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1.
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2.
Intermittent rivers make up a large portion of the global river network and are the dominant river type in northern Australia. Increased pressure is being placed on such systems, and a better understanding of their ecology is needed. We examined, over a 7‐year period, the fish fauna of the intermittent Fergusson River, a major tributary of the Daly River of the northern Australia. Changes in habitat structure with the onset of the dry season involved contraction of the riffle/run/pool habitat to a single refugial pool, the size of which was determined by antecedent wet season hydrology. The fishes present comprised a subset of species present within the Daly River main channel and consisted of the most widely distributed of northern Australia's freshwater fishes. The Fergusson River provides suitable spawning habitat for species during the wet season (e.g. Hephaestus fuliginosus, Leiopotherapon unicolor and Neosilurus catfishes) and during the dry season for a different set of species (e.g. Amniataba percoides, Melanotaenia australis and Glossogobius aureus). Little year‐to‐year variation in assemblage structure was observed early in the dry season, whereas interannual variation in late dry season assemblages was substantial. Dry season recruitment imparted some of the interannual variability in assemblage structure recorded between late dry season samples. Piscivorous fishes were an important, but temporally variable, component of the assemblage present in the late dry season refugial habitat, and predation was potentially another important source of variation in assemblage structure.  相似文献   

3.
Abstract. The reproductive biology of a popular and abundant freshwater catfish, Mystus nemurus Cuvier & Valenciennes, was examined, including sex ratio, gonadosomatic index, ova diameter and fecundity. The numerical ratio of male to female was 1:1.06 and was not significantly different (P > 0.05). Mean female gonadosomatic indices (GSI) in April and September corresponding to north-east and south-west monsoons were significantly different (P < 0.05) from the dry season (May, June, July and August). Thus the apparent GSI maxima in April and September were indicative of peak spawning period. However, there were no significant differences (P > 0.05) in the fluctuation of the measure of GSI except for those in the dry months, which probably suggested the existence of a protracted breeding season. Mean male GSI in February and November were similarly significant (P < 0.05) to the dry season, although not statistically different (P > 0.05) from those of January, March, April, July, August, October and November. This was probably attributable to an extended breeding period with spawning peaks in February and November corresponding to early and late monsoons. The aseasonal reproduction is common in tropical fishes. GSI were positively correlated with rainfall and water level fluctuations. Fecundity varied from a minimum 6900 to a maximum 93510 in specimens with total lengths of 34.8cm and 45.0cm respectively. Fecundity was found to increase linearly with length and weight and was significantly different (P < 0.05) from them.  相似文献   

4.
Abstract. In contrast to its North American relatives, the Lake Naivasha blackbass, Micropterus saimoides (Lacepdde) has a prolonged spawning season of 8 months between June and January, peaking in August to November. This season is characterized by the presence of high numbers of mature fish with the highest gonadosomatic index (GSI). Analysis of GSI variations in different length-classes reveals that maximum reproduction occurs in the 30-34.9-cm length-class in males and 40-44.9-cm in females. Analysis of the GSI values in the different sampling stations identifies two stations as the breeding areas of M. salmoides in the lake.
The positive correlation between the GSI and the stomach fullness index suggests that the species probably feeds all year round, including the spawning season. Fifty per cent of males and females are mature at 25-29.9-cm and 30-34.9-cm length-classes respectively. The fecundity of fish of 28.4 cm (371 g) to 33 cm (550g) ranged from 1300 to 3524 with a mean of 2203 eggs. Fecundity had no relationship with body length but increased linearly with body weight.  相似文献   

5.
Abstract –  The reproductive activities of two dominant fish species, roach Rutilus rutilus and rudd Scardinius erythrophthalmus were investigated from August 2000 to July 2002 in an oligotrophic lake, Lake Sapanca, in the northwest of Turkey. A total of 907 roach and 593 rudd individuals were examined. Macroscopic appearance of ovary, gonadosomatic index and oocyte diameter frequency distribution suggested that the spawning season of roach and rudd were from early April (13 °C) to late May (18 °C) and from early May (17.5 °C) to late June (23.5 °C), respectively. The spawning cycles of both species showed the same tendency in two successive years. The estimated mean total lengths at first maturity ( L T50) were 12.26 and 14.98 cm for male and female roach, respectively, and 7.12 and 8.10 cm for male and female rudd, respectively. The sizes at 50% maturity corresponded to 3 years for roach and 1 year for rudd, for both sexes. The ratio of males to females was 1.3:1 and 1.2:1 for roach and rudd, respectively. The average condition factor K was 1.21 for rudd and 1.14 for roach, and it was not affected by sex or reproductive effort. Absolute fecundity varied from 7829 to 95,387 eggs between ages 3 and 9 for roach and from 1807 to 35,629 eggs between ages 1 and 7 for rudd. Comparisons of these results with earlier studies from more northern regions revealed that spawning of both species in this area started earlier, but spawning temperature and the duration of spawning was approximately the same.  相似文献   

