Comment on "Metabolic scaling is the product of life-history optimization".

White et al. (Science 377, p. 834-839, 2022) propose that reproduction reduces the somatic growth of animals. This contradicts the common observations that non-reproducing adults are not larger than those that reproduced as well as the very example the authors provide of a fish that reproduces while its growth continues to accelerate, which is common in larger fish.

Response to Comments on "Metabolic scaling is the product of life-history optimization".

Froese and Pauly argue that our model is contradicted by the observation that fish reproduce before their growth rate decreases. Kearney and Jusup show that our model incompletely describes growth and reproduction for some species. Here we discuss the costs of reproduction, the relationship between reproduction and growth, and propose tests of models based on optimality and constraint.

Influence of garlic extract on larval performance and survival of juvenile angelfish Pterophyllum scalare during transport / Influência do extrato de alho no desempenho larval e na sobrevivência durante o transporte de juvenis de acará bandeira Pterophyllum scalare

The objective of this study was to evaluate the properties of garlic as a growth promoter in larvae of angelfish Pterophyllum scalare and its benefits during transport of juveniles of this species. The experiment was conducted in recirculation aquaculture system, consisting of 20 tanks of 40 L equipped with independent water input and output. We used 1,400 larvae distributed among five treatments, with four repetitions, which totaled 20 experimental units. The treatments were 0, 50, 100, 200, and 400 mg of garlic extract per kilo of feed. The results showed that the inclusion of levels of garlic extract in the feed did not significantly effect the fish’s development or their transport. Neither did the inclusion of levels of garlic extract affect the survival of the larvae during the trial period. New research with extracts of higher dosages should be performed to elucidate the effect of garlic extract as a growth promoter.

O estudo teve como objetivo avaliar as propriedades do alho como promotor de crescimento em larvas de acará bandeira Pterophyllum scalare e seus benefícios no transporte de juvenis da mesma espécie. O experimento foi conduzido em sistema de recirculação composto por 20 aquários de 40 L de volume útil, dotado de entrada e saída de água independentes e teve a duração de 40 dias. O delineamento experimental adotado foi o inteiramente casualizado (DIC), com cinco tratamentos e quatro repetições, totalizando 20 unidades experimentais. Foram utilizadas 1.400 larvas de acará bandeira (Pterophyllum scalare) divididas entre os tratamentos. Os tratamentos consistiram em: 0, 50, 100, 200 e 400 mg de extrato de alho por quilo de ração. Os resultados mostraram que não houve efeito significativo dos níveis de inclusão do extrato do alho sobre os índices zootécnicos avaliados e posteriormente no transporte dos juvenis. Também não foi observado influência na sobrevivência das larvas durante o período experimental. Novas pesquisas com dosagens maiores de extratos devem ser realizados para melhor elucidação do efeito do extrato de alho como promotor de crescimento.

Enhanced Muscle Fibers of Epinephelus coioides by Myostatin Autologous Nucleic Acid Vaccine.

Epinephelus coioides is a fish species with high economic value due to its delicious meat, high protein content, and rich fatty acid nutrition. It has become a high-economic fish in southern parts of China and some other Southeast Asian countries. In this study, the myostatin nucleic acid vaccine was constructed and used to immunize E. coioides. The results from body length and weight measurements indicated the myostatin nucleic acid vaccine promoted E. coioides growth performance by increasing muscle fiber size. The results from RT-qPCR analysis showed that myostatin nucleic acid vaccine upregulated the expression of myod, myog and p21 mRNA, downregulated the expression of smad3 and mrf4 mRNA. This preliminary study is the first report that explored the role of myostatin in E. coioides and showed positive effects of autologous nucleic acid vaccine on the muscle growth of E. coioides. Further experiments with increased numbers of animals and different doses are needed for its application to E. coiodes aquaculture production.

Genetic and Pathogenic Characterization of a New Iridovirus Isolated from Cage-Cultured Large Yellow Croaker (Larimichthys crocea) in China.

Iridoviruses are an important pathogen of ectothermic vertebrates and are considered a significant threat to aquacultural fish production. Recently, one of the most economically important marine species in China, the large yellow croaker (Larimichthys crocea), has been increasingly reported to be the victim of iridovirus disease. In this study, we isolated and identified a novel iridovirus, LYCIV-ZS-2020, from cage-cultured large yellow croaker farms in Zhoushan island, China. Genome sequencing and subsequent phylogenetic analyses showed that LYCIV-ZS-2020 belongs to the genus Megalocytivirus and is closely related to the Pompano iridoviruses isolated in the Dominican Republic. LYCIV-ZS-2020 enriched from selected tissues of naturally infected large yellow croaker was used in an artificial infection trial and the results proved its pathogenicity in large yellow croaker. This is the first systematic research on the genetic and pathogenic characterization of iridovirus in large yellow croakers, which expanded our knowledge of the iridovirus.

