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1.
ABSTRACT:   The purpose of this study was to determine the growth and reproductive characteristics of round scad Decapterus maruadsi in the East China Sea. The characteristics regarding growth and reproduction of round scad based on otolith reading and gonad histology, respectively, were estimated. The von Bertalanffy's growth model for round scad was estimated as follows:
FL t  = 342[1 − exp{−0.55( t  + 0.58)}], (1 <  t  < 7)
where FL t is fork length (mm) at age in years t . The maturation stage of the ovary was observed by histological techniques. June was the main spawning period; the maturation and migratory nucleus stage of the oocyte was observed when the gonad somatic index value was approximately greater than 4.  相似文献   

2.
ABSTRACT: The reproductive value and population status of the big eye in the north-eastern Taiwan waters was estimated by demographic analysis using available life-history parameters. Life-history tables were constructed using estimates of natural mortality ( M ) of 10.4920/year for age 0 and 0.3256/year for ages 1–9, with a maximum age of 9. Age-specific batch fecundity ( Fe ) was from Fe  = 1391.34e0.1782 FL . The age-specific proportion of maturity was estimated from the relationship between the proportion of female maturity ( Pr ) and fork length ( FL ): Pr  = 1/(1 + e15.081−0.796 FL ). Females mature at age 3 and mature females reproduce every year. The population increase rate (λ) was estimated to be 20.5% per year and the generation time ( G ) was 6.25 years without exploitation. The net reproductive value ( R0 ), generation time and intrinsic rate of natural increase ( r ) decreased with increased fishing mortality. For fixed fishing mortality, when F  = 1.2/year and fishing started at age 3, R0 was estimated to be 1.0 and the population was considered to be in equilibrium. For age-specific fishing mortality, when fishing started at age 3, R0 was estimated to be 0.96/year, G being 6.18 years, and the population decreased 0.7% per year. The big eye population had a strong resilience as long as F  < = 1.3/year started at an age that was older than the age at maturity (i.e. 3 years old) but would decline when intensive fishing ( F  > = 1.2/year) started at age 2 or younger. Sensitivity analysis indicated that the mortality of age 0 is the most sensitive parameter in demographic analysis.  相似文献   

3.
ABSTRACT:   The age, growth and maturation of the redbelly tilapia Tilapia zillii introduced into the Haebaru Reservoir on Okinawa-jima Island were studied using 2197 specimens ranging from 7.3 to 168.0 mm standard length (SL). The spawning season was estimated to be from April to August, with a peak in April and May. The first maturation sizes of females and males were estimated to be 38.1 and 33.0 mm SL, respectively. The opaque zones in otoliths that form annually were found to correlate with the spawning season. Maximum ages of females and males were 7 and 6 years, respectively. The von Bertalanffy growth formulae were expressed as: L t  = 99{1 − exp[−0.67( t  + 0.09)]} for females and L t  = 155{1 − exp [−0.36( t  + 0.12)]} for males. Males grew to be larger than females from the first year onward. Populations of this species are characterized by early maturation life history parameters and are thought to adapt and become established quickly after being released into new water systems. Furthermore, extermination activity in winter is thought to be an effective strategy before the newly recruited fish begin breeding in the warmer months.  相似文献   

4.
ABSTRACT:   Common silver biddy Gerres oyena were collected monthly between November 2002 and November 2005 in Okinawa Island of southern Japan. The seasonal reproductive cycle of this species was investigated using the gonadosomatic index (GSI) and through histological observation of gonads. Temporal variation in the GSI reflected gonadal development from histological observations; ovary development occurred from March to September and testes development occurred between March and August. Maximal development was observed in April and May in both sexes. While mean values for hepatosomatic and lipidosomatic indices decreased markedly in females relative to males during gonadal development, mean condition factors decreased with gonadal recrudescence in both sexes. The minimum standard length (SL) at sexual maturity was 89.7 mm for females and 81.4 mm for males and the size at which 50% of individuals were sexually mature was 104 and 92 mm SL in females and males, respectively. The power relationships of batch fecundity (BF) versus standard length (SL, mm) and body weight (BW, g) of females can be expressed as BF  = 46.7 × e1.64 SL and BF  = 19 697 × e0.49 BW , respectively.  相似文献   

