Japanese Anchovy Engraulis Japonicus Research Articles

Current status and trends for commercial stock of japanese anchovy <i>Engraulis japonicus</i> (Engraulidae) in Russian waters of the Japan Sea

Japanese anchovy Engraulis japonicus of the Tsushima Current stock migrate to the northwestern Japan Sea in warm season and play there an important role in the pelagic food web. According to survey and fishery data, the commercial stock of this species declines recently that determines decreasing of intensity of its migrations into the Russian waters, though its level is still appropriate for fishery. The anchovy releases ashore occur sometimes on the Far-Eastern coast, likely in cases of unstable environments that have become more frequent under climate change. More intense research of the pelagic ecosystem in the northwestern Japan Sea is necessary to clarify the status of fishery resources formed by southern migrants, including anchovy, sardine and mackerel.

Growth–feeding linkage in small pelagic fish larvae in the Kii Channel, Japan

AbstractThe linkage between growth rate and feeding success has been shown to strengthen the effects of early growth rate on later growth rate in the early life history of fish. However, the growth–feeding linkage largely remains to be tested at the individual level within the same populations/cohorts. We examined the growth–feeding linkage for multiple populations/cohorts in Japanese anchovy Engraulis japonicus larvae and Pacific round herring Etrumeus micropus larvae, through otolith microstructure analysis, based on samples collected from the commercial fishery for larval fish in the Kii Channel, Japan. The three growth–feeding mechanisms, which are based on the respective potential advantages of larger somatic size, higher growth rate, and earlier morphological development for achieving feeding success, were tested to understand how growth rate relates to feeding success. The “somatic size” mechanism was supported for all of six samples for anchovy larvae and three of four samples for round herring larvae. The “growth rate” mechanism was supported for two of six samples for anchovy larvae and three of four samples for round herring larvae. The “morphological development” mechanism was supported for three of four samples for anchovy larvae and all of three samples for round herring larvae. Overall, the present analysis supported the growth–feeding linkage but revealed the dynamics of the growth–feeding mechanisms. All the mechanisms were shown to operate at least for certain populations/cohorts, but none of them were universally effective over all populations/cohorts across the two species. Understanding the dynamics of the growth–feeding mechanisms would provide precious hints for considering strategies of predicting recruitment dynamics.

Seasonal variability in the otolith and somatic size relationship of Japanese anchovy larvae: Counter effects of somatic growth and temperature

Otolith microstructure analysis has played an essential role in understanding the recruitment mechanisms of fish. Despite the fundamental assumption of a close correlation between otolith size and somatic size in growth back-calculations, numerous studies have shown that somatic growth and temperature have negative and positive effects on otolith size at the same somatic size, respectively. However, few studies have investigated the effects of somatic growth and temperature on otolith and somatic size relationships at intra- and inter-cohort levels in the same study framework. The present study investigated the effects of somatic growth and temperature on the seasonal variability in the otolith and somatic size relationship in Japanese anchovy Engraulis japonicus larvae collected from multiple seasonal cohorts throughout the year in the Kii Channel, Japan. The otolith and somatic size relationships were strong within each seasonal cohort sample (R2 = 0.771–0.949), but the relationship became weaker when all the seasonal data were pooled (R2 = 0.571). Relative otolith size at a given somatic size (ROS) was negatively related to somatic growth rates within each seasonal cohort sample (i.e., at the intra-cohort level), but the relationship became weak when all the data were pooled. On the contrary, sea temperature had positive effects on ROS, which would explain the seasonal variability in the otolith and somatic size relationship. The multiple regression analysis showed that temperature influenced ROS almost six times more than somatic growth. Overall, the present study demonstrated that an uncoupling in the otolith size–somatic size relationship was generated by the counter effects of somatic growth and temperature. The observed counter effects should be taken into account in estimating past larval growth for larvae obtained from different environmental conditions.

