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1.
ABSTRACT:   To determine the growth performances and habitat characteristics of spotted halibut Verasper variegatus , successive samplings were conducted in the south-eastern coastal area of Shimabara Peninsula in Ariake Bay. The push-net samplings were performed at Kamaga beach from May 2003 to April 2004 to determine the horizontal distribution of larvae and juveniles, while the gill net samplings were done in the coastal waters of Tatsuishi beach from July 2003 to July 2004 to collect the larger juveniles and adults. A total of 478 individuals from metamorphosing larvae to 2-year-old fish (15.2–447.0 mm total length [TL]) were sampled. In particular, the 2003-year class fish were successively collected from May 2003 to June 2004 (15.2–350.0 mm TL; n  = 418) and the mean total length in March, June, September, December 2003 and May 2004 was 22.4, 82.5, 172.5, 203.9 and 296.4 mm, respectively. The present study found that metamorphosing larvae migrated into the estuarine tidal flats during March 2003; newly settled juveniles inhabited the shallow intertidal areas; and juveniles had a remarkably high growth in shallow coastal areas. It is suggested that young fish around 300 mm TL migrated from the nursery grounds in Ariake Bay to deeper waters around Tachibana Bay during May–June 2004.  相似文献   

2.
Otolith Sr:Ca ratios were used to evaluate the contribution of estuarine nursery areas to the temperate seabass (Lateolabrax japonicus) population in Tango Bay, the Sea of Japan. Otolith Sr:Ca ratios of juveniles collected from freshwater, brackish and coastal areas were analysed to determine a criterion for distinguishing whether individuals used estuarine or coastal areas as nurseries. Otolith Sr:Ca ratios of adult seabass collected around Tango Bay were also analysed to detect the records of salinity that juveniles experienced and to estimate the contribution of each habitat. Sr:Ca ratios of the edges of otoliths of juveniles from freshwater areas were 2.4 × 10?3 in average, which were significantly lower than those of juveniles collected from a coastal area (4.9 × 10?3 in average) owing to differences in salinity conditions among these areas. Based on the threshold criterion determined by this difference, 39 out of 107 (36%) adult seabass were estimated to have used the estuary as a nursery during their juvenile stage according to their Sr:Ca chronologies. Despite the small area covered by estuarine nurseries compared with coastal waters, the Yura River estuary contributed considerably to the adult seabass population. This indicates estuaries play an important role as nurseries for seabass juveniles, and it should be noted that the estuaries are important nurseries to conserve the stocks of coastal fishes.  相似文献   

3.
Northwesterly cold winds characteristic of the East Asian Winter Monsoon (EAWM) dictate winter climatic conditions over the Japanese Archipelago. Japanese temperate bass Lateolabrax japonicus is a commercially important coastal fish that spawns offshore in winter and uses shallow waters as nursery habitats. To investigate the effects of EAWM on the planktonic period of L. japonicus, eggs, larvae, and juveniles were quantitatively collected in Tango Bay on the Sea of Japan side in winter and spring from 2007 to 2017. Although eggs occurred close to the mouth of the bay, planktonic larvae occurred further inside as they developed. The horizontal distribution of planktonic larvae, combined with water velocity data obtained from mooring observations, indicated that planktonic larvae are transported south‐ to westward through Ekman current and an anticyclonic circulation, which are driven by northwesterly winds. To evaluate survival during the planktonic period in each year class, the abundance of benthic larvae/juveniles was divided by winter total landings of Lateolabrax spp. (proxy of the spawning stock size). This survival index exhibited a positive correlation with the northwesterly component of winter winds, and a negative correlation with winter air temperature (average from December to February, Spearman's correlation, p < .05). There was, however, no significant correlation with winter water temperature or winter freshwater discharge in the bay. We conclude that northwesterly cold winds of EAWM play a critical role in transporting L. japonicus eggs and larvae toward nursery habitats, specifically beaches and estuaries fringing the innermost part of Tango Bay.  相似文献   

