Initial Swim Bladder Inflation Research Articles

A sensation for inflation: initial swim bladder inflation in larval zebrafish is mediated by the mechanosensory lateral line.

Larval zebrafish achieve neutral buoyancy by swimming up to the surface and taking in air through their mouths to inflate their swim bladders. We define this behavior as 'surfacing'. Little is known about the sensory basis for this underappreciated behavior of larval fish. A strong candidate is the mechanosensory lateral line, a hair cell-based sensory system that detects hydrodynamic information from sources such as water currents, predators, prey and surface waves. However, a role for the lateral line in mediating initial inflation of the swim bladder has not been reported. To explore the connection between the lateral line and surfacing, we used a genetic mutant (lhfpl5b-/-) that renders the zebrafish lateral line insensitive to mechanical stimuli. We observed that approximately half of these lateral line mutants over-inflate their swim bladders during initial inflation and become positively buoyant. Thus, we hypothesized that larval zebrafish use their lateral line to moderate interactions with the air-water interface during surfacing to regulate swim bladder inflation. To test the hypothesis that lateral line defects are responsible for swim bladder over-inflation, we showed that exogenous air is required for the hyperinflation phenotype and transgenic rescue of hair cell function restores normal inflation. We also found that chemical ablation of anterior lateral line hair cells in wild-type larvae causes hyperinflation. Furthermore, we show that manipulation of lateral line sensory information results in abnormal inflation. Finally, we report spatial and temporal differences in the surfacing behavior between wild-type and lateral line mutant larvae. In summary, we propose a novel sensory basis for achieving neutral buoyancy where larval zebrafish use their lateral line to sense the air-water interface and regulate initial swim bladder inflation.

Swimbladder non-inflation and its influence on larviculture of mandarin fish (Siniperca chuatsi)

Low occurrence of swimbladder inflation often leads to vertebral skeletal malformations and poor swimming ability, which exert numerous effects on growth, feeding, buoyancy regulation and survival rate of fish larvae. In the present study, 713 mandarin fish (Siniperca chuatsi) larvae samples ranging from 5 to 11 days post hatch (DPH) were collected to detect the rate of swimbladder inflation and calculate the body density of each sample. Swimbladder inflated fish larvae were increased with the development of DPH except 7 DPH, with 86.21% in 11 DPH whereas 27.59% in 5 DPH. Our results indicate that 5–11 DPH is the main stage for swimbladder inflation in mandarin fish larvae, following the onset of exogenous feeding. The body density of swimbladder inflated (SBI) fish larvae (0.983 ± 0.016 g/cm3) was lower than the swimbladder non-inflated (SBN) ones (1.023 ± 0.018 g/cm3), while SBI fish larvae were significant heavier (p < 0.05) than SBN group. These findings suggest that swimbladder non-inflation could significantly influenced the neutrally buoyancy maintained and live bait predation in mandarin fish. The research will contribute to understanding the influence of initial swimbladder inflation on larviculture of mandarin fish.

Requirement of access to an air–water interface for initial swim bladder inflation and ontogenetic and day–night change of body‐specific gravity in Japanese amberjack, Seriola quinqueradiata , larvae

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 larval swim bladder volume and body-specific gravity (BSG) which elucidates a part of sinking syndrome mechanism. 77.7% of larvae reared with a clearer water surface had inflated swim bladders, while those reared with oil sealed had a very low percentage lower than 6.7%. This indicates their requirement of a clearer air–water interface to initially inflate swim bladders by gulping air and the necessity of treatments to remove the surface film of rearing water. Larval BSG was estimated from their sinking speed through the bilayer sea water column which consisted of 1/2 and 1/1 sea water in the upper and in the lower layer respectively. Larval BSG increased from 1 to 4 days post hatch (dph), thereafter decreased until 9 dph and increased a little again from 10 dph, and averaged larval BSG was higher than that of sea water. This suggests the critical period of larval sinking on 3, 4 and 10 dph.

