Comparative study of reproductive biology in single- and multiple-spawner cyprinid fish. I. Morphological and histological features

To clarify the dynamics and regulation of oogenesis in single- and multiple-spawning cyprinid fish with group-synchronous oocyte development, a multidisciplinary approach to their reproduction was undertaken using three species from the River Meuse (Belgium): the roach Rutilus rutilus as a single spawner, and the bleak Alburnus alburnus and the white bream Blicca bjoerkna as multiple spawners. The gonadosomatic index (GSI) and histomorphometric changes (distribution of oocyte size, relative proportion of the various oocyte stages) in the ovary are compared. Different patterns of GSI and oocyte growth were observed both between the single- and multiple-spawner fish and between the two multiple spawners. Maximum GSIs were higher in roach (21%) than in bleak and white bream (17.7 and 14.5%, respectively), and compared to the rapid decline of GSI in the roach population, the GSI of multiple spawners decreased progressively during the spawning season. In roach, a short gonadal quiescent period and an early onset of vitellogenesis was recorded from late summer onwards whereas, in bleak and white bream, exogenous vitellogenesis was not systematically observed before winter. A protracted spawning season and/or a low water temperature in autumn are hypothesized to explain this long period of gonadal quiescence. In bleak, during the spawning season, the oocytes recruited arose from the stock of endogenous vitellogenesis and attained the final maturation stage very rapidly. This recruitment occurred during the whole spawning season. In white bream, the differentiation of vitellogenic oocytes from smaller oocytes was completed before the onset of the spawning season. During the spawning period, the proportion of vitellogenic oocytes decreased progressively whereas the percentage of oocytes in the final maturation stage remained approximately constant.     

Influence of the hydrological regime in the lower reaches of the Volga delta on natural fish reproduction

This article considers the influence of the hydrological regime in the lower reaches of the Volga delta (based on the example of the Damchiksky site of the Astrakhan Reserve) during high water periods in the low-water year of 2012 and medium-water year of 2013 on the abundance of producers entering for spawning and the density of aggregations of juveniles of roach Rutilus caspicus, vulgaris rudd Scardinius erythrophthalmus, and river perch Perca fluviatilis. It is shown that the fish mass spawning in 2013 was more effective and occurred on floodplain spawning areas with the sequential succession of the investigated species, while the fish spawning was observed in eriks and was less effective in 2012. It was revealed that vulgaris rudd shows the highest adaptation to insufficient watering conditions.     

Reproduction and population density affect humoral immunity in bank voles under field experimental conditions

Density dependence is a common feature in the dynamics of animal populations. Availability of food resources critical to immunity is likely to be one of the mechanisms mediating the effect of population density on individual fitness. The ability to mount an immune response to an antigen is also affected by levels of immunosuppressive hormones associated with reproduction or mediating the response to ecological and social stress. We assessed variation in condition and intensity of humoral immune response to a T-cell-dependent antigen in bank voles (Clethrionomys glareolus) by experimentally altering population density before immunisation. Consistent with our prediction, males had lower humoral immunocompetence in the breeding than in the non-breeding season. Contrary to our expectation, males did not show enhanced immunocompetence and females showed depressed humoral immune response under experimentally lowered population density. Variation of immune response in relation to population density depended on sex, with females but not males showing lower immune response under experimentally reduced density. We conclude that humoral immunity of bank voles was affected by reproduction and social environment rather than by population density. Received: 2 November 1999 / Accepted: 22 March 2000     

Reproductive and growth strategies of the red roach, Rutilus arcasii (Steindachner, 1866), in two contrasting tributaries of the River Duero, Spain

The life-histories of red roach were assessed in the R. Moros and the R. Ucero, two contrasting tributaries of the R. Duero. Growth occurred from April to October and Ucero red roach were larger than those in the Moros from their second year onwards. Condition increased with gonad development and abruptly decreased after spawning in both populations. The condition of Ucero fish recovered during the summer, but that of the Moros fish remained low. The same year classes (1980 and 1982) dominated both populations. River Moros red roach spawned in a 4-week period between the end of April and early June, while the spawning season of Ucero red roach lasted until August. The length to fecundity relationship was similar for both populations, and fecundity and ovum size increased with fish length. The life-history traits of these red roach populations are discussed in relation to current life-history theories.     

