Assessment of temperature or salinity effects on larval development by catecholamine‐induced metamorphosis of hatchery‐reared flat oyster,Ostrea angasi (Sowerby 1871) larvae

A need to improve larval rearing techniques led to the development of protocols for catecholamine‐induced settlement of flat oyster, Ostrea angasi, larvae. To further refine these techniques and optimize settlement percentages, the influence of salinity or temperature on development of O. angasi larvae was assessed using epinephrine‐induced metamorphosis. Larvae were reared between salinities of 15–35 and temperatures between 14.5 and 31°C. The greatest percentage survival, growth, development occurred when larvae were reared between 26 and 29°C and between salinities of 30 and 35. Larvae reared outside this salinity and temperature range exhibited reduced growth, survival and/or delayed development. Short‐term (1 h) reduction in larval rearing temperature from 26°C to 23.5°C significantly increased larval metamorphosis without affecting larval survival. Short‐term (1 h) increase in larval rearing temperature from 26°C to 29 and 31°C decreased larval survival and metamorphosis. To ensure repeatability in outcomes, tests showed that larvae sourced from different estuaries did not vary significantly in their metamorphic response to short‐term temperature manipulation and epinephrine‐induced metamorphosis.     

Effect of incubation temperature on the embryonic development and yolk‐sac larvae of the Pacific red snapper Lutjanus peru (Nichols & Murphy, 1922)

The effect of incubation temperature on embryonic development and yolk‐sac larva of the Pacific red snapper Lutjanus peru were evaluated by testing the effect of 26, 28 and 30°C, as this is the natural thermal interval reported during the spawning season of Pacific red snapper in the Gulf of California, Mexico. Sixteen developmental stages were observed. The incubation temperature affected the rate of development and time to hatching, being shorter at 30 than at 26°C, but no significant effect (P < 0.05) on larval length at hatching was registered. The depletion rate of yolk sac and oil globule was affected by incubation temperature particularly during the first 12 h post hatching (hph). At the end of the experiment (48 hph), significantly (P < 0.05) larger larvae were recorded at 26°C (TL = 3.22 ± 0.01 mm) than at 28° (TL = 3.01 ± 0.02 mm) and 30°C (TL = 2.97 ± 0.05 mm). Incubation of newly fertilized eggs at 26°C produces larger larvae, which may help to improve feeding efficiency and survival during first feeding.     

Embryonic and larval development of serpae tetra Hyphessobrycon eques (Steindachner, 1882)

In this study, the embryonic and larval development stages of one of the most important ornamental fish serpae tetra (Hyphessobrycon eques) are described. The early life stage is documented from fertilization until the beginning of the juvenile period. The fertilized eggs (the average diameter = 938.55 ± 35.20 µm) were incubated at a water temperature of 26 ± 0.5°C. The cleavage finished in 1:10 hr (=h) and the early blastula stage occurred at 1:26 hr post fertilization (hpf). The gastrulation started at 3:05 hpf, and 50% epiboly was observed at 3:25 hpf. Segmentation stage was monitored at 7:26 hpf. Embryonic developmental stage was completed and hatching occurred 20–21 hpf. The total length (TL) of newly hatched larvae was 2.64 ± 0.21 mm. The larval development of serpae tetra was divided into four different periods: Yolk‐sac larva (1–4 DAH, TL = 2.77 ± 0.09 mm ‐ 3.85 ± 0.11 mm), preflexion larva (5–12 DAH), flexion larva (13–15 DAH, TL = 5.78 ± 0.46 mm on the 15th day) and post‐flexion larva (16–30 DAH, TL = 10.7 ± 0.27 mm on the 28th–30th days). The mouth and anus are closed at 1 DAH. The mouth and anus opened at 4 DAH. Exogenous feeding started on the 4th day. The first gulping of the swim bladder was on days 3. The larva begins to swim freely, and the yolk sac was completely consumed at 4 DAH. Histological structures of the eye and brain of new hatched larva were clearly identified at 1 day after hatching (DAH). According to histological findings, the digestive system (stomach, intestine) started to develop and the liver could be seen on the ventral side of the swim bladder at 5 DAH. No histological difference was observed between the anterior intestine and the posterior intestine at 15–16 DAH. The larval metamorphosis was completed, and the larvae transformed into juveniles at 28–30 DAH.     

