Reproductive biology of Oreochromis mossambicus populations of man-made lakes in Sri Lanka: a comparative study

Abstract. The sex ratio, mean size at maturity (L_m), gonosomatic index (GSI), frequency of distribution of egg diameter of the mature ovaries and fecundity of Oreochromis mossambicus (Peters) populations of 12 man-made lakes were studied using commercial landings from the gill-net fishery. The overall sex ratio was 1·0:0·88 of females to males and that of the individual populations varied from 1·0:0·54 to 1·0:1·34. The L_m ranged from 16·0 to 21·0 cm (TL) and was found to be correlated to the size of the water-body. The GSI of the females in stage V, the stage prior to spawning, did not differ from each other, except in one reservoir. The variations in the mean egg size (μ) of different populations were negatively correlated to the fecundity of a Ash of standard weight (FW₂₀₀) of the different populations and the relationship was, y =3487·4– 1·14FW₂₀₀(df = 10; r= -0·64; P < 0·05) The overall fecundity ranged from 318 to 3169 in fish ranging in body length (TL) and body weight from 16·5 to 32·0 cm and 80 to 651 g respectively. Fecundity was linearly related to body weight and curvilinearly to body length. The exponent b of the fecundity (F) length (1) regressions (F = aL^b) of the different populations varied between 1·20 and 3·83. The overall relationship of fecundity to body weight (W) and body length (1) for O. mossambicus reservoir populations in Sri Lanka were: F = 3·23W + 357·8 (df = 203; r= 0·73; P < 0·001) F = l·52L^2·11(df = 203; r= 0·68; P < 0·001) The variations in the theoretical fecundity calculated for a standard size individual of 200 g in weight (FW₂₀₀) of the reservoir populations were correlated to the mean fishing pressure (X) exerted on each population according to the equations. (a) FW₂₀₀= 10–24X+ 896·8 (df 9; r= 0·58; P < 0·05) (b) FW₂₀₀= 1200 – 422·76e^?0·102X (df 9; P < 0·05)     

繁殖季节长江口斑尾刺虾虎鱼的形态、生殖力与卵巢组织学特征

在繁殖季节研究了斑尾刺虾虎鱼的形态、生殖力与卵巢组织学特征。结果表明,斑尾刺虾虎鱼全长(TL)与体长(SL)、头长(HL)与体长(SL)、体长(SL)与体高(BD)、体重(BW)与空壳重(SW)、体重(BW)与体长(SL)的相关关系分别为:TL=0.779 6SL+1.793 9;HL=0.299 9SL+7.288;SL=0.783 2BD+7.324 9;BW=0.818 4SW-4.979 6;BW=0.062 9SL2.331 5。斑尾刺虾虎鱼个体绝对生殖力(F)为6 328~59 878 egg,与体长(SL)、空壳重(SW)、卵巢重(OW)的相关关系分别为F=94.972SL2-4 832.2SL+833 435;F=83.823SW+14 084;F=507.54OW+13 190。个体绝对生殖力(F)与体长、空壳重、卵巢重、成熟系数(GSI)的多元回归方程为:F=2 375.54+525.67SL-31.44SW+199.43OW+261.74GSI。斑尾刺虾虎鱼体长相对生殖力(FL)平均为88±31 egg/mm,体重相对生殖力(FW)平均为157±54 egg/g。平均卵径为1.22±0.24 mm。斑尾刺虾虎鱼IV期卵巢以第IV时相卵母细胞为主,第IV时相晚期卵母细胞开始出现油球,细胞核偏移和变形,放射带明显;Ⅴ期卵巢的卵细胞游离,卵膜外的二层滤泡膜脱落,卵细胞的外层分别有胶膜、放射带和质膜。     

