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Variation in the degree of sexual size dimorphism (SSD) among taxa is generally considered to arise from differences in the relative intensity of male–male competition and fecundity selection. One might predict, therefore, that SSD will vary systematically with (1) the intensity of sexual selection for increased male size, and (2) the intensity of fecundity selection for increased female size. To test these two fundamental hypotheses, we conducted a phylogenetic comparative analysis of SSD in fish. Specifically, using records of body length at first sexual maturity from FishBase, we quantified variation in the magnitude and direction of SSD in more than 600 diverse freshwater and marine fish species, from sticklebacks to sharks. Although female-biased SSD was common, and thought to be driven primarily by fecundity selection, variation in SSD was not dependent on either the allometric scaling of reproductive energy output or fecundity in female fish. Instead, systematic patterns based on habitat and life-history characteristics associated with varying degrees of male–male competition and paternal care strongly suggest that adaptive variation in SSD is driven by the intensity of sexual selection for increased male size. [ABSTRACT FROM AUTHOR]

Fecundity information is critical in determining reproductive potential of a population. Collecting fecundity data, however, can be cost prohibitive or ineffective if a sampling protocol is not well designed. Inappropriate sampling can lead to biased estimates of fecundity, which may result in biased estimate of reproductive potential. Processing egg samples tends to be time-consuming and labour-intensive. For many fish and crustacean species, fecundity is dependent on female sizes. Nevertheless, at extreme size classes, fecundity may decrease or level off due to senescence. In order to account for this maternal effect, female sample of a wide size range need to be collected for developing a complete relationship between fecundity and body sizes. Using the Gulf of Maine northern shrimp, Pandalus borealis, as an example, we evaluated two sampling strategies, simple random sampling and size-based stratified random sampling, with a different number of sampling locations and different number of animals sampled per sampling location or length interval. The study shows that both the sampling strategies, simple random sampling and size-based stratified random sampling, can generate representative samples. However, the simulation analysis suggests that when the population size distribution is skewed with a lack of large and/or small individuals, size-based stratified random sampling is preferred due to lower variation in differences of means and medians between samples and the population. This study provides a simulation framework for identifying a cost-effective sampling protocol that can improve the estimate of fecundity, leading to an improved estimate of fish population reproductive potential. [ABSTRACT FROM AUTHOR]

Key message: Using COS markers, the study reveals homeologous relationships between tetraploid Agropyron cristatum and bread wheat to support alien introgression breeding of wheat. Crested wheatgrass (Agropyron cristatum L. Gaertn.) is a wild relative of wheat that possesses many genes that are potentially useful in wheat improvement. The species comprises a complex of diploid, tetraploid and hexaploid forms. In this study, wheat–A. cristatum chromosome, telosome and translocation lines were used to characterize syntenic relationships between tetraploid A. cristatum and bread wheat. Prior to mapping COS markers, the cytogenetic stock lines were characterized for fertility and by FISH and GISH for karyotype stability. Out of 328 COS markers selected for the study, 279 consistently amplified products in tetraploid A. cristatum, and, out of these, 139 were polymorphic between tetraploid crested wheatgrass and wheat. Sixty-nine markers were found to be suitable for the detection of tetraploid A. cristatum chromosomes 1P–6P in wheat, ranging from 6 to 17 markers per chromosome. BLASTn of the source ESTs resulted in significant hits for 67 markers on the wheat pseudomolecules. Generally, COS markers of the same homeologous group were detected on similar arms in both Agropyron and wheat. However, some intragenomic duplications and chromosome rearrangements were detected in tetraploid A. cristatum. These results provide new insights into the structure and evolution of the tetraploid A. cristatum genome and will facilitate the exploitation of the wild species for introgression breeding of bread wheat. [ABSTRACT FROM AUTHOR]

Hybrid catfish (female Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus) fry are produced by hormone‐induced spawning of Channel Catfish in hatcheries. Anesthetics are used routinely to reduce handling stress by limiting the activation of the hypothalamic–pituitary–interrenal axis hormones. As a comparison, the present study determined the efficacy of electrosedation using a portable electrosedation system (PES) and its feasibility for possible application in hybrid catfish hatcheries. The PES was evaluated at 100 V and a 25% duty cycle at 30, 60, 90, or 100 Hz to anesthetize mature Channel Catfish to stage IV of sedation. The PES was compared to the chemical sedatives tricaine methanesulfonate (MS‐222; 200 mg/L) and metomidate hydrochloride (Aquacalm; 6 mg/L). The PES at 30 Hz anesthetized Channel Catfish in 4 s, significantly faster than the 120 s needed for MS‐222. However, the mean (±SE) time to recover from anesthesia and mean plasma cortisol response were similar (P > 0.05) with MS‐222 (104 ± 9 s; 35 ng/mL) and the PES (119 ± 15 s; 32 ng/mL). Relative fecundity of fish sedated by the PES and MS‐222 averaged 5,222 and 5,593 eggs/kg of body weight (BW), respectively; percent hatch averaged 46.9% and 50.4%, respectively; and hybrid catfish fry production averaged 1,644 and 1,711 fry/kg BW, respectively. Relative fecundity, percent hatch, and hybrid fry production were not significantly different between the PES and MS‐222 groups (P > 0.05). No internal injuries were noted in any of the fish subjected to electrosedation. The PES at 30 Hz effectively anesthetized female Channel Catfish with a quicker induction time, provided moderate time to recover from anesthesia, and elicited a cortisol response, with no known internal injuries. The results suggest that the PES has the potential to replace MS‐222 usage in hybrid catfish hatcheries. The PES is environmentally safe, does not expire or degrade, and requires no disposal or withdrawal period. [ABSTRACT FROM AUTHOR]

The gonadosomatic index (GSI) and fecundity of the threatened Cirrhinus reba (Hamilton) was studied over a period of one year from January to December 2015 in the Ganges River (northwest Bangladesh). The GSI index indicated that the C. reba breeding season in the Ganges was from June to September with the peak in August. Fish fecundity increased with increasing fish length and weight, and the highest fecundity (265,042.23) was recorded in a fish with a total length, a body weight, and an ovary weight of 23.80 cm, 136.00 g and 45.00 g, respectively. There was a linear relationship between fecundity and total length (r = 0.871), body weight (r = 0.872), and ovary weight (r = 0.879), with that between ovary weight and fecundity being the strongest. [ABSTRACT FROM AUTHOR]

