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1.
Eight spotted ragged-tooth sharks Carcharias taurus (95–248,4 cm total length TL), ranging in known age from 0 to 16,6 years, were used to investigate the growth of the species in captivity. Total length was measured by a standard technique in some cases and estimated from photographs in others. The accuracy of the photographic technique was evaluated and found adequate for captive growth studies in sharks. Parameters of various growth models were estimated by non-linear regression and the special Von Bertalanffy growth model provided the best fit to the age-length data of the combined sexes. The parameters of the special Von Bertalanffy model are L ∞ = 249,8 cm TL, K = 0,233·year?1, t 0 = ?2,238 years. Longevity of captive C. taurus is greater than 16,6 years.  相似文献   

2.
The biology of the redspotted tonguesole Cynoglossus zanzibarensis, a common African cynoglossid inhabiting the Agulhas Bank, South Africa, is described. Growth studies based on sectioned sagittal otoliths revealed that C. zanzibarensis is relatively fast-growing and long-lived, attaining ages >8 years. Growth in length was rapid in immature fish, fish attaining 56% of their maximum size within their first year. By sexual maturity, fish had attained 28% of their maximum age and 68% of their maximum length. Total length-at-age was best described by the Von Bertalanffy growth model with combined-sex growth described as Lt = 354.78(1?e?0.43 (t+1.17)) mm TL. Sexually dimorphic growth patterns were evident, females attaining larger lengths, but at a slower growth rate than males. Despite the similar mean size of adult fish, the trawl-sampled adult population was dominated by females, with a sex ratio of 1 male:2.4 females. Female C. zanzibarensis mature in their second year of life (275 mm TL), after which they spawn small, pelagic eggs throughout the year. Approximations of the rates of total, natural and fishing mortality were estimated to be 0.62, 0.48 and 0.14 year?1 respectively.  相似文献   

3.
Mustelus lenticulatus is a non‐placental ovoviviparous shark with a gestation period of about 11 months. Young are born at a total length of 30–32 cm from September to December. Copulation, and ovulation of a further set of eggs, rapidly follows parturition. Fecundity increases with the length of the female; the most eggs found in one female was 24; the mean for all females was 10.73.

Males mature at about 85 cm total length and females at 95 cm at Kaikoura. Nelson males probably mature at a smaller size than do Kaikoura males. Nelson females mature at about 85 cm. Maximum observed lengths were 137 cm for females and 115 cm for males.  相似文献   

4.
The length at first maturity of the sand flounder, Rhombosolea plebeia (Richardson), and the yellow‐belly flounder, Rhombosolea leporina Gunther, (Teleostei: Heterosomata) in the Hauraki Gulf was investigated by the incidence of sexually tnature and immature fish grouped at 1‐cm length intervals. All male sand flounders and yellow‐bellies were sexually mature at sizes considerably less than the legal minima of 22.9 cm (9 in.) and 25.4 cm (10 in.) respectively. About 95% of female sand flounders and about 15% of female yellow‐bellies matured before reaching the respective minimum legal sizes. Most (i.e., over 50%) female sand flounders and yellow‐bellies were mature when they reached lengths of 18 cm and 26 cm respectively.  相似文献   

5.
半滑舌鳎3个形态性状与体质量的相关及通径分析   总被引：10，自引：2，他引：8  
为了深入认识半滑舌鳎形态性状与体质量之间的关系,本研究使用831尾12月龄左右半滑舌鳎个体的体质量[BM(g)]和形态性状,包括全长[TL(cm)]、体高[BH(cm)]、体厚[BW(cm)],通过模型拟合筛选获得能够反映雌、雄性个体各个形态性状与体质量关系的最佳模型。建立了以形态性状为自变量、体质量作为因变量的回归方程,并计算了直接、间接通径系数和决定系数。模型拟合结果显示,雌、雄个体全长、体高和体厚与体质量的最优拟合模型都为幂函数曲线模型,雌性个体3个形态性状与体质量的最优模型分别为:y⌒=0.004x3.090、y⌒=0.382x2.983、y⌒=61.912x2.461;雄性个体的3个最优模型公式依次为:y⌒=0.005x3.003、y⌒=0.300x3.147、y⌒=57.681x2.156。通径分析结果显示,雌性个体中体高对体质量的直接影响最大,通径系数为0.535,而雄性个体全长对体质量的直接作用最大,通径系数为0.407。雌、雄个体的3个形态性状对体质量都有极显著的直接作用,其最优多元回归方程:雌性为BM=-88.530+1.297 TL+15.862 BH+39.021 BW;雄性为BM=-71.579+2.587TL+7.351 BH+35.595 BW。  相似文献   

