The estuarine tapertail anchovy(Coilia nasus)is a high-value commercial fish.Estimating the spawning site or hatchery origin and habitat is essential for its conservation.This study aimed to determine the habitat use ...The estuarine tapertail anchovy(Coilia nasus)is a high-value commercial fish.Estimating the spawning site or hatchery origin and habitat is essential for its conservation.This study aimed to determine the habitat use and life history characteristics of C.nasus from the Changjiang River Estuary.We investigated the environmental signatures of strontium(Sr)and calcium(Ca)in the otoliths of the collected specimens using electron probe microanalysis;additionally,we examined their gonadal maturity stage.Our results indicate that the 31 adult C.nasus specimens used in this study could be classified into two types based on their otolith Sr:Ca concentration ratios and their gonadal maturity stage.The long freshwater early life history type(Type LF)had wider central region in the otolith with low Sr:Ca concentration ratios ranging from 1.24±0.62 to 1.92±0.78 and a bluish pattern of low Sr content level.These fish are of riverine origin and had a relatively long early life history in freshwater and low gonadal maturation when captured.The short freshwater early life history type(Type SF)had a shorter central region in the otolith with low Sr:Ca concentration ratios ranging from 1.35±0.5 to 2.82±0.97 and a correspondingly bluish pattern.These fish also had a relatively short-term early life history in freshwater and high gonadal maturation when captured.The results of the otolith microchemical analysis indicated that Type LF and Type SF originated in spawning/hatching sites far from and close to the estuary,respectively.The mature gonads of Type SF fish indicated that they may breed in areas close to the estuary,whereas the immature gonads of Type LF fish indicated that they may breed in areas far from the estuary.This study is the first to reveal that the Changjiang River Estuary contains stocks of anadromous C.nasus originating in different spawning sites during the same season.The estuarine habitat plays a critical role in the connectivity between freshwater recruitment and the marine resources available to adult spawners of this commercially valued species.From a conservation perspective,this study provides important information for identifying anadromous C.nasus stocks originating in different spawning sites in the Changjiang River Basin.展开更多
Japanese Spanish mackerel Scomberomorus niphonius is a pelagic,neritic species that occurs in the Yellow Sea in high commercial value.The spawning period of this fast-growing species is controlled by water temperature...Japanese Spanish mackerel Scomberomorus niphonius is a pelagic,neritic species that occurs in the Yellow Sea in high commercial value.The spawning period of this fast-growing species is controlled by water temperature.Based on microstructural analysis of otoliths from 145 young-of-the-year(YoY)S.niphonius collected by trawl in 2017,2018,and 2020,and the temporal variation in the spawning period in the northern Yellow Sea,and its relationship to water temperature were examined.We found that the spawning lasted from late April to late June but differed in year:in 2017 it occurred from April 23 to June 1 and peaked in early May,in 2018 it extended later from May 7 to June 29,and in 2020 from May 6 to June 22 and peaked later from late May to mid-June.The highest temperature in 2017 corresponds with the earliest end of the spawning period and a lower growing degree-day(GDD,℃·day)of 383℃·day.In 2018,slower warming corresponds with a longer spawning period,and a GDD spawning period of 506℃·day.Rapid warming in late 2020 corresponds with a spawning peak,and a GDD spawning temperature of 448℃·day.Despite differences in spawning period,the water temperature when spawning commenced was 10-12℃.Therefore,water temperature is the major determinant of the spawning period,affecting both the starting and the ending of spawning.This study improved our understanding of the spawning dynamics and environmental adaptation of S.niphonius,and how these might change in environments subject to increased warming.展开更多
Global Navigation Satellite System(GNSS)-based passive radar(GBPR)has been widely used in remote sensing applications.However,for moving target detection(MTD),the quadratic phase error(QPE)introduced by the non-cooper...Global Navigation Satellite System(GNSS)-based passive radar(GBPR)has been widely used in remote sensing applications.However,for moving target detection(MTD),the quadratic phase error(QPE)introduced by the non-cooperative target motion is usually difficult to be compensated,as the low power level of the GBPR echo signal renders the estimation of the Doppler rate less effective.Consequently,the moving target in GBPR image is usually defocused,which aggravates the difficulty of target detection even further.In this paper,a spawning particle filter(SPF)is proposed for defocused MTD.Firstly,the measurement model and the likelihood ratio function(LRF)of the defocused point-like target image are deduced.Then,a spawning particle set is generated for subsequent target detection,with reference to traditional particles in particle filter(PF)as their parent.After that,based on the PF estimator,the SPF algorithm and its sequential Monte Carlo(SMC)implementation are proposed with a novel amplitude estimation method to decrease the target state dimension.Finally,the effectiveness of the proposed SPF is demonstrated by numerical simulations and pre-liminary experimental results,showing that the target range and Doppler can be estimated accurately.展开更多
Chinese sturgeon(Acipenser sinensis) is the flagship species of the Changjiang River.The migration route of this species is blocked by the first dam,the Gezhou Dam,and its reproduction is affected by the Three Gorges ...Chinese sturgeon(Acipenser sinensis) is the flagship species of the Changjiang River.The migration route of this species is blocked by the first dam,the Gezhou Dam,and its reproduction is affected by the Three Gorges Dam(TGD),one of the largest dams in the world.We studied the impact of the impoundment of the Three Gorges Reservoir(TGR) since 2003 on the spawning stock and the natural reproduction of the Chinese sturgeon by using our monitoring data from 1997 to 2013.Results indicate that TGR impoundment has delayed the first spawning dates of the fish from middle-late October to late November,decreased the amount of spawning activities from twice to only once each year,and significantly reduced egg production.In particular,the fish did not demonstrate any spawning activities in 2013.Therefore,TGR impoundment significantly affects the natural reproduction of the fish downstream of the TGD.The spawning stock size of the fish is also predicted to further decrease in the future,which will lead to a risk of population extinction.Ecological regulations must be imposed on decreasing the water temperature to 20℃before mid-October and increasing water discharge downstream of the TGD in October to induce spawning of the Chinese sturgeon.展开更多
Although amphioxus is widespread in temperate and tropical seas,its population is diminishing be-cause of environmental pollution.To keep the population of this evolutionarily important animal fromdiminishing,study on...Although amphioxus is widespread in temperate and tropical seas,its population is diminishing be-cause of environmental pollution.To keep the population of this evolutionarily important animal fromdiminishing,study on its reproduction and development is necessary.The main findings in this study onthe spawning and fecundity of the amphioxus reared in laboratory and its larval development are as fol-lows.1.Water temperature markedly affected the spawning.It spawned only when water temperature reached 21℃.2.Spawning of the amphioxus in laboratory was markedly extended.Initially,the amphioxus spawned at about 7:00 PM,but spawning time was postponed as spawning days went on.3.The number of eggs produced by a female ranged from 1400 to 12800,average of 5800.This al-so represents the fecundity of the amphioxus because it shedded all eggs within the ovary at a time.4.During the first few months of life of the amphioxus,its growth rate changed seasonally.Thegrowth rate in summer and fall was greater than that展开更多
