Relative Fecundity Research Articles

Primary and secondary plant metabolites determining the suitability of pistachio kernels for the carob moth

AbstractThe carob moth, Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae) is a serious pest of fruit and nut crops worldwide that causes significant losses in Iranian pistachio orchards. In order to assess variation among cultivars is susceptibility to carob moth and biochemical correlates, the present study evaluated the suitability of kernels of 10 pistachio cultivars for E. ceratoniae development and reproductive performance under laboratory conditions: 25 ± 1°C, 65 ± 5% RH and a 16:8 (L:D) photoperiod. The primary and secondary metabolites of nuts were quantified and correlated with life history traits and various metrics of biological performance and indices of relative suitability were calculated. Nut protein content averaged 18.4 ± 0.1% and did not vary significantly among cultivars. Two cultivars yielded significantly slower larval development and lower values for relative growth rate, female longevity and fecundity, relative to all others. Suitability indices calculated from moth life history parameters varied by a factor of 4.66 across cultivars, with values <1 for the two most resistant varieties. The latter cultivars were less consumed by larvae and were lowest in carbohydrate content and efficiency of food conversion, but ranked highest in total phenolics, tannins and flavonoids. Linear regressions indicated that carbohydrate content was positively correlated with kernel suitability for larval development and adult reproduction, whereas total phenolics, tannins, flavonoids and anthocyanins were all negatively correlated. The implications of these findings for integrated management of E. ceratoniae in pistachio orchards, and the possibility of improving pistachio resistance to carob moth, are discussed.

Life-history of the Caucasian dwarf goby Knipowitschia caucasica in an Iranian coastal wetland of the southern Caspian Sea

The Caucasian dwarf goby Knipowitschia caucasica is a small fish in the coastal wetlands of the southern Caspian Sea. The objective of this work was to describe its life-history aspects from individuals collected in the Gomishan wetland of Iran, a highly degraded ecosystem. We collected 707 fish along 18 months and calculated a short life span, TL∞=47.25mm for males, and TL∞=43.05mm for females, high mortality rate (1.84 and 5.83 year-1 for males and females, respectively), female dominance (M: F as 1: 1.22), low fecundity (average absolute fecundity: 672 oocytes.female-1 and mean relative fecundity 1209 oocyte.g-1 ), comparatively large oocytes (0.593 mm, ranging from 0.220 to 0.924 mm) and dependence on the wetland for spawning. Given adverse environmental changes in wetlands, we support the hypothesis that life-history traits confer this fish a high probability of extinction.

The relationships of female size with reproductive parameters, egg diameter and larval growth of striped catfish (Pangasianodon hypophthalmus)

This study aimed to quantify relationships between female weight and some reproductive parameters, yolk sac volume, and larval length of striped catfish (Pangasianodon hypophthalmus). Mature fish were selected from the broodstock conditioning tank in a recirculating system. Females (n = 36) weighing 1.7 to 7.0 kg were artificially propagated with the same male group. The results showed that realized fecundity (331,667 - 1,404,791 eggs/female) was positively correlated (P < 0.01), while relative fecundity (73,849 - 255,214 eggs/kg female) had a negative relationship with females’ weight (P < 0.01). Eighteen females were divided into 3 groups of weights (6 - 7 kg, n = 5; 5 - 5.5 kg, n = 8; and 3 - 4.8 kg, n = 5) to examine other reproductive parameters. Egg diameter (1,014 - 1,024 µm), fertilization rate (65.78 - 79.00%), and hatching rate (42.73 - 57.27%) were not significantly different among female groups. Larvae produced by medium and large-sized females appeared to grow (in length) faster than those by small-sized females, and these differences were significant at hatching, 24, and 72 h post-hatch (P < 0.05). Yolk sac volume was not different among the three groups (P > 0.05), ranging from 0.37 to 0.41 mm3 at hatching, and decreasing 62.2 - 68.3% after 36 h and 83.8 - 85.4% after 48 h post-hatch. In sum, females weighing 5 to 7 kg had higher realized fecundity and better growth of larvae during the first five days compared to small females.

