Identification of juvenile abalone <Emphasis Type="Italic">Haliotis diversicolor</Emphasis> based on number of open and sealed respiratory pores

ABSTRACT:   Changes in the number of respiratory pores (open pores) and their imprints (sealed pores) in post-larvae and juveniles were observed and compared for four abalone species Haliotis diversicolor , H. discus discus , H. madaka , and H. gigantea . The first open pore was evident at a shell length (SL) of 1.5 mm in H. diversicolor , 1.9–2.0 mm SL in H. discus discus , and 2.3–2.4 mm SL in H. madaka and H. gigantea . The number of open pores in H. diversicolor gradually increased with growth, with four to five pores at 2.5–18.0 mm SL and five to six pores at 18.0–27.0 mm SL. The other three species maintained four to five open pores after they reached 3.4–4.5 mm SL. The total number of open and sealed pores (TNP) was greater in H. diversicolor than in the other species at the same SL. Juvenile H. diversicolor were identified among field-caught abalone by the difference in the relationship between SL and TNP (SL–TNP relationship) and also by the monoclonal antibody reaction method. The results of the two methods were in perfect agreement, indicating that our method using the SL–TNP relationship is reliable for the identification of H. diversicolor .     

Effects of Food and Temperature on Survival and Development in the Peppermint Shrimp Lysmata wurdemanni

Abstract— The effects of four kinds of foods ( Artemia nauplii, rotifer, and microalgae Chaetoceros gracilis and Isochrysis galbana ) and four temperature regimes on survival and development of larval Lysmata wurdemanni , a marine ornamental shrimp, were determined. The larvae fed with Chaetoceros or Isochrysis only survived for a maximum of 17 d, before developing to zoea IV. The survivorship of the larvae fed with Artemia nauplii or rotifer from zoea II to post-larvae was 66.7% and 68.9%. respectively, without significant difference ( P > 0.05). But larvae fed with Artemia nauplii grew significantly ( P < 0.05) faster than those fed with rotifer. Larvae fed with Artemia nauplii reached postlarvae in 29–32 d, compared with 32–36 d in the rotifer treatment. Artemia nauplii are also suitable food for the postlarvae and juveniles of L. wurdemanni . The 30 postlarvae fed on Artemia nauplii all survived to reach sexual maturity in 50 to 70 d, growing from about 7 to 28 mm in total length. The effects of four temperature regimes on larval development of L. wurdemanni was also investigated. The duration (mean ± SD d) to the postlarvae at temperatures of 26 C (37.4 ± 5.4) and of 26–30 C daily (40.2 ± 5.8) was significantly ( P < 0.05) longer than that at 28.5 C (29.3 ± 4.8) and at 27–29 C daily (28.7 ± 3.5).     

Growth and ontogenetic migration of greeneye Chlorophthalmus albatrossis in Tosa Bay, Pacific Coast of South-Western Japan

ABSTRACT:   Growth and ontogenetic migration of greeneye Chlorophthalmus albatrossis were studied in the area from 100–400 m depths in Tosa Bay, from April 1996 to March 1997, using samples collected by an otter trawl net with a 1.3 mm mesh cod end. In the monthly changes of the standard length (SL) composition, four year classes were recognized, although the third- and fourth-year classes were not clearly separated in all the monthly samples. Individuals of 40–50 mm SL settled on the bottom of the 150–200 m depth zone from August to February. By May and June, they grew to 75–80 mm SL modal size, and migrated to 200–300 m depth. In one year after settlement, they grew to 125–130 mm SL, and migrated to 300–350 m depth. They grew to a maximum of 160 mm SL and were not sampled in the winter three years after settlement, suggesting either migration or mortality. Seasonal changes in the gonadosomatic index for combined samples of males and females showed that greeneye did not mature in Tosa Bay. It is suggested that the planktonic larvae are transported from the spawning grounds, the location of which remains unknown.     

