Larval Japanese Anchovy Engraulis Japonicus Research Articles

Relationships between the daily growth rate of Japanese anchovy Engraulis japonicus larvae and environmental factors in Osaka Bay, Seto Inland Sea, Japan

Seasonal changes in the growth rate of larval Japanese anchovy Engraulis japonicus collected by shirasu seine net boats in Osaka Bay in 2008 were estimated using otolith daily growth increments to examine the effects of environmental factors. Larval anchovy were caught from May to November. The range in standard length (SL) of the larval anchovy was 10–35 mm, and larvae of SL 20–25 mm dominated numerically, accounting for more than 40% of all anchovy larvae. Daily growth rates for the last five days before catch increased from May to July, decreased or were stagnant in August and September, increased again in October, and decreased in November. Seawater temperature and density of copepod nauplii were correlated with the daily growth rate. In this study, the relationship between growth rate and temperature showed a skewed dome shape, with an optimum temperature for growth of around 23 °C. These results in summer of 2008 suggest that the growth rate of Japanese anchovy increased with increasing temperature for temperatures < 23 °C, but growth was limited by prey availability and/or other factors, such as low dissolved oxygen, at higher temperatures. Recent environmental improvements in nutrient inputs to Osaka Bay are discussed in relation to larval growth rate.

Diet of late larval Japanese anchovy Engraulis japonicus in the Kii Channel, Japan

The diet of late larval (standard length 17.0–24.9 mm) Japanese anchovy Engraulis japonicus collected from the Kii Channel between April 2007 and March 2008 was analyzed. The main prey items found in the gut were copepods, and the composition of the gut contents changed on a monthly basis. The most important prey items were Calanoida (unidentified) from June to August and in October–November, Oncaea in March, April, and September, and Oithona in December and January. The prey selectivity analysis demonstrated that the selectivity for a particular prey category was not consistent throughout the months. It was considered that late larval anchovy may actually have no preference for a particular prey category. The major size (body width) of the prey items consumed fell within the range of 0.10–0.40 mm throughout almost the whole year. Late larvae tended to select relatively larger prey items from the environment. The relationship between the seasonal variabilities in diet and the fishery catch of anchovy “shirasu” (larvae of anchovy) is also discussed.

Effects of temperature, food availability, and body size on daily growth rate of Japanese anchovy Engraulis japonicus larvae in Hiuchi-nada

With data sampled from 2003 to 2006, this study presents the effects of temperature, food availability (C), and body size on the somatic growth rate \( \hat{g} \) (mm day−1) and on the size-specific growth rates \( \hat{G} \) (day−1) of larval Japanese anchovy Engraulis japonicus caught in Hiuchi-nada, Seto Inland Sea, Japan, a semi-enclosed narrow sea. C was calculated using an individual-based model, which is an encounter model between copepods and anchovy where the anchovy resulted in a successful capture of the copepod. \( \hat{g} \) decreased with increasing anchovy length, but increased with increasing C. No significant relationship was found between \( \hat{g} \) and temperature. \( \hat{G} \) decreased with increasing temperature, but anchovy weight, on the other hand, increased with increasing C. In the literature, the mechanism of growth determination for larvae of pelagic fish species is considered to be primarily determined by sea temperature and secondarily by food availability. However, \( \hat{g} \) and \( \hat{G} \) were found to be dependent on C rather than temperature. \( \hat{G} \) was dependent on anchovy weight rather than C and temperature. For forecasting the number of days required for development from an arbitrary pre-recruitment size to the recruitment size, we address not only temperature but also food availability and the size effect when considering the mechanism of growth determination for larvae.

Seasonal variability in growth of larval Japanese anchovy Engraulis japonicus driven by fluctuations in sea temperature in the Kii Channel, Japan

Seasonal variability in the growth of larval Japanese anchovy Engraulis japonicus was examined through otolith microstructure analysis based on the samples collected from the northern side (inner area, IA) and the southern side (outer area, OA) of the Kii Channel from April 2006 to March 2007. Growth trajectories (otolith backcalculated mean standard length of 5 day intervals from 5 days after hatch to 24 days) as well as the most recent 5 day mean growth rate of larvae before capture (G(5)) differed among months. Growth trajectories showed the same pattern as G(5). In IA, mean +/-s.d.G(5) ranged from 0.31 +/- 0.04 mm day(-1) (January) to 0.73 +/- 0.06 mm day(-1) (October). In OA, mean +/-s.d.G(5) ranged from 0.36 +/- 0.05 mm day(-1) (January) to 0.79 +/- 0.11 mm day(-1) (August). G(5) values declined from November to January and then started to increase. In general, the seasonal patterns of growth were similar between IA and OA, and a clear seasonal pattern in growth was identified. When the relationships among larval growth rate, sea temperature, zooplankton density and larval density were examined, growth rate was positively related with sea temperature in both areas and not related with the other factors. The similar pattern in growth observed between IA and OA was probably due to the low spatial variability in sea temperature compared to its seasonal variability.