5.
ABSTRACT:   Age and growth of alfonsino Beryx splendens (Lowe) were studied using counts of presumed daily incremental growth rings on the transverse section of otoliths of fish collected from the Kanto District, central Japan. Microstructural growth increments were observed from the core to the outermost margin of the broadest of approximately 50 branches formed on the surface of an otolith. Of 98 otoliths examined, 46 were readable. The number of increments and fish lengths ranged from 448 (218 mm fork length [FL]) to 3701 (411 mm FL). The ages of these fish were estimated to be 1 year, 2 months and 10 years, 2 months, respectively, assuming that an increment was formed daily. The von Bertalanffy growth equation combined for males and females was expressed as follows: L t  = 542 {1 −  exp  [−0.133( t  + 2.00)]}, where L t is fork length (mm) at yearly age t . The results of the present study were compared with those of other researchers who had studied alfonsino from central Japan.  相似文献   

6.
ABSTRACT:   Elongate ilisha Ilisha elongata is a commercially important fishery resource in both Japan and China. Age and growth of the species were investigated by scale analysis from June 1996 to July 1997 in Ariake Sound, Japan. Scale annuli were formed once a year mainly between June and July. The age was 1–6 years for both male and female individuals. There was no significant difference in the regression of fork length (FL) on scale radius ( R ) between sexes by a covariance analysis. The combined sex von Bertalanffy growth equations were expressed as L t  = 495.4 × (1 − e−0.3176( t  + 0.4108)), where L t is FL in mm at age t . Comparison of the age and growth among different populations from coastal waters in the western North Pacific Ocean suggested that the FL of the Ariake population is the smallest at each age. The spatio–temporal variations in growth are possibly relevant to environmental conditions of the growth grounds of subadults; however, there was no gradient change in the growth of I. elongata with latitude. Water temperature may not be the main factor affecting the growth of this species . The growth of the tropical population from Sarawak differs greatly from those of temperate and subtemperate populations, which implies genetic variation or phenotypic plasticity in different climate zones.  相似文献   

7.
ABSTRACT:   The effect of various tooth spacing on the contact selection and the net-mouth available selection of a dredge for the equilateral Venus clam Gomphina melanaegis is evaluated by applying a contact-probability model based on the SELECT method to the data of paired-gear tests with a control dredge of 12-mm tooth spacing and four test dredges of tooth spacing 16, 20, 24 and 35 mm. A master selection curve was estimated to be s ( R ) = exp(−11.23 R  + 4.799)/(1 + exp[−11.23 R  + 4.799]) where, R is l / d , the ratio of the shell length, l , to the tooth spacing, d . The shell width of 50% retention was slightly smaller than the tooth spacing, which means that size selectivity of teeth was a type of contact selection which was dependent on the tooth spacing. Contact probability, δ, of the clams coming into contact with the teeth were 0.625, 0.467, 0.563, 0.670 and 0.976 for tooth spacing 12, 16, 20, 24 and 35 mm, respectively. This indicates that some clams entered the dredge bagnet without contacting the teeth as the sand clogging the tooth spacing carried them into the bagnet. Available selection curve of the dredge net-mouth with teeth was obtained as δ s ( R ) + 1 −  δ , and examined in terms of the legal landing size of the Venus clam.  相似文献   

8.
Donhyug  KANG  Kazuhiro  SADAYASU  Tohru  MUKAI  Kohji  IIDA  Doojin  HWANG  Kouichi  SAWADA  Kazushi  MIYASHITA 《Fisheries Science》2004,70(5):819-828
ABSTRACT:   Black porgy are hatched and released in marine ranching areas in Japan, Korea and Taiwan to maintain fisheries resources in coastal areas. If acoustic methods are used for field surveys, target strength ( TS ) information on the species is needed to convert acoustic data to biomass density. Target strength of black porgy ( Acanthopagrus schlegeli ) 15.5–32.9 cm fork length (nine individuals) was measured at 38 and 120 kHz (split beam) by ex situ measurements (cage and fishhook methods) of living fish, a tethered method with shock-frozen fish, and an acoustic scattering model, the Kirchhoff ray mode (KRM) model based on fish morphology. The ex situ TS -to-fork length ( FL , cm) relationships were TS 38kHz = 20log10 FL  − 64.6 ( r  = 0.77) and TS 120kHz = 20log10 FL  − 65.2 ( r  = 0.70). The values for the KRM model were TS 38kHz = 20log10 FL  − 64.8 ( r  = 0.88) and TS 120kHz = 20log10 FL  − 65.4 ( r  = 0.80). The agreement between the ex situ measurements and the KRM model for the mean TS was very good. In contrast, the results for the tethered method ( TS 38kHz = 20log10 FL  − 69.3 [ r  = 0.42]) differed markedly from the other two methods, perhaps because of the effects of the shock-freezing procedure in air. The results of the ex situ measurements and scattering model provide basic information for studying TS and conducting acoustic surveys of black porgy, even though the tethered method must be modified.  相似文献   

