Reproductive biology ofAwaous guamensis, an amphidromous Hawaiian goby

Synopsis Spawning season, size at first reproduction, oocyte maturation, and fecundity ofAwaous guamensis, an amphidromous Hawaiian goby, were studied from June 1989 through May 1991 in the Wainiha River, Kau'ai, Hawai'i. Female fish larger than 73 mm standard length (SL) had mature gonads from August through December in 1989 and 1990. Gonadosomatic index (GSI) values for mature females ranged from 0.2 to 14.5 during the spawning season. Male fish larger than 64 mm SL had elevated GSI values from June 1989 through December 1989 and from August 1990 through December 1990. Mature sperm were found in two male fish collected in January and February. GSI values for mature males ranged from less than 0.01 to 4.0 in the spawning season. Size-frequency distributions of measurements of vitellogenic oocyte diameters and microscopic observations of oocytes indicated this species has group-synchronous oocyte development. Ovarian maturation stages examined over a 29-month period suggest that members of the stock spawned at different times within the spawning season, although mass spawning events have been documented for this species. Estimates of clutch sizes from nests measured in situ were comparable to estimates of potential fecundity from in vitro examination of ovaries, and indicated that female fish deposited an entire clutch during a spawning event. No evidence for multiple spawning by an individual fish in a single season was found. However, microscopic observations of brown bodies in some ovaries suggested that individual fish probably spawn more than once in a lifetime.     

Spatio‐temporal dynamics in maturation and spawning of Patagonian toothfish Dissostichus eleginoides on the sub‐Antarctic Kerguelen Plateau

This study investigated maturation and spawning of Patagonian toothfish Dissostichus eleginoides in the Heard Island and McDonald Islands (HIMI) fishery on the Kerguelen Plateau in the Indian Sector of the Southern Ocean based on gonads and otoliths collected between 2004 and 2015 and using histological analyses and calibration of macroscopic staging criteria. Dissostichus eleginoides at HIMI spawn throughout the austral late autumn and winter months of May–August and spawning activity is concentrated on slopes along the west and south of the plateau around HIMI at depths of 1500–1900 m. Comparison between histological analyses and macroscopic gonad staging indicated that many fish that had spawned, as indicated by the presence of post‐ovulatory follicles, returned to a resting stage which was macroscopically indistinguishable from maturing fish. Furthermore, the occurrence of females of all size classes with low gonado‐somatic index and low macroscopic gonad stage during the spawning season suggested that a proportion of mature females did not spawn every year. Age‐at‐maturity estimates, based on the assumption that fish of macroscopic stages ≥2 were mature, decreased between the 2004–2009 and 2010–2015 periods for both sexes. The magnitude of this temporal variation in age at maturity, however, varied between gear types and fishing depths and variable sampling regimes probably influenced these variations. This study highlights the importance of correct interpretation of macroscopic gonad stages and understanding the influence of fishery operations on estimations of life‐history parameters.     

Spawning season and size at sexual maturity of <Emphasis Type="Italic">Kyphosus bigibbus</Emphasis> (Kyphosidae) from northwest Kyushu,Japan

The reproductive characteristics of Kyphosus bigibbus were examined using individuals collected between June 2004 and February 2009 off Nagasaki Peninsula in northwest Kyushu, Japan. The spawning season and size at sexual maturity of this species were characterized based on a gonad index and histological examination of the gonads. The spawning season extends from June to October. This species is assumed to be an indeterminate, multiple-batch spawner. Females reached sexual maturity at larger size than males (fork length at 50% sexual maturity: males 284 mm, females 360 mm).     