The Effect of Different Surface‐Cleaning Devices on the Success of Swim Bladder Inflation in Zander Larvae

AbstractThe failure of initial swim bladder inflation (SBI) is one of the main obstacles to successful results in Zander (also known as Pikeperch) Sander lucioperca larviculture because the larvae are unable to penetrate the oil layer on the water surface to gulp air. There are numerous technical solutions for cleaning the water surface, including using a sprayer to emulsify the oil contamination and a skimmer for trapping the oil globules on the surface. To investigate the most appropriate method for improving the SBI success rate, three different devices were evaluated in triplicate tanks. In addition to the control tanks, which were not equipped with any surface‐cleaning device other than overflow mesh, two sprayer designs (narrow, covering one‐third of the tank's diameter, versus wide, covering the tank's entire diameter) and an air‐blowing surface skimmer were set for a 16‐d trial. Freshly hatched larvae (7,000 per tank) were divided into four treatment groups in twelve 250‐L larval nursing tanks that shared a common recirculation system. Significantly higher rates of SBI were found in the tanks that were equipped with a wide‐covering sprayer (30.6 ± 13.0%) compared with the control, skimmer, and narrow‐covering sprayer groups (14.7 ± 7.5%, 4.8 ± 1.7%, and 12.2 ± 5.1%, respectively). Thus, the results of the present study indicate that the sprayer design that covers a large portion of the tank’s diameter is an appropriate solution for enhancing SBI rates in Zander larviculture.

MORPHO-FUNCTIONAL AND DEVELOPMENTAL STUDY OF SWIM BLADDER IN PRE TO POST FLEXION STAGES LARVAE OF HIMALAYAN SNOW TROUT SCHIZOTHORAX PLAGIOSTOMUS (HECKEL) REARED IN ARTIFICIAL AND NATURAL CONDITIONS

Present study deals with histology, gross morphology of the larvae and its behavioural aspects to describe the progression of the development of swim bladder in pre to post flexion stages larvae of the Himalayan Snow Trout Schizothorax plagiostomus (Heckel) reared in laboratory as well as in natural site. It reveals a very significant information in respect to derivation, tissue differentiation, initial inflation as well as factors responsible for noninflation of swim bladder especially among laboratory reared larvae. At hatching (108-110 and 124-130 hours after fertilization in laboratory and natural site respectively), larvae measured 9.00 mm and 10.5 mm in laboratory and natural site respectively, and their body cavity was mostly occupied with a huge amount of yolk. The mouth, pharynx and esophagus were impervious till 3rd day post hatching (dph). Primordial swim bladder appeared on 3rd.dph as a cluster of mesenchymal cells evaginating from the posterior dorsal surface of the differentiating esophagus. Later on it grows toward the caudal direction below the differentiating vertebral column and kidney. Initial swim bladder inflation occurred by 6-dph when larvae attained 12.50–13.50 mm length, with the onset of first exogenous feeding. During this phase a mucous like substance was also observed in the pneumatic duct as well as lumen of swim bladder of some laboratory reared larvae and later on they got mortality. By 8-dph well differentiated and inflated swim bladder becomes externally visible and pneumatic duct extended to join the dorsal wall of esophagus. A number of biotic and abiotic factors were found associated with preventing swim bladder inflation during Pre flexion to Post flexion stages.

The role of phototaxis in the initial swim bladder inflation of larval yellow perch (Perca flavescens)

