瓦氏黄颡鱼的繁殖生物学研究

研究了长江中游嘉鱼至新滩口江段瓦氏黄颡鱼的繁殖生物学。性腺发育可分为6个时期。4-7月性成熟系数较高,为繁殖季节。雌、雄鱼的肥满度和脂肪系数在繁殖前和繁殖后各出现1个峰值,繁殖期出现最小值。绝对繁殖力为1088-19765(粒),平均7728±4093(粒);相对繁殖力为23-88(粒),平均55±16(粒)。绝对繁殖力与体长、体重和年龄呈显著的正相关,其中体重与绝对繁殖力的关系最密切。群体性比接近1:1。属一次性产卵类型。两性最小性成熟年龄均为2龄。为补充群体占优势的繁殖群体。     

Seasonal maturity development of Baltic cod in different spawning areas: importance of the Arkona Sea for the summer spawning stock

We investigated the seasonal maturity development of cod in four areas of the Baltic Sea. Two different spawning peaks were identified and found to be consistent over the period 1992–2005. In the Kiel Bight and Mecklenburg Bight (ICES SD 22) a spawning peak was observed from March to April (spring spawning). In the areas of the Arkona Sea (ICES SD 24) and Bornholm Sea (ICES SD 25) the spawning peak occurred during summer. In the Bornholm Sea, the main spawning activities began in June and ended in September, with a spawning peak in June–August (summer spawning). In the Arkona Sea, which is a transition area between the Mecklenburg Bight and the central Baltic Sea, spawning began in March and lasted until July, with a spawning peak in June–July (summer spawning). Seasonal maturity development and proportions of spawning cod in June in the Arkona Sea were similar to that of the Bornholm Sea. In addition, the proportion of spawning cod in the Arkona Sea was positively correlated with the size of the spawning stock in the Bornholm Sea. Our results provide evidence of a spatial expansion of spawning activities of the summer spawning stock from the eastern Baltic Sea into the Arkona Sea. Therefore, the Arkona Sea should be considered as one of the spawning habitats of the summer spawning stock of Baltic cod.     

Some issues related to reproduction of Pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> in waters of the eastern coast of the northern Kuril Islands and the southern extremity of Kamchatka

The analysis of data collected in December 1996 and 1998 on the reproduction of cod Gadus macrocephalus in Pacific waters of the northern Kuril Islands and the southern part of Kamchatka was performed. It was shown that the individual absolute fecundity of the cod varies within 0.197–9.729 million eggs and the relative fecundity, in the range of 24-1386 eggs. The fecundity of 1000 mature females comprises 2179–2449 million eggs. The low individual fecundity of fish is related to pseudobranchial tumor growth. The main role in cod reproduction is played by females of two-three size groups characterized by the highest numbers of mature females. It is suggested that different fecundity within the range of Pacific cod is related to environmental conditions, in particular, water temperature in the spawning grounds during spawning rather than to the habitation latitude.     

First evidence of spawning of eastern Baltic cod (Gadus morhua callarias) in the Belt Sea,the main spawning area of western Baltic cod (Gadus morhua L.)

Two cod stocks (western Baltic cod, WBC, and eastern Baltic cod, EBC) are managed in the Baltic Sea which is characterized by different main spawning areas and different main spawning periods. In this study we analyse the spatial and temporal occurrence of spawning individuals of both cod stocks in the main spawning grounds of the Baltic Sea based on eight microsatellite loci. Our results suggest that EBC (Gadus morhua callarias) has formed currently temporally stable, substantially homogeneous population not only in the Bornholm Sea (ICES SD: 25) but also in the Arkona Sea (ICES SD: 24). The presented analyses proved that EBC (G. m. callarias) can temporarily also spawn in the Belt Sea.     