Predator-specific growth-selective predation on larval Japanese anchovy Engraulis japonicus

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 350:99-107 (2007) - DOI: https://doi.org/10.3354/meps07158 Predator-specific growth-selective predation on larval Japanese anchovy Engraulis japonicus Akinori Takasuka1,*, Ichiro Aoki2, Yoshioki Oozeki1 1National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan 2Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan *Email: takasuka@affrc.go.jp ABSTRACT: Predator-specific growth-selective predation on larval Japanese anchovy Engraulis japonicus was demonstrated by comparing growth rates between the larvae ingested by predators and the larvae from the corresponding original populations through otolith microstructure analysis, based on original data and reanalyzed data from previous studies. Ingested larvae from the stomachs of small pelagic predators (juvenile Japanese anchovy, round herring Etrumeus teres, jack mackerel Trachurus japonicus and white croaker Pennahia argentatus) had significantly lower growth rates than the larvae from the original populations in general. For large piscivorous predators (sea bass Lateolabrax japonicus, greater amberjack Seriola dumerili and skipjack tuna Katsuwonus pelamis), no measurable differences in the growth rates were observed between ingested larvae and larvae from the original populations. Small pelagic fish were therefore identified as growth-selective predators, whereas large piscivorous fish were identified as non-growth-selective predators. Exponential declines in the relative predation mortalities of larvae with higher growth rates suggest the potential for growth rate to exert a great effect on recruitment variability. However, the predator field would regulate selection for growth characteristics of survivors. KEY WORDS: Growth-selective predation hypothesis · Growth rate · Otolith · Early life stage · Japanese anchovy · Relative predation mortality · Optimal foraging theory Full text in pdf format PreviousNextCite this article as: Takasuka A, Aoki I, Oozeki Y (2007) Predator-specific growth-selective predation on larval Japanese anchovy Engraulis japonicus. Mar Ecol Prog Ser 350:99-107. https://doi.org/10.3354/meps07158Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 350. Online publication date: November 22, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Carbon source and trophic position of pelagic fish in coastal waters of south-eastern Izu Peninsula, Japan, identified by stable isotope analysis

It is important to clarify trophic dynamics in marine ecosystems for management of the fishing ground. Organic carbon sources and trophic position of pelagic fishes in the coastal waters of the south-eastern Izu Peninsula, Japan, were examined on the basis of carbon and nitrogen stable isotope distributions. The δ13C of the fishes was mostly distributed from −19 to −16‰ for nektonic fishes (13 species of adults and immatures) and planktonic fishes (10 species of larvae and juveniles), close to the δ13C values of particulate organic matter and planktonic decapods. These δ13C signatures for the inhabitants of the water column were in contrast with the high δ13C values (mainly −16 to −13‰) for demersal fishes of Scorpaeniformes and benthic polychaetes collected in the surf zone. These results indicate that nektonic and planktonic fishes depend on phytoplankton for carbon supply. The δ15N signatures suggest that the trophic position ranged 3.1–4.5 for the nektonic fishes and 2.9–3.7 for the planktonic fishes, premised on trophic level 3 for larval Japanese anchovy Engraulis japonicus. Thus, planktivorous fishes should be mainly assigned to trophic levels 3 and 4 in this area.

Environmental determinants of growth rates for larval Japanese anchovy Engraulis japonicus in different waters

AbstractDo disparate mechanisms determine growth rates of fish larvae in the different regions? The relationship between growth rates and environmental factors (sea temperature and food availability) was examined for larval Japanese anchovy Engraulis japonicus in geographically and environmentally different waters, through sagittal otolith microstructure analysis. Recent 3‐day mean growth rates directly before capture were positively related with sea‐surface temperature (SST) but not with food availability (plankton density) for the larvae in the Kuroshio Extension and Kuroshio–Oyashio transition regions of the western North Pacific. On the contrary, variations in recent growth rates were attributed to food availability (plankton density) as well as SST for the larvae in the East China Sea. In the shirasu fishing ground in Sagami Bay, larval growth rates were variable under the influences of both SST and food availability (feeding incidence). On the surface, the growth–environment relationships seemed to differ among regions. However, a definite general pattern of the dome‐shaped relationship between recent growth rates and SST was observed when all the regions were combined. Growth rates were similar even among clearly different regions if at the same SST. Overall, growth rates roughly increased with SST until they reached the maximum at SST of 21–22°C (i.e. optimal growth temperature), and declined when SST went over 21–22°C. On the contrary, no clear relationship was observed between growth rate and plankton density or between SST and plankton density. Therefore, the apparent among‐region differences would be firstly caused by the differences in regional SST range. The systematic mechanism of growth determination for widespread pelagic fish species larvae would be run by primarily sea temperature and secondarily food availability, at the species level.