4.
The occurrence and distribution of settling and settled spotted halibut Verasper variegatus were compared with those of Japanese flounder Paralichthys olivaceus in shallow habitats around Shimabara Peninsula, western Japan, to elucidate the settlement and recruitment characteristics of spotted halibut, a rare pleuronectid flatfish in Japan. Push-net sampling conducted at nine sites in March and April 2003 collected spotted halibut from four nurseries located at eastern areas of Shimabara Peninsula in Ariake Bay; Japanese flounder were sampled from eight nurseries. Comparison of microhabitat distributions in a tidal-flat nursery during February?CApril in 2003?C2007 revealed that metamorphosing larvae and juveniles of spotted halibut, which showed the drastic body coloration (black to brown) and behavioral changes (frequent swimming to settlement), were distributed mainly in the lower edge of the intertidal area, whereas Japanese flounder inhabited both intertidal and subtidal areas. Metamorphosing larvae of spotted halibut (12.6?C16.5?mm standard length; n?=?24) were collected in March when the highest densities were observed, whereas metamorphosing larvae of Japanese flounder (10.0?C15.9?mm, n?=?55) were observed during March?CApril. Our results suggest that spotted halibut has a narrower time/space window for recruitment to the specific nurseries compared with Japanese flounder.  相似文献   

5.
The horizontal distribution of the early life stages of small yellow croaker Larimichthys polyactis in the Yangtze River estuary and its adjacent area was investigated through six ichthyoplankton surveys conducted during the period of mid-April to mid-July 2015. A total of seven eggs and 2461 larvae and juveniles of small yellow croaker were collected. Abundance of the specimens was highest in mid-May and lowest in mid-July. The composition of the different development stages of small yellow croaker varied among the six cruises, although post-flexion larvae and juveniles dominated the ichthyoplankton collection in each cruise. Specimens at different development stages showed different distribution patterns in the study area. The eggs, yolk-sac and pre-flexion larvae were mainly collected at stations with depth exceeding 30 m, while post-flexion larvae and juveniles were mainly distributed in the relatively shallow waters near to the mouth of the Yangtze River. In conclusion, the study suggested that the study area had largely lost the ecological function to support small yellow croaker spawning, although it could still serve as nursery ground for the species.  相似文献   

6.
ABSTRACT:   Predation experiments were conducted in mesocosms to test the hypothesis that habitat complexity affects vulnerability of red sea bream Pagrus major juveniles to piscivorous fish predators. Juvenile behavior was video-recorded for 6 h in two structurally different habitats: vegetated with sea grass Zostera marina , and unvegetated 0.5-t tanks. Association behavior with seagrass was observed in the vegetated tank throughout the trials. Predation experiments were conducted with 30 red sea bream juveniles (29.9 mm body length) exposed to two individuals of the piscivorous fish predator Chinese sea bass Lateolabrax sp. (261.6 mm), for 6 h in 1.0-t tanks. Predation rate (no. of fish predated on per predator per h) was significantly lower in the vegetated tank (0.02/predator per h) than in the unvegetated tank (0.27/predator per h). Present experiments indicate that habitat complexity reduces vulnerability of juvenile red sea bream to predation by piscivorous fish by serving as physical and/or visual barriers and limiting the predator's ability to pursue and capture prey. Seagrass beds in the shallow coastal waters around Japan are suggested to be an important nursery for red sea bream since they provide the juveniles with habitat complexity as well as serve as a feeding ground.  相似文献   

