Changes of sperm morphology,volume, density,and motility parameters in northern pike during the spawning period

Sexually mature males (BW?=?1600?±?150 g and TL?=?235?±?30 mm) of northern pike (Esox lucius L.) were randomly selected from a pond to record changes in their sperm quality parameters (spermatozoa morphology, sperm volume, density, and motility parameters) during the spawning season. The morphological and motility parameters changed significantly during the reproductive season with following trends. Only, head width was not changed during the spawning season. The longest spermatozoa and its flagellar length were found at the middle of spawning period (TL?=?38.24?±?0.37 μm and 35.14?±?0.26 μm) and shortest at the beginning of spawning period (TL?=?34.81?±?0.29 μm and 32.53?±?0.18 μm). Other morphological characters were always the lowest at the beginning of spawning period. Sperm volume was changed from 0.33?±?0.3 ml in February, 0.43?±?0.2 ml in March to 0.24?±?0.1 ml in April, and density from 16.2?±?0.2?×?109 spermatozoa ml^?1 in February, 19.4?±?0.2?×?109 spermatozoa ml^?1 in March to 4.8?±?0.2?×?109 spermatozoa ml^?1 in April. Same sperm velocity was observed in all spawning terms at 10 and 20 s after activation. Higher velocity was found at 30 and 40 s after activation in sperm collected at the middle and the end of spawning period. Significantly, higher percentage of motile sperm was observed at 20, 30, and 40 s after activation in sperm sampled at the end of spawning period. This study supports the hypothesis that longer spermatozoa swim faster.     

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.     

Discovery of a spawning area of the common Japanese conger <Emphasis Type="Italic">Conger myriaster</Emphasis> along the Kyushu-Palau Ridge in the western North Pacific

The common Japanese conger Conger myriaster is an important commercial coastal fisheries species in East Asia, but its spawning area has not been determined. A larval sampling survey was conducted in September 2008 along 136°E between 13°N and 22°N, which roughly followed the Kyushu-Palau Ridge in the western North Pacific. Twenty larval specimens were confirmed to be C. myriaster using DNA analysis. Two were newly hatched larvae (preleptocephali) 5.8 and 7.8 mm in total length (TL), which were caught at 17°N. The 5.8 mm TL larva was estimated to be 3–4 days after hatching, the youngest preleptocephalus (i.e., the earliest stage) of this species ever collected. Eighteen other leptocephali were caught at 18°N and 21°N, and these ranged from 18.6 to 40.0 mm TL. Based on these collections, we discerned that there is a spawning area of C. myriaster in the area along the Kyushu-Palau Ridge approximately 380 km south of Okinotorishima Island. Similar to the Japanese eel spawning area along the West Mariana Ridge, the Kyushu-Palau Ridge may play an important role as a landmark of the spawning area. The discovery of this offshore spawning area should lead us to a better understanding of the recruitment mechanisms of C. myriaster, and help to facilitate future international management efforts.     

Comparison of Two Environmental Regimes for Culture of Australian Snapper, Pagrus auratus, Larvae in Commercial-scale Tanks

The performance of Australian snapper, Pagrus auratus, larvae from 4 to 33 days posthatch (dph) under two environmental rearing regimes was evaluated in 2000‐L commercial‐scale larval rearing tanks (N = 3 tanks/treatment). The treatments were the following: (1) a varying regime of salinity (20–35 ppt), temperature (24 C), and photoperiod (12 light [L] : 12 dark [D] to swim bladder inflation and then 18L : 06D) and (2) a constant regime of salinity (35 ppt), temperature (21 C), and photoperiod (14L : 10D). The final total length (TL) and wet and dry weights (mean ± SEM) of larvae grown in the varying regime were greater (15.6 ± 0.5 mm; 42.4 ± 3.4 mg wet weight; and 7.3 ± 0.6 mg dry weight) than those of larvae grown in the constant regime (11.1 ± 0.2 mm; 12.9 ± 0.8 mg wet weight; and 2.1 ± 0.2 mg dry weight). By 33 dph, larvae in the varying regime were fully weaned from live feeds to a formulated pellet diet and were suitable for transfer from the hatchery to a nursery facility. In contrast, larvae in the constant regime were not weaned onto a pellet diet and still required live feeds. Neither survival (Treatment 1, 14.2 ± 3.0% and Treatment 2, 13.3 ± 1.9%) nor swim bladder inflation (Treatment 1, 70.0 ± 17.3% and Treatment 2, 70.0 ± 11.5%, by 13 dph) was affected by rearing regime. The incidence of urinary calculi at 7 dph was greatest initially in the varying regime; however, by 19 dph, when larvae were 8.0 ± 0.28 mm TL, very few larvae in this treatment had urinary calculi. In contrast, many larvae in the constant regime had developed urinary calculi and this continued until the end of the experiment. The incidence of urinary calculi was not associated with larval mortality. Extrapolation of the snapper larval growth curves for the constant larval rearing regime predicts that a further 15–18 d, or approximately 1.5 times longer, will be required until these larvae attain the same size and development of larvae reared in the varying regime.     

