Swim bladder inflation as a possible cause of saddleback-like syndrome malformation in hatchery-reared red spotted grouper <Emphasis Type="Italic">Epinephelus akaara</Emphasis>

Saddleback-like syndrome is one of the most frequently observed malformations in hatchery-reared red spotted grouper Epinephelus akaara. Saddleback-like syndrome is characterized by a V-shaped dorsal-profile depression behind the head region accompanied by deformities or misalignments of the first to fourth neural spines on the vertebral column and the first to fourth pterygiophores of the dorsal fin. Abnormal swim bladder inflation in several finfish species leads to malformations, particularly of the vertebral column. The present study examined the influence of swim bladder inflation on saddleback-like syndrome in hatchery-reared red spotted grouper. The incidence of saddleback-like syndrome increased as swim bladder inflation rate increased. Additionally, the incidence of saddleback-like syndrome among juveniles with inflated swim bladders was significantly higher than that among juveniles with uninflated swim bladders. The larval swim bladder is located just below the first to fifth vertebrae and the first to fifth dorsal spines, where saddleback-like syndrome occurs. Our results suggest that an inflated swim bladder increases the risk of saddleback-like syndrome in hatchery-reared red spotted grouper.     

Ontogeny of the shi drum Umbrina cirrosa (Linnaeus 1758), a candidate new species for aquaculture

The ontogeny of shi drum Umbrina cirrosa (Linnaeus 1758), a candidate new species for aquaculture, was studied throughout the entire larval phase. Geometric morphometric analysis revealed two clear inflection points (7.0 and 12.7 mm total length, TL) in the shape ontogeny of this species, separating the studied period into three phases of different allometric priorities. Spline graphs demonstrated that the major non‐uniform shape ontogeny correlated with the development of the fins, the anterior dorsal area of the body, the caudal peduncle, the eye and the mouth. Concerning the morphological features, shi drum larvae are characterized by an upward anterior bending of the notochord. The ontogeny of the fins began with the formation of the pectoral buds (2.9 mm TL), continued with the notochord flexion (4.3 mm TL, associated with the caudal fin development), the appearance of the pelvic buds, the first anal rays (4.5 mm TL) and the first dorsal rays (4.8 mm TL). Shi drum juveniles presented 25 vertebrae and the following dominant fin types: D XI,23, AII,6, VI,5, P17 and C17.     

Skeletal development and abnormalities of the vertebral column and fins in larval stage of hatchery‐reared American shad,Alosa sapidissima

The present study describes the skeletal development and the occurrence of deformities in American shad, Alosa sapidissima, larvae from hatching to 45 days after hatching (DAH). The ontogeny of the vertebral column started at 16 DAH (days after hatching), with the formation of the posterior neural and haemal arches, and was complete at 28 DAH. In comparison, the vertebral centra started to form at 16 DAH, with ossification being visible in all centra at 38 DAH. The pectorals were the only fins that formed before the onset of feeding (at 2 DAH), with ossification being complete at 45 DAH. The caudal fin formed at 5 DAH, with ossification being complete at 40 DAH. Dorsal and pelvic fin development began at 6 DAH and 20 DAH respectively. The ossification of both the dorsal and pelvic fins was visible at 45 DAH. The anal fin began forming at 14 DAH, and was complete at 30 DAH. The ossification of the anal fin was complete at 45 DAH. Overall, 22 types of skeletal deformities were detected in about 41% of individuals. Most anomalies were detected in the haemal region, while the fewest anomalies were detected in the anal fin. In addition, the frequency of deformities gradually increased with fish age at the different developmental stages. Our results are expected to contribute baseline information on how rearing conditions impact skeletal development, in addition to identifying potential causative factors of skeletal deformities.     

The prevalence of vertebral deformities is increased with higher egg incubation temperatures and triploidy in Atlantic salmon Salmo salar L.