Morphological differences yet genetic similarity among seasonal cohorts of Japanese anchovy during the early life stages in the Kii Channel

Abstract Species in the genus Engraulis show extensive intraspecific as well as interspecific morphological and genetic diversity. Since morphological differences do not necessarily correspond to genetic differences, it is necessary to clarify the relationship between morphological differences and genetic differences for a better understanding of the population structure. Fish morphology at a given standard length differs between cohorts of Japanese anchovy Engraulis japonicus during the early life stages in the Kii Channel, but it is unknown whether the differences are caused by genetic differences or not. The Kii Channel includes the boundary between the Pacific (southern side of the Kii Channel) and the Seto Inland Sea stocks (northern side), but stock separation is based primarily on demographic characteristics. In the present study, genetic analyses were conducted to examine the genetic differences among samples (month and area) based on mitochondrial DNA cytochrome b region (Cyt b), control region (CR) and microsatellite markers. AMOVA revealed that the percentage of genetic variation among samples was low at 0.11% for Cyt b, 0.30% for CR and 0.00% for microsatellite, and no significant genetic variation was observed among samples. Although two clades were identified in the unrooted neighbour-joining tree for Cyt b and CR, both Cyt b and CR sequences were similar between months and between areas. Accordingly, the morphological differences among cohorts can be attributed to phenotypic plasticity. Additionally, there were no genetic differences between samples from the southern side and the northern side of the Kii Channel, suggesting strong genetic connectivity in these areas.

Environmental DNA in the Kuroshio reveals environment-dependent distribution of economically important small pelagic fish

IntroductionSmall pelagic fishes constitute large proportions of fisheries and are important components linking lower and higher trophic levels in marine ecosystems. Many small pelagic fishes in the Northwest Pacific spawn upstream in the Kuroshio and spend their juvenile stage in the Kuroshio Front area, indicating that the Kuroshio Current system impacts their stock fluctuations. However, the distribution of these fish relative to the Kuroshio has not been determined due to dynamic spatio-temporal fluctuations of the system. Here, the recent development of environmental DNA (eDNA) monitoring enabled us to investigate the distribution patterns of four economically important small pelagic fishes (Japanese sardine Sardinops melanostictus, Japanese anchovy Engraulis japonicus, chub mackerel Scomber japonicus, and blue mackerel Scomber australasicus) in the Kuroshio Current system. MethodsThe influence of environmental factors, such as sea water temperature, salinity, oxygen concentration, chlorophyll-a concentration, and prey fish on the occurrence and quantity of target fish eDNA was analyzed using generalized additive models. In addition, the detection (presence) of target fish eDNA were compared between the offshore and inshore side areas of the Kuroshio axis.ResultsSea water temperature showed important effect, especially on the distribution of Japanese sardine and Japanese anchovy, whereas the distribution pattern of chub mackerel and blue mackerel was greatly influenced by the eDNA quantity of Japanese sardine and Japanese anchovy (especially potential prey fish: Japanese anchovy). In addition, we found that the four target fish species could be observed in areas on the inshore side or around the Kuroshio axis, while they were hardly found on the offshore side.ConclusionBased on eDNA data, we succeeded in revealing detailed spatial distribution patterns of small pelagic fishes in the Kuroshio Current system and hypothesized predator–prey relationships influence their distribution in small pelagic fish communities.

Metabolic Rates of Japanese Anchovy (Engraulis japonicus) during Early Development Using a Novel Modified Respirometry Method.

The allometric relationship between metabolic rate (VO2) and body mass (M) has been a subject of fascination and controversy for decades. Nevertheless, little is known about intraspecific size-scaling metabolism in marine animals such as teleost fish. The Japanese anchovy Engraulis japonicus is a planktotrophic pelagic fish with a rapid growth and metabolic rate. However, metabolic rate measurements are difficult in this species due to their extremely small body size after hatching. Herein, the metabolic rate of this species during its early developmental stage was measured for 47 individuals weighing 0.00009-0.09 g (from just after hatching to 43 days old) using the micro-semi-closed method, a newly modified method for monitoring metabolism developed specifically for this study. As a result, three distinct allometric phases were identified. During these phases, two stepwise increases in scaling constants occurred at around 0.001 and 0.01 g, although the scaling exponent constant remained unchanged in each phase (b^ = 0.683). Behavioral and morphological changes accompanied the stepwise increases in scaling constants. Although this novel modified respirometry method requires further validation, it is expected that this study will be useful for future metabolic ecology research in fish to determine metabolism and survival strategy.

