Anchovy Biomass Research Articles

Recent collapse of northern anchovy biomass off California

New estimates of abundance of northern anchovy (Engraulis mordax) are developed from California Cooperative Oceanic Fisheries Investigations (CalCOFI) data on egg and larval densities for the period 1951–2011. Previous estimates utilizing mean density over the CalCOFI area show a hyperstability bias because of the nearshore concentration of CalCOFI stations and the tendency of the anchovy population to contract into this area when abundances are low. New abundance estimates weight sample egg and larval densities to the local area represented by that sample, and then sum contributions to obtain total abundance. We develop total egg and larval abundance estimates for January and April, form a combined index, and calibrate it to the absolute biomass estimates produced by the Daily Egg Production Method in the early 1980s. Anchovy spawning biomass was very low, 10,000–20,000 Metric Tons (MT), in the early 1950s when CalCOFI sampling began. Abundance increased and fluctuated between 0.5 and 2 million metric tons from 1960 through 1990. After 1990, spawning biomass fluctuated around 200,000 tons, briefly increased during 2005–2006, then declined substantially over four years to below 20,000 tons from 2009 to 2011. CalCOFI ichthyoplankton data collected after 2011 are not yet available for analysis, but continuous underway egg sampling conducted during CalCOFI cruises indicates continued low abundance and very limited spawning through 2015 in both southern and central California. The recent collapse of anchovy abundance occurred in the absence of a significant fishery. Present annual catches of a few thousand tons are small by historical comparison, but the exploitation rate may now be relatively high given the low stock abundance. The decline in anchovy abundance coincides with recent die-offs and reproductive failures of anchovy-dependent predators in the ecosystem (e.g., sea lions and pelicans).

Trends in productivity and biomass yields in the Mediterranean Sea Large Marine Ecosystem during climate change

In this essay we briefly describe climate change in the Mediterranean Sea Large Marine Ecosystem (LME) using different indices. We further describe the evolution of yearly catches and species composition of the catches in the West (W), Central (C), and East (E) Mediterranean LME during 1970–2010 and the exploitation status of the fisheries resources and review various signals of climate on Mediterranean fisheries. In addition, we explore the mean temperature of the catch in the W, C and E Mediterranean under a scenario considering the catches of species migrating through the Suez Canal. We further review the existing habitat modeling studies at the Mediterranean scale of various species and discuss their response to climate change. Finally, we present the development of a 3-D full life cycle population model and the respective model forecasts of European anchovy (Engraulis encrasicolus) biomass at the Mediterranean Sea LME scale.

Lipstick method is better than conventional ‘Ink Method’ for taking dermatoglyphic prints

In this essay we briefly describe climate change in the Mediterranean Sea Large Marine Ecosystem (LME) using different indices. We further describe the evolution of yearly catches and species composition of the catches in the West (W), Central (C), and East (E) Mediterranean LME during 1970–2010 and the exploitation status of the fisheries resources and review various signals of climate on Mediterranean fisheries. In addition, we explore the mean temperature of the catch in the W, C and E Mediterranean under a scenario considering the catches of species migrating through the Suez Canal. We further review the existing habitat modeling studies at the Mediterranean scale of various species and discuss their response to climate change. Finally, we present the development of a 3-D full life cycle population model and the respective model forecasts of European anchovy (Engraulis encrasicolus) biomass at the Mediterranean Sea LME scale.

Interannual Changes in Biomass Affect the Spatial Aggregations of Anchovy and Sardine as Evidenced by Geostatistical and Spatial Indicators.

Geostatistical techniques were applied and a series of spatial indicators were calculated (occupation, aggregation, location, dispersion, spatial autocorrelation and overlap) to characterize the spatial distributions of European anchovy and sardine during summer. Two ecosystems were compared for this purpose, both located in the Mediterranean Sea: the Strait of Sicily (upwelling area) and the North Aegean Sea (continental shelf area, influenced by freshwater). Although the biomass of anchovy and sardine presented high interannual variability in both areas, the location of the centres of gravity and the main spatial patches of their populations were very similar between years. The size of the patches representing the dominant part of the abundance (80%) was mostly ecosystem- and species-specific. Occupation (area of presence) appears to be shaped by the extent of suitable habitats in each ecosystem whereas aggregation patterns (how the populations are distributed within the area of presence) were species-specific and related to levels of population biomass. In the upwelling area, both species showed consistently higher occupation values compared to the continental shelf area. Certain characteristics of the spatial distribution of sardine (e.g. spreading area, overlapping with anchovy) differed substantially between the two ecosystems. Principal component analysis of geostatistical and spatial indicators revealed that biomass was significantly related to a suite of, rather than single, spatial indicators. At the spatial scale of our study, strong correlations emerged between biomass and the first principal component axis with highly positive loadings for occupation, aggregation and patchiness, independently of species and ecosystem. Overlapping between anchovy and sardine increased with the increase of sardine biomass but decreased with the increase of anchovy. This contrasting pattern was attributed to the location of the respective major patches combined with the specific occupation patterns of the two species. The potential use of spatial indices as auxiliary stock monitoring indicators is discussed.