9.
ABSTRACT:   Studies were conducted on growth and reproduction of the red frog crab, Ranina ranina (Linnaeus, 1758), in the Andaman Sea off Thailand from 1998 to 1999. Samples were collected from Ko Similan, Ko Surin and Thai-Myanmar boundary waters by gill net. Results showed that the relationship between carapace length (CL) and body weight (BW) for males (CL, 5.84–14.10 cm) was BW = 0.2598 CL3.0931, and for females (CL, 5.35–10.97 cm) was BW = 0.4280 CL2.8656. Growth in each gender showed allometric growth. The average CL of males was significantly larger than that of females. Average male and female crab sizes in 1999 were smaller than in 1998. The spawning season was found to be from November to February; maturing male crabs were abundant from September to December. Average sizes of CL at first maturity for males and females were 7.44 and 7.22 cm, respectively. Fecundity ranges of ovigerous female crabs were 74 600–167 900 eggs with an average egg diameter of 0.62 mm. The monthly sex ratios (male : female) varied between 1:0.56 and 1:2.77.  相似文献   

10.
ABSTRACT:   In Tokyo Bay, conger tube-trap fishers voluntarily deployed escape holes of at least 13 mm diameter to reduce the by-catch of young conger smaller than the marketable size of 35 cm total length. Comparative fishing experiments in Tokyo Bay were carried out using tube traps with seven hole diameters (3, 9, 13.5, 14, 15, 17, and 19 mm), to obtain the size-selectivity of the escape-hole size for inshore hagfish Eptatretus burgeri and white-spotted conger Conger myriaster . On the assumption of the geometrical similarity in the combination of body g and hole perimeter m at a given retention probability, a single master curve s ( R ) = exp(−13.52 + 11.31 R )/(1 + exp [−13.52 + 11.31 R ]) was estimated for the two species in terms of relative R  =  g / m using the Share Each LEngth's Catch Total (SELECT) process based on a multinomial distribution. Almost all conger and hagfish with a girth equivalent to the hole perimeter were able to pass through the hole. Thus, the two species have a high ability to escape through a narrow space by squeezing the body through the hole in the rigid PVC tube. Optimum escape-hole size is discussed from several objectives for conger tube-trap fishery management, e.g. reduction of hagfish by-catch. This study also specifies the conditions for pooling data when fishing experiments using more than two fishing gears are replicated.  相似文献   

11.
ABSTRACT:   Mid-water trawl surveys were conducted from late August to late September in 1999 and 2004 in order to investigate the distribution pattern, hatch date, and growth of juvenile Pacific bluefin tuna Thunnus orientalis in the Sea of Japan. Juveniles were collected at the stations where ambient water temperature (mean water temperature from surface to 30 m deep, WT0−30) was 23.4–25.9°C, and most of them were found in waters where WT0−30 was higher than 24°C. Sampled juveniles ranged 108–280 mm fork length. Based on otolith analysis, they were estimated to grow to approximately 180 and 250 mm at 60 and 90 days old, respectively, and showed similar growth to that of Atlantic bluefin tuna in the Mediterranean Sea. The back-calculated hatch date of the samples was mostly in July and most juveniles spawned in the Sea of Japan.  相似文献   

12.
ABSTRACT:   Final oocyte maturation and ovulation of captive chub mackerel Scomber japonicus with fully yolk-accumulated oocytes were induced by a single injection of human chorionic gonadotropin. Reproductive parameters, including spawning frequency and batch fecundity, which are required to estimate spawning biomass in pelagic fish by the daily egg production method, were analyzed. Germinal vesicle migration (GVM) occurred at 18–24 h post-injection, and the hydration and ovulation of oocytes were completed at 30 and 36 h post-injection, respectively. The results of the maturation process suggest that fish with GVM-stage ovaries captured in the daytime from the field are capable of spawning on the night following their capture. The oocytes used in the oocyte size-frequency distribution method for batch fecundity estimates should be at late GVM and more advanced stages. The results of sequential artificial insemination showed that the quality of ovulated eggs held in the ovarian lumen rapidly deteriorated as time progressed after ovulation. This indicates that the fertilization window for the ovulated eggs of chub mackerel lasts only a few hours, and spawning behavior should be performed within a few hours after ovulation in the wild population.  相似文献   