Effect of dietary supplementation of lauric acid on growth performance, antioxidative capacity, intestinal development and gut microbiota on black sea bream (Acanthopagrus schlegelii).

A feeding trial of eight weeks was conducted to examine the influence of food supplementation with lauric acid (LA) on Acanthopagrus schlegelii (juvenile black sea bream). A 24 percent fish meal baseline diet was created, while the other two diets were generated with dietary supplementation of graded points of LA at 0.1 percent and 0.8 percent, respectively. Each diet was given a triplicate tank with 20 fish weighing 6.22 ± 0.19 g. In comparison with the control group, the weight gain rate, growth rate, as well as feed efficiency of fish fed of 0.1 percent diet of LA were considerably (P < 0.05) greater. The total body and dorsal muscle proximate compositions did not change significantly between groups (P > 0.05). Triglyceride (TG) content was considerably (P < 0.05) greater in the LA-supplemented meals eating group in comparison with the control group. In the group eating LA-supplemented meals, the height of villus and the number of goblet cells/villus were considerably (P < 0.05) larger. The microbial makeup of the gut was also studied. The differences in phyla, class, and family level were not statistically significant (P > 0.05). Firmicutes in the phylum, Betaproteobacteri, Gammaproteobacteria, and Clostridia in the class, and Clostridiaceae in the family were all substantially increased with higher levels of LA supplementation (P < 0.05). According to the findings of this study, an LA-supplemented diet improves fish development, antioxidative capability, gut microbiota and intestinal health.

Genomic prediction of growth in a commercially, recreationally, and culturally important marine resource, the Australian snapper (Chrysophrys auratus).

Growth is one of the most important traits of an organism. For exploited species, this trait has ecological and evolutionary consequences as well as economical and conservation significance. Rapid changes in growth rate associated with anthropogenic stressors have been reported for several marine fishes, but little is known about the genetic basis of growth traits in teleosts. We used reduced genome representation data and genome-wide association approaches to identify growth-related genetic variation in the commercially, recreationally, and culturally important Australian snapper (Chrysophrys auratus, Sparidae). Based on 17,490 high-quality single-nucleotide polymorphisms and 363 individuals representing extreme growth phenotypes from 15,000 fish of the same age and reared under identical conditions in a sea pen, we identified 100 unique candidates that were annotated to 51 proteins. We documented a complex polygenic nature of growth in the species that included several loci with small effects and a few loci with larger effects. Overall heritability was high (75.7%), reflected in the high accuracy of the genomic prediction for the phenotype (small vs large). Although the single-nucleotide polymorphisms were distributed across the genome, most candidates (60%) clustered on chromosome 16, which also explains the largest proportion of heritability (16.4%). This study demonstrates that reduced genome representation single-nucleotide polymorphisms and the right bioinformatic tools provide a cost-efficient approach to identify growth-related loci and to describe genomic architectures of complex quantitative traits. Our results help to inform captive aquaculture breeding programs and are of relevance to monitor growth-related evolutionary shifts in wild populations in response to anthropogenic pressures.

A Transcriptome Insight During Early Fish Larval Development Followed by Starvation in Seriola rivoliana.

We investigated a time-course larval transcriptional analysis (RNA-seq) in the longfin yellowtail Seriola rivoliana, from hatching to day four at 22 °C, without providing zooplankton as food. Larval starvation is a critical physiological stage that must be prevented to ensure survival. However, the transcriptional mechanisms to endure starvation have not been investigated in marine fish. Differential gene expression showed newly day-specific transcriptome events during larval development. On day 1 (yolk sac absorption), the predominant upregulated developmental processes were larval growth, muscle and vision development, cytoskeletal structure, protein synthesis, protein and fat digestion-absorption, and hormone biosynthesis, whereas the cell cycle was suppressed. On day 2 (yolk sac exhaustion), a new stage of energy regeneration (ATP) was supplied by the oil drop reserve, whereas protein digestion-absorption and growth were suppressed. On day 3 (mouth opening and starvation), stress signals and nutrition deprivation upregulated the p53 signal and triggered autophagy and the AMP-activated protein kinase (AMPK) pathways as an alternative catabolic pathway to enduring starvation, and the circadian rhythm was established. On day 4 (starving and weakened larvae condition), autophagy supported subsequent protein synthesis, activated the immune system, and promoted estrogen signaling and skeleton renovation. However, larvae suppressed muscle development, vision and carbohydrate, and fat digestion-absorption and became lethargic, evidencing limited physiological support by autophagy to maintain survival without exogenous nutrition in this species.