Fecundity traits of young ovigerous females of yellow-line-arrow spider crab Stenorhynchus debilis (Brachyura: Inachoididae) in Bahía de La Paz Baja California Sur, México

The southwestern Gulf of California is an important source of ornamental marine species traded worldwide, wherein spider crabs Stenorhynchus debilis are popular items. However, little is known about species biology and ecology. This study involves young ovigerous females (28 in total) recollected at Bahía de La Paz, Mexico, into bivalve mariculture devices cleaned every 3-4 months. Total carapace length (TL) and carapace width (CW), weight without eggs (TW), and fecundity (F, number of eggs) were analyzed for multiple relationships. F varied into 162 and 2205 eggs (x̄ = 1171 ± 689 eggs), their diameter into 0.38 to 0.45 mm (x̄ = 0.396 ± 0.027 mm). Three persistent and interactive modes were detected: low/moderate/high F, small/medium/large size (TL and CW), and light/middle/heavy TW. Log-linearized allometric regressions were applied to determine the relative fecundity constants (RFC) by body complexion, finding high parallelism between TL and CW related to step-wise growth and size categorization upon the isosceles-shaped carapace. In contrast, TW denoted an increase in body complexion across intermolt phases. S. debilis likely completes three maturation/molt cycles within 3-4 months after the first crab instar. RFC values confirmed positive trends by body complexion where egg size and F are related to species size and shape, establishing the trade-off proportions in this study case.

Indications of an Achaea sp. caterpillar outbreak disrupting fruiting of an ectomycorrhizal tropical tree in Central African rainforest

Background and aims – Where one or several tree species come to dominate patches of tropical forest, as many masting ectomycorrhizal legumes do in Central Africa, ecological theory predicts they may be prone to herbivory, which might alter their reproductive output. This was indirectly investigated in lowland rainforest in Cameroon for Tetraberlinia korupensis, whose crowns were attacked in 2008 by an outbreaking black caterpillar—identified as an Achaea sp., probably A. catocaloides—in Korup National Park. Material and methods – Field-collected data on tree-level seed and fruit (pod) production of T. korupensis in its 2008 masting event were compared with that of its two co-dominant neighbours (T. bifoliolata, Microberlinia bisulcata), whose populations masted in 2007 (and 2010). To do this, bivariate regression models (linear, polynomial, ZiG [zero-inflated gamma model]), contingency table analysis, and non-parametric measures of dispersion were used. Key results – Assuming T. korupensis is prone to Achaea caterpillar attacks, empirical data support the hypothesized lower proportion of adults participating in its masting (54% in 2008) than for either masting population of M. bisulcata (98% in 2007, 89% in 2010) or T. bifoliolata (96% in 2007, 78% in 2010). These fruiting T. korupensis trees were about one-third larger in stem diameter than conspecific non-fruiters and produced as many pods and seeds per capita as T. bifoliolata. However, regressions only modestly support the hypothesis that the positive tree size–fecundity relationship for T. korupensis was weaker (i.e. lower adj. R2) than for M. bisulcata (whose leaves are morphologically similar) or T. bifoliolata, with mostly similar dispersion about the median among these species. Conclusion – Altogether, the findings suggest a role for tolerance in nutrient-poor forests. It is postulated that instead of conferring resistance to herbivores, the ectomycorrhizas associated with these trees may enable them to more quickly recover from potential yet unpredictable insect outbreaks.