The distribution of nutrients and the effect of side transport of nutrients on anchovy spawning ground to the southern waters of Shandong Peninsula are discussed based on the data collected in June 2000, May and June ...The distribution of nutrients and the effect of side transport of nutrients on anchovy spawning ground to the southern waters of Shandong Peninsula are discussed based on the data collected in June 2000, May and June 2001. The coastal current and upwelling are the main physical processes of nutrient transport to the southern waters of Shandong Peninsula. The concentrations of nutrients, Chl-a, the density of anchovy eggs, larva and juvenile fish increase obviously where they are greatly affected by these processes, while the contents of nutrients and Chl-a, the density of anchovy eggs, larva and juvenile fish decrease significantly where these processes diminish or disappear. The investigation suggest that the side transport of nutrients by Lubei (North Shandong) coastal current in the northern area causes the Chl-a content to be high and dense anchovy eggs, larva and juvenile fish to be dense in the coastal area of the Chengshan Cape. In the southern area, the riverine input from Subei irrigation ditch with high content of nutrients inshore and upwelling in the western edge of the Huanghai Sea Cold Water offshore should be responsible for high Chl-a concentration and dense anchovy eggs, larva and juvenile fish. It is possible that these processes of nutrient transport have controlled the anchovy spawning ground to the southern waters of Shandong Peninsula.展开更多
In recent years,Konosirus punctatus has accounted for a large portion in catch composition and become important economic species in the South Yellow Sea.However,the distribution of K.punctatus early life stages is sti...In recent years,Konosirus punctatus has accounted for a large portion in catch composition and become important economic species in the South Yellow Sea.However,the distribution of K.punctatus early life stages is still poorly understood.In this study,generalized additive models with Tweedie distribution were used to analyze the relationships between K.punctatus ichthyoplankton and environmental factors(longitude and latitude,sea surface temperature(SST),sea surface salinity(SSS)and depth),and predict distribution K.punctatus spawning ground and nursing ground,based on samplings collected in 6 months during 2014–2017.The results showed that K.punctatus’spawning ground were mainly distributed in central and north study area(from 33.0°N to 37.0°N).By comparison,the nursing ground shifted southward,which were approximately located along central and south coast of study area(from 31.7°N to 35.5°N).The optimal models identified that suitable SST,SSS and depth for eggs were 19–26℃,25–30 and 9–23 m,respectively.The suitable SSS for larvae were 29–31.The K.punctatus spawning habit might have changed in the past decades,which was a response to increasing SST and fishing pressure.That needs to be proved in further study.The study provides references of conservation and exploitation for K.punctatus.展开更多
This study proposes a simulation model that well reproduces the spawning stock biomass of Pacific bluefin tuna. Environmental factors were chosen to estimate the recruitment per spawning stock biomass, and a simulatio...This study proposes a simulation model that well reproduces the spawning stock biomass of Pacific bluefin tuna. Environmental factors were chosen to estimate the recruitment per spawning stock biomass, and a simulation model that well reproduced the spawning stock biomass was developed. Then, effects of various fisheries regulations were evaluated using the simulation study. The results were as follows: 1) arctic oscillations, Pacific decadal oscillations and the recruitment number of the Pacific stock of Japanese sardine were chosen as the environmental factors that determined the recruitment per spawning stock biomass;2) spawning stock biomass could be well reproduced using a model that reproduced the recruitment per spawning stock biomass and the survival process of the population that included the effect of fishing;and 3) the effects of various fisheries regulation could be evaluated using the simulation model mentioned above. The effective regulation in the simulations conducted in this paper was a prohibition of fishing for 0- and 1-year-old fish in terms of recovering the spawning stock biomass. The reduction of fishing mortality coefficients for all age fish to 50% of actual values also showed a good performance. The recent reductions of the recruitment and spawning stock biomass were likely caused by heavy harvesting, especially of immature fish, since 2004.展开更多
Pseudopleuronectes yokamae (Günther) is one of the most important economic fish species in the genus living specially in the northwest Pacific, and is distributed in the southern area of the far east sea of Russi...Pseudopleuronectes yokamae (Günther) is one of the most important economic fish species in the genus living specially in the northwest Pacific, and is distributed in the southern area of the far east sea of Russia, Japan, Korea, the Huanghai Sea, the Bohai Sea and the northern area of the East China Sea. Usually they live in nearshore waters of these areas as geographic subpopulations. P. yokamae in the Sheath Bay belongs to a local group of the Huanghai-Bohai Sea subpopulation and is distributed in the mouth and adjacent waters of the bay all the year round, and the catch of its spawning group has展开更多
The fecundity and spawning locations of rice planthoppers in several rice varieties were surveyed in the test. The results showed that spawning behavior of rice planthoppers obeyed obvious niche distribution; rice pla...The fecundity and spawning locations of rice planthoppers in several rice varieties were surveyed in the test. The results showed that spawning behavior of rice planthoppers obeyed obvious niche distribution; rice planthopper preferred to lay eggs in the leaf sheath with spawning mark distance more than 20 cm, while they liked to lay eggs in the leaves with spawning mark distance of 10 - 20 cm. The average fecundity in leaf sheaths was obviously higher than that in leaves, indicating that leaf sheaths were more suitable for spawning of rice planthoppers than leaves.展开更多
Muricids are commercially important gastropods and are exploited primarily for shell craft industries. They also occupy a niche in ornamental keeping. Studies on the larval development of muricids in Indian waters are...Muricids are commercially important gastropods and are exploited primarily for shell craft industries. They also occupy a niche in ornamental keeping. Studies on the larval development of muricids in Indian waters are few. Hence, an attempt was made to study with a focus on the optimum requirements for captive brood maintenance;regional variation in egg laying, intracapsular development and to estimate production potential of individual brooder (the length/ weight ranged from 80 -?110 mm/49 -?169 g (average 94.875 ± 3.980 mm/111.625 ± 14.870 g) of Chicoreus virgineus var. ponderosa collected off Tuticorin coast, Gulf of Mannar. Experimental airlift water circulation system fitted in 1 t FRP tanks having an overturn of 300% water is found suitable for long term maintenance and maturation of brooders with near cent percent survival over a year. Spontaneous breeding commenced from June ’09. Eggs cases were ‘vase’ shaped and measured 1.2 -?1.5 cm in height. Egg case numbers varied between 110 and 140 and got reduced to 10 -?40 during October and increased in Nov & December. Number of eggs within the egg case was highly variable ranging from 100 -?380. Eggs were spherical, embedded in jelly mass within the egg case and measured 510 -?608 μ (578 μ). Intra capsular development is detailed and compared with the earlier report on this species from other areas of Indian coast. Development took nearly 20 days and only few free living juveniles measuring between 1.7 -?1.9 mm emerged and the rest of the eggs have functioned as “Nurse eggs”. Average net production potential of a single viable egg case was estimated to be 6.7 nos for Chicoreus virgineus var. ponderosa of Tuticorin coast of Gulf of Mannar.展开更多
