Spatial variation in the annual reproductive cycle of Turbo (Batillus) cornutus (Gastropoda: Trochidae) at Jeju Island,Korea

The annual reproductive cycle of the top shell Turbo cornutus from Jeju Island was investigated in two populations using histology. In the northern population, gametogenesis commenced in January as the surface water temperature reached 14?°C, while in the southern population gametogenesis began a month earlier, as the water temperature remained at 17?°C. Ripe top shells first appeared in June and spawning continued from June to October when water temperatures were between 20 and 24?°C. Histology indicated that the spawning period of the southern population was a month earlier and lasted longer (June–October) than in the northern population (July–September). The percentage gonad area of animals in the southern population in March and April was significantly higher than in the northern population (p?相似文献   

Growth of larval Pacific anchovy Engraulis japonicus in the Yellow Sea as indicated by otolith microstructure analysis

Larval Pacific anchovy Engraulis japonicus were sampled from coastal waters off the central west coast of Korea from June to November 1996. Using otolith microstructure analysis (daily growth increments), three cohorts (spring, early summer and late summer) were distinguished based on backcalculated spawning dates. Growth rates differed between cohorts, with higher growth rates for late-summer cohorts than either the spring or early-summer cohorts. Growth rate was positively related to surface water temperature, with an optimum temperature range of between 20 and 26° C occurring during the late summer (late July through to mid-September). The study highlights that early growth rates of Pacific anchovy are dependent on ecosystem (particularly water temperature) attributes during early life.     

Reproduction of an alien Ruditapes clam (Bivalvia: Veneridae) on recreational clam-gathering grounds in Tokyo Bay,Japan

The Manila clam Ruditapes philippinarum is an important fisheries resource and popular recreational native species in Japan. To counter the domestic shortage of Manila clams caused by depleted catches, similar clams were introduced into Japan from China and the Korean peninsula. The introduced clam is an unnamed morph closely related to R. philippinarum that originates from southern China. Its shell is morphologically different from that of the typical Manila clam and there are small but distinct genetic differences. There is evidence to suggest that the Chinese morph may hybridize with the Manila clam in the Ariake Sea, but not in Tokyo Bay. We carried out studies to determine the degree of overlap of the breeding seasons of both taxa by collecting samples of the Manila clam and the alien clam released onto recreational clam-gathering grounds in Tokyo Bay and their gonadal maturity was examined histologically. Spawning-stage individuals of the Manila clam appeared from April to August and those of the southern Chinese morph from July to August, indicating overlapping spawning periods and thus the potential for hybridization. We discussed the forming condition of the hybridized clam population in terms of reproduction and recruitment process of the clams.     

Growth statistics of an exploited razor clam (Ensis siliqua) bed at Gormanstown,Co Meath,Ireland

A clam bed of 21 km² was discovered at Gormanstown on the East coast of Ireland in 1997. Between July 1998 and August 1999, dredge samples were collected from vessels fishing there and these provided material for biological analysis. E. siliqua occurs with an inshore invertebrate fauna; occasional occurrences of large numbers of Donax vittaus, Pharus legumen and Lanice conchilega were associated with razor clams of less than 6 cm long. As harvesting proceeded smaller individuals appeared in the samples; these may have immigrated onto the bed from the periphery of high densities of larger clams. On the clam bed the animals ranged from 0+ to 19+ years old. Ensis siliqua grew at a slower rate on the west coast of the Irish Sea than on the coast of North Wales. Males grew slightly faster and longer than females and males were more numerous in the landings. The clams are estimated to commence maturation at approximately 4 years of age. They have a similar gonadal cycle to those in Portugal and a similar spawning period from mid-May to the end of July or early August. Condition reflects gonad development, reaching a peak in May. Harvesting by hydraulic dredging causes breakages which are higher in quarters 1 and 4 than in quarters 2 and 3. Bruised razor clams do not eliminate sand in desanding tanks and so they are rejected by processors. The total biomass of the Gormanstown bed is estimated at approximately 1500 tonnes of which 2/3 had been removed by July 1999, two years after exploitation commenced.     