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.     

Relative importance of gulf and shelf waters for spawning and recruitment of Australian anchovy, Engraulis australis, in South Australia

Gonosomatic indices and egg and larval densities observed from 1986 to 2001 suggest that the peak spawning season of the Australian anchovy (Engraulis australis) in South Australia occurs during January to March (summer and autumn). This coincides with the spawning season of sardine (Sardinops sagax) and the period when productivity in shelf waters is enhanced by upwelling. Anchovy eggs were abundant throughout gulf and shelf waters, but the highest densities occurred in the northern parts of Spencer Gulf and Gulf St Vincent where sea surface temperatures (SST) were 24–26°C. In contrast, larvae >10 mm total length (TL) were found mainly in shelf waters near upwelling zones where SSTs were relatively low (<20°C) and levels of chlorophyll a (chl a) relatively high. Larvae >15 mm TL were collected only from shelf waters near upwelling zones. The high levels of larval abundance in the upwelling zones may reflect higher levels of recruitment to later stages in these areas compared with the gulfs. The sardine spawns mainly in shelf waters; few eggs and no larvae were collected from the northern gulfs. The abundance of anchovy eggs and larvae in shelf waters increased when sardine abundance was reduced by large‐scale mortality events, and decreased as the sardine numbers subsequently recovered. We hypothesize that the upwelling zones provide optimal conditions for the survival of larval anchovy in South Australia, but that anchovy can only utilize these zones effectively when the sardine population is low. At other times, northern gulf waters of South Australia may provide a refuge for the anchovy that the sardine cannot utilize.     

Breeding and larval rearing of the camouflage grouper Epinephelus polyphekadion (Bleeker) in the hypersaline waters of the Red Sea coast of Saudi Arabia

This is the first report on the successful year-round natural spawning and larval rearing of Epinephelus polyphekadion (Bleeker) in captivity and under hypersaline water conditions of 42-43%₀ salinity in the Red Sea coast of Saudi Arabia. Although the fish spawned naturally once or twice a year during 1992-94 culture period, incorporation of cod-liver oil in the broodstock diet during the 1995 culture period enabled the fish to spawn continuously for 2-3 days in each month during March, April, May and August. The egg fertilization and hatching rates also increased during the 1995 spawning period. The egg fertilization rate varied from 90 to 100% with a mean of 96.5 ± 3.38%. The egg hatching rate varied from 70 to 95% with a mean of 83.1 ± 10.12%. The fertilized egg diameter averaged 757.3 ± 37.36 μm. There was a linear relation between the fertilized egg size and the egg hatching rate. The increase in the hatching rate relevant to the egg size was statistically significant (P < 0.01). The egg development time until hatching lasted for 19 h at 29°C. The newly hatched larval size ranged from 1.55-1.71 mm with a mean of 1.65 ± 0.052 mm in total length. The larval growth was slow in the early stages and the growth curve until metamorphosis showed a curvilinear pattern. Wide variations in larval size, range 22-47 mm with a mean of 33.40 ± 7.01 mm, were observed during the metamorphosis stage at day 50. No significant difference (P > 0.05) in growth and survival was observed between the larvae reared using white and grey coloured tanks. The larval survival up to metamorphosis was 1.6-4.7% with a mean of 2.98 ± 1.56% in the grey coloured tanks and 1.6-1.9% with a mean of 1.73 ± 0.16% in the white tanks. The results demonstrated the possibility of breeding E. polyphekadion under captive culture conditions. However, methods to improve the larval survival have to be pursued further for commercial farming of this species.     