山东南部皱纹盘鲍工厂化养殖试验研究

报道了山东南部皱纹盘鲍（HaliotisdiscushannaiIno）工厂化养殖试验研究的结果。自1995年1月19日至1996年5月19日，经16个月的培育，将平均壳长21．4mm，平均体重0．99g的幼的培育成平均壳长61．9mm（最大壳长72．0mm），平均体重28.5g的成鲍，成活率为93．2％。0．3m2的波纹权的养殖密度：鲍壳长为20．0～30．0mm时，养殖密度200～250粒为好；40．0mm以前，养殖密度150粒为宜；60．0mm以前，养殖密度50～80粒为佳。饵料以人工配合饵料为好。在鲍壳长40．0mm以前，在投喂人工配合饵料的同时，加上适量的新鲜海藻可以达到同样的增长和增重的目的。全投喂海藻增长和增重都较慢。     

Effects of ontogeny, temperature, and light on vertical movements of larval Pacific cod (Gadus macrocephalus)

The role of behavior, especially vertical migration, is recognized as a critical component of realistic models of larval fish dispersion. Unfortunately, our understanding of these behaviors lags well behind our ability to construct three-dimensional flow-field models. Previous field studies of vertical behavior of larval Pacific cod ( Gadus macrocephalus ) were limited to small, preflexion stages (≤11 mm SL) in a narrow range of thermal conditions. To develop a more complete picture of larval behavior, we examined the effects of ontogeny, temperature, and light on vertical responses of larval Pacific cod in experimental columns. While eggs were strictly demersal, yolk-sac larvae displayed a strong surface orientation as early as 1 day post hatch (∼ 5 mm SL). Consistent with field observations, small preflexion larvae (<10 mm SL) showed no response to varying light levels. However, there was a direct effect of temperature on larval behavior: Pacific cod larvae exhibited a stronger surface orientation at 4°C than at 8°C. The behavior of larger, postflexion larvae (>15 mm SL) in experimental columns was consistent with a diel vertical migration and independent of water temperature: fish were more widely distributed in the column, and median positions were consistently deeper at higher light levels. These laboratory observations are combined with observations from discrete-depth (MOCNESS) sampling in the Gulf of Alaska to characterize the vertical distribution of larval Pacific cod and contrast ontogenetic patterns with walleye pollock ( Theragra chalcogramma ). The vertical movements of larval Pacific cod described here will be applied in the development of dispersal projections from Gulf of Alaska spawning grounds.     

Culture of larvae of the white mullet,Mugil curema Valenciennes

Planktonic eggs of the white mullet, Mugil curema, were collected in Biscayne Bay, Florida, and the larvae were reared in four laboratory experiments. Static rearing systems were used and copepod nauplii and copepodites were fed to larvae. Larvae grew from 2.1 mm standard length (SL) at hatching to 28.5 mm SL (35.9 mm total length) at 36 days after hatching. No significant mortalities occurred beyond 12 days after hatching. At 20 days, survival ranged from 1.2 to 23.0%. Most larval mortality occurred when larvae sank to the bottom of the rearing tanks, a phenomenon previously reported for striped mullet, Mugil cephalus. Successful culture of white mullet could have potential for meeting the demands of the live bait market for recreational fishing in south Florida.     

Effect of starvation on the growth and survival of post-larval abalone (Haliotis iris)

The starvation tolerance of post-larval abalone (Haliotis iris) was determined by examining post-larval growth and survival after various periods of starvation. Competent larvae (10 days old at 16°C) were induced to attach and metamorphose with 2 μM GABA. Post-larvae were either fed diatoms (Nitzschia longissima) or starved. In Experiment 1, post-larvae were starved immediately after metamorphosis for periods of 1, 2, 4, 8, 15, 20, 25 and 30 days. Starved post-larvae grew relatively well for several days after metamorphosis despite the absence of food (averages of 10.4 and 17.8 μm shell length (SL) per day after 8 days for two batches). Subsequent growth was minimal, averaging 1.7 and 0.7 μm day⁻¹ over 6–7 days for the two batches. There was no clear relationship between period of starvation and growth rate when fed. Mean daily growth rate over 3 weeks when fed ranged from 15–22 μm day⁻¹. However, the duration of starvation did have a significant effect on survival. Survival of post-larvae fed after 1–2 days of starvation was 90–100% after 3 weeks of feeding. Longer starvation periods gave progressively lower survival and post-larvae starved for 30 days all died within a week of being fed. In Experiment 2, post larvae were fed for 3 weeks after metamorphosis, then starved for 0, 3, 7, 14 or 21 days. Growth rates of starved post-larvae averaged only 5–6 μm day⁻¹ in the first week (vs. 30 μm day⁻¹ in controls), and later declined to zero. Growth resumed within a week following return to food, but the 14- and 21-day starvation treatments took 2 weeks to reach growth rates comparable to controls. The no-starvation controls and the 3- and 7-day starvation treatments all had >70% survival over 4 weeks after return to food. Survival in the 14- and 21-day starvation treatments was 15–20%, with almost all mortalities occurring in the first week after return to food. These data suggest that Haliotis iris post-larvae are relatively tolerant of starvation, so abalone farmers have a week or so to remedy food shortages before major post-larval mortality begins.     