长江中游贝氏(鳖)繁殖生物学研究

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

虹鳟养殖品系个体繁殖力遗传进展的初步研究

自2004年至2009年历经两个世代研究了5个虹鳟(Oncorhynchous mykiss Walbaum)品系的相对繁殖力、绝对繁殖力与形态学指标的关系及其遗传进展。结果显示:美国加州、美国道氏、挪威品系的繁殖力指标好于丹麦和渤海品系。各品系绝对繁殖力与体长呈幂函数关系,即F=7.2071L1.6099(R2=0.6479,P<0.01),绝对繁殖力与体重呈线性关系,F=2243.1+1235.3W(R2=0.7371,P<0.01)。绝对繁殖力随着卵径的增加而呈增加趋势,但卵径达到(0.4±0.1)cm时这一规律不明显。5个品系子一代优势选育系(G1优势选育系)与基础种群相比较,绝对繁殖力的平均遗传进度为24.06%。     

Fecundity, egg size and total egg volume differences in 12 stocks of rainbow trout, Oncorhynchus mykiss Richardson

Abstract. Measurements of egg number, egg size and total egg volume in relation to post-stripped weight, made on the eggs stripped from 12 separately maintained farm stocks of 4-year-old rainbow trout. Oncorhynchus mykiss Richardson, revealed highly significant differences between populations when analysed by regression and covariance statistical techniques. All of the stocks showed increases in fecundity with increasing fish size, with 61% (coefficient of determination or r²) of the variation in fecundity of the 12 stocks explained by the common regression on parental fish size. Comparison of the regressions of the different stocks revealed that the rate of increase of fecundity with increasing fish weight was constant throughout the weight range (i.e. the regressions had similar slopes) although there were highly significant differences in elevation, with some stocks producing almost twice as many eggs as some of the others. By contrast, the relationship of egg size with fish weight was much more variable with three of the stocks showing no significant regression of egg size on fish weight and a further two stocks with data poorly fitted to the regressions. Of the remaining seven stocks only one showed a significant difference in slope of the regression with modest increases in fish weight being associated with large increases in egg size. Only four of the remaining stocks of fish showed significant differences in the elevation of their regressions, i.e. the egg sizes were significantly different after the potentially conflicting influence of fish size was partitioned using covariance techniques. Assessments of total egg volume produced far improved regressions on post-strip weight with 75% (r²) of the variation in the pooled data of the 12 stocks being described by the line of the common regression. In general, there appeared to be a “trade-off” between egg number and size with the most and least fecund fish producing somewhat smaller and larger eggs respectively. All 12 regressions of totai egg volume on fish weight showed a common slope. However, there were significant differences in elevation of the regressions, with some of the stocks of trout producing up to a 55% greater volume of eggs. There appeared to be no relationship between the differences in egg number, size or total egg volume and the type or geograpfiical location of the farms on which the stocks were held. Although it remains to be determined to what extent these differences in reproductive performance are Inheritable, it is recommended that these characteristics should be taken into account by hatcheries in tbe design of long-term broodstock selection programmes for rainbow trout.     

Effects of unilateral ovariectomy on recruitment and growth of follicles in the rainbow trout,Oncorhynchus mykiss

Virgin female rainbow trout, Oncorhynchus mykiss, were unilaterally ovariectomised at various stages of ovarian development to investigate the effect of the removal of one ovary on subsequent recruitment and growth of follicles in the remaining ovary. The right ovary was removed from groups of 12–15 fish, 12, 7 and 4 months before they were due to ovulate, and the gonadosomatic index and follicle number and size determined just prior to ovulation. There were no differences in fecundity or follicle size in fish unilaterally ovariectomised at 12 and 7 months prior to ovulation compared to the controls. However, in the females unilaterally ovariectomised 4 months prior to ovulation, the remaining ovary either had the normal number of follicles for a single ovary but of a significantly larger size than follicles in the controls, or alternatively had almost 70% more than the normal number of vitellogenic follicles but comprising two distinctly different size populations. Differences in plasma oestradiol-17β concentrations at the final sample were seen only in females unilaterally ovariectomised 4 months prior to ovulation, where the levels were significantly lower than both the sham operated and control fish (p < 0.05). These data show that in the rainbow trout, complete compensatory ovarian hypertrophy following unilateral ovariectomy can occur throughout a major part of ovarian development, but that follicle recruitment is limited to stages up to (and therefore fecundity is determined by) mid-vitellogenesis.     