Molecular characterization of fshb and lhb subunits and their expression profiles in captive white-edged rockfish, Sebastes taczanowskii.

Fundamental knowledge on the regulation of reproduction by gonadotropins (Gths) is quite limited in viviparous fishes. In the present study, we performed molecular cloning and characterization of cDNAs encoding two Gth subunits (fshb and lhb) from the pituitaries of viviparous white-edged rockfish, Sebastes taczanowskii; expression profiles of both gene transcripts were elucidated in the pituitaries of reproductive males and females which were kept in a captive environment. The cloned fshb and lhb fragments exhibited high sequence identities with corresponding ß-subunit sequences from black rockfish, S. schlegelii. Notably, the fshb of white-edged rockfish appeared to lack a putative N-glycosylation site, whereas lhb conserved it. Expression of fshb and lhb transcripts in the rockfish pituitaries largely changed in synchrony but for minor exceptions. In males, levels of both transcripts increased with progression of spermatogenesis, although the peak for fshb (October) appeared slightly earlier than that for lhb (November). In females, both gene transcripts exhibited synchronous bimodal changes. High expression of fshb and lhb transcripts in the female pituitary during the gestation period, followed by the drastic decrease at parturition, suggest their possible involvement in regulation of gestation of this species. The knowledge gained for Sebastes in this study superimposes fundamental information necessary for further physiological understanding of viviparity in teleost fish.

Maternal diet affects utilization of endogenous lipids by red drum Sciaenops ocellatus embryos and early larvae.

Embryonic and early larval development and metabolism of most teleost fishes are fueled entirely by maternally derived nutritional resources (yolk and oil) before the onset of exogenous feeding. The composition of those resources depends, in part, on maternal diet. To examine how diet-induced variations in egg composition affect embryonic and larval utilization of endogenous lipids and fatty acids, we fed red drum (Sciaenops ocellatus) broodstock four different diets to produce distinctive fatty acid compositions in eggs but with no significant difference in total lipid content. We sampled embryos and unfed larvae every 12 h from 12 h post-fertilization (hpf) until starvation (96-120 hpf; n = 5 spawns per diet group). Rates of utilization of the oil globule were significantly different among diet groups, resulting in significant differences in mean oil globule size at the first feeding stage (84 hpf). Utilization rates for 15 fatty acids were significantly different among diet groups and were proportional to their initial concentration. As a result, differences in larval fatty acid compositions among maternal diet groups diminished over time but remained different even at later stages. In addition, larval standard length at 84 hpf was positively correlated with egg total lipid content. This study suggests that the fatty acid composition of yolk and oil affects energy metabolism and tissue composition in red drum larvae. These effects could have consequences for the survival and essential physiological functions of fish larvae during the critical period of transition to exogenous feeding.

Effects of Ocean Acidification on Transcriptomes in Asian Seabass Juveniles.

Ocean acidification is changing the fate of marine organisms. It is essential to predict the biological responses and evolutionary processes driven by ocean acidification, to maintain the equilibrium of the marine ecosystem and to facilitate aquaculture. However, how marine organisms, particularly the marine fish species, respond to ocean acidification, is still poorly understood. Consequences of ocean acidification on finfish aquaculture are largely not well known. We studied the effects of ocean acidification for 7 days on growth, behaviour and gene expression profiles in the brain, gill and kidney of Asian seabass juveniles. Results showed that growth and behaviour were not affected by short-term ocean acidification. We found tissue-specific differentially expressed genes (DEGs) involving many molecular processes, such as organ development, growth, muscle development, ion homeostasis and neurogenesis and development, as well as behaviours. Most of the DEGs, which were functionally enriched in ion homeostasis, were related to calcium transport, followed by sodium/potassium channels. We found that genes associated with neurogenesis and development were significantly enriched, implying that ocean acidification has also adversely affected the neural regulatory mechanism. Our results indicate that although the short-term ocean acidification does not cause obvious phenotypic and behavioural changes, it causes substantial changes of gene expressions in all three analysed tissues. All these changes of gene expressions may eventually affect physiological fitness. The DEGs identified here should be further investigated to discover DNA markers associated with adaptability to ocean acidification to improve fish's capability to adapt to ocean acidification.