金沙江中下游圆口铜鱼的繁殖生物学

根据2013—2014在皎平渡圆口铜鱼产卵场的定点亲鱼收集(n=206)和2006—2014年在金沙江中下游金安桥至巧家干流江段的流动亲鱼采集(n=70), 对圆口铜鱼的繁殖生物学进行了初步研究。定点亲鱼收集的结果显示: 圆口铜鱼雌性最小性成熟个体全长330 mm, 体质量441.0 g, 年龄4龄; 雄性最小性成熟个体全长352 mm, 体质量396.6 g, 年龄3龄; 50%个体达到性成熟的年龄和全长分别为雌性4.32龄 406 mm, 雄性4.44龄 412 mm; 繁殖群体雌雄性比为1.37﹕1, 繁殖群体中雌性年龄为4—7龄, 雄性年龄为3—7龄; 雌雄个体的性成熟系数平均值均以6龄个体最高, 分别为10.55%和3.45%; 平均卵径为0.16 cm, 卵径分布呈双峰型。定点和流动亲鱼收集的雌性性成熟个体的结果表明: 圆口铜鱼绝对繁殖力变动范围为4055—137900粒/尾, 平均值为22817粒/尾; 相对繁殖力变动范围为5—73粒/g, 平均值为20粒/g, 75.68%个体的绝对繁殖力在10000—30000粒/尾之间, 70.27%个体的相对繁殖力在15—20粒/g之间; 绝对繁殖力和相对繁殖力均随着体长和体质量的增加而增加, 其中全长、体质量与绝对繁殖力呈指数分布函数正相关, 而与相对繁殖力呈二次项函数正相关。研究结果可为长江流域圆口铜鱼资源的保护提供重要的基础数据支撑。     

Intra-annual variation in the batch fecundity of sardine off Portugal

Atresia in the ovaries of sardine Sardina pilchardus did not show clear seasonal patterns. There was high prevalance ( c. 60%) and low intensity ( c. 1% of gonadal area occupied by oocytes) in all months of the spawning season studied. The batch size to ovary-free mass relationship was significantly different in the mid-spawning season, with higher relative fecundity and gonadosomatic index (I_G) in January than in November and March. There was no additional effect on batch fecundity due to age or condition factor. Data from monthly market samples during 1998–1999 revealed a continuous decline of the condition factor throughout the spawning season. The market samples also revealed that the duration of the spawning season is not equal for all fish. In any month, pre-spawning fish tended to have significantly higher I_G than spawners, indicating that delayed initiation of spawning can lead to larger relative fecundity. The increase in sardine relative fecundity during the first half of the spawning season is probably due to the continuous influx of new spawners and possibly to body mass loss that is initially not translated into gonad mass loss. After January when all visible fat reserves within the body cavity have disappeared, the influx of new spawners practically ceases.     

Spawning Dynamics and Size Related Trends in Reproductive Parameters of Southern Bluefin Tuna,Thunnus maccoyii

Knowledge of spawning behaviour and fecundity of fish is important for estimating the reproductive potential of a stock and for constructing appropriate statistical models for assessing sustainable catch levels. Estimates of length-based reproductive parameters are particularly important for determining potential annual fecundity as a function of fish size, but they are often difficult to estimate reliably. Here we provide new information on the reproductive dynamics of southern bluefin tuna (SBT) Thunnus maccoyii through the analysis of fish size and ovary histology collected on the spawning ground in 1993–1995 and 1999–2002. These are used to refine previous parameter estimates of spawning dynamics and investigate size related trends in these parameters. Our results suggest that the small SBT tend to arrive on the spawning ground slightly later and depart earlier in the spawning season relative to large fish. All females were mature and the majority were classed as spawning capable (actively spawning or non-spawning) with a very small proportion classed as regressing. The fraction of females spawning per day decreased with fish size, but once females start a spawning episode, they spawned daily irrespective of size. Mean batch fecundity was estimated directly at 6.5 million oocytes. Analysis of ovary histology and ovary weight data indicated that relative batch fecundity, and the duration of spawning and non-spawning episodes, increased with fish size. These reproductive parameter estimates could be used with estimates of residency time on the spawning ground as a function of fish size (if known) and demographic data for the spawning population to provide a time series of relative annual fecundity for SBT.     