Spawning behaviour,early development and first feeding of the bluestriped angelfish [Chaetodontoplus septentrionalis (Temminck & Schlegel, 1844)] in captivity

Successful natural spawning of Chaetodontoplus septentrionalis in captivity from 19 March to 11 May, 2008 is described for the first time. A single male dominates a harem of two females, spawning with each at dusk, from 10 min before to 20 min after sunset. Each female laid an average 119 × 10³ eggs during the spawning period. Fertilized eggs were spherical, buoyant and had a diameter of 0.83 ± 0.02 mm (mean ± SD). Embryonic development lasted 15–18 h at 28.1 °C. Newly hatched larvae were 1.60 ± 0.07 mm in total length (TL) with 27 myomeres. Larvae completed yolk absorption within 3 days post hatching (ph) at 3.01 ± 0.08 mm TL. Ten days ph, the larvae had attained 3.95 ± 0.12 mm TL. Larvae were fed either 100% s‐type rotifers (Brachionus rotundiformis), 100% copepods (Microsetella sp.), a combination of the two (50%:50%) or without live feed (starved control) to determine the effect of live feed on the survival rate. The survival was significantly (P<0.001) higher in larvae fed a combination of diet than the others. These results indicate that C. septentrionalis is a potential species for captive breeding programs and the use of a combination of diet (s‐type rotifers and copepods) may be a suitable first food for the larvae.     

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.     

Different responses between orange variant and cultured population of the Pacific oyster Crassostrea gigas at early life stage to temperature‐salinity combinations

Although breeding of rare shell colour variants has drawn widespread attention from shellfish breeders, the potential disadvantages of their adaptive capacity have been ignored in practice. To explore the difference in adaptive capacity between orange shell variant (OSO) and commercially cultured population (CPO) of the Pacific oyster Crassostrea gigas at early life stage, the development to D‐larvae and larval survival and growth (just 23 and 30°C for larval experiment) of them were compared under different temperature (16, 23 and 30°C) and salinity (17, 25 and 33 psu) combinations. In this study, at 23°C and 25 psu, for both OSO and CPO there was no difference in fertilization rates and survival (p > .05) (mean percentages of D‐larvae after fertilized 40 hr ≥ 95.00%; mean larval survival rates on day 10 > 80.00%). However, the percentage of D‐larvae of CPO at 40 hr was significantly (p < .05) higher than OSO at temperatures of 16 and 30°C and 25–33 psu and 17 psu at 23°C. Similarly, CPO has a better larval survival on day 10 and growth than OSO at salinities of 17 and 33 psu at 23°C. Overall, our results indicate that OSO can have an equally good performance like CPO at early life stage under optimal condition (23°C; 25 psu), but the potential disadvantages in adaptive capacity will be shown at suboptimal conditions. These findings can guide future hatchery breeding of OSO, and suggest the potential disadvantages in adaptive capacity in rare colour variants need more attention in further breeding.     

Use of the freshwater rotifer <Emphasis Type="Italic">Brachionus angularis</Emphasis> as the first food for larvae of the Siamese fighting fish <Emphasis Type="Italic">Betta splendens</Emphasis>

Larvae of the Siamese fighting fish Betta splendens were reared on the mass-cultured small freshwater rotifer Brachionus angularis Laos strain (UTAC-Lao), Paramecia sp., and Artemia as live food sources. Larvae fed live food were found to have a significantly high survival rate (97.5–100%) 18 days after hatch (DAH) in comparison to the control unfed larvae, which died by 12 DAH. Rotifer-fed larvae were found to grow faster than paramecia-fed larvae. The fastest growth rate was observed in larvae fed a combination of rotifer and Artemia, with growth in these larvae increasing by 282% by 18 DAH [total length (TL) 11.3 ± 1.2 mm] relative to body measurements taken 3 DAH. The next fastest growth rate was observed in rotifer-fed larvae, with a 158% increase in growth observed by 18 DAH (TL 7.6 ± 0.5 mm). The paramecia-fed larvae were found to grow by only 54.3% (TL 4.6 ± 0.1 mm) during the same period.     