13.
The reproductive biology of 315 cobia, Rachycentron canadum, from northeastern Australia was studied for an 18-month period. Cobia ranged from 181 to 1,470 mm FL (0.06–55 kg). Length–frequency distributions of males and females did not differ significantly. The sex ratio of females to males was 2.18:1. Histological data showed that cobia developed hydrated oocytes during a protracted spawning season between September and June. Gonadosomatic index peaked from October to December, coinciding with the monsoon or “wet” season. Estimated length at first maturity for female cobia was 671 mm FL. Length at 50% maturity (L 50) for females was estimated at 784 mm FL (1–2 years of age). Batch fecundity ranged from 577,468 to 7,372,283 eggs with a mean of 2,877,669 (± SD 1,603,760) eggs. Relative batch fecundity was 249 eggs per g, and no relationship between relative fecundity and fork length was found. There was a significant positive relationship between the total number of eggs produced and fork length. Spawning frequency, estimated by the post-ovulatory follicle method, was 7.6 days. Based on the detection of hydrated oocytes in fish caught at night, cobia most likely spawn at night. Cobia also feed throughout the spawning period. This is the first report on the reproductive biology of cobia in Australian waters, and provides valuable data for future population assessments of cobia throughout the Indo-Pacific.  相似文献   

14.
ABSTRACT:   To understand the mechanism of the behavioral response in the capture process of how fish recognize fishing gear and then how they can avoid the gear, the visual acuity of Pacific saury Cololabis saira was investigated by histological examination of the retina of individuals in the size range of 75–365 mm fork length (FL). The contour map of cone density distribution shows that the highest cone density is located in the temporal area of the retina, which indicated the visual axis as the forward direction. The visual acuity (VA) depends both on the focal length of the lens and the number of cones in the retina. The lens diameter increased linearly from 1.40 to 4.73 mm with fish growth, while the cone density decreased gradually from 765 to 378 cells/0.01 mm2. Our results show that the visual acuity increases proportionately from 0.057 to 0.140 for individuals ranging in FL from 75 to 365 mm as expressed by the equation VA  = 0.0065 ×  FL 0.5271 ( r 2 = 0.9624).  相似文献   

15.
ABSTRACT:   The catch of ribbonfish Trichiurus lepturus in the coastal waters of south-western Taiwan has significantly declined in recent years. To examine the effects of exploitation on the feeding habits of ribbonfish, 1570 specimens were collected on a monthly basis during March 2002–March 2003 from the landings by trawlers operating in the coastal waters of south-western Taiwan. The size of the ribbonfish ranged from 83–298 mm preanal length (PL), with a peak at 201–250 mm PL. Although they fed on shrimps and squid, fishes including Benthosema pterotum , Bregmaceros lanceolatus and Encrasicholina heteroloba were their main food items . In particular, B. pterotum was the most important food all year except during summer. No evidence of cannibalism was found in this study. No differences between day and night were found in the feeding activity of T. lepturus . However, B. pterotum and Acetes intermedius were the most important prey in the daytime, whereas B. lanceolatus , B. pterotum and E. heteroloba were at night. Feeding activity and the number of food items increased with increasing size of ribbonfish. Their feeding intensity in February to June, the main spawning season, was significantly greater than in other months. Changes in the food and feeding habits of this species before and after the recent period of heavy exploitation are discussed in detail in this study.  相似文献   

16.
Abstract:   Age, growth and sexual maturity of the fan ray Platyrhina sinensis in Ariake Bay, Japan were determined from specimens collected from May 2002 to September 2006. Age determination was conducted by vertebral centrum analysis using soft X-radiography. Annual band pair deposition was determined by marginal increment and edge analyses. The von Bertalanffy growth model best described the overall pattern of growth for both males and females (males L ∝  = 455.2, k  = 0.56, t 0 = −1.09; females L ∝  = 555.8, k  = 0.28, t 0 = −1.77; L ∝ is the theoretical asymptotic total length in mm, k is the growth rate coefficient and t 0 is the theoretical time at zero length). Parameter estimates suggest that females attain a larger asymptotic total length and grow more slowly than males. The observed maximum ages were 5 years for males and 12 years for females. Age at 50% sexual maturity was 2.1 years for males and 2.9 years for females. The results indicate that this species is relatively fast-growing, short-lived and early maturing compared with many batoid species.  相似文献   

17.
ABSTRACT:   The size selectivity of a trammel net for herded oval squid Sepioteuthis lessoniana in Tateyama Bay, Chiba Prefecture, was estimated by comparison between the mantle length frequency distributions of oval squid caught by a trammel net and by a set net. The measured mesh sizes of the inner net of the trammel net and of the final section of the set net were 85.3 and 11.3 mm, respectively. In the trammel net fishery where oval squid are herded into the net, most of the oval squid are caught in the bag-shaped inner net. Hence, the logistic function was employed for the size selectivity curve of the trammel net. The 'share each length's catch total' (SELECT) model was implemented for the estimation of the selectivity curve. The size selectivity r ( l ) of the trammel net for the oval squid was expressed as a logistic function of the mantle length l : r ( l ) = exp(−18.57 + 0.88  l )/[1 + exp(−18.57 + 0.88  l )]. From these logistic parameter estimates, the 50% selection mantle length and selection range ( L 75– L 25) were calculated as 21.07 and 2.49 cm, respectively. The selection probability of oval squid whose mantle girth was equivalent to the mesh perimeter of the inner net was 0.09. Accordingly, oval squid of a girth smaller than the mesh perimeter were likely to pass through the mesh to escape from the net.  相似文献   