Gonad development and reproductive cycle of the white‐spotted rabbitfish Siganus canaliculatus (Park, 1797) in Palompon,Leyte, Eastern Visayas,Philippines

The siganid production in the Philippines is continuously declining from 2007 up to present. In Palompon, Leyte, annual yield of siganids, particularly Siganus canaliculatus (Park, 1797) also showed a decreasing trend of total production. This is consistent that this stock is under heavy pressure, and when left unmanaged, this could lead to further overexploitation and the collapse of the stock in the long run. Regardless of this, detailed reproductive biology and potential of this species are very few in the Philippines. Therefore, this study was conducted to provide information on the reproductive biology and breeding cycle of S. canaliculatus in Palompon, Leyte where fishing pressure is high and sound management formulation is necessary. S. canaliculatus is a group‐synchronous, multiple spawners with skewed sex ratio where males predominates over females. Maturity stages based on macroscopic examinations identified four maturity stages (immature, developing, mature and spent) while six maturity stages (immature, developing, mature, spawning, spent and re‐developing) were identified through histological analysis. A single ovo‐testis was identified among the 669 specimens examined. Based on histological sections, the smallest size of mature male was 5.5 cm standard length, and the smallest mature female was 7.1 cm standard length. On the other hand, length at first maturity for mature fish were 8.1 cm standard length for males and 9.7 cm standard length for females. Two defined peaks of gonadosomatic index were identified in both sexes: a major peak from February to May and a minor protracted one from July to December. Mature and older ovaries and testes occurred throughout the year, an indication of your round breeding season of S. canaliculatus in Palompon. Implementing a fishing ban during the major and the minor breeding spawning peaks would allow the mature and older individuals to contribute first to the population; allowing the continuity of the stock.     

Sexual maturity cycle and spawning of Greenland halibut Reinhardtius hippoglossoides in the Davis Strait

Female sexual maturation cycle and the main spawning time of Greenland halibut Reinhardtius hippoglossoides in the Davis Strait were studied through regularly collected samples during 1 year starting in spring 2003. Samples were collected from the southern slope of the Davis Strait Ridge between Canada and Greenland in the depth range 1000–1500 m. Female sexual maturation was described using different approaches: gonado‐somatic index, visual macroscopic maturity stage index, histological microscopic maturity index and oocyte diameter measurements. A significant increase in the gonado‐somatic index was seen from September onwards until February with a maximum estimated value of 18%. The proportion of mature fish increased from December until March. At the same time, the proportion of females with a low gonado‐somatic index also increased from February, indicating that spawning had occurred and females were recovering. Oocyte diameter distribution revealed a leading cohort development during autumn through to December to February. A coupling between sexual maturity and fish condition was seen for females in maturing condition indicating a steady build up of stored energy in the liver from June to November.     

Reproductive biology of Bagrus docmak in the Victoria Nile,Uganda

Aspects of the reproductive biology of Bagrus docmak in the Victoria Nile were investigated between November 2005 and October 2006. Macroscopic and histological analysis of the gonads confirmed it as an asynchronous batch spawner which spawns throughout the year with bimodal spawning peaks coinciding with rainfall seasons. The first spawning peak occurred from March to May, the second from September to November. The sex ratio did not significantly deviate from 1:1. Length at sexual maturity was 33.6 cm and 31.6 cm fork length (FL) for females and males, respectively. Batch fecundity ranged from 1 000 eggs in 34 cm FL fish to 43 000 eggs in 79 cm FL fish, and correlated linearly with FL (r = 0.72) and body weight (r = 0.79). Mean relative batch fecundity was 6 eggs g^?1 (SE 2). These results could guide research into the possibility of artificially inducing the fish to spawn, and its subsequent culture.     

Reproductive strategy of the Patagonian catfish Hatcheria macraei

This study describes the reproductive strategy of the stream‐dwelling catfish Hatcheria macraei in the Pichileufu River, Argentina. Gonad maturity phases, classified on the basis of histological analysis, stages of gamete development and the frequency distribution of oocyte size, were correlated with macroscopic features of the gonads. Hatcheria macraei has a cystovarian ovary, asynchronous oocyte development and lobular testes. Five oocyte and four spermatogenic stages were identified and related to macroscopic gonad characteristics, making it possible to divide gonad development into five phases for females and males. Mature oocyte diameter ranged from 922 to 1935 µm. Absolute fecundity in mature females varied from 115 to 480 oocytes. Hatcheria macraei has multiple spawning during a protracted reproductive season that extends from December to April. This, together with its small size, is characteristic of an opportunistic reproductive strategy, commonly found in species that inhabit adverse and unpredictable environments, such as the low‐order rivers of Patagonia.     