Optimum protein requirement of juvenile orange-spotted grouper (Epinephelus coioides).

The purpose of subject was to explore the optimum protein requirement of juvenile grouper (Epinephelus coioides). In the test, 450 juveniles with an average weight (10.02 ± 0.22) g were randomly divided into six groups with triplicate, and were fed with 350, 400, 450, 500, 550 and 600 g/kg iso-lipid test diet twice 1 day for 8 weeks, respectively. The results showed that: (1) With the increase of protein level, the body weight gain rate and specific growth rate first increased and then reduced, while the feed coefficient rate first decreased and then increased, while the protein efficiency significantly decreased (P < 0.05). (2) With the increase of protein level, the condition factor, hepaticsomatic index and visceralsomatic index significantly reduced (P < 0.05). (3) With the increase of protein level, the crude protein content of whole fish and muscle gradually increased, while the crude lipid content gradually decreased. (4) High-protein diet (550-600 g/kg) significantly increased the plasma total protein content and decreased the triglyceride content of orange-spotted grouper (P < 0.05). (5) Compared with the 350 g/kg group, 500, 550, 600 g/kg groups significantly increased the activities of glutamic-pyruvic transaminase and glutamic oxaloacetic transaminase in liver (P < 0.05). (6) With the increase of protein level, the protease activity of intestine first increased and then decreased, and reached the maximum at the protein level of 500 g/kg, while lipase and amylase decreased significantly (P < 0.05). (7) The activities of acid phosphatase, superoxide dismutase and lysozyme in liver increased first and then decreased with the increase of protein level, and reached the maximum in the 400 g/kg protein group. According to the analysis specific growth rate, the optimum protein level of juvenile orange-spotted grouper is 521.84 g/kg.

Gonadal lipidomics profile of an ovoviviparity teleost, black rockfish, during gonadal development.

In order to study the variation of gonad lipidomics during reproductive cycle, black rockfish was employed as the research model in the present study. Using histology, lipidomics, and qPCR, the profile of gonad lipidomics and the expression levels of related genes during different developmental stages were detected and analyzed to show the potential regulatory network of lipid metabolism. Based on Ultra High-Performance Liquid Tandem Chromatography Quadrupole Time of Flight Mass Spectrometry (UHPLC-QTOFMS), four significant differential glycerophospholipid metabolic pathways including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), and phosphatidic acid (PA) were enriched by KEGG. Pathway-related enzyme-coding genes, including phosphatidylserine decarboxylase (pisd), phosphatidylserine synthase (ptdss1, ptdss2), and phospholipase D (pld1, pld2) were identified from the whole genome data and confirmed by cloning. The expression profiles of these genes were tested by qPCR in the tissues and gonads in developmental stages, and we found that pisd, pld, and ptdss genes were all downregulated through the developmental process in the brain of male, and the latter two genes were upregulated in the liver and testis at stage IV, which were the opposite trend observed in the female. Thus, our findings would be helpful in further understanding the substance metabolism and regulation during gonad development in ovoviviparity teleosts.

Finding Nemo's clock reveals switch from nocturnal to diurnal activity.

Timing mechanisms play a key role in the biology of coral reef fish. Typically, fish larvae leave their reef after hatching, stay for a period in the open ocean before returning to the reef for settlement. During this dispersal, larvae use a time-compensated sun compass for orientation. However, the timing of settlement and how coral reef fish keep track of time via endogenous timing mechanisms is poorly understood. Here, we have studied the behavioural and genetic basis of diel rhythms in the clown anemonefish Amphiprion ocellaris. We document a behavioural shift from nocturnal larvae to diurnal adults, while juveniles show an intermediate pattern of activity which potentially indicates flexibility in the timing of settlement on a host anemone. qRTPCR analysis of six core circadian clock genes (bmal1, clocka, cry1b, per1b, per2, per3) reveals rhythmic gene expression patterns that are comparable in larvae and juveniles, and so do not reflect the corresponding activity changes. By establishing an embryonic cell line, we demonstrate that clown anemonefish possess an endogenous clock with similar properties to that of the zebrafish circadian clock. Furthermore, our study provides a first basis to study the multi-layered interaction of clocks from fish, anemones and their zooxanthellae endosymbionts.