Size-dependent predation on marine fish larvae by Ctenophores, Scyphomedusae, and Planktivorous fish

Size-dependent predation rates on marine fish larvae by the ctenophore Mnemiopsis leidyi , scyphomedusa Chrysaora quinquecirrha , and planktivorous fish Anchoa mitchilli were estimated via experiments in 3.2 m³ me-socosms. Predation rates on larvae of the goby Gobio-soma bosci were estimated in relation to 1) length of larval prey, 2) presence or absence of alternative < 1 mm zooplankton prey, and 3) a predator-prey interaction between the scyphomedusa and ctenophore. The consumption rate of larvae by the three predators generally declined as larval length increased. The ctenophore ate fewer (1.0 d^-1 per predator) larvae than did the medusa (7.8 d ^-1 per predator) or bay anchovy (4.0 d ^-1 per predator), but it consumed larvae in all size classes tested (3.0–9.5 mm SL). Predation by bay anchovy and the medusa was more size-dependent: 3.0–5.0 mm larvae were most vulnerable. Fewer larvae were eaten by the ctenophore and bay anchovy when zooplankton alternative prey was available, but predation on larvae by the medusa was not influenced by alternative zooplankton prey. Consumption rate of fish larvae by the medusa was reduced 20–25% when the ctenophore was present as its alternative prey. An encounter-rate model was developed and its parameters estimated from the experimental results. Model simulations indicated that the relationship between larval size and vulnerability is dependent on size, swimming speed, and behavior of both predators and larvae, and that bigger or faster-growing fish larvae are not always less vulnerable to predation.     

Ecological significances of ontogenetic shifts in the stream-dwelling catfish, Hatcheria macraei (Siluriformes, Trichomycteridae), in a Patagonian river

Abstract –  The relationship between ontogenetic changes and both feeding and habitat preferences was studied in a stream catfish population of Argentine Patagonia. Fish capture, as well as habitat data recording, was performed during a 1-year long period. Larvae–juvenile transition was determined between 22.4 and 29.4 mm standard length (SL), on the basis of the relative growth changes and morphogenesis, and juvenile–adult shift was established between 61 and 65 mm SL using a macroscopic criterion of gonadal development and gonadosomatic index. Spawning period was estimated to be in the summer season, from December to February. Larvae preferred shallow marginal pools and fed mainly on small Chironomidae larvae, while juveniles and adults inhabited riffles and preyed on Ephemeroptera nymphs and Chironomid larvae. Morphological constraints during the larval period were related to habitat and feeding preferences. A complete development of fins allowed juveniles to colonise faster water habitats while a bigger mouth gape permitted them to prey on new items and on a larger size prey range.     

中国沿海九种头足类齿舌的形态学

采用扫描电镜技术对9种头足类的齿舌进行了显微观察和比较研究。结果显示所研究的物种的齿舌均有7列纵向的齿组成,齿式为3·1·3。乌贼目的7个种(罗氏乌贼Sepiarobsoni、金乌贼S.esculenta、虎斑乌贼S..pharaonis、白斑乌贼S.latimanus、目乌贼S.aculeata、曼氏无针乌贼Sepiellamaindroni、柏氏四盘耳乌贼Euprymnaberryi)中央齿一列,具有一个齿尖;侧齿位于中央齿两侧各3列,分别称为第一、第二和第三侧齿,也称为侧齿,内缘齿和外缘齿;无缘板结构。长蛸Octopusvariabilis和短蛸O.ocellatus中央齿一列,分别有5个、3和5个齿尖,侧齿各3列,具有缘板。文中对九个种的齿舌结构以及彼此的异同进行了详细的描述和比较,并对乌贼类、蛸类和枪乌贼类彼此之间的齿舌关系以及功能差异进行了讨论。     

Dietary value of gametophytes and juvenile sporophytes of the brown macroalga <Emphasis Type="Italic">Eisenia bicyclis</Emphasis> for juvenile abalone <Emphasis Type="Italic">Haliotis diversicolor</Emphasis>