Prevalence and infection intensity of the ovarian parasite Marteilioides chungmuensis during an annual reproductive cycle of the oyster Crassostrea gigas

The occurrence of Marteilioides chungmuensis, a protozoan paramyxean parasite in the reproductive system of the Pacific oyster Crassostrea gigas, was observed at Gosung Bay, Korea. Seasonal variation in gonad development was investigated in a suspended cultured oyster population. Gametogenesis began in February and first-spawning was observed between mid and late June when surface water temperature reached 22 to 25 degrees C. Spawning activity extended from mid June to late September, with 2 marked spawning peaks in June and August. Histological examination indicated that gonad development paralleled seasonal fluctuations in water temperature. Spawning in late June was partly associated with a sudden drop in salinity due to large freshwater inputs to the Bay with the summer monsoon. M. chungmuensis occurred in developing and fully mature eggs of spawning oysters in late June to January, but were not observed from February to May. Monthly mean infection intensity was high in late June when most oysters had their first spawning period. The infection level was also relatively high in late August and November, when oysters were spawning or had completed spawning. Several oysters collected in November (11.4%) and December (16.3%) carried a large quantity of ripe but M. chungmuensis-infected eggs, suggesting that infection also causes spawning failure by delaying spawning and destroying ripe oocytes.     

The bimodal adult activity of Monochamus alternatus (Coleoptera: Cerambycidae) caught in pheromone traps in Jeju can be explained by the competitive attractiveness of dying pine trees

The Japanese pine sawyer, Monochamus alternatus Hope (Coleoptera: Cerambycidae), is known to be the primary vector of pinewood nematode Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle that causes pine wilt disease. Adult activity of M. alternatus caught in a pheromone trap on Jeju Island of Korea showed a bimodal form with the first peak in mid to late June and the second peak in mid to late September. The two peaks were separated between mid and late August, showing a valley. Accumulated degree‐days predicted that the emergence of the second generation adults could be possible just before the second peak. But actually no adults of the second generation occurred in the field development experiments of M. alternatus in 2016 and 2017. Pine trees without oleoresin flow (namely dying trees by the infection of pinewood nematode) were abundant during early July to early August. The bimodal adult activity pattern of M. alternatus could be partially explained by the competitive attractiveness of dying trees against pheromone traps, when we accepted the assumption that dying pine trees attract strongly M. alternatus.     

Age and growth of tarpon,Megalops atlanticus,larvae in the eastern Gulf of Mexico,with notes on relative abundance and probable spawning areas

Synopsis Leptocephali were collected in June 1981 and July 1989 over the continental shelf and slope of the Florida west coast. Tarpon larvae ranged 5.5–24.4 mm standard length (SL) and were the second most abundant leptocephalus species. Sagittae examined with compound microscopes and scanning electron microscopy had increments that were presumed to be formed daily. Increment counts made using the two microscopic techniques were not significantly different. Estimated ages ranged 2–25 days with a growth rate (± standard error) of 0.92 ± 0.04 mm d^–1 The least squares linear regression equation SL = 2.78 + 0.92 (age in days) best described the relationship between estimated age and length. Adult tarpon appear to undergo a substantial spawning migration from inshore areas frequented during spring and summer to offshore spawning grounds. Spawning occurs during May, June, and July, although the spawning season may be of greater duration.     

Effect of spawning ground location on the transport and growth of chub mackerel (Scomber japonicus) eggs and larvae in the East China Sea

Chub mackerel (Scomber japonicus) are an important pelagic fish species within the China Sea. Annual recruitment of this species is determined primarily by survival in the early life history stages. Minor changes in the physical marine environment can have a significant effect on the growth and survival of eggs and larvae, thereby affecting recruitment of population. To model this interaction, we constructed a bio-physical dynamic model of the early life history of chub mackerel in the East China Sea (ECS). The physical model was based on the unstructured grid Finite Volume Coast and Ocean Model (FVCOM) and simulated the 3-D physical fields. The biological model was based on individual-based models (IBMs) in which the early life stages of chub mackerel were divided into five stages based on age or length. The model was parameterized using functions describing spawning, growth, and survival for chub mackerel in the ECS. Using this coupled physical and biological model, driven by the March–July climatological forcing, we tracked super individuals from spawning grounds to the nursery grounds to evaluate the influence of the physical environment at each of the spawning locations (western, normal, eastern) on the transport and survival of chub mackerel. The model suggests that spawning location has a significant effect on larval transport, although the larvae were generally advected northeastward to enter the Japan/East Sea through the Tsushima/East Strait or southeastward with the Kuroshio Current which then flows along the eastern Japanese coast. Spawning to the west was highly influenced by the Taiwan Warm Current (TWC) during early transport when the larvae were advected northward and then northeastward. The speed of drifting during this period was relatively slow. The model predicted that a large number of eggs and larvae would enter and transit through China’s coastal waters (Changjiang River Estuary, Hangzhou Bay, and the Zhoushan Islands). Under this scenario, the majority of larvae were transported to the northern nursery grounds, 79% to the nursery at Jeju Island and 10% to the nursery at Tsushima Strait. In contrast, only 11% were transported to the southern nursery grounds in the Pacific Ocean and Kyushu. Larvae spawned at the eastern spawning ground were primarily influenced by the Kuroshio Current which transported the larvae southeastward. Kuroshio acts as a barrier, restricting larvae from being advected to the interior of the western Pacific Ocean. Under such circumstances, almost no eggs and larvae were retained in the coastal waters of China. Instead, the larvae were rapidly transported northeastward from the Chinese shelf towards the coast of Japan. The model predicted that a large number of larvae would be transported to the southern nursery grounds in the Pacific Ocean and Kyushu, before entering the Pacific Ocean and Japan Sea. In total, 36% of larvae were transported to the Pacific Ocean nursery, 45% to the northern nursery grounds of Jeju Island and Tsushima Strait, and 27% to the Jeju Island nursery. The three simulations assumed the same number of eggs were spawned (2.17 × 10¹²) and the survival of larvae at the western, normal, and eastern spawning grounds was 0.0306%, 0.0353%, and 0.0234%, respectively. The average length was 123.7, 126.0, and 123.5 mm, respectively. Our results suggest that larvae spawned in different regions encountered different physical environments and were subject to different transport processes. These differences explain the changes in survival and growth observed between larvae from the different areas. Survival and growth was highest for chub mackerel that were spawned at the normal spawning location and subject to suitable water depths and temperatures during transport.     

