Contrasting multispecies patterns in larval fish production trace inter-annual variability in oceanographic conditions over the N.E. Aegean Sea continental shelf (Eastern Mediterranean)

The response of larval fish communities of the northeastern Aegean Sea (NEA) to interannual environmental changes is analyzed using data from four ichthyoplankton surveys covering the NEA continental shelf during June 1993, 1994, 1995, and 1996. Waters were significantly cooler, less saline and richer in zooplankton in 1993 and 1996 (‘cold’ years) than in 1994 and 1995 (‘warm’ years). A comparison of monthly SST series (1993–1997) between the NEA, the Marmara Sea, and the Western Black Sea revealed high correlations and similar trend components among these areas implying that oceanographic conditions over the NEA (and observed inter-annual differences) were most likely dominated by the properties and relative amount of Black Sea water inflow in the NEA. The relative composition of the larval fish community was significantly related to the ‘cold/warm’ regime and larval diversity was higher during the warm years. Larvae of the small-sized pelagic species, such as anchovy (Engraulis encrasicolus), and most mesopelagic fishes were relatively more abundant during the cold, zooplankton-rich years. Larvae of the middle-sized pelagics (Sardinella aurita, Scomber japonicus, Trachurus mediterraneaus, Auxis rochei) and certain benthopelagic species exhibited an opposite trend, i.e., they were more abundant during the warm years or absent during the cold years. Most of these species are known to be typical summer spawners (e.g., Serranus cabrilla, Lisa saliens, Trachinus draco, and Symphurus nigrescens). Co-variation in larval fish production might be indicative of similar responses among species to changing physical and/or trophic regimes.     

Distribution and abundance of fish larvae in the northern Ionian Sea (Eastern Mediterranean)

The purpose of this paper was to study the spatial distribution, abundance and composition of fish larvae in the northern Ionian Sea. Samples were collected to the 600 m depth with an electronic multinet BIONESS during the “INTERREG Italia-Grecia” oceanographic cruise carried out in March 2000 off the Apulian Italian coast. A total of 46 species of teleost early stages were collected, belonging to 38 genera and 22 families. Over 52% of the larvae identified were mesopelagic species, almost 27% were demersal and about 21% pelagic. A total of 307 myctophids, 69 clupeids and 61 gadid post-larvae dominated the community. Benthosema glaciale (mean 6.1 mm SL) was the most abundant species (21.6%), the most frequent in the samples (28.8%), and dominant in the whole study area (mean 1.4 ind/100 m³). Particular attention was given to the horizontal and vertical distribution and abundance of the three dominant post-larval species: Benthosema glaciale, Sprattus sprattus sprattus and Notoscopelus elongatus. The Pearson coefficient (R = 0.734) showed a high correlation between total zooplankton and fish larval assemblages in terms of spatial distribution abundance values. Regarding the vertical distribution of fish larvae, Sorensen’s index (S = 0.69) showed that fish larvae and total zooplankton abundance peaks co-occurred along the water column.     

长江口水域夏季鱼卵和仔稚鱼年间变化

基于2005年、2008年、2009年和2011年8月(夏季)在长江口水域(30°30'—31°45'N,121°15'—123°10'E)4个航次的浮游生物拖网资料,分析了长江口水域鱼卵和仔稚鱼的种类组成、数量分布特征及其年间变化。结果表明:4个航次采集的鱼卵和仔稚鱼鉴定到种的种类有17种,隶属于8目13科,以鲈形目种类最多,11种,其次是鲱形目,5种,其他各目种类均小于5种;种类数存在明显年间差异,2005年种类数最多(鱼卵3种,仔稚鱼8种),其次是2009年和2011年,2008年种类数最少(鱼卵1种,仔稚鱼5种)。优势种年间更替明显,长蛇鲻(Saurida elongata)、虾虎鱼(Gobiidae spp.)和中华小公鱼(Stolephorus chinensis)在2005年是优势种,2008年优势种为鳀鱼(Engraulis japonicus),2009年优势种为鳀鱼、寡鳞飘鱼(Pseudolaubuca engraulis)、虾虎鱼等,2011年虾虎鱼和小公鱼(包括小公鱼属未定种Stolephorus spp.和中华小公鱼Stolephorus chinensis)成为优势种。2005年鱼卵和仔稚鱼数量分布的密集区在嵊泗列岛附近水域,2008年鱼卵和仔稚鱼出现较少,未出现明显的数量密集区;2009年鱼卵数量较少,仔稚鱼数量较多,密集区主要分布在在长江口以外123°E附近水域;2011年鱼卵主要分布在在长江北支口门外附近水域,仔稚鱼在调查区内分布相对均匀。     