Suboptimal egg incubation temperature is a risk factor for the development of skeletal deformities in teleosts. Triplicate diploid and triploid Atlantic salmon, Salmo salar L., egg batches were incubated at 6, 8 and 10 °C up until first feeding, whereupon fish were reared on a natural temperature before examination for externally visible skeletal deformities (jaw and spine) and radiographed for vertebral deformities and morphology at the parr stage. Increasing incubation temperatures and triploidy increased the number of fish showing one or more deformed vertebrae. Triploids had significantly higher mean vertebrae cranio‐caudal length (L) and dorsal‐ventral height (H) ratio at 6 and 10 °C than diploids, but triploidy had no effect on mean vertebrae centra area. Triploids demonstrated an increase in lower jaw deformities with increased incubation temperature, whereas jaw deformities were rare in diploids. Fish incubated at 10 °C had a significantly lower mean vertebral number than fish incubated at 6 °C, and triploids had lower mean vertebral numbers than diploids. Diploid fish with 58 vertebrae had a significantly higher mean vertebral centra area than fish with 59 vertebrae, but vertebral number did not affect the mean vertebral L/H ratio. The results are discussed with respect to the welfare and production of farmed salmonids.     

Skeletal development and deformities in cultured larval and juvenile seven-band grouper, Epinephelus septemfasciatus (Thunberg)

The seven‐band grouper, Epinephelus septemfasciatus (Thunberg), is currently recognized as a potential new species for aquaculture in Japan. This study describes normal and abnormal skeletal development of the jaw and vertebrae in cultured larvae and early juveniles of E. septemfasciatus. The ontogenetic stages at which skeletal deformities of jaw and vertebra developed were also described for this species. Osteological observations were made using a clearing and staining method for larvae and soft X‐ray photographs for juveniles. A high incidence of skeletal deformities was observed in the jaws and vertebral column during the larval and juvenile stages. Most of the jaw deformities were explained by an abnormal maxilla curvature. Jaw deformities were visually evident from flexion stage after ossification of the deformed elements. Deformities in the vertebral column (mostly lordosis) were observed from the post‐larval stage and became more evident as growth proceeded. The lordosis generally occurred on the positions of the 8–11th vertebra. These types of deformities are compared with those of other species, and possible causative factors of the skeletal deformities are discussed.
     

Saddleback syndrome in European sea bass Dicentrarchus labrax (Linnaeus, 1758): anatomy,ontogeny and correlation with lateral‐line,anal and pelvic fin abnormalities

This study focused on the anatomy and ontogeny of saddleback syndrome (SBS) in reared European sea bass. The abnormality was detected at an unusually high frequency (12–94%) during a routine quality control in a commercial hatchery. Anatomically the abnormality was mainly characterized by the loss of 1–5 hard spines and severe abnormalities of the proximal pterygiophores (anterior dorsal fin), size reduction of a few lepidotrichia, missing lepidotrichia and/or lepidotrichia of poor ossification (posterior dorsal fin). SBS was significantly correlated with abnormalities of the anal and pelvic fins in all the examined populations. Moreover, in juvenile fish, SBS was significantly correlated with an abnormal lack of sectors of the lateral line. The examination of early larval samples revealed that SBS was ontogenetically associated with severe abnormalities of the primordial marginal finfold, which developed at the flexion stage (ca 8.5–11.0 mm SL). Histologically, these abnormalities were associated with extensive epidermal erosion. The results are discussed in respect of the critical ontogenetic period and the possible causative factors of SBS in European sea bass. It is suggested that causative factors acted during a wide ontogenetic period including flexion and metamorphosis phases.     

Early development and allometric growth in hatchery‐reared characin Brycon orbignyanus