Enzyme-linked immunosorbent assay (ELISA) used in quantification of reproductive output in the pacific oyster,Crassostrea gigas,in Korea

Polyclonal antibody developed from egg proteins of the Pacific oysters, Crassostrea gigas, was used in quantification of the eggs. Quantity of the egg protein was measured using ELISA and a weight-normalized gonadosomatic index (GSI) was then established. Histology indicated that the oysters collected from Goseong Bay, Korea, in 2000 initiated gametogenesis as early as late February and spawned mostly in late June to early July when water temperature reached 23–25 °C. A second spawning peak was also observed in late August and the spawning activity continued to late October. Oyster egg proteins could be detected by ELISA in all months except March and November; a few oysters collected during December and January contained a measurable amount of eggs. The highest monthly mean GSI, 0.423, was observed in mid-June when the oysters were ready to spawn. The maximum GSI recorded in this study was 0.667. A positive correlation was found between oyster size and fecundity; the number of eggs increased as oyster biomass increased (r²=0.7497). Our data suggest that oysters in Goseong Bay produce 3–196 million eggs during the spawning season. The immunological method developed in this study was sensitive enough to measure a small quantity of eggs and considered to be method of choice for studying bivalve reproduction.     

Molting phenology of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the Baja California Peninsula,Mexico

We document and compare the annual molt of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the west coast of the Baja California Peninsula that are the northern and southern extremes of its distribution in Mexico. During 2014, observations were made from March to July on Todos Santos Island (northern extreme) and from January to June on San Roque Island (southern extreme). On Todos Santos, the premolt lasted 15 wk (March–June) and the molt 12 wk (April–July). On San Roque, the premolt lasted 22 wk (January–June) and the molt 17 wk (February–June). The proportion of seals undergoing molt peaked on 26 May on Todos Santos and on 7 June on San Roque. Shedding of old hair most commonly initiated on the torso and progressed to the head and flippers (reverse molting pattern). The period when the highest number of harbor seals haul out in Mexico is in late April on the more southerly islands and in early May on the more northerly islands, when a large proportion of seals are in premolt.     

Semilunar spawning cycle of the humbug damselfish Dascyllus aruanus

A very distinct semilunar spawning cycle was found in a population of the damselfish Dascyllus aruanus on the coral reefs of Sesoko Island, Okinawa. Spawning occurred from June to September, only in the early morning, during a period of 2–4 days immediately before or around the time of the new and full moon. Males cared for the eggs deposited on the substrate for 2.5 days until hatching. Hatching occurred just after sunset, i.e., at the high tide of spring tide; the strong ebb current then would rapidly disperse the newly hatched larvae offshore. Females tended to synchronize spawning in a male's nest, also because multiple clutches in a nest would be more likely to survive until hatching. Thus, the distinct semilunar spawning cycle may favor females in reducing mortality of both eggs and larvae. Received: July 9, 1999 / Accepted: January 29, 2000     

Summer spawning of Porites lutea from north-western Australia

Most coral species off Australia??s west coast spawn in the austral autumn (March?CApril), with a few species also spawning in the southern spring or early summer (November?CDecember). This is the reverse timing to spawning recorded off Australia??s east coast. Porites lutea, a gonochoric broadcast spawner that is common on Australia??s west coast, is shown here to spawn in the months of November or December, as it does on Australia??s east coast. Spawning occurred between 2 and 5 nights after full moon, with the majority of spawning activity on night 3. Gametes developed over three to four months with rapid development in the last two weeks before spawning. Zooxanthellae were typically observed in mature oocytes, only a week before spawning so their presence may provide a useful indicator of imminent spawning.     