Spawning frequency, fecundity, egg weight and spawning type of silver pomfret, Pampus argenteus (Euphrasen) (Stromateidae), in Kuwait waters

Silver pomfret, Pampus argenteus, were collected by fishing with drift gillnets on one spawning ground in Kuwait waters during 1998–2000. Fish size frequency, sex ratio, maturation cycle, spawning frequency, fecundity and egg weight were assessed. The length–weight relationship differed between sexes whereby females were significantly bigger than males. Spawning started in mid‐May and continued until early October. During this time the water temperature ranged from 26.0 to 32.8°C, salinity was ? 39.0‰ and water depth ranged between 5 and 12 m. Large females spawned earlier than young spawners and the overall percentage of males during the spawning period was 70.3%. Spawning occurred after 13.00 h, with peak spawning between 15.00 and 18.00 hours during outgoing tide. Mean daily spawning frequency amounted to 63.2%. Spawning activity was found to be associated with the lunar cycle and spawnings were concentrated during the first and third quarters of the moon period, indicating a semilunar reproduction cycle. It was concluded that a female would spawn at least six times during the season. No change was observed in relative fecundity during the peak spawning season (June–August). Average relative batch fecundity was 176.3 eggs g^?1 somatic weight (SW), corresponding to a relative total fecundity of 1058 eggs g^?1 SW, which is 1.5 times higher than estimates obtained from counting the standing stock of oocytes. Bigger fish produced heavier eggs and the egg weight decreased as the spawning season progressed. Based on gonadal cycles, oocyte size frequency distribution and total fecundity, we concluded that silver pomfret is a multiple batch spawner with indeterminate fecundity.     

Differences in reproductive strategies between obscure puffer Takifugu obscurus and ocellated puffer Takifugu ocellatus during their spawning migration

Reproductive strategies were compared between obscure puffer Takifugu obscurus and ocellated puffer Takifugu ocellatus captured in waters near Yangzhong Island in the lower reaches of the Yangtze River during the spawning migration season from February to June in two consecutive years (1995 and 1996). Results showed that obscure puffer and ocellated puffer have adopted different reproductive strategies, including different spawning times, different size at maturity, and different number and size of oocytes, resulting in two different larval sizes. In detail, the timing of the spawning migration and status of gonad development of obscure puffer was about 1 month earlier than that of ocellated puffer; the obscure puffer was obviously longer and heavier than ocellated puffer in both mature male and female fish; mean GSI of obscure puffer females (15.8%) was significantly higher than that of ocellated puffer females (14.6%); the average diameter of ocellated puffer eggs (1.49 ± 0.12 mm) was significantly larger than that of the obscure puffer (1.22 ± 0.08 mm); and obscure puffer females (320.8 oocytes mg^?1 somatic wet weight) had significantly higher relative fecundity than ocellated puffer females (125.2 oocytes mg^?1 somatic wet weight). These differences in reproductive strategies between two closely related species of the Takifugu genus indicate that both obscure puffer and ocellated puffer fit the r/K dichotomy. Obscure puffer shows K‐selected characters with maturity at relatively large size and r‐selected characters with relatively many and small offspring, whereas ocellated puffer shows r‐selected characters with maturity at a relatively small size and K‐selected characters with relatively few and large offspring.     

Batch fecundity and spawning frequency of invasive Hemiculter leucisculus (Basilewsky, 1855) in Erhai Lake,China

Hemiculter leucisculus are multiple spawners with indeterminate fecundity, although previous fecundity estimates have assumed a determinate spawning pattern. Batch fecundity and spawning frequency of H. leucisculus were studied in Erhai Lake, China, in which the fish, as an exotic species, has become a successful colonizer. Spawning frequency was 16.05 %, as determined from the percent of females with postovulatory follicles 12 to 36 h old during the peak reproductive period (from May 27 to August 8). The average interval between spawning was 6.2 days and there were more than 16 total spawning batches during the peak reproductive period. The average batch fecundity (mean ± SD) was 11,934?±?5,921 hydrated oocytes in 40 females (standard length or SL: 9.1–14.4 cm), while relative batch fecundity was 560?±?137 eggs g^?1 wet weight. The total potential annual fecundity was approximately 190,944 oocytes over the whole spawning season and was much higher than the estimated standing stock (31,585 oocytes) of yolked oocytes (36 females, SL: 9.5–16.2 cm) at the beginning of the spawning season in April 2010. This high annual fecundity is likely to have contributed to successful invasion of Erhai Lake by H. leucisculus.     

