Fish larvae association in a Mexican Caribbean bay

Interannual ichthyoplankton variation, was analyzed in Bahía de la Ascensión, Mexico, during December of four consecutive years (1994-1997). A total of 32 families, 35 genera and 21 species of fish larvae were identified. The most abundant fish larvae were the Gobiidae followed by the Callionymidae, Clupeidae and Tetraodontidae. Larval diversity was low when compared with other periods ("dry" and "rainy"). Three spatial associations (internal, medium and external) were found in December 1994 and 1995. In 1996-1997, stations of the inner and outer parts of the bay were mixed. The dominant families characterized most of the faunal associations. Egg density was highest in the external zone of the bay, whereas larvae were most abundant in the inner area. Major factors affecting the fish larval assemblages during December (1994-1997) in Bahía de la Ascensión seem to be related to the nursery areas location and to the tropical fishes reproductive period.     

Occurrence of Gobiidae larvae in a tropical Brazilian estuary,with particular emphasis on the use of size classes to categorize species guilds

The structure and seasonal dynamics of larvae of the Gobiidae family in the Mucuri Estuary (Bahia, Brazil) were studied for nine consecutive years. Sampling was conducted at three stations in the lower estuary channel, between 2002 and 2010, in relation to season, day and night and tidal variations. A total of 5802 Gobiidae larvae, representing 15 taxa (12 species and three morphotypes), were collected in the Mucuri Estuary during this time. The highest mean ± s.d. density of fish larvae, 54·7 ± 79·8 larvae 100 m^?3, was recorded during the flood tide and night sampling. Ctenogobius boleosoma was the most abundant species (68%), being dominant in the rainy and dry seasons and had a long reproductive period. This species was classed as a marine estuarine‐opportunist because it was observed at high frequencies and active larvae entering the estuary between 6·1 and 12·0 mm standard length (L_S). Gobionellus oceanicus, second in abundance (12%), occurred only in later larval stages but did not use the estuary as a preferred location for spawning, being classed a marine estuarine dependent. Microgobius carri (11%) was represented in all L_S classes and was resident in the estuary for spawning, remaining there throughout their life cycle. The other species were considered rare due to their low densities and could not be classified in any guild.     

Community structure and temporal variability of ichthyoplankton in North Brazilian mangrove creeks

The species composition and dynamics of fish larvae in three mangrove creeks located in the Caeté Estuary (north Brazil) were studied monthly using a trap net during diurnal ebb tides. A total of 109 954 larvae, representing 25 families and 54 species, were collected from October 1996 to October 1997. The community was dominated numerically by a few species, a feature common for other estuarine fish populations. The most abundant taxa were estuarine species, namely the eleotrid Guavina guavina (46·7%) and the engraulid Anchovia clupeoides (14·9%). The sciaenid Cynoscion acoupa was the only marine species that used the mangroves extensively as a nursery site, occurring mainly at the postflexion stage. The size distribution of G. guavina did not produce shifting modes, indicating continuous transport out of the mangroves by tidal currents. Significantly lower species richness was observed in the late rainy season, primarily due to the emigration of marine species. Intermediate seasons were characterized by more complex larval fish assemblages. The temporal trends of the dominant species was influenced to a great degree by their life history strategy.     

Comparison of inshore and offshore fish larval assemblages within the wider Yangtze River estuary (China)

It is hypothesized that fish larvae undertake vertical movements in estuarine waters. To test this hypothesis, a sampling period was selected during times when many spring‐spawning fish reach maximum abundance in coastal waters so that spring and summer variations in larval fish assemblages could be determined in the Yangtze River estuary. Six oceanographic surveys were conducted across the salinity gradient of an inshore (freshwater) and offshore area (brackish intersection) during spring (May) and summer (August) between 2010 and 2012. The fish larval community was dominated by species of Engraulidae, Gobiidae, Champsodontidae and Mugilidae. The pre‐flexion and flexion larval stages of euryhaline marine species, which are dependent on estuaries as nursery areas, were common. The brackish and marine larval assemblage was the most abundant with taxa such as Coilia mystus and Engraulis japonicus accounting for more than 57.3% of the total catch. Spatial differences in the taxonomic composition of larval fish assemblages were evident between the inshore and offshore areas. Additionally, the Yangtze River runoff regulatory functions as affected by the Three Gorges Reservoir operational mode (hydrological alternating operations) showed weak influences on fish and habitat environments. Low salinities from high freshwater inflow limited bay anchovy production in the inshore area.     