Temporal and spatial distributions of the fish larval assemblages of the Ivinheima River sub-basin (Brazil)

Fish, like other animals, choose environments for reproduction that are favorable for their offspring’s initial development. For example, these environments may be chosen to provide shelter and food. This study examined the fish larvae inhabiting the Ivinheima River sub-basin. The study aimed to (i) characterize the taxonomic composition of the larval fish fauna, (ii) analyze the structure of the larval assemblage, and (iii) verify the relationship between the larval assemblages and environmental variables. The sampling areas included three environments: the Ivinheima River, the Finado Raimundo Lagoon and the Patos Lagoon. Sampling was performed between October 2002 and March 2006 during four reproductive periods (RPs). The data were analyzed with correspondence analysis (CA) and canonical correlation analysis (CCA). A total of 120 619 larvae were collected. These larvae belonged to several species characterized by different reproductive strategies. Our results showed differences between the composition of the Ivinheima River’s assemblages, where there were more larvae of migratory fish, and the lagoons, where larvae of sedentary species were predominant. In addition, differences were found among the RPs evaluated in the Ivinheima River: the first and second RPs were characterized by milder floods and by a greater abundance of migratory piscivore larvae, whereas the third and fourth RPs had more outflow and a greater abundance of larvae of detritivore and omnivore species. We conclude that the Ivinheima River plays a significant role in the maintenance of native migratory fish stocks in the upper Paraná River basin and that the environment shows a segregation of the spatial and temporal composition and abundance of larvae related to running and flooding/standing water.     

Some biological characteristics of early larvae Dacodraco hunteri (Notothenioidei: Channichthyidae) in the western Ross Sea

Ichtyoplankton surveys were carried out in the western Ross Sea by the R/V Italica in the austral summer 1996 and 1997–1998 to study species composition and spatial distribution of larval stages of fish. One of the most abundant icefish caught was Dacodraco hunteri, a poorly known channichthyid inhabiting the high-Antarctic Zone. Based on 382 yolk-sac larvae and 13 preflexion larvae, the study was focused to estimate spatial distribution and abundance, as well as diet and growth rate. The pigmentation pattern and some morphometric measurements were also recorded for comparative purposes. The specimens were caught in relatively restricted areas located in Terra Nova Bay and north of the Ross Ice Shelf on the Challenger and Joides Basins. The standardized abundance of early larvae ranged between 0.03 and 1.72 individuals 10⁻³ m³ in 1996 and 0.16–4.53 individuals 10⁻³ m³ in 1997–1998, respectively. Fitting a linear model to the mean length increase in larvae collected in subsequent catch dates, the growth rate was estimated to be approximately 0.11 mm/day. Based on back calculation of growth rate and presumed hatch size of 11 mm, larval hatching probably took place in mid-December. Diet of preflexion larvae consisted exclusively of larvae of the pelagic nototheniid Pleuragramma antarcticum, a key species of the high-Antarctic pelagic food web. Hence, D. hunteri probably plays a more important role than previously thought in the pelagic community of the Ross Sea.     

Identification of deep-water pink shrimp abundance distribution patterns and nursery grounds in the eastern Mediterranean by means of generalized additive modelling

Generalized Additive Modelling (GAM) techniques were used to model the time series of abundance data of deep-water pink shrimp, collected during the MEDITS bottom trawl surveys carried out in the Greek seas from 1996 to 2006, as functions of the sampling location (longitude–latitude), depth and year. The life stages of the species were taken into account. All variables were highly significant, although latitude and depth had always the highest explanatory power. The total abundance was higher between 100 and 400 m of depth, with juveniles and adults being more abundant in the 100–200 m and 200–400 m depth strata, respectively. GAM prediction maps showed high abundance concentration areas for all life stages mainly in the Aegean Sea. The most important nursery ground identified was located in the Saronikos Gulf and a secondary in the Thracian Sea. Concerning the concentration areas of the adult specimens, they are located mainly in the Saronikos Gulf, the Thracian Sea, the Thermaikos Gulf, the Cretan Sea and the eastern part of the Aegean. Guest Editor: V. D. Valavanis Essential Fish Habitat Mapping in the Mediterranean     