6.
ABSTRACT: This study clarifies the annual reproductive cycle and the lunar-synchronized spawning of the spiny rabbitfish ( Siganus spinus ) that inhabit the Okinawan waters. Annual and weekly changes in the gonadosomatic index (GSI) and the histological features of the ovaries were checked. Gonadosomatic index was high during the months of May to July, and yolk-laden oocytes were observed in the ovaries from March to July. Some of the ovaries collected during June and July contained oocytes at maturation stage or ovulatory follicles. These results suggest that the spiny rabbitfish undergo active vitellogenesis and spawning from May to July. During the reproductive season (May to July), collection of fish according to the lunar phase revealed that a high GSI occurred around the time of the new moon. Cyclic oocyte development with peaks around the time of the same moon phase was also observed, suggesting that, in Okinawan waters, this species is a lunar-synchronized spawner and spawns three times.  相似文献   

7.
长江中游贝氏(鳖)繁殖生物学研究   总被引：1，自引：0，他引：1  
2016年4-12月在监利长江何王庙故道采集591尾样本,对长江中游贝氏(鳖)(Hemiculter bleekeri)性比、初次性成熟大小、繁殖季节、产卵类型、产卵群体组成及繁殖力等繁殖生物学指标进行了分析.结果显示:贝氏(鳖)总体雌雄性比1.44:1,与1:1存在极显著性差异;繁殖期间雌雄比2.5:1,非繁殖季节雌雄比为0.91:1.繁殖群体年龄结构为1-3龄,以1龄补充群体为主,属于第Ⅱ类型.初次性成熟体长:SL♀50=8.08 cm, SL♂50=8.47 cm,最小观测性成熟个体分别为:雌性7.5 cm,体重6.65 g, 1龄;雄性8.2 cm,体重8.13 g, 1龄.根据成熟系数变化和性腺发育期观察,推测其繁殖季节为4-6月,可能延至7月份.贝氏(鳖)绝对繁殖力为1703~9601粒/尾,平均为(5876.6 ± 1837.8) 粒/尾,与体重、性腺重均呈线性关系,与体长呈幂函数关系.相对繁殖力(FW)为204.7~406.5粒/g,平均(322.3 ± 49.7) 粒/g,与成熟系数呈幂函数相关;相对繁殖力(FL)为212.0~827.6粒/cm,平均(552.4 ± 136.1) 粒/cm,与体重幂函数相关.  相似文献   

8.
The objectives of this study were to evaluate the reproductive cycle, morphological changes of ovary and mobilization of energy reserves in Nile tilapia reared with biofloc technology (BFT). In general, the growth and reproductive performance were highly similar between BFT and Control system (clear water). Difference between the systems was found in the hepatosomatic index (using mixed‐effects models), which suggested that BFT can alter the energy mobilization in the post‐spawning period. The absolute and relative fecundity, fertilization rate, number of larvae produced per female, gonadosomatic index, proportion of oogenesis cells, number of post‐ovulatory and atretic follicles were similar between the two systems. We also did not detect a reduction in the reproductive cycle length in Nile tilapia reared in BFT. Because there was no evidence of the negative effects of BFT on Nile tilapia reproduction, we concluded that BFT might be used for breeder stocking of this species.  相似文献   

9.
The reproductive cycle and batch fecundity of yellow croaker Larimichthys polyactis were examined in 981 specimens (286 males, 695 females) caught from waters around Mokpo, Busan, and Jeju-do (Korea) between February 2008 and January 2009. Males and females with ripe-stage gonads were collected between April and June, at which time the mean gonadosomatic indices were also high, indicating that the spawning season of yellow croaker around the waters off southern Korea occurs from April to June. Degenerating postovulatory follicles as well as oocytes in the migratory-nucleus stage or hydrated stage were found in ripe-stage gonads, suggesting that this species can spawn repeatedly in a season. Batch fecundity in 45 females with migratory-nucleus or hydrated oocytes ranged from 19,396 to 106,311 eggs in fish varying from 20.0 to 26.7 cm in total length and was found to be positively related to total length and body weight. Our findings should assist in implementing a proper stock assessment of yellow croaker around the waters off Korea.  相似文献   