Early Life Intervention Using Probiotic Clostridium butyricum Improves Intestinal Development, Immune Response, and Gut Microbiota in Large Yellow Croaker (Larimichthys crocea) Larvae.

Marine fish larvae are vulnerable during the early life period. The early intervention using probiotics may be a promising method to improve growth of fish larvae. In this study, a 30-day feeding trial was conducted to evaluate the effects of early life intervention using probiotic Clostridium butyricum (CB) on growth performance, intestinal development, immune response and gut microbiota of large yellow croaker (Larimichthys crocea) larvae. Four isonitrogenous and isolipidic diets were formulated with the supplementation of four different levels of CB (5 × 109 CFU g-1), 0.00% (Control), 0.10% (CB1), 0.20% (CB2), and 0.40% (CB3). Results showed that larvae fed diets with CB had significant higher final length than the control group. Meanwhile, larvae fed the diet with 0.10% CB had significant higher final weight and specific growth rate (SGR) than the control group. However, no significant difference in survival rate was observed among dietary treatments. CB supplementation significantly increased the height of intestinal villus and the length of intestinal enterocyte. Similarly, CB supplementation significantly increased the expression of tight zonula occludens-2 (zo-2) and ornithine decarboxylase (odc) than the control group. Larvae fed the diet with 0.20% CB had significant higher lipase and leucine-aminopeptidase (LAP) activity than the control group. Moreover, CB supplementation significantly improved immune enzyme activities than the control group. Sequencing of bacterial 16S rRNA V4-5 region indicated that dietary CB altered intestinal microbiota profile and decreased intestinal microbial diversities of larvae. CB supplementation could effectively increase the abundance of CB, and decrease the abundance of some potential pathogenic bacteria in larval gut. These results revealed that early life intervention using 0.10-0.20% CB could promote growth of large yellow croaker larvae probably through promoting intestinal development, improving immune enzyme activities and modulating gut microbiota.

The effects of acute temperature change and digestive status on in situ cardiac function in mahi-mahi (Coryphaena hippurus).

In this study, we investigated the effect of acute increases in temperature on cardiovascular function of mahi-mahi (Coryphaena hippurus). We also describe, for the first time, an artery that supplies the gastrointestinal tract that originates from the fourth branchial artery. We used vascular casting to verify the anatomical location of this unique celiaco-mesenteric artery. We predicted that blood flow in this vessel would be correlated with the digestive state of the animal. Increasing water temperature from 25.0 to 30.5 °C resulted in a linear increase in heart rate (fH) from 165 ± 4 beats∙min-1to 232 ± 7 beats∙min-1. Over this temperature range, fH strongly correlated with water temperature (R2 = 0.79). At 31 °C fH no longer correlated with water temperature, and at 34 °C fH had dropped to 114 ± 19 beats∙min-1. Furthermore, we found that mahi are capable of maintaining constant cardiac output over a temperature range from 25 to 31 °C. Cardiac function appeared to be compromised at temperatures >31 °C. In fed anesthetized fish, blood flow was pulsatile in the celiaco-mesenteric artery and was not in fasted fish. In fed fish, blood flow in the left celiaco-mesenteric artery was 1.99 ± 0.78 ml·min-1·kg-1 compared to the total cardiac output of 168.6 ± 12.7 ml·min-1·kg-1. The data suggest that mahi can differentially regulate gastric blood flow based on feeding state, which may explain the high digestive efficiency and very high growth rates of these pelagic predators.

Insights into early ontogenesis: characterization of stress and development key genes of pikeperch (Sander lucioperca) in vivo and in vitro.

There are still numerous difficulties in the successful farming of pikeperch in the anthropogenic environment of various aquaculture systems, especially during early developmental steps in the hatchery. To investigate the physiological processes involved on the molecular level, we determined the basal expression patterns of 21 genes involved in stress and immune responses and early ontogenesis of pikeperch between 0 and 175 days post hatch (dph). Their transcription patterns most likely reflect the challenges of growth and feed conversion. The gene coding for apolipoprotein A (APOE) was strongly expressed at 0 dph, indicating its importance for yolk sac utilization. Genes encoding bone morphogenetic proteins 4 and 7 (BMP4, BMP7), creatine kinase M (CKM), and SRY-box transcription factor 9 (SOX9) were highly abundant during the peak phases of morphological changes and acclimatization processes at 4-18 dph. The high expression of genes coding for peroxisome proliferator-activated receptors alpha and delta (PPARA, PPARD) at 121 and 175 dph, respectively, suggests their importance during this strong growth phase of juvenile stages. As an alternative experimental model to replace further in vivo investigations of ontogenetically important processes, we initiated the first approach towards a long-lasting primary cell culture from whole pikeperch embryos. The present study provides a set of possible biomarkers to support the monitoring of pikeperch farming and provides a first basis for the establishment of a suitable cell model of this emerging aquaculture species.