Year-to-year variation in larval fish assemblages of the Southern North Sea

In order to test the temporal stability within and the reproducibility of larval fish assemblages between years, the larval fish assemblage at Helgoland Roads, North Sea (NE Atlantic) was quantitatively sampled almost daily from January 2003 to December 2005. The survey resulted in a total of 462 samples containing 50,632 larval fish of at least 42 taxa. In winter the larval fish assemblage was mainly dominated by larvae emerging from demersal eggs. This changed gradually to larvae hatching from pelagic eggs. Larvae from pelagic eggs dominated the ichthyoplankton assemblage in summer. A remarkably stable seasonality in terms of dominance patterns with recurring, season-specific fish assemblages was observed over the 3 years, despite substantial variation in environmental conditions such as a temperature difference of almost 20°C between summer and winter. The lesser sandeel (Ammodytes marinus), was the only species which showed significant fluctuations in abundance between the years. After removal of this species from the analysis, the dominance patterns of the remaining fish species were almost identical between years.     

Seasonal and interannual dynamics of larval abundance of <Emphasis Type="Italic">Mytilus coruscus</Emphasis> Gould, 1861 (Bivalvia: Mytilidae) in Amursky Bay (Peter the Great Bay,Sea of Japan)

Based on an analysis of the gonads, as well as the size composition and abundance of larvae in plankton, we determined the seasonal and long-term dynamics of the reproduction of the mussel Mytilus coruscus in Amursky Bay (Peter the Great Bay, Sea of Japan). Mussel gonads were in a mature condition in late July-early August; the spawning season continued from mid-August to mid-September. The larvae of this species occurred in plankton from June to September, under surface water temperatures of 14.5–23.5°C. The density of larvae in different years varied from 350 to 4500 ind/m³. Two peaks of larval abundance were observed annually, in June and September. The first peak was apparently provided by allochthonous larvae, the second, by larvae of the local population. The high density of larvae of M. coruscus in the plankton of Peter the Great Bay enabled us to consider this species as a potential object for mariculture.     

Relationships between coral reef substrata and fish

 The objective of this work is to identify which substrata characteristics (such as coral morphology, coral diversity, coral species richness, percentage coverage by live coral or by algae) influence the structure and abundance of fish communities. The study was carried out at Reunion Island, Indian Ocean, where six sites were sampled in two zones (reef flat and outer reef slope). Quantitative data were collected by visual census techniques, along a linear transect of 50 m for the substratum, and a belt of 50×2 m for the fish communities. Correspondence analysis (CA) and an optimising cluster analysis, called dynamic clustering method (DCM) were used to describe and compare fish assemblages with the benthic composition. The relationships between benthic and fish communities were examined using the classes revealed by the partitioning of the substratum with DCM. This partitioning allowed us to derive four classes of substratum: the non-disturbed reef flat, the non-disturbed outer reef slope, the perturbed reef habitat and the reef pass. The analysis of the partitioning based on the coral variables suggests that there are significant relationships between benthic and fish assemblages. Accepted: 26 July 1996     

Summer Ichthyoplankon in Onega Bay of the White Sea: Species Composition and Spatial Distribution

Data on the species composition and distribution of ichthyoplankton in Onega Bay of the White Sea are presented for June–July 2007, 2010–2012, and 2015–2016. In the ichthyoplankton, the specimens of the early developmental stages of 21 fish species were registered; the larvae of the White Sea herring Clupea pallasi marisalbi, capelin Mallotus villosus, and Pacific sand lance Ammodytes hexapterus were the most abundant. It is shown that the northwestern and southeastern zones, distinguished in Onega Bay by hydrophysical parameters, also differ in species composition and in ichthyoplankton abundance.     