In order to exploit native fish species for aquaculture, basic parameters of artificial reproducetion and estimates of reproductive potential for this fish must be determined to improve hatchery success. We analyze se...In order to exploit native fish species for aquaculture, basic parameters of artificial reproducetion and estimates of reproductive potential for this fish must be determined to improve hatchery success. We analyze seven Brazilian commercial fish. Spawning was induced using the hypophysation method, with injection of crude carp pituitary extract (CCPE). Characiformes species signaled the spawning time with behavioral alterations (usually circular movements). The time of oocyte extrusion varied from 5.3 ± 0.3 h in Salminus franciscanus to 8.6 ± 0.1 h in Prochilodus argenteus after the second CCPE injection. The greatest diameter of a vitellogenic oocyte was registered for P. argenteus (873.9 ± 122.2 μm) and the smallest was for Pimelodus maculates (465.4 ± 36.3 μm). The diameter of vitellogenic oocytes was very similar among species belonging to the same family. The highest ROI values were registered for Prochilodus costatus(27.0 ± 3.5 μm) and P. argenteus (23.4 ± 3.7 μm), while the lowest values were found in Pseudoplatystoma corruscans (4.6 ± 0.9 μm) and P. maculatus (6.0 ± 1.3 μm). Absolute fecundity (number of oocytes released at spawning) was lowest in P. maculatus and highest in P. corruscans. Relative fecundity (RF) presented a high correlation (r = 0.98 to 0.99) with gonad weight, indicating high efficiency of spawning. The RF also presented a high correlation with body weight (r = 0.88 to 0.97) and total length (r = 0.86 to 0.92). The highest RF was registered for Leporinus obtusidens, and the lowest was for P. corruscans. Released fecundity had a negative correlation with the diameter of vitellogenic oocytes and with the height of the follicular cells, and a positive correlation with the thickness of the zona pelucida. These results indicate that the species studied herein are suitable candidates for aquaculture due to their reproductive and zootechnical characteristics.展开更多
In captive conditions, most neotropical migratory species do not have the necessary incentive to complete gonadal maturation and spawning, which require induction techniques, usually with the use of hormones. Numerous...In captive conditions, most neotropical migratory species do not have the necessary incentive to complete gonadal maturation and spawning, which require induction techniques, usually with the use of hormones. Numerous studies have therefore focused on finding an effective hormonal treatment to induce reproduction for each species. A standard treatment was successfully developed for most of these species, which consists of two doses of Carp Pituitary Extract (CPE), totaling 5.5 mgCPE/kg of fish. However, the best strategy for the subsequent fertilization of gametes is still unclear. This study was conducted with five species of commercial interest that do not reproduce naturally in captivity: pacu Piaractus mesopotamicus, piracanjuba Brycon orbignyanus, curimbatá Prochilodus lineatus, dourado Salminus brasiliensis and piau?u Leporinus macrocephalus. Ninety-nine broodstocks were used, consisting of males and females of the five species to compare two techniques for spawning and fertilization: extrusion followed by the dry method and natural spawning. All fish were induced with two hormone doses, i.e., 0.5 and 5.0 mgCPE/kg, and were subjected to one of the two types of fertilization. The results were compared using the fertilization rate, number of oocytes produced, relative fecundity and the broodstocks' survival rate on days following spawning. All species responded positively to spawning for extrusion, and only S. brasiliensis did not spawn through the natural spawning method. The natural spawning technique provided a higher fertilization rate of eggs and a greater broodstock survival rate (P S. brasiliensis. It was concluded that the natural spawning technique can increase the production of viable eggs and reduce the mortality of species during breeding, except for S. brasiliensis.展开更多
Gezhouba Dam was built in 1981 across the Yangtze River at Yichang, Hubei Prov-ince, China. It blocked the upstream spawning migration of all anadromous species offish, including the Chinese sturgeon Acipenser sinensi...Gezhouba Dam was built in 1981 across the Yangtze River at Yichang, Hubei Prov-ince, China. It blocked the upstream spawning migration of all anadromous species offish, including the Chinese sturgeon Acipenser sinensis. Although the main historicalspawing areas of Chinese sturgeons were far upstream of the dam, successful spawning inthe reach below the dam has been documented each year since 1982 by collecting展开更多
Since the construction of the Gezhouba Dam on the Yangtze River in 1981, it has been found that the Chinese Sturgeon, Acipensor sinensis, performs natural propagation annually in a narrow reach downstream close to the...Since the construction of the Gezhouba Dam on the Yangtze River in 1981, it has been found that the Chinese Sturgeon, Acipensor sinensis, performs natural propagation annually in a narrow reach downstream close to the Gezhouba Dam site. This might allow one to better investigate the river hydrodynamic conditions of the Chinese Sturgeon spawning ground. In this article, spatial Kinetic Energy Gradient (KEG) and absolute value of vorticity were computed along the river sections from measured data. The relation between Spawn Density per Unit Area (SDUA) and vorticity strength and between SDUA and KEG were worked out. The Results showed that the vorticity and KEG were both effective parameters for describing the hydrodynamic characteristics of Chinese Sturgeon spawning ground. The Chinese Sturgeons prefer to spawn in the river sections where the value of vorticity strength is larger than 0.4 s^-1 and KEG is larger than 0.029 Jkg^-1m^-1.展开更多
In the classical form,the Poisson Multi-Bernoulli Mixture(PMBM)filter uses a PMBM density to describe target birth,surviving,and death,which does not model the appearance of spawned targets.Although such a model can h...In the classical form,the Poisson Multi-Bernoulli Mixture(PMBM)filter uses a PMBM density to describe target birth,surviving,and death,which does not model the appearance of spawned targets.Although such a model can handle target birth,surviving,and death well,its performance may degrade when target spawning arises.The reason for this is that the original PMBM filter treats the spawned targets as birth targets,ignoring the surviving targets’information.In this paper,we propose a Kullback–Leibler Divergence(KLD)minimization based derivation for the PMBM prediction step,including target spawning,in which the spawned targets are modeled using a Poisson Point Process(PPP).Furthermore,to improve the computational efficiency,three approximations are used to implement the proposed algorithm,such as the Variational MultiBernoulli(VMB)filter,the Measurement-Oriented marginal MeMBer/Poisson(MOMB/P)filter,and the Track-Oriented marginal MeMBer/Poisson(TOMB/P)filter.Finally,simulation results demonstrate the validity of the proposed filter by using the spawning model in these three approximations.展开更多