Promiscuous spawning behaviour of the tropical herring Spratelloides gracilis

Spawning behaviour of the blue sprat Spratelloides gracilis was observed at shallow reefs of Kuchierabu‐jima Island, southern Japan. The fish carried out promiscuous spawning behaviour on substrata covered with algal mats mainly in the intertidal region of a shallow inlet. The spawning events occurred only at predawn (20–50 min before sunrise) and daily for c . 25 days from mid‐June to mid‐July.     

Reproductive cycle and releasing time for increase of resource of adult sea cucumber Apostichopus japonicus released to seed breeding grounds

The reproductive cycle and releasing time for effective increase of resource of adult sea cucumber (Apostichopus japonicus) have been studied in the west coast of Korea. Adult sea cucumbers collected in Seocheon-gun April 2013 for first release and in the uncontaminated Taean-gun area in the west coast of Korea. Divers monthly collected the specimens in the released area from December 2013 to November 2014 in order to investigate the reproductive cycle of A. japonicas in Taean-gun. Random specimens were dissected to examine the gonadal developmental stages and discharge rates of the guts and gonads. The reproductive cycle of A. japonicus in both sexes are classified into the following six successive stages in the Taean-gun: (1) Stage I (recovery stage from December to February), (2) Stage II (early growing stage from February to March), (3) Stage III (late growing stage from March to April), (4) Stage IV (mature stage from April to July), (5) Stage V (partly spawned stage in July), and (6) Stage VI (spent stage from August to November). The estivation period of this species is from July to October in the Taean-gun region while surface water temperature is approximately 20–25.4°C. Thus, the optimum period to easily harvest them is from October to November in the uncontaminated Taean-gun area. It is also the best releasing time because the recovery stage starts from December to February in the Taean-gun region.     

Cultivation of a brown alga, <Emphasis Type="Italic">Undariopsis peterseniana</Emphasis> (Kjellman) Miyabe and Okamura,as a warm-temperature species by artificial seed production in Korea

Undariopsis peterseniana is an endangered annual brown alga in Udo, Jeju Island, Korea. There is current interest in the commercial-scale aquaculture of this species for warm-water species development in Korea. Growth and maturation were investigated from January to December 2007 in their natural habitat. Zoospores were transplanted into an intensive seaweed culture ground in Wando, southern coast of Korea, for the mass cultivation of this species. Indoor and outdoor cultivation were conducted from June 2007 to May 2008. Mean production obtained from the zoospore seeding was 31.1 ± 1.5 kg wet wt. m⁻¹ of culture rope during the cultivation period in situ. Transplanted F₁ thalli in Wando had a length 1.7 times longer than their parents in Udo, and their maximal growth period changed from June (at 19.9°C in Udo of natural habitat) to April (at 14.0°C in Wando of culture ground). The relationship between optimal water depth for culture and underwater irradiance during the U. peterseniana cultivation was defined as: y = - 0.78 ×+ 7.67( r² = 0.92 ) y = - 0.78 \times + 7.67\left( {{r^2} = 0.92} \right) . This study indicates that U. peterseniana could be successfully transferred to the northern coast beyond the original habitat in Jeju Island.     

Mass spawning of Caesio teres (Pisces: Caesionidae) at Enewetak Atoll,Marshall Islands

Synopsis Mass spawning of Caesio teres occurred between March and August, 1983 on a reef emerging from deep water just inside the East Channel of Enewetak Atoll, Marshall Islands. Aggregations and spawning were observed from one day before until three days after the full moon. Spawning aggregations were not observed during the new or quarter moons. Spawning commenced after high tide, when the current began to flow out the pass from lagoon to ocean. The spawning aggregation of close to 1000 individuals migrated to the spawning site. Spawning occurred when the aggregate ascended to near the water's surface. Subgroups dashed horizontally within the aggregate, releasing a highly visible gamete cloud. Predation on spawning adults was not observed. Predation on spawned eggs was noted. The eggs of C. teres are described. Mid-Pacific Research Laboratory, Enewetak Atoll, Republic of the Marshall Islands Present address: Motupore Island Research Station, P.O. Box 320, University of Papua New Guinea, Papua New Guinea     

REPRODUCTIVE PERIODICITY OF THE SEA URCHIN,TRIPNEUSTES GRATILLA (L.) IN TAIWAN COMPARED WITH OTHER REGIONS

An annual reproductive periodicity of Tripneustes gratilla in northern Taiwan is revealed by both the gonad development stages and the gonad index. The gonads of T. gratilla recovered from spawning in February—March, propagated gametocytes in April—June, came to prematurity in July—August, and matured in September—November. Spawning occurred in October—December. The breeding pattern of T. gratilla over a broad geographical area appears to be related to seasonal changes of sea temperatures.     