Fish assemblages on artificial and natural reefs in the Flower Garden Banks National Marine Sanctuary, USA

 Visual censusing was used to characterize fish assemblages on artificial and natural reefs located within the boundaries of the Flower Garden Banks National Marine Sanctuary (FGBNMS) in the northwestern Gulf of Mexico. Emphasis was placed on determining spatial and temporal patterns in habitat utilization by fishes on an offshore artificial reef (Mobil Platform HI-A389A). Overall, 43 species were observed during diurnal surveys in the upper 24 m of the artificial reef. Midwater pelagic fishes (i.e., carangids and scombrids) accounted for over 50% of all taxa enumerated on the artificial reef; however, these taxa were transient members of the assemblage and were observed infrequently. Labrids, pomacentrids, and serranids were the dominant reef-dependent taxa. Distinct trends in vertical, diel, and seasonal abundances were observed for juvenile and adult fishes. Of the three designated depth zones (upper 1.5–9.0, middle 9.0–16.5; lower 16.5–24.0 m), abundance and species diversity were lowest in the upper zone. Nocturnal counts were characterized by a marked reduction or complete absence of most species, due in part to twilight cover-seeking and movement activities. Seasonal variation in community composition and species abundance (May versus September) was primarily due to recruitment of juveniles (0-age fishes) to the artificial reef in late summer. Increases in total fish abundance (all taxa combined) coincided with both increasing habitat rugosity and degree of fouling. Species richness on natural coral reefs in the FGBNMS was higher than on the artificial reef. Unlike the artificial reef, fish assemblages on the natural reefs were dominated by a single family (Pomacentridae) which accounted for over 50% of all individuals observed. Accepted: 1 August 1996     

Zooplankton distribution and diversity in a frontal area of the Aegean Sea

This study was carried out in the northern Aegean Sea during late summer and spring. The aim was to examine the spatial and temporal distribution of the zooplankton community across a dynamic frontal area and to investigate how the oceanographic heterogeneity structures the composition of the zooplankton assemblages. The low-salinity and cold Black Sea water coming from the Dardanelles Strait is modified by mixing with the underlying warm and saline Aegean water. These hydrological features result in a pronounced thermohaline front in the northern Aegean Sea throughout the year. In both seasons, zooplankton was collected using both 45 and 200 µm mesh plankton nets. A high abundance of zooplankton was observed in the surface layer at the stations closest to the Dardanelles Strait on the stratified side of the front. The zooplankton distribution and community structure in the northern Aegean Sea were strongly influenced by the hydrological features. The frontal structure acts as a boundary for the zooplankton community. The surface layer at the stratified stations had the lowest copepod diversity, from where it increased with depth and horizontally as the stratification weakened outside of the front. The total abundance of zooplankton collected with the 200 µm net was between two and 20 times lower than samples taken with the 45 µm net. The most pronounced differences were observed for the adults and copepodids of the small genera Oithona, Oncaea and Microsetella. Thus, to manage and understand the transfer of primary production up the food chain in the Aegean Sea, the smaller fraction of copepods should be taken into account in future investigations.     

Predicting the structure and diversity of young-of-the-year fish assemblages in large rivers

1. Interactions between environmental variables and 0+ fish assemblages in the upper River Garonne (France) were quantified during late August 1995.
2. The abundance and diversity of the fish assemblages in floodplain channels were modelled using Artificial Neural Network (ANN) analysis and nine variables: the abundance of the six dominant species, fish specific richness, overall abundance of 0+ fish and the Shannon index of diversity. Multiple regression analysis was also used to assess ANN performance.
3. Using 596 samples, correlation coefficients ( r adjusted) between observed and estimated values of the nine dependent parameters were all highly significant ( P < 0.01). Expected values from the tested data were significantly related to the observed values. The correlation coefficient between observed and estimated values ( r ) varied from 0.70 to 0.85.
4. The ANN provided a high quality prediction, despite the complex nature of the relationship between microhabitat composition and fish abundance.
5. Garson's algorithm was used to provide the explanatory power needed in ecology when using black-box models. Parameters contained in the models (i.e. weighting) were used to determine the relative contributions of explanatory variables and thus to ascertain the structure of fish communities.     

Fish larvae association in a Mexican Caribbean bay

Interannual ichthyoplankton variation, was analyzed in Bahía de la Ascensión, Mexico, during December of four consecutive years (1994-1997). A total of 32 families, 35 genera and 21 species of fish larvae were identified. The most abundant fish larvae were the Gobiidae followed by the Callionymidae, Clupeidae and Tetraodontidae. Larval diversity was low when compared with other periods ("dry" and "rainy"). Three spatial associations (internal, medium and external) were found in December 1994 and 1995. In 1996-1997, stations of the inner and outer parts of the bay were mixed. The dominant families characterized most of the faunal associations. Egg density was highest in the external zone of the bay, whereas larvae were most abundant in the inner area. Major factors affecting the fish larval assemblages during December (1994-1997) in Bahía de la Ascensión seem to be related to the nursery areas location and to the tropical fishes reproductive period.     

