Reproduction of Snowy Sculpin Myoxocephalus brandti(Cottidae) in Peter the Great Bay, Sea of Japan

Spawning of snowy sculpin in Peter the Great Bay begins in November and takes place at a depth of about 4–7 m. Males of this sculpin species guard their laid eggs. Larvae hatch in April. Final fecundity is attained at ovary maturity stages IV–V.     

Spawning of the sea ravenHemitripterus villosus in Peter the Great Bay, Sea of Japan

The spawning habits of the sea ravenHemitripterus villosus were investigated by scuba diving at shallow rocky bottom sites around Bolshoi Pelis Island (Peter the Great Bay, Sea of Japan). Spawning occurs in September, when the surface water temperature drops. The optimum spawning temperature is 17–18°C. The fish density in nest sites reaches 120/300 m². The mean individual fecundity is about 10000 eggs. Over 35% of the egg masses ofH. villosus are eaten by echinoderms, primarilyPatiria pectinifera andStrongylocentrotus nudus. Since fecundity is relatively low and parents do not take care of the egg masses, predation can strongly affect the abundance of this species.     

Growth,fecundity, and egg size of least brook lamprey,Lampetra aepyptera

Synopsis Eight geographically-diverse (33°11N to 39°14N) populations of least brook lamprey varied significantly in density of larvae and mean length of metamorphosing and adult lampreys (101–152 mm). Absolute fecundity (503–5900 eggs) did not change significantly with stage of post-larval development, suggesting little post-metamorphic atresia; egg dry weight increased to stage 6, the penultimate stage of metamorphosis. Absolute fecundity increased with the cubic power of total length. Relative fecundity (250–1124 eggs per gram total body weight) decreased significantly with increasing length within two streams. Relative fecundity, adjusted to a common length, increased with mean length of the population. Conversely, mean egg dry weight (0.09–0.24 mg, stages 6–8) increased with maternal length within three streams, and decreased with length among streams. In populations where spawning occurs at a small body size, females produce comparatively fewer but larger eggs. Large eggs may be required to counter the effects of an unproductive environment and the accompanying reduction in relative fecundity is compensatory. No relationship was evident between latitude, annual thermal units, or density and relative fecundity or egg size. Mean length of a population was also unrelated to these environmental factors.     

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.     

Maturation and Reproductive Biology of Female Wild Carp, Cyprinus carpio, in Victoria, Australia

The reproduction of carp Cyprinus carpio L. (Family: Cyprinidae), from Victorian waters in Australia, is studied with detailed analysis of gonad maturation, spawning season, fecundity and oocyte diameter. Results show that carp has a high annual fecundity (AF) (0.12–1.54 million oocytes per fish), which is positively correlated with caudal fork-length (L, mm) and total weight (W, kg) but not age. The relationships between length or weight and AF were statistically significant and best described with the simple linear or quadratic regressions. Mean relative fecundity was 0.163 million eggs kg^–1 whole weight. Egg size was estimated from oocyte diameter in carp from eight stocks. Egg size was proportional to maternal size but not age. Seasonal trends in gonadosomatic indices, together with the changes in the macroscopic and microscopic condition of ovaries, demonstrated that spawning generally peaks during spring–early summer, but also occurs through until autumn and can even start in late winter at some sites. In Victoria, this species is a multiple spawner with asynchronous oocyte development and a protracted spawning season. Stocks generally contain both females that spawn once, and females that spawn repeatedly, within a spawning season. Implications for management for the control of feral carp stocks are discussed.     

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.     

Enzyme-linked immunosorbent assay (ELISA) used in quantification of reproductive output in the pacific oyster,Crassostrea gigas,in Korea

Polyclonal antibody developed from egg proteins of the Pacific oysters, Crassostrea gigas, was used in quantification of the eggs. Quantity of the egg protein was measured using ELISA and a weight-normalized gonadosomatic index (GSI) was then established. Histology indicated that the oysters collected from Goseong Bay, Korea, in 2000 initiated gametogenesis as early as late February and spawned mostly in late June to early July when water temperature reached 23–25 °C. A second spawning peak was also observed in late August and the spawning activity continued to late October. Oyster egg proteins could be detected by ELISA in all months except March and November; a few oysters collected during December and January contained a measurable amount of eggs. The highest monthly mean GSI, 0.423, was observed in mid-June when the oysters were ready to spawn. The maximum GSI recorded in this study was 0.667. A positive correlation was found between oyster size and fecundity; the number of eggs increased as oyster biomass increased (r²=0.7497). Our data suggest that oysters in Goseong Bay produce 3–196 million eggs during the spawning season. The immunological method developed in this study was sensitive enough to measure a small quantity of eggs and considered to be method of choice for studying bivalve reproduction.     