In zebrafish,the chemical identity and biological roles of reproductive pheromones have yet to be clarified.The current study assessed the role(s)of male-released odorants in a reproductive context,and evaluated the p...In zebrafish,the chemical identity and biological roles of reproductive pheromones have yet to be clarified.The current study assessed the role(s)of male-released odorants in a reproductive context,and evaluated the possible involvement of steroids and their metabolites.Females were placed in chemical and/or visual contact with males.In chemical contact,females ovulated as frequently whether they could see the males or not.Conversely,females with visual contact alone with males ovulated as frequently as isolated females.Male-released odorants attracted females;visual contact with males attracted females,but to a lesser extent;the two effects were additive.The olfactory potency of solid-phase extraction of male-and female-conditioned water was assessed by the electro-olfactogram;males released more potent odorants than females,but the most potent extract came from water in which males and females interacted freely.HPLC fractionation of these extracts revealed that,while in all samples some fractions contained odorants,male-specific activity was contained in the first four fractions,suggesting that the compounds involved are relatively hydrophilic.Finally,the olfactory potency of some steroids,previously suggested to have a pheromonal role,was assessed.However,it is unlikely that these steroids contribute significantly to the odor of fish-conditioned water.展开更多
Objective:To determine the fatty acids profiles in female fish,Rhabdosargus sarba(R.sarba)from the Red Sea during the spawning season.Methods:Monthly individual R.sarba were obtained from Bangalah market in Jeddah,Red...Objective:To determine the fatty acids profiles in female fish,Rhabdosargus sarba(R.sarba)from the Red Sea during the spawning season.Methods:Monthly individual R.sarba were obtained from Bangalah market in Jeddah,Red Sea and transported to the laboratory in ice aquarium.The total length,standard length and weight were measured,fishes were dissected.Ovaries were removed,weighed and 10 mL of concentrated hydrochloric acid were added to 10 g of the ovary in a conical flask and immersed in boiling water until the sample was dissolved and the fat was seen to collect on the surface.The conical was cooled and the fat was extracted by shaking with 30 mL of diethyl ether.The extract was bowled after allowing the layers to separate into a weighed flask.The extraction was repeated three times more and distilled off the solvent then the fat dried at 100℃,cooled and weighed.Then 50 mg of lipid was put in a tube,5 mL of methanolic sulphuric acid was added and 2 mL of benzene,the tube well closed and placed in water bath at 90℃for an hour and a half.After cooling,8 mL water and 5 mL petroleum were added and shaked strongly and the ethereal layer was separated in a dry tube,evaporated to dryness.The fatty acid methyl esters were analyzed by using a Hewlett Packard(HP 6890)chromatography,a split/splitless injector and flame ionization detector.Results:In female R.sarba,a total of 29 fatty acids were detected in ovaries throughout the spawning season.The main fatty acid group in total lipid was saturated fatty acid(SFA,28.9%),followed by 23.5%of polyunsaturated fatty acids(PUFA)and 12.9%of monounsaturated fatty acids(MUFA).The dominant SFA were palmitic and stearic,the major MUFA were palmitoleic and oleic,and the major PUFA were C18:2 and C22:2.During spawning stages,there were no significant differences in total SFA,MUFA and PUFA.The highest value of SFA was in late spawning(36.78%).However,the highest value of MUFA and PUFA was in spawning(16.70%and 24.96%respectively).During spawning season there were significant differences in total SFA between March(late spawning stage)and December(nearly ripe stage),P<0.05.Conclusions:From the present study it has been shown that 29 fatty acids were detected in ovaries of R.sarba throughout the spawning season.The main fatty acid group in total lipid was SFA followed by PUFA and MUFA.The dominant SFA were palmitic and stearic,the major MUFA were palmitoleic and oleic,and the major PUFA were C18:2 and C22:2.The highest value of SFA was in late spawning.However,the highest value of MUFA and PUFA was in spawning.展开更多
Study on coastal processes in Kapar waters was conducted from 2008-2016.The aim of this study is to identify potential blood cockle(Anadara granosa)induce spawning ground based on physical intermittency.A total of 132...Study on coastal processes in Kapar waters was conducted from 2008-2016.The aim of this study is to identify potential blood cockle(Anadara granosa)induce spawning ground based on physical intermittency.A total of 132 sampling stations were recorded.A thermal power station situated 2 km away is discharging treated warm water(<40℃)on to the open sea causing the Sea Surface Temperature at near-by cockle culture to intermittent between 31-34℃ while the temperature at the bottom(at 6-8 m Mean Sea Level,MSL)is constant between 29.5℃ and 30.5℃.The results suggested that Kapar waters have two seasons of low waters annually(January-March and June-September,respectively)and the Lowest Astronomical Tide(LAT)occur in late January-February while Great Diurnal Tide is observed on the same period.The bathymetry suggested the present of deep water(6-8 m,MSL)towards the end of cockle culture lot which is closed to merchant shipping lane near Port Klang.Based on water elevation,an area of 255.4 ha within cockle culture lots were identified to have this bottom temperature intermittency(29.5-34.0℃)during its GT and it associated with cockle induce spawning condition.But this area was left out for cockle culture due to its typical depth(>3 m MSL)which prevents cockle farmers from harvesting due to their maximum of 3 m long hand dredge.Thus,this information could be useful for cockle sustainable management plan in near future.展开更多
The Japanese common squid Todarodes pacificus is widely distributed in the Sea of Japan,the East China Sea and the Northwest Pacific Ocean,and is largely exploited by the Asia-Pacific countries.In this study,the impac...The Japanese common squid Todarodes pacificus is widely distributed in the Sea of Japan,the East China Sea and the Northwest Pacific Ocean,and is largely exploited by the Asia-Pacific countries.In this study,the impacts of regime shift of the Pacific Decadal Oscillation(PDO)during 1977-2015 on the autumn cohort of T.pacificus were assessed by examining the variations in vertical water temperatures at depths of 0 m(Temp_0 m),50 m(Temp_50 m)and 100 m(Temp_100 m)and the distribution pattern of preferred spawning ground(SSG).Spatial and temporal correlation analysis revealed that the PDO index exhibited a significantly negative relationship with vertical water temperatures at different depths and was negatively related to catch-per-unit-effort(CPUE)and stock biomass of T.pacificus.In addition,water temperatures in the specific three water layers were positively associated with CPUE.The PDO regime shift strongly affected the thermal condition and spawning ground of T.pacificus.Comparing to the negative PDO,the waters from the surface to the deep became cool in the positive PDO phase;correspondingly,the area of SSG largely contracted at different depths.Consequently,the CPUE and stock biomass of T.pacificus profoundly decreased.From the results it can be concluded that the PDO regime shift-driven changes in vertical thermal condition and SSG ranges can yield substantial impacts on T.pacificus abundance.展开更多
基金The National Natural Science Foundation of China under contract No.31602159the Agricultural Finance Special Project under contract No.CJDC-2017-22the Scientific Research Foundation of Wuxi City for Returned Oversea Chinese Scholars under contract No.CZ2019231400.