Habitat discrimination of juvenile sardines in the Aegean Sea using remotely sensed environmental data

Despite the importance of the recruitment process for small pelagic fish and the high economic importance of European sardine (Sardina pilchardus, Walbaum 1792) in the Mediterranean Sea, knowledge on the distribution and environmental characteristics of its nursery grounds is very limited. In the present study, we used pelagic trawl data collected during 1995–2006 to explore the spatial distribution of sardine juveniles in the Aegean Sea in early summer. Based on sardine abundance per length class, a cluster analysis was initially used to define hauls dominated by juveniles. In a subsequent step, Discriminant Function Analysis (DFA) was applied to discriminate stations with high relative abundance of juveniles using satellite environmental data and bottom depth. The parameters contributing mostly to the discrimination of juvenile grounds were sea level anomaly, photosynthetically active radiation, sea surface temperature, chlorophyll-α and bottom depth. The classification functions of DFA were finally used to post classify unsampled areas in the Greek Seas and the Mediterranean Sea in order to map grounds that meet characteristic environmental conditions for young sardine. Such areas were mostly located inshore, in semi-closed productive areas and often in proximity to river mouths, a pattern that is generally supported by existing information. Guest editor: V. D. Valavanis Essential Fish Habitat Mapping in the Mediterranean     

Comparative characteristics of the ichthyoplankton of lagoon lakes of the south-eastern part of Sakhalin

Ichthyoplankton surveys are made in lagoon water bodies of the south-eastern part of Sakhalin (the Vavai-Chibisan system of lakes, Lake Tunaicha, Lake Izmenchivoe) from April until November 2002–2007. Comparative characteristics of ichthyoplankton complexes in the ice-free period is given. In the investigated lagoon lakes, differences in the species composition of the ichthyoplankton by the number and time of appearance of the maxima of abundance of eggs and larvae are noted, and also related to morphological structure and hydrological conditions of water bodies. In lagoon lake Izmenchivoe with a salinity not less than 26‰, the eggs and larvae of marine fishes only takes place while, in Vavai-Chibisan lakes, that of freshwater fishes only takes place. In brackish lake Tunaicha, the lowest number of fish species reproduce. In the Vavai-Chibisan system and in Lake Izmenchivoe, one maximum of abundance of ichthyoplankton in June is recorded and, in Lake Tunaicha, two maxima (the highest in June and less expressed in August) are recorded. Irrespective of the species composition, the ichthyoplankton complexes of lagoon lakes have general traits determined by hydrological conditions of water bodies and by their general origin and geographic situation: prevalence of eggs and larvae of low boreal fish species, the maximum species diversity in the late spring-early summer, and decrease of abundance in cooler years.     

Shifts in the composition and distribution of Pacific Arctic larval fish assemblages in response to rapid ecosystem change

The Pacific Arctic marine ecosystem has undergone rapid changes in recent years due to ocean warming, sea ice loss, and increased northward transport of Pacific-origin waters into the Arctic. These climate-mediated changes have been linked to range shifts of juvenile and adult subarctic (boreal) and Arctic fish populations, though it is unclear whether distributional changes are also occurring during the early life stages. We analyzed larval fish abundance and distribution data sampled in late summer from 2010 to 2019 in two interconnected Pacific Arctic ecosystems: the northern Bering Sea and Chukchi Sea, to determine whether recent warming and loss of sea ice has restricted habitat for Arctic species and altered larval fish assemblage composition from Arctic- to boreal-associated taxa. Multivariate analyses revealed the presence of three distinct multi-species assemblages across all years: (1) a boreal assemblage dominated by yellowfin sole (Limanda aspera), capelin (Mallotus catervarius), and walleye pollock (Gadus chalcogrammus); (2) an Arctic assemblage composed of Arctic cod (Boreogadus saida) and other common Arctic species; and (3) a mixed assemblage composed of the dominant species from the other two assemblages. We found that the wind- and current-driven northward advection of warmer, subarctic waters and the unprecedented low-ice conditions observed in the northern Bering and Chukchi seas beginning in 2017 and persisting into 2018 and 2019 have precipitated community-wide shifts, with the boreal larval fish assemblage expanding northward and offshore and the Arctic assemblage retreating poleward. We conclude that Arctic warming is most significantly driving changes in abundance at the leading and trailing edges of the Chukchi Sea larval fish community as boreal species increase in abundance and Arctic species decline. Our analyses document how quickly larval fish assemblages respond to environmental change and reveal that the impacts of Arctic borealization on fish community composition spans multiple life stages over large spatial scales.     