Assessment of a small-scale fishery: Lane Snapper (Lutjanus synagris) using a length metric method.

Small-scale fisheries are hard to assess because of the limited availability of data. Therefore, a method requiring easy-to-obtain catch-data is important for the assessment and management of small-scale fisheries. The objective of this study was to assess the effect of fishing gear selectivity on a length-based metric method proposed by Froese by estimating three indicators using catch-data from Lane Snapper (Lutjanus synagris) collected in Honduras. These indicators are (1) the percentage of mature individuals in the catch, (2) the percentage of fish within the range of estimated optimal lengths to be captured, and (3) the percentage of fish larger than the optimal length. These indicators determine the level of overfishing. The indicators were estimated separately for catch-data corresponding to gill nets, and each indicator was estimated with and without selectivity correction. Selectivity and mesh sizes of the fishing gear had a major impact on the estimation of indicators 1 and 2. As for indicator 3, it consistently showed a high level of exploitation. The three estimated indicators suggested that the Lane Snapper fishery in Honduras is experiencing overfishing. Overall, the method appears to be promising for the assessment of small-scale fisheries, but it should be used cautiously.

Faster juvenile growth promotes earlier sex change in a protandrous hermaphrodite (barramundi Lates calcarifer).

The relationship between growth and sexual maturation is central to understanding the dynamics of animal populations which exhibit indeterminate growth. In sequential hermaphrodites, which undergo post-maturation sex change, the size and age at which sex change occurs directly affects reproductive output and hence population productivity. However, these traits are often labile, and may be strongly influenced by heterogenous growth and mortality rates. We analysed otolith microstructure of a protandrous (i.e., male-to-female) fish (barramundi Lates calcarifer) to examine growth in relation to individual variation in the timing of sex change. Growth trajectories of individuals with contrasting life histories were examined to elucidate the direction and extent to which growth rate influences the size and age individuals change sex. Then, the relationships between growth rate, maturation schedules and asymptotic maximum size were explored to identify potential trade-offs between age at female maturity and growth potential. Rapid growth was strongly associated with decreased age at sex change, but this was not accompanied by a decrease in size at sex change. Individuals that were caught as large females grew faster than those caught as males, suggesting that fast-growing individuals ultimately obtain higher fitness and therefore make a disproportionate contribution to population fecundity. These results indicate that individual-level variation in maturation schedules is not reflective of trade-offs between growth and reproduction. Rather, we suggest that conditions experienced during the juvenile phase are likely to be a key determinant of post-maturation fitness. These findings highlight the vulnerability of sex-changing species to future environmental change and harvest.

Morphological and biochemical effects of food deprivation during the early development of Pacific red snapper Lutjanus peru.

We report the effects of food deprivation on the early development of Pacific red snapper Lutjanus peru during the first days of development. The point of no return (PNR) was determined using the feeding incidence after a delay in first feeding. The gradual deterioration of the larvae during food deprivation was recorded using morphometric, histological, enzymatic and biochemical analysis. The time to reach the PNR was 120 h after hatching. Morphologically, the total length, muscle height, head length, tail length and pectoral angle showed the biggest reductions and their growth coefficients changed significantly during food deprivation. Histologically, enterocyte height also was reduced significantly. The protein concentration and activities of the digestive enzymes trypsin, cathepsin-like and lipase showed a significant decrease; meanwhile, amylase activity remained constant during food deprivation. The concentration of total essential free amino acids (EFAAs) decreased significantly while that of the nonessential free amino acids (NEFAAs) remain stable during food deprivation. The most abundant EFAAs were lysine, leucine, isoleucine and valine; the most abundant NEFAAs were alanine, glycine and glutamate, suggesting a more prominent role as energy substrates. At the time of the PNR the concentration of almost all the free amino acids showed a significant decrease. Early food deprivation has a significant impact on the morphology and biochemical characteristics of L. peru. These results suggest that initial feeding of L. peru should begin within 3 days of yolk sac depletion to avoid the PNR. Further studies are necessary to confirm and validate the characters identified in this study as biomarkers of starvation under culture conditions and evaluate their possible utility in ichthyoplankton surveys.