The seasonal changes in somatic energy content of Gulf of Alaska yellowfin sole, Pleuronectes asper

Seasonal measurement of body energy content was made for Pleuronectes asper (Pallas, 1814) from the Gulf of Alaska. Whole body energy content of complete fish (～ 3472 J g^?1 wet wt) was minimal in May for females as their overwintering phase ended, then increased to ～ 4456 J g^?1 prior to spawning. The ovarian index [(g.w./t.w.) × 100] and energy content of ovaries (J g^?1) was highest in June and May respectively, and then declined markedly by August as spawning occurred. Throughout the year male whole body energy content of complete fish ranged from 3351 to 4590 J g^?1 with the lowest values in May and highest values occurring during June to September, the feeding season. The testes index [(g.w./t.w.) × 100] and total energy content of testes (J g^?1) were high in March and lowest during June and July. On a weight-specific basis, males and females had similar whole body energy values throughout the year. Juveniles followed the same seasonal trends in energy storage as adults and had similar whole body energy values. Whole body energy content was linearly related to wet and dry weight condition factor with r² values of 0.70 and 0.87, respectively. Dry body weight as percent of wet body weight was the best predictor of body energy (r²=0.91). Yellowfin sole had an annual energy cycle with energy accumulation and growth from May to September. Thereafter they utilized stored energy for metabolic and reproductive needs. Spawning began in late May or early June and fish were spent by August. Whole body energy content increased by 28, 33 and 35% between May and June, for females, juveniles, and males, respectively, the most dramatic change during the year long survey. This suggests that intense feeding in May must be an important aspect of their energy storage cycle.     

Reproductive characteristics and gamete development of the soft coral Sclerophytum cf. heterospiculatum in Okinawa Island,Japan

Sexual reproduction data are important to understand how organisms can replenish their populations and proliferate on coral reefs. Despite the importance of such data, the reproductive characteristics of most soft coral species are still unknown. Here, we examined the reproductive strategies of a species from the often-dominant genus Sclerophytum in a coral reef on subtropical Okinawa Island, Japan. DNA barcoding and histological examinations of the tissues were conducted to confirm colony conspecificity and identify reproductive characteristics, respectively, between March 2020 and March 2021. Results indicated that the studied species, identified as Sclerophytum cf. heterospiculatum, exhibits gonochorism with longer oogenesis and shorter spermatogenesis. Female colonies produced immature oocytes throughout the year, with mature oocytes observed from late July to early September, and thus, extended spawning is likely characteristic of this species. In male colonies, spermatogenesis took place over ~5 months, with spermaries present from April through August. Mature spermaries were noted beginning in July and the inferred peak of sperm release was between late August and early September, which suggests that spermatogenesis duration was ~5 months. The largest mean oocyte and spermary sizes (628.45 ± 61.36 and 240.04 ± 49.49 μm, respectively) were both recorded in August. Gamete spawning presumably occurred during the summer season, which suggests seasonality in reproduction as influenced by changes in seawater temperature. However, the proximate cue for exact dates of spawning could be the lunar period because the inferred release of spawning materials seemed to occur between full moon and last-quarter moon phases in both the months of August and September. The results of this study represent the first detailed report of reproductive characteristics of the genus Sclerophytum in Japan.     

Predation on fish eggs by white perch,Morone americana,in western Lake Erie

Synopsis The white perch,Morone americana, is an east coast estuarine species that invaded Lake Erie in the 1950's, but did not increase in abundance until the mid 1970's. We studied its distribution and feeding during spawning in the Sandusky River, Ohio in 1981–1983. White perch were present in the area from early April through May, but abundance was highest on bedrock riffles about 45 km upstream from Lake Erie. Spawning activity peaked in the last week of April when temperatures approached 18°C. White perch collected in early April had eaten walleye,Stizostedion vitreum vitreum, eggs. As spawning activity of white perch increased, feeding activity declined, and most fish collected during late April contained no food. Egg predation increased again in May, but the eggs eaten then were those of white bass,Morone chrysops, white perch, and possibly other species. We have no evidence that egg predation by white perch has affected walleye or white bass recruitment, but it could become a problem if white perch continue to increase in abundance.