Biological interactions potentially alter the large-scale distribution pattern of the small pelagic fish, Pacific saury Cololabis saira

We aimed to understand the effect of biological interactions on the distribution of small pelagic fishes. Surveys were conducted during 2003-2019 using sea surface trawl nets in the western and central North Pacific Ocean, covering an area between 143° E and 165° W, to estimate the distributions of 4 small pelagic fishes: Pacific saury Cololabis saira, Japanese sardine Sardinops melanostictus, chub mackerel Scomber japonicus, and Japanese anchovy Engraulis japonicus. These species are potential competitors, as they all occupy a similar niche. Japanese anchovy was abundant during 2003-2012, while Japanese sardine and chub mackerel were abundant during 2013-2019. Only Pacific saury was distributed throughout the survey area, while the others occurred within the area west of 180° longitude (WA). Pacific saury and its potential competitors showed adjacent distributions, with a slight overlap along sea surface temperature gradients in the WA. This distribution pattern remained even when Japanese sardine expanded its distribution to colder waters and increased in abundance after 2013, resulting in a shift in the distribution of Pacific saury to colder waters and a period of high densities of Japanese sardine. Such a distribution shift of Pacific saury was not observed in the area east of 180° longitude, where no Japanese sardine was observed. These results suggest the possibility that biological interactions such as inter-species competition can be an important factor in determining the distribution of small pelagic fishes.

Revisiting the role of early life growth for survival potential in three clupeoid species

AbstractJohan Hjort's “critical period” hypothesis, which postulates that year‐class strength is determined in the short period following the onset of exogenous feeding, has rarely been supported by empirical data. Instead, the current understanding is that recruitment is determined by cumulative mortality throughout early life. Recent studies relied on the measure of growth autocorrelation derived from otolith daily increment widths to test the link between growth rate achieved during the post‐hatch period and during subsequent phases of the larval stage. Based on this approach, we revisit the role of larval growth in driving survival potential in three clupeoid species: Japanese sardine Sardinops melanostictus, Japanese anchovy Engraulis japonicus, and Pacific round herring Etrumeus micropus throughout the larval stage, using a combination of published datasets of otolith increment widths. Strong growth autocorrelation was detected for all three species throughout the larval stage, suggesting that initial growth determines to some extent growth rates achieved later in life. The extent of autocorrelation was reduced in sardine relative to anchovy and round herring at older ages. This interspecific difference could be attributed to differences in sensitivity to variability of environmental factors such as water temperature and food availability. The present findings suggest that the effect of early growth rate persists into later life stages for driving survival potential, which could reconcile the classic concept of “critical period” and the current “growth–survival” paradigm.

Development of a prey-predator species distribution model for a large piscivorous fish: A case study for Japanese Spanish mackerel Scomberomorus niphonius and Japanese anchovy Engraulis japonicus

One of the major challenges of species distribution models (SDMs) is incorporating the influence of prey on the predator. An ensemble modeling approach, the prey-predator species distributabion model (PPSDM), uses environmental variables (sea surface temperature, bathymetry, sea surface salinity, and sea surface current) and a biotic variable (predicted prey distribution: Japanese anchovy) to predict a piscivorous fish (Japanese Spanish mackerel) habitat in the China Seas. PPSDM comprised selected preferable single algorithms from nine algorithms, including tree-based models, machine learning models, regression models, an envelope-style method, and a classification model. Compared with that obtained when using habitat without the Japanese anchovy distribution, the regression models, machine learning models and a classification model have significant improvements. However, tree-based models have only slightly improved. The PPSDM results well reflected the ontogenetic migration of Japanese Spanish mackerel. We found that the wintering ground was distributed in regions with temperatures between 11 and 17 °C and salinities between 33.6 and 34.1. The bottom topography was also closely correlated with Japanese Spanish mackerel, and the suitable habitat was at 50–100 m isobaths as topography determined the position of isotherms (11, 17 °C), salinity isolines (33.6, 34.1), and fronts (temperature, salinity) in winter. The relationships among different climatic indices, temperature, and Japanese Spanish mackerel were analyzed. We found that the East Asian monsoon significantly influenced the Japanese Spanish mackerel habitat by affecting temperature variation. In the future, the suitable habitat of Japanese Spanish mackerel is projected to decrease by 21%, 28%, 36%, and 42% under RCP2.6, RCP4.5, RCP6.0, and RCP8.5, respectively. The Japanese Spanish mackerel in the northern Yellow Sea is projected to experience the ‘cul de sac’ effect, which would drive this species toward local extinction. The Japanese Spanish mackerel in the China Seas will probably shift northeastward through the Tsushima Strait, and the Sea of Japan may form the main habitat at the end of the century.