武湖日本沼虾繁殖生物学研究

武湖日本沼虾产卵场位于全湖沿岸带．越冬虾主要繁殖期为春夏季(4月中旬～7月中旬,水温20．5～31℃)。当年虾繁殖期为秋季(7月中旬～9月中旬,水温31～23℃),7月中下旬为新老世代交替期．非繁殖季节雄虾多于雌虾,繁殖季节雌虾多于雄虾．越冬虾绝对繁殖力明显大于当年虾．绝对繁殖力与体长呈幂函数关系,与体重呈直线相关．相对繁殖力RW为常数,其95％置信区间为1067．76±16．94eggs·g^-1。     

Aspects of the fecundity of the feral catfish,Clarias macrocephalus (Gunther), population obtained from the rice fields used for rice-fish farming,in Malaysia

The catfish, Clarias macrocephalus, harvested from the irrigated rice fields of Malaysia, exhibited spawning activities that are influenced by water level management. The multiple spawning potential of the fish is negated by declining water level and the fish spawned only once per growing season. Although oocyte development started in conjunction with water level increase, subsequent oocyte development did not take place due to low water level. Absolute and relative fecundity also decreased with declining water level, however, mean relative fecundity is relatively constant (17.6–53.7 oocytes g^–1 body weight) and not related to body size. Absolute fecundity ranged between 785 to 14066 oocytes female^–1, whereas relative fecundity is between 7.1 to 83.5 oocytes g^–1 body weight, respectively.     

足木足河黄石爬■个体生殖力研究

2012年7月和2013年6月于大渡河流域足木足河日部-足木足段采集黄石爬鮡Euchiloglanis kishinouyei,研究性腺Ⅳ期雌性个体生殖力及其与多项形态学指标的关系。结果显示:黄石爬鮡为一次性产卵鱼类,产卵群体以5~8龄鱼为主;个体绝对生殖力247.77粒±81.37粒,体长相对生殖力17.75粒/cm±5.34粒/cm,体质量相对生殖力6.59粒/g±1.99粒/g,繁殖策略属于典型的K对策者;绝对生殖力、体长相对生殖力和体质量相对生殖力均与成熟系数相关性显著,绝对生殖力与体长、体质量相对生殖力与净体质量和肥满度相关性较显著,可根据成熟系数、体长和体质量预测其种群繁殖能力,进而了解其种群的动态变化。     

Spawning frequency and batch fecundity of horse mackerel, Trachurus trachurus (L.), in the Saronikos Gulf (Greece)

Horse mackerel, Trachurus trachurus (L.), is a multiple spawning fish with most probably an indeterminate fecundity. Histological sections of gonads were used to identify the hydrated oocytes, the migratory-nucleus stage oocytes, and the new and old post-ovulatory follicles. Spawning frequency determination, based on the mean percentage estimation of the females that occurred in different spawning states such as migratory-nucleus stage oocytes and post-ovulatory follicles during two successive reproductive periods, was found to average once every 5.8 and 4.8 days, respectively. High spawning frequency was observed at the peak of spawning. Relative batch fecundity of 205 oocytes/g fish weight was estimated by the hydrated and migratory-nucleus method. Since potential annual spawnings were found to be equal to 16, potential annual relative fecundity could be 3280 oocytes/g fish weight.     