Length–weight relationships of cryptic reef fishes from the southwestern Gulf of California, Mèxico

Length–weight relationships of 33 cryptic reef fishes from the southwestern Gulf of California were estimated. The most common families were Gobiidae (seven species), Labrisomidae (four), Pomacentridae (three), and Tripterygiidae (three). These are the first length–weight parameters reported for 32 of these species. Specimens were sampled during a comparative ecological study of community structure of fish assemblages associated with coral heads, rocky walls, and artificial reefs in Bahía de La Paz, Baja California Sur. The b values varied between 2.63 and 3.61. New maximum length records for five of the species were established in the study.     

Seasonality in fish larval assemblage structure within marine reef National Parks in coastal Kenya

Variability of larval assemblages within marine habitats has an effect on population structure of adults, and on patchiness of populations in space and time. However, despite this effect, few studies have examined this variability in the Western Indian Ocean (WIO) especially in relation to marine park boundaries. In this study, we tested the hypothesis that seasonality and biophysical variables influence fish larval assemblage structure within two of the oldest marine parks in Kenya of differing reef structure. Monthly samples were obtained from the parks using oblique plankton tows for 14–24 months. A total of 38 families and 52 genera of fish larvae were obtained from Malindi Marine Park, while 20 genera in 20 families were sampled from the more enclosed Watamu Marine Park but with a connection to an estuarine system. The preflexion larvae comprised over 80% of the total larvae in the parks with the dominant groups being; Gobiidae, Blenniidae, Engraulidae and Apogonidae. The availability of a wide size range of larvae for some groups like Blenniidae, Gobiidae, Engraulidae, Labridae and Scaridae indicated the possibility of some larvae completing their pelagic phase within the parks. Larval densities differed significantly between seasons and stations in both parks, with higher densities ranging between 95–311 larvae/100 m³ during the calm northeast monsoon (NEM) season, compared to 5–58 larvae/100 m³ during the stormy southeast monsoon (SEM) season. Stepwise multiple regression analysis indicated a significant positive influence of zooplankton density on fish larval abundance in Malindi Park, while a positive and significant influence of temperature was found in Watamu Park. Distinct assemblages of larvae occurred within the parks indicating within park patchiness in larval distribution and, perhaps existence of retention features. These results provide useful baseline data on larval distribution in the WIO, and will be useful in understanding population dynamics of adult populations when complimented with additional oceanographic data.     

The effect of parental acclimation to spawning salinity on the survival of larval Cynoscion nebulosus

The yolk and oil depletion of eggs and larvae of spotted seatrout Cynoscion nebulosus , produced by fish collected from two bays with historically different salinity regimes (Matagorda Bay (MB; 18-24%) and Upper Laguna Madre (ULM; 40–50%), Texas, U.S.A. and spawned in salinities of 20, 30 and 40%, differed in their response to both salinity and history. Time to 90% yolk depletion was significantly longer for low salinity bay fish (MB) kept at 20%, but not for high salinity bay fish (ULM) at 20%. The neutral buoyancy salinity of 1 and 2 day old MB 20% larvae was significantly lower than that of MB larvae spawned in 30 or 40%. Overall, eggs and larvae spawned by MB fish were able to hatch out and survive to 3 days post-hatch in lower salinities than those from ULM. Furthermore, the tolerance of eggs and larvae to very low salinities increased with decreasing spawning salinity. The ability of 1–9 day old ULM, but not MB, larvae to survive 18 h exposure to salinities above or below that of spawning exhibited an age-dependent pattern with day 3 being the most sensitive. This study shows that the response of spotted seatrout eggs and larvae to changes in salinity is dependent upon the spawning salinity of the adults and the prevailing salinity regime within the bay.     