The yellow perch (Perca flavescens) is a high priority species for aquaculture, with strong demand in the USA. Unfortunately, numerous developmental problems during larval rearing prevent its commercial viability. Failed swim bladder inflation (SBI) has been reported in the culture of numerous physoclistous fish species and is a prominent problem in the culture of yellow perch. Initial SBI occurs within a short period of ontogeny, and missing this opportunity results in permanent malformation of the organ. Lighting cues appear to play a role in triggering the response of rising to the surface to swallow the air required for initial SBI in several fishes including yellow perch. Larval yellow perch are photopositive, and this phototactic response seems to co-occur with the window of opportunity for SBI. Thus, we examined the role of phototactic behavior and low-intensity, moonlight-like illumination in initial SBI in yellow perch. Lights were positioned below and above the water surface in larval culture tanks to see if the presence of nighttime illumination impacted SBI success, and if the phototactic behavior of yellow perch helps them find the water surface when inflating at night. The results of this study reveal that even very low-intensity nighttime light reduces the proportion of yellow perch larvae to initially inflate regardless of the direction of the light source. Also, on treatment with no nighttime illumination, higher than expected SBI was observed, and the culture conditions that produced this success should be examined when focusing on improving SBI in the future. This research suggests that the photopositive response of yellow perch is not involved in SBI success, and lighting could play a role in hindering the process.

Optimal period for the effective promotion of initial swim bladder inflation in yellowfin tuna, Thunnus albacares (Temminck and Schlegel), larvae

Aquaculture ResearchVolume 48, Issue 10 p. 5443-5446 SHORT COMMUNICATION Optimal period for the effective promotion of initial swim bladder inflation in yellowfin tuna, Thunnus albacares (Temminck and Schlegel), larvae Tomoki Honryo, Corresponding Author Tomoki Honryo [email protected] orcid.org/0000-0002-3205-9571 Oshima Station, Aquaculture Research Institute of Kindai University, Wakayama, Japan Correspondence Tomoki Honryo, Oshima Station, Aquaculture Research Institute of Kindai University, Wakayama, Japan. Email: [email protected]Search for more papers by this authorMichio Kurata, Michio Kurata orcid.org/0000-0001-9241-6713 Oshima Station, Aquaculture Research Institute of Kindai University, Wakayama, JapanSearch for more papers by this authorAngel Guillen, Angel Guillen Aquatic Resources Authority of Panama, Wakayama, Republic of PanamaSearch for more papers by this authorYoshiki Tamura, Yoshiki Tamura Department of Fisheries, Faculty of Agriculture of Kindai University, Nara, JapanSearch for more papers by this authorAmado Cano, Amado Cano Aquatic Resources Authority of Panama, Wakayama, Republic of PanamaSearch for more papers by this authorMaria S Stein, Maria S Stein Inter-American Tropical Tuna Commission, La Jolla, CA, USASearch for more papers by this authorDaniel Margulies, Daniel Margulies Inter-American Tropical Tuna Commission, La Jolla, CA, USASearch for more papers by this authorVernon P Scholey, Vernon P Scholey Inter-American Tropical Tuna Commission, La Jolla, CA, USASearch for more papers by this authorYoshifumi Sawada, Yoshifumi Sawada Oshima Station, Aquaculture Research Institute of Kindai University, Wakayama, JapanSearch for more papers by this author Tomoki Honryo, Corresponding Author Tomoki Honryo [email protected] orcid.org/0000-0002-3205-9571 Oshima Station, Aquaculture Research Institute of Kindai University, Wakayama, Japan Correspondence Tomoki Honryo, Oshima Station, Aquaculture Research Institute of Kindai University, Wakayama, Japan. Email: [email protected]Search for more papers by this authorMichio Kurata, Michio Kurata orcid.org/0000-0001-9241-6713 Oshima Station, Aquaculture Research Institute of Kindai University, Wakayama, JapanSearch for more papers by this authorAngel Guillen, Angel Guillen Aquatic Resources Authority of Panama, Wakayama, Republic of PanamaSearch for more papers by this authorYoshiki Tamura, Yoshiki Tamura Department of Fisheries, Faculty of Agriculture of Kindai University, Nara, JapanSearch for more papers by this authorAmado Cano, Amado Cano Aquatic Resources Authority of Panama, Wakayama, Republic of PanamaSearch for more papers by this authorMaria S Stein, Maria S Stein Inter-American Tropical Tuna Commission, La Jolla, CA, USASearch for more papers by this authorDaniel Margulies, Daniel Margulies Inter-American Tropical Tuna Commission, La Jolla, CA, USASearch for more papers by this authorVernon P Scholey, Vernon P Scholey Inter-American Tropical Tuna Commission, La Jolla, CA, USASearch for more papers by this authorYoshifumi Sawada, Yoshifumi Sawada Oshima Station, Aquaculture Research Institute of Kindai University, Wakayama, JapanSearch for more papers by this author First published: 25 April 2017 https://doi.org/10.1111/are.13355Citations: 2Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume48, Issue10October 2017Pages 5443-5446 RelatedInformation

