Tomoki Honryo

• Researcher at Kindai University

During the fingerling production process of Pacific bluefin tuna (PBF), Thunnus orientalis , heavy mortality can occur immediately after the transportation of juveniles from nursery tanks to sea cages and the nighttime lighting moderates this mortality. It has been confirmed that various wild live prey gathered under nighttime lighting in practical...

Seriola species are an important target fish for the aquaculture industry, and innovative techniques for their rearing have been developed in recent years. In Experiment 1 of this work, the growth of S. dumerili larvae (with and without a swim bladder) and diurnal changes in relative swim bladder volume were compared to elucidate the significance o...

Changes in nutritional constituents and enzyme activities were clarified in yellowfin tuna (YFT, Thunnus albacares) eggs during embryonic development, from eggs immediately after fertilization to hatching. The protein levels in the eggs gradually increased with development until the completion of hatching. In contrast, the triglyceride (TG) and fre...

White trevally Pseudocaranx dentex is a high-value carangid fish species that is only cultured in Japan under full lifecycle aquaculture conditions. To make the reproductive process successful and efficient, sexual phenotyping of broodstock is essential, and this has conventionally been practiced via examination upon abdominal compression. However,...

Swim bladder dysplasia is closely related with larval mass mortality due to sinking syndrome and juvenile vertebral malformations in many cultured fishes. This study revealed the appropriate environmental condition for initial swim bladder inflation (ISI) of transiently physostomous Seriola quinqueradiata and the ontogenetic and day–night change of...

Here, characteristics of marine litter ingested by Pacific bluefin tuna (PBF, Thunnus orientalis) juveniles under captive conditions were investigated. Swimming speeds of PBF juveniles with pseud-ingested polystyrene chips were compared, and mortality due to polystyrene chip ingestion in cultured teleosts (red sea bream, greater amberjack, and whit...

Three experiments were conducted to elucidate the most suitable rearing light intensity during the ontogenetic changes in white trevally (Pseudocaranx dentex) larvae. In Experiment 1, larvae were reared under 1000, 3000 or 9000 lx. At 10 days post hatching (dph), larval growth was significantly higher in the 1000 lx treatment than in the other trea...

High levels of mortality occur in the fingerling production of juvenile Pacific bluefin tuna (PBF, Thunnus orientalis), especially just after transportation from land‐based tanks to sea cages. The survival rate drastically declines within 3 days after transportation. To improve aquaculture efficiency, this problem needs to be resolved. We focused o...

In this study, we aimed to clarify the mechanism of sinking death during the larval stage of Pacific Bluefin tuna Thunnus orientalis by investigating the effects of swimming performance on sinking death, using a behavioral approach. Swimming performance was examined 3–9 days after hatching (DAH) under day and night light conditions in cuboid experi...

Some fish blood flukes of the genus Cardicola (Aporocotylidae) are considered important pathogens of farmed/ranched tuna, Thunnus spp. Infections with Cardicola spp. might obstruct the blood flow in the gills via massive accumulations of eggs and often lead to mass mortalities in captive tuna. At present, oral administration of an anthelminthic dru...

The high mortality rates of Pacific bluefin tuna (PBF; Thunnus orientalis) juveniles due to collision death can be alleviated by night-time lighting both in land-based tanks and sea cages; however, the optimal night-time lighting intensity and area of illumination for sea cages have not been systematically investigated. We addressed these issues in...

High levels of mortality occur in large net‐cage culture of Pacific bluefin tuna (PBF) Thunnus orientalis due to poor growth on commencement of sea‐cage culture obstructing the mass production of fingerlings. Therefore, we carried out this study to develop a countermeasure by using small sea cages (square with 13‐m sides). PBF juveniles were direct...

Jaw malformations are a serious problem in fingerlings of the greater amberjack, Seriola dumerili. To establish a countermeasure against these malformations, we conducted a larval behavioural test to identify their root cause, and we investigated the ability of low‐brightness rearing tank walls to control their occurrence. Larval distribution was e...

We conducted a chemical analysis of the blood of juvenile Pacific bluefin tuna (PBF; Thunnus orientalis) showing abnormal swimming (AS) behavior, such as irregular and/or frantic patterns, and compared them to normally-swimming (NS) fish in order to elucidate causes of death in aquaculture-reared tuna. This study found three abnormal characteristic...