Occurrence and distribution of Carangidae larvae (Teleostei,Perciformes) from the Southwest Atlantic Ocean,Brazil (12–23°S)

The objective of this study was to identify larvae species composition, distribution and abundance of carangids along the Brazilian coastal shelf area in order to provide background information on the reproductive community patterns. All carangid larvae used in this study are from the larval fish collection of the Zooplankton and Ichthyoplankton Integrated Laboratory of Federal University of Rio de Janeiro – Brazil (DZUFRJ). Carangid larvae were collected in 13 surveys (nine in the dry season and four during the rainy season) between 1998 and 2008, from Bahia (12°S) to Rio de Janeiro (23°S), comprising 158 sampling stations (45 coastal; 98 oceanic; 15 over seamounts). A bongo net with 330 and 500‐μm mesh size was towed at a speed of about two knots, obliquely (surface‐bottom‐surface) from a maximum depth of 200 m. Samples were collected both during the day and at night and combined in the analysis. A total of 1321 carangid larvae were identified representing 14 species: Decapterus punctatus (56.7%), Chloroscombrus chrysurus (16.8%), Caranx crysos (8.4%), Selar crumenophthalmus (6.3%), Trachurus lathami (6.3%), Caranx latus (2.4%), Carangoides bartholomaei (1.3%), Oligoplites spp. (0.6%), Pseudocaranx dentex (0.3%), Seriola dumerili (0.2%), Elagatis bipinnulata (0.2%), Selene setapinnis (0.2%), Trachinotus carolinus (0.2%) and Selene vomer (0.1%). There was no significant difference in carangid density (P = 0.17) or in species composition (P = 0.09) among the coastal, oceanic and seamount stations. Although there was a significant difference in larval densities between the dry and rainy periods (P = 0.000264), the community composition did not vary significantly (P = 0.47). Therefore, seasonality (rainy and dry periods) seems to be the main factor affecting carangid densities although the community composition is not influenced by sampling periods or by the gradient coast‐ocean.     

Interannual variability in seasonal dynamics and species composition of drifting young-of-the-year fishes in two European lowland rivers

st young-of-the-year (YOY) fishes in two lowland rivers in the Czech Republic (Danube Basin) drifted from mid-May to mid-July and almost exclusively at night. The peak of drift density lasted c . 3 weeks and depended on water temperature (by its effect on fish spawning), but not on discharge. Peak drift densities varied between years and rivers from 80 to 1354 fish 1000 m⁻³. More than 98% of drifting fish were cyprinids. Rutilus rutilus, Rhodeus sericeus, Gobio spp., Alburnus alburnus and Abramis brama were dominate in the 22 species encountered in the River Morava. Carassius auratus gibelio and R. sericeus were the most common of 17 species in the River Kyjovka. Species composition of drifting fishes was similar among years in the Morava but varied in the Kyjovka. The species composition of drifting fishes did not differ from those of the YOY fish assemblage in nursery areas during the drift season. Relative abundances in nursery areas decreased after the drift season in species that dominated in the drift, but increased in those that avoided drift. It is suggested that drift is a regular part of the life history of many cyprinid fishes and interannual variability in density and species composition of drifting YOY fish can be explained by variable spawning success among years. Differences in the relative abundances of the YOY fish assemblage in nurseries during and after the drift season suggests that drift may cause significant mortality.     

Species composition and dynamics of larval and juvenile fishes in the surf zone of Mauritius

The importance of the surf zone as a nursery ground for larval and juvenile fishes has been widely recognized, however the zone has yet to be studied in Mauritius. Recently, the coastal area of the island has been increasingly affected by human activities, especially by tourism. We collected fish samples with a hand pulled seine net during the period of August 2001 to March 2003 to clarify the fish fauna and the dynamics of fishes in the surf zone. Two sampling sites adjacent to river mouth areas and one sampling site adjacent to a mangrove area were selected for comparison of fish fauna in relation to environmental conditions. A total of 9,429 fish larvae and juveniles, representing at least 112 species from 48 families were collected. The abundant species were hardyhead silverside, Atherinomorus lacunosus, bluespot mullet, Valamugil seheli, and Ambassis spp., each contributing 16.2, 12.4, and 11.8% of the total number of individuals, respectively. Estuarine species dominated in the surf zone adjacent to the river mouth areas. Species composition and diversity changed seasonally. The number of fish increased during the rainy season. Species diversity increased at the turn of the seasons from the dry season to the rainy season. We conclude that species composition in each site was affected by environmental factors, such as the scale of the flux from the rivers, which is related to the precipitation. The results indicated that freshwater from the river is a trigger to aggregate larvae and juveniles in the surf zone.     