Promotion of initial swim bladder inflation and effect of initial inflation failure on skeletal malformation in cultured seven-band grouperHyporthodus septemfasciatus(Thunberg)

The effects of the removal of the oily surface film on initial swim bladder inflation and survival in cultured seven-band grouper Hyporthodus septemfasciatus were investigated during the larval stage. Additionally, the relationship between swim bladder inflation failure and malformations in later stages was examined. To explore promotion conditions for inflation, duplicate experiments were conducted under three different water surface conditions: removal of the oily surface film (ROF group), covering the water surface with an oil film (COF group), and sealing the water surface with liquid paraffin (SLP group). Larval swim bladder inflation was first observed 14 days after hatching (DAH) in the ROF group; thereafter, swim bladder inflation rates increased to 11.1% and 38.7% until the end of the experiments. This indicates that initial swim bladder inflation occurs at the pre-flexion stage in larval development. Conversely, bladder inflation was rarely observed in the COF or SLP groups, indicating the promotional effect of surface film removal on larval swim bladder inflation and suggesting that gulping atmospheric air is necessary for initial inflation. Although larval water surface death occurred frequently in the ROF group, no significant difference existed in any group between the survival rates at 10 DAH and at the end of the experiment. The incidence rate of spinal curvature and deformation of the centra was significantly higher in individuals without initial swim bladder inflation, and these malformations mainly occurred in the caudal vertebra. Therefore, the removal of the oily surface film promotes initial swim bladder inflation and reduces larval malformations.

Effect of water surface condition on survival, growth and swim bladder inflation of yellowfin tuna,Thunnus albacares(Temminck and Schlegel), larvae

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 of yolk sac larvae was significantly higher when the rearing water surface was covered with fish oil at aeration rates of 0 and 50 mL min−1. The highest mortality occurred at the highest aeration rate of 250 mL min−1 regardless of surface water condition. A second experiment was conducted twice under different water surface conditions: the water surface was covered by fish oil (FO), skimmed of fish oil (SS), and was not treated (NC). The percentage survival was not significantly different between treatments after 7 days of feeding. In contrast to the survival, the proportion of larvae with inflated swim bladders was significantly higher for the NC and SS groups than that of the FO group. Results of these experiments indicate that the addition of oil to the rearing water surface without its removal interferes with the initial swim bladder inflation in YFT larvae. These results also indicate that YFT larvae need to obtain (gulp) air at the water surface for initial swim bladder inflation, and success of initial swim bladder inflation may be crucial for their survival.

Early Morphological Development and Allometric Growth Patterns in Hatchery-Reared Red Porgy (Pagrus pagrus)

Morphological development and allometric growth were investigated in the red porgy, Pagrus pagrus, during larval development until the end of weaning at 46 days after hatching (DAH). Total length (TL) of newly hatched larvae was 2.77±0.09 mm (mean±SE). Onset of exogenous feeding occurred at 4 DAH (3.74±0.13 mm TL). Initial swimbladder inflation occured at 10 DAH (4.22±0.18 mm TL) and post-inflation became more elongate at 16 DAH (4.95±0.26 mm TL). Notochord flexion occurred between 22 DAH (5.56±0.43 mm TL) and 34 DAH (8.22±0.63 mm TL). At the end of the weaning at 46 DAH, TL of larvae was 15.81±1.36 mm. According to individual measurements of a total of 1026 larvae of 18 body parameters for allometric growth, in 19 of 35 respective regression equations, the allometry coefficients were positive, while coefficients of 7 equations showed negative allometry. The majority of all allometric changes from inflection point were expressed during the larval stage and were integrated with the metamorphosis stage. Inflections in body proportion changes occurred mainly at TL values of 3.74, 4.22 and 5.56 mm, coinciding with mouth opening, initial swimbladder inflation and flexion of notochord, respectively.