文摘The estuarine tapertail anchovy(Coilia nasus)is a high-value commercial fish.Estimating the spawning site or hatchery origin and habitat is essential for its conservation.This study aimed to determine the habitat use and life history characteristics of C.nasus from the Changjiang River Estuary.We investigated the environmental signatures of strontium(Sr)and calcium(Ca)in the otoliths of the collected specimens using electron probe microanalysis;additionally,we examined their gonadal maturity stage.Our results indicate that the 31 adult C.nasus specimens used in this study could be classified into two types based on their otolith Sr:Ca concentration ratios and their gonadal maturity stage.The long freshwater early life history type(Type LF)had wider central region in the otolith with low Sr:Ca concentration ratios ranging from 1.24±0.62 to 1.92±0.78 and a bluish pattern of low Sr content level.These fish are of riverine origin and had a relatively long early life history in freshwater and low gonadal maturation when captured.The short freshwater early life history type(Type SF)had a shorter central region in the otolith with low Sr:Ca concentration ratios ranging from 1.35±0.5 to 2.82±0.97 and a correspondingly bluish pattern.These fish also had a relatively short-term early life history in freshwater and high gonadal maturation when captured.The results of the otolith microchemical analysis indicated that Type LF and Type SF originated in spawning/hatching sites far from and close to the estuary,respectively.The mature gonads of Type SF fish indicated that they may breed in areas close to the estuary,whereas the immature gonads of Type LF fish indicated that they may breed in areas far from the estuary.This study is the first to reveal that the Changjiang River Estuary contains stocks of anadromous C.nasus originating in different spawning sites during the same season.The estuarine habitat plays a critical role in the connectivity between freshwater recruitment and the marine resources available to adult spawners of this commercially valued species.From a conservation perspective,this study provides important information for identifying anadromous C.nasus stocks originating in different spawning sites in the Changjiang River Basin.
基金Supported by the National Natural Science Foundation of China(NSFC)(No.41930534)。
文摘Japanese Spanish mackerel Scomberomorus niphonius is a pelagic,neritic species that occurs in the Yellow Sea in high commercial value.The spawning period of this fast-growing species is controlled by water temperature.Based on microstructural analysis of otoliths from 145 young-of-the-year(YoY)S.niphonius collected by trawl in 2017,2018,and 2020,and the temporal variation in the spawning period in the northern Yellow Sea,and its relationship to water temperature were examined.We found that the spawning lasted from late April to late June but differed in year:in 2017 it occurred from April 23 to June 1 and peaked in early May,in 2018 it extended later from May 7 to June 29,and in 2020 from May 6 to June 22 and peaked later from late May to mid-June.The highest temperature in 2017 corresponds with the earliest end of the spawning period and a lower growing degree-day(GDD,℃·day)of 383℃·day.In 2018,slower warming corresponds with a longer spawning period,and a GDD spawning period of 506℃·day.Rapid warming in late 2020 corresponds with a spawning peak,and a GDD spawning temperature of 448℃·day.Despite differences in spawning period,the water temperature when spawning commenced was 10-12℃.Therefore,water temperature is the major determinant of the spawning period,affecting both the starting and the ending of spawning.This study improved our understanding of the spawning dynamics and environmental adaptation of S.niphonius,and how these might change in environments subject to increased warming.
基金supported by the National Natural Science Foundation of China(62101014)the National Key Laboratory of Science and Technology on Space Microwave(6142411203307).
文摘Global Navigation Satellite System(GNSS)-based passive radar(GBPR)has been widely used in remote sensing applications.However,for moving target detection(MTD),the quadratic phase error(QPE)introduced by the non-cooperative target motion is usually difficult to be compensated,as the low power level of the GBPR echo signal renders the estimation of the Doppler rate less effective.Consequently,the moving target in GBPR image is usually defocused,which aggravates the difficulty of target detection even further.In this paper,a spawning particle filter(SPF)is proposed for defocused MTD.Firstly,the measurement model and the likelihood ratio function(LRF)of the defocused point-like target image are deduced.Then,a spawning particle set is generated for subsequent target detection,with reference to traditional particles in particle filter(PF)as their parent.After that,based on the PF estimator,the SPF algorithm and its sequential Monte Carlo(SMC)implementation are proposed with a novel amplitude estimation method to decrease the target state dimension.Finally,the effectiveness of the proposed SPF is demonstrated by numerical simulations and pre-liminary experimental results,showing that the target range and Doppler can be estimated accurately.
基金Supported by the Three Gorges Project Eco-Environmental Monitoring System(No.JJ[2015]-010)the National Natural Science Foundation of China(No.31201727)the China Three Gorges Corporation(No.0799533)
文摘Chinese sturgeon(Acipenser sinensis) is the flagship species of the Changjiang River.The migration route of this species is blocked by the first dam,the Gezhou Dam,and its reproduction is affected by the Three Gorges Dam(TGD),one of the largest dams in the world.We studied the impact of the impoundment of the Three Gorges Reservoir(TGR) since 2003 on the spawning stock and the natural reproduction of the Chinese sturgeon by using our monitoring data from 1997 to 2013.Results indicate that TGR impoundment has delayed the first spawning dates of the fish from middle-late October to late November,decreased the amount of spawning activities from twice to only once each year,and significantly reduced egg production.In particular,the fish did not demonstrate any spawning activities in 2013.Therefore,TGR impoundment significantly affects the natural reproduction of the fish downstream of the TGD.The spawning stock size of the fish is also predicted to further decrease in the future,which will lead to a risk of population extinction.Ecological regulations must be imposed on decreasing the water temperature to 20℃before mid-October and increasing water discharge downstream of the TGD in October to induce spawning of the Chinese sturgeon.