Fecundity strategy of the highly exploited limpet Patella ordinaria from an oceanic archipelago

Limpet harvesting dates to the 15th century in Madeira archipelago (NE Atlantic Ocean). This activity is size-selective, removing older and larger individuals with greater commercial value. It can lead to a lower reproductive output as individual fecundity is size-dependent. The decrease of limpet populations has led to the implementation of a series of management measures including a closed season during the reproductive season (November–March). So far, sizes and the reproductive parameters, size and age at first maturity, have been previously used to determine the exploitation status of Patella ordinaria in Madeira archipelago, with no study performed on the reproductive strategy of this limpet. This is pivotal to comprehend the population dynamics of any species, being fecundity one of the reproduction parameters that should be analysed. This work aims to provide for the first time data on the fecundity of P. ordinaria. An average of 17 females per month were randomly collected over the spawning 2021/2022 season from the subtidal rocky shores of the Madeira archipelago. Four criteria were analysed over the spawning season: (i) the presence of a hiatus between pre- and vitellogenic oocytes; (ii) the number and (iii) mean size of advanced vitellogenic oocytes; and (iv) the incidence of atresia. A hiatus between pre- and vitellogenic oocytes across the spawning season was observed. An increasing trend in the number of vitellogenic oocytes was observed over the spawning season. The size of vitellogenic oocytes showed significant differences among months and the relative intensity of atresia varied from 7.86 to 20.79%. The information on the fecundity strategy leads to a better understanding of the reproductive capacity of this species. It also identifies the best approach for future estimations of relative annual fecundity estimations, with direct implications on the sustainable exploitation of this commercial species.

Age, growth, reproduction and status of resource development of Ptychidio jordani, a critically endangered freshwater fish in the Hongshui River, China.

The age, growth, reproduction and resource development status of Ptychidio jordani, as a critically endangered freshwater fish in the Hongshui River, China, was studied in this work. A total of 525 specimens were collected monthly using the cages and gillnets from October 2021 to September 2022 in the Hongshui River. The scale was used for age determination, and the maximum age for both female and male was estimated to be 5 years and 3 years, respectively. Female and male P. jordani showed different growth patterns, which were expressed as Lt =261.3 (1-e-0.4885(t-0.1476) ) and Lt =251.2 (1-e-0.4758(t+0.9643) ), respectively. The overall sex ratio was 1:0.47 (female:male). Female attained sex maturity at 2.34 years (192 mm body length). Month variation of the gonad somatic index indicated that the spawning period occurred from April to October. The absolute fecundity was estimated at 9046 ± 3434 eggs per individual, and the relative fecundity was 38.08 ± 15.77 eggs per gram. The exploitation rate of female and male was 0.233 and 0.495, which indicated that P. jordani was not overfishing. This study provided data on the key life-history traits of P. jordani, which has not been known previously and is essential for conservation strategy and policy development.

Experimental and theoretical support for costs of plasticity and phenotype in a nematode cannibalistic trait.

Developmental plasticity is the ability of a genotype to express multiple phenotypes under different environmental conditions and has been shown to facilitate the evolution of novel traits. However, while the associated cost of plasticity, i.e., the loss in fitness due to the ability to express plasticity in response to environmental change, and the cost of phenotype, i.e., the loss of fitness due to expressing a fixed phenotype across environments, have been theoretically predicted, empirically such costs remain poorly documented and little understood. Here, we use a plasticity model system, hermaphroditic nematode Pristionchus pacificus, to experimentally measure these costs in wild isolates under controlled laboratory conditions. P. pacificus can develop either a bacterial feeding or predatory mouth morph in response to different external stimuli, with natural variation of mouth-morph ratios between strains. We first demonstrated the cost of phenotype by analyzing fecundity and developmental speed in relation to mouth morphs across the P. pacificus phylogenetic tree. Then, we exposed P. pacificus strains to two distinct microbial diets that induce strain-specific mouth-form ratios. Our results indicate that the plastic strain does shoulder a cost of plasticity, i.e., the diet-induced predatory mouth morph is associated with reduced fecundity and slower developmental speed. In contrast, the non-plastic strain suffers from the cost of phenotype since its phenotype does not change to match the unfavorable bacterial diet but shows increased fitness and higher developmental speed on the favorable diet. Furthermore, using a stage-structured population model based on empirically derived life history parameters, we show how population structure can alleviate the cost of plasticity in P. pacificus. The results of the model illustrate the extent to which the costs associated with plasticity and its effect on competition depend on ecological factors. This study provides support for costs of plasticity and phenotype based on empirical and modeling approaches.