Annual reproductive cycle and sexual dimorphism in the dragonet,repomucenus valenciennei, in tokyo bay, japan

The annual reproductive cycle of the dragonet,Repomucenus valenciennei, from Tokyo Bay, Japan, was studied by analysis of seasonal trends in gonadosomatic indices and histological observations of gonads. Sexual dimorphism in the growth of several body parts relative to standard length (SL) and changes in color pattern of the first dorsal fin with growth were also investigated. The spawning season lasted from spring (April [1991] or February [1992]) to autumn (October) with two spawning peaks, in spring and autumn. In spring, only one-year-old (age 1+) fish spawned, age 0+ females not spawning until autumn, at which time they had reached age 1+. Likewise, histological observations of males indicated that testes had reached full maturity by 80 mm SL (age 1+). The minimum mature size of females was estimated as 60 mm SL. In males 45–80 mm SL, the first spine of the first dorsal fin, last ray of the second dorsal fin, last ray of the anal fin, and caudal fin ray showed strongly positive allometry, indicating rapid growth of these structures relative to SL. Subsequently, their growth returned to an isometric pattern in males>80 mm SL. In females, on the other hand, the same body parts showed slightly positive allometry throughout their growth. The color pattern on the first dorsal fin also changed in males 45–80 mm SL.     

Cytomorphology of female and male gonads in Antarctic toothfish <Emphasis Type="Italic">Dissosctichus mawsoni</Emphasis> (Nototheniidae) from the Ross Sea in the summer period

Results of histological analysis of gonads of female and male Antarctic toothfish Dissostichus mawsoni caught in the Ross Sea of the Pacific sector in the period of Antarctic summer (December–February) 2004–2005 are presented. Morphological indices and index of gonad maturity are described and ecological criteria of assessment of maturity stages of ovaries, cytological indices of oocytes, and the type of toothfish oogenesis are determined. It was established that in the period of fishing Antarctic toothfish, females and males with gonads at maturity stage III dominate. Ovaries contain two groups of oocytes of the period of trophoplasmatic growth and large oocytes of the nearest spawning season that comprise the smallest proportion of total sex cells. In the testes of two male toothfish, the primary fusion of renal and generative tissues was revealed. It is suggested that the termination of gonad maturity of toothfish takes place from March to April, and spawning takes place from June to August.     

The multiple spawning pattern of weakfish in the Chesapeake Bay and Middle Atlantic Bight

Weakfish Cynoscion regalis were collected from commercial fisheries in the Chesapeake Bay and the Middle Atlantic Bight (n=4380) during 1989–1992 and their reproductive biology assessed using the gonadosomatic index, macroscopic gonad stages, oocyte diameter distributions, microscopic whole oocyte analysis and histology. Sex ratios were approximately 3:1, females to males, in 1990–1992. Most fish (90%) attained sexual maturity by age 1 and at a small size. Estimated mean length at first maturity was: 164mm total length (TL) for males, and 170 mm TL for females. Weakfish spawn within the Chesapeake Bay, as far north as the Virginia/ Maryland border. Although spawning occurred during May–August and gonad development and initiation of spawning was synchronous, cessation of spawning was asynchronous. There was no indication that older fish exhibited a more extended spawning season than younger fish. Weakfish are multiple spawners with indeterminate fecundity. Oocyte development is asynchronous with oocytes of all stages being present in developed ovaries. Because of the complex and dynamic weakfish ovarian cycle, typical methods of assessing reproduction, such as the GSI and macroscopic gonad stages, are inadequate for this species if not used in conjunction with more detailed methods such as histology.     

Biology of the amphioxus,Branchiostoma belcheri in the Ariake Sea,Japan II. Reproduction

We investigated the reproduction of the amphioxus Branchiostoma belcheri in the southern Ariake Sea, Japan, from 1999 to 2002. Gonads were very small or almost absent from September to December and began to develop in January. Changes in the gonad length index indicated that spawning began in mid June, after the gonads had attained maximum size. Although most gametes were extruded during the first spawning, some remained in the gonads. Shrunken gonads were much smaller but contained gametes, and the second spawning occurred around 10 July. It was unclear whether all adults spawned twice, but a large proportion of individuals did. After the first spawning, both males and females lost 30% of their body weight. Most one-year-old individuals did not spawn, and the minimum size at maturity was ca. 20 mm. We found no termination of reproduction among very large individuals. The average number of gonads was significantly larger on the right side of the body (26.2 in males and 26.1 in females) than on the left side (24.0 in males and 23.5 in females). We found two hermaphrodites in a total of 11,184 specimens examined. Each had four or three ovaries among a total of 45 or 54 gonads.     