Reproductive biology of common silver biddy Gerres oyena in Okinawa Island of southern Japan

ABSTRACT:   Common silver biddy Gerres oyena were collected monthly between November 2002 and November 2005 in Okinawa Island of southern Japan. The seasonal reproductive cycle of this species was investigated using the gonadosomatic index (GSI) and through histological observation of gonads. Temporal variation in the GSI reflected gonadal development from histological observations; ovary development occurred from March to September and testes development occurred between March and August. Maximal development was observed in April and May in both sexes. While mean values for hepatosomatic and lipidosomatic indices decreased markedly in females relative to males during gonadal development, mean condition factors decreased with gonadal recrudescence in both sexes. The minimum standard length (SL) at sexual maturity was 89.7 mm for females and 81.4 mm for males and the size at which 50% of individuals were sexually mature was 104 and 92 mm SL in females and males, respectively. The power relationships of batch fecundity (BF) versus standard length (SL, mm) and body weight (BW, g) of females can be expressed as BF  = 46.7 × e^{1.64 SL} and BF  = 19 697 × e^{0.49 BW} , respectively.     

Testing hypotheses about fecundity, body size and maternal condition in fishes

Recent research suggests that maternal condition positively influences the number of eggs spawned in fishes. These studies commonly choose a priori to use body length rather than weight as an explanatory variable of offspring production, even though weight is usually the better predictor of fecundity. We are concerned that consistent exclusion of body weight as a predictor of egg production inflates the variance in fecundity attributable to maternal condition. By analysing data on three populations of Atlantic cod (Gadus morhua, Gadidae) and 10 populations of brook trout (Salvelinus fontinalis, Salmonidae), we illustrate the need for a statistically defensible method of model selection to distinguish the effects of maternal condition on egg production from the effects of body size alone. Forward stepwise regression and null model analyses reveal how length‐based regressions can significantly over‐estimate correlations between condition and fecundity, leading us to conclude that the effect of condition on egg productivity may not be as ubiquitous or as biologically important as previously thought. Our work underscores the need for greater statistical clarity in analyses of the effects of maternal condition on reproductive productivity in fishes.     

Reproductive Biology of Puntius sarana, an indigenous species, and Tilapia rendalli (melanopleura), an exotic, in an Ancient Man-Made Lake in Sri Lanka

Investigations on the reproductive biology of Puntius sarana an indigenous species and Tiiapia remialli (melanopleura) an exotic, in an ancient man-made lake, Parakrama Sarnudra (Sea of Parakrama), in Sri Lanka, carried out from February 1978 to May 1979 are presented. The overall female to male ratio in T. rendalli and P. sarana were 1.1:1.0 and 1.5:1.0, respectively. Considerable deviation from the mean ratio was observed and are attributed to their spawning behaviour and migrations. In the larger size groups in T. rendalti males were dominant while the reverse was observed in P. sarana. Both species were found to breed through out the year, with well defined peaks in the case of P. sarana which were coincidental with the main rainy seasons. Both species are multiple spawners, fecundity ranging from 760 to 6160 in T. rendalli with length and weight varying from 18.8 to 25.8 cm and 126 to 380 g, respectively. In P. sarana. with a length of 23.8–38.0cm and a weight of 180–792 g, fecundity ranged between 16,000 and 290,000.     