RNA, DNA, and protein contents were assessed to evaluate somatic growth in larval and juvenile yellowfin tuna (YFT), Thunnus albacares. The experimental fish were reared at the Achotines Laboratory of the Inter-American Tropical Tuna Commission in Los Santos Province, Republic of Panama. Sampling was carried out from 3 to 33 days after hatching (DA...

Some vertebral anomalies in cultured fish arise from unusual environmental conditions during embryogenesis. We investigated the individual and combined teratogenic effects of short‐term hypercapnia and hypoxia on embryos of red sea bream (RSB), Pagrus major. Ten‐somite stage embryos were exposed to hypercapnia (60 and 120 mg/L dissolved carbon diox...

This study aimed to examine the effect of different water temperatures and light intensities on swim bladder inflation (SBI) and growth of red sea bream Pagrus major larvae to improve rearing techniques for this species. Two sets of experiments were conducted: different rearing temperatures were used in experiment 1 (19, 21, 23, and 25 °C), and dif...

It is important to understand the physiological stress responses in juvenile Pacific bluefin tuna (PBF), Thunnus orientalis, when transporting them from land-based tanks to sea cages, to develop countermeasures against mass mortality and enhance survival. We investigated the estimated time required to recover from transportation stress in PBF juven...

Three experiments were conducted to investigate the growth, survival, and standardized cohort biomass of Pacific bluefin tuna, Thunnus orientalis, larvae fed nutritionally enhanced prey during the first week of feeding using two commonly used, commercially available enrichment media, AlgaMac Enrich and Marine Glos. T. orientalis larvae exhibited ex...

Fish blood fluke of the genus Cardicola (Digenea: Aporocotylidae) are important pathogens in tuna aquaculture. Recent advances in marine blood fluke research have led to the elucidation of the lifecycles of 3 Cardicola spp. infecting tuna, which all utilize terebellid polychaetes as the intermediate host. In our survey, we obtained large numbers of...

Farming of Pacific bluefin tuna (PBT), Thunnus orientalis, is a rapidly growing industry in Japan. Aporocotylid blood flukes of the genus Cardicola comprising C. orientalis, C. opisthorchis and C. forsteri are parasites of economic importance for PBT farming. Recently, terebellid polychaetes have been identified as the intermediate hosts for all th...

Success of swim bladder inflation (SBI) is crucial for early survival of Pacific bluefin tuna (PBF) larvae, because it reduces larval sinking death by enhancing buoyancy. In Experiment 1, we examined the effect of photoperiod on SBI and survival in PBF larvae by comparing photoperiods of 9L: 15D (9L), 14L: 10D (14L: natural photoperiod), 19L: 5D (1...

Comparative feeding studies of yellowfin (Thunnus albacares) (YFT) and Pacific bluefin (Thunnus orientalis) (PBT) tuna larvae were conducted between 2011 and 2014 at the Inter-American Tropical Tuna Commission’s Achotines Laboratory in Panama and the Kinki University Fishery Laboratory in Japan as part of a 5-year research project of the SATREPS Pr...

Fish blood flukes (Aporocotylidae) are important pathogens of farmed finfish around the world. Among them, Cardicola spp. infecting farmed tuna are considered to be serious threats to tuna farming and have received tremendous attention. We conducted periodical samplings at a tuna farming site in Japan between January and May, 2015 to determine the...

To develop techniques for seedling production of yellowfin tuna, the behavior of primordial germ cells (PGCs) and gonadogenesis were examined at 1-30 days post hatching (dph) using morphometric analysis, histological examination, and in situ hybridization. Immediately after hatching, PGCs were located on the dorsal side of the posterior end of the...

A male-specific marker of a DNA sequence for the Pacific bluefin tuna Thunnus orientalis, Male delta 6 (Md6), was identified by comparative study of the sequences obtained by F3-cultured male and female AFLP-selective DNA amplification products, followed by high-throughput DNA sequencing. Md6 was characteristic in continuous 6-bp nucleotide deletio...

Early-stage mortality due to surface water tension-related death and due to sinking to the tank bottom was investigated for yellowfin tuna, Thunnus albacares (YFT), larvae. Different aeration rates and rearing water surface conditions were examined to evaluate the effect on larval survival, swim bladder inflation and growth. The percentage survival...