A 500 year climate catch: Pelagic fish scales and paleoproductivity in the Santa Barbara Basin from the Medieval Climate Anomaly to the Little Ice Age (AD 1000–1500)

Based upon observations from the 20th century, populations of lower trophic level, short-lived fish species are thought to be controlled by large scale ocean–atmosphere circulation shifts. Here, we provide a new 500 year reconstruction of northern anchovy and Pacific sardine fish scale deposition rates (SDRs) and relative abundance from Santa Barbara Basin (SBB), through the transition from the Medieval Climate Anomaly into the Little Ice Age (AD 1000–1500). Three intervals of high anchovy biomass (high SDRs) were coincident with increased upwelling diatom abundance in SBB and cool/negative Pacific Decadal Oscillation (PDO) events at 1130–1160, 1280–1310 and 1410–1450. Intervals of absent or low SDR of both sardine and anchovy in SBB sediments occurred in association with increased wave activity (benthic diatoms), California Current diatoms, and the relative dominance of sardine over anchovy. Thus although ocean–atmosphere circulation shifts such as the PDO appear to play a role in shifting the dominance of anchovy over sardine, the biomass of sardines as indicated by SDRs has a more complicated response to environmental change.

Relationships between environmental features, distribution and abundance of the Argentine anchovy, Engraulis anchoita, on the South West Atlantic Continental Shelf

Marine fisheries in Brazil follow a similar trend as the rest of the world, with reduced catches of most stocks. Although extensive, the Brazilian coast is poorly assessed, and marine fishery resources are not properly managed. Small pelagic fishes are secondary consumers, which feed on zooplankton and serve as foraging species for large, carnivorous fishes. The anchovy (Engraulis anchoita) is an abundant, small pelagic fish found in abundance in Brazilian waters as it migrates along the Brazilian, Uruguayan and Argentine shelves. In 2010, five acoustic assessment cruises were conducted to estimate anchovy biomass in the southernmost part of the Brazilian coast. Hydroacoustic data were obtained using a SIMRAD EK 500 echo sounder along parallel transects. CTD (conductivity temperature depth) casts and mid-water trawl hauls were used to collect environmental and biological data. Anchovy biomass was estimated using NASC values, the fish target strength by size and the dimension of the surveyed area. For each survey, a GLM binomial was fitted to anchovy presence and the following explanatory variables: surface salinity and temperature, bottom salinity and temperature, and depth. Anchovy biomass ranged between 73,000 (June) and 814,000 (August) tons. We observed a mean temperature decrease of ∼3°C during the June and August surveys. This sharp environmental change was followed by a distinct increase in adult anchovy biomass from the first to the second survey. Fitted GLM models indicated that the bottom layers of cold, saline water had a positive effect on anchovy presence in August but not in June. Furthermore, during the August survey, a sharp change in the surface layer waters was observed on the Southern Brazilian Shelf, as the result of a low-salinity water inflow to this area. This phenomena was due to the Patos Lagoon runoff and also to the coastal winds over the Argentine Shelf, which forces the northward spreading of the Plate River plume to lower latitudes. This inflow increases primary productivity and, subsequently, the occurrence of fishes within the area.