Food consumption of northern pike (Esox lucius L.), estimated with a bioenergetics model

Abstract– A bioenergetics model was used to estimate the food consumption of northern pike ( Esox lucius L.) in two lakes in northeastern Finland, and the results compared with those obtained by a method based on stomach contents and gastric evacuation rates. The annual specific food consumption was 7–5 g per one gram pike for one- and two-year-old pike, and 4–3 g g⁻¹ in age groups 3–6 years old, according to the bioenergetics model. The proportion of ingested food used for growth was 10–30%, and was highest in the youngest age groups. The food consumption rates estimated by the stomach contents method were considerably lower, only about half those produced by the bioenergetics model. The method based on stomach contents tends to underestimate the food consumption. The bioenergetics model was considered more valid for estimating food consumption, but some of the parameter values for northern pike may differ in populations from different latitudes. According to a sensitivity analysis, the food consumption estimate of the bioenergetics model was most sensitive to parameters in the allometric function for respiration.     

中华花鳅的繁殖生物学特性研究

探究中华花鳅(Cobitis sinensis)的繁殖生物学特性,可为其人工增养殖和资源保护利用提供科学依据。2017年11月至2018年5月,在贵州境内舞阳河施秉段采集中华花鳅样本381尾,以鳞片作为年龄鉴定材料,将样本解剖后进行性别鉴定和性腺分期。结果表明,舞阳河中华花鳅体长(L)为58.9~100.2 mm,体重(W)为2.0~13.7 g,年龄在1~4龄。381尾样本中,性别不可辨样本有23尾,雄248尾,雌110尾,性腺发育至IV期最多。经肉眼观察发现,中华花鳅的精巢和卵巢均可分为6期,有70尾雌鱼性腺发育达到IV期,其绝对繁殖力(F)为542~2 865粒,体长相对繁殖力(FL)为6.6~28.6粒/mm,体重相对繁殖力(FW)为99.8~490.7粒/g;绝对繁殖力(F)、体长相对繁殖力(FL)均与体长(L)、体重(W)、净体重(W0)、性腺重(W1)、成熟系数(GSI)之间具有极显著相关性(P<0.01),体重相对繁殖力(FW)与性腺重(W1)、成熟系数(GSI)之间具有极显著相关性(P<0.01)。实地调查发现,中华花鳅的产卵场主要在砂质底质、水质清新、水流较缓、水草丰富的浅水区,繁殖期为5-8月,繁殖高峰期为5月中旬至6月上旬。研究显示,中华花鳅的繁殖力较低,繁殖高峰期时间较短,低龄化严重,亟需对其进行资源保护和系统研究。     

Effects of food supply on size at first maturity, fecundity and growth of hybrid tilapia, Oreochromis niloticus (L.) ×Oreochromis aureus (Steindachner), in outdoor concrete tanks in Saudi Arabia

The effects of four levels of food supply (0.5%, 1%, 2% and 3% body weight daily) were investigated on some reproductive traits and growth of hybrid tilapia in outdoor concrete tanks. Fast-growing fish matured early in the season (March), but spawning started late in May. Smallest size of males and females at first maturity was 8.1 cm. Fish size at maturity appears to be influenced by the feeding level, which affects the growth of fish. For both sexes, no significant difference was found in gonadosomatic index (GSI) among different treatments. Mean percentage of mature fish decreased with decreasing food supply and was found to be significantly different between fishes fed at 3% (46%) and 0.5% (28%) body weight. Fecundity increased with increased feeding levels, although significant differences were found only between 3% and other feeding rates (0.5–2.0%). The fecundity per g female was higher at the lower ration levels (0.5% and 1%) than at the higher feeding levels. Egg quality, with respect to egg size, hatchability. fry length and weight, was not affected by the feeding rates. Final mean weight and food conversion ratios were significantly influenced by feeding rates. Higher increase in ovary weight with increasing body weight of mature females fed at 0.5% body weight than fishes receiving higher food levels suggests that in these fish, more food resources are diverted towards gonad building than to somatic growth.     