Comparative study of reproductive biology in single and multiple-spawner cyprinid fish. II. Sex steroid and plasma protein phosphorus concentrations

The dynamics and regulation of oogenesis in single and multiple-spawner cyprinid fish showing group-synchronous oocyte development, was investigated in three species from the River Meuse (Belgium): the roach Rutilus rutilus as a single spawner, and the bleak Alburnus alburnus and the white bream Blicca bjoerkna as multiple spawners. This paper compares the seasonal profiles of sex steroids (oestradiol-17β, testosterone and 17,20β-dihydroxy-4-pregnen-3-one) and plasma alkali-labile protein phosphorus. Different patterns of plasma oestradiol-17β (E2) and plasma protein phosphorus (PPP) have been observed not only between the single and the multiple spawner fish, but also among the two multiple spawners. In roach, two increases of E2 levels were observed. The first occurred in September after a short gonadal quiescent period, and coincided with the increase of the PPP at the onset of exogenous vitellogenesis. The second took place in spring before the spawning season. The low PPP recorded during that period probably reflected its rapid incorporation by the oocytes. In both multiple spawners, highest values of PPP were recorded just before the spawning season. In white bream, the PPP declined progressively once the differentiation of exogenous vitellogenic oocytes was completed before the onset of the spawning season. In bleak, PPP levels remained high throughout the spawning season and corresponded to a sustained oocyte recruitment during the whole of this period. Regardless of the pattern of oocyte growth recruitment, the E2 concentrations were high in both multiple spawner species during the breeding season. In the three species, testosterone levels remained low regardless of the maturation stage (ranging from 0.6 to 13.4ng ml^?1). Except for relatively high concentrations of 17,20βP in roach during final maturation and postspawning stages (20 and 28 ng ml^?1, respectively), low levels of this steroid were measured in these cyprinids, and especially in the multiple spawner fish. The role of this progestogen as the maturation inducing Steroid is discussed.     

Ranges of Regulation of Sodium, Potassium, Calcium, Magnesium Concentrations in Plasma, Erythrocytes, and Muscle Tissue of Rutilus rutilus under Natural Conditions

As a result of studies for 3 years on the roach Ratilus ratilus under natural conditions, it was shown that the Na, K, Ca, and Mg content in the blood plasma, erythrocytes, and muscle tissue as well as muscle water were maintained year after year within definite ranges characterizing normal values for these parameters. Comparison of variations in the Na, K, Ca, Mg blood plasma concentrations in different fish species revealed the presence of common limits for each of these elements. Throughout the year the most essential changes in the roach blood and tissue cation levels were found during reproduction period. During spawning the fish are characterized by the state of acute stress with parameters indicating a decrease in stability and exhaustion of adaptive possibilities in animals. Intensification of defense reactions, including those providing maintenance of the water–salt homeostasis occurs shortly before spawning for a preliminary preparation to the stress situation.     

Occurrence of cyprinids in fish ladders in relation to flow

To analyse the relationship between spawning migrations and flow, cyprinids from ten fish ladders of the Elbe River (Czech Republic) were collected during the period of spawning migrations (April–June) in 1996, 2000 and 2001. Number of species and individuals in the fish ladders increased with increasing flow up to medium values, followed by further decrease during high flows, whilst length of individuals increased with increasing flow. Moreover, occurrence of four the most numerous species (bleak, roach, silver bream and barbel) showed species specific differences in response to flow variability. In early spring, the highest number of bleak in fish ladders occurred during the low flow, whilst later increased with increasing flow. Occurrence of roach and silver bream achieved the maximum during the medium flow values across the whole studied period. In opposite, occurrence of barbel increased with increasing flows during the whole period. Furthermore, it can be assumed that occurrence of fish in ladders was associated not only with spawning migrations but also reflected shifts in local fish distribution in response to flow variability in the main channel.     

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.     

Assessment of Maturity,Reproduction and Reproductive Potentials of Torpedo Scad, <Emphasis Type="Italic">Megalaspis cordyla</Emphasis> (Linnaeus, 1758) from Northern Arabian Sea Coast of Pakistan