Effects of temperature gradients resulting from reservoir discharge on Dorosoma cepedianum spawning in the Savannah River

Synopsis The timing and spatial pattern of gizzard shad, Dorosoma cepedianum, spawning were markedly affected by a temperature gradient caused by the release of hypolimnetic water from an upstream reservoir into the middle reaches of the Savannah River. During 1983 and 1984, a distinct thermal gradient occurred with the warmest temperatures at the downstream end of the 257 km study reach and the coolest temperatures at the upstream end. The occurrence of gizzard shad larvae indicated that spawning began at the sample stations farthest downstream and progressed upstream, peaking at each sample station when it warmed to approximately 19° C. The estimated difference in date of peak density of larvae between the upstream and downstream ends of the gradient was 23 days in 1983 and 35 days in 1984. Because of this pattern, densities of larvae were highest at the downstream end of the study area early in the spawning season and highest at the upstream end of the study area late in the spawning season.Photoperiod and daylength appeared unrelated to the patterns under study. Far-reaching effects of anthropogenic temperature changes on fish spawning and the distribution of larvae are probably common in rivers that receive hypolimnetic discharge.     

Effect of artificial wetting and rainfall on the larval diapause of a stem borer, Busseola fusca in Western Kenya

Clarification of factors enabling diapause termination was carried out in a stem borer, Busseola fusca. Diapausing larvae very rarely pupated under dry conditions. Water apparently played a significant role in the termination of late diapause. During the late diapause period, larvae in the field were exposed to rains of the short rainy season. This precipitation, however, terminated diapause in only a few larvae, which indicate that termination requires sustained exposure to wet conditions that are not usually met during the short rains.

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Résumé Les causes de la fin de la diapause ont été précisées sur B. fusca. Les chenilles diapausantes se nymphosent très rarement en conditions sèches. L'eau joue apparement un rôle important dans la fin de la dernière phase de la diapause. Dans la nature, les chenilles sont exposées pendant cette période aux plues de la brève saison de pluies. Cependant, ces précipitations n'interrompent la diapause que d'un nombre limité de chenilles, ce qui montre que la fin de la diapause exige une exposition prolongée à des conditions humides que l'on ne rencontre pas généralement pendant la brève saison des pluies.

     

Spawning areas and early development of long spiky-head carp (Luciobrama macrocephalus) in the Yangtze River and Pearl River, China

The spawning areas and early development of long spiky-head carp, Luciobrama macrocephalus (Lacépède), an endemic fish species in China, were investigated in the Yangtze River and Pearl River of central and southeastern China between 1961 and 1993. The potamodromous fish migrated upstream to spawn between May and July as the floodwater began to rise. The water-hardened eggs drifted down the river, and the embryos and larvae developed in the course of drifting. The spawning areas of the fish were widely found in the upper and middle main channels and large tributaries. Two large dams (Gezhouba dam and Danjiangkou dam) did not significantly impact on the reproduction of the fish. Fifty stages of the early development from one cell to the juvenile with fully formed fins were observed and characterized pictorially. The larvae of long spiky-head carp could be distinguished from the larvae of other co-occurring species by counting the number of somites and comparing the proportion of sizes of eye to otic capsule.     

Feeding habits and seasonal trophic guilds structuring fish community in the bay mouth region of a tropical estuarine habitat

Understanding trophic relationships of fish in estuarine ecosystem is an important element for sustainable resource management. This study examined the feeding habits of 29 dominant fish species, characterized the trophic guilds, assessed the impact of season and clarified the role of diets in structuring the fish community in the mouth region of Pattani Bay, Thailand. Samples of 5792 fishes collected monthly by gillnets from March 2019 to February 2020 were used for stomach content analyses. It was found that the number of food types and fullness index differed between fish taxa (P < 0.001). Most fishes were specialist feeders feeding on specific food components and were categorized into five trophic guilds: piscivore, shrimp-fish feeder, polychaete feeder, zooplanktivore and planktivore. Six species were piscivorous, considered as apex predators, that fed almost entirely on fishes. High diet overlaps among some species (>0.6) were recorded. Not much variation in seasonal guilds was observed: four guilds in the dry season, three in the moderate rainy season and four in the rainy season. Some species remained in the same guild the whole year round, but some fishes changed seasonally. Two fish communities from different regions of the bay were segregated based on feeding habits. The inner bay community comprised mainly copepod and plankton feeders, but there were more piscivores in the deeper bay mouth area. Results from this study help us to understand the feeding habits and trophic guilds of dominant fish species at the mouth of this tropical estuarine bay.     