Winter longitudinal variation in the body size of larval fishes in the Seto Inland Sea,Japan

This study revealed the spatial variation in abundance and body size of larval fishes in the Seto Inland Sea, Japan, in January 2014 and 2015. Fish larvae were collected by a 1.3-m-diameter ring net towed at the surface and at 10-m depth at 21 stations. The most dominant species was the sandlance Ammodytes japonicus, constituting 82% of total larval fish caught. The body size of A. japonicus was greater [ca. 9 mm total length (TL) in 2014] in eastern areas than in western areas (ca. 5 mm TL in 2014). This trend was also observed in rockfishes (Sebastiscus marmoratus and Sebastes inermis species complex), suggesting a common phenomenon in this region. Because the water temperature was lower in eastern areas, it is likely that the longitudinal differences in larval body size are attributable to earlier spawning in eastern areas caused by different temperature conditions.     

Embryonic and larval development of black skirt tetra (Gymnocorymbus ternetzi,Boulenger, 1895) under laboratory conditions

The embryonic and larval development of black skirt tetra, Gymnocorymbus ternetzi, are described under controlled laboratory conditions. In addition, major histomorphological changes and the allometric growth patterns during larval development have been described. The laboratory‐reared broodstock, that is 1 year of age, were spawned. Hatching occurred 20–21 h after spawning at 24 ± 0.5°C. The cleavage was finished in 2 h and the early blastula stage occurred at 2:04 hours after spawning. The gastrulation started at 3:20 hours and 30% epiboly was observed at 3:34 hours after spawning. Eight‐somite stage was observed at 08:33 hours. And embryonic developmental stage was completed at 21 h after spawning. The newly hatched larvae were 1442 ± 14.3 μm in mean total length (TL). The mouth opened at 3 days after hatching (DAH). The yolk sac had been totally absorbed and the larvae started to swim actively within 3–4 days. Notochord flexion began at 11 DAH. The metamorphosis was completed and the larvae transformed into juveniles at 32 DAH. In this paper, the full developmental sequence from egg to juvenile of G. ternetzi is described for the first time.     

Sperm quality analysis of normal season (NG) and out-season by photoperiod manipulation (PG) of male rainbow trout broodstock (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

Sperm quality parameters in rainbow trout (Oncorhynchus mykiss) were investigated during normal season spawning (November–January) and out-season spawning (July–August) treated with artificial photoperiod manipulation. Normal spawning males (n?=?15) were kept in an open concrete pond under natural condition. Out-season spawning males (n?=?15) were treated with artificial LED light (50 lm/m²) in a closed concrete pond. In these two experimental groups, five fish were used in each of three spawning periods. The mean weight and body length of males (2?+ years, n?=?30) were 1213.43?±?39.43 g and 45.08?±?0.62 cm, respectively. Sperms were collected from July to August 2016 in the out-season spawning or photoperiod-manipulated group (PG) (water temperature 14.21?±?0.31 °C) and from December 2016 to January 2017, in the normal season spawning group (NG) (water temperature 8.81?±?1.03 °C). Volume of sperm, osmolality of seminal plasma, density of sperm, percentage of motile spermatozoa (MOT), curvilinear velocity (VCL), and duration of motility were measured for each male. Seminal plasma osmolality, density of sperm, and the motility of duration were 358.47?±?37.24 and 308.87?±?44.09, 4.37?±?2.10 and 9.8?±?1.56, and 8.8?±?2.42 and 24.6?±?6.76 in PG and NG, respectively. Fertilization rate was 37.79?±?9.37% and 94.51?±?1.33% in PG and NG, respectively. Sperm quality parameters showed significant differences in most of the cases (p?<?0.05) and fertilization rate at eyed egg stage (150–160 degree-days) was significantly higher in normal season spawning group than the photoperiod-manipulated group (p?<?0.05). Though the rate of fertilization was low in out-season, it was able to get enough gametes in summer using only artificial light having no changes in other parameters.     