Effects of temperature and salinity on the survival and development of mud crab, Scylla serrata (Forsskål), larvae

The combined effects of temperature and salinity on larval survival and development of the mud crab, Scylla serrata, were investigated in the laboratory. Newly hatched larvae were reared under 20 °C temperature and salinity combinations (i.e. combinations of four temperatures 25, 28, 31, 34 °C with five salinities 15, 20, 25, 30, 35 g L⁻¹). The results showed that temperature and salinity as well as the interaction of the two parameters significantly affected the survival of zoeal larvae. Salinity at 15 g L⁻¹ resulted in no larval survival to the first crab stage, suggesting that the lower salinity tolerance limit for mud crab larvae lies somewhere between salinity 15 and 20 g L⁻¹. However, within the salinity range of 20–35 g L⁻¹, no significant effects on survival of zoeal larvae were detected (P>0.05). The combined effects of temperature and salinity on larval survival were also evident as at low salinities, both high and low temperature led to mass mortality of newly hatched larvae (e.g. 34 °C/15 g L⁻¹, 34 °C/20 g L⁻¹ and 25 °C/15 g L⁻¹ combinations). In contrast, the low temperature and high salinity combination of 25 °C/35 g L⁻¹ resulted in one of the highest survival to the megalopal stage. It was also shown that at optimal 28 °C, larvae could withstand broader salinity conditions. Temperature, salinity and their interaction also significantly affected larval development. At 34 °C, the mean larval development time to megalopa under different salinity conditions ranged from 13.5 to 18.5 days. It increased to between 20.6 and 22.6 days at 25 °C. The effects of salinity on larval development were demonstrated by the fact that for all the temperatures tested, the fastest mean development to megalopa was always recorded at the salinity of 25 g L⁻¹. However, a different trend of salinity effects was shown for megalopae as their duration consistently increased with an increase in salinity from 20 to 35 g L⁻¹. In summary, S. serrata larvae tolerate a broad range of salinity and temperature conditions. Rearing temperature 25–30 °C and salinity 20–35 g L⁻¹ generally result in reasonable survival. However, from an aquaculture point of view, a higher temperature range of 28–30 °C and a salinity range of 20–30 g L⁻¹ are recommended as it shortens the culture cycle.     

Effects of salinity and temperature during incubation on hatching and development of lingcod Ophiodon elongatus Girard, embryos

The interactive effects of salinity and temperature on development and hatching success of lingcod, Ophiodon elongatus Girard, were studied by incubating eggs at four temperatures (6, 9, 12 and 15°C) and five salinities (15, 20, 25, 30 and 35 g L^?1). Hatch did not occur in any of the 15°C treatments. Degree days (°C days) to first hatch was not influenced by temperature or salinity, however, calendar days to first hatch differed significantly for temperature (P<0.0001, 61±1, 44±1 and 35±1 days for 6, 9 and 12°C respectively). Degree days to 50% (427.1±4.2) hatch was not significantly influenced by temperature but was by salinity (P=0.0324). Viable hatch (live with no deformities, 74.1±4.0%) was greatest at 9°C and 25 g L^?1 but not significantly different in the range of 20–30 g L^?1. Larval length (9.4±0.13 mm) was greatest at 9°C and 20–30 g L^?1. Temperature and salinity significantly influenced all categories of deformities with treatments at the upper (12°C and 35 g L^?1) and lower limits (6°C and 15 g L^?1) producing the greatest deformities. The optimal temperature and salinity for incubating Puget Sound lingcod eggs was found to be 9°C and 20–30 g L^?1.     

OPTIMAL SALINITY-TEMPERATURE COMBINATIONS FOR THE EARLY LIFE STAGES OF GILTHEAD BREAM,Sparus auratus L.