The reproductive biology of <Emphasis Type="Italic">Nassarius festivus</Emphasis> (Powys, 1835) (Gastropoda: Nassariidae) in relation to seasonal changes in temperature and salinity in subtropical Hong Kong

The reproduction of Nassarius festivus (Gastropoda: Nassariidae) has been studied on three contrasting beaches in Hong Kong. There was no significant difference in shell heights between females and males of N. festivus at three study sites and the sex ratio was always female biased. The highest female sex ratio was recorded from Starfish Bay, followed by Tai Tam Bay and then Tai Mong Tsai. The sexual cycle of N. festivus is completed in 1 year in Hong Kong. It is a winter spawner with a reproductive period ranging from September to May. The gonads progressively mature in autumn with maturity being achieved in winter. Spring and summer are times of gonadal decline and gametogenesis initiation, respectively. The ranges in water temperature and salinity at which mature individuals occur were 13.7–28.0°C and 19.3–29.0‰, respectively. N. festivus produces between 16 and 46 eggs·capsule⁻¹. Over its short life span of 1.21 years, therefore, N. festivus attempts to maximize reproductive output. The eggs hatch as veligers which remain in the plankton for between 33 and 41 days. In terms of its reproductive biology, it is concluded that N. festivus behaves as a typical sub-tropical species with a mix of tropical and temperate characteristics seen in other nassariids from these latitudes.     

Fecundity of the Grass Shrimp,Pandalus kessleri (Decapoda: Pandalidae), near the Southern Kuril Islands

We determined the absolute (AIF) and relative (RIF) individual fecundity in a commercially important object, the grass shrimp, Pandalus kessleri (Decapoda: Pandalidae) near the Southern Kuril Islands. In the shrimps from Izmeny Bay (Kunashir Island) and the coastal area of the Southern Kuril Islands, the AIF equaled 192–918 (averaging 505) and 162–784 (459), respectively. In larger females, the AIF increases, reaches the maximum value, and then decreases again in the largest females. In June the AIF is smaller than in September, and in larger prawns, this difference is more pronounced. The mean large (D) and small (d) diameters of eggs equaled 1972 (1665–2400) and 1538 (1347–1900) m, respectively; the D/d ratio equaled 1.28. The mean wet weight of an egg (w) was 3.43 mg (1.986–4.9) mg. From September 1 to November 30 D and d increased from 1894 to 2088 m and from 1490 to 1567 m, respectively. The factors affecting the fecundity of grass shrimp in Izmeny Bay are discussed.     

Prevalence and infection intensity of the ovarian parasite Marteilioides chungmuensis during an annual reproductive cycle of the oyster Crassostrea gigas

The occurrence of Marteilioides chungmuensis, a protozoan paramyxean parasite in the reproductive system of the Pacific oyster Crassostrea gigas, was observed at Gosung Bay, Korea. Seasonal variation in gonad development was investigated in a suspended cultured oyster population. Gametogenesis began in February and first-spawning was observed between mid and late June when surface water temperature reached 22 to 25 degrees C. Spawning activity extended from mid June to late September, with 2 marked spawning peaks in June and August. Histological examination indicated that gonad development paralleled seasonal fluctuations in water temperature. Spawning in late June was partly associated with a sudden drop in salinity due to large freshwater inputs to the Bay with the summer monsoon. M. chungmuensis occurred in developing and fully mature eggs of spawning oysters in late June to January, but were not observed from February to May. Monthly mean infection intensity was high in late June when most oysters had their first spawning period. The infection level was also relatively high in late August and November, when oysters were spawning or had completed spawning. Several oysters collected in November (11.4%) and December (16.3%) carried a large quantity of ripe but M. chungmuensis-infected eggs, suggesting that infection also causes spawning failure by delaying spawning and destroying ripe oocytes.     