Spatial and temporal variation in fish community structure of a marine embayment in Zanzibar,Tanzania

Spatial and temporal variation in the fish community structure were studied in a tropical non-estuarine embayment in Chwaka Bay, Zanzibar (Tanzania). Fish samples were collected bi-monthly (at each spring low tide) for 1 year (November 2001–October 2002) from a range of bay habitats ranging from mangroves deep inside the bay to seagrass beds close to the mouth of the bay. Additionally, environmental variables were examined to determine their relationship with the fish community structure. Being a non-estuarine embayment, the environmental variables as well as the fish community structure in each habitat remained relatively constant for most part of the year; however, a marked decline was observed during the rainy period (April–May). Significant variations in fish community variables (density, biomass and species richness) and in water temperature and salinity were observed during the rainy season in all habitats, with larger changes in the mangrove and mud/sand flats habitats than in the seagrass beds. Seasonal variations in water clarity and dissolved oxygen were not significant, though. Many species disappeared from the mangrove and mud/sand flats habitats during the rainy season and those which persisted showed a remarkable decrease in density. Moreover, the results indicate that mangroves were the preferred settling habitats for Gerres filamentosus, Gerres oyena, Lethrinus lentjan and Monodactylus argenteus, especially during the dry period (December–February) before the rainy season. This observation is contrary to what has been reported from some other tropical regions where greater abundance and species richness was observed during the rainy season. A significant relationship was found between density of fish and temperature, salinity and turbidity. Since salinity was the most conspicuously changing environmental variable with seasons, we propose that salinity, alone or in combination with low visibility and temperature, was probably the most important environmental factor structuring the fish assemblage in the mangrove and mud/sand flats habitats, particularly during the rainy season. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: J. A. Cambray     

Connectivity of a large embayment and coastal fishery: spawning aggregations in one bay source local and broad-scale fishery replenishment

Ichthyoplankton sampling and otolith chemistry were used to determine the importance of transient spawning aggregations of snapper Chrysophrys auratus (Sparidae) in a large embayment, Port Phillip Bay (PPB), Australia, as a source of local and broad-scale fishery replenishment. Ichthyoplankton sampling across five spawning seasons within PPB, across the narrow entrance to the bay and in adjacent coastal waters, indicated that although spawning may occur in coastal waters, the spawning aggregations within the bay were the primary source of larval recruitment to the bay. Otolith chemical signatures previously characterized for 0+ year C. auratus of two cohorts (2000 and 2001) were used as the baseline signatures to quantify the contribution that fish derived from reproduction in PPB make to fishery replenishment. Sampling of these cohorts over a 5 year period at various widely dispersed fishery regions, combined with maximum likelihood analyses of the chemistry of the 0+ year otolith portions of these older fish, indicated that C. auratus of 1 to 3+ years of age displayed both local residency and broad-scale emigration from PPB to populate coastal waters and an adjacent bay (Western Port). While the PPB fishery was consistently dominated (>70%) by locally derived fish irrespective of cohort or age, the contribution of fish that had originated from PPB to distant populations increased with age. At 4 to 5+ years of age, when C. auratus mature and fully recruit to the fishery, populations of both cohorts across the entire central and western Victorian fishery, including two major embayments and c. 800 km of coastal waters, were dominated (>70%) by fish that had originated from the spawning aggregations and nursery habitat within PPB. Dependence of this broadly dispersed fishery on replenishment from heavily targeted spawning aggregations within one embayment has significant implications for management and monitoring programmes.     

中街山列岛海域鱼卵、仔稚鱼群落结构特征及其与环境因子的关系

为了解中街山列岛海域鱼卵仔稚鱼空间分布、种类组成及与环境因子的关系,于2010年5月—2012年2月在中街山列岛海域利用水平和垂直拖网开展了8个航次的鱼卵、仔稚鱼调查。运用非度量多维标度排序、聚类分析和典范对应分析(CCA)等方法对该海域鱼卵、仔稚鱼的空间分布进行了综合分析。结果表明:两年水平拖网共采集到鱼卵1783粒,仔稚鱼67尾;垂直拖网共采集到鱼卵576粒,仔稚鱼59尾。2010年平拖优势种为短吻红舌鳎(Cynoglossus joyneri),垂拖重要种为鲉形目未定种(Scorpaeniformes sp.)和扁舵鰹(Auxis thazard)。2011年平拖重要种为短吻红舌鳎、鰏属未定种(Leiognathuss sp.)、龙头鱼(Harpodon nehereus)和鳀(Engraulis japonicus);垂拖重要种为短吻红舌鳎、龙头鱼和中华小公鱼(Stolephorus chinensis)。经单因子相似性分析(ANOSIM),鱼卵仔稚鱼的优势种和重要种群落物种组成存在显著差异(P0.01)。研究结果表明,温度和盐度对鱼卵仔稚鱼的影响较大,夏季是中街山列岛海域鱼类产卵的重要时期。该海域以恋礁的小型底层鱼类为主,是褐菖鲉(Sebastiscus marmoratus)、龙头鱼等小型底层经济鱼类的重要产卵场和育幼场。     