High larval mortalities during rearing of gilthead bream, Sparus auratus L., led to experiments on the influence of salinity and temperature on eggs and yolk-sac larvae. Test salinities ranged from 5 to 70 ppt for eggs and from 15 to 45 ppt for larvae; experimental temperatures were 18–20°C for eggs and 18, 23 and 26°C for larvae. Spawning conditions were 18–20°C and 33–35 ppt salinity; the yolk-sac larvae were chosen from hatches obtained under similar conditions (18°C and 35 ppt salinity). For eggs the optimum survival range was found to be 30–50 ppt at 18°C and 15–60 ppt at 23°C, while that for yolk-sac larvae was 15–25 ppt at all three temperatures. Choosing normal development (no dorsal curvature) as the decisive criterion, the optimum salinity range for egg incubation was reduced to 30–40 ppt at 18°C and to 35–45 ppt at 23°C, while that for the yolk-sac stage remained 15–25 ppt at all test temperatures. Egg incubation was most successful at salinity-temperature combinations close to those during spawning, whereas salinity had to be reduced by at least 10 ppt for yolk-sac larvae.     

The effects of temperature and photoperiod on egg hatching success,egg production and population growth of the calanoid copepod,Acartia grani (Calanoida: Acartiidae)

Calanoid copepods, including species of the genus Acartia, are commonly used as larval diets for marine finfish. This study aimed to determine the separate effects of water temperature (18, 22, 24, 28° ± 0.5°C) and photoperiod (24L:0D; 18L:6D; 12L:12D; 8L:18D; 0L:24D) on Acartia grani egg production (EP), hatching rate (EHR) and population growth. Egg production rate was not affected by the two abiotic parameters. A. grani eggs incubated at T24°C and T28°C were the first to achieve 50% hatching rate (23–25 hr), with significant differences at the end of the experiment (48 hr) between T28°C treatment (EHR 88 ± 5%) and T18°C treatment (EHR 65 ± 2%). However, different temperature regimes did not affect final number of individuals in population growth experiment. Still, when eggs were excluded from data, population at lower temperatures (18°C) was mainly composed by the nauplii stage (72%), while at higher temperatures (24°C and 28°C) more than 60% of the population was composed by copepodites and adults. A. grani subjected to long‐day photoperiods had significantly lower EHR (16.7% at 24L:0D; 20.8% at 18L:6D) than at short‐day photoperiods (52.6% at 6L:18D; 50.0% at 0L:24D). In population growth experiment, eggs were the most common life stage after 12‐day culture. Lowest population number was found at constant light conditions (665.0 ± 197.1), suggesting higher metabolic rates and depletion of energy reserves in long‐day conditions. This study expanded knowledge on the biological response of A. grani to separate temperature and photoperiod regimes, and provided ground to improve the culture of this potential life feed species for hatcheries.     

GnRHa‐induced Multiple Spawns and Volition Spawning of Captive Spotted Rose Snapper,Lutjanus guttatus,at Mazatlan,Mexico

Sexual maturation and induced spawning treatments were carried out with captive spotted rose snapper, Lutjanus guttatus. A total of 3013 × 10⁶ eggs (64.7% were floating) were produced from eight treated females in 42 spawns induced with GnRHa implants during the course of the present study. GnRHa ethylene‐vinyl acetate copolymer effective doses were 204 ± 11 µg/kg in June 2005, and 224 ± 13 µg/kg in July 2005. General fertilization was 50.9 ± 34.5% and 12–14 h after spawning, viability of floating eggs was 90.4 ± 12.4%. Mean incubation period at 29–31 C was 18–20 h, and mean hatching was 94.4 ± 8.2% (73–100%). Newly hatched larvae were 2.18 ± 0.15 mm in total length (TL). One month after the last hormone experiment, previously GnRHa‐treated and untreated fish began spawning voluntarily. Hormone‐treated breeders had higher fecundity than untreated fish, producing 72.5 million eggs versus 13.9 million eggs for the untreated fish, over the following 11 mo. Combined data of volitional spawning for total egg fertilization, viability, hatching, and larval TL were 77.7 ± 1.8%, 90.3 ± 1.3%, 87.9 ± 2%, and 2.50 ± 0.12 mm, respectively. These results can ensure the sustainability of a commercial hatchery.     