7.
The spatial and temporal occurrence of pelagic fish stages and their biological variability may affect their dispersal and survival, and ultimately fish recruitment. We collected Atlantic cod larvae at one station inside and at one station outside the Gullmar Fjord, eastern Skagerrak, in order to investigate small-scale larval group differentiation. Rectangular midwater trawl hauls were taken every 6 h (during 24 h) from three separate depth intervals between the surface and 70 m depth. About 80% and 20% of all larvae occurred above the halocline at the Fjord station and the Coastal station, respectively. Hatching (at both stations) occurred from the 3rd week in February to the 1st week in May, indicating that cod larvae were present for at least 5 months (from late February to early August). The length and hatch date frequency distributions of larvae from the surface layer were unimodal inside the fjord but bimodal outside the fjord. Analyses of seven microsatellite DNA loci indicated that larvae collected inside the fjord (where local spawning occurs) were genetically distinct from larvae sampled on the outside (FST = 0.0026). The two age cohorts outside the fjord were not, however, genetically different, nor were larvae collected at different depths. We conclude that small-scale variability of vertical concentration and larval life history variability should have consequences for interpreting models of larval dispersal and survival, and subpopulation structure analyses.  相似文献   

8.
ABSTRACT:   It is important to clarify trophic dynamics in marine ecosystems for management of the fishing ground. Organic carbon sources and trophic position of pelagic fishes in the coastal waters of the south-eastern Izu Peninsula, Japan, were examined on the basis of carbon and nitrogen stable isotope distributions. The δ13C of the fishes was mostly distributed from −19 to −16‰ for nektonic fishes (13 species of adults and immatures) and planktonic fishes (10 species of larvae and juveniles), close to the δ13C values of particulate organic matter and planktonic decapods. These δ13C signatures for the inhabitants of the water column were in contrast with the high δ13C values (mainly −16 to −13‰) for demersal fishes of Scorpaeniformes and benthic polychaetes collected in the surf zone. These results indicate that nektonic and planktonic fishes depend on phytoplankton for carbon supply. The δ15N signatures suggest that the trophic position ranged 3.1–4.5 for the nektonic fishes and 2.9–3.7 for the planktonic fishes, premised on trophic level 3 for larval Japanese anchovy Engraulis japonicus . Thus, planktivorous fishes should be mainly assigned to trophic levels 3 and 4 in this area.  相似文献   

9.
This study aimed at (1) evaluating the efficacy of live food organisms (Artemia and natural zooplankton) and an artificial diet in the larval rearing of African carp Labeo parvus and (2) determining appropriate rearing conditions. After yolk sac resorption, the larvae were separated into five different feeding trials with two replicates. At the end of the larval rearing period (28 days post‐hatching), the highest (94.6%) and the lowest (53.7%) cumulative survival rates were found when larvae were fed with natural zooplankton for 7 days followed by Nippai food for 21 days, and when larvae were fed from the beginning of exogenous feeding with Nippai food only respectively. The significant highest body weight (351.6 mg), total length (34.4 mm) and specific growth rates (15.5%day?1) were recorded when the larvae were fed with Artemia nauplii for 14 days followed by Nippai food for 14 days. The lowest growth performance (body weight and specific growth rates) were obtained when larvae were fed exclusively Nippai food. These results indicate that L. parvus can be successfully cultured in indoor nursery systems from hatching to the early juvenile stage.  相似文献   

10.
1. The soft‐shell clam, Mya arenaria, was intentionally introduced to Washington State during the mid‐1870s. Presently, extensive shell deposits cover parts of the intertidal flats of Grays Harbor, an estuarine ecosystem that has received much attention because of its role as nursery ground for Dungeness crab (Cancer magister), a commercially significant species. 2. Preliminary observations revealed that shells in the deposits belonged to clams that were much larger than extant conspecifics. Shell deposits and extant populations have spatially disjoint distributions; few individuals are found living within the deposits. The purpose of our study was to determine the cause of the different size characteristics between extinct and extant clams, when and how the deposits originated, and why the extant population does not prosper in what appears to be prime habitat. 3. We (i) surveyed extant populations and shell deposits, (ii) followed the extant population through periodic sampling over a 3‐year period, (iii) investigated growth and survival in extant and extinct populations, (iv) experimentally manipulated growth conditions, and (v) searched archival sources for information about the origin of the deposits. 4. We conclude that extinct clams grew faster and lived longer, apparently because they occupied the best habitats available. Archival records suggest that the population expanded rapidly during the period around 20 years after its introduction, but was decimated between 1895 and 1897 by a mass‐mortality episode that resulted in the formation of the deposits. The population since then has never rebounded in its prime habitat, in spite of potential settlers being regularly available. 5. Dungeness crab larvae settle preferentially in the shell deposits, where the abundance of 0+ age juveniles is orders of magnitude higher than in the adjacent flats. We hypothesize that predation by juvenile crabs limits clam recruitment. 6. The introduction of Mya to Grays Harbor during the 1870s has had long‐lasting effects, which persist a century after their once large populations were decimated by a mass‐mortality event. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