Port landing specimens of torpedo scad, Megalaspis cordyla were collected at monthly intervals from August 2013 to June 2014 from the northern Arabian Sea coast of Pakistan. The life history characteristics revealed that torpedo scad has a prolonged breeding season which occurred with two peaks: from May to June and from November to February. The spawning seasonality was also validated with microscopic gonad examination.The highest GSI value was noted in May and January whereas the lowest in November was recorded for both sexes. The age at which individuals of both sexes become 50% mature (t₅₀) was estimated as 2.44 year. Life span (t_max) calculated as 3.96 years for male and females. The size of 270 and 265 mm at which 50% individuals attained sexual maturity (L₅₀) was determined for males and females respectively. The reproductive potential (fecundity)was made from ten ripe females ranged from 29–43.8 cm TL and weighing 220–540 g of IV–V developmental stage was enumerated as 32306–236677 eggs (CV = 2.135) with an average number of eggs 86544 counted per ripe female/season. This study contains fundamental data of an important fish species in the northern Arabian Sea coast of Pakistan. It provides vital information to the fisheries managers for implementation on sustainable use of the resource during spawning season.     

假单胞菌减毒活疫苗免疫后的大黄鱼脾脏转录组分析

大黄鱼是中国东部沿海养殖的重要经济鱼类品种,多年来受到假单胞菌引起的内脏白点病的危害,疫苗免疫是预防该病的理想手段,减毒活疫苗(live attenuated vaccine,LAV)或DNA疫苗等能有效刺激宿主细胞免疫应答的疫苗可能是该菌疫苗发展的重要方向。为了评估减毒活疫苗的有效性,解悉大黄鱼对疫苗的免疫应答机制,本研究以重要毒力基因缺失的减毒活菌株ΔpcrV NB2011免疫鱼体,在免疫后0 h和48 h分别采取实验鱼的脾脏组织进行转录组测序。通过美吉云平台在线分析,一共注释了30 438条Unigene和70 618条转录本。筛选出上调和下调表达基因分别为311个和313个,其中免疫相关的显著性差异基因28个,涉及抗原加工呈递、补体系统、细胞因子、模式识别受体和吞噬作用,尤其是MHCI型抗原加工和递呈通路显著上调。对上调表达基因进行KEGG富集分析,涉及的最主要通路包括谷胱甘肽代谢通路、精氨酸-脯氨酸代谢通路、抗原提呈与加工通路和溶菌酶通路等。选取5个显著性差异表达的免疫相关基因进行qRT-PCR验证,验证结果与测序结果变化趋势基本一致,提示了LAV免疫后有效激发鱼体的细胞免疫应答,有助于快速清除胞内病原。本研究部分揭示了大黄鱼对致病性假单胞菌LAV的免疫应答机制,可以为疫苗的研制提供科学依据。     

Male Siamese fighting fish use gill flaring as the first display towards territorial intruders

The Siamese fighting fish (Betta splendens) is well known as an aggressive fish with unique spawning and parental care behavior. During reproduction, male fish construct a bubble nest, court females, protect the brood, and defend the territory through aggressive displays. Aggression in male Siamese fighting fish has long been the subject of investigation; however, the kinematics of aggression during contests have been largely overlooked. Here we investigated how nest-holding, male Siamese fighting fish use two different types of displays, gill flaring and fin spreading, towards intruders during various reproductive phases; before (BB) and after bubble nest building, and after spawning (AS), and hatching (AH). Males were more aggressive towards male than female intruders and the level of aggression changed significantly between reproductive phases. Gill flaring, the more energetically costly display, was the dominant initial display towards male and female intruders in BB, AS, AH phases. However, defending males switched to fin spreading after prolonged exposure to intruders. The results suggest that Siamese fighting fish use gill flaring as an acute response in order to defend their territory; this response may be replaced by fin spreading as a chronic response, probably to reduce the energetic costs during the contest.     

The administration of exogenous prostaglandin may improve ovulation in pacu (Piaractus mesopotamicus)

Based on the reports of unsuccessful ovulation in pacu (Piaractus mesopotamicus) by fish farmers and researchers undertaking artificial reproduction programs, we evaluated the use of prostaglandin F (PGF) to improve pacu ovulation. This study was conducted during two spawning seasons (2009/2010 and 2010/2011) with two samplings in the first season and one sampling in the second season. A total of 45 females was sampled in this study. The control group was injected with carp pituitary extract (crude extract, 6 mg/kg), and the treatment group received PGF (2 mL per fish in the 2009/2010 season and 5 mL per fish in the 2010/2011 season) in addition to the crude extract. In both seasons, 100% (N = 4, 2009/2010 first sampling; N = 5, 2009/2010 second sampling; and N = 3, 2010/2011) of the PGF-treated fish spawned. In contrast, 53.0% (N = 9) and 83.3% (N = 10) of the control fish spawned in the first and second samplings of the 2009/2010 season, respectively, and only 25.0% (N = 1) spawned in the 2010/2011 season. Fecundity, fertility, and hatching rates did not differ (P > 0.05) between the treated and control fish. Based on oocyte volume frequency analysis, ovaries of the control fish had more (P < 0.05) vitellogenic oocytes with germinal vesicle breakdown that remained unovulated after spawning, whereas more (P < 0.05) of previtellogenic oocytes were present in the ovaries of the PGF-treated fish. In conclusion, administration of exogenous prostaglandin may improve the outcome of hormonally induced spawning in tropical migratory fish.     