Density-dependent attributes of schooling in small pelagic fishes.

Many small pelagic fishes obligately form schools; some of these schools reach remarkable sizes. Although the school is a fundamental and important ecological unit and is the site of biological interactions such as competition and predation, information on schooling processes in the field remains scarce. Here, we examined the quantitative relationships between population density and school size, the number of schools, and other school characteristics (i.e. packing density, volume, and cross-sectional area) in three species of small pelagic fishes: Japanese anchovy Engraulis japonicus, Japanese sardine Sardinops melanostictus, and chub mackerel Scomber japonicus. We found that school size increased almost linearly with population density, whereas the number of schools and other characteristics increased non-linearly with population density, whereby the rate of increase slowed radically as population density increased. These results indicate that, at low population densities, an increase in density causes an increase in both school size and the number of schools, whereas at higher population densities, an increase in density triggers the formation of larger schools rather than more schools. Furthermore, we found that the shapes of the relationships of all school characteristics with population density differed amongst species. Our results indicate that the schooling behaviour of small pelagic fishes is density-dependent, and responses to changes in density are species-specific. Our results provide insight into how biological interactions such as intra- and inter-specific competition and predator-prey interactions mediate the density-dependent processes that underlie the population dynamics and community structure of small pelagic fishes in marine ecosystems.

Spawning overlap of Japanese anchovy Engraulis japonicus and Japanese Spanish mackerel Scomberomorus niphonius in the coastal Yellow Sea: A prey–predator interaction

AbstractJapanese Spanish mackerel Scomberomorus niphonius and Japanese anchovy Engraulis japonicus are typical predator and prey species, respectively, with high commercial values in the China seas. However, the interspecific interaction, particularly the relationship between the two species during early life stages, is unclear. Here, based on ichthyoplankton surveys in the coastal Yellow Sea during 2013–2018, we analyzed the relationship between the two species based on egg occurrence and abundance in the context of species interaction. Spawning optimal temperature were examined for anchovy (13.0–18.0°C) and mackerel (15.0–20.0°C) based on egg occurrences and abundances in relation to sea surface temperature. We confirmed the peak spawning periods (May and June) and primary spawning areas (Haizhou Bay) for both mackerel and anchovy based on spatiotemporal distributions of two species eggs. Mackerel showed a high spawning overlap with anchovy, and anchovy egg abundance were also higher in overlap areas. Anchovy egg abundance may be more important for mackerel spawning than environmental variables, suggesting the significance of prey for predators during early recruitment. The temperature also has important effects on mackerel spawning and could be a threshold affecting mackerel spawning activity. Mackerel might have evolved a spawning strategy of short‐term spawning timed to coincide with the peak spawning of anchovy in the coastal Yellow Sea. These results highlight the effects of interspecific relationships on spawning strategy of anchovy and mackerel in the coastal Yellow Sea and may provide some insights for early recruitment studies of piscivorous fishes in the context of the match–mismatch hypothesis.