Batch fecundity of Atlantic mackerel, Scomber scombrus L.

The total annual fecundity of mackerel, Scomber scombrus L., during a spawning season is produced by release of discrete batches of eggs. Total fecundity is then the product of the number of batches times the batch fecundity ( F _bw). An extensive trawl survey of the Western mackerel stock in the NE Atlantic was undertaken in the 1989 spawning season. Batch fecundity was estimated for 298 fish by counting hydrated eggs in ovaries just prior to ovulation. F _bw, expressed as eggs g⁻¹ body weight, varied with latitude: south of 51°N, F _bw= 55.49, s.e. = 2.04, n = 227; between 51°N and 55°N, F _bw= 45.72, s.e. = 3.41, n = 52 and north of 55° N, F _bw= 41.33, s.e. = 5.52, n = 19. It is suggested that as spawning fish migrate northwards the batch size decreases with progress of the spawning season.     

三峡水库秀丽白虾生长与繁殖生物学特征研究

2012 年11 月至2013 年10 月逐月对三峡水库木洞江段秀丽白虾的生长和繁殖生物学特征进行了研究。结果显示秀丽白虾是一年生的虾类, 寿命为1214 个月。雌性个体的平均体长(37.727.92) mm 显著大于雄性(37.086.59) mm, 具有明显的雌雄异形现象。秀丽白虾的渐近体长(L)为59.33 mm, 生长系数(K)是1.6/年, 生长方程为:Lt=59.33-e-1.6(t+0.081)。雌虾繁殖季节从4 月上旬持续至9 月下旬, 繁殖高峰期为4 月中旬至6 月中旬, 由越冬虾和当年虾两个世代的繁殖群体组成。抱卵雌虾的体长为27.0753.71 mm, 平均体长(L50)为37.06 mm。雌雄性比月变化为1.112.36, 平均为1.46, 群体中雌性个体数量显著多于雄性(P 0.001)。绝对繁殖力(FA)为31294 粒, 相对繁殖力(FR)为(11522)粒/g。绝对繁殖力与体长呈幂函数关系(FA=0.0031L2.8632, r=0.72, n=106), 而与体重呈直线关系(FA=104.63W+9.9534, r=0.79, n=106)。卵径(D)平均值为(1215102) m。为合理保护和利用三峡水库秀丽白虾种群资源, 建议加强虾类捕捞管理, 繁殖期间(49 月)禁止捕捞虾类或限制捕捞强度。       

Evidence of autumn spawning in Suwannee River Gulf sturgeon,Acipenser oxyrinchus desotoi (Vladykov, 1955)

Evidence of autumn spawning of Gulf sturgeon Acipenser oxyrinchus desotoi in the Suwannee River, Florida, was compiled from multiple investigations between 1986 and 2008. Gulf sturgeon are known from egg collections to spawn in the springtime months following immigration into rivers. Evidence of autumn spawning includes multiple captures of sturgeon in September through early November that were ripe (late‐development ova; motile sperm) or exhibited just‐spawned characteristics, telemetry of fish that made >175 river kilometer upstream excursions to the spawning grounds in September–October, and the capture of a 9.3 cm TL age‐0 Gulf sturgeon on 29 November 2000 (which would have been spawned in late September 2000). Analysis of age‐at‐length data indicates that ca. 20% of the Suwannee River Gulf sturgeon population may be attributable to autumn spawning. However, with the very low sampling effort expended, eggs or early life stages have not yet been captured in the autumn, which would be the conclusive proof of autumn spawning. More sampling, and sampling at previously unknown sites frequented by acoustic telemetry fish, would be required to find eggs.     