The effectiveness of Ovaprim, Ovopel, and their combinations in artificial reproduction of common rudd Scardinius erythrophthalmus under controlled conditions

In this study, a practical protocol for artificial reproduction was developed for the rudd, Scardinius erythrophthalmus, to help to produce this fish for aquaculture industries and also for restocking programs. For this purpose, the efficiency of different hormonal agents and their combinations for spawning induction of female breeders of rudd was evaluated. Ovulations were stimulated using different treatments as: two injections of Ovaprim (Ova), two injections of Ovopel (Ovo), a priming dose of Ovopel with a resolving dose of Ovaprim (Comb1), a priming dose of Ovaprim with a resolving dose of Ovopel (Comb2), and two injections of sterile 0.9% NaCl solution as a control group. During the study, ovulation success, egg developmental competence as well as the performance of the freshly hatched larvae were recorded. There was no ovulation in females from the control group. In hormone-treated groups, 84–100% of fish ovulated, but no differences were observed in ovulation success (P > 0.05). The shortest latency period in treated fish was recorded in the Ovo group (431.6 degree-hour, P < 0.05). The best results in terms of working fecundity (number of obtained eggs per fish), relative fecundity, fertilization success, hatching rate, and embryo survival up to the eyed stage were achieved in the Ova and Comb1 groups (P < 0.05). Moreover, better survival rates up to the absorbing yolk sac stage and the lowest abnormality of larvae were observed in Ova and Comb1 groups (P < 0.05). There was no significant difference in the incubation time among different groups (P > 0.05). The obtained results indicate that two injections of Ovaprim and/or a priming dose of Ovopel with a resolving dose of Ovaprim are suitable for the artificial reproduction of rudd female breeders. Due to the proper effects and ease of use, two injections of Ovaprim could be recommended for the production of this species for restocking or aquaculture programs.

Reproduction parameters of hatchery reared grayling (Thymallus thymallus) females

European grayling (Thymallus thymallus) is an endangered salmonid fish species and its populations have decreased considerably in European waters in recent decades. One of the conservation measures applied to grayling is stocking with hatchery-reared fish. To advance the knowledge of grayling reproduction in the hatchery, husbandry data were systematically collected in the period from 2006 to 2015 during grayling spawning seasons and analyzed to quantify grayling female reproductive parameters such as fecundity, egg size, and embryo survival to the eyed egg stage. Data was collected for first time spawners (3 years old) and repeat spawners reared in the hatchery. Statistically significant differences were found for the number of eggs between first time spawners, producing on average 3600 eggs, and repeat spawners, producing on average 8000 eggs. Absolute fecundity was positively correlated to grayling female total length and weight for both first time and repeat spawners. However, relative fecundity did not correlate with these parameters. A positive correlation was observed between female total length and mean egg weight for repeat spawners, while the correlation was negative for first time spawners. Heavier eggs tended to have a higher rate of survival until the eyed egg stage, though the correlation was stronger for first time spawners than for repeat spawners. Due to the higher reproductive success of repeat spawners, it could be concluded that larger and older grayling females should be included in hatchery reproduction.

Induced reproduction of yellow-tailed lambari (Astyanax lacustris) with Ovopel® and buserelin acetate as alternatives to the protocol with carp pituitary extract.