文摘Although amphioxus is widespread in temperate and tropical seas,its population is diminishing be-cause of environmental pollution.To keep the population of this evolutionarily important animal fromdiminishing,study on its reproduction and development is necessary.The main findings in this study onthe spawning and fecundity of the amphioxus reared in laboratory and its larval development are as fol-lows.1.Water temperature markedly affected the spawning.It spawned only when water temperature reached 21℃.2.Spawning of the amphioxus in laboratory was markedly extended.Initially,the amphioxus spawned at about 7:00 PM,but spawning time was postponed as spawning days went on.3.The number of eggs produced by a female ranged from 1400 to 12800,average of 5800.This al-so represents the fecundity of the amphioxus because it shedded all eggs within the ovary at a time.4.During the first few months of life of the amphioxus,its growth rate changed seasonally.Thegrowth rate in summer and fall was greater than that
文摘The distribution of nutrients and the effect of side transport of nutrients on anchovy spawning ground to the southern waters of Shandong Peninsula are discussed based on the data collected in June 2000, May and June 2001. The coastal current and upwelling are the main physical processes of nutrient transport to the southern waters of Shandong Peninsula. The concentrations of nutrients, Chl-a, the density of anchovy eggs, larva and juvenile fish increase obviously where they are greatly affected by these processes, while the contents of nutrients and Chl-a, the density of anchovy eggs, larva and juvenile fish decrease significantly where these processes diminish or disappear. The investigation suggest that the side transport of nutrients by Lubei (North Shandong) coastal current in the northern area causes the Chl-a content to be high and dense anchovy eggs, larva and juvenile fish to be dense in the coastal area of the Chengshan Cape. In the southern area, the riverine input from Subei irrigation ditch with high content of nutrients inshore and upwelling in the western edge of the Huanghai Sea Cold Water offshore should be responsible for high Chl-a concentration and dense anchovy eggs, larva and juvenile fish. It is possible that these processes of nutrient transport have controlled the anchovy spawning ground to the southern waters of Shandong Peninsula.
基金The Public Science and Technology Research Funds Projects of Ocean under contract No.201305030the National Natural Science Foundation of China under contract No.41930535。
文摘In recent years,Konosirus punctatus has accounted for a large portion in catch composition and become important economic species in the South Yellow Sea.However,the distribution of K.punctatus early life stages is still poorly understood.In this study,generalized additive models with Tweedie distribution were used to analyze the relationships between K.punctatus ichthyoplankton and environmental factors(longitude and latitude,sea surface temperature(SST),sea surface salinity(SSS)and depth),and predict distribution K.punctatus spawning ground and nursing ground,based on samplings collected in 6 months during 2014–2017.The results showed that K.punctatus’spawning ground were mainly distributed in central and north study area(from 33.0°N to 37.0°N).By comparison,the nursing ground shifted southward,which were approximately located along central and south coast of study area(from 31.7°N to 35.5°N).The optimal models identified that suitable SST,SSS and depth for eggs were 19–26℃,25–30 and 9–23 m,respectively.The suitable SSS for larvae were 29–31.The K.punctatus spawning habit might have changed in the past decades,which was a response to increasing SST and fishing pressure.That needs to be proved in further study.The study provides references of conservation and exploitation for K.punctatus.
文摘This study proposes a simulation model that well reproduces the spawning stock biomass of Pacific bluefin tuna. Environmental factors were chosen to estimate the recruitment per spawning stock biomass, and a simulation model that well reproduced the spawning stock biomass was developed. Then, effects of various fisheries regulations were evaluated using the simulation study. The results were as follows: 1) arctic oscillations, Pacific decadal oscillations and the recruitment number of the Pacific stock of Japanese sardine were chosen as the environmental factors that determined the recruitment per spawning stock biomass;2) spawning stock biomass could be well reproduced using a model that reproduced the recruitment per spawning stock biomass and the survival process of the population that included the effect of fishing;and 3) the effects of various fisheries regulation could be evaluated using the simulation model mentioned above. The effective regulation in the simulations conducted in this paper was a prohibition of fishing for 0- and 1-year-old fish in terms of recovering the spawning stock biomass. The reduction of fishing mortality coefficients for all age fish to 50% of actual values also showed a good performance. The recent reductions of the recruitment and spawning stock biomass were likely caused by heavy harvesting, especially of immature fish, since 2004.
文摘Pseudopleuronectes yokamae (Günther) is one of the most important economic fish species in the genus living specially in the northwest Pacific, and is distributed in the southern area of the far east sea of Russia, Japan, Korea, the Huanghai Sea, the Bohai Sea and the northern area of the East China Sea. Usually they live in nearshore waters of these areas as geographic subpopulations. P. yokamae in the Sheath Bay belongs to a local group of the Huanghai-Bohai Sea subpopulation and is distributed in the mouth and adjacent waters of the bay all the year round, and the catch of its spawning group has
基金Supported by National "12th Five-Year Plan" Key Technology R&D Program(2012BAD19B03)
文摘The fecundity and spawning locations of rice planthoppers in several rice varieties were surveyed in the test. The results showed that spawning behavior of rice planthoppers obeyed obvious niche distribution; rice planthopper preferred to lay eggs in the leaf sheath with spawning mark distance more than 20 cm, while they liked to lay eggs in the leaves with spawning mark distance of 10 - 20 cm. The average fecundity in leaf sheaths was obviously higher than that in leaves, indicating that leaf sheaths were more suitable for spawning of rice planthoppers than leaves.
文摘Muricids are commercially important gastropods and are exploited primarily for shell craft industries. They also occupy a niche in ornamental keeping. Studies on the larval development of muricids in Indian waters are few. Hence, an attempt was made to study with a focus on the optimum requirements for captive brood maintenance;regional variation in egg laying, intracapsular development and to estimate production potential of individual brooder (the length/ weight ranged from 80 -?110 mm/49 -?169 g (average 94.875 ± 3.980 mm/111.625 ± 14.870 g) of Chicoreus virgineus var. ponderosa collected off Tuticorin coast, Gulf of Mannar. Experimental airlift water circulation system fitted in 1 t FRP tanks having an overturn of 300% water is found suitable for long term maintenance and maturation of brooders with near cent percent survival over a year. Spontaneous breeding commenced from June ’09. Eggs cases were ‘vase’ shaped and measured 1.2 -?1.5 cm in height. Egg case numbers varied between 110 and 140 and got reduced to 10 -?40 during October and increased in Nov & December. Number of eggs within the egg case was highly variable ranging from 100 -?380. Eggs were spherical, embedded in jelly mass within the egg case and measured 510 -?608 μ (578 μ). Intra capsular development is detailed and compared with the earlier report on this species from other areas of Indian coast. Development took nearly 20 days and only few free living juveniles measuring between 1.7 -?1.9 mm emerged and the rest of the eggs have functioned as “Nurse eggs”. Average net production potential of a single viable egg case was estimated to be 6.7 nos for Chicoreus virgineus var. ponderosa of Tuticorin coast of Gulf of Mannar.