10.
After feeding female Eriocheir sinensis on an optimized formulated diet or fresh razor clam Sinonovacula constricta for 7 months, their reproductive performance and offspring quality were compared. To evaluate diet nutrient contents, the proximate, fatty acid and amino acid compositions of the formulated diet and the razor clam were analysed. The nutritional value of the diets was determined by assessing survival, gonadosomatic index (GSI) and hepatosomatic index (HSI) of female crabs from both diet treatments, together with the percentage of females that spawned, total egg production per female and fecundity (number of eggs g?1 female wet weight). Furthermore, the quality of eggs and newly hatched larvae from the two dietary treatments were determined using the following parameters: egg diameter, wet weight and dry weight, hatchability, proximate and fatty acid profile of eggs, larval carapace length, resistant to starvation and osmotic shock, larval survival and development to the zoea II stage. Higher protein, phospholipids (PL) and amino acids (AA) contents were found in the razor clam while the formulated diet contains higher levels of ash, total lipid (TL) and 18:1n‐9, 18:2n‐6 and 22:6n‐3 fatty acids. Although female crabs fed the two different diets showed similar reproductive performances, newly hatched zoea I larvae produced by the crabs fed the formulated diet had significantly longer mean carapace length and shorter development time to the zoea II stage under identical culture condition (P<0.05). Moreover, dietary fatty acid appeared to have more significant effects on the fatty acid composition of the hepatopancreas than it did on mature ovaries or eggs. This suggests that the fatty acid profile of mature ovaries is indicative of the specific fatty acid required for ovarian development in E. sinensis. In conclusion, our results show that the optimized formulated diet developed in this laboratory can totally replace the razor clam, a broodstock food widely used in E. sinensis hatcheries in China. This encouraging result should facilitate more reliable hatchery production of this important aquaculture species.  相似文献   

11.
The reproductive dynamics of a species is important information to have for the maintenance and reproduction of animals in captivity, for either commercial or conservation purposes. Steindachneridion melanodermatum is an endemic fish that has been reproduced by breeding protocols, but knowledge related to the maturation and reproductive cycle of this species is scarce. The purpose of this research was to observe different parameters related to the reproductive biology of males born in captivity over a 24‐month period to determine the first maturation and reproductive activity of S. melanodermatum males maintained in captivity. Body development changes (weight and length) were observed, and gonadosomatic index (GSI) and plasma sex steroids (testosterone and 17β‐estradiol) were measured monthly. Phases of the reproductive cycle were detected based on macroscopic changes and histological observations of the testes. The obtained data were correlated, demonstrating that the GSI values accompanied testis development and sex steroid peaks. Additionally, immunohistochemistry was performed for the detection of KI‐67, 3β‐HSD and Vasa protein. Our data analysis indicated that the first maturity in males bred in captivity occurred after one year (at 22‐month‐old fish), with a reproductive period occurring from September to November, which is the spring season in the southern hemisphere.  相似文献   

12.
Abstract. A quantitative gonadal index was developed for oysters, Crassostrea virginica (Gmelin. 1791), using polyclonal antibodies from eggs and sperm. Percoll used in the purification of oyster eggs and sperm greatly improved the purity of antigens compared to filtering the egg or sperm through a fine mesh only. The antigen-antibody reaction was tested with indirect sandwich ELISA using alkaline phosphatase-conjugated goat anti-rabbit igG as a secondary antibody. Rabbit anti-oyster egg IgG and anti-oyster sperm IgG initially exhibited a weak cross-reactivity over somatic tissue. Absoring with acetone-dried oyster tissue powder removed this cross-reactivity. Both antisera exhibited strong specific immunological reactions to oyster eggs or sperm respectively. The quantity of eggs or sperm was measured using ELISA and a quantitative gonadosomatic index (dry wt of egg or sperm/dry wt oyster) (GSI) calculated. GSI from ELISA correlated with gonadal stage measured histologically. Monthly mean GSI of female oysters was highest during late spring to early summer (0·157–0·201) and lowest during early winter to early spring (0·002-0·000). Maximum GSI observed during the study was 0·422 for female oysters and 0·446 for male oysters. Female oysters produce 3·7–65·4 million eggs, with an average of 21·1 million during each spawning. A positive correlation was observed between the number of eggs produced and oyster size; the number of eggs in the gonad increased as oyster size (i.e. total dry wt) increased (r= 0·67); however, the relationship was non-linear. Large oysters contained proportionally fewer eggs. Prevalence of Perkinsus marinus parasitism was high, 90–100%, during the study, as was weighted incidence, 1·33 to 2·67, No statistically significant correlation was observed between infection intensity and the per cent weight of oyster eggs or egg number.  相似文献   