This study was an attempt to understand the exploitation rate and mortality parameters of Trichiurus lepturus Linnaeus, 1758 for sustainable exploitation and conservation of this important fish species in Ogun coastal waters, Nigeria. Reproductive biology, trophodynamics and stock structure of the population was assessed from ribbonfish captured with graded gillnets (18, 22, 26, 30, 40, 45, 50, 65, 70, 75, 80 and 90 mm, knot-to-knot). A total of 1,616 individuals of T. lepturus were captured and subjected to descriptive and inferential statistical tools. Sex ratio of males: females (0.4:1) was significantly (x2=32.144; p=0.0007) different from unity. Peak spawning seasons were December and July. Total fecundity ranged between 7,051 and 12,456 eggs·yr-1. In stomach contents, juveniles of ribbonfish dominated the finfish group with an index of relative importance (IRI) value of 42.6%, while Penaeids occurred most in the shellfish group with IRI value of 17.3%. Feeding intensity showed that juveniles fed mostly on prawns and crustaceans while adults fed more on finfishes. T. lepturus exhibited positive allometric growth with modal classes of 35-36.9 and 45-46.9 cm; von Bertallanfy model gave an asymptotic-length (L∞) of 69.3 cm. Exploitation rate of T. lepturus is 0.73, which indicates that the stock of T. lepturus is marginally over-exploited. [ABSTRACT FROM AUTHOR]

Abstract The reproductive performance of farmed Arctic charr exhibits substantial individual variation. The causes behind this variation have not yet been properly explained, despite the species relatively long history in aquaculture. The aim of the present study was to provide better understanding of the issue by evaluating parent and gamete traits in relation to fertility and offspring viability under routine hatchery conditions. Are losses mainly due to failed fertilisation or mortality? Are maternal or paternal factor more predominant? The study covered sex hormone status of the broodstock, egg traits (egg size and wateriness of egg batches), milt traits (volume, density, and sperm motility characteristics), and symmetry of early cell division. We found that the majority of offspring loss occurred as embryo mortality, although a significant additional loss could be assigned fertilisation failure. Fertilisation and mortality rates were not inter-correlated. Neither of the evaluated egg traits, egg size and wateriness of newly stripped egg batches, proved to be useful indicators of egg quality. With regard to sperm traits, milt density as well as several computer assisted sperm analysis (CASA) parameters, i.e. swimming speed (VAP, VSL, and VCL) and beat cross frequency (BCF), were correlated with reproductive performance and could potentially be used as quality indicators for Arctic charr. Together, male 17,20β-P levels and BCF explained 69.5% of the between male variation in proportion of successfully eyed eggs. The results support previous indications that post-ovulatory aging of oocytes is contributing to the impairment of reproductive performance in farmed Arctic charr. In addition, a significant paternal factor to this impairment has been exposed. However, the cause and mechanism involved are still far from clear. Highlights • Broodstock and gamete traits were evaluated together with fertility and embryo viability under routine hatchery conditions. • Embryo mortality, rather than failed fertilisation, was the main cause for egg loss in the studied Arctic charr broodstock. • Besides post-ovulatory aging of oocytes, paternal fertility issues, which needs to be investigated further, were revealed. [ABSTRACT FROM AUTHOR]

Early stages from fertilized eggs to juveniles are important in the existence and development cycles of fish. At these stages, fish are still not fully developed, and are thus easily affected by environmental factors. Vietnam has a rich fish diversity, with ca 3000 species, and fishery resources play significantly roles not only in the daily lives of local residents but also in national economic development. Ichthyological studies in Vietnam have focused mainly on matured fish while early life history has so far been less researched. This paper presents an overview of studies in Vietnam related to early stages of fish and provides an orientation for this field in future. [ABSTRACT FROM AUTHOR]

This study evaluated the annual cycle of biological reproductive aspects of Prochilodus lacustris, a neotropical fish species, in Baixada Maranhense Protection Area in northeastern Brazil. Fish were collected monthly between June of 2015 and June of 2016 using gill nets. In the laboratory, 600 individuals were weighed, measured, and eviscerated to obtain biometric data and data for the microscopic and macroscopic analyses of the maturation stages of the gonads. These analyses allowed the determination of the reproductive period using biological indicators such as the gonadosomatic index and hepatosomatic index, condition factor, stomach repletion index, and spawning season. Abiotic variables were measured in situ during the samplig: temperature, pH, dissolved oxygen, and electrical conductivity. In addition, local rainfall data was also obtained. The results showed that the total body length of individuals varied from 151 to 211 mm in males, and from 142 to 239 mm in females. The sex ratio showed a predominance of females over males, and the species showed negative allometric growth. The annual variation of reproductive indicators and the frequency of individuals in advanced stages of gonadal maturation suggest that the reproductive cycle of the species occurs between November and January, with a reproductive peak in January. This reproductive peak coincides with the beginning of the region's rainy season. Although we did not do the fertility analysis, our results suggest that the species presents partitioned spawning. In conclusion, this results demonstrates that the reproduction of the investigated specie is influenced by associations between environmental variables on a seasonal scale and can be contribute to improve the understanding of the dynamics of the physiological reproductive process in lentic environments. [ABSTRACT FROM AUTHOR]

Fecundity estimates are important in fisheries management to determine the reproductive potential and spawning stock biomass of a population. Traditional methods for determining these estimates, however, have been time consuming and tedious, often requiring long‐term sample storage in toxic preservatives. Recently, studies incorporated the use of scanners and image analysis software to produce equally reliable fish fecundity estimates. This study was undertaken to demonstrate the application of this technique with Alewife Alosa pseudoharengus, "a species of concern." Ovaries were collected from fish ranging in size from 25 to 34 cm throughout their annual spawning migration (Newmarket, New Hampshire) and used to compare fecundity estimated gravimetrically following long‐term storage and by use of a flatbed scanner. Gonadosomatic indices were calculated throughout the collection period but were not found to differ over time. Comparisons within ovaries demonstrated that oocyte size and number did not differ among anterior, center, and posterior sections. Fecundity estimates did not differ between the two methods and increased with fish age and size ranging from 121,000 and 130,200 oocytes/female (25 cm) to 332,500 and 364,900 oocytes/females (34 cm), respectively. These results demonstrate that fecundity estimates using digital image analysis software were equally reliable as those produced by traditional methods but were generated more quickly and with less reliance on toxic preservatives. [ABSTRACT FROM AUTHOR]

Abstract This study was conducted to determine the effect of turmeric powder dietary supplementation on the histology of visceral organs and reproductive performance of Pseudotropheus acei. The fish were fed dietary additions of 0%, 1%, 3%, 5%, and 7% turmeric powder. Each treatment was replicated three times. There were one male and four female fish with a mean weight of 6 g in each replicate. The fish were fed ad libitum for 90 days. There were no differences in fertility rate, fecundity rate, hatching rate, egg diameter, and larvae survival rate among groups (P < 0.05). Ovulation frequency and the percent of spawning broodstock were less in the 7% and 5% turmeric-supplemented group (P < 0.05), while there were no effects of treatment in the 1%, and 3% groups compared with the control group. Observations in histopathological examinations indicated there were normal tissue structures in the control, 1% and 3% turmeric-supplemented groups, while the addition of 5% and 7% turmeric induced a degeneration of and decrease in number of observable ovarian follicles. In addition, there was a normal liver structure in the control and the 1% and 3% turmeric-supplemented groups and slight to severe lipidosis in the 5% and 7% turmeric-supplemented groups. Also, the supplementation of larger amounts of turmeric induced enteritis and the slight to severe side effects on the relevant organs. These results indicate that supplementing of diets with turmeric powder in amounts of 5% and 7% suppressed ovarian follicle development, and extended periods between times of spawning which resulted in subfertility of broodstocks. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine fertility of spiny-cheek crayfish harvested in the first half of April from the Vistula Lagoon and to compare it with that of the crayfish from freshwater habitats. The sample consisted of 47 sexually mature females shortly before they were ready to lay eggs. After determining the absolute fertility (number of eggs per ovary), the relative fertility was calculated (number of eggs per 1 g of body weight). Absolute and relative fertility of spiny-cheek crayfish females with total body length 8.1-11.6 cm was 535 and 17 eggs, respectively. Absolute and relative fertility was correlated with total body length and weight. Along with the increase in these parameters, the absolute fertility increased and the relative fertility decreased. A comparison of absolute and relative fertility of spiny-cheek crayfish from the Vistula Lagoon with the representatives of this species from freshwater habitats such as the Brda River and the Lake Dgał Wielki, showed no significant differences. [ABSTRACT FROM AUTHOR]