Vertical migration in streams: seasonal use of the hyporheic zone by the spinous loach <Emphasis Type="Italic">Cobitis shikokuensis</Emphasis>

Vertical hydrological connectivity between the surface stream and benthic and hyporheic zones plays a key ecological role in the biodiversity of lotic ecosystems because it allows surface and benthic organisms to use the hyporheic zone as a seasonal habitat and refuge. Use of the hyporheic zone by surface/benthic organisms has been well studied in invertebrates, but little is known about the importance of this connectivity for fishes. We investigated streambed surface and hyporheic densities (5–10, 15–20 and 20–25 cm below the streambed surface) of a stream fish, Cobitis shikokuensis, over a 20-month period in the Shigenobu River, southwestern Japan, to test the hypothesis that it uses the hyporheic zone for spawning and overwintering. In total, 1,804 individuals (13–58 mm total length) were captured from 33 streambed surface samplings and 102 individuals (10–46 mm total length) were present in 1,147 samples of 57 hyporheic samplings. Population densities in both zones peaked in late summer–early autumn due to the recruitment of age 0+ fish and a female with eggs was found in the hyporheic zone during the reproductive season. Both 0+ and older fish were absent from the streambed surface during winter, and fish densities were also lower in the hyporheic zone at this time. However, the vertical distribution of the fish tended to be skewed towards the deeper hyporheic layers from autumn to spring. These findings indicate that C. shikokuensis vertically migrates between the streambed surface and the hyporheic zone for spawning, rearing and overwintering, suggesting that the integrity of vertical hydrological connectivity in lotic systems is crucial for certain fish species.     

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.     

Movements of lumpsucker females in a northern Norwegian fjord during the spawning season

The lumpsucker Cyclopterus lumpus is distributed throughout the North Atlantic Ocean and migrates considerable distances between offshore feeding areas and shallow inshore spawning grounds. The number of the lumpsucker has declined since the mid 1980s, probably as a result of overexploitation. The lumpsucker is the preferred host of the sea louse Caligus elongates, which is a problem for marine aquaculture. However, little is known about the biology of the lumpsucker. The aims of the study were to 1) examine the movements of female lumpsucker during the spawning migration, and 2) assess the potential for lumpsucker to act as a vector for transmission of parasites and diseases between aquaculture farms and wild fish. Twenty female lumpsuckers tagged with acoustic transmitters were released during the spawning season in the inner part of Øksfjord, northern Norway and their distribution was recorded by 22 automatic acoustic receivers. The average time until departure from the fjord was 3 days, and within 1 week all fish had left the fjord. Timing of departure from the fjord was unrelated with either tidal current patterns or the time of the day. A high proportion of the fish (75%) were recorded within 200 m of fish farms, but they did not stay for extended periods at these farms. Our results suggest that mature female lumpsucker exhibit a movement pattern characterized by rapid fjord-scale migrations during the spawning season, and that they are not attracted to salmon farms in the same way as a range of other fish species.     

Spawning strategies in cypriniform fishes in a lowland river invaded by non-indigenous European barbel Barbus barbus

Spawning strategies of lowland river fishes include single spawning, where reproduction generally occurs in early spring to provide 0+ fish with an extended growth season through the summer, but with a high risk of stochastic mortality events occurring, such as early summer floods. This risk can be reduced by multiple or protracted spawning strategies, where 0+ fish are produced over an extended period, often into mid-summer, but with the trade-off being a shorter growth season. The spawning strategies of cypriniform fish were explored in the River Teme, a spate river in Western England, which has non-indigenous European barbel Barbus barbus present. Sampling 0+ fish in spring and summer and across three spawning periods, B. barbus, chub Squalius cephalus and minnow Phoxinus phoxinus always revealed multiple spawning events, with 0+ fish of < 20 mm present in samples collected from June to August. Fish below 20 mm in August remained relatively small by the end of their growth season (October). For dace Leuciscus leuciscus, only single spawning events were evident, but with 0+ dace always being relatively large. Therefore, multiple spawning appears to be a common strategy that provides resilience in 0+ fish against stochastic mortality events in lowland rivers.