The dietary value of juvenile stages (gametophyte and juvenile sporophyte) of the brown macroalga Eisenia bicyclis for post-larval and juvenile abalone Haliotis diversicolor of 2.0–6.5 mm in shell length (SL) was examined and compared with that of a benthic diatom, Nitzschia sp., in laboratory experiments. Most abalone actively fed on these diets, but there were large variations in the growth rate among the diets and among the growth stages of abalone. Growth rates of abalone fed on Nitzschia sp. were highly variable within each growth stage, but showed no clear differences among growth stages. In contrast, in abalone fed gametophytes or juvenile sporophytes, growth rates linearly increased as abalone grew. Growth rates of >60 μm SL/day were observed in juveniles of >3 mm SL fed gametophytes, and juveniles of >5 mm SL fed juvenile sporophytes. These results indicate that the dietary value of the juvenile stages of E. bicyclis for the abalone changes as they grow, and with growth juvenile abalone begin to efficiently utilize gametophytes and juvenile sporophytes in that order.     

Observations on larval fish transport and retention on the Scotian Shelf in relation to geostrophic circulation

We draw inferences about the dynamic processes responsible for the dispersal of ichthyoplankton on small marine banks using physical and biological data derived from static point-estimates of water-mass characteristics and ichthyoplankton collected concomitantly on the central Scotian Shelf. Where the density field evolves slowly and ageostrophic forcing is weak, the near-surface geostrophic flow can be derived from hydrographic data using the dynamic height method modified for shallow seas. We assess our interpretations of larval distributions using simple particle tracking. The hydrography of the Scotian Shelf during November of 1997 was typical of late autumn, when density is determined by surface variation in salinity. Surface isopycnals generally paralleled isobaths, and there was no evidence of strong surface fronts. Sizes of larvae of pelagic origin (e.g. cod and hake) on Western Bank (sole spawning source) increased and became skewed towards larger animals (cod, 3–10 mm; hake, 5–15 mm) in water-mass (Temperature and Salinity) space along isopycnals, consistent with gradual mixing and limited transport in the geostrophic flow (i.e. retention). Conversely, larvae of benthic origin (e.g. herring, 6–25 mm) were distributed across water-mass space, consistent with multiple origins and substantial transport. Our results indicate that dispersal from small, low-energy marine banks results from the interaction of spawning location, geostrophic currents and bathymetric steering, and requires neither convergence nor larval behaviour.     

Morphoecology in larval fin-fish: a new candidate species for aquaculture, Diplodus puntazzo (Sparidae)

This study was aimed to acquire information ontrophic behavior of Diplodus puntazzolarvae and juveniles, by studing theontogenetic sensory development, except vision.D. puntazzo specimens were observed usinga scanning electron (n = 67) and a lightmicroscope (n = 7). The results concerned fourontogenetical stages of sharpsnout seabream:larval, post-larval, transitional, and juvenilestages. The yolk-sac larval stage was notdetected as the smallest larvae at our disposal(3.1 mm TL; 2nd day from hatching) showedno external appearance of the yolk. During thelarval stage (3.1–4.7 mm TL), sharpsnoutseabream is equipped with free neuromasts andolfactory ciliated receptor cells. In thepost-larval stage (5–28.6 mm TL), mechano- andchemo-reception is implemented: the inner andouter taste buds differentiation, the nasalformation, the lateral line system canalizationoccur. The precocious differentiation ofchemo-receptors makes post-larvae particularlysensitive to the organoleptic properties ofadministered preys. D. puntazzo, at theend of this phase, could be considered ajuvenile (complete squamation is acquired),except for the mouth and pharyngeal teeth.During the subsequent phase (`transitional'),in fact, eight chisel-type and two lateralseries of molar-like teeth progressivelysubstituted the conical ones on each jaw, andthree different types of teeth on the upper andlower pharynx differentiated. So, the juvenilephase is reached in individuals longer than58 mm TL.     

Dietary value of benthic diatoms for post-larval abalone <Emphasis Type="Italic">Haliotis diversicolor</Emphasis> associated with feeding transitions