Comparative analysis of reproductive traits in black-chinned tilapia females from various coastal marine, estuarine and freshwater ecosystems

The black-chinned tilapia Sarotherodon melanotheron is a marine teleost characterised by an extreme euryhalinity. However, beyond a certain threshold at very high salinity, the species exhibits impaired growth and precocious reproduction. In this study, the relationships between reproductive parameters, environmental salinity and condition factor were investigated in wild populations of this species that were sampled in two consecutive years (2003 and 2004) from three locations in Senegal with different salinities: Guiers lake (freshwater, 0 psu), Hann bay (seawater, 37 psu) and Saloum estuary (hypersaline water, 66-127 psu). The highest absolute fecundity and spawning weight were recorded in seawater by comparison to either freshwater or hypersaline water whereas the poorest condition factors were observed in the most saline sampling site. These results reflect higher resource allocation to the reproduction due to the lowest costs of adaptation to salinity in seawater (the natural environment of this species) rather than differences in food resources at sites and/or efficiency at foraging and prey availability. Fecundities, oocyte size as well as spawning weight were consistent from year to year. However, the relative fecundity in the Saloum estuary varied significantly between the dry and rainy raisons with higher values in the wet season, which seems to reflect seasonal variations in environmental salinity. Such a reproductive tactic of producing large amounts of eggs in the rainy season when the salinity in the estuary was lower, would give the fry a better chance at survival and therefore assures a high larval recruitment. An inverse correlation was found between relative fecundity and oocyte size at the two extreme salinity locations, indicating that S. melanotheron has different reproductive strategies in these ecosystems. The adaptive significance of these two reproductive modes is discussed in regard to the heavy osmotic constraint imposed by extreme salinities and high inter-specific competition.     

Reproductive ecology of Brazilian freshwater fishes

We used metadata on nine reproductive traits of 67 species of Brazilian iteroparous, oviparous, teleost freshwater fishes to test phenotypes associations to discriminate species that only spawn in large rivers (lotic fishes) from those capable to spawn in lentic habitats (lentic fishes). We tested the hypothesis that lotic fishes present spawning migration, shorter spawning season, single spawning, no parental care, free eggs, higher relative fecundity, faster embryogenesis, and larger size, while lentic fishes present no spawning migration, longer spawning season, multiple spawning, parental care, adhesive eggs, lower relative fecundity, slower embryogenesis, and smaller size. Our analyses supported the hypothesis but not all phenotypic associations satisfied it, specifically with regard to lentic fishes or to pairs of phenotypes typical of lentic fishes. We also concluded that spawning in large rivers is a better predictor of bionomic characters than spawning in lentic habitats, and lotic fishes are specialists compared to lentic fishes.     

Reproductive biology of Hemiramphus brasiliensis and H. balao (hemiramphidae): maturation,spawning frequency,and fecundity

Analyses of life-history data show that both the size-specific batch fecundities and the age-specific spawning frequencies differ for two halfbeak species, Hemiramphus brasiliensis, the ballyhoo, and H. balao, the balao. Halfbeak ages were determined from sectioned otoliths; histological data was used to describe oocyte development and estimate spawning frequency; and batch fecundity was measured from counts of whole oocytes in final maturation. Hemiramphus brasiliensis lived longer (4 versus 2 years) and had a higher survival rate (14.9% versus 7.5% annually) than H. balao did. Of the two species the larger and longer-lived congener, H. brasiliensis, reached sexual maturity at a larger size (fork length 198 versus 160 mm). The spawning period of age-0 females was strongly related to season, whereas spawning by older females occurred throughout the year. Reproduction by both species peaked during late spring or early summer, and all mature females were spawning daily during April (H. brasiliensis) or June (H. balao). This is the first demonstration of iteroparity for the family Hemiramphidae. H. brasiliensis had a lower batch fecundity (about 1164 versus 3743 hydrated oocytes for a 100-g female) than H. balao did. Such low batch fecundities are typical of the order Beloniformes, but quite different from those of other fishes that live in association with coral reef habitats. H. balao's higher batch fecundity is consistent with the life-history theory that predicts higher numbers of eggs for shorter-lived species; this is possible because H. balao produces smaller hydrated oocytes than H. brasiliensis (modal diameter about 1.6 versus 2.4 mm). The high spawning frequency of Hemiramphus species compensates for their low batch fecundity. The annual fecundity of both species is similar to that of other reef fish species, after adjusting for body size and spawning frequency. The lifetime fecundity of H. balao was very similar to that of H. brasiliensis, after accounting for the differences in survival for each species. This suggests a fine tuning of different reproductive traits over the entire life cycle that results in roughly equivalent lifetime fecundity for both species.     