大竹蛏生产性人工繁育试验

2007年对大竹蛏进行了生产性人工繁育试验。对亲本不同批次催产效果、不同规格亲本产卵差异、孵化密度进行了比较,研究了D形幼虫发育与温度的关系以及幼虫发育各阶段生长规律等,结果显示,大竹蛏属分批成熟、分批产卵的潜居性贝类,不同批次个体平均产卵量(36~118)×104cell,个体总产卵量294×104cell。壳长8~10 cm的亲贝产卵量大,催产效果好。受精卵适宜的孵化密度为5~10 cell/mL。在水温21~24.5℃条件下,D形幼虫经8~5 d生长,发育变态为附着稚贝。D形幼虫壳长日生长33.33±4.22μm,1 mm前的稚贝壳长日生长108.33±22.57μm,1~10 mm的稚贝平均旬生长量2.12 mm,10.4~30.6 mm的苗种平均旬生长量为2.02 mm。当水温下降到15℃后,大竹蛏苗种生长滞缓。2007年培育出壳长11.52±0.27 mm的稚贝2 165×104cfu,平均成活率12.1%。     

The Scale‐up of Spotted Rose Snapper,Lutjanus guttatus,Larval Rearing at Mazatlan,Mexico

The scale‐up of spotted rose snapper, Lutjanus guttatus, larval rearing is described. Fertilized eggs (480,000) were obtained from a 1‐d harvest of a natural spawning captive broodstock acclimatized for 1 yr and 6 mo in two fiberglass tanks (18 m³). Fourteen hours after spawning, 89.6% of the collected eggs were floating, of which 96.2% were transparent with live embryos. Incubation at 25–26 C lasted 21 h, with 90.2 ± 2.1% hatching percentage of normal larvae. The percentage of viable larvae at 48 h after hatching was 79.7 ± 1.9%. Initial stocking density was 10.4 ± 1.0 larvae/L 2 days after hatching (d.p.h.). A total of 22,600 juveniles (1256 ± 170 juveniles/m³) were harvested from six 3‐m³ cylindrical fiberglass tanks. Average survival was 12.1 ± 1.1%. Final mean length and weight were 5.5 ± 0.05 cm and 2.24 ± 0.04 g, respectively. Growth expressed in total length was TL = 2.1476e^0.0543t (R² = 0.9911). Final mean biomass and condition factor were 2.8 kg/m³, 12.3% and 1.346. General length‐weight ratio was W = 0.05460 LT^2.2306.     

Estimating reproductive success of brooders and heritability of growth traits in Asian sea bass (Lates calcarifer) using microsatellites

Asian sea bass (Lates calcarifer) is one of the most important marine food fish species in Asia and Australia. To estimate the reproductive success of broodstock and heritabilities of growth‐related traits, two independent full‐factorial crosses (PI and PII) were created by crossing 10 males and 10 females. At 90 days post hatch (dph), the body weight (BW) and total length (TL) of 804 individuals from PI and 900 individuals from PII were measured and tissues samples of each fish were collected. Parents and offspring were genotyped with nine polymorphic microsatellites. Out of 1704 offspring from the two crosses, 98.7% were assigned to their parents. In PI, 19 of 20 parents produced offspring, while in PII, only five parents contributed to offspring. Low contribution of parents to offspring could lead to reduced genetic variation in the next generation. Heritabilities for growth‐related traits were estimated using the pedigrees reconstructed using microsatellite genotypes. The estimates of heritability were 0.22±0.16 and 0.25±0.18 for BW, 0.31±0.14 and 0.24±0.21 for TL and 0.22±0.22 and 0.15±0.09 for Fulton's condition factor in the two crosses respectively. Body weights at 90 dph and at harvest (289 dph) were significantly correlated (r=0.601, P<0.01). Therefore, growth‐related traits could be improved by exploiting additive genetic effects through selective breeding, and broodstock candidates could be selected early in the production cycle.     

In situ growth and mortality of juvenile Acropora over 2 years following mass spawning in Sekisei Lagoon,Okinawa (24°N)

The growth of Acropora in Sekisei Lagoon was investigated in situ using ceramic coral settlement devices (CSDs) and marine blocks (MBs) with small holes on their surfaces that were deployed prior to a mass spawning event. Acropora that had settled in 10-mm holes on the upper surface of the MBs were found to have grown inwards after 348 days post-mass spawning. After 733 days, the colonies had grown outwards, encrusting the blocks and attaining a maximum diameter of 21.5 mm (3.7 mm). CSDs that had been stacked above each other on frames were separated and observed in situ on 405 and 764 days after mass spawning. After 405 days, the maximum diameter of the encrusting Acropora was 7.6 mm (±2.4 mm), which increased to 19.4 mm (±5.5 mm) after 764 days, with 30% of colonies extending short branches. The length of the branches of Acropora grown on the CSDs fixed to the MBs 3 months after the mass spawning event exceeded the size of the encrusting portion of the colony 629 days after spawning. The mortality of colonies between 1 and 2 years was slight, with the temperatures conducive to coral bleaching that occurred during the study also having only a slight effect.     