6.
The ornate jobfish Pristipomoides argyrogrammicus Valenciennes 1832 occurs in the Indo-West Pacific Ocean, where it is harvested by small-scale coastal fisheries. Management of this species is hindered by lack of adequate biological data. We sampled a total of 113 individuals from the landings of local artisanal fishers on the island of Réunion (southwestern Indian Ocean), from March 2014 to March 2015. The relationships between two types of body length (total and standard length, cm) and total weight (g) were shown to be significant (p < 0.05). The length–weight relationship was described by a power function, with the scaling factor estimated to be 0.008 and the exponent 3.146. Age was determined using whole otoliths. The von Bertalanffy growth equation was estimated to be TLt = 30.68(1 – e?0.52(t)). Otolith morphometry variables (length, width and area) were significantly correlated with age estimates (p < 0.05). No significant difference in age estimates was observed between left and right otoliths used as predictors. Readings from observed age and the estimates from modelled age indicated relatively good agreement, suggesting the potential to use whole otoliths for age estimation.  相似文献   

7.
Between 1978 and 1990, 209 Java sharks Carcharhinus amboinensis were caught in the shark nets that protect the swimming beaches of Natal, thereby constituting 0,5 per cent of the total shark catch. The catch rate was relatively constant at about 0,4 sharks·km net?1·year?1. Catches were highest at the northernmost beaches in summer and autumn and they consisted mostly of juvenile, but not newborn, and adolescent sharks. Specimens ranged from 99 to 176 cm PCL, with a mode of 131–135 cm for males and 131–145 cm for females. Males matured at 150 cm and females at 160 cm. Of the eight mature females caught, five were pregnant. Mating takes place in late summer and gestation is thought to last approximately 12 months. The largest embryo found was 53 cm. Teleosts were identified in 62,1 per cent of the 103 stomachs that contained food. Elasmobranchs (44,7%), crustaceans (12,6%) and cephalopods (11,6%) were the other major prey groups. Most of the fish prey were demersal, associated with soft bottoms.  相似文献   

8.
The carapace length and total length size at first maturity in females of Jasus verreauxi (H. Milne Edwards, 1851) has been investigated by a detailed study of (a) the detection of the smallest size class with external eggs, and (b) the incidence of egg‐carrying females per size‐class interval. For the study 834 females were measured and examined at Spirits Bay, New Zealand, during mid October and late December 1966. The specimens ranged in carapace length from 12.0 cm to 23.9 cm, and in total length from 29.0 cm to 56.9 cm.

The results of the study show clearly that the females reach first maturity at a carapace length or a total length larger than the present minimum legal size, i.e. a carapace length of 10.2 cm (4.02 in.), or a total length of 25.4 cm (10.0 in.). No mature females were found less than 13.5 cm carapace length, or 32.0 cm total length. First maturity was attained by the majority (50% or more) of the J verreauxi females at a carapace length of 15.3 cm or larger, or at a total length of 38.0 cm or larger.

No undersized (smaller than the minimum legal size) females were present in the collections—yet 10.3% of the specimens were found to be immature. Immature females ranged in carapace length from 12.0 cm to 16.9 cm, or in total length from 29.0 cm to 41.9 cm. Being larger than the minimum legal size, all of the immature specimens examined were “harvested"—without having reached first maturity. It appears therefore that the stocks of small, immature female J. verreauxi are not protected by the present New Zealand minimum size regulation.  相似文献   