2013년-2014년 춘계와 동계에 대한 통영과 여수 연안역의 멸치 어군의 현존량 추정

Anchovy (Engraulis japonicus) is one of the most important species in the South Sea of South Korea. In order to estimate the biomass of anchovy, acoustic surveys, concurrently with trawling, were conducted in April, July, and September of 2013 and February of 2014 off the coast of Tongyeong and Yeosu. However, anchovies were found only during spring (April) and winter (February) surveys. To display only anchovy species confirmed by trawls on empty spaced echograms, virtual echograms were created. Three target strength (TS) values of anchovy were used: TS_z

Distribution and abundance of eggs and estimation of spawning stock biomass of anchovy,Engraulis encrasicolus(Linnaeus, 1758), in the south-eastern Adriatic Sea

Seasonal distribution and abundance of anchovy eggs were analysed during three scientific cruises carried out from summer 2006 to summer 2007 in the Boka Kotorska Bay, and one cruise in July 2008 in the open waters of the south-eastern Adriatic Sea. Daily egg production method (DEPM) was applied for the first time for estimation of the anchovy spawning stock biomass in the south-eastern Adriatic Sea. The daily egg production was 13–581 eggs day−1within the bay, and 42–110 eggs day−1in the open waters. Anchovy egg abundance was highest in spring inside the Bay of Kotor (one of the innermost and eutrophic sub-bays of the Boka Kotorska Bay), which indicates that the conditions for anchovy spawning are very favourable in this part of the Adriatic Sea, even when temperatures are below the optimum. This study has shown that the Boka Kotorska Bay is an area of very intensive spawning of anchovy, and that small-size anchovies live and spawn in the bay, and after spawning migrate towards open waters. The length at which 50% of anchovy were mature (L50) was calculated as 9.28 for females and 9.02 for males. Spawning stock biomass was at a stable level during the period of investigation.

수산음향기법을 이용한 아산만 멸치(Engraulis japonicus)와 기타어군의 분포 및 현존량 추정

The distribution and abundance of coastal fish species in Asan Bay, Korea, were estimated from hydroacoustic survey and net catches. Acoustic data were collected with 38 and 200 kHz from July to October of 2012, and converted to the nautical area scattering coefficient (NASC, <TEX>$m^2/mile^2$</TEX>) for <TEX>$0.25n{\cdot}mile$</TEX> along ten transects. Japanese anchovy Engraulis japonicus was the dominant specie in the net catches. The virtual echogram technique was used to distinguish E. japonicus from other species based on the differences in the mean volume backscattering strength (<TEX>${\Delta}MVBS$</TEX>) at 38 and 200 kHz. Engraulis japonicus and other fishes are mainly distributed in the center channel and outer part of Asan Bay. E. japonicus tends to move from inner to outer Asan Bay in summer and fall. From NASC data, the target strength and length-weight function of E. japonicus and other fishes were used to estimate the E. japonicus stock at 24.1-93.3 tons, and other fish at 40.6-88.4 tons from July to October 2012. The estimated anchovy biomass compared well with the cumulative catch weight from stow net catches. The hydroacoustic method offers an approach to understanding spatial/temporal structure and estimating the biomass of fish aggregations in coastal areas.

A Bayesian approach to estimate the biomass of anchovies off the coast of Perú.

The Northern Humboldt Current System (NHCS) is the world's most productive ecosystem in terms of fish. In particular, the Peruvian anchovy (Engraulis ringens) is the major prey of the main top predators, like seabirds, fish, humans, and other mammals. In this context, it is important to understand the dynamics of the anchovy distribution to preserve it as well as to exploit its economic capacities. Using the data collected by the "Instituto del Mar del Perú" (IMARPE) during a scientific survey in 2005, we present a statistical analysis that has as main goals: (i) to adapt to the characteristics of the sampled data, such as spatial dependence, high proportions of zeros and big size of samples; (ii) to provide important insights on the dynamics of the anchovy population; and (iii) to propose a model for estimation and prediction of anchovy biomass in the NHCS offshore from Perú. These data were analyzed in a Bayesian framework using the integrated nested Laplace approximation (INLA) method. Further, to select the best model and to study the predictive power of each model, we performed model comparisons and predictive checks, respectively. Finally, we carried out a Bayesian spatial influence diagnostic for the preferred model.

Ecosystem scenarios shape fishermen spatial behavior. The case of the Peruvian anchovy fishery in the Northern Humboldt Current System

A major goal in marine ecology is the understanding of the interactions between the dynamics of the different ecosystem components, from physics to top predators. While fishermen are among the main top predators at sea, almost none of the existing studies on ecology from physics to top predators contemplate fishermen as part of the system. The present work focuses on the coastal processes in the Northern Humboldt Current System, which encompasses both an intense climatic variability and the largest monospecific fishery of the world. From concomitant satellite, acoustic survey and Vessel Monitoring System data (∼90,000 fishing trips) for a ten-year period (2000–2009), we quantify the associations between the dynamics of the spatial behavior of fishermen, environmental conditions and anchovy (Engraulis ringens) biomass and spatial distribution. Using multivariate statistical analyses we show that environmental and anchovy conditions do significantly shape fishermen spatial behavior and present evidences that environmental fluctuations smoothed out along trophic levels. We propose a retrospective analysis of the study period in the light of the ecosystem scenarios evidenced and we finally discuss the potential use of fishermen spatial behavior as ecosystem indicator.