13.
基于30余年渤海鱼卵、仔稚鱼历史调查资料的整理分析并结合产卵场补充调查,以1982~1983年周年逐月调查资料为本底,采用多元统计学方法分析30余年渤海鱼类种群早期补充群体群聚特性(物种多样性和关键种群)的季节变化和年代际变化,并掌握结构更替过程中优势种和重要种协同消长规律。分析结果显示,渤海各调查季节(冬季除外)鱼卵、仔稚鱼种类数以及资源丰度指数呈先降后升变动趋势。当前鱼卵种类数仅为20世纪80年代1/2左右,资源丰度不足20世纪80年代的1/10;仔稚鱼种类数和资源丰度仅为20世纪80年代的3/4左右,但冬季仔稚鱼种类数和资源丰度指数呈现上升趋势。各调查时期相同季节鱼卵优势种变化不明显,但仔稚鱼优势种变化幅度超过鱼卵,底层重要经济种类早期补充群体优势度急剧下降;鱼卵和仔稚鱼物种多样性水平在升温季节较高而在降温季节较低,调查期内各季主要呈现先降后升变动趋势。鱼类早期补充群体种类更替现象明显,近年来种类更替率呈现明显加快趋势。各调查时期相同季节各适温类型产卵亲体种数均呈现先降后升变动趋势,但各适温类型种数所占比例和全年综合各适温类型种数所占比例基本稳定。各调查时期相同季节各主要栖所类型产卵亲体种类数也均呈现先降后升变动趋势,全年综合陆架浅水中上层鱼类种数所占比例升高,中底层和底层鱼类所占比例有所下降。近30年在多重外来干扰作用下,渤海鱼类早期补充过程各个关键环节已随其栖息地(产卵场)生境要素发生不可逆变化或变迁。渤海鱼类种群早期补充群体群聚特性和结构更替是环境-捕捞胁迫下鱼类群落内多重生态位的交替失调和渔业资源结构性衰退的具体表现。  相似文献   

14.
基于1985-1986年和2011-2012年"北斗"号渔业调查船在黄海中南部的底拖网数据,对细纹狮子鱼的绝对繁殖力、相对繁殖力、卵径、性腺成熟度等繁殖生物学特征的年代际变化进行了研究。结果表明,黄海中南部细纹狮子鱼卵径分布由1985-1986年的多峰型转变为2011-2012年的双峰型,但平均卵径由(1.1±0.2)mm增加至(1.2±0.1)mm。2011年1月细纹狮子鱼性成熟系数和肥满度比1986年1月有所下降,均与绝对繁殖力无显著相关(P0.05)。1985-1986年细纹狮子鱼个体绝对繁殖力F为9407-84209粒,平均为(37677±3625)粒,体长相对繁殖力FL为446-1981粒/cm,体重相对繁殖力FW为18-157粒/g,均高于2011-2012年细纹狮子鱼个体绝对繁殖力[2984-81614粒,平均为(24728±2822)粒]和相对繁殖力(FL为114-1690粒/cm,FW为15-106粒/g),但协方差检验两个年代间繁殖力参数发现无显著差异。1985-1986年和2011-2012年细纹狮子鱼F与体长均呈幂正相关,与体重呈线性正相关;体长与FL呈线性正相关,与FW呈线性负相关,体重与FL、FW不存在明显相关性。  相似文献   

15.
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   

16.
为了探究丰枯水期里下河腹地典型水体中浮游动物的群落结构特征,通过布设20个采样站点,于2014年丰水期(7月29日)和枯水期(12月24日)对里下河腹地典型水体进行了2次全面调查,并对水质状况进行了评价。结果表明,里下河腹地典型水体共鉴定出浮游动物21种(包括变种和变型),无节幼体1类;其中轮虫最多,共14种,占浮游动物总种数的66.6%;枝角类次之,共6种,占28.6%;桡足类最少,仅1种,占4.8%;各站点浮游动物种类组成和密度均以轮虫和枝角类为主,数量在5~15种,密度变化在9.8~102.2个/L。浮游动物相似性指数在0.18~0.55,平均为0.36,偏向于轻度相似,表明丰水期与枯水期的生境差异较大。优势种的优势度不高,在0.023~0.297;多样性指数在1.73~3.56,均匀度指数在0.67~0.95,表明丰、枯水期里下河腹地典型水体的浮游动物群落信息含量较大、群落结构处于较稳定状态。浮游动物多样性和水质监测结果均表明,枯水期水质优于丰水期,枯水期水质基本处于清洁状态,丰水期水质基本处于中度污染状态;污染源主要为面源污染,且串场河(6号)、新通扬运河(12号)、喜鹊湖(17号)、兴姜河(18号)受人类活动影响较大。  相似文献   