Aspects of the reproductive biology of two archer fishes <Emphasis Type="Italic">Toxotes chatareus</Emphasis>, (Hamilton 1822) and <Emphasis Type="Italic">Toxotes jaculatrix</Emphasis> (Pallas 1767)

Various aspects of the reproductive biology of two archer fishes Toxotes chatareus and Toxotes jaculatrix were studied to describe gonad development, spawning season, sex ratio, and fecundity. Spawning season was assessed using monthly changes in gonadosomatic index (GSI) and histological inspection of the gonads. Both species exhibit two modes of oocytes; a mode of small primary growth oocytes and a single mode that increases with size as oocytes sequester vitellogenin and undergo maturation, showing the synchronous oocyte development typical of total spawners. Based on GSI values and advanced stages of oocyte maturity, T. chatareus and T. jaculatrix, females appear to spawn from November to December. The average fecundity of female T. chatareus was 55 000 ± 5538 eggs, and T. jaculatrix was 50 000 ± 3440 eggs; fecundity ranged from 20 000 to 150 000 eggs for both species, with relative fecundities of 600 to 1100 eggs/g body weight, and a mean value of 800 ± 32 for T. chatareus; relative fecundity ranged from 500 to 1100 with a mean value of 700 ± 23 for T. jaculatrix. Sex ratio, defined as the proportion of males to females, was 2.2 and 2.5 in T. chatareus and T. jaculatrix, respectively. The apparent abundance of males in samples could be due to females being positioned lower in the water column and therefore being sampled less frequently. Our results indicate that in both species, spawning occurs between the months of November and December during the monsoon season, which provides the mangrove coastal waters inhabited by these species with an abundance of food resources and additional floodplain nursery habitat for larvae and juveniles.     

Reproductive biology of brown trout, Salmo trutta macrostigma Dumeril 1858, in a tributary of the Ceyhan River which flows into the eastern Mediterranean Sea

The study describes some key elements of the reproductive biology, including spawning season, age at sexual maturity, fecundity and egg diameter of the native brown trout, Salmo trutta macrostigma, in a tributary of the Ceyhan River. A total of 197 brown trout (118 females and 79 males) were captured in 2000–2001 by electric fishing. In observations on monthly changes, the gonadosomatic index (GSI) and the monthly frequency distribution of egg diameter confirmed that spawning lasted from November to January. Some 27.7% of the females and 62.5% of the males attained sexual maturity in their second year. The smallest fork length (FL) of brown trout attaining sexual maturity was 17.4 cm for males and 17.8 cm for females. Mean fecundity in age groups II, III, IV and V were 360, 452, 693 and 1283 eggs per female, respectively. One 9‐year‐old female had a unique 3232 egg count. The mean fecundity of the sampled population was 554 eggs per fish, positively correlated with the FL (mm) (R = 0.8227 ) and body weight (R = 0.8130). The diameter of mature eggs in the spawning season ranged from 3.250 to 5.930 mm, with a 4.146 mm average. Mean egg diameter in age groups II, III, IV and V in the spawning season were 0.813, 3.799, 4.663 and 5.243 mm, respectively. Fecundity, egg weight and diameter were statistically different in all age groups.     

Examination of the meroplankton community in the south-western Ross Sea, Antarctica, using a collapsible plankton net

The meroplankton community in the coastal Antarctic has been poorly studied, in part due to the presence of extensive sea-ice cover during the summer months. In this study, a collapsible plankton net was used to examine the meroplankton community at two sites in the south-western Ross Sea: at Cape Evans on Ross Island, and at Cape Roberts on the Victoria Land coast. Three samples were taken on 5 consecutive days in the early summer at each site (26–30 November and 8–12 December 2001) and 11 operational taxonomic units (OTUs) were quantified from the phyla Annelida, Mollusca, Nemertea, Echinodermata and Sipuncula and the early developmental stages of undetermined phyla. Multivariate analysis showed that there were distinct differences in the meroplankton communities at the two locations, but because there was a 2-week difference in the time of sampling between sites, location and time are confounded variables. On average, a total of 16 larvae/eggs/embryos were collected per tow (3.92 m³) at Cape Evans and 27 larvae/eggs/embryos at Cape Roberts, with a significant difference in total larval numbers and in numbers of 4/6 larval types tested between location and time. This research has shown that a collapsible plankton net can be used for meroplankton work in remote locations in the coastal Antarctic and that a diverse meroplankton community is evident in the south-western Ross Sea in the early summer.     