Timing to promote initial swimbladder inflation by surface film removal in Pacific bluefin tuna,Thunnus orientalis(Temminck and Schlegel), larvae

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). SFR was conducted from 05:00 to 19:00 hours (light period: S.5–19), 19:00 to 05:00 hours (dark period: S.19–5), 08:00 to 19:00 hours (S.8–19) and the entire day (S.24) in Experiment 1; from 08:00 to 19:00 hours (S.8–19-E2), 08:00 to 13:00 hours (S.8–13), 13:00 to 19:00 hours (S.13–19) in Experiment 2; and from 13:00 to 16:00 hours (S.13–16), 16:00 to 19:00 hours (S.16–19), 18:00–19:00 hours (S.18–19) in Experiment 3. The swimbladder inflation frequency at the experiment termination (9 dph) was significantly higher (P < 0.001) in S.24 (91.1 ± 5.7%), S.5–19 (92.2 ± 5.1%) and S.8–19 (93.3 ± 3.4%) than in S.19–5 (11.1 ± 5.1%) in Experiment 1, and remarkably higher in S.8–19-E2 (81.7%) and S.13–19 (88.3%) than in S.8–13 (0.0%) in Experiment 2, and significantly higher (P < 0.001) in S.16–19 (84.4 ± 5.1%) and S.18–19 (70.0 ± 12.0%) than in S.13–16 (7.8 ± 3.9%) in Experiment 3. These results suggest that the optimal timing to promote larval ISI by SFR is a few hours before the end of light period (16:00–19:00 hours) from 3 to 9 dph.

Vulnerability of larval and juvenile white sturgeon to barotrauma: can they handle the pressure?

Techniques were developed to determine which life stages of fish are vulnerable to barotrauma from expansion of internal gases during decompression. Eggs, larvae, and juvenile hatchery-reared white sturgeon (Acipenser transmontanus; up to 91 days post hatch; d.p.h.) were decompressed to assess vulnerability to barotrauma and identify initial swim bladder inflation. Barotrauma-related injury and mortality were first observed 9 d.p.h., on the same day as initial exogenous feeding. However, barotrauma-related injury did not occur again until swim bladder inflation 75 d.p.h. (visible at necropsy and on radiographs). Swim bladder inflation was not consistent among individuals, with only 44% being inflated 91 d.p.h. Additionally, swim bladder inflation did not appear to be size dependent among fish ranging in total length from 61 to 153 mm at 91 d.p.h. The use of a combination of decompression tests and radiography was validated as a method to determine initial swim bladder inflation and vulnerability to barotrauma. Extending these techniques to other species and life-history stages would help to determine the susceptibility of fish to hydro turbine passage and aid in fish conservation.

Ontogeny of body density and the swimbladder in yellowtail kingfish Seriola lalandi larvae

The ontogeny of larval body density and the morphological and histological events during swimbladder development were investigated in two cohorts of yellowtail kingfish Seriola lalandi larvae to understand the relationship between larval morphology and body density. Larvae <3 days post hatch (dph) were positively buoyant with a mean ± s.d. body density of 1.023 ± 0.001 g cm(-3). Histological evidence demonstrated that S. lalandi larvae are initially transient physostomes with the primordial swimbladder derived from the evagination of the gut ventral to the notochord and seen at 2 dph. A pneumatic duct connected the swimbladder to the oesophagus, but degenerated after 5 dph. Initial swimbladder (SB) inflation occurred on 3 dph, and the inflation window was 3-5 dph when the pneumatic duct was still connected to the gut. The swimbladder volume increased with larval age and the epithelial lining on the swimbladder became flattened squamous cells after initial inflation. Seriola lalandi developed into a physoclist with the formation of the rete mirabile and the gas-secreting gland comprised low-columnar epithelial cells. Larvae with successfully inflated swimbladders remained positively buoyant, whereas larvae without SB inflation became negatively buoyant and their body density gradually reached 1.030 ± 0.001 g cm(-3) by 10 dph. Diel density changes were observed after 5 dph, owing to day time deflation and night-time inflation of the swimbladder. These results show that SB inflation has a direct effect on body density in larval S. lalandi and environmental factors should be further investigated to enhance the rate of SB inflation to prevent the sinking death syndrome in the early life stage of the fish larvae.