New findings of rare fish species in Indian and Pacific oceans with the description of two new species from the families Gobiidae and Platycephalidae

We provide information about the morphology and new findings of 15 rare fish species from the families Bathyclupeidae, Callionymidae, Champsodontidae, Cottidae, Gobiidae, Lophichthyidae, Melanostomiidae, Moridae, Oneirodidae, Paralepididae, Pegasidae, Platycephalidae, and Uranoscopidae. Two new species are described: Thysanophrys haploblepharis sp. n. (Platycephalidae) from the Western Indian Ocean and Vanderhorstia stegauchenia sp. n. (Gobiidae) from the South China Sea. The new synonymy is established: Cottus dybowskii Hilgendorf, 1879 = Myoxocephalus brandtii.     

COMPOSITION,ABUNDANCE AND SEASONALITY OF LARVAL FISH IN RICHARDS BAY HARBOUR,KWAZULU-NATAL,SOUTH AFRICA

Summary

The present study examined the composition, abundance and seasonality of fish larvae occurring in Richards Bay Harbour, over an 18-month period from June 1991 to November 1992. Ichthyoplankton samples were collected every six weeks at top, mid and bottom depths in the dredged channel 100 to 200 m from the harbour entrance. A total of 7 163 fish larvae, representing 105 taxa and 53 families, was collected throughout the study period. The dominant families were the Engraulidae and Gobiidae representing 50% and 37% of the total catch, respectively. The most abundant larvae were those of the thorny anchovy, Stolephorus holodon, and an unidentified goby, Gobiid 12 (32% and 30% of the total catch, respectively). Estuarine-associated taxa dominated the total catch in terms of density (61%), with 11 out of the 28 taxa being totally dependent on estuaries at some stage in their life cycle. Turbidity and temperature were significant variables accounting for 27% of the variation in larval densities of estuarine-dependent species. The main peak in larval density occurred in January 1992 (summer) with a mean larval density of 160 larvae per 100 m³. Larvae of estuarine-associated taxa were predominantly at the flexion and postflexion developmental stages. Since larval densities of certain estuarine-associated species were significantly greater in bottom samples and on flood tides, it is suggested that selective tidal stream transport is a recruitment mechanism used by these species. The present study concluded that it is important to maintain and preserve the estuarine component of Richards Bay Harbour so that the system can function as an estuarine nursery for many of the fish species depending on it at certain stages in their life cycle.     

Hatch-period-dependent early growth and survival of Pacific herring Clupea pallasii in Miyako Bay, Japan

Considerable interannual variation in the abundance of larval and juvenile Pacific herring Clupea pallasii was detected in Miyako Bay, on the Pacific coast of northern Japan; abundances were high in 2001 and 2003 and low in 2000 and 2002. Hatch dates and growth rates for larval and juvenile survivors were estimated through otolith analysis. Water temperature and food availability were monitored on the spawning and nursery grounds in the inner part of the bay. The number of spawning females caught in nets set around the spawning ground was recorded during each spawning season (January to May) in 2000–2003. No correlation was found between the number of spawning females and the abundance of larvae and juveniles on the spawning and nursery grounds. The hatch dates of surviving larvae and juveniles were concentrated at the end of the spawning season in 2001 and in the middle of the season in 2003. The larvae experienced relatively high prey concentrations during the first-feeding period in 2001 but low concentrations in 2003. Survival of larvae during the first-feeding period may be a function of prey concentration as well as water temperature. In 2003, low water temperature would reduce starvation mortality during the first-feeding period. In contrast, unfavourable feeding conditions with higher temperatures during the first-feeding period seemed to result in low larval survival in 2000 and 2002. The 2001 larvae grew faster than those in 2003 because of the late hatch dates and the higher ambient temperatures that resulted. Temperature might be a major factor controlling growth rates of C. pallasii larvae in Miyako Bay.