The objective of this study was to evaluate reproductive traits in adults of Astyanax lacustris subjected to different spawning inducers. The study involved 240 females (12.54 g ± 2.33 and 7.66 cm ± 0.63 cm) and 240 males (5.83 g ± 0.39 g and 6.14 cm ± 0.64 cm), all at reproductive age. Three different inducers were evaluated: (i) 0.4 pellets of Ovopel®/kg of body weight; (ii) 0.5 ml of buserelin acetate/kg of body weight; and (iii) carp pituitary extract (CPE) (5.5 mg CPE/kg body weight for females and 2.5 mg CPE/kg body weight for males), as well as saline solution (without hormone). The degree-hours for spawning were greater (P<0.05) for the Ovopel® treatment (with 204.93) than in the treatment with CPE (183.2). Ovary weight and gonadosomatic index were higher (P<0.05) in CPE and Ovopel® treatments when compared to buserelin acetate. The number of oocytes per female, absolute and relative fecundity were greater (P<0.05) for Ovopel® and CPE treatments. Fertilization rate was higher (P<0.05) in treatment with buserelin acetate (82.3%) in relation to Ovopel® (72.33%) and CPE (62.40%) treatments, and the highest (P<0.05) hatching rates were achieved with buserelin acetate and Ovopel®. The number of larvae per female body weight was greater (P<0.05) when Ovopel® was used. In conclusion, Ovopel® proves to be a more effective reproductive inducer for induced reproduction of A. lacustris when compared to CPE and buserelin acetate.

Fecundity of Glyptothorax telchitta (Hamilton, 1822) from Tamor River, Nepal

The present study assesses the fecundity of Glyptothorax telchitta, a hill stream fish from the Tamor River, Nepal. A total of 60 specimens were collected from the Tamor River, with the help of local fishermen between March 2019 and February 2020. The absolute fecundity ranged from 3385 to 14298 eggs with the mean absolute fecundity of 9448.469 ± 607.783. The fish was found to be a medium fecund fish. Relative fecundity ranged from 151 to 529 eggs per gram body weight with mean relative fecundity of 371.38 ± 15.72. Fecundity showed significant positive correlations with ovary weight (r = 0.858) total length (r = 0.844) and total weight (r = 0.825). This indicated that fecundity dependent is mostly on ovary weight. Gonado-somatic index scored the peak values during March (15.15%) and May (15.01%), indicating the fish’s spawning period during the spring season. Egg sizes varied from 0.382 mm to 1.149 mm. The appearance of various sizes of eggs in a single ovary indicated that the fish was a fractional spawner. The ovaries occupied maximum space in the abdomen during the breeding season.

Рибницько-біологічна та продуктивна характеристика плідників дунайського лосося (Hucho hucho Linnaeus, 1758) в умовах ДУ «Рибоводний форелевий завод ”Лопушно”»

Purpose. Study and improvement of the reproduction technology of Danube salmon under artificial conditions. Research and analysis of morphological and reproductive parameters of brood Danube salmon reared on artificial feeds. Methodology. The work describes the generalized results of studies carried out during 2018–2020. Morphological and reproductive parameters of brood Danube salmon reared in ponds of the trout farm “Lopushno” were investigated. Healthy age-6-8 brood fish grown using certified specialized artificial feeds of European manufacturers were used for the study. Brood fish were fed with high-protein feed of the Danish manufacturer Efico Alfa 717 (particle size of 6 mm). Findings. The body weight of age-6 Danube salmon females had a wide range of fluctuations ranging from 1700 to 3700 g; body length ranged from 62 to 78 cm, respectively. The limits of fluctuations in body weight in males were from 1850 to 3400 g, in body length from 61 to 78 cm. The average weight of age-7 brood Danube salmon used in spawning was 3331.3 g, and the average length was 74.9 cm. The limits of variation in weight for males were from 2600 to 4850 g, for females – from 2350 to 3500 g; in length: females ranged from 66 to 78 cm, males ranged from 67 to 84 cm. Average weight gain of brood fish was 553 g per year. The body length to height ratio in age-6 brood fish was 6.1 and was higher than in 2019 in age-7 brood fish (5.1), age-6 fish were more oblong. The condition factor in age-6 fish was 0.69, in age-7 fish 0.77 units. The collection of eggs from age-6-7 brood fish was carried out without stimulation. The results of reproductive parameters in age-6-7 females were as follows: the working fertility in age-6 fish ranged from 5882 to 7794 eggs, working fertility in age-7 fish ranged from 6958 to 8671 eggs, relative fecundity in age-6 females had a high result: on average, it was 3219 eggs versus age-7 fish - 2552 eggs. The average weight of age-8 brood Danube salmon used in spawning was 3890.3 g with an average length of 76 cm. The limits of weight fluctuations: in males were 3300–4800 g, in females – 3000–4500 g; in length: 72-82 cm and 72-80 cm, respectively. The analysis of reproductive parameters of age-8 females showed that their average working fertility was 10,980 eggs. Compared to age-8-9 females from natural water bodies, the average working fertility of females grown in artificial conditions was 20% higher. Originality. The monitoring of linear and weight growth of brood Danube salmon of different ages in artificial conditions was carried out. A comprehensive mechanism of scientific principles and methodical recommendations for the artificial reproduction of Danube salmon in order to preserve its abundance in the water network of the Carpathian region has been developed. Practical value. The obtained results can be used to improve the technology of reproduction of salmonids in artificial conditions. Key words: brood Danube salmon, working fecundity, relative fecundity, State Enterprise Trout Farm “Lopushno”.