11.
A seasonal migration pattern for silver kob, Argyrosomus inodorus (Griffiths & Heemstra) is elucidated based on tag-recapture data. Spawning adults start migrating southwards against the north-westerly surface currents at the beginning of the austral summer from the northern end of their distributional range to their spawning grounds, Sandwich and Meob Bays, at the southern end of their distributional range. It is suggested that after spawning larvae drift north with the current to the nursery areas, the West coast Recreational area (WCR). When juveniles reach the age of approximately 2 years they will gradually move north towards the adult feeding ground, the Skeleton Coast Park (SCP) waters. At the end of the spawning season when the surf-zone water temperature decreases to about 15 °C adult silver kob complete their spawning cycle by returning to the adult feeding ground, probably moving slightly offshore and with the current.  相似文献   

12.
Abstract:   The community and trophic structures of the subtidal habitat of the abalone Haliotis diversicolor were examined in Nagai, Sagami Bay, Japan. Conventional community indices showed no significant differences among three sampling stations. The overall continuum of stable isotope ratios was structured into three different trophic linkages: (i) brown algae-dependent benthic food chain; (ii) red algae-dependent benthic food chain; and (iii) planktonic food chain. Brown algae and red algae likely play different roles with respect to carbon sources in the habitat. Conventional fractionation values indicated that the abalone H. diversicolor (δ13C = −12.4 ± 1.0‰, δ15N = 9.3 ± 0.5‰) feeds on the lamina of Undaria pinnatifida during juvenile and adult stages (8.0–65.6 mm shell length). Stable isotope signatures suggested that the juveniles of other abalone species as well as some amphipods and a sea cucumber Holothuria decorata are competitors of H. diversicolor , whereas some Muricidae gastropods such as Thais bronni and Ergalatax contractus are predators. The isotopic differences among macroalgal species and the subsequent transfer to consumers indicate that stable isotopic analysis is an effective means of studying food webs in an open rocky shore community with little influence from external primary production such as terrestrial vegetation.  相似文献   

13.
Morphological characteristics and body pigmentations of juvenile slime flounder Microstomus achne were described from one specimen [27.8 mm total length (TL)] collected off Niigata Prefecture from the Sea of Japan (35 m depth) in May 1993 and from three specimens (30.1, 36.2, and 40.9 mm TL) collected off Fukushima Prefecture on the Pacific coast of northern Japan (15 and 50 m depths) during April–May 2008 and 2009. These age-0 juveniles had a characteristically slenderly oval-shaped body and slightly protruded front nostrils. Sparsely distributed melanophores and xanthophores were clearly visible throughout the ocular side of one specimen, which was judged as a newly settled juvenile, whereas several spots aggregated by small melanophores were found in the others with elongated pectoral fins and small cycloid scales. Melanophores were only slightly detectable on the blind side. Comparisons of the depth distributions of slime flounder juveniles and sympatrically collected age-0 pleuronectids (Pseudopleuronectes herzensteini, Pseudopleuronectes yokohamae, Platichthys bicoloratus, and Dexistes rikuzenius) suggested that slime flounder can settle on broad nursery areas of coastal and offshore pleuronectid flatfishes, probably depending on local oceanic conditions during the protracted pelagic phase.  相似文献   

14.
Fisheries Science - To clarify nursery habitat use for larval and juvenile Pacific herring Clupea pallasii, we collected eggs, larvae, and juveniles at several sampling sites in inner Miyako Bay...  相似文献   