Reproductive biology of Vinciguerria nimbaria in the equatorial waters of the eastern Atlantic Ocean

Adult Vinciguerria nimbaria in an area of the Atlantic Ocean (0–5°N; 10–20°W), collected from November 1994 to February 1998, exhibited two different patterns in diel behaviour: 'typical' behaviour which consisted of large diel vertical migration and 'atypical', characterized by concentrations of schools that remained in the surface layers during the daytime. The total life span of V. nimbaria was estimated at 6–7 months. Females were mature when they reached 30·6 mm standard length ( L _S), which corresponded to an age of 85 days. Once the females were mature, spawning was continuous in the population as a whole, and V. nimbaria spawned continuously throughout the year. Spawning took place during two restricted times of the day: typical females spawned at dusk and atypical females spawned at dawn. Using the post-ovulatory follicles method, spawning frequency was estimated at 2 days. Batch fecundity was estimated at 1236 oocytes or 1230 oocytes g⁻¹ of total body mass, and egg size was 650 µm whatever the period of the year. The lifetime fecundity of V. nimbaria was estimated at 9000 eggs (109 000 eggs if mortality rate was not taken into account), and the maximum stock egg production of a theoretical cohort occurred at 37 mm L _S. Young adults thus contributed the most to the reproductive output for the survival of the population.     

Reproductive biology of the endangered Oxleyan pygmy perch Nannoperca oxleyana Whitley

The reproductive biology of the Oxleyan pygmy perch Nannoperca oxleyana is described from simultaneous studies of wild populations in north-eastern New South Wales and mature fish held in aquaria. In the wild, 50% of males and females matured at total lengths of 24·0–25·9 and 28·0–29·9 mm, respectively. The species displays sexual dichromatism during the spawning season, with males developing more intense red and brown fin and body colouration, and black pelvic fins. Captive male broodfish displayed territoriality during the breeding season, closely guarding sites within artificial, plant-like substrata in which pairs of fish spawned adhesive eggs. Protracted serial spawning of wild and captive fish occurred from September to April and May at mean water temperatures ≥16·6° C and day length ≥10·7 h. Captive broodfish spawned on an average of 57% of days during the 256 day spawning period. Gonado-somatic indices averaged 0·7% for all ripe males and 4·1–4·2% for all ripe females collected. Mean total and batch fecundities of captive females were 1323 eggs per fish and 7·8 eggs per fish per day, respectively, and relative fecundity was 587 eggs g⁻¹ of body mass. Batch fecundity of wild females was estimated at 7·8 eggs per fish. The adaptive significance of this reproductive strategy in a harsh, variable environment is discussed.     

Reproductive guilds (maturation,spawning frequency and fecundity) in the black pomfret,Parastromateus niger (Carangidae) in the Kuwaiti waters of the Arabian Gulf

Oogenesis, oocyte maturation pattern, spawning rhythm, spawning frequency, batch fecundity and oocyte diameter–frequency distribution of the black pomfret, Parastromateus niger (Bloch, 1795) in Kuwaiti waters were investigated from October 2003 to September 2005, using histological and morphological methods. The process of development is divided into four major phases: (i) primary growth phase; (ii) secondary growth phase; (iii) maturation phase; and (iv) spawning phase, followed by the regressed phase. Development of the yolky oocyte is an asynchronous process resulting, by the time of oocyte maturation, in a clear differentiation between a ready batch of oocytes (ready for spawning) and a reserve pool. Consequently, P. niger is capable of spawning multiple times throughout the reproductive season. Spawning frequency estimates, based on final oocyte maturation (FOM) method indicated that the species spawns once every 2.8 days during an 8‐month spawning season lasting from February to September, with a potential annual number of 22.4 spawns. Batch fecundity (BF) (2132–2001 648, mean 406 010 eggs), was significantly positively related to both standard length (SL) (P < 0.05) and ovary‐free body weight (OFBW) (P < 0.05), both parameters being good predictors of BF (r² = 30.8% for SL, from 22 cm onwards, and r² = 29.6% for OFBW, from 129.5 g onwards). No significant differences in monthly BF were found throughout the spawning season. Relative batch fecundity was 336 eggs/g OFBW; thus, estimate for potential annual relative batch fecundity was 7526 eggs g^?1 OFBW. The oocyte diameter–frequency distribution analysis revealed a multimodal distribution (at 100–200, 300–400 and 500–700 μm), confirming the evidence of multiple spawning.