Three synergistic growth-related mechanisms in the short-term survival of larval Japanese anchovy Engraulis japonicus in Sagami Bay

The 'growth-mortality' hypothesis, which holds that larger and/or faster growing individuals will have a higher probability of survival, currently includes 3 functional mechanisms (hypotheses) in its theoretical framework: 'bigger is better', 'stage duration' and the recently proposed 'growth-selective predation', which are based on size, time and per se growth rate, respec- tively. Through otolith microstructure analysis, we tested these 3 synergistic growth-related mecha- nisms according to growth characteristics of the survivors vs the original population in the short-term (ca. 2 wk) survival process of larval Japanese anchovy Engraulis japonicus in the 'shirasu' (larval anchovy) fishing ground in Sagami Bay, Japan. Back-calculated standard length (growth trajectory) and growth rate (growth history) were compared between the survivors (SV) captured on 18 July 2001 and the presumed original population (OP) captured on 1 and 5 July 2001. The larvae from SV were consistently smaller than the larvae from OP until at least the start of the ca. 2 wk survival pro- cess (1 July). Daily growth rates, however, were higher for SV than for OP at least at the start of the survival period. Therefore, faster growing individuals survived even if they were smaller than slower- growing conspecifics. This was probably mediated by predation. Growth histories were generally similar between the metamorphosing larvae and non-metamorphosing larvae older than 40 d, the minimum age for metamorphosis, except for the period immediately after hatching. As such, we failed to detect a clear relationship between growth rates and the timing of metamorphosis (stage duration) as a whole. The results supported and extended the 'growth-selective predation' hypothe- sis but not the 'bigger is better' hypothesis. The 'stage duration' hypothesis was not unequivocally supported by the present findings.

Growth-selective predation hypothesis revisited for larval anchovy in offshore waters: cannibalism by juveniles versus predation by skipjack tunas

The 'growth-selective predation' hypothesis was revisited for larval Japanese anchovy Engraulis japonicus, focusing on larval cannibalism by juveniles and larval predation by skipjack tunas Katsuwonus pelamis, in offshore waters. Larval anchovy and predators were captured simulta- neously in June 1997 and in May 2000 in the western North Pacific. Growth rates estimated through otolith microstructure analysis, as well as somatic sizes, were compared between the ingested larvae from the stomach contents of the predators and the surviving larvae from the original population. Size-selective mortality was directed negatively for cannibalism by juveniles and positively for pre- dation by skipjack tunas. The cannibalised larvae had lower growth rates than the larvae from the original population in the same larval size range. On the other hand, a similar comparison showed no differences in larval growth rates for predation by skipjack tunas. Larval cannibalism by juveniles would potentially regulate growth-selective survival as well as survival rate itself during early life history stages of Japanese anchovy, while predation by skipjack tunas would influence survival rate itself but not growth-selective survival.

Evidence of growth-selective predation on larval Japanese anchovy Engraulis japonicus in Sagami Bay

Growth-selective predation mortality was demonstrated for postlarval Japanese anchovy Engraulis japonicus in field research. The larval anchovy and their predatory fish were simultaneously captured by a trawl in Sagami Bay during October to November 2000. The growth rates analyzed by otolith microstructure were compared between the larvae from the stomach con- tents of the predators (prey larvae) and those from the population of origin (surviving larvae). The mean growth rates of the prey larvae collected on 28 October and 2 to 4 November (mean ± SD: 0.57 ± 0.07 mm d -1 ) and on 23 November (0.50 ± 0.06 mm d -1 ) were significantly lower than those of the corresponding surviving larvae (0.63 ± 0.07 and 0.54 ± 0.06 mm d -1 , respectively). Such significant differences were not explained by size-selective predation, but were due to variations in the mean growth rates at the same larval size (i.e. non-size-related). The mean growth rates of the prey larvae were different among predatory species (barracuda Sphyraena pinguis, Japanese sea bass Lateo- labrax japonicus, white croaker Pennahia argentatus, Japanese jack mackerel Trachurus japonicus, Pacific round herring Etrumeus teres and juvenile anchovy). Comparisons of back-calculated daily growth rates showed that the decrease in growth rates of the prey larvae were consistent from directly after hatching up to predation. The larvae with lower growth rates were more vulnerable to predation, owing to the cumulative decline in growth rates from hatching to each encounter with predators, compared to the larvae with higher growth rates, even if they were the same size, at a given moment in the sea. Therefore, the level of growth rates itself had direct impact on vulnerabil- ity to predation for larval anchovy, independently of both size (size-selective mortality) and time (stage duration). In addition, such impacts could be predator specific. We propose the 'growth-selec- tive predation' hypothesis (mechanism), which is theoretically independent of and synergistic with the existing hypotheses based on size and time under the general 'growth-mortality' concept for the survival process during the early life history of marine pelagic fish.