Timing of Initial Swim Bladder Inflation in Larvae of Greater Amberjack Seriola dumerili Reared under Different Temperature and Light Conditions

Timing of Initial Swim Bladder Inflation in Larvae of Greater Amberjack Seriola dumerili Reared under Different Temperature and Light Conditions

Swimbladder inflation, growth and survival of yellowtail kingfishSeriola lalandi(Valenciennes, 1833) larvae under different temperature, light and oxygen conditions

Poor swimbladder inflation leads to low fish survival due to resulting spinal deformities and the inability to feed and develop normally. Failure of swimbladder inflation may be attributed to the inappropriate range of abiotic conditions. This study investigated the effects of temperature, light source and intensity, and oxygen conditions on initial swimbladder inflation, growth and survival of yellowtail kingfish Seriola lalandi larvae. The study consisted of four separate trials including low (21.5°C) and high (24.5°C) temperatures, natural and artificial light sources, low (1000 lux) and high (32 000 lux) light intensities, and ambient and supersaturated dissolved oxygen. Initial swimbladder inflation was only significantly affected by light source, with the highest inflation rate (97.5 ± 3.5%) under artificial light. Fish growth was improved at the higher temperature and at the higher light intensity. Survival was only significantly influenced by light intensity, with the highest survival (11.0 ± 2.3%) at the high intensity (32 000 lux). This study indicates that light source affects swimbladder inflation timing and high artificial light intensity improves larval fish growth and survival.

Influence of initial swimbladder inflation failure on survival of Pacific bluefin tuna,Thunnus orientalis(Temminck and Schlegel), larvae

This study investigated the influence of initial swimbladder inflation (ISI) failure on survival of Pacific bluefin tuna (PBT), Thunnus orientalis, larvae to prevent mass mortality due to sinking death. In Experiment 1, swimbladder inflation frequency and survival within an ISI promoted (PS) group, for which surface film of rearing water was removed, and a group without ISI promotion (NPS) were compared in 20 and 30 kL tanks. The PS group demonstrated significantly higher swimbladder inflation frequency and increased survival than the NPS group within 20 kL tanks at 9 days post hatching (dph). Similar tendencies were observed within 30 kL tanks. In Experiment 2, larval distribution and swimbladder inflation frequency in the night-time were examined through larval sampling within the upper and middle layers of the water column and tank bottom within 1.6 and 30 kL tanks at 5 dph. Larvae at tank bottom had higher distributional density and significantly lower swimbladder inflation frequency than those distributed in the upper and middle layers within 1.6 kL tanks. Similar tendencies were observed within 30 kL tanks. Results of this study suggest the improvement of larval survival due to prevention of sinking death through ISI promotion in mass-scale PBT larviculture.

Morphological Development and Allometric Growth of Sharpsnout Seabream (Diplodus puntazzo) Larvae

In this study, morphological development and allometric growth were investigated in the sharpsnout seabream, Diplodus puntazzo, during larval development until the end of the weaning on day 42. Average total length (TL) of newly hatched larvae was 2.91±0.11 mm and it was 3.35±0.13 mm TL at the onset of feeding at 4 days after hatching (DAH). Initial swimbladder inflation occurred at 10 DAH (5.11±0.45 mm TL) and post-inflation became more elongate at 15 DAH (5.95±0.43 mm TL). The notochord flexion occurred between 5.95±0.43 mm TL at 15 DAH and 7.98±0.72 mm TL on 24 DAH. At the end of weaning, larvae were 16.03±1.74 mm TL at 42 DAH. The majority of all allometric changes from inflection point were integrated with the larval and the metamorphosis stage. Inflections in body proportion changes occurred mainly at 5.12, 5.95 and 7.98 mm TL, corresponding to initial swimbladder inflation and flexion period of notochord, respectively.