Reproductive biology of the marine catfish,Genidens genidens (Siluriformes,Ariidae), in the Jacarepaguá Lagoon system,Rio de Janeiro,Brazil

Synopsis Genidens genidens was sampled at the Jacarepaguá Lagoon system (23° S, 43° W), Rio de Janeiro State, Brazil, using cast nets and beach seines, to study its reproductive biology. Spawning period extended from October to February, but was more intense from December to January, coinciding with high surface water temperature and low salinity in the area. After spawning, males mouthbrood the eggs for two to three months until development is completed. Mean length at first maturity for females was approximately 180 mm TL, and at 250 mm TL, all females were mature. Batch fecundity was very low, ranging from 7 to 30 eggs for fish with 170 mm TL (37.0 g TW) to 228 mm TL (104.0 g TW), respectively, and was linearly related to fish total length and total weight. Sexual dimorphism starts after sexual maturity, with females having relatively longer pelvic fins than males. Both sexes exhibited very low condition during the spawning season, probably due to changes in feeding activity related to the reproductive cycle. A strong predominance of males during the main spawning/brooding period suggests that females migrate from the area after spawning is completed.Present address: Virginia Institute of Marine Science, School of Marine Science, The College of William and MaryGloucester Point, VA 23062, U.S.A.     

Gametogenesis and reproductive strategies in some species of the Antarctic fish genus Trematomus (Nototheniidae) from Terra Nova Bay, Ross Sea

Species of the genus Trematomus are the most common nototheniids in the High-Antarctic Zone, and several live sympatrically on the Ross Sea continental shelf. Histological analysis of gonadal development of T. bernacchii, T. hansoni and T. newnesi was carried out on samples collected during the austral summer in the coastal waters of Terra Nova Bay, western Ross Sea. Gonads of both females and males of the three species were described based on macroscopic and histologic scales. Histologically, both males and females of T. bernacchii were in postspawning or in early maturing condition, thus indicating that they recently completed spawning. Conversely, most specimens of T. hansoni were in spawning condition, as evidenced by the histological appearance of gonads and by the high value of gonado-somatic index (GSI) of females between 20 and 36%. In the same period, females of T. newnesi had maturing ovaries, whereas males were at an early developmental stage of maturity. In all species, the testicular structure closely resembled the unrestricted spermatogonial type, although spermatogonia were more concentrated in the blind end of tubules. On the basis of the pattern of oocyte maturity observed within the ovarian lamellae, all Trematomus had a group synchronous ovary, as commonly reported in Antarctic fish. Furthermore, the presence of oocytes showing the commencement of yolk deposition in spent females confirms that vitellogenesis is a slow process, extending over at least 1 year. The reproductive strategies of Trematomus are discussed in terms of timing of the spawning season of each species as a function of the seasonal production cycle and of the interspecific relationships. The spawning activities of the three species investigated appeared to be mismatched with respect to time as well as location within the range of distribution of each.     

Reproductive biology of wahoo, Acanthocybium solandri, off eastern Australia

A dearth of basic biological information for wahoo, Acanthocybium solandri, currently hinders the ability of scientists and managers to assess population sustainability and appropriately manage the dramatically increasing global catch. This study examined the gonads of 382 wahoo collected off eastern Australia during 2008–2011 to quantify their reproductive biology in the region. The overall sex ratio of the sample was 3.2:1 (females:males), however this differed significantly among fishing sectors and areas. The estimated fork length at which 50 % of female wahoo reach maturity was 1,046 mm. Similar to the Atlantic Ocean, female wahoo have a protracted summer spawning season during October-February. The mean spawning frequency of female wahoo was uncertain but may be approximately 2–3 days, with evidence of fish actively spawning on consecutive days. Batch fecundity of females was positively correlated with fish size and estimates ranged between 0.65 and 5.12 million oocytes. Relative fecundity was estimated at 122.0 (±9.7) oocytes per gram of ovary free body weight and did not differ with fish size or throughout the spawning season. Estimation of reproductive parameters such as size- and age-at-maturity may facilitate the construction of per-recruit stock assessments of wahoo in the region.     