9.
A total of 2256 specimens of Atherina boyeri caught in Gomishan wetland (a marsh lagoon located at the southeast Caspian Sea) during spawning season from February to August 2007 were examined for life-history attributes. The population has a 4-year life cycle. Length–weight relationship was estimated as W = 0.0053TL3.0181 for males and W = 0.0050TL3.063 for females, being allometrically positive for both sexes. The von Bertalanffy growth function fitted to back-calculated size at age data was: Lt = 155.17[1 − exp − 0.28(t + 0.738)] and Lt = 162.77[1 − exp − 0.27(t + 0.727)] for males and females respectively. The sex ratio was 1:1.30 in favor of females. The reproductive season, evaluated from GSI, extended from March to July, with a peak in March. The average absolute and relative fecundities were 2976 eggs and 874 eggs g−1 of body weight respectively. The diameter of oocytes ranged from 0.03 to 0.20 mm with a mean value of 0.68. The life-history patterns of A. boyeri in the population under study imply that the population of this species in the southeast Caspian Sea differs markedly from those of other localities of its range distribution. The differences were thought to be due to differences in geographical locations.  相似文献   

10.
This paper examines the relationships between maturity, length and age of whiting sampled on a length-stratified basis from groundfish surveys of the Irish Sea during spawning in spring 1992–2001. Maturity, defined by the triggering of vitellogenesis or milt production, was a function of both length and age. Proportions of mature individuals in 1-year-old males increased successively from almost zero in length classes below 15 cm to around 0.9 at 25 cm, whilst almost all 2-year-old males were mature from their smallest length of around 19 cm. Maturity in females was more strongly linked to age than to length. Most 1-year-old females were immature, the proportion of mature individuals not exceeding 0.3 in any length class. Most 2-year-old females were mature and immature fish were found in the smallest length classes only (20–25 cm). Almost all 3-year-olds of both sexes were mature in all length classes. Proportions of mature individuals in 1-year-olds increased substantially after 1997, particularly in males. Significant positive cross-correlation between proportion mature and mean length was found for 1-year-olds of both sexes. Length at 50% maturity (L50) averaged around 19 cm in males and 22 cm in females. Variability in L50 was negatively cross-correlated with average sea surface temperature in the preceding year. There is no evidence for substantial changes in maturity of whiting since the 1950s, despite an order-of-magnitude reduction in biomass caused by high fishing mortality. Concomitant decreases in mean length-at-age and weight-at-age in recent decades indicate that conditions may have been unfavourable for compensatory changes in maturation.  相似文献   

11.
Between 1978 and 1990,1 800 copper sharks Carcharhinus brachyurus were caught in the shark nets that protect the swimming beaches of Natal. The species constituted 9,6 per cent of the total shark catch. Annual catches and catch rates fluctuated widely about a mean of 138 sharks and 3,5 sharks·km net?1 respectively. Most sharks were caught at the southern beaches during the annual Natal sardine run in June and July, when shoals of pilchard Sardinops ocellatus move into the waters off southern Natal. Catches were dominated by sharks >140 cm pre-caudal length PCL. Mature males (generally ≥ 175 cm PCL) were present for much of the year, but mature females (generally ≥ 190 cm) and immature sharks were only abundant in June and July. Gonad indices in males were highest in March and April, whereas high gonad indices and large ova were recorded in females in June and July. Mating appears to take place after July and parturition about 12 months later, both occur south of the netted region. The smallest of 50 pregnant females caught was 178 cm. Mean embryo length within a litter ranged from 17 to 54 cm. Teleosts were found in 92 per cent and pilchard in 84 per cent of stomachs containing food.  相似文献   

12.
A total of 1125 specimens of sardine, Sardina pilchardus, ranging in total length from 4.9 to 12.5 cm (mean 8.31 ± 1.41 cm) and in weights between 1.02 g and 11.18 g (mean 4.40 ± 1.87 g) were randomly sampled using a beach seine from the Krka River estuary. Samples were collected monthly according to their occurrence in this area from October to February during 2002/03, 2003/04 and 2004/05, which is during the spawning period of this species. Monthly fluctuations in the length frequency distributions of sardine were observed during that time. The length–weight relationship of all sardine specimens was described by the equation: W=0.007L2.9587(r2 = 0.9626); and the isometric nature of relative growth was established (t = −5.1495; p < 0.05). According to the allometric condition factor Ka, sardine specimens were in better somatic condition at the beginning of their appearance (spawning period) in the Krka River estuary. The length at which 50% of sardines were mature (L50) was calculated to be 7.9 cm.  相似文献   