Rapid changes in growth, condition, size and age of small pelagic fish in the Mediterranean

Since 2007, the ecosystem of the Gulf of Lions has shifted to a different regime, characterised by a low anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) biomass and a remarkably high sprat (Sprattus sprattus) biomass. Surprisingly, the abundance and recruitment of anchovy and sardine remained high. To understand which processes (bottom-up or top-down control, etc.) could have caused this shift, we studied the changes in body condition, growth and size and age of anchovy, sardine and sprat over 1984–1985 and 1992–2012, using data from scientific surveys. The annual age structure of anchovy and sardine was estimated using Bayesian mixture models based on size frequency data with priors on the age–length relationship derived from independent otolith readings. The results indicated periods during which anchovy and sardine were in an average (1992–2004), good (2005–2007) or poor (2008–2012) overall state of condition. For sardine, the shift towards smaller fish observed during these past 4 years was explained by a combination of slower growth and the disappearance of older individuals (ages 2+). Despite the increase in biomass of sprat since 2008, indications were found that sprat was also smaller than in the past. As growth and condition decreased and overexploitation has not been documented or suspected for those three species in this area, we propose that the current decline in sardine and anchovy biomass could be due to qualitative and/or quantitative modifications in the planktonic production (i.e. a bottom-up control) or mass mortalities of adults due to an epidemic disease.

Comparison of anchovy biomass estimates measured by trawls, egg production methods and hydro-acoustics in the Chesapeake Bay and the Korea Strait

We compared estimates of anchovy biomass derived from trawl surveys, egg production method (EPM) and acoustic surveys, conducted in two remote regions. Biomass density of bay anchovy Anchoa mitchilli was estimated in Chesapeake Bay, USA, by trawls, EPM and acoustics from 1989 to 2000. Biomass density of Pacific anchovy Engraulis japonicus was estimated in the Korea Strait using EPM, simulation-based daily cohort analysis and acoustics from 1984 to 2006. Most of the existing estimates already had considered body-size-dependent gear selectivity, highlyvariable instantaneous natural mortality of anchovy eggs, and avoidance of trawl nets by adult anchovy. Despite great variability in the ratio of trawl to acoustic biomass estimates (0.034–8.35), annually-averaged biomass density of young-ofthe-year individuals derived by the two methods were similar for bay anchovy in Chesapeake Bay and Pacific anchovy in the Korea Strait (0.83 and 0.70 g m−3, respectively). Results suggested that, despite substantial uncertainty, anchovy biomass estimates are generally compatible between EPM and acoustics. However, reported estimates of biomass density derived from the two acoustic surveys in the Korea Strait differed by a factor of 28, suggesting that further improvements in calibrations are required to reliably estimate anchovy biomass. The comparisons suggested that all biomass estimates could be biased and will require comparison and validation by other, independent sampling methods.

Comprehensive Model of Jumbo Squid Dosidicus gigas Trophic Ecology in the Northern Humboldt Current System

The jumbo squid Dosidicus gigas plays an important role in marine food webs both as predator and prey. We investigated the ontogenetic and spatiotemporal variability of the diet composition of jumbo squid in the northern Humboldt Current system. For that purpose we applied several statistical methods to an extensive dataset of 3,618 jumbo squid non empty stomachs collected off Peru from 2004 to 2011. A total of 55 prey taxa was identified that we aggregated into eleven groups. Our results evidenced a large variability in prey composition as already observed in other systems. However, our data do not support the hypothesis that jumbo squids select the most abundant or energetic taxon in a prey assemblage, neglecting the other available prey. Indeed, multinomial model predictions showed that stomach fullness increased with the number of prey taxa, while most stomachs with low contents contained one or two prey taxa only. Our results therefore question the common hypothesis that predators seek locally dense aggregations of monospecific prey. In addition D. gigas consumes very few anchovy Engraulis ringens in Peru, whereas a tremendous biomass of anchovy is potentially available. It seems that D. gigas cannot reach the oxygen unsaturated waters very close to the coast, where the bulk of anchovy occurs. Indeed, even if jumbo squid can forage in hypoxic deep waters during the day, surface normoxic waters are then required to recover its maintenance respiration (or energy?). Oxygen concentration could thus limit the co-occurrence of both species and then preclude predator-prey interactions. Finally we propose a conceptual model illustrating the opportunistic foraging behaviour of jumbo squid impacted by ontogenetic migration and potentially constrained by oxygen saturation in surface waters.