Boops boops sexuality was studied in 664 females, 201 males, and 103 hermaphrodites collected from central Algerian coast ports between December 2013 and November 2014. Histoanatomical observations were performed to describe the sexual pattern of B. boops. Observation of the evolution of sexual maturity stages as well as the gonadosomatic report have established the breeding period of B. boops as between February and June. The B. boops population fished here is in favor of females, with a percentage of 76.76% against 23.34% for males. Thus, the female to male ratio (F:M) of the sample was calculated as 1:3.3. According to the monthly value of hepatosomatic index, the bogue seems to store its reserves in the liver. The condition factor did not significantly fluctuate. The size at first sexual maturity for both sexes was determined as 14.74 cm total length. Fecundity was studied by the volumetric method in 149 mature females of between 13.9 and 29.4 cm in total length. Absolute fecundity varied between 36,600 and 445,200 oocytes per female. The average relative fecundity was 1 565 ± 228 oocytes per gram of body weight. [ABSTRACT FROM AUTHOR]

Genome editing technology is becoming increasingly accepted as a way to improve traits in marine fish aquaculture. In fish, microinjection is a major method for introducing RNA or protein into eggs for genome editing; however, this method has not yet been established in aquaculture fish. We successfully established microinjection methods achieving high survival rates for tiger pufferfish and red sea bream by optimizing the following three parameters: (1) the soaking solution of fertilized eggs during microinjection, (2) the elapsed time from in vitro fertilization to microinjection, (3) the elapsed time from stripping to microinjection. In tiger pufferfish, Iwamatsu solution or diluted sea water is effective as the soaking solution. In vitro fertilization can be performed at intervals of 15 min from fertilization until 2.5 h after stripping. Similarly, in red sea bream, Leibovitz's L-15 medium or Iwamatsu solution is effective as the soaking solution and in vitro fertilization can be performed at intervals of 10 min from fertilization until 2.5 h after stripping. We anticipate our findings will contribute to effectively establish genome edited aquaculture breeds. [ABSTRACT FROM AUTHOR]

Abstract Bisphenol A (BPA) in eggs prior to fertilization was found to induce long-term metabolic disturbances in juvenile rainbow trout (Oncorhynchus mykiss). Here we describe these imprinting effects in a Dynamic Energy Budget (DEB) framework, which allows interpretation of the data in an energy allocation context. First, DEB parameters for control rainbow trout were optimized using data extracted from 12 studies in the literature. Several modes of action on DEB parameters were then tested in order to correctly predict weight differences observed in rainbow trout in response to 5 different concentrations of BPA in eggs prior to fertilization. Reduced energy conductance v ̇ at day 0, followed by an exponential recovery, was found to closely fit the experimental data. Effects on v ̇ lasted beyond the disappearance of the chemical from the body, suggesting an imprinting effect of BPA on energy mobilization from the reserve. Our model predicts that early changes in DEB parameters lead to permanent and irreversible impairment of the metabolic growth acceleration in rainbow trout. Highlights • A control DEB model was obtained for rainbow trout using data extracted from 12 studies. • Mode of action of BPA exposure prior fertilization was investigated at 5 different concentrations. • BPA imprints DEB parameters long after being cleared from the animal. • Impaired DEB parameters at early life stages lead to irreversible changes related to acceleration factor. [ABSTRACT FROM AUTHOR]

The life histories of species influence the connectivity between populations, for example the dispersal potential, fecundity, and population size. We compare the phylogeography and genetic connectivity of two sandy-beach crustaceans with contrasting dispersal potentials and population traits in Brazil, based on the 16S mitochondrial gene. While the ghost crab Ocypode quadrata possesses high fecundity, long-lived planktonic larvae, and lower population densities of adults, the isopod Excirolana braziliensis is a brooder with low fecundity and higher population densities. Phylogenetic analysis of haplotype networks yielded contrasting results for the two species. Four different lineages were observed for E. braziliensis, while O. quadrata showed a low genetic structure, sharing haplotypes over ~ 7,000 km. For the isopod, the two most frequent lineages (‘North A’ and ‘South A’ lineages) showed distribution range limits that agreed with the tropical-subtropical transition of 22°S, while the others were sympatric, less frequent, and uncommon. While the ‘North A’ showed high haplotype diversity with a high structure, the ‘South A’ showed shared haplotypes and low genetic structure. Our results suggest that the contrasting life histories affect the population connectivity and genetic structure. The genetic patterns of the two species should be considered in the management and conservation of sandy-beach ecosystems. [ABSTRACT FROM AUTHOR]

Seasonal environments favor the evolution of capital breeding, whereby reproduction uses surplus energy from resources acquired during an earlier period. Consequently, reproductive effort in capital breeders is expected to depend on traits associated with energy storage rather than environmental conditions at the time of reproduction. Based on a 15-year dataset, we investigate the effect of phenotype (body size and condition) and environmental conditions (intensity of hydrological seasons, predator density, and density of conspecifics) on fecundity three capital breeding fish species from the strongly seasonal Amazon River floodplain: Psectrogaster rutiloides, Triportheus angulatus, and Acestrorhynchus falcirostris. Fecundity of all three species was strongly correlated with phenotype and modulated by unfavorable environmental conditions during the period of reproduction, especially high density of conspecifics. Fecundity was negatively affected by the density of conspecifics for small females of A. falcirostris, and for T. angulatus females with poor body condition. Fecundity of P. rutiloides declined during periods of drought when density of conspecifics was highest. A clear tradeoff between quantity and quality of oocytes was found only for P. rutiloides. This study highlights that reproductive allocation of capital breeders in seasonal environments is strongly linked to environmental conditions before and during the reproductive period. [ABSTRACT FROM AUTHOR]