基金This study was conducted with funds granted by CNPq,FAPEMIG and CODEVASF.
文摘In order to exploit native fish species for aquaculture, basic parameters of artificial reproducetion and estimates of reproductive potential for this fish must be determined to improve hatchery success. We analyze seven Brazilian commercial fish. Spawning was induced using the hypophysation method, with injection of crude carp pituitary extract (CCPE). Characiformes species signaled the spawning time with behavioral alterations (usually circular movements). The time of oocyte extrusion varied from 5.3 ± 0.3 h in Salminus franciscanus to 8.6 ± 0.1 h in Prochilodus argenteus after the second CCPE injection. The greatest diameter of a vitellogenic oocyte was registered for P. argenteus (873.9 ± 122.2 μm) and the smallest was for Pimelodus maculates (465.4 ± 36.3 μm). The diameter of vitellogenic oocytes was very similar among species belonging to the same family. The highest ROI values were registered for Prochilodus costatus(27.0 ± 3.5 μm) and P. argenteus (23.4 ± 3.7 μm), while the lowest values were found in Pseudoplatystoma corruscans (4.6 ± 0.9 μm) and P. maculatus (6.0 ± 1.3 μm). Absolute fecundity (number of oocytes released at spawning) was lowest in P. maculatus and highest in P. corruscans. Relative fecundity (RF) presented a high correlation (r = 0.98 to 0.99) with gonad weight, indicating high efficiency of spawning. The RF also presented a high correlation with body weight (r = 0.88 to 0.97) and total length (r = 0.86 to 0.92). The highest RF was registered for Leporinus obtusidens, and the lowest was for P. corruscans. Released fecundity had a negative correlation with the diameter of vitellogenic oocytes and with the height of the follicular cells, and a positive correlation with the thickness of the zona pelucida. These results indicate that the species studied herein are suitable candidates for aquaculture due to their reproductive and zootechnical characteristics.
文摘In captive conditions, most neotropical migratory species do not have the necessary incentive to complete gonadal maturation and spawning, which require induction techniques, usually with the use of hormones. Numerous studies have therefore focused on finding an effective hormonal treatment to induce reproduction for each species. A standard treatment was successfully developed for most of these species, which consists of two doses of Carp Pituitary Extract (CPE), totaling 5.5 mgCPE/kg of fish. However, the best strategy for the subsequent fertilization of gametes is still unclear. This study was conducted with five species of commercial interest that do not reproduce naturally in captivity: pacu Piaractus mesopotamicus, piracanjuba Brycon orbignyanus, curimbatá Prochilodus lineatus, dourado Salminus brasiliensis and piau?u Leporinus macrocephalus. Ninety-nine broodstocks were used, consisting of males and females of the five species to compare two techniques for spawning and fertilization: extrusion followed by the dry method and natural spawning. All fish were induced with two hormone doses, i.e., 0.5 and 5.0 mgCPE/kg, and were subjected to one of the two types of fertilization. The results were compared using the fertilization rate, number of oocytes produced, relative fecundity and the broodstocks' survival rate on days following spawning. All species responded positively to spawning for extrusion, and only S. brasiliensis did not spawn through the natural spawning method. The natural spawning technique provided a higher fertilization rate of eggs and a greater broodstock survival rate (P S. brasiliensis. It was concluded that the natural spawning technique can increase the production of viable eggs and reduce the mortality of species during breeding, except for S. brasiliensis.
基金Project supported by the United States-China Natural Program.
文摘Gezhouba Dam was built in 1981 across the Yangtze River at Yichang, Hubei Prov-ince, China. It blocked the upstream spawning migration of all anadromous species offish, including the Chinese sturgeon Acipenser sinensis. Although the main historicalspawing areas of Chinese sturgeons were far upstream of the dam, successful spawning inthe reach below the dam has been documented each year since 1982 by collecting
基金supported by the National Natural ScienceFoundation of China (Grant No. 30490235)the NHRFoundation for Youth (Grant No. Y10704)
文摘Since the construction of the Gezhouba Dam on the Yangtze River in 1981, it has been found that the Chinese Sturgeon, Acipensor sinensis, performs natural propagation annually in a narrow reach downstream close to the Gezhouba Dam site. This might allow one to better investigate the river hydrodynamic conditions of the Chinese Sturgeon spawning ground. In this article, spatial Kinetic Energy Gradient (KEG) and absolute value of vorticity were computed along the river sections from measured data. The relation between Spawn Density per Unit Area (SDUA) and vorticity strength and between SDUA and KEG were worked out. The Results showed that the vorticity and KEG were both effective parameters for describing the hydrodynamic characteristics of Chinese Sturgeon spawning ground. The Chinese Sturgeons prefer to spawn in the river sections where the value of vorticity strength is larger than 0.4 s^-1 and KEG is larger than 0.029 Jkg^-1m^-1.
基金supported by the National Natural Science Foundation of China(No.61871301)。
文摘In the classical form,the Poisson Multi-Bernoulli Mixture(PMBM)filter uses a PMBM density to describe target birth,surviving,and death,which does not model the appearance of spawned targets.Although such a model can handle target birth,surviving,and death well,its performance may degrade when target spawning arises.The reason for this is that the original PMBM filter treats the spawned targets as birth targets,ignoring the surviving targets’information.In this paper,we propose a Kullback–Leibler Divergence(KLD)minimization based derivation for the PMBM prediction step,including target spawning,in which the spawned targets are modeled using a Poisson Point Process(PPP).Furthermore,to improve the computational efficiency,three approximations are used to implement the proposed algorithm,such as the Variational MultiBernoulli(VMB)filter,the Measurement-Oriented marginal MeMBer/Poisson(MOMB/P)filter,and the Track-Oriented marginal MeMBer/Poisson(TOMB/P)filter.Finally,simulation results demonstrate the validity of the proposed filter by using the spawning model in these three approximations.