Role of the Nutritional Condition of Breeding Anchovies in the Subsequent Recruitment to their Population in the Bay of Biscay (NE Atlantic)

The recruitment of marine fish populations is a central concern of fisheries scientists. Multiple research pathways have been explored, with emphasis of the causes of mortality affecting principally the early developmental stages of fish life. The small data set presented focuses on a feature often inadequately considered, i.e., the nutritional condition of the breeding parent fishes estimated from the levels of the RNA/DNA ratio determined in fish white muscle. This is applied to the European anchovy population inhabiting the French continental shelf of the North-east Atlantic Ocean. In four of the five years analysed, the annual recruitment shows a tight relationship with the mean values for the RNA/DNA ratio determined in the parent fish during the previous breeding season. One year is clearly distinguished from this model, owing to a strong drop of the recruitment, of which an explanation is tentatively advanced. This drop coincides with the beginning of a strong collapse of the population. A very low level of the anchovy biomass will last ten years. The role of the nutrition of breeding fish in the recruitment success is discussed in connection with the literature that emphasized the importance of conditions providing fish with sufficient fuel during the crucial period of its gametogenesis, particularly in clupeoids and anchovies.

The application of an age-structured model to the north Aegean anchovy fishery: An evaluation of different management measures

The objective of this paper is the integration of existing biological and fishery knowledge of anchovy into a unified modelling framework in order to advance our understanding of species’ population dynamics under different fishing strategies. The model simulates the anchovy biomass by combining an age-specific growth equation and a continuous age-structured population model based on the McKendrick–Von Foerster equation. Model predictions were compared to the biomass estimates and annual catches during the period 2003–2008. The present work provided direct evidence for the significance of the prespawning period as a critical life period for the management of anchovy stock in the Aegean Sea. It was found that the introduction of additional management measures could increase the profits in the long run for the fishery. However, for these to become apparent they will require a minimum of four years. Results also indicated that the reduction of fishing mortality directed at the spawning stock (recruitment overfishing) and the selective harvesting of younger individuals may be a plausible means of increasing stock’s total anchovy biomass. Finally, as a criterion of long-term population survival, we have considered the mathematical notation of persistence. The numerical criteria of persistence in the present model indicated that the anchovy population could be considered viable.

Collapse of South Africa's penguins in the early 21st century

The number of African penguins Spheniscus demersus breeding in South Africa collapsed from about 56 000 pairs in 2001 to some 21 000 pairs in 2009, a loss of 35 000 pairs (>60%) in eight years. This reduced the global population to 26 000 pairs, when including Namibian breeders, and led to classification of the species as Endangered. In South Africa, penguins breed in two regions, the Western Cape and Algoa Bay (Eastern Cape), their breeding localities in these regions being separated by c. 600 km. Their main food is anchovy Engraulis encrasicolus and sardine Sardinops sagax, which are also the target of purse-seine fisheries. In Algoa Bay, numbers of African penguins halved from 21 000 pairs in 2001 to 10 000 pairs in 2003. In the Western Cape, numbers decreased from a mean of 35 000 pairs in 2001–2005 to 11 000 pairs in 2009. At Dassen Island, the annual survival rate of adult penguins decreased from 0.70 in 2002/2003 to 0.46 in 2006/2007; at Robben Island it decreased from 0.77 to 0.55 in the same period. In both the Western and Eastern Cape provinces, long-term trends in numbers of penguins breeding were significantly related to the combined biomass of anchovy and sardine off South Africa. However, recent decreases in the Western Cape were greater than expected given a continuing high abundance of anchovy. In this province, there was a south-east displacement of prey around 2000, which led to a mismatch in the distributions of prey and the western breeding localities of penguins.