The fish productivity from the reservoir in its all naturalness depends on various abiotic and biotic factors. The abiotic factors include mostly all physico-chemical parameters of water body, which have immense influence on biogenic factors and existence of flora and fauna in the reservoir. The first and foremost impact of physico-chemical parameters are experienced by the biotic community existing at the base of trophic level, which include the autotrophs like phytoplankton, which forms the very basic source of food material for the first order consumers like fishes who thrive on the pasture of phytoplankton. The physical factors like insolation, temperature, transparency had the direct impact on the existence of phytoplankton. The results obtained clearly indicates the existence of high bloom of plankton in the summer months owing to increased availability of radiant sun's energy (insolation), rise in temperature and high level of transparency accounting for the enhanced photosynthetic activity. The astonishingly high bloom phytoplankton at all the stations of the recording in the summer ensured the ample availability of food material for pelagic fishes. The length-weight measurement conducted for all the fishes from the reservoir evidently indicated the maximum gain of the growth of fishes during the summer months. The community, which derived the maximum advantage of high intensity of feeding on phytoplankton during the summer months resulting into enhanced growth, was mostly the carps (Indian major carps and minor carps) from the reservoir. The correlation of finding of fish fecundity in the reservoir to the conversion eggs into spawns at the rate of minimum 50%, it was estimated that there was addition of average number of over 20.0 Lakh from Catla catla; over 30.0 Lakh from Labeo rohita, over 20.0 Lakh of Cirrhinus mrigala, over 15.0 Lakh from Heteropneustes fossilis and Channa striatus, over 35.0 Lakh Labeo gonius. [ABSTRACT FROM AUTHOR]

Gynogenetic zebrafish Danio rerio were obtained by activating D. rerio oocytes with UV irradiated common carp Cyprinus carpio sperm and then applying one of four different shocks [two (early) meiotic and two (late) mitotic shocks]. Gynogens produced by three of the shocks survived to maturity. All adult gynogens (n = 52) except one were found to be male. There was no difference in growth rate between the biparental controls and gynogens produced through the most effective shock, thereby eliminating growth rate as a possible cause of the skewed sex ratio. Gynogen males had reduced fertility compared to biparental controls, with about half of gynogens being unable to reproduce through natural spawning (all controls reproduced successfully). Gynogen males that did reproduce gave lower fertilization rates compared with controls. This demonstrates the negative effects of increased homozygosity on male reproductive function. Families sired by meiotic gynogen males were more likely to be female biased (33% of families) compared with families sired by biparental control males (11%). In addition to confirming the polygenic nature of sex determination in D. rerio, these observations suggest that recessive or over‐dominant male‐determining alleles are present in domesticated D. rerio populations. [ABSTRACT FROM AUTHOR]

Maternal influences on age-0 walleye (Sander vitreus (Mitchill, 1818)) recruit abundance and survival from egg to fall were observed in Escanaba Lake, Wisconsin, in 1957–2015. Annual egg production best explained variation in age-0 recruitment, compared with female relative abundance, and adult abundance (sexes combined). Age-0 recruitment was not significantly correlated with any temperature metric tested or our index of yellow perch (Perca flavescens (Mitchill, 1814)) abundance. Survival of walleye from egg to fall age-0 was positively correlated with the percent contribution of large females (>55.9 cm) to annual egg production. Mean size diversity of females by length class did not influence age-0 recruit abundance or survival over time. Evidence for maternal effects via size- and age-specific influences on fecundity and age-0 walleye survival suggest that exploitation may influence natural recruitment by altering adult female size structure. Given recent declines observed in walleye natural recruitment in the upper Midwestern USA, understanding the roles of maternal drivers and exploitation on recruitment is critical for sustainable walleye management. [ABSTRACT FROM AUTHOR]

• An assay to assess inhibition of oocyte maturation was developed. • TBCO decreased fecundity of Japanese medaka. • TBCO impaired oocyte maturation, in vitro and ex vivo. • Impaired oocyte maturation is a mechanism of decreased fecundity of Japanese medaka exposed to TBCO. Inhibition of oocyte maturation is an understudied mechanism by which chemical stressors can impair fecundity of female fishes. The primary objective of the present study was to develop an assay to assess oocyte maturation disruption by chemical stressors in Japanese medaka (Oryzias latipes). First, an in vitro assay to assess maturation inducing hormone (MIH)-stimulated oocyte maturation in zebrafish was validated for use with Japanese medaka. Next, using the brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO), which previously was shown to decrease fecundity of Japanese medaka and inhibit oocyte maturation in zebrafish, effects on oocyte maturation were quantified using in vitro and in vivo exposure. Adaptation of the protocol for in vitro MIH-stimulated maturation of stage IV oocytes from zebrafish was successful in inducing greater than 80% of stage IX oocytes from female Japanese medaka to mature. To assess effects of in vitro exposure, stage IX oocytes were exposed to 0, 2, 20, and 200 μg/L of TBCO, followed by exposure to MIH. The in vitro exposure caused a significant decrease in maturation of oocytes exposed to 20 and 200 μg/L of TBCO. To assess effects of TBCO on fecundity and oocyte maturation following in vivo exposure, sexually mature fish were fed a control, 100 μg/g, or 1000 μg/g concentration of TBCO-spiked fish food for 21 days, where fecundity was measured daily, and following the exposure, stage IX oocytes were excised to assess MIH-stimulated maturation. Fecundity and oocyte maturation were significantly decreased at either concentration of TBCO. Plasma concentrations of 17β-estradiol (E2) and hepatic abundances of transcripts of vitellogenin (vtgI and vtgII) were quantified, but there were no significant differences between treatments. Results suggest that inhibition of oocyte maturation is a mechanism by which TBCO decreases fecundity, and that in vitro assays of oocyte maturation might be predictive of fecundity in this species. [ABSTRACT FROM AUTHOR]

The reproductive characteristics of Gymnocypris firmispinatus were determined from 582 individuals collected in the Anning River, China. The sex ratio (male: female) was 1:1 for the overall population but 3.1:1 for the mature group. Females reached a larger total length and total weight (242 mm and 148.17 g) than males (163 mm and 41.58 g). Lengths and ages at maturity were estimated to be 83.4 mm and 2.4 years for males, 130.7 mm and 5.9 years for females, respectively. Based on the analyses of gonad development and the size distribution of oocytes, G. firmispinatus spawned from March to May with high degree of the spawning synchronicity. The opposite tendency between gonado-somatic index and hepato-somatic index from January to March in females indicated that the energy requirement for the oocytes growth may be derived from the liver. In addition, the estimated mean fecundity and mean relative fecundity were 1227 and 29.7 eggs per g total weight. The fecundity of G. firmispinatus increased linearly with increasing of total length, total weight and ovary weight. This study provides details about the reproduction suggesting that G. firmispinatus might be especially vulnerable to exploitation in the Anning River. [ABSTRACT FROM AUTHOR]

