relationships indicated similarities between anchovy and whiting, whose reproduction is related to the coastal habitat on the one hand, and between sprat and horse mackerel, which are open sea spawners on the other hand. Recruitment in the latter species appeared to be less dependant on the parental stock biomass and the river discharge and was negatively related with SST. GAM was found to be a suitable tool for fisheries and environmental data analysis, providing a flexible and powerful way to explore and model non-linear relationships.