The characin piracanjuba, Brycon orbignyanus (Valenciennes, 1850), has been recognized as a candidate species for aquaculture. The early morphological development and allometric growth of hatchery‐reared piracanjuba were studied from hatching to the juvenile stage, at water temperature of 27.9 ± 0.6°C. Growth, in total length (TL), was linear during that period. At hatching (3.4 ± 0.2 mm TL), the non‐pigmented free embryo had most functional systems not fully differentiated. The primordial finfold was almost completely absorbed, except the preanal segment, in individuals measuring 9.1 ± 0.4 mm TL. Retinal pigmentation occurred as early as 24 hours posthatching (hph). The yolk sac was no longer observed after 60 hph. Body proportion and growth rates changed considerably during early morphological development. The head experienced positive allometric growth in length throughout the interval of study, and at the inflexion point of 6.6 mm TL, head growth had reduced significantly, but still remained allometrically positive. Trunk length showed negative allometric growth throughout the period of study. The growth of the postanal length was allometrically positive until the inflexion point at 7.1 mm TL, and thereafter decreased to near isometric. The allometric growth changes in the piracanjuba during initial life likely result from selective organogenesis directed towards survival priorities.     

Comparative performance of growth,vertebral structure and muscle composition in diploid and triploid Paralichthys olivaceus

Growth, skeletal structure and muscle composition of cold‐shock‐induced triploid olive flounder Paralichthys olivaceus were investigated. The average values of total length and total weight of triploids were higher than those of diploids from 5 to 11 months posthatch (mph). The growth difference disappeared after 11 mph. The skeletal structure of flounder at 11 mph was observed by X‐ray imaging method. There are four kinds of vertebral deformity including vertebrae fusion, one‐sided compression, two‐sided compression and vertically shifted. The trunk region (V8–18) and tailing end of the vertebral column were the predominant locations of deformity. In general, the frequencies of vertebral deformities in triploids (60.0%) were higher than those in diploids (33.3%, p < 0.05). Both the number of fish with deformed vertebrae and the average frequencies of deformed vertebrae in triploids were significantly higher than those in diploids (p < 0.05). The muscle tissues of diploid and triploid flounder at 11 mph contain the same types of fatty acid and free amino acid profiles. The number of fatty acids with significant higher contents in diploids and triploids was one and ten, respectively (p < 0.05). The contents of free amino acids showed no difference between triploid and diploid fish.     

Association of a lordosis-scoliosis-kyphosis deformity in gilthead seabream (Sparus aurata) with family structure

Skeletal deformities constitute a major problem for aquaculture industry by decreasing the final value of the fish. An analysis of skeletal malformations in 11,640 fish was performed considering families and triplicates per family. Thirtynine different skeletal abnormalities were detected, such as lordosis, vertebral fusion, absence of one or both operculum, bent-jaw, etc. Moreover, a new unusual complex spinal column deformity consisting of a consecutive repetition of lordosis, scoliosis and kyphosis (LSK) from the head to the caudal fin was described. This syndrome was statistically associated with the family structure (Z_{2H–family,LSK}=3.49; p<0.05). The incidence of this deformity was 0.2% in the whole population, and 6.5% within the affected family (2H). The environmental and genetic causes are discussed.     

Early development and allometric growth in hatchery‐reared Eurasian perch,Perca fluviatilis L.

The morphological development and allometric growth patterns of Eurasian perch, Perca fluviatilis L., a highly valued commercial species, were studied under intensive rearing conditions from hatching up to 50 DPH (Days Post Hatch). Based on the external morphology, four different phases during early development of Eurasian perch were identified: pre‐flexion larva 0–20 DPH (5.70–10.16 mm TL); flexion larva 22–30 DPH (11.09–15.14 mm TL) and post‐flexion larva/juvenile 32–50 DPH (18.00–24.75 mm TL). The results indicate that growth period when final replacement of all temporary (larval) structures and most important changes in the shape of P. fluviatilis occurred (between 13.95 and 24.06 mm TL, during flexion and post‐flexion phase) can be considered as a transitional period between the larva and juvenile. All body segments, except trunk length and tail length showed fast growth (positive allometry) throughout the entire studied period or up to the respective inflexion point with a common tendency to isometry. In addition, the specific behaviours (e.g. pelagic way of life) of Eurasian perch larvae resulted in some characteristic allometric growth patterns in the posterior region, different from the majority of other teleosts. The results are discussed with respect to the ontogeny of the functional morphology under both ecological and aquaculture considerations.     