The sexual maturity of the female swamp eel (Monopterus albus) was studied by determining its fecundity and gonadosomatic index (GSI). The body weight of a sexually mature female swamp eel was 200-250 g. The eggs were nonadhesive demersal and rounded. The maximum fecundity was in June at 701 ova/fish with a gonadosomatic index (GSI) of 3.09%. The minimum recorded fecundity was 181 ova/fish in October with a GSI of 0.57%. The average diameter of the eggs was 1,784 µm. The fish eggs were classified by diameter into seven groups: 250-750 µm (12.25%) as group 1, 751-1,250 µm (15.62%) as group 2, 1,251-1,750 µm (14.76%) as group 3, 1,751-2,250 µm (31.50%) as group 4, 2,251-2,750 µm (18.87%) as group 5, 2,751-3,250 µm (6%) as group 6, and 3,251-3,750 µm (1%) as group 7. Newly hatched larvae of the swamp eel were produced by the semi-control natural method. Newly hatched larvae had a mean (SD) total length (TL) of 1.76±0.06 cm with a mean (SD) yolk sac volume of 1,279.14±101.50 µm³. The yolk sacs were completely absorbed within 174 hours after hatching (hAH) at a water temperature of 28,0-30.5 °C. All larvae were able to open their mouths at 108 hAH (2.50±0.17 mm TL), with a mean (SD) height measurement of 785.00±30.83 µm. The digestive tract was straight, and was placed on the yolk sac. The digestive tracts were formed at 116 hAH with a mean (SD) length of 845.00±30.75 µm. The average number of Moina sp. in the digestive tract at the start of feeding was 0.83 individuals/larva. The larvae died within 1,092 hAH at water temperatures that ranged 27.0-30.5 °C. It was found that the feeding scheme of the larval swamp eel was as follows: larvae of age 5-15 days (total length 2.81-3.30 cm) consumed Moina sp., but at age 12-15 days (average total length 3.2-3.30 cm) the larvae consumed both Moina sp. and a commercial pellet known as 'power feed'. Larvae more than 16 days old (average total length 3.20 mm) consumed only 'power feed'. [ABSTRACT FROM AUTHOR]

The study on the reproductive biology of commercially important fish species in Lake Langeno, Ethiopia was conducted from March 2015 to February 2016. Fish samples were collected from different sampling sites by different mesh size of gillnets and long lines. A total of 4207 fish specimens were collected. The peak breeding time observed was April-June, May-July, June-July and March-May for Oreochromis niloticus (Linnaeus 1758), Clarias gariepinus (Burchell 1822), Labeobarbus intermedius (Rüppell 1835) and Cyprinus carpio Linnaeus 1758, respectively. Their respective L50 were 16.4 cm and 15.8 cm TL, 28.5 cm and 29.5 cm TL, 30.5 cm and 29.5 cm FL, and 28.2 cm and 27.6 cm FL for females and males, respectively. The mean fecundities of these fish species were 463.83 ± 114, 141466 ± 40982, 3055 ± 2234 and 105631 ± 46680 eggs.fish-1, respectively. The relationship between fecundity and total or/fork length were curvilinear for all fish species, while the relationship between fecundity and total weight were linear for O. niloticus, L. intermedius and C. carpio, and curvilinear for C. gariepinus (r² > 90). The result showed a significant temporal variation of GSI for all fish species (ANOVA, P < 0.05). It also showed the domination of small-sized fishes with the small L50 of most fishes. Therefore, effective management is needed to improve the situation of fishes in the lake. [ABSTRACT FROM AUTHOR]

Sexual ornaments found only in females are a rare occurrence in nature. One explanation for this is that female ornaments are costly to produce and maintain and, therefore, females must trade‐off resources related to reproduction to promote ornament expression. Here, we investigate whether a trade‐off exists between female ornamentation and fecundity in the sex‐role reversed, wide‐bodied pipefish, Stigmatopora nigra. We measured two components of the disk‐shaped, ventral‐striped female ornament, body width, and stripe thickness. After controlling for the influence of body size, we found no evidence of a cost of belly width or stripe thickness on female fecundity. Rather, females that have larger ornaments have higher fecundity and thus accurately advertise their reproductive value to males without incurring a cost to fecundity. We also investigated the relationship between female body size and egg size and found that larger females suffer a slight decrease in egg size and fecundity, although this decrease was independent of female ornamentation. More broadly, considered in light of similar findings in other taxa, lack of an apparent fecundity cost of ornamentation in female pipefish underscores the need to revisit theoretical assumptions concerning the evolution of female ornamentation. In the wide‐bodied pipefish, females attract males with enormous striped bellies. Do females suffer a cost to offspring production by producing such an elaborate ornament? Larger females have larger ornaments that honestly signal their fecundity to males. [ABSTRACT FROM AUTHOR]

The daubed shanny Leptoclinus maculatus is a relatively common fish species in Svalbard waters, but little is known about its reproduction. In total, 207 specimens (76 females, 131 males) were collected and examined. Gonadosomatic (GSI) and hepatosomatic indices were significantly higher in females (mean 2.8 and 2.7%, respectively) than males (mean 0.3 and 1.8%) in all seasons. The GSI of females was highest during autumn and winter (18.5%) while the GSI of males was highest in winter (1.7%). Females become sexually mature at 125 mm standard length (SL) and 7 years of age while males become sexually mature at similar length and 6 years of age. The number of oocytes in gonads increased with SL and age and comprised two groups: (1) 115-124 mm SL, 5-7 g gutted weight (GW) and 5-6 years of age with potential fecundity of 950-1850 oocytes, (2) 125-134 mm SL, 7-9 g GW and 7-12 years of age with 1250-2800 oocytes. The daubed shanny seems to spawn all its ripe oocytes during one spawning event each year. Fish become sexually dimorphic after maturation, and differences in sexual morphology are likely linked to reproduction, with female parental care and territorial defence for males. The reproductive strategy of daubed shanny is characterized by late maturation, relatively low fecundity and large size of offspring, i.e. large investment in relatively few offspring. [ABSTRACT FROM AUTHOR]

Abstract: A mismatch in synchrony between male and female gamete release in external fertilizers can result in reduced or failed fertilization, sperm competition, and reduced paternity. In Arctic charr (Salvelinus alpinus), males can adopt either a guard or sneak tactic resulting in both pre‐ and postcopulatory competition between males with alternative reproduction tactics. Here, spawning behavior of free‐living Arctic charr was video‐recorded, and their reproductive behavior was analyzed. From evaluating 157 spawning events, we observed that females mainly spawned with a guarding male and that the female and the guarding male synchronized timing of gamete release under sperm competition. Although sneakers spawned with higher synchrony than the guarding male in single‐male spawning events, the average sneaker released his milt less synchronized with the female than the guarding male under sperm competition. Approximately 50% of the recorded spawning events occurred under sperm competition, where each event included an average of 2.7 males. Additionally, sneakers were more exposed to sperm competition than guarding males. An influx of males, in close proximity to the female, occurred during the behavioral sequences leading up to egg release, but this influx seemed not dependent on egg release, suggesting that something else than gonadal product attracts sneaker males to the spawning female. Just before and during the actual release of gametes, the spawning couple vibrates their bodies in close contact and it seems likely that this vibrational communication between the spawning couple, which results in a larger amplitude sound wave than seen under regular courting, reveals time of gamete release to sneaker males. Thus, vibrational communication may enable synchrony between the guarding male and the female, and this might be traded against the cost of higher detectability from surrounding sneaker males, eavesdropping in close proximity. [ABSTRACT FROM AUTHOR]