基金Li Jie was supported by a grant from Shanghai Aquatic Products(grant no.A1-2035-150048C1)This study received national funds from Fundacao para a Ciencia e a Tecnologia(FCTPortuguese Foundation for Science and Technology)through project UID/Multi/04326/2013.
文摘In zebrafish,the chemical identity and biological roles of reproductive pheromones have yet to be clarified.The current study assessed the role(s)of male-released odorants in a reproductive context,and evaluated the possible involvement of steroids and their metabolites.Females were placed in chemical and/or visual contact with males.In chemical contact,females ovulated as frequently whether they could see the males or not.Conversely,females with visual contact alone with males ovulated as frequently as isolated females.Male-released odorants attracted females;visual contact with males attracted females,but to a lesser extent;the two effects were additive.The olfactory potency of solid-phase extraction of male-and female-conditioned water was assessed by the electro-olfactogram;males released more potent odorants than females,but the most potent extract came from water in which males and females interacted freely.HPLC fractionation of these extracts revealed that,while in all samples some fractions contained odorants,male-specific activity was contained in the first four fractions,suggesting that the compounds involved are relatively hydrophilic.Finally,the olfactory potency of some steroids,previously suggested to have a pheromonal role,was assessed.However,it is unlikely that these steroids contribute significantly to the odor of fish-conditioned water.
基金Supported by grants from the King Abdulaziz City for Science and Technology under grant no.(T-T-10-0179).
文摘Objective:To determine the fatty acids profiles in female fish,Rhabdosargus sarba(R.sarba)from the Red Sea during the spawning season.Methods:Monthly individual R.sarba were obtained from Bangalah market in Jeddah,Red Sea and transported to the laboratory in ice aquarium.The total length,standard length and weight were measured,fishes were dissected.Ovaries were removed,weighed and 10 mL of concentrated hydrochloric acid were added to 10 g of the ovary in a conical flask and immersed in boiling water until the sample was dissolved and the fat was seen to collect on the surface.The conical was cooled and the fat was extracted by shaking with 30 mL of diethyl ether.The extract was bowled after allowing the layers to separate into a weighed flask.The extraction was repeated three times more and distilled off the solvent then the fat dried at 100℃,cooled and weighed.Then 50 mg of lipid was put in a tube,5 mL of methanolic sulphuric acid was added and 2 mL of benzene,the tube well closed and placed in water bath at 90℃for an hour and a half.After cooling,8 mL water and 5 mL petroleum were added and shaked strongly and the ethereal layer was separated in a dry tube,evaporated to dryness.The fatty acid methyl esters were analyzed by using a Hewlett Packard(HP 6890)chromatography,a split/splitless injector and flame ionization detector.Results:In female R.sarba,a total of 29 fatty acids were detected in ovaries throughout the spawning season.The main fatty acid group in total lipid was saturated fatty acid(SFA,28.9%),followed by 23.5%of polyunsaturated fatty acids(PUFA)and 12.9%of monounsaturated fatty acids(MUFA).The dominant SFA were palmitic and stearic,the major MUFA were palmitoleic and oleic,and the major PUFA were C18:2 and C22:2.During spawning stages,there were no significant differences in total SFA,MUFA and PUFA.The highest value of SFA was in late spawning(36.78%).However,the highest value of MUFA and PUFA was in spawning(16.70%and 24.96%respectively).During spawning season there were significant differences in total SFA between March(late spawning stage)and December(nearly ripe stage),P<0.05.Conclusions:From the present study it has been shown that 29 fatty acids were detected in ovaries of R.sarba throughout the spawning season.The main fatty acid group in total lipid was SFA followed by PUFA and MUFA.The dominant SFA were palmitic and stearic,the major MUFA were palmitoleic and oleic,and the major PUFA were C18:2 and C22:2.The highest value of SFA was in late spawning.However,the highest value of MUFA and PUFA was in spawning.
文摘Study on coastal processes in Kapar waters was conducted from 2008-2016.The aim of this study is to identify potential blood cockle(Anadara granosa)induce spawning ground based on physical intermittency.A total of 132 sampling stations were recorded.A thermal power station situated 2 km away is discharging treated warm water(<40℃)on to the open sea causing the Sea Surface Temperature at near-by cockle culture to intermittent between 31-34℃ while the temperature at the bottom(at 6-8 m Mean Sea Level,MSL)is constant between 29.5℃ and 30.5℃.The results suggested that Kapar waters have two seasons of low waters annually(January-March and June-September,respectively)and the Lowest Astronomical Tide(LAT)occur in late January-February while Great Diurnal Tide is observed on the same period.The bathymetry suggested the present of deep water(6-8 m,MSL)towards the end of cockle culture lot which is closed to merchant shipping lane near Port Klang.Based on water elevation,an area of 255.4 ha within cockle culture lots were identified to have this bottom temperature intermittency(29.5-34.0℃)during its GT and it associated with cockle induce spawning condition.But this area was left out for cockle culture due to its typical depth(>3 m MSL)which prevents cockle farmers from harvesting due to their maximum of 3 m long hand dredge.Thus,this information could be useful for cockle sustainable management plan in near future.
基金This study was financially supported by the Shanghai Talent Development Funding for the Project(No.2021078)the National Natural Science Foundation of China(No.41906073)the Construction and Application Demonstration of Natural Resources Satellite Remote Sensing Technology System(No.202101003).
文摘The Japanese common squid Todarodes pacificus is widely distributed in the Sea of Japan,the East China Sea and the Northwest Pacific Ocean,and is largely exploited by the Asia-Pacific countries.In this study,the impacts of regime shift of the Pacific Decadal Oscillation(PDO)during 1977-2015 on the autumn cohort of T.pacificus were assessed by examining the variations in vertical water temperatures at depths of 0 m(Temp_0 m),50 m(Temp_50 m)and 100 m(Temp_100 m)and the distribution pattern of preferred spawning ground(SSG).Spatial and temporal correlation analysis revealed that the PDO index exhibited a significantly negative relationship with vertical water temperatures at different depths and was negatively related to catch-per-unit-effort(CPUE)and stock biomass of T.pacificus.In addition,water temperatures in the specific three water layers were positively associated with CPUE.The PDO regime shift strongly affected the thermal condition and spawning ground of T.pacificus.Comparing to the negative PDO,the waters from the surface to the deep became cool in the positive PDO phase;correspondingly,the area of SSG largely contracted at different depths.Consequently,the CPUE and stock biomass of T.pacificus profoundly decreased.From the results it can be concluded that the PDO regime shift-driven changes in vertical thermal condition and SSG ranges can yield substantial impacts on T.pacificus abundance.