美洲鲥仔稚鱼脊柱及附肢骨骼系统的早期发育

使用软骨-硬骨双染色技术,描述了美洲鲥(Alosa sapidissima)仔稚鱼(1~51日龄)脊柱、胸鳍、尾鳍、背鳍等附肢骨骼的形态发育特征。结果显示,脊柱的发育开始于10日龄仔鱼尾部的髓弓、脉弓和尾下骨的出现,16日龄髓弓和脉弓延伸形成髓棘和脉棘,19日龄脊柱出现分节的硬骨环,23日龄所有椎体形成。各附鳍支鳍骨发育顺序先后依次为胸鳍、尾鳍、背鳍、臀鳍和腹鳍。胸鳍在2日龄时出现乌喙骨,13日龄形成软骨质的胸鳍支鳍骨,19日龄仔鱼肩带和上匙骨开始骨化;尾鳍的尾下骨最早出现在5日龄,12日龄尾鳍形成2枚尾上骨、1枚尾杆骨和6枚尾下骨,19日龄仔鱼尾椎和尾鳍率先开始骨化,直至23日龄尾鳍骨骼系统钙化完全。最终背鳍和臀鳍分别形成18和22根鳍条。美洲鲥骨骼发育研究对其早期发育功能趋向、环境优化及分类鉴定有重要作用。     

Identification of stocked muskellunge and potential for distinguishing hatchery‐origin and wild fish using pelvic fin ray microchemistry

The effectiveness of pelvic fin ray microchemistry of muskellunge, Esox masquinongy Mitchill, to identify stocked individuals along with the potential to identify naturally reproduced fish were evaluated. Fish and water samples were obtained from one hatchery and seven lakes with natural differences in water Sr:Ca to determine whether location‐specific environmental signatures were recorded in sectioned muskellunge pelvic fin rays, including fish of known environmental history. Water and fin ray Sr:Ca were strongly correlated. Six lakes in Illinois possessed Sr:Ca signatures that were distinct from the hatchery where muskellunge were raised, resulting in pronounced shifts in Sr:Ca across sectioned fin rays of stocked fish. Hatchery and lake‐specific Sr:Ca signatures were stable across years. Sixteen of 19 individual fish known to have been stocked based on PIT tags implanted at stocking were correctly identified as hatchery‐origin fish using fin ray core Sr:Ca. Results also indicated that the hatchery Sr:Ca signal can be retained for at least 7 years in fin rays of stocked fish. Fin ray microchemistry is a non‐lethal approach for determining environmental history of muskellunge that could be used to assess movement patterns in lake and river systems and the degree to which muskellunge populations are supported by natural reproduction and stocking.     

Early life history of yellow puffer,Chonerhinos naritus (Richardson, 1848) from Sarawak,Northwestern Borneo

The growth and morphological development including fins, spine distribution and pigmentation of larval and juvenile of hatchery‐reared yellow puffer, Chonerhinos naritus were described to provide essential information on the early life history of this species. The total length (TL) of newly hatched larvae was 3.42 ± 0.23 (mean ± SD) mm, reaching 5.66 ± 0.38 mm on 5 days after hatched (DAH), 7.80 ± 0.28 mm on 11 DAH, 9.88 ± 0.40 mm on 27 DAH and 10.92 ± 0.58 mm on 30 DAH. The yolk was completely absorbed in preflexion larvae at 4 DAH. The mouth opening started at 3 DAH of yolk sac larvae, while the teeth appeared starting from preflexion larvae at 7 DAH. Overall aggregate fin ray numbers including caudal fin attained full complement in postflexion larvae at 27 DAH. Several melanophores with appearance of small stellate were first appeared dorsally on the head of flexion larvae at 13 DAH, expanded at the dorsal region of the head, above the eye in juveniles at 30 DAH. The spines first appeared in preflexion larvae of C. naritus at 7 DAH, covering the ventral skin region below pectoral fin base and expanded to the ventral part of the body and nearly covered the whole abdomen region before the anus and below the eyes in juveniles. C. naritus remain as larvae for approximately 29 days, during which they metamorphose to the juvenile stage prior to sexual maturation. Observations in larvae development of C. naritus revealed similar characteristics with other Tetraodontidae species.     