Abstract: The pejerrey possesses a genotypic sex determination system driven by the amhy gene and yet shows marked temperature‐dependent sex determination. Sex‐reversed XY females have been found in a naturally breeding population established in Lake Kasumigaura, Japan. These females could mate with normal XY males and generate YY “supermale” individuals that, if viable and fertile, would sire only genotypic male offspring. This study was conducted to verify the viability, gender, and fertility of YY pejerrey and to develop a molecular method for their identification. Production of YY fish was attempted by crossing a thermally sex‐reversed XY female and an XY male, and rearing the progeny until sexual maturation. To identify the presumable YY individuals, we first conducted a PCR analysis using amhy‐specific primers to screen only amhy‐positive (XY and YY) fish. This screening showed that 60.6% of the progeny was amhy‐positive, which suggested the presence of YY fish. We then conducted a second screening by qPCR in order to identify the individuals with two amhy copies in their genome. This screening revealed 13 individuals, all males, with values twice higher than the other 30 amhy‐positive fishes, suggesting they have a YY complement. This assumption as well as the viability, fertility, and “supermale” nature of these individuals was confirmed in progeny tests with XX females that yielded 100% amhy‐positive offspring. These results demonstrate that qPCR can obviate progeny test as a means to identify the genotypic sex and therefore may be useful for the survey of all three possible genotypes in wild populations. [ABSTRACT FROM AUTHOR]

Fecundity of marine fish species is highly variable, but trade-offs between fecundity and egg quality have rarely been observed at the individual level. We investigated spatial differences in reproductive investment of individual European sprat Sprattus sprattus (Linnaeus 1758) females by determining batch fecundity, condition indices (somatic condition index and gonadosomatic index) as well as oocyte dry weight, protein content, lipid content, spawning batch energy content, and fatty acid composition. Sampling was conducted in five different spawning areas within the Baltic Sea between March and May 2012. Spawning sprat from the Kiel Bight were in a better nutritional condition compared to sprat from the Arkona Basin, Bornholm Basin, and the Gdansk Deep. These females were also producing up to twice as many oocytes, and invested significantly more energy in reproduction, than their counterparts sampled in the eastern part of the Baltic Sea. Still, oocytes produced by Kiel Bight sprat contained significantly lower fractions of the essential fatty acids 20:4 (n-6) and 22:6 (n-3). A seasonal trade-off between oocyte weight/lipid content and fecundity was found for Baltic sprat, albeit the gross energy invested into spawning remained constant. Observed spatial and seasonal differences in sprat reproductive investment may be linked to hydrographic conditions and food availability and will impact the survival probability of yolk-sac and first feeding larvae. These findings indicate that Baltic sprat is able to adapt its reproductive tactics to the highly variable pelagic habitat of the Baltic Sea. [ABSTRACT FROM AUTHOR]

Summary: This study explores the reproductive biology and the influence of environmental factors on the reproductive traits of Floridichthys polyommus inhabiting the estuary of the Champoton River. The analysis included population structure, gonadal developmental stages, reproductive period, size at first sexual maturity, fecundity, sex ratio, and somatic indexes. A spatio‐temporal pattern in the distribution of the seven size classes was detected. The species showed a positive allometric growth. Sex ratio was 1.21:1 (females:males). Size at first maturity was 42.23 mm (females) and 47.8 mm (males). A higher absolute and relative fecundity was detected in Puente Champotón estuary (PCH) with lower salinities than those detected in the Delta (DE). The adaptive significance of this trait could be in response to the heavy osmotic constraint imposed by extreme salinities in the DE. Floridichthys polyommus prefers PCH for spawning, and as a result a higher number of ripe individuals was observed in this site, characterized by the highest nutrient levels, which can boost productivity and food availability for fish. Hepatosomatic index was negatively correlated with gonadosomatic index, suggesting energy transfer from the liver towards gamete production. Floridichthys polyommus exhibits an opportunistic strategy (early maturity, small oocytes, small clutches) suggesting that energy is allocated towards reproduction to compensate for the unpredictable hydrological conditions imposed by the estuary (particularly during the hurricane season). Floridichthys polyommus shows a reproductive strategy exhibited by fish living in unstable systems. A seasonal divergence was observed in the reproductive traits of F. polyommus, while differences between study sites were for fecundity. [ABSTRACT FROM AUTHOR]

The present hypothesis on reproductive migration pattern between two species of sciaenids is based on the data collected with the help of the single-day commercial trawl with a fishing effort of 181 h along the fishing grounds of Goa, west coast of India. The observations on abundance revealed that between the two species (Johnius borneensis and Otolithes ruber) that formed bulk of the catch, a significant inverse trend in catch was observed. The pattern of migration based on the examination of female gonadal status suggested J. borneensis to be a continuous spawner and was evidenced by continuous occurrence of gravid and spent females and their juveniles. On the other hand, the rare occurrences of gravid females of O. ruber from the study area suggest that the species spawns away from the coast or might migrate to some potential spawning grounds. Further, an assessment of fecundity and the ova distribution pattern propounded higher fecundity in O. ruber compared to J. borneensis with multiple spawning in both the species. [ABSTRACT FROM AUTHOR]

Abstract: In addition to genetic variation, epigenetic mechanisms such as DNA methylation might make important contributions to heritable phenotypic diversity in populations. However, it is often difficult to disentangle the contributions of genetic and epigenetic variation to phenotypic diversity. Here, we investigated global DNA methylation and mRNA expression of the methylation‐associated enzymes during embryonic development and in adult tissues of one natural isogenic lineage of mangrove rivulus fish, Kryptolebias marmoratus. Being the best‐known self‐fertilizing hermaphroditic vertebrate affords the opportunity to work with genetically identical individuals to examine, explicitly, the phenotypic effects of epigenetic variance. Using the LUminometric Methylation Assay (LUMA), we described variable global DNA methylation at CpG sites in adult tissues, which differed significantly between hermaphrodite ovotestes and male testes (79.6% and 87.2%, respectively). After fertilization, an immediate decrease in DNA methylation occurred to 15.8% in gastrula followed by re‐establishment to 70.0% by stage 26 (liver formation). Compared to zebrafish, at the same embryonic stages, this reprogramming event seems later, deeper, and longer. Furthermore, genes putatively encoding DNA methyltransferases (DNMTs), Ten‐Eleven Translocation (TET), and MeCP2 proteins showed specific regulation in adult gonad and brain, and also during early embryogenesis. Their conserved domains and expression profiles suggest that these proteins play important roles during reproduction and development. This study raises questions about mangrove rivulus’ peculiar reprogramming period in terms of epigenetic transmission and physiological adaptation of individuals to highly variable environments. In accordance with the general‐purpose genotype model, epigenetic mechanisms might allow for the expression of diverse phenotypes among genetically identical individuals. Such phenotypes might help to overcome environmental challenges, making the mangrove rivulus a valuable vertebrate model for ecological epigenetic studies. The mangrove rivulus, Kryptolebias marmoratus, is the best‐known self‐fertilizing hermaphroditic vertebrate that allows to work with genetically identical individuals to examine, explicitly, the phenotypic effects of epigenetic variance. The reprogramming event is later, more dramatic and longer than in other described vertebrates. High evolutionary conservation and expression patterns of DNMT, TET, and MeCP2 proteins in K. marmoratus suggest biological roles for each member in gametogenesis and development. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study was to investigate the reproductive ability of second generation (F2) koi (Cyprinus carpio L.) × goldfish (Carassius auratus L.) hybrids. Only diploid F2 males and females were fertile and used in crosses. A significant increase was recorded in male fertility in F2 versus F1. In contrast with an earlier study in which only one fertile F1 male was found, about 20% of F2 males produced sperm. The observed reproductive ability of F2 hybrids was similar to that demonstrated by the only fertile F1 male and F1 females. F2 males produced diploid spermatozoa and generated triploids when crossed with koi females. All triploid fish in these progenies were males indicating that F2 males had a sex chromosome constitution of XY. F2 females produced diploid eggs and generated mostly triploids when crossed with koi males. In progenies obtained by crosses of F2 males with F1 and F2 females, most of the surviving juveniles (63%–100%) were diploid; a minority of juveniles were aneuploid (ploidy ranged from 2.1n to 3.6n). Diploid fish in these progenies were presumably the result of spontaneous androgenesis and gynogenesis, by the same mechanisms observed earlier in progenies obtained by crossing the F1 male with F1 females. [ABSTRACT FROM AUTHOR]