Reproductive strategy of Leporinus piau (Fowler, 1941), a neotropical freshwater fish from the semi‐arid region of Brazil

This study concerns the reproductive strategy of the freshwater fish, Leporinus piau, native to the Brazilian semi‐arid region. The hypothesis of this work predicts that the species would spawn during the rainy season, presenting a seasonal reproductive strategy. The study investigated the structure of total body length and body mass, sex ratio, body size at first sexual maturity, developmental stages of gonads, fecundity, gonadosomatic index (GSI), condition factor (K) and the spawning season of L. piau. Twelve monthly samplings (mean n = 18) were carried out in 2009 and environmental parameters such as rainfall, temperature, pH, electrical conductivity and concentration of dissolved oxygen of water were registered. The sampled population of L. piau (n = 211) showed a slight predominance of males (55%), but with larger and heavier females. First sexual maturation in males occurred earlier (16.5 cm total length) than in females (20.5 cm total length). The species is a total spawner with an average fecundity of 55 000 mature oocytes. Rainfall (225 ± 7.2 mm) and concentration of dissolved oxygen (8.5 ± 0.2 mg L^?1) acted as influential factors during the spawning season. The monthly GSI shows that spawning starts when the rainy season is at its maximum and ends synchronously (females r = 0.91; males r = 0.89) with the end of the rainy season. L. piau presents a seasonal reproductive strategy with high reproductive output, providing a population increase and exploitation of the environmental resources.     

Gonad development and size‐at‐maturity of silver therapon Leiopotherapon plumbeus (Kner 1864; Teleostei:Terapontidae) in tropical volcanic lakes in south Luzon,Philippines

Gonad development of the silver therapon Leiopotherapon plumbeus in two volcanic crater  lake  habitats (Sampaloc Lake, Taal Lake) in south Luzon, Philippines was examined during the annual reproductive cycle. The minimum body size‐at‐maturity of fish in these two lake habitats was also compared. Four gonad development stages were characterized as basis for the classification of ovarian (immature, maturing, mature, spawned) and testicular maturation (immature, maturing, mature) phases. The occurrence of all development stages in individual gonads suggest an asynchronous development whereby advanced stages are recruited continuously from a pool of younger stage germ cells to result in elevated female and male GSI throughout the annual cycle due to active gonadogenesis. Together with the increasing occurrence of advanced stage oocytes and spermatozoa from March until October, the elevated GSI of fish may indicate peak gonadal growth during the onset of the dry season (December–January) for eventual spawning from the beginning (May–June) until the end of the wet season (October–November). In both lake habitats, male fish were smaller than females but, regardless of sex, the minimum size‐at‐maturity of fish in Sampaloc Lake was significantly smaller than fish in Taal Lake. Overall, asynchronous development during oogenesis and spermatogenesis allows for year‐round reproduction of silver therapon, with elevated gonad growth in the dry season in preparation for spawning during the wet season. Compared with fish in Taal Lake, a smaller size‐at‐maturity of fish in Sampaloc Lake may be a response of the wild fishery stock to long‐term high fishing mortality and degradation of the lake habitat.     

Maturation and spawning of a gobiid fish, Oligolepis acutipennis (Cuv. & Val.), from the south-west coast of India

The breeding biology of Oligolepis acutipennis (C. & V.), a gobiid fish abundant in the estuaries and brackish water tracts of the south-west coast of India was studied. Data on the intra-ovarian development of ova, the breeding season, spawning frequency, size at first maturity and sex-ratio were based on observations for 1 year. The size distribution of ova showed no significant variation between different regions of the ovary. The gonads were classified into five maturity stages. The sequence of development of ova to maturity indicated two batches of ova developed in a single ovary in a year. The minimum size at first maturity of females was less than that of males. Seasonal variation in gonad weight and the percentage occurrence of various maturity stages of gonads showed that the fish has a protracted breeding period in which two seasons can be recognized. The females dominate over males in numbers except in the non-breeding months.     