Osteological ontogeny and malformations in larval and juvenile golden pompano Trachinotus ovatus (Linnaeus 1758)

The osteological ontogeny and the incidence of deformities occurred in vertebral column and caudal complex were studied from 1 day post hatch (DPH) to 31 DPH in Trachinotus ovatus. Results indicate that the development of both caudal complex and vertebral column initiated between 7 DPH and 9 DPH along with the calcification of haemal arches and neural arches, and occurrence of caudal elements. The last element of caudal complex, uroneural, appeared on 18 DPH. A high number of malformations in the vertebral column and caudal complex were detected in this study. More than 33% experimental fish exhibited at least one type of malformation. Results from this study provide the first reference on the osteological ontogeny and malformation of golden pompano. Such information can be applied to the quality control for fingerling production in golden pompano.     

Effects of baffles and isolation on dorsal fin erosion in steelhead trout, Oncorhynchus mykiss (Walbaum)

Abstract. Dorsal fin condition was evaluated in two groups of hatchery-reared steelhead trout, Oncorhynchus mykiss (Walbaum), and compared to wild fish. Hatchery fish were reared either in nursery tanks with baffles or in isolation (1 fish/rearing space). Evaluations were conducted to determine differences in dorsal fin condition between these groups and to monitor the progression and severity of fin damage. Isolated hatchery and wild steelhead trout maintained perfect dorsal fins with characteristic white margins. Hatchery fish reared in nursery tanks with baffles experienced dorsal fin erosion that started when the fish were about 40mm total length (30 days after being on feed). This erosion continued until dorsal fin length averaged only 2·3 mm in fish 161–200 mm total length in contrast to an average dorsal fin length of 20·9mm in wild fish of the same size.     

Osteological development and anomalies in larval stage of hatchery‐reared yellow catfish Pelteobagrus fulvidraco

Comprehensive knowledge of osteological development of fish not only provides means for understanding its functional development, but also allows early detection of skeletal anomalies. The present study was conducted to determine osteological development and occurrence of anomalies from the first to the 40th day after hatching (DAH) for yellow catfish Pelteobagrus fulvidraco, a commercially important species in China. Vertebral ontogeny started with formation of anterior neural arches at 3 DAH, and completed at 6 DAH. Vertebral centra started to develop at 4 DAH and ossification in all centra was visible at 15 DAH. Caudal fin appeared at 2 DAH and ossification was visible at 26 DAH. The onset of dorsal and anal fins appeared at 4 DAH and their ossifications were visible at 20 DAH. Pectoral fins were present before first feeding and formed entirely at 9 DAH, and their ossifications were visible at 21 DAH. Pelvic fins appeared at 9 DAH, and formed completely at 21 DAH. The ossification of pelvic fins was not finished until the end of the experiment (40 DAH). 24 types of skeletal anomalies were observed. About 20% of individuals showed at least one anomaly. Haemal vertebrae anomalies occurred at the highest frequency, followed by pre‐haemal, caudal vertebrae and anal fin anomalies, and caudal fin had the lowest anomalies frequency. For the first time, our study determined osteological development and anomalies incidence in larval yellow catfish, which help further investigations into rearing conditions leading to appearance of these anomalies to prevent their incidence.     

Repeatability of fin length measurements using digital image analysis and studies of fin erosion as indicator of social interactions in Atlantic cod (Gadus morhua)