Effects of formalin preservation on egg size of small pelagic fish as major target species in ichthyoplankton surveys

AbstractPreservation is critical for egg and larval samples from ichthyoplankton surveys. As growing interest is directed toward maternal effects on egg quality, historical collections of egg samples in formalin are potentially invaluable materials but concerns about the effects of formalin preservation need to be clarified. The present study examined effects of formalin preservation on egg size of Japanese sardine Sardinops melanostictus, chub mackerel Scomber japonicus and Japanese anchovy Engraulis japonicus over a long period (30–36 months). Overall, the egg sizes slightly decreased in a couple of months after preservation but then recovered to be at a similar level to the live eggs for diameters of spherical eggs of sardine and mackerel and short diameters of ellipsoidal eggs of anchovy, although a caveat lies in unstable and slightly increasing patterns in long diameters of anchovy eggs. No substantial differences were found between 5% and 10% formalin solutions. For practical purposes, we conclude that no correction factors are required for using the measurements of egg samples preserved in formalin over a long period. Assuming the applicability to congeneric species, the information presented here supports the validity of previous studies and will promote future studies on egg size variability in small pelagic fish based on historical collections of egg samples preserved in formalin in various regions of the world.

The Diet Composition and Ingested Plastics of Laysan and Black-Footed Albatrosses Incidentally Captured by the Pelagic Longline Fishery in the Western North Pacific

The stomach contents (food and ingested plastics) of Laysan Albatross Phoebastria immutabilis and Black-footed Albatross P. nigripes were examined by necropsy analysis of birds caught as bycatch in the pelagic longline fisheries in the Western North Pacific. The contents were classified separately for the proventriculus and gizzard. Undigested fish and cephalopods were found in the proventriculus, while hard objects such as cephalopod beaks, plastics, and pebbles were found in the gizzard. This indicates that the retention time of soft tissues in fish or cephalopods differs from that for hard objects. The main prey of both albatrosses consisted of mesopelagic cephalopods such as Cranchiidae, Gonatidae, Histioteuthidae, and Onychoteuthidae species. Laysan Albatrosses also foraged on small teleosts (Japanese Anchovy Engraulis japonicus and some Myctophidae fishes) as major prey items. The estimated dorsal mantle length of cephalopods preyed upon by the albatrosses was below 200 mm, which was smaller than the mature sizes of those cephalopods and the size class mainly preyed upon by cetaceans. This implies that the albatrosses may forage on immature cephalopods floating in the surface layer. Ingested plastics were found in 71.8% of Laysan and 31.8% of Black-footed Albatrosses and plastic fragments were the most abundant.

Evidence of bottom-up effects of climate on Japanese anchovy (Engraulis japonicus) in the western North Pacific

Evidence of bottom-up effects of climate on Japanese anchovy (Engraulis japonicus) in the western North Pacific

Length–length and Length–weight Relationships for Four Dominant Small Pelagic Fishes in the Kuroshio–Oyashio Current System

Length–length and length–weight relationships in various length measurement standards were estimated for dominant small pelagic fishes in the Kuroshio–Oyashio current system (Japanese sardine Sardinops melanostictus, Japanese anchovy Engraulis japonicus, chub mackerel Scomber japonicus, and spotted mackerel Scomber australasicus). Fish samples were collected from surface–midwater trawl surveys and commercial purse-seine fisheries between September and October of 2020 in the western North Pacific. Total length (TL), fork length (FL), and standard length (SL) were measured to 0.01 cm, and total body weight (W) was measured to the nearest 0.01 g for each individual. All length–length relationships (TL–FL, TL–SL, and FL–SL) were highly significant (p 0.98 in all species. Length–weight relationships (W–TL, W–FL, and W–SL) were also highly significant (p 0.98 in all species. This study provides new comprehensive information on length–length and length–weight relationships in various length measurement standards for the four small pelagic fish species. These data will be useful references for biological studies and stock assessments of these small pelagic fishes.