Promotion of initial swimbladder inflation in Pacific bluefin tuna, Thunnus orientalis (Temminck and Schlegel), larvae

Initial swimbladder inflation (ISI) of Pacific bluefin tuna (PBT), Thunnus orientalis, larvae was studied to increase the survival of cultured larvae. Experiment 1 was conducted to explore promotion and inhibition of ISI under different water surface conditions; including the use of surface skimmer to remove autogenous surface substances (SS), covering the water surface with liquid-paraffin-layer (LP) and oil film (OF), and a control (non-treatment, NT). Significantly higher inflation frequency was observed in SS (62.2%) than NT (11.9%), LP (2.7%) and OF (3.9%). This indicates that ISI in PBT larvae can be promoted by removal of surface substances on rearing water which inhibit larval air gulping. Experiment 2 aimed to elucidate proper day of larval age to start skimming for promoting ISI with four different periods of oil film removal: from 3 to 8 (SF3D), 4 to 8 (SF4D), 5 to 8 (SF5D), 6 to 8 (SF6D) days-post-hatch (dph). Significant improvement in ISI frequency was observed in SF3D (80.2%) but the frequency was very poor in SF4D, SF5D, and SF6D (17.8–7.5%). This implies the need of oil film removal without missing a narrow window, 1 day of 3 dph, to promote ISI in practical PBT larviculture.

Swimbladder inflation and its implication to the culture of marine finfish larvae

AbstractThis review examines the initial swimbladder inflation in cultured finfish larvae and the mechanisms controlling body buoyancy and the distribution of larvae during the critical early development stages. The literature suggests that the body buoyancy of larvae affects their distribution in the tank and fish with low buoyancy are likely to sink to the bottom leading to mortality. Initial swimbladder inflation occurs in a finite period of the postlarval stage and a number of biotic and abiotic factors have been associated with preventing inflation during the ‘window’ period. In recent times larval rearing techniques have been advanced, but it is still a challenge to increase the initial swimbladder inflation rates and maintain larval positioning in the water column to reduce mortality. This review shows that various nutritional and abiotic factors can be manipulated in the culture of many finfish species to achieve high rates of swimbladder inflation and reduce deformations and mortality during early larval rearing.

Allometric Growth in Hatchery‐Reared Gilthead Seabream

AbstractMorphological development and allometric growth were investigated in the gilthead seabream Sparus aurata during larval development until the end of the weaning period on day 41. Fertilized eggs had a diameter of 1.01 ± 0.02 mm (mean ± SE) and a lipid vesicle diameter of 0.227 ± 0.021 mm. Mean total length (TL) was 2.68 ± 0.04 mm for newly hatched larvae and 3.57 ± 0.09 mm at the onset of feeding (4 d after hatching [DAH]). At 10 DAH, initial swim bladder inflation occurred, mean TL was 4.19 ± 0.08 mm, and notochord length (NL) was 4.00 ± 0.07 mm. At 16 DAH, the swim bladder became more elongated, TL was 5.13 ± 0.09 mm, and NL was 4.94 ± 0.07 mm. Notochord flexion occurred at 6.46 ± 0.11 mm TL on 23 DAH, and the complement of the flexion occurred at 8.67 ± 0.109 mm TL on 35 DAH. At the end of the weaning period (at 41 DAH), larvae were 10.85 ± 0.116 mm TL. The majority of all allometric changes from the inflection point were expressed during the larval stage and integrated with the metamorphosis stage. Inflections in body proportion changes occurred mainly at 4.19 and 7.04 mm TL, corresponding to initial swim bladder inflation and the notochord flexion period, respectively.