Рибогосподарська оцінка плідників сибірського осетра (Acipenser baerii Brandt, 1869), вирощених у плавучих садках за природної температури води Лісостепу України

Purpose. To determine and evaluate the main fishery parameters in the process of artificial production of mature eggs from brood Siberian sturgeon grown in floating cages at natural water temperature of the Forest-Steppe of Ukraine. Methodology. The material for the study was 121 specimens of Siberian sturgeon females of various ages with body weights from 3.80 to 16.84 kg, which were cultivated in industrial-type farming conditions in a water body with a natural temperature regime for the Forest-Steppe zone Ukraine with the use of floating cage systems. Experiments on obtaining mature eggs were carried out under controlled water temperature during the period from January to April under the conditions of a recirculation aquaculture system. Hormonal stimulation for the maturation of sturgeon gonads was performed using natural cyprinid pituitary preparations. Determination of fishery indicators and study of environmental abiotic factors were carried out according to methods generally accepted in fish farming and hydrochemistry. Findings. The efficiency of maturation in brood fish of different groups varied between 57–100% at a water temperature of 14.0–15.5°C after the injection of a gonadotropic drug with a total dose from 2.5 to 4.5 mg/kg per fish weight. A total dose of the gonadotropic drug of 3.5 mg/kg per fish weight was found to be sufficient for the high efficiency of gonad maturation. The weight of mature eggs obtained from brood fish aged 8+ to 17+ varied on average from 0.54 to 2.12 kg. The average working fecundity and relative fecundity in females of different ages varied, respectively, within the range of 33.60-108.21 thousand eggs and 6.62-7.95 thousand eggss/kg of fish weight, with average values of the gonadosomatic index of 10.71-15.81%. Originality. The peculiarities of obtaining ovulated eggs and the main fishery parameters of brood Siberian sturgeon cultivated using the technology of intensive sturgeon aquaculture, which is not common in Ukraine, were studied. Practical value. The study results can be used for the development of modern methods of sturgeon aquaculture in the industrial farms conditions. Keywords: brood Siberian sturgeon, industrial fish farming, fishery parameters, ovulated eggs, combined aquaculture technology.