Effects of three cold weather event simulations on early life stages of Southern Flounder (Paralichthys lethostigma)

ABSTRACT

To determine the minimum age/size at which Southern Flounder, Paralichthys lethostigma, can safely be moved to outdoor rearing facilities in Texas, we examined survival of simulated temperature drops in two distinct life stages: premetamorphic larvae and two size classes of postmetamorphic juveniles (small = 9.8 ± 0.3 mm in TL; large = 19.7 ± 0.6 mm). Temperature was lowered by ?0.33°C/h to 4°C, 7°C, or 10°C, held for 48 h and then raised at +0.33°C/h back to normal rearing temperature. Fish were monitored daily for survival. Larger postmetamorphic flounder had high survival for all temperature treatments (89%–100% survival), whereas both premetamorphic larvae and smaller postmetamorphic juveniles had low survival (<30%) for all temperature treatments.     

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.     

The pseudo-green water technique for intensive rearing of sea bream (Sparus aurata) larvae

The “pseudo green water” technology for sea bream(Sparus aurata) larval rearing was evaluated by analyzingresults of a 2-year study, performed in a pilot scale system. Thetechnology is characterized by the daily addition of phytoplankton in therearing tanks during the first month of rearing. Effects of egg origin,spawningseason and initial larval density on the larval rearing were investigated. Fishreared in “pseudo green water” systems for 60 days, presented highbiological performance in terms of survival (56 ± 16%), meanweight (62 ± 12 mg), total length (20 ± 1mm), conformity with wild standard (88 ± 9%), andfunctional swim bladder (93 ± 4%). The results present homogenitybetween the categories (origin of eggs, time of spawning, initial egg density)studied, proving the stability of the technology.     

Effect of geographic origin, temperature and timing of broodstock collection on conditioning, spawning success and larval viability of Ruditapes decussatus (Linné, 1758)

Culture of Ruditapes decussatus is clearly limited by the availability of seed, as this production proceeds almost exclusively from natural recruitment. Artificial spawning and larval rearing programs could provide an alternative source of spat. This study was designed to evaluate the effect of different conditioning temperatures on the broodstock maturation, spawning success and larval viability of two geographically (north and south of the Iberian Peninsula) distinct populations of European clam (R. decussatus) collected at different periods of the year in order to create “optimal” artificial spawning and larval rearing programs. Two batches of clams from each population were collected in October and February, and conditioned at 18 ± 1°C, 20 ± 1°C and 22 ± 1°C. Of the three variables analysed the timing of broodstock collection was the most determining factor for gametogenic development, spawning and larval rearing. Geographic origin and conditioning temperature also greatly affected the spawning. The results also showed that the February conditioning was more effective than October and that the best conditioning temperatures were 20 ± 1°C and 22 ± 1°C for the northern and southern populations, respectively. These results suggest that the efficient conditioning temperature for each population of the same species is related to the seasonal temperature regime from their geographic origin. Larval viability and growth performance seemed to be independent of the broodstock conditioning.     

Occurrence and distribution during the post-settlement stage of two Choerodon species in shallow waters around Ishigaki Island, southern Japan

The recruitment patterns of black-spot tuskfish Choerodon schoenleinii were compared with those of orange-dotted tuskfish (OT) C. ancholago. Individuals at the settlement and juvenile stages were collected using a push net in the intertidal zone and a seine net in seagrass beds. Relative values of standard length to total length (TL) for the two Choerodon species indicated an inflection point at approximately 10?C20?mm TL, suggesting that both species complete metamorphosis at a similar size. However, their temporal and spatial occurrence patterns were distinct. Newly settled individuals (postflexion stage) of black-spot tuskfish were collected mainly within foliage of Sargassum plants of the intertidal zone around March?CApril, while those of OT occurred in both the intertidal zone and seagrass beds mainly in May and June. In seagrass beds, the abundances of both species increased from May or June; however, the TL of black-spot tuskfish was bigger than that of OT. Therefore, black-spot tuskfish progressively migrate to seagrass beds after settling and completing metamorphosis in the intertidal zone, indicating that they utilize two different habitats as nursery grounds. Early spawning and migration from the intertidal zone by this species contributed to the occurrence of relatively large individuals in seagrass beds.