ABSTRACT:   The feeding behavior and growth of post-larval Haliotis diversicolor with initial shell lengths (SL) of approximately 500 μm (Exp. 1-1 and 1-2), 800 μm (Exp. 2), and 1200 μm (Exp. 3) were studied in a laboratory setting while they fed on four species of benthic diatom Achnanthes longipes , Cocconeis sublittoralis , Cylindrotheca closterium , and Navicula ramosissima . Exp. 1-1 and 1-2 revealed no marked differences in post-larval growth rates (mean 24–39 μm SL/day) among the diatom species. However, marked differences in growth rates among the species were revealed in Exp. 2 and 3. Three species, A. longipes , Co. sublittoralis, and Cy. closterium , produced faster growth (Exp. 2 mean 29–51 μm/day, Exp. 3 mean 36–44 μm/day) than N. ramosissima (Exp. 2 mean 18 μm/day, Exp. 3 mean 23 μm/day). Post-larvae fed N. ramosissima had lower digestion efficiency (42.8%) than those fed other diatom species (90.7–100%). Diatom extracellular substances appeared to be principally used from post-settlement to 800 μm SL, and diatom cell contents were required to produce rapid growth of larger post-larvae (>800 μm SL). It is likely that the availability of each diatom for post-larvae was affected by diatom morphology, attachment strength, frustule strength, and post-larval size.     

Preservation-induced changes in morphometrics of fishes: influence on prey size-choice in juvenile walleye, Stizostedion vitreum (Mitchill)

Abstract– Juveniles of the Gulf coast population of walleye, Stizostedion vitreum , 22.4–89.9 mm SL ( n =111) shrank significantly in SL and throat diameter over 12 months after being fixed in 10% formalin for 1 week and preserved in 50% isopropyl alcohol thereafter. Significant changes in body depth and total length (TL) were also determined for select larval fish prey that juvenile walleye might encounter in nature. The relationship between fresh SL and throat diameter in juveniles of the Gulf coast population of walleye (22.4–172.4 mm SL) is: throat diameter (mm) =−0.8783 + 0.0786 SL (mm) ( r ²= 0.988, P < 0.0001, n = 135). In laboratory experiments on prey size choice, walleye selected available prey near or less than their mean throat diameter, although several larger prey (7.4% of total) were also consumed. To determine the actual spectrum of prey sizes available to juvenile piscivores, we must adjust the realized size of the predator and prey for changes caused by preservation. Preservation-induced alterations in morphology translated into errors in the perceived pattern of prey size choice in walleye. The preservation-induced changes documented in this study, which are also supported by a number of other empirical data sets, must be included when modeling the relationships between feeding ecology, morphology, growth, and ecologically relevant indices (condition factors, relative weights, etc.).     

Size-related changes in habitat selection by larval grayling (Thymallus thymallus L.)

Abstract  – In a medium-sized river in northern Finland, larval grayling shifted with growth from shallow habitats with slow velocities, fine substrata and abundant vegetation cover to deeper sites with swifter velocities, coarse substrata and sparse vegetation cover within 3 weeks. Small (17–21 mm) larvae preferred water depths 10–30 cm, substrata dominated by mud or sand (<2 mm), 10–70% vegetation cover and water velocities <10 cm · s⁻¹. Middle-sized (22–25 mm) larvae preferred 30–90 cm depths, sandy substrata, <40% vegetation cover and velocities <10 cm · s⁻¹. Large (26–31 mm) larvae preferred >50 cm depths, substrata dominated by sand or boulders, <20% vegetation cover and 10–50 cm · s⁻¹ velocities. The strict habitat requirements of the smallest larval group suggest that these habitats, in particular, are important to the early survival of grayling.     

Implications of larval diet concentration on post-larval yield in a production scale flow-through system for scallops (Pecten maximus Lamarck) in Norway

In order to optimize Pecten maximus larval performance and post-larval yield, larvae were fed five algal concentrations in the range 3–20 cells μL^?1 in 2,800-L flow-through tanks without prophylactic antibiotics. Competent larvae were transferred to a commercial hatchery for settlement and provided uniform conditions for 4 weeks to observe effects. Increased diet concentration increased the sum of fatty acids (FA) in the total larval population, reaching 7 and 25 ng FA larvae^?1 at 3 and 16 cells μL^?1, respectively. The FA level in competent larvae was not affected by diet concentration and ranged from 30 to 46 ng larvae^?1. Increased diet concentration increased larval growth rate, and the larvae were ready to settle 5 days earlier when fed 16 cells μL^?1 compared to 3 cells μL^?1. Larval ingestion rate increased during life span and with increased larval diet concentrations, but a considerable amount (40–60 %) of the added algal cells was lost from the larval rearing tanks due to the seawater flow. There was no effect on larval survival, final post-larval shell height, % of competent larvae transferred to settlement, or total yield of post-larvae. Final mean post-larval shell height was 509 μm and 25.5 % of competent larvae settled, resulting in a final post-larval yield between 6.9 and 17.6 % of the initial number of d3 larvae. Competent larvae with similar FA content produced similar numbers of post-larvae independent of diet concentration, even if higher diet concentrations resulted in higher rates of larval development and metamorphosis.     