To investigate the reason for the high mortality of cultured juvenile Pacific bluefin tuna (PBT), especially during land-based culture, we examined the effect of the rate of light-intensity change during the dawn period. Juvenile PBT kept in a natural light environment (control) were compared with those exposed to an artificially slowed change in l...

This study investigated the effect of feedings taurine-enriched rotifers on the growth and development of larval red sea bream (RSB). Rotifers incubated in taurine-enriched water at a taurine concentration of 800 mg L−1 (T-800) and 0 mg L−1 (T-0) were fed to larvae from 3 to 20 days after hatching (DAH). Notochord length, body weight and specific g...

We have previously reported that night-time lighting prevents the mass death of Pacific bluefin tuna (PBT) juvenile due to collision and/or contact with the walls of sea cages, immediately after transfer to the cages, and that night-time lighting does not negatively impact fish stress levels. However, the period of night-time lighting should be lim...

The spectral sensitivity of the fish and the suitable light wavelength range for survival and growth performance of juvenile Pacific bluefin tuna (PBT) were investigated. The spectral sensitivity peak of PBT under photopic condition was observed between 449 and 503 nm, which corresponded to their natural habitat. The fish were reared in tanks irrad...

Although the survival rate of juvenile Pacific bluefin tuna Thunnus orientalis (PBT) during 30 days after stocking in sea net cages has been as low as approximately 50%, the reason for this high mortality is not clear. The dead fish were collected and counted during 30 days after stocking in a sea net cage, and the growth performance, stomach conte...

Effect of water temperature on embryonic development of yellor,vfin tuna was investigated. Eggs were incubated at different water temperatures:22, 24, 26C (Experiment-1) arrd 28, 30, 32C (Experiment-2). Developmental condition was observed and the elapsed time from the 2 or 4 cell stages until hatching was mea-sured. Hatching occurred at 18.58 h fo...

Effect of photoperiod on survival rate of juvenile Pacific bluefin tuna (PBT) was investigated. The 24L (24 hours lighting) significantly improved the survival rate compared with the 12LD (12 hours lighting and 12 hours darkness) and 24D (24 hours darkness) tanks. Next, juvenile PBT were reared under 3 different 24 hours light intensities. Fish sur...

This study examined the influence of swimbladder inflation (SBI) failure on mortality (Experiment 1), lordotic deformity (Experiment 2) and growth (Experiment 1, 2) in Pacific bluefin tuna, Thunnus orientalis, postflexion larvae and juveniles by producing larvae lacking inflated swimbladders. Experiment 1 was conducted for postflexion larvae to juv...

This study investigated the optimal timing of day to promote initial swimbladder inflation (ISI) for improved Pacific bluefin tuna (PBT), Thunnus orientalis, larval survival. Larval swimbladder inflation frequency was compared based on three experiments using different time schemes of surface film removal (SFR) from 3 to 9 days post hatch (dph). SF...

Land-based cultured juvenile Pacific bluefin tuna Thunnus orientalis (PBT) have high mortality rates due to collisions or contacts with tank walls after about 30 days of hatching. To determine the effect of night-time lighting on their survival, juvenile PBT were reared under four different night-time light intensities (0, 5, 15 and 150 lx) for 9 d...

Morphogenesis is most active during fish embryonic development with increased susceptibility to environmental stressors. In order to elucidate the causalities of malformations in fishes that produce buoyant eggs, this study estimated the time change of dissolved oxygen (DO) and carbon dioxide (DCD) concentrations in the interstitial water of red se...

It is important to produce safe cultured fish by reducing their dioxin content.We investigated the reduction of dioxin content in cultured red sea bream Pargus major by feeding artificial diets containing two sorts of fish oil with different dioxin content: CT (3 pg-TEQ/g) and MD (18 pg-TEQ/g). There was no significant difference in the growth, sur...

AFLP, amplified fragment length polymorphism screening, was conducted to identify sex characteristic DNA markers of cultured Pacific bluefin tuna (PBT), Thunnus orientalis. The AFLP screening of 4 females and 4 males with 64 primer combinations produced a total of 1038 scorable bands, of which 183 were polymorphic between individuals. Male characte...

High mortality following transfer of early juvenile Pacific bluefin tuna (PBT) aged around 30 days post hatching (about 5 cm total length) from hatchery tanks to sea net cage, particularly during the first few days, is a major problem inhibiting development of large-scale culture operations. Survival rate of the fish after stocking from land tank t...