15.
Horizontal distribution patterns of jack mackerel (Trachurus japonicus) larvae and juveniles were investigated in the East China Sea between 4 February and 30 April 2001. A total of 1549 larvae and juveniles were collected by bongo and neuston nets at 357 stations. The larvae were concentrated in the frontal area between the Kuroshio Current and shelf waters in the upstream region of the Kuroshio. The abundance of small larvae (<3 mm notochord length) was highest in the southern East China Sea (SECS) south of 28°N, suggesting that the principal spawning ground is formed in the SECS from late winter to spring. Jack mackerel also spawned in the northern and central East China Sea (NECS and CECS, respectively), as some small larvae were also collected in these areas. In the SECS, the abundance of small larvae was highest in February and gradually decreased from March to April. The habitat temperature of small larvae in the SECS and CECS (20–26°C) was higher than that in the NECS (15–21°C), suggesting higher growth rates in the SECS and CECS than in the NECS. The juveniles (10‐ to 30‐mm standard length) became abundant in the NECS off the west coast of Kyushu Island and CECS in April and were collected in association with scyphozoans typical of the Kuroshio waters. However, juveniles were rarely collected in the SECS, where the small larvae were concentrated. Considering the current systems in the study area, a large number of the eggs and larvae spawned and hatched in the SECS would be transported northeastward by the Kuroshio and its branches into the jack mackerels’ nursery grounds, such as the shallow waters off the west coast of Kyushu and the Pacific coast of southern Japan.  相似文献   

16.
This study evaluates the effectiveness of two fish passes at two hydropower dams (Canoas I and II) in the Upper Parana basin, which form part of a cascade of three reservoirs. Fish from 12 migratory species (3089 specimens) were captured during their ascending, reproductive migration and were tagged with hydrostatic tags. The recapture data (294 specimens over two consecutive years) showed that there is a strong tendency for the maintenance of ascending migration through reservoirs with fish passes but with differences in migratory activity within the same species. No eggs, larvae or juveniles of these species were found in samples collected over 5 years in the reservoirs above the fish passes. These data suggest that fish passes have contributed to the restoration of the migratory routes of adult fish but that in the absence of suitable spawning or nursery habitats for these species; they probably act as ecological traps and do not contribute to the recruitment of the species.  相似文献   

17.
东海区泗礁沙滩碎波带仔稚鱼种类组成及栖息地利用模式   总被引：2，自引：1，他引：1  
为探明泗礁沙滩碎波带仔稚鱼种类组成及其对碎波带的利用模式,于2010年7月至2011年8月每月大潮期间,在泗礁沙滩8个站位点水深0.5~1.5 m处,两人沿海岸平行方向步行拖曳小型拖网(1 m×4 m,网目1 mm)采集仔稚鱼样本。周年采集仔稚鱼1 762尾,隶属于28科46种,其中海洋性鱼类29种,河口性鱼类14种,洄游性鱼类2种,淡水性鱼类1种。体长10~30 mm的仔稚鱼占总渔获量的87.05%;后弯曲期仔鱼和稚鱼分别占总渔获量的24.57%和68.27%。鳀(Engraulis japonicus)为优势种,占总渔获量的55.68%。种类数及单位捕捞努力渔获量(CPUE)春夏季较高而秋冬较低,种类数和CPUE峰值分别出现在2010年8月和2011年5月。站点间的种类数和CPUE变化表明,仔稚鱼偏好栖息于封闭型沙滩碎波带。前10位主要种对碎波带的利用分3种类型:鳀、中国花鲈(Lateolabrax maculatus)、鮻(Liza haematocheila)和棘头梅童鱼(Collichthys lucidus)利用碎波带作为保育场;中华侧带小公鱼(Stolephorus chinensis)、鲻(Mugil cephalus)、细鳞鯻(Terapon jarbua)和弓斑东方鲀(Takifugu ocellatus)连续数月利用碎波带作为暂时栖息地;相模虾虎鱼(Sagamia geneionema)和鲬(Platycephalus indicus)则在单月进入碎波带栖息。因此在进行海滩和港湾开发和利用时,应重视对沙滩破碎带仔稚鱼栖息地的保护。  相似文献   