Effect of stocking density and feeding regime on larval growth,survival, and larval development of Japanese flounder,Paralichthys olivaceus,using live feeds

This research examined the effect of initial stocking density and feeding regime on larval growth and survival of Japanese flounder, Paralichthys olivaceus. Larval rearing trials were conducted in nine 50‐L tanks with different initial stocking densities combined with different feed rations (20 larvae/L with standard feed ration [LD], 80 larvae/L with standard feed ration [HD], and 80 larvae/L with four times the standard feed ration [HD+]). Larvae were stocked on 0 days posthatch (DPH) following hatching of the fertilized embryos. Larval total length (TL), survival rates, and final densities were observed on larval settlement (32 DPH) to evaluate larval rearing performance. At 32 DPH, there were no significant differences (p > .05) in TL or survival rates between the LD (46.5 ± 17.0%) and HD+ (40.3 ± 9.4%). The TL and survival rate of HD (23.1 ± 3.5%) were significantly lower than that of LD and HD+ (p < .05). However, the larval density of HD was significantly higher than that of LD (p < .05). HD+ achieved the best larvae production (32.27 ± 7.51 larvae/L), supported by sufficient food source, high water exchange, and proper water quality management (routine siphoning, surface skimming). The larval‐rearing protocols and larval development from hatching to metamorphosis is described in detail, with corresponding photographs taken during the experiment.     

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.     

Effect of increasing docosahexaenoic acid content in weaning diets on survival,growth and skeletal anomalies of longfin yellowtail (Seriola rivoliana,Valenciennes 1833)

Five isoproteic (54.8%) and isolipidic (24.1%) microdiets, which varied in their docosahexaenoic acid (DHA) content (0.25%, 0.75%, 1.64%, 1.99% and 3.17%; dw), were manufactured to determine its effects on longfin yellowtail Seriola rivoliana larvae in terms of fish biological performance, whole body fatty acid profile and incidence of skeletal anomalies from 30 dah (11.31 ± 1.79 Total Length, TL) to 50 dah (19.80 ± 0.58 mm TL). The inclusion of dietary DHA up to 3.17% (dw) improved larval resistance to air exposure, although DHA did not significantly affect fish final growth or final survival. Indeed, high levels of dietary DHA (1.99% and 3.17%, dw) tended to increase the incidence of skeletal anomalies in S. rivoliana larvae, albeit no significant differences were observed. Furthermore, the occurrence of severe anomalies such as kyphosis and lordosis, was mainly associated to the larvae fed the highest levels of dietary DHA. In terms of survival, increasing dietary DHA levels did not significantly affect longfin yellowtail survival rate, despite a tendency for enhanced survival. The results of the present study proved that the inclusion of dietary DHA in inert diets up to a 3.17% (dw) and a DHA/EPA ratio above 3.1 increased the final survival and stress resistance in S. rivoliana larvae.     

Effect of dietary lipid level on growth,lipid metabolism and health status of the Pacific white shrimp Litopenaeus vannamei at two salinities

Three isonitrogenous diets containing 60 g kg^–1, 90 g kg^–1 or 120 g kg^–1 lipid were formulated and fed to the Litopenaeus vannamei (2.00 ± 0.08 g) under two salinities (25 or 3 psu) in triplicate for 8 weeks. Shrimp fed 90 g kg^–1 lipid had higher weight gain and specific growth rate than shrimp fed the other two diets regardless of salinity, and the hepatosomatic index increased with increasing dietary lipid at both salinities. The shrimp at 3 psu had significantly lower survival and ash content, higher condition factor, weight gain and specific growth rate than the shrimp at 25 psu. Increasing dietary lipid level induced the accumulation of serum MDA regardless of salinity, and at 3 psu, it reduced the serum GOT and GPT activities and the mRNA expression of TNF‐α in intestine and gill of L. vannamei. The hepatopancreatic triacylglycerol lipase (TGL) and CPT‐1 mRNA expression showed the highest value in shrimp fed 90 g kg^–1 lipid diet at 3 psu. This study indicates that 120 g kg^–1 dietary lipid may negatively affect the growth and induce oxidative damage in shrimp, but can improve immune defence at low salinity; 60 g kg^–1 dietary lipid cannot afford the growth and either has no positive impact on the immunology for L. vannamei at 3 psu.     