The aims of this study were to examine fin erosion caused by social interactions between Atlantic cod (Gadus morhua) juveniles, and to evaluate the repeatability of recorded fin length using digital image analysis (DIA). Fin length of 2100 juvenile Atlantic cod was analysed using DIA, during a 6 weeks experiment. The lengths of the three dorsal fins and the caudal fin were measured by three different assessors (M, K, B) three times during the experiment. Repeatability was based on a sub set of data from 42 randomly chosen fish. Assessor M measured the length of the fins of the 42 fish three times (M1, M2, M3). M1 and M2 were done on the same day, while M3 was conducted 2 weeks later. Assessor K measured two times with a 2‐year interval, and assessor B measured the fin length only once. The correlations between replicated measurements within assessor were highest for assessor M measured on the same day indicating an effect of memory. Repeatability of fin length ranged from 0.57 to 0.73 for the four fins. Social interaction with respect to fin erosion was studied using data on the four fins from all 2100 fish. ‘Relative fin length’ (fin length/total body length × 100) was calculated to assess fin erosion. Results indicated that all four fins were eroded due to social interactions, but the caudal fin was most severely eroded. In conclusion, DIA can be used to measured fin length but the method could be improved by using chromatic pictures.     

Quantitative genetic parameters for growth-related and morphometric traits of hatchery-produced Japanese flounder Paralichthys olivaceus in the wild

To understand quantitative genetic characteristics of hatchery‐produced Japanese flounder in the wild, heritability and genetic correlation of growth‐related and morphometric traits were examined in yearling released individuals at a coastal region in northeast Japan. Quantitative genetic parameters were estimated with restricted maximum likelihood following reconstruction of pedigree by a likelihood method using seven microsatellite loci. Estimates of heritability were 0.65 and 0.51 for growth‐related traits (body length and the proportion of body length to body depth) and 0.45–0.62 for morphometric traits (vertebral count and dorsal and anal fin ray counts). Genetic correlation was significantly positive (0.61) between dorsal and anal fin ray counts, indicating the possibility of pleiotropic genes or gametic phase disequilibrium for these traits. All the estimates of heritability and genetic correlation in the released individuals were close to those of hatchery‐reared juveniles, suggesting that yearling released individuals had similar quantitative genetic characteristics of growth and morphometric traits in the wild to hatchery‐reared juveniles.     

Morphological development of larval and juvenile blacktip grouper, <Emphasis Type="Italic">Epinephelus fasciatus</Emphasis>

The morphological development of larval and juvenile blacktip grouper, Epinephelus fasciatus, was examined using a hatchery-reared series. By about 5 mm body length (BL), the larvae developed characteristic pigmentation patterns of groupers, such as melanophores on the dorsal part of the gut, on the tips of the second-dorsal and pelvic fin spines, and on the midpoint of the tail to form a cluster. In addition, characteristic spines of groupers, such as spinelets on the second-dorsal and pelvic fin spines, and the preopercular angle spine developed by about 6 mm BL. The notochord end was in the process of flexion in larvae of 6–7 mm BL, by when major melanophores, spines, and jaw teeth started to appear. After the fin ray counts attained the adult complement at about 14 mm BL, somewhat densely pigmented bands started to appear on the body. The fish had the five distinct transverse bands and attained adult-like attire at about 40 mm BL when the major head spines disappeared and body parts in relation to BL became stable.     

New insight on vertebral anomalies in cultured Senegalese sole (Solea senegalensis,Kaup) at early stages of development

Senegalese sole (Solea senegalensis, Kaup) is a promising flatfish species in aquaculture. However, skeletal anomalies are still a great concern in sole farming. Investigation of this issue is crucial to improving larval quality and optimizing production. The aim of this study was to thoroughly assess anomalies in the rachis of reared sole at early developmental stages. Sole (n = 507) were sampled at 31 or 32 days after hatching (dah). The specimens were stained with alcian blue and alizarin red and evaluated for the detection of vertebral deformities. Most fish presented 9:34:3 vertebrae in abdominal, caudal and caudal complex regions, respectively. Remarkably, all specimens showed at least one spinal anomaly. Alterations of neural/haemal elements, as well as deformities of hypurals, parhypural and epural, were recurrent. Vertebral body anomalies and/or vertebral column deviations were identified in 52% of the individuals. Vertebral deformations and fusions were common, especially in caudal complex. ‘Minor’ anomalies were predominant, and some of the detected disorders might be a result of non‐/low‐pathological processes. These results contribute a new insight into the main skeletal anomalies affecting cultured sole larvae. Further research is required to determine their impact on fish welfare and external appearances at commercial stages.