额尔齐斯河银鲫繁殖生物学研究

2013年4—10月在额尔齐斯河中国段下游采集了546尾银鲫(Carassius auratus gibelio)样本, 依据传统生物学和组织学方法, 对额尔齐斯河银鲫的繁殖生物学特性进行了分析和研究。统计表明, 额尔齐斯河银鲫的性比(雌/雄)为10.84﹕1。根据卵母细胞和精细胞发育及比例情况, 将银鲫卵巢和精巢发育分别划分为6期。依据不同性腺发育期比例、性体指数和卵径频率分布, 推测银鲫为同步产卵鱼类, 繁殖期为5—7月, 6月为高峰期。采用Logistic回归方程获得其初次性成熟体长(SL₅₀)和年龄(A₅₀)分别为: 雌鱼161 mm和2.3龄; 雄鱼135 mm和1.9龄。绝对繁殖力为(42453±28205)粒, 相对繁殖力为(98.19±34.6)粒/g。绝对繁殖力与体长线性相关性较低, 与体重呈幂指数相关, 但与年龄及卵巢重的相关性不显著。研究进一步丰富了额尔齐斯河银鲫生物学研究资料, 为其资源养护和可持续利用提供科学依据。     

Sexuality, sex change and maturation patterns in the yellowfin seabream, Acanthopagrus latus (Teleostei: Sparidae) (Houttuyn, 1782)

Macroscopic and histological studies were carried out to describe the reproductive styles and sex reversal and to follow gonadal changes in captive yellowfin seabream during the second year of life. Four reproductive styles are found in Acanthopagrus latus (Houttuyn, 1782): (i) males and females (gonochorism), (ii) functional males, (iii) transitionals and (iv) functional females. The species is a protandric hermaphrodite and begins life as a functional male with testicular zone undergoing active spermatogenesis, while the ovarian zone is arrested at the primary growth (perinucleolar) phase. Males and females were encountered in virtually all size‐classes. Functional males outnumbered the functional females in all size‐classes in which they were encountered. Sex reversal begins in the transitionals from July to August, after spawning in the functional males, at 14.9–20.2 cm standard length (SL) and, by November, maturation of the ovarian tissue begins. A. latus in cages in Kuwait waters spawns from January to April with a peak in February for males, and a peak in March for females and transitionals. Spawning begins in the 18.3–20.2 cm size‐range fish, peaking in the 20.3–22.2 cm size‐range in both males and females and also in the transitionals, although a few of the latter spawn from 14.9 cm SL. In relation to age, spawning begins at 20 months in males and peaks at 21 months. Females begin to spawn at 21 months with a peak at 22 months, while transitionals generally begin to spawn at 20 months, although a few 14–15‐month‐old sex‐changing individuals were encountered. Temperature, either alone or in combination with other unknown factors, triggers spawning in A. latus.     

Reproduction in the greenback grey mullet, Liza subviridis (Valenciennes, 1836)

This paper presents data on the reproductive biology of Liza subviridis , a little studied mullet species. The fish is heterosexual, exhibiting external fertilization. Six maturity stages can be macroscopically identified in the testes and seven in the ovaries. The macroscopic changes in the gonads are manifestations of histological changes occurring in the development of sperm cells and oocytes. First sexual maturity is attained in the length ranges of 9.5–11.5 cm and 10.5–11.5 cm in male and female fish respectively. The fecundity for fish measuring 10.3–13.9 cm in standard length ranged from 40 000–145 000 eggs. The relationship between fecundity ( F ) and length ( L ) can be represented as: F = 1.9044 L ^4.2998. The spawning duration in L. subviridis is restricted to a short and definite period, with all ripe ova being released within a single spawning act. A pronounced spawning season can be detected to extend from June to November. However, during off-seasons, some spawning also occurs. The correlations between spawning, rainfall and air temperature is discussed.