Effects of commonly used disinfectants on bacterial load,hatchability and survival of Bluefin Sea bream (Sparidentex hasta) eggs

The efficacy of four chemical reagents, iodophor, formalin, hydrogen peroxide and bronopol as fish egg surface disinfectants were evaluated in bluefin sea bream (Sparidentex hasta). Fertilized eggs were counted and subjected to a static bath dip treatment in different concentrations of the above chemicals for 4 min before being incubated at 20 ± 0.5°C for 40 h. Treatment efficacy of the different disinfectants was evaluated by assessing the bactericidal activity, egg hatch percentage and survival of larvae up to 3 days post hatch. Results showed that iodophor at medium concentrations (75 and 100 ppm) was the best of all tested disinfectants in bacterial killing ability (12% reduction in the bacterial counts), egg hatching per cent (99.8% and 99.6% respectively) and larval survival up to 3 days post hatch (50.8% and 54.8% respectively). Formalin was the second best disinfectant at levels of 100 and 150 ppm. Hydrogen peroxide gave good results compared with the control while, bronopol showed discouraging results. In conclusion, iodophor appeared to be suitable for bluefin sea bream eggs disinfection with a 4 min exposure to 75–100 ppm when applied 14–16 h after egg fertilization.     

Interspecific variations in age and size at settlement of 8 emperor fishes (Lethrinidae) at the southern Ryukyu Islands,Japan

Molecular and otolith analyses were conducted for 173 settlement-stage larvae of emperor fishes (family Lethrinidae) collected by light traps at Ishigaki Island, southern Japan, in July and August (summer season), to (1) present diagnostic DNA markers for identification of lethrinid species and (2) compare the size and age at settlement of each species. PCR–RFLP and direct nucleotide sequencing analyses identified 8 species. Size (standard length, SL) at settlement differed significantly between species; Lethrinus ornatus (mean SL ± SD, 12.8 ± 1.5 mm), L. obsoletus (14.2 ± 0.8 mm) and L. harak (15.8 ± 1.6 mm) settled at a smaller size than L. atkinsoni (17.0 ± 1.3 mm), L. genivittatus (17.3 ± 1.0 mm), L. olivaceus (18.1 ± 0.6 mm), L. nebulosus (18.6 ± 4.2 mm), and L. sp.2 reported by Lo Galbo et al. (J Mol Evol 54:754–762, 2002) (21.7 ± 1.4 mm). Age at settlement tends to increase with settlement size; L. obsoletus (mean age ± SD, 25.6 ± 1.2 days), L. atkinsoni (26.1 ± 2.1 days) and L. ornatus (26.3 ± 2.9 days) were younger at settlement than L. nebulosus (28.4 ± 2.1 days), L. harak (29.2 ± 1.7 days), L. olivaceus (29.5 ± 1.0 days), L. genivittatus (30.5 ± 1.7 days) and L. sp.2 (31.0 ± 2.0 days). Although our study showed interspecific variation in body size and age at settlement among 8 lethrinid species, further seasonal replication is necessary to clarify the general patterns.     

Cranial osteological development and abnormalities in northern palm ruff,Seriolella violacea (Guichenot, 1848), larvae and juveniles

Seriolella violacea, a new species to be potentially farmed in Chile and Peru, has shown cranial malformations during farming that could adversely affect its commercial development. This study seeks to generate early knowledge of the osteological development and type of cranial abnormalities that this species presents under culture conditions. Larvae from wild caught broodstock were reared from 1 to 60 days post hatching (DPH) (4.8 ± 0.1 mm TL and 11.8 ± 1.0 mm TL respectively). Larvae samples were collected throughout the experimental trial for recording cranial osteological development and abnormalities in cartilage and bone. At 5.7 ± 0.1 mm TL, coraco‐scapular, sclerotic, ethmoid plate and quadrate cartilages were present. At 8.0 ± 0.6 mm TL, early ossification was observed in the jaw, premaxilla and maxilla. At 11.8 ± 1.0 mm TL, the branchiostegal rays, jaw, maxilla and opercular complex were ossified. The first cartilaginous structures observed were the Meckel's cartilage, the branchial arches and the suspensory ligament. The first cranial malformations were detected at 5.7 ± 0.1 mm TL, coinciding with mouth opening. The most frequent malformations were a curvature of the lower jaw (23.1%), abnormal separation between branchial arches and the Meckel's cartilage (19.4%) and bulging jaws (15.7%).