Diet shift of larval and juvenile landlocked Ryukyu-ayu <Emphasis Type="Italic">Plecoglossus altivelis ryukyuensis</Emphasis> in the Fukuji Reservoir,Okinawa Island,Japan

ABSTRACT:   The diet shift of larval and juvenile Ryukyu-ayu Plecoglossus altivelis ryukyuensis was investigated for the landlocked population stocked in the Fukuji Reservoir, Okinawa Island. Gut contents of 274 specimens (5.1–31.4 mm in body length) including 31 yolk-sac larvae (5.7–8.0 mm) were examined. The diet of larval and juvenile landlocked P. a. ryukyuensis was mainly composed of zooplankton such as dinoflagellates, rotifers, copepods, and cladocerans. Feeding incidence was 48% in total and it gradually increased with growth. Diet analysis clearly demonstrated a diet shift during the larval and juvenile periods. For yolk-sac larvae and 5.0–19.9 mm fish, the diet was dominated by dinoflagellates Gymnodinium sp., and Peridinium sp., both numerically and by frequency, followed by rotifers that mainly consisted of Polyarthra spp. Diet breadth (Levin's standardized index B_A) diversified with growth, and feeding on copepods and cladocerans gradually increased in 10.0–14.9 mm fish. Diet overlap (Morisita's index: C) showed that diet drastically changed in 20.0–24.9 mm fish with a specialization on cladocerans Bosminopsis deitersi and Diaphanosoma brachyurum . This diet shift probably corresponded with an increase of feeding ability resulting from an enlargement of the mouth, increased swimming ability, and the development of sense organs.     

Ontogeny of anti-predator behavior in hatchery-reared jack mackerel Trachurus japonicus larvae and juveniles: patchiness formation, swimming capability, and interaction with jellyfish

ABSTRACT:   Laboratory rearing and behavioral observations of larval and juvenile jack mackerel Trachurus japonicus were conducted to elucidate their life-history traits with emphasis on the interaction with the moon jellyfish Aurelia aurita . Jack mackerel were raised from naturally spawned fertilized eggs and they attained 10.3 ± 0.7 (mean ± standard deviation) mm in body length (BL) by 30 days post hatching (dph) and 26.6 ± 1.8 mm BL at 48 dph raised at 19.3–25.0°C. Patchiness (dense aggregation) was confirmed from 5–16 dph (2.9–5.9 mm BL) during the day and from 9–48 dph (4.0–27 mm BL) at night. Cruise and burst swimming speeds were 1.5–1.9 BL/s and 16–24 BL/s, respectively, during larval and juvenile stages, in experimental tanks. Although escape performance from jellyfish was not different between the larvae of jack mackerel and chub mackerel Scomber japonicus , both species showed better survival compared to red sea bream Pagrus major larvae of a similar size. Although jack mackerel were slow in growth, their slow cruise swimming may reduce the chance of encountering predators and fast burst swimming may help escape from gelatinous predators.     

Effect of nitrite on larval development of giant river prawn Macrobrachium rosenbergii

The effects of ambient nitrite concentrations on larval development of giant river prawn Macrobrachium rosenbergii were evaluated. The trials were conducted in two phases: phase 1, larvae from stages I through VIII and phase 2, larvae from stage VIII until post-larvae. In both phases larvae were kept in water with nitrite (NO₂-N) concentrations of 0, 2, 4, 8 and 16 mg/L. Oxygen consumption was analyzed for larvae in stage II at nitrite concentrations of 0, 4, and 8 mg/L. Survival, weight gain, larval stage index and metamorphosis rate decreased linearly with increasing ambient nitrite concentration. However, there was no significant difference between larvae subjected to 0 and 2 mg/L NO₂-N. In phase 1, there was total mortality at 16 mg/L NO₂-N, while in phase 2 larval development stopped at stage X in this treatment. The oxygen consumption in stage II increased significantly at NO₂-N concentration from 0 to 4 mg/L, but there was no difference between 4 and 8 mg/L NO₂-N. In conclusion, increasing ambient nitrite up to 16 mg/L NO₂-N delays larval development, reduces larval growth rate and causes mortality, whereas no significant effect occurs for levels below 2 mg/L NO₂-N. However, the establishment of a general safe level of nitrite to M. rosenbergii hatchery may be difficult due to the great variability in larvae individual sensitivity.