Although the majority of studies on mate choice focus on female mate choice, there is growing recognition of the role of male mate choice too. Male mate choice is tightly linked to 2 other phenomena: female competition for males and ornamentation in females. In the current article, I review the existing literature on this in a group of fishes, Poeciliidae. In this group, male mate choice appears to be based on differences in female quality, especially female size, which is a proxy for fecundity. Some males also have to choose between heterospecific and conspecific females in the unusual mating system of the Amazon molly. In this case, they typically show a preference for conspecific females. Whereas male mate choice is relatively well documented for this family, female ornamentation and female competition are not. [ABSTRACT FROM AUTHOR]

Much of my career has been focussed on exploring the causes and consequences of variation in the productivity of fish. The aim has been to provide better advice for fisheries management. We have realized that variation in the components of productivity, such as growth, maturation, and fecundity is substantial. Incorporating this variation into stock assessment leads to a significant change in the perception of reference points and stock status. If exploitation levels are not adjusted for varying productivity, they will not be sustainable. Although we have learned much about the causes and consequences of variation in productivity there is still much to learn. It will be a huge leap forward when we can explain the processes driving this variation and use this information in our population models. My contributions to the field have benefitted greatly from a series of collaborations that have fuelled my creativity, productivity and enjoyment. My direct involvement in stock assessment has resulted in my research being used directly in the provision of scientific advice and also opened up areas of research that I would not have otherwise pursued. Get involved. Be open to new opportunities and seize them. You never know where they will lead you! [ABSTRACT FROM AUTHOR]

Fish samples of Indian hill trout Barilius bendelisis, were collected from the Gaula river (29° 17' 25'' N Latitude, 79° 32' 143'' E) and reared in captive condition at Directorate of Coldwater Fisheries Research, Bhimtal (29°21´ N, 79034´ E, altitude 1370 m MSL).Gonadosomatic index was found maximum in May for females (13.24 ± 0.92) and males (1.13 ± 0.07) respectively indicating a single spawning period of this species under captivity. Absolute fecundity (total number of eggs) varied from 320 to 4000. The average absolute fecundity was 1661 ± 304.6 at a total length 10.07 ± 0.30 cm and body weight of 11.92 ± 1.23 g. Histological study of the ovary revealed the presence of oocytes at different stages of maturity with a maximum number of the mature oocytes during April to May. Results of the present investigation suggest that B. bendelisis belongs to a category of low fecund fish and spawns during April and May under captive condition [ABSTRACT FROM AUTHOR]

The disappearance of larger individuals and the decrease in individual body condition suffered by Atlantic cod Gadus morhua in the eastern Baltic during the past two decades can be expected to affect the stock reproductive output. To investigate this, female G. morhua were collected during the spawning and pre‐spawning period in 2015−2016. The current individual potential fecundity (FP) of eastern Baltic G. morhua was estimated and analysed in relation to total length (LT) and indices of nutritional status such as body condition (K) and hepato‐somatic index (IH) using generalized linear models. In addition, the current prevalence of atresia and its potential relation to K were investigated. Moreover, a calibration curve to estimate FP from oocyte diameter, based on the autodiametric oocyte counting method, was established for the first time for eastern Baltic G. morhua and can be used for future fecundity studies on this stock. The results showed that FP was mainly positively related to fish length, but K and IH also contributed significantly to the variation in FP. The model predicted that fish with K = 1·2 have a FP 51% higher than fish of the same LT with K = 0·8. The prevalence of fecundity regulation by atresia was 5·8%, but it was found only in fish in the pre‐spawning maturity stage and with low K. Temporal changes in biological features such as the length composition and individual body condition of eastern Baltic G. morhua, should be accounted for when estimating stock reproductive potential. [ABSTRACT FROM AUTHOR]

Features of oogenesis, ovarian maturity phases and fecundity of the smooth lumpsucker (Aptocyclus ventricosus) are described here for the first time. Gonadal development was examined by histological methods and the morphological features and size of germ cells at various stages was determined. These features were used to more accurately define morphological criteria of 7 histological and macroscopic maturity phases. The smooth lumpsucker is an iteroparous gonochoristic species with determinate fecundity, group-synchronous ovary organization, total spawning (release of 1 batch of eggs per breeding season), and external fertilization. [ABSTRACT FROM AUTHOR]