Influence of egg size on the growth,onset of feeding,point-of-no-return,and survival of unfed Oreochromis mossambicus fry

The variation in egg size within and between egg clutches of O. mossambicus, and the subsequent influence of mean egg size on growth, feeding incidence and survival of unfed fry were investigated.The individual egg sizes within 90% of the egg clutches examined were normally distributed and the coefficient of variation of egg size within clutches ranged from 7.4% to 15.4%. Fry emerging from the small, medium and large egg size groups reached their maximum length and weight at 9, 9 and 12 days after hatching, respectively. Maximum attainable fry length and weight were significantly correlated with egg size (r = 0.885 and 0.947, respectively, with P < 0.01).Egg size had little influence on the onset of feeding. Fry were capable of exogenous feeding within 6 to 7 days of hatching. Fry originating from small and medium egg size classes reached the point-of-no-return at 15–16 days after hatching compared to 21 days for fry from the large egg size class. The mean survival time (ST₅₀) of fry on their yolk reserves was significantly correlated (r = 0.923; P < 0.01) with their original mean egg weight and ranged from 9.5 days for fry hatching from 0.91-mg eggs to 21 days for fry from 1.93-mg eggs.     

雌性克氏原螯虾性腺发育及相关系数的周年动态研究

建立了克氏原螯虾(Procam barus clarkii)生殖群体的平均体长、体重、性腺重及肝脏重的周年统计值,并利用怀卵量、抱卵量、相对繁殖力等生态学参数建立性腺发育数学模型。结果显示:雌性螯虾初始怀卵和抱卵的理论体长分别为5.6 cm和5.8 cm,理论最大怀卵量和抱卵量分别为1963粒和1136粒;通过模拟Logistic曲线,得到怀卵量随体重增长的3个关键点即始盛期、高峰期和盛末期,分别为16.87 g、36.53 g和56.18 g;雌性克氏原螯虾理论最大相对繁殖力的体长为9.22 cm,最大值为19.78粒/g;其理论最大体长为15.01 cm且当体长小于3.43 cm时性腺尚未发育。另外,本研究还分析了克氏原螯虾产卵群体的性成熟时间与结构。     

Influence of size, age and maternal condition on the oocyte dry weight of Argentine hake (Merluccius hubbsi)

Effects of maternal age–size and condition on oocyte dry weight were analysed for Merluccius hubbsi. Samples of mature females were collected in the Patagonian spawning area during 10 research surveys carried out between 2000 and 2005. Dry weight of 50 hydrated oocytes ranged from 0.80 to 1.90 mg. Relationships of this variable with total length and age were best described by a logarithmic model during the spawning peak. At the beginning and at the end of the reproductive season no significant relationship between these variables was observed, but a decrease in egg dry weight was detected during the spawning period. In general, young spawners (≤5-year-old) showed more variability in egg dry weight, which was associated with a reproductive season shorter than that of old females. Relative condition factor did not shows a significant relationship with oocyte dry weight, and mean values of this index were similar for different months of the spawning seasons analysed.     

Fecundity changes in Macrobrachium rosenbergii (de Man) during egg incubation

Abstract. For a study of the fecundity of Macrobrachium rosenbergii , a total of 117 berried females were sampled from ponds. Fecundity was found to vary from 1216 to 89747 eggs for prawns measuring 9.0cm to 15.8cm total length and weighing 6.22 to 45.80g. The relationship between fecundity (EN) and total length (TL) was found to be EN = 0.001876 TL^6.3617.
The average egg number/g total body weight for prawns having orange, yellow and grey eggs was 1132.7 ± 484.1,766.4 ± 524.3 and 745.5 ± 487.2, respectively, a decrease of 32.3% when orange eggs became yellow and 34.3% when they turned grey. This decrease was probably due to unfertilized eggs dropping off and some eggs being eaten by the brooders during the incubation period.
Egg numbers/g egg weight were found to be 11360.1 ± 1642.1,10715.7 ± 2725.3 and 8634.0 ± 1892.3 for orange, yellow and grey eggs, respectively. When compared to orange eggs, yellow eggs were slightly heavier (6%), but grey eggs were significantly heavier by 31.6%. The increase in the weight of the grey eggs can be explained by the elongation of fully formed organs and appendages by about 17 days post fertilization.     