Ammonia tolerance of Japanese anchovy Engraulis japonicus: Implications for cost reduction in a skipjack pole-and-line fishery

Ammonia tolerance of Japanese anchovy Engraulis japonicus: Implications for cost reduction in a skipjack pole-and-line fishery

Feeding ecology of juvenile Pacific bluefin tuna

The feeding ecology of juvenile Pacific bluefin tuna (PBF) Thunnus orientalis in the Sea of Japan was examined to better understand the survival process before fishery recruitment. Stomach content analysis showed that the main prey items were fish, especially Japanese anchovy Engraulis japonicus, cephalopods, mainly small squid Enoploteuthis chunii, and copepods. In addition, although both fish prey and cephalopods were important for large juveniles (100–300-mm fork length, FL), the stomach contents of small juveniles (40–99 mm FL) mainly included fish prey. The strong possibility of cannibalism was also suggested, although its contribution to total food consumption was limited. The size of fish prey increased significantly with the FL of PBF. Nitrogen isotope ratios (i.e. δ15N) also increased with increasing FL (12–227 mm), suggesting that the trophic level increases rapidly during the juvenile stage because of the active feeding on fish by PBF. Such feeding habits, especially feeding on fish, would be essential to achieve a high growth rate and would therefore be associated with the survival of juvenile PBF before recruitment in the Sea of Japan. In addition, PBF exhibited a decrease in stomach fullness during the night-time, and their estimated gastric evacuation rate was 0.36 h–1.

Spawning strategy of Japanese anchovy Engraulis japonicus in the coastal Yellow Sea: Choice and dynamics

AbstractUnderstanding the relationships between hydrodynamics and the spawning activities of small pelagic fishes is crucial for understanding their recruitment dynamics and for fisheries management. Here, we clarify the effects of marine environmental factors and the associated hydrodynamic processes on the spawning activities of the Japanese anchovy Engraulis japonicus in the coastal Yellow Sea using data from in situ ichthyoplankton surveys (7 recent years), a hydrodynamic model and satellite remote sensing. We confirmed the peak spawning period (May and June) and primary spawning location (Haizhou Bay). We defined the ‘spawning temperature optima’ hypothesis to identify the optimal spawning temperature (13.0–18.0°C) for the Japanese anchovy based on egg occurrence and abundance. We detected fortnightly variation in spawning behaviour, which peaked after the spring tide. Anchovy eggs showed evident aggregation in the nearshore upwelling area during May and June, while strong upwelling in July may cause a negative spawning‐site choice in upwelling zone. These findings clarify the effects of hydrodynamics on the spawning behaviour of the Japanese anchovy in the coastal Yellow Sea.

Evaluation of Muscle Post-mortem Changes of Japanese Anchovy Engraulis japonicus and Round Herring Etrumeus teres and Recovery of ATP Concentration of Japanese Anchovy Following Brief Rest in a Fish Cage

Evaluation of Muscle Post-mortem Changes of Japanese Anchovy Engraulis japonicus and Round Herring Etrumeus teres and Recovery of ATP Concentration of Japanese Anchovy Following Brief Rest in a Fish Cage

Microscale stable carbon and oxygen isotope measurement of individual otoliths of larvae and juveniles of Japanese anchovy and sardine

The stable carbon and oxygen isotope ratios (δ13C and δ18O) of fish otoliths are useful proxies for habitat and physiological conditions affecting fish during their lifetime. To understand the ecology of the early life stage specimens of Japanese sardine Sardinops melanostictus and Japanese anchovy Engraulis japonicus collected from Toyama Bay, Japan, we used a submicrogram-scale stable isotopic analytical system called MICAL3c to investigate otolith δ13C and δ18O values of larvae and juveniles. The otolith δ13C and δ18O values of the two species showed a decreasing trend with ontogeny. Temperatures estimated from otolith δ18O values suggest that otolith δ18O values may record a decline in ambient salinity rather than seasonal increase in temperature during the transportation from the spawning to the fishing grounds, or an ontogenetic shift in the pH of the endolymph. Sea surface salinity in Toyama Bay was drastically decreased along the southern shore compared with elsewhere in the bay, whereas the sea surface temperature distribution was rather uniform. Considering that the main sardine and anchovy spawning ground is in the western part of Toyama Bay and that a counterclockwise current usually prevails in the bay, the salinity change associated with the transport of larvae from the spawning ground to the sampling site may explain the otolith δ18O change. The δ13C and δ18O values recorded in otoliths of two species are inconsistent with the observed temperatures, but this may be due to unmeasured variability of δ13C (dissolved inorganic carbon, DIC) and δ18O (H2O) in seawater and/or physiological effects on the calcification process.