Some Observations on the Reproductive Biology of the Mediterranean Pennatulacean Pteroeides Spinosum (Ellis and Solander, 1786) (Cnidaria: Octocorallia: Pennatulacea)

Sea pens are some of the most important structural species in soft bottom benthic communities. Pteroeides spinosum is a shallow-water pennatulacean (Cnidaria: Octocorallia: Pennatulacea) habiting NE Atlantic-Mediterranean bottoms. In this study, sixteen colonies of Pteroeides spinosum collected from NW Mediterranean Sea (Cap de Creus, Spain) at 99–106 m depth in July (2012), were used to acquire information of their reproductive biology, and to enable a comparison with other pennatulaceans. Our colonies of Pteroeides spinosum are gonochoric showing a bimodal oocyte frequency distribution and an unimodal spermatocyst diameter distribution. All polyp leaves contained oocytes and spermatocysts in different size classes, with those small and translucent spermatocysts/ oocytes (size-class I) often found near the base or lower end of the gastrovascular cavities of polyps. The largest observed diameter was 668 μm for spermatocysts and 687 μm for oocytes. Mean potential relative fecundity (PRF) ranged between 7–17 oocytes per polyp. The effective reproductive effort (ERE) reached a value of ca. 30,000 large oocytes per colony. As was observed for all pennatulaceans previously studied, no sign of hermaphroditism or internal fertilization was detected in our colonies of Pteroeides spinosum.

Influence of maternal effects and temperature on fecundity of Sebastes fasciatus on the Flemish Cap

The conservation of a sufficient reproductive potential of an exploited stock is one of the goals of fisheries management, as it ensures sustainable productivity. However, there is evidence that spawning stock biomass (SSB) does not represent well the variation in stock reproductive potential, often leading to impaired stock-recruitment relationships. In this study we show that fecundity of Sebastes fasciatus on Flemish Cap is not proportional to SSB and shows temporal fluctuation influenced by maternal effects. Females were collected in 23 research surveys between 1996 and 2020. An autodiametric calibration model was developed for S. fasciatus for the first time to estimate fecundity. Mean potential fecundity was estimated as 36000 oocytes and mean relative fecundity as 79 oocytes g–1. Potential fecundity varied significantly with female length, age, condition index, gonadosomatic index and environmental variability. Mixed-effect linear models were fitted to assess the effect of maternal traits and bottom temperature on fecundity. Fecundity increased significantly with condition factor and sea bottom temperature. Relative fecundity also increased significantly with length, age and gonadosomatic index, indicating that older, larger and better-conditioned females produce more eggs per female gram. This suggests that SSB is not a good proxy to stock reproductive potential so it is unsuitable for use in stock assessment and scientific advice. Considering that S. fasciatus is a viviparous species, future research should focus on maternal effects on offspring and on building time series of reproductive potential indexes that take into account maternal effects.

Induced spawning of African catfish (Clarias gariepinus) using goat (Capra aegagrushircus) and pig (Sus scrofa domesticus) pituitary extracts

Concerns relating to cost and availability have directed traditional farmers to expand options on the induced spawning of fish for viable production of seeds. The study was conducted to examine the potential of using pituitary extracts (PE) from goat (Capra aegagrushircus) and pig (Sus scrofa domesticus) on the induced spawning of African catfish (Clarias gariepinus). Pituitary extract of African catfish using 4 mgkg–1 body weight dosage (control) and PE from goat and pig using 4 mgkg–1 and 200 mgkg–1 body weight dosages were single intramuscularly injected to female breeders. Utilisation of goat and pig PE has successfully induced the spawning of African catfish. All female breeders attained ovulation within 10-12 h which is under the prescribed latency period. Total number of eggs spawned ranged from 36200-67600. The three PE used attained comparable result in terms of relative fecundity. Fertilisation rate revealed that PE from goat at 4 mgkg–1 dosage attained similar result to that of control treatment. Hatching period occurred within 24–36 h and goat PE using both dosages gave the highest results in hatching rate. The current study provides preliminary information on the success of using PE from goat and pig for the induced spawning of African catfish.