This study presents data and estimates reproductive parameters of the sailfish Istiophorus platypterus (Shaw, 1792) in the western Atlantic, useful for future stock assessments of the species in the Atlantic Ocean. During the period 2006-2011, a total of 1132 fish were sampled by scientific observers on board Venezuelan and Brazilian longline vessels and from artisanal fisheries based out of Cumaná, Puerto La Cruz and Playa Verde, Venezuela and Cabo Frio, Rio de Janeiro, Brazil. The ovaries of 543 females were classified into five ovarian development phases based on microscopic analysis of the most advanced group of oocytes. Generalized additive models were applied to the gonadal index and sex ratio data in order to assess spatio-temporal trends of the reproductive activity and identify the spawning areas. Space-time effect was a significant factor contributing to changes in sex ratio and reproductive activity. Spawning activity was observed in two distinct areas. On the south-east Brazilian coast spawning peaked during December-February, while in the south-eastern Caribbean Sea spawning occurred between March and September, with its peak in March and April. Using a Bayesian approach, size at 50% maturity was estimated to be 146.12 cm (credibility interval of 95%, 138.45-152.09 cm). Batch fecundity ranged from 436,800 to 2,492,500 hydrated oocytes per female. This study confirms multiple aggregation spawning for this species in the western Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Reproductive biology of gray-eel catfish, Plotosus canius was studied at Pattani Bay by determining its year round changes of gonadosomatic index (GSI). Results show that the GSI was maximum in October (8.4 %), and minimum in April (0.24 %). The sampled size of sexually matured female fishes ranged from 40.9 to 60.5 cm in total length, and between 367.56 to 1,159.37 g in body weight. The average total length of the female fish is 51.9 cm, with an average body weight of 788.8 g. The average fecundity was 1,842.14 egg/fish. The average GSI was 10.87 % (n=14).The fish total length (TL) and body weight (BW) of the matured fish were linearly related, and could be represented by the linear regression as: BW = 32.295 TL - 887.52. The relationship between body weight (BW) and fecundity (Fe) could also be represented by the linear regression as Fe = 398.67+1.83BW. The eggs were adhesive demersal egg type, and rounded. The distribution of egg's diameter could be categorized into five groups i.e. group1 (3.3%), group2 (6.9%), group3 (11.0%), group4 (54.1 %), and group5 (24.6 %), with values of 2.89± 0.19 mm, 3.44±0.36 mm, 4.65±0.28 mm, 5.65±0.26 mm, and 6.38±0.25 mm respectively. The spawning ground is made of silty clay soil, with sediment's pH of 7.16±0.47and water salinity of 12.06 ± 0.78 ppt. We also found that the sperms activity was most active in the 0.9 % sodium chloride's concentration level. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the L-lysine effect in silver catfish, Rhamdia voulezi female reproduction. Four hundred fish were used distributed in a random in 16 net cages (25 fish each x 4 replicates = 100 fish per treatment). The treatments consisted in four diets, isoproteic and isoenergetic (30% crude protein and 3,500 kcal kg-1 digestible energy) with different L-lysine levels: T1: 1.30; T2: 1.40; T3: 1.60 and T4: 1.95%. After 185 days of experiment 18 females per treatment were weighed, measured, and submitted to hormonal induction (0.5 and 5.0 mg kg-1 Carp Pituitary Extract). The females were then sacrificed and had their ovaries, liver and fat removed and the respective organosomatic indices were estimated. With regard to the reproductive parameters, the released oocytes, absolute fecundity and remaining ovaries were influenced (P < 0.05) by the diet, and the highest mean values were observed in the treatment with 1.95% L-lysine. Among the organosomatic indices, only the visceral fat was influenced (P < 0.05). The estradiol levels and the composition of essential amino acid in oocytes were not affected (P > 0.05). We can conclude that L-lysine affects the reproductive parameters and accumulation of visceral fat in R. voulezi. [ABSTRACT FROM AUTHOR]

Investigation of fecundity and gonado somatic index (GSI) of Rastrelliger kanagurta were carried out from March 2011 to February 2012. Fecundity was determined at different length, weight and ovary ranges of different individual fishes. Study revealed that at 5% significant level significant average absolute fecundity was found to be 1,08,266 and relative fecundity ranged from 407 to 1499. The number of ova generally increased with increase in length and weight. However, variations in fecundity with respect to length and weight were also noticed. The gonado- somatic index (GSI) was calculated for each individual fish (592 numbers) and was averaged for each month. The average GSI values were plotted against each month to analysed monthly variations. GSI showed wide variations between sex and it was highest for both males and females during the month of April and September, showing occurrence of more ripe individuals. Analysis of regression showed that there were significant relationship between the fecundity with the fish length, body weight and ovary weight. [ABSTRACT FROM AUTHOR]

Abstract: Sexual selection should favour females that can assess the functional fertility of available sexual partners and avoid mating with recently mated, sperm‐depleted males. Our current understanding of the sensory mechanism(s) underlying female assessment of males based on their functional fertility and avoidance of sperm‐depleted males is incomplete. Female Trinidadian guppies (Poecilia reticulata) are known to avoid mating with males that they had previously observed mating with other females. Here, we investigated experimentally the proximate sensory cues that they use to distinguish between paired size‐ and colour‐matched mated and unmated males in the absence of visual public information on their prior mating histories. When only water‐borne chemical cues from the males were available, females avoided the previously mated male and preferred the unmated one, but they chose randomly when only male visual cues (and no chemical cues) were available. They also preferred unmated over mated males when freely swimming with them in a more sensorially complex environment with multiple male cues (i.e., visual, chemical and mechanical cues) concurrently available. Females exhibited no preference for either stimulus males when both were unmated, irrespectively of the sensory environment. These novel results suggest that, in the absence of prior visual public information on the recent mating histories of males, female guppies use olfactory cues putatively emitted by mated males to avoid mating with them. The source and nature of the implicated olfactory cues and the fitness benefits gained by female guppies in sexually preferring males that have not recently mated remain unknown and warrant further research. [ABSTRACT FROM AUTHOR]

Abstracts Ultrastructure and development of spermatozoa in cobia, Rachycentron canadum are described. Sections through the testis show different developmental stages viz, Spermatocytes, spermatids and sperm. Spermatozoa of R. canadum exhibit the configuration of uniflagellated, anacrosomal Type I aquasperm, typical for externally fertilizing fish. Mature spermatozoon is seen with a prominent head and long cylindrical flagellum. Ultrastructure of sperm shows invaginated ‘U’ shaped nucleus and other organelles. The mitochondrial matrix is electron-dense with irregular arrangement of the cristae. The nucleus reveals a deep invagination (nuclear fossa) in which the centriolar complex is located. The centriolar complex lies inside the nuclear fossa and is composed of a proximal and a distal centriole. The two centrioles are placed perpendicular to each other. The flagellum has a typical eukaryotic organization (microtubule doublets 9 + 2 pattern) and measures around 36.21 ± 0.42 μm in length. This study for the first time provides a comprehensive detail on the ultrastructure and developmental process of sperm in cobia, R. canadum . [ABSTRACT FROM AUTHOR]

Abstract: Ramshorn snail (Helisoma anceps) is a freshwater gastropod found all over North America and is also an essential component to the larval and juvenile culture of endangered Delta Smelt (Hypomesus transpacificus) at the UC Davis Fish Conservation and Culture Lab (FCCL). H. anceps has been proven effective in cleaning the excess algae while not harming the larvae. A challenge at the FCCL has been having a reliable source of these snails, since previously it has been dependent upon nature and never guaranteed there would be enough to meet the needs of the FCCL. Experiments were conducted to assess the effects of temperature, food types, rearing density and total ammonia nitrogen (TAN) concentrations. Procedures recommended to increase snail fecundity for the FCCL are to rear spawning parent snails and the resultant eggs at a high temperature (16–20°C) and with a low TAN concentration (0–5 mg/L). Newly hatched snails need to be cultured at a low density (about one snail/20 cm2). After the snails grow to an acceptable size (1.3 cm diameter), they could be set aside and cultured in an environment with less optimal water quality parameters such as a high TAN level (as high as 20 mg/L) and low temperature (12°C) for quantity control prior to use. [ABSTRACT FROM AUTHOR]