18.
Chaetognatha were among the most dominant macrozooplankton taxa collected in 6 years of springtime collections, both throughout the water column and near-bottom on the continental shelf in the northern Gulf of Alaska. Three species ( Sagitta elegans, S. scrippsae, and Eukrohnia hamata ) were collected in 248 collections, although S. elegans was the numerically dominant species overall during most cruises. Collections taken in epibenthic sleds generally contained about two orders of magnitude more chaetognaths than those that sampled throughout the water column. Two size modes were apparent in the S. elegans size-frequency distributions which were believed to belong to different cohorts. Growth rate was on the order of 2–3 mm per month. The two cohorts showed asynchronous diel vertical distribution patterns, with the smaller individuals found near the surface during the day whereas the larger individuals were near the surface at night. About 7.5% of the S. elegans examined contained food. Copepods made up the majority (∼89% by number) of the diet of both large and small individuals. Euphausiid juveniles and cirripede larvae were also observed, as well as several incidences of cannibalism by large chaetognaths on smaller individuals. Based on the results of two diel series, this species was observed to feed mainly during the night-time.  相似文献   

19.
An individual‐based model (IBM) for the simulation of year‐to‐year survival during the early life‐history stages of the north‐east Atlantic stock of mackerel (Scomber scombrus) was developed within the EU funded Shelf‐Edge Advection, Mortality and Recruitment (SEAMAR) programme. The IBM included transport, growth and survival and was used to track the passive movement of mackerel eggs, larvae and post‐larvae and determine their distribution and abundance after approximately 2 months of drift. One of the main outputs from the IBM, namely distributions and numbers of surviving post‐larvae, are compared with field data as recruit (age‐0/age‐1 juveniles) distribution and abundance for the years 1998, 1999 and 2000. The juvenile distributions show more inter‐annual and spatial variability than the modelled distributions of survivors; this may be due to the restriction of using the same initial egg distribution for all 3 yr of simulation. The IBM simulations indicate two main recruitment areas for the north‐east Atlantic stock of mackerel, these being Porcupine Bank and the south‐eastern Bay of Biscay. These areas correspond to areas of high juvenile catches, although the juveniles generally have a more widespread distribution than the model simulations. The best agreement between modelled data and field data for distribution (juveniles and model survivors) is for the year 1998. The juvenile catches in different representative nursery areas are totalled to give a field abundance index (FAI). This index is compared with a model survivor index (MSI) which is calculated from the total of survivors for the whole spawning season. The MSI compares favourably with the FAI for 1998 and 1999 but not for 2000; in this year, juvenile catches dropped sharply compared with the previous years but there was no equivalent drop in modelled survivors.  相似文献   

20.
Assemblages of vertical migratory mesopelagic fish are described for the nighttime upper 20 m layer of the transitional and adjacent waters in the western North Pacific. Twenty-three mesopelagic fish species belonging to six families and 16 genera were collected during June 1996. Family Myctophidae was most speciose, represented by 17 species, followed by Sternoptychidae (two spp.) and Bathylagidae (one spp.). Six assemblages are recognized based on their species composition: Subarctic, Northern Transition, Southern Transition, Subtropical, Slope Water and Seamount Assemblages. These assemblages are also characterized by size composition and biomass of the catches. The distributions of the Subarctic, Northern Transition, Southern Transition and Subtropical Assemblages are approximately defined by the Kuroshio and Oyashio fronts and the Subarctic Boundary. Slope Water and Seamount Assemblages are closely related to the slope water around the shelf edge off Japan and waters around the Shatsky Rise and the Emperor Seamount chain, respectively. The importance of the Southern Transition Assemblage area between the Kuroshio front and Subarctic Boundary as spawning and nursery grounds of many subarctic, transitional and subtropical fishes is elucidated, based on the geographical distribution patterns of their larvae and juveniles.  相似文献   

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