Evolution of sex ratio and egg production of gilthead seabream (Sparus aurata) over the course of five reproductive seasons

Spawning performance -relative fecundity and fertilization success- was studied in two hatchery-reared broodstocks of gilthead seabream (Sparus aurata) held under relatively constant well-water temperature (18–20 °C) and simulated natural photoperiod, for five consecutive spawning seasons, between 3 and 7 years of age. The spawning season lasted between 4 and 6 months each year, and the total number of eggs produced annually ranged between 1 480 000 and 3 100 000 eggs/kg female body weight, being the highest during the first and second spawning season. No difference was observed in monthly relative fecundity between years -although high variation existed within years, whereas fertilization success was the highest during the second and third reproductive season, and dropped significantly during the last year of the study. The male percentage of the broodstocks was 35% during the first spawning season of the females, and thereafter it decreased further and remained stable at around 15%–20% for the second and third spawning season. Substitution of older females with smaller males to readjust male percentage to 50% in the fourth spawning season, was followed by sex change of larger males to females and a drop of the male percentage to 18% in the following spawning season. The present study demonstrated the long spawning season of gilthead seabream -especially under constant water temperature, the high fecundity and fertilization success, and the stabilization of male percentage to ∼20% after the first spawning season or when a broodstock is modified to increase male percentage. These results are useful to the aquaculture industry, demonstrating that there is no need to add males to gilthead seabream broodstocks over the years, as the sex ratio is stabilized and egg production and fertilization success remain high with a relatively low male:female sex ratio.

Assessment of Spawning Fecundity and Its Relationship with Body Parameters of Rainbow Trout (Oncorhynchus mykiss) and Brown Trout (Salmo trutta fario)

The present investigations were carried out at Trout Culture Farm Laribal, Srinagar (J&amp;K Govt.), India during December, 2020. Relationship between length-weight, spawning fecundity and relative fecundity was observed in rainbow trout (O. mykiss) and brown trout (S. trutta fario). The mean length of male rainbow trout was (38.77±1.38 cm) and mean length of (38.05±1.32 cm) was observed in female rainbow trout. While as, the mean length of male brown trout was (38.86±1.41 cm) and for female brown trout mean length of (37.98±1.30 cm) was observed. The mean weight of male and female rainbow trout recorded was 794.6±49.3 g and 766.3±64.3 g respectively, while as, the average weight of male and female brown trout was 772.7±41.4 g and 757.6±57.22 g respectively. The spawning fecundity female-1 of rainbow trout ranged from 2002−2804 eggs and mean relative fecundity of 3.13±0.12 g-1 body weight was observed and for brown trout the spawning fecundity female-1 fish ranged from 961 to 1604 eggs, with a relative fecundity of 1.41 g-1 body weight to 1.56 g-1 body weight. The present study recorded a significant positive correlation between total body length and total body weight of male rainbow trout (r=0.938, p&lt;0.05) and total body length and total body weight of female rainbow trout (r=0.989, p&lt;0.05) and for brown trout a significant positive correlation was recorded between total body length and spawning fecundity, body weight and spawning fecundity was observed. However, relative fecundity formed a significant negative correlation between total length, body weight and spawning fecundity in brown trout.

Length-weight relationship, relative condition factor and fecundity of Notopterus notopterus (Pallas, 1769) from river Brahmaputra in Dhubri, Assam, India

Notopterus notopterus (Pallas, 1769) commonly known as bronze featherback is an important freshwater fish widely distributed in deep and clean waters in the rivers, beels, reservoirs and ponds. This study elucidates the length-weight relationship (LWR), relative condition factor and fecundity of N. notopterus collected from the river Brahmaputra in Dhubri, Assam, India. A total of 181 fish specimen were sampled. The LWR showed a positive isometric growth with uniform increase in height or width with increasing length. The value of a and b in males were 0.0120 and 3.06 respectively. In females, a and b were slightly higher being 0.0230 and 3.18 respectively. The coefficient of determination for combined sex was equal to 0.8572 (p &lt; 0.001). The relationship between the fecundity and four variables viz. total length, body weight, gonadal length, gonadal weight were analysed and the relationship between the fecundity and gonad weight was much more significant than other variables considered. The current study might serve as a valuable guideline for establishing future biometric studies for fishes collected from this stretch of the river Brahmaputra.