Reproductive ecology of Japanese anchovy off the Pacific coast of eastern Honshu, Japan

Spawning frequency of offshore migrant populations of Japanese anchovy Engraulis japonicus ranged from 0·34 to 0·90, and was higher than that of inshore Japanese anchovy. In addition, spawning frequency of offshore populations varied in response to the sex ratio. They spawned at water temperatures of 5.0, 8.6 and 12.6° C, indicating that the minimum critical water temperature of offshore Japanese anchovy was considerably lower than that of inshore populations. A significant positive relationship was observed between water temperature and relative batch fecundity of offshore Japanese anchovy. Furthermore, water temperature was negatively related to egg size, suggesting a trade-o. between relative batch fecundity and egg size for offshore fish. At the same water temperature, relative batch fecundity of offshore populations was higher than that of inshore ones. The comparison of spawning frequency and relative batch fecundity suggests that offshore Japanese anchovy represent a reproductive ecology by which they spawn more eggs than inshore Japanese anchovy within a certain time period.     

Spatial and environmental effects on Coho Salmon life history trait variation

Adult size, egg size, fecundity, and mass of gonads are affected by trade‐offs between reproductive investment and environmental conditions shaping the evolution of life history traits among populations for widely distributed species. Coho salmon Oncorhynchus kisutch have a large geographic distribution, and different environmental conditions are experienced by populations throughout their range. We examined the effect of environmental variables on female size, egg size, fecundity, and reproductive investment of populations of Coho Salmon from across British Columbia using an information theoretic approach. Female size increased with latitude and decreased with migration distance from the ocean to spawning locations. Egg size was lowest for intermediate intragravel temperature during incubation, decreased with migration distance, but increased in rivers below lakes. Fecundity increased with latitude, warmer temperature during the spawning period, and river size, but decreased in rivers below lakes compared with rivers with tributary sources. Relative gonad size increased with latitude and decreased with migration distance. Latitude of spawning grounds, migratory distance, and temperatures experienced by a population, but also hydrologic features—river size and headwater source—are influential in shaping patterns of reproductive investment, particularly egg size. Although, relative gonad size varied with latitude and migration distance, how gonadal mass was partitioned gives insight into the trade‐off between egg size and fecundity. The lack of an effect of latitude on egg size suggests that local optima for egg size related to intragravel temperature may drive the variation in fecundity observed among years.     

Evidence for metapopulation structuring in cod from the west of Scotland and North Sea

The scale of population structuring in cod Gadus morhua from the west of Scotland (ICES stock area VIa) and northern North Sea was investigated using a combination of non-genetic methods. Site fidelity of spawning aggregations was examined using historic tag-recapture experiments and individual geolocation estimates from data storage tagged fish. The extent of movements from spawning areas indicated by these two tagging approaches was broadly similar. Between 67 and 97% of adult cod remained within 100 km of spawning areas throughout the year, suggesting resident spawning groups. A small proportion of cod, however, did appear to stray between spawning areas. A comparison of the elemental signature of the otoliths of 0 year-group and the 0 year-group component from the same year-class at age 2 years indicated that most adults originate from local nursery areas. Moreover, there did not appear to be detectable exchange between spawning areas >200 km apart, such as the Clyde and Minch or Shetland and the Inner Hebrides. As such, population processes may operate at a smaller spatial scale than the stock level, with spawning aggregations functioning as local populations within a metapopulation. The relevance of this scale of dynamics is discussed in relation to recently imposed closed areas in the region.