Larval feeding of Chionodraco hamatus (Pisces, Channichthyidae) in the Ross Sea and its relation to environmental conditions

Feeding habits of early life stages of the channichthyid Chionodraco hamatus were investigated on samples collected in the western Ross Sea in early summer of 1996 and 2004. The stomach content analysis was carried out on larval and postlarval specimens ranging from 14 to 39 mm SL. Unlike larvae and juveniles of other channichthyids, which elsewhere largely rely on early life stages of Antarctic krill or ice krill, no euphausiids were found in the stomach contents of C. hamatus, except for a single large individual of Thysanoessa macrura. In both years, dietary composition consisted almost exclusively of notothenioid fish larvae. Early larvae of Pleuragramma antarcticum overwhelmingly dominated the diet in terms of abundance, biomass and frequency of occurrence, accounting for 98.4% of the index of relative importance (IRI). Other fish larvae consumed occasionally in small amount were Trematomus lepidorhinus, T. scotti and C. hamatus itself. As a result, the feeding strategy of C. hamatus was considerably shifted toward specialization, relying on relatively few taxa of prey, each of them showing a high prey-specific abundance. Comparing both dietary composition and feeding strategy of C. hamatus in the two different sampling years, several differences were observed, probably due to different environmental conditions, mainly linked to a significant delay of ice retreat and formation of the Ross Sea polynya verified in the 2003–2004 summer season.     

Larval fish assemblages and geostrophic circulation in Bahia de La Paz and the surrounding southwestern region of the Gulf of California

We analyze spatial–temporal relationship between larvalfish assemblages and geostrophic surface flow in Bahíade La Paz and the neighboring Gulf of California (May, Julyand October 2001 and February 2002). The analysis of fish larvaedistribution in relation to geostrophic circulation and hydrographyis an innovative interdisciplinary approach for the understandingof fish larvae ecology. The Bray–Curtis Index definedtwo larval fish assemblages with spatial–temporal variations:coastal assemblage dominated by epipelagic coastal species (e.g.Sardinops caeruleus) and oceanic assemblages—oceanic andtransitional oceanic assemblages both dominated by mesopelagicspecies (e.g. Vinciguerria lucetia and Benthosema panamense)but with different larval abundance. The assemblage variationsappear to be related to water exchange between the bay and theGulf through the North Mouth. During July–October, thegeostrophic flow through the entrance is strong, and the oceanicassemblages spread in the whole bay, whereas during February–Maywhen the geostrophic transport is weak, the coastal assemblageis distributed over the whole bay. The strong summer–autumnwater interchange between bay and gulf is in agreement withthe annual evolution of the surface water properties insidethe bay, from high-salinity Gulf of California Water duringwinter–spring to fresher Tropical Surface Water duringsummer–autumn, when the highest species number was recorded.     

Ichthyoplankton in the plankton community of the Crimean Peninsula shelf zone (Black Sea) in July 2010

Data on the species composition and quantitative distribution of ichthyoplankton, zooplankton, and jelly fish macroplankton from different areas of the Crimean Peninsula shelf zone in July 2010 are presented. It has been shown that the structure of species composition and the maximum abundance of ichthyoplankton are comparable to those in July 1988, i.e., until negative changes in the ecosystem of the Black Sea shelf, which took place in the 1990s. The average abundance of ichthyoplankton in July 2010 corresponds to the lowest long-term data obtained in July 1950s and 1960s. The effect produced by organochlorine contaminants and by the abundance of jelly fish macroplankton on the survival of pelagic fish eggs and fish larvae is studied. The prevalence of juvenile copepods in the guts of fish larvae, as well as the low proportion of fish larvae with empty stomachs (<10%), if compared to the data obtained in the 1990s (50–90%), point to the favorable trophical conditions for fish larvae in the area of investigation.