     

The effects of thermal effluent exposure on the gametogenesis of female fish

High temperature in Swedish and Lithuanian thermal effluent areas influenced gametogenesis of female perch Perca fluviatilis , roach Rutilus rutilus and pike Esox lucius negatively, indicating reduced reproductive capacity. Oocyte atresia started during vitellogenesis in autumn, and was often followed by asynchronous egg cell development. Among other anomalies, multi-nucleus oocytes and hermaphroditism were observed. No significant impact was seen in silver bream Blicca bjoerkna . Ruffe Gymnocephalus cernuus reacted by a tendency to produce an additional mature oocyte generation during the spawning period. Ovaries in roach from coastal areas were often infected by a microsporidian parasite Pleistophora mirandellae , causing severe damage to the gonad. Parasites were also detected in pike, but neither in perch nor in lake populations of roach. Fish living in open coastal environments did not avoid impact by moving out of the heated areas. There seems to be a conflict in some temperate fish between temperature preference behaviour and safeguarding normal reproduction.     

Fish recruitment in a canal with intensive navigation: implications for ecosystem management

The young-of-the-year (YOY) fish community in Oder-Havel-Kanal, a navigable canal in the German lowlands, assessed from May to October 1999, was dominated by tolerant species especially roach Rutilus rutilus and perch Perca fluviatilis . Roach dominance was high in May and June and low during the rest of the sampling period. The dominance pattern of perch was inversely related to that of roach. Significantly higher densities of significantly smaller YOY fishes were found in bays compared with the straight reaches of the main channel which was the result of an aggregation of 0+ year roach in bays in May and June. Parallel to low structural variability (spawning and nursery habitats), the intensive ship traffic may have been a major force structuring the fish communities in the canals. Measured ship-induced flow velocity in straight reaches was about four times higher than in bays of the canal. Maximum flow velocities caused by barge tows were also four times higher than those induced by pleasure boats. The study demonstrated the relatively low fish reproductive potential of a navigable, artificially embanked lowland canal. To improve fish reproduction, modification of canal banks is highly advisable to preserve existing bays and tributaries and even to create additional ones.     

Movement and pattern of activity of the roach in the River Spree, Germany

Water body and bank structure use of adult roach Rutilus rutilus were examined to increase the knowledge of the most abundant species in the River Spree, Germany. Six tracking series were conducted between 1994 and 1995 to analyse the seasonal and diel movements of the fish. In each series, four to 12 roach were tagged externally and located every 2 h for up to 14 days using radiotelemetry. Roach were highly active, moving up to 10 km downstream to Lake Dämeritzsee, and up to 6 km upstream from their release site. The fish, which mostly swam greater distances upstream during the day and downstream at night, were most active during the spawning season. Their habitat range varied greatly. Close-range habitat, based on 50% of all radiolocations, varied between 5 and 1350 m (mean, ̄=296 m). Wide-range habitat, based on 90% of all radiolocations, varied between 75 and 3820 m (̄=1006 m). The fish preferred different sections of water at different times of year, casting doubt on the relevance of the term home range. Generally, roach stayed close to the bank structures of the main channel during the day and moved to the stagnant waters at night. Consequently, they were most active at dawn and dusk.     

Seasonal and interannual variation of ichthyoplankton off Mauritania

Changes of the quantitative and qualitative composition of ichthyoplankton off Mauritania (21–16° N) in different seasons of 1997–2008 are analyzed. In this area, pelagic eggs and larvae of over 120 fish species belonging to 71 families are recorded. In warm periods, the fish of the tropical fauna intensively spawn off Mauritania; round sardinella Sardinella aurita, West-African horse mackerel Trachurus trecae, and jack mackerel Caranx rhonchus are dominant. In cold periods, active spawning of fish belonging to the tropical fauna is recorded, the most abundant are European pilchard Sardina pilchardus, European horse mackerel Trachurus trachurus, and Atlantic mackerel Scomber japonicus. The spawning biomass of principal commercial fish species is calculated on the basis of the quantity of eggs laid by females. Environmental factors control fluctuations of abundance and distribution of ichthyoplankton in the considered region.