18.
Gillnet selectivity parameters for the Atlantic sharpnose, Rhizoprionodon terraenovae, blacknose, Carcharhinus acronotus, finetooth, Carcharhinus isodon, and bonnethead, Sphyrna tiburo, sharks were estimated from fishery-independent catches in multi-panel gillnets with stretched mesh sizes ranging from 8.9 to 14.0 cm in steps of 1.3 cm, with an additional size of 20.3 cm. Mesh selectivities were estimated using a maximum-likelihood model, which fits a gamma distribution to length data for each mesh size using the log-likelihood function. The Atlantic sharpnose and finetooth shark exhibited the broadest selection curves. Peak selectivities for the Atlantic sharpnose were reached from 750 mm FL for the 8.9 cm mesh to 1150 mm FL for the 14.0 cm mesh in 50 mm FL increments per mesh. Peak selectivity for the finetooth shark was reached at 550 mm FL for the 8.9 and 10.2 cm meshes, increased to 650 mm FL for the 11.4 mesh, and 750 mm FL for the 12.7 and 14.0 cm meshes. Selectivity was highest at 1150 mm FL for the 20.3 cm mesh. The bonnethead and blacknose shark exhibited narrower selection curves, with peak selectivity occurring at 450 mm FL for the 8.9 cm mesh, 750 mm for the 12.7 cm mesh in 100 mm FL increments per mesh. Maximum selectivity for the 20.3 cm mesh was 950 and 1050 mm FL for bonnethead and blacknose shark, respectively. The θ1 values for blacknose and finetooth shark were most similar (140.58 and 141.25), whereas the value calculated for Atlantic sharpnose was the highest (211.95) and that for the bonnethead (131.77) was the lowest. Values calculated for θ2, a parameter that describes the variance of sizes by mesh, ranged from 27,259 for the bonnethead to 189,873 for the finetooth shark. Although gillnets used in this study were not directly constructed for use in estimation of gillnet selectivities, information on mesh selectivities estimated herein has direct applicability to commercial gillnets with meshes of similar sizes.  相似文献   

19.
ABSTRACT:   The blackspot snapper Lutjanus fulviflammus is one of the most common Lutjanus species landed and consumed on Okinawa Island, Japan. Using 901 fish (29.9–304.2 mm in standard length; SL) obtained from fish markets or caught by angling, the age, growth, maturation size and maturation age were estimated. Each opaque zone formed on the otolith every year correlated with their spawning and was thought to be an annual ring. The main spawning season was estimated to be from April to July, which peaked in May and June, with a few mature fish collected in August and September. Maximum ages were observed as 24 years for both sexes and L∞ (mm SL), K and t0 (years) of the von Bertalanffy growth formula were estimated to be 276, 0.144 and −5.22 for females and 247, 0.227 and −3.18 for males, respectively. First maturation size and age were estimated to be 175 mm SL and 2 years for both sexes. A faster growth rate up to 2 years will allow reproduction at a young age and provide many chances for spawning throughout their long life. Furthermore, the possibility exists that populations would easily recover if regulations were established.  相似文献   

20.
ABSTRACT:   In total, 491 whitespotted bamboo sharks were collected from northern Taiwanese waters from February 2002 to February 2003. The sex ratio of the specimens was 0.65, total length (TL) ranged from 35.3–85 cm, and weight ranged 124–2580 g. The mean size at first maturity was estimated to be 64.9 and 65.6 cm TL for females and males, respectively, based on the relationship between mature percentage and TL. The ovulation season was estimated as March to May based on gonadosomatic index (GSI) variations and captive observation. The monthly changes in GSI of males suggested that the mating season was from December to January. The inconsistency between mating and ovulation seasons suggested that females have sperm storage and delayed fertilization. One or two eggs were deposited every 6 or 7 days on average. Deposition of eggs extended for 2 months, and fecundity was 8 ± 3.8 eggs. Thirteen of 48 eggs deposited in 2003 were hatched and the hatching rate was 0.27. The hatching period was 107 ± 9.3 days with accumulated water temperature ranging from 2372–2835°C.  相似文献   

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