17.
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18.
We investigated the effects of infection by the protozoan Perkinsus olseni on the reproduction of female Manila clams, Ruditapes philippinarum, from a population in Gomso Bay, Korea. The reproductive effort of the clams was assessed by ELISA using a clam egg-specific antibody and was expressed as a weight-based gonadosomatic index (GSI). The number of Perkinsus infecting each clam was estimated from the gills using Ray's fluid thioglycollate medium (RFTM) along with a NaOH digestion assay. We found that reproductive effort was negatively correlated with the intensity of the Perkinsus infection: more heavily infected clams produced fewer eggs during the spawning period from May to August. Frequency of spawning was also negatively correlated with the level of Perkinsus infection; heavily infected clams (HIC) exhibited a single spawning pulse in late July, whereas lightly infected clams (LIC) showed three spawning peaks in mid-May, late July, and late August. Egg production of HIC was only 30–75% of LIC during spawning. The level of total protein in LIC was also higher year round than in HIC. In conclusion, our investigation demonstrates that a high level of Perkinsus infection affects spawning frequency and reduces egg production, which may have long-term impacts on clam recruitment and population growth.  相似文献   

19.
为研究马苏大麻哈鱼(Oncorhynchus masou)资源保护策略和人工繁殖技术,对人工养殖的图们江陆封型马苏大麻哈鱼繁殖力进行了研究。选取122尾不同养殖区域卵巢发育Ⅳ-Ⅴ期的马苏大麻哈鱼样本(其中延吉42尾、山东35尾、北京45尾)进行统计分析。试验马苏大麻哈鱼体重209~845 g,平均为(512±206)g;体长17.0~39.5 cm,平均为(26.81±6.53)cm。结果表明,大麻哈鱼的绝对繁殖力410~3 075粒,平均为(1 485±797)粒;体重相对繁殖力1.93~3.64粒/g,平均为(2.72±0.47)粒/g;体长相对繁殖力23.60~77.85粒/cm,平均为(51.35±17.60)粒/cm;Ⅴ期卵巢性腺指数14.85%~27.93%,平均为(20.97±3.57)%;繁殖力随着体重、体长、性腺指数增加而提高(P0.01)。通过人工驯养和移植培育,改变了马苏大麻哈鱼在自然环境下雌鱼卵巢发育不成熟的现象,而且繁殖力明显提高。移植到北京和山东后,其繁殖力极显著高于原产地(P0.01)。国产陆封型马苏大麻哈鱼具有规模化人工繁育的优势,能够为野生种群资源增殖提供苗种补充。  相似文献   

20.
Abstract  – We investigated several indices (relative weight, mesentery fat, hepatosomatic index, gonadosomatic index, muscle index and visceral somatic index) of largemouth bass Micropterus salmoides (Lacèpede) as a function of season, gender and length to determine how these indices changed with energy content. Length was a significant influence in all comparisons of monthly index measurements, with the exception of the muscle index. All indices, except for the gonadosomatic index, showed few significant differences between sexes for all length groups. Generally, index values were associated with seasonal changes in prey relative abundance and temperature, and the reproductive cycle in mature fish. Total body energy was most influenced by muscle energy stores. Hepatic and gonadal energy of large, sexually mature females decreased considerably with the onset of spawning. Muscle and hepatic energy, to a lesser extent, supported gonadal development. Muscle index values closely tracked seasonal changes in muscle energy, thus providing a useful tool for evaluating seasonal growth and energy patterns. The hepatosomatic index responded to changes in body condition of small and medium fish until June, after which further increases in plumpness caused the utility of this index to decrease. The mesentery fat index provided a useful measure of stored energy available for long-term needs, relative to other energy depots. Seasonal dynamics of invasive condition indices must be considered in light of rapid increases or decreases in body weight (e.g., spawning loss of gametes).  相似文献   

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