13.
骨形态发生蛋白2（BMP2）在脊椎动物的骨形成、尤其是诱导成骨方面具有至关重要的作用。本研究克隆了半滑舌鳎（Cynoglossussemilaevis）BMP2基因的cDNA序列，分析其在半滑舌鳎成鱼的组织表达差异及其在早期发育阶段的定位和表达变化趋势，并检测了其启动子活性。研究结果表明，半滑舌鳎BMP2基因cDNA全长为2048bp，编码422个氨基酸。BMP2mRNA在半滑舌鳎成鱼的14个组织中具有广泛的分布，并在脊髓中表达量最高。此外，BMP2基因在早期胚胎发育阶段（原肠期）具有极高水平的表达，其表达量约为其他发育阶段表达量的10倍。整体原位杂交检测结果表明，BMP2mRNA在1日龄仔鱼主要在冠状幼鳍、心和肝表达，在脊索有微量表达；随后，3日龄仔鱼的BMP2mRNA主要表达于脊索。通过对BMP2基因5''上游调控区片段进行启动子活性分析，发现了-179～+109片段可能包含启动子活性增强原件，生物信息学预测该片段包含的锌指转录因子等可能参与了BMP2的转录调控。  相似文献   

14.
A method of aging the elephant fish Callorhinchus milii Bory de St Vincent 1823, is described. Alternating light and dark layers, seen in cross‐sections of the dorsal spine, are assumed to be laid down annually as in other fish. Ages obtained from spine sections are identical with ages obtained from interpretation of modal peaks in the length‐frequency graphs. Males mature at 3 y old, at approximately 50 cm fork length; females at 4.5 y old and 70 cm. The significance of this in relation to the New Zealand fishery for elephant fish is discussed.  相似文献   

15.
The current study provides long-term catch rate and biological data for tiger sharks Galeocerdo cuvier caught in the KwaZulu-Natal bather protection programme. Between 1978 and 2014, 1 760 G. cuvier were caught in nets and between 2007 and 2014, 108 G. cuvier were caught on drumlines. Standardised catch rates increased significantly over time (p < 0.001) for both small (≤180 cm precaudal length, PCL) and large sharks (>180 cm). There was also a significant temporal increase in the mean size of sharks across gear types (p < 0.001). A quasi-Poisson generalised additive mixed model showed that the deployment of drumlines had no significant effect on the catch rate of sharks in nets. The nets, however, caught significantly larger sharks (mean 184.5 cm, SD 39) than did drumlines (mean 138.6 cm, SD 36.5; p < 0.001). The size frequency of the catch was unimodal and females significantly outnumbered males in both gear types. Few young-of-the-year (0.8%) or mature sharks (1.8%) were caught. Only 23 (4.7%) of the 486 sharks tagged and released were recaptured, with the majority (87.0%) of those recaptured <150 km from their original tagging locality. The results from this study suggest an increasing local population trend in G. cuvier along the KwaZulu-Natal coast.  相似文献   

16.
Here we report the first observations of loggerhead turtles Caretta caretta preying on a conspicuous molluscan invader, the rapa whelk Rapana venosa. An average number of 136 opercula were found in stomach contents of five turtles, the curved carapace length ranging in from 51 to 112 cm. No other alimentary items were found in the turtles analyzed. We suggest that the rapa whelk may constitute up to 100% of the diet for immature and mature loggerheads in the Río de la Plata estuary (Uruguay), highlighting the plastic nature of the foraging behavior of loggerheads.  相似文献   

17.
Reproductive aspects of the golden ling, Genypterus blacodes, from the southern Chilean fishery are presented. Gonad samples were obtained from commercially caught fish between September 1999 and October 2000. Stage of sexual maturity, gonadosomatic index (GSI), and size of females at 50% maturation determined by logistic methods and by plotting the mean GSI by total length, are presented for both years. Batch fecundity was calculated from subsampling mature ovaries containing oocytes in advanced stages of maturity. Changes in GSI and monthly diameters of oocytes showed that ling had a spawning season which extended between August and November. The sizes at first maturity in 1999 and 2000 were 86.6 and 84.8 cm total length (TL), respectively, using the logistic model, and 84 cm for both years using the mean GSI‐size plotting method. The mean batch fecundity was 333 330 oocytes per individual for fish sized 85–120 cm TL. Fecundity increased with increasing weight and total length.  相似文献   