Dietary Lipid Requirements for Optimal Egg Quality of Redclaw Crayfish,Cherax quadricarinatus

The effect of three crude dietary lipid levels (4, 8, and 12%) on egg quality of the female redclaw crayfish, Cherax quadricarinatus, was evaluated. Three replicate groups of 40 crayfish (mean initial weight ± SD, 23.0 ± 3.0 g) per diet treatment were stocked in 15,000 ‐L tanks, at 28 C. After 75 d of culture, there were significant differences (P < 0.001) in egg area (3.52–3.90 mm²), volume (34.0–39.3 mm³), weight (4.81–5.36 mg), and diameter (2.15–2.27 mm) in response to dietary lipids in the diet. Using the quadratic equation, the maximum responses of these parameters corresponded to lipid levels from 8.60–8.84%. There were no significant differences (P > 0.05) in survival (82.1–86.9%), final weight (41.0–43.7 g), number of spawning females (18.12–27.38%), and fecundity (9.07–10.31 eggs/g female). Additionally, there were no significant differences (P > 0.05) in egg mean protein (2306.87 ± 440.08 μg/egg), lipid (441.95 ± 83.23 μg/egg) and carbohydrate (74.81 ± 10.12 μg/egg) contents, and energy (13.49 ± 2.25 kcal/egg). The optimum overall response was obtained for dietary lipid content of 8.7%, which we recommend to optimize egg quality of this freshwater crayfish.     

Variation in reproductive potential and influence on Icelandic herring recruitment

Explaining recruitment variation in fish is essential for successful fishery management and is consequently under constant review, with an increasing focus on how maternal factors, relative to environmental influences, operate at the level of individual female spawners and extend from the spawning stock through to recruitment. We estimate total egg production (E) in Icelandic summer‐spawning herring (Clupea harengus) from 1963 through 1999 by using sequential population analyses (SPA) and their estimates of stock biomass and recruitment, various size and maturity metrics, and individual fecundity estimates that rely on total length and the condition of the spawners. Generalized linear models indicate that maternal effects are of significance in explaining SPA‐based recruitment‐at‐age‐3 (R). The best model explained 64% of the variation in R and incorporates E constrained to the repeat spawners (40%), the NAO winter index (18%) and ocean temperature (6%). The latter two represent the winter and spring periods subsequent to year‐class formation. Recruit spawner contributions to E were of no significance in explaining variation in R despite the fact that they could contribute as much as 55% of E when their contribution to E was consistently underestimated by a factor of ～ 2, based only on their contribution to spawning stock biomass. We conclude that the spawning potential of the repeat spawners should replace total spawning stock biomass for determining recruitment potential in stock assessment. In addition to the incorporation of oceanographic factors, this would provided a more cautious and risk‐adverse approach.     

Reproductive performance of female rainbow trout Oncorhynchus mykiss (Walbaum) kept under water temperatures and photoperiods of 13° and 51°N latitude

At Doi Inthanon Fisheries Research Unit (DIFRU), Thailand (13°N), rainbow trout were exposed to natural (13°N) and artificial (51°N) photoperiods, and natural water (NW) temperatures and cooled water (CW) 8 months before first spawning. In group I (51°N, CW), water temperatures of 18°C were never reached. In group II (51°N, NW) and group III (13°N, NW), the mean water temperatures in May exceeded 20°C, and 19°C in June and July. Eggs from 94% of all females in group I were obtained before January. This percentage diminished to 84% and 68% in groups II and III. The weight of the spawners and the size of the eggs were significantly lower in group III than in the other groups. No significant differences were observed for egg number per kg body weight of spawners between the groups. The mean fertilization rate of eggs was the highest, with 71%, in group I, and the lowest, with 50%, in group II. For hatching rates, on average 27%, 24% and 30% in groups I, II and III, respectively, differences were not significant. In group III, 37% of all batches reached fertilization rates above 80% and 16% of egg batches showed hatching rates of more than 60%.