Long-term changes in zooplankton size distribution in the Peruvian Humboldt Current System: conditions favouring sardine or anchovy

Changes in the size distribution of zooplankton in the Humboldt Current System have been hypothesized to underlie observed changes in sardine and anchovy populations, the dominant pelagic fish species. To examine this hypothesis, the size distribution of over 15 000 zooplankton data samples collected since the 1960s was qualitatively determined. Dominance of each size group of zooplankton (small, medium and large) and of euphausiids was modelled using generalized additive models as a function of year, latitude, time of day, distance from the 200 m isobath (a surrogate for on- shelf versus off-shelf), sea surface temperature and salinity. The temporal (yr) pattern for euphausiid dominance was highly cross-correlated (i.e. was in phase) with the time series for estimated biomass of anchovy, and small zooplankton dominance with that for estimated sardine biomass. This supports the focal hypothesis based on feeding-energetic experiments, which showed energetic advantages to sardine filter feeding on smaller zooplankton and to anchovy bite feeding on larger copepods and euphausiids. Although euphausiids predominate offshore from the shelf break, anchovy biomass is generally highest on the shelf, suggesting a possible mismatch between anchovy feeding and euphausiid dominance. However, evidence concerning the offshore expansion of the anchovy range in cooler conditions, where both anchovy and euphausiids predominate, somewhat alleviates this apparent contradiction. A strong diel component to euphausiids and large zooplankton indicated diel migration for these zooplankton groups. That anchovy will preferentially eat euphausiids when they are more available (i.e. during the night and offshore) is supported by anchovy diet data.

Influence of feeding conditions on breeding of African penguins—importance of adequate local food supplies

Off the coast of South Africa, the 2 most important prey items for African penguins Spheniscus demersus are sardine Sardinops sagax and anchovy Engraulis encrasicolus, species heavily exploited by commercial fisheries. At Dassen Island, the proportion of burrows occupied for breeding by African penguins from 1995 to 2008 was affected positively by the interaction between the overall biomass of sardine and anchovy. However, sardine had a positive effect while anchovy had a negative one. This unexpected negative relationship may result from a reduced local availabil- ity of anchovy linked to the fishing effort that continued to be focussed in the vicinity of Dassen Island, while the growing anchovy stock experienced an eastward shift away from Dassen Island in recent years, creating a spatial mismatch between penguin and available anchovy. A decrease of the Southern Oscillation Index tended to advance the onset of penguins' breeding, as did an increase in sea surface temperature (SST) at the sardine and anchovy spawning grounds. An increase in SST at the nursery and spawning areas tended to decrease the penguin per capita growth rate. Earlier breeding resulted in decreased chick production, possibly because it created a temporal mismatch between chick rearing and winter availability of young-of-the-year anchovy and sardine along South Africa's west coast. The local abundance of prey is more important for breeding African penguins than overall fish abundance. Consequently, management of the purse-seine fishery should be adjusted spatially in order to ensure adequate local food supplies for breeding African penguins.

High variability in the Daily Egg Production Method parameters of an eastern Mediterranean anchovy stock: Influence of environmental factors, fish condition and population density

The recently launched Daily Egg Production Method (DEPM) surveys to estimate the spawning stock biomass (SSB) of the northern Aegean Sea anchovy stock are presented and variability in plankton and adult parameters is analyzed for the yearly applications of 2003, 2004, 2005, 2006 and 2008. Anchovy spawned mainly over the continental shelf of the Thracian Sea in the east (directly affected by Black Sea waters), and the semi-enclosed Thermaikos Gulf and Evoikos Gulf in the west. The surveyed area was therefore post-stratified into an eastern and western region and DEPM parameters, which, in certain years, differed markedly between the two areas, were estimated separately for the two strata. To increase precision of the daily egg production estimates, both eggs and yolk sac larvae were used assuming that the mortality rate does not change between the egg and yolk sac larval stage. Embryonic mortality increased as a power function of temperature. The estimation of spawning fraction was based on the postovulatory follicles (POFs) method and was particularly complicated due to the presence of strong thermoclines and diel vertical migration of the fish: POF absorption was very fast during the night, when fish were located above the thermocline (>20°C), but relatively slow during the day, when fish were close to the bottom at ∼14–15°C. Mean relative batch fecundity was significantly related to somatic condition (energy reserves) whereas spawning frequency was related to liver condition (presumably, direct food intake). In comparing daily specific fecundities (DSFs) with concurrent estimates of mesozooplankton biomass and total anchovy biomass (independently derived from acoustic sampling) evidence for strong density-dependence in DSF emerged. Density-dependent use (expansion–contraction) of the spawning habitat (SA), indexed by the ratio CV(SA)/CV(SSB), was relatively low but density-dependency of egg production CV(DSF)/CV(SSB) was particularly high in the N. Aegean Sea compared to the more productive Bay of Biscay or upwelling regions.