18.
红鳍东方鲀(Takifugu rubripes)形态性状对体重的影响效果   总被引：1，自引：1，他引：0  
采用通径分析方法,对红鳍东方鲀表型形态性状对体重的影响效果进行研究.结果表明,所测各表型性状与体重之间的相关系数均达到显著水平(P＜0.05)或极显著水平(P＜0.01);体周长1对体重的直接影响(0.533)最大,对体重的决定程度(28.41％)最高,是影响体重的主要因素;全长对体重的直接作用(0.369)较大,间接作用(0.259)最小;体高、尾柄高对体重的直接作用(0.228,0.145)相对较小,主要通过体周长1的间接作用(0.363,0.296)影响体重.所选表型性状对体重的复相关指数R2=0.950,表明所选性状是影响体重的主要性状.利用逐步回归分析方法建立以体周长1、体高、尾柄高为自变量估计体重的多元回归回归方程为:y =-2154.095+42.072x1+33.936x2+72.687x3+50.538x4.  相似文献   

19.
本文通过qPCR方法,研究了我国重要海水鱼类——牙鲆（Paralichthys olivaceus）雌、雄成体组织以及性腺分化期的脑、性腺中gnrh1、gnrh2和gnrh3的表达水平。结果显示,gnrh1分布于所有检测的组织：在脑、垂体、肾脏和肝脏中高表达,在性腺中表达相对较低;gnrh2则在雌、雄性的肝脏以及雄性的肠、肾脏、眼睛和头肾中;而gnrh3只在雄性的肾脏、眼睛和肌肉中检测到微弱表达。人工诱导的牙鲆雌核发育鱼苗分别用17β-雌二醇（E2）和17α-甲基睾酮（MT）处理,使其分化为雌性或雄性个体表型。在性腺分化期的脑中,gnrh1的表达呈现上升趋势,在全长（total length,TL）4 cm鱼苗中,E2组的表达显著高于MT组（P<0.05）;gnrh2在2 cm TL时E2组显著高于MT组（P<0.05）,随后在E2和对照组的表达水平均出现下降趋势;gnrh3在2 cm TL时E2和对照组的表达均显著高于MT组（P<0.05）,自6 cm TL时MT和E2组的表达开始下降。在性腺中,三种gnrh在性腺分化前2 cm TL表达量都相对较高,随后呈现下降趋势。综上,推测牙鲆gnrh1可能参与了性腺分化的启动、分化过程及性腺发育,gnrh2主要参与了性腺分化的启动,gnrh3主要参与了性腺分化的启动和分化过程。  相似文献   

20.
The reproductive cycle of anchovy, Engraulis encrasicolus (L.), was studied from monthly random samples of purse seine catches. A total of 1477 anchovy specimens were collected from January to December 2003 in the Zrmanja River estuary (Novigrad Sea). The analysis was based on the temporal evolution of gonadosomatic index, mass and stage of gonads. The total length of anchovy ranged from 4.5 to 14.5 cm and mass from 0.56 to 19.80 g. Sex ratio was slightly different from 1:1; the females were insignificantly predominated (♂/♀ = 0.99). The period of reproductive activity was from April to September coinciding with the most developed stages of gonads as well as with the highest gonad weights, and gonadosomatic indices. To estimate the length at maturity, a sub sample of 454 anchovy was taken from May to July (peak of anchovy spawning period). The length at which 50% of anchovy were mature (L50) was calculated to be 8.2 cm. The length–weight relationship of anchovy was described by the expression: W = 3.51 × 10−3 LT3.211 (r2 = 0.998). The relationships between total length–standard length and total length–fork length are LT = 1.1405LS + 0.2420 and LT = 1.0425 LF + 0.3944, respectively.  相似文献   

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