Gonadosomatic Research Articles

Spatial and temporal patterns of gonadal maturation and spawning in European flounder Platichthys flesus at its southern continental edge

The European flounder (Platichthys flesus) is a marine flatfish with high plasticity in several life-history traits, including spawning sites and habitat use patterns. With the overarching goal of understanding the use of estuaries in connection with maturation and reproduction in adult flounder, this study investigates its reproductive cycle in the Douro Estuary (NW Portugal), at the southern edge of its geographical distribution. Adults were caught by monthly trawling from November 2016 to November 2017. Sex ratio and length-weight relationships were determined. The annual reproductive cycle was described using a combination of gonadosomatic (GSI), hepatosomatic (HSI), and general fish condition (Kn) indices, seasonal gonad development staging (macroscopic and histological), and quantification of plasma sexual steroids. Total sex ratio was 1 M:3 F, and females presented negative allometric growth, while males’ growth was isometric. The various indices consistently indicated that the greatest reproductive activity occurred between January and March, peaking in February. However, some females at advanced reproductive stages (late vitellogenesis), high GSI values and steroid hormone (E2) levels were observed as late as May. Females in spawning condition, i.e., undergoing full oocyte maturation and ovulation, were never found, unlike males who exhibited spermiation within the estuary. Sexual differences in migration patterns were also suggested: males seem to leave earlier and stay longer in offshore spawning grounds, while females return to the estuary shortly after spawning. Overall, there was a good correlation between GSI, seasonal hormone cycling, and sexual maturity of female and male flounder, supporting the use of circulating sex steroids as a less invasive tool to assess maturity status.

Assessing the ovarian development of Macrobrachium amazonicum (Heller, 1862) phenotypes by means of an integrative analysis

Macrobrachium amazonicum is a species of economic interest with a wide distribution in the Americas and high morphological and reproductive variability. Three phenotypes can be observed in this species: i) large-size amphidromous, ii) large-size and iii) small-size hololimnetic prawns. In the present work, the morphological, histochemical and ultrastructural aspects of ovarian development in the three phenotypes were comparatively analyzed. In addition, the interaction between the ovary and the hepatopancreas was investigated in these phenotypes through the use of gonadosomatic (GSI) and hepatosomatic (HSI) indices. Despite the morphological differences and different reproductive strategies adopted by the females, the macroscopic, histochemical and ultrastructural patterns of ovarian development showed no differences between the phenotypes. The ovaries were macroscopically classified into five stages of development (I to V). In early stages (I and II), the ovaries are full of oogonia, previtellogenic oocytes and oocytes in primary or endogenous vitellogenesis. At these stages, the rough endoplasmic reticulum (RER) produces a granular electron-dense material and sends it to the Golgi apparatus, where it will be modified, compacted and transformed into immature yolk granules. From stage III, secondary or exogenous vitellogenesis begins (with no interruption of endogenous vitellogenesis), where follicular cells nourish the oocytes and extracellular material is absorbed by endocytic vesicles, which fuse with immature yolk granules (forming mature granules) or with existing mature yolk granules. In stages IV and V, secondary vitellogenesis continues and mature yolk granules progressively occupy the cytoplasm. In M. amazonicum, the patterns of increase in oocyte diameter are quite similar between phenotypes, being greater in the small-size phenotype. This is related to the formation of larger oocytes/eggs and the production of large lipid reserves for their larvae. Changes in GSI and HSI during ovarian development show strong similarity between phenotypes, supporting the results obtained by histology and ultrastructure. Females in stages III and IV mobilize hepatopancreas reserves for ovarian maturation, which justifies the higher HSI values recorded in these stages. On the other hand, females in stage V show higher GSI and lower HSI values, indicating a mobilization of resources for the end of ovarian development as the females are ready to spawn.

Female energy dynamics in the southernmost fiddler crab: Mixed breeding strategy in Leptuca uruguayensis

At the south of its geographical distribution, the fiddler crab Leptuca uruguayensis shows two population spawning events, with more than 65 % of the females being ovigerous. The aim of this study was to assess the energy dynamics in L. uruguayensis females to estimate how they mix the capital and the income breeding strategies in the first and second spawns of the short reproductive season. The relationship between the hepatosomatic (HIS) and gonadosomatic (GSI) indices was used to assess the contribution of the hepatopancreas to ovary maturation, as indicative of the capital breeding strategy, whereas the feeding rate and the energy available in the food resource (sediment) were estimated to assess the importance of energy intake in ovary maturation, as indicative of the income breeding strategy. Before the first spawn, a significant negative relationship between the HSI and GSI (p < 0.001) and an increase of 28.2 % in the feeding rate were recorded. This suggests that the first spawn was mainly supported by energy reserves in the hepatopancreas, indicating that females used mostly the capital breeding strategy. After the first spawn, total lipid content in the hepatopancreas decreased by 33 %. On the days before the second spawn, the relationship between the HSI and GSI showed a negative but not significant (p = 0.125) trend, whereas the feeding rate increased even more. This suggests that the intense feeding activity provided the most important energetic source for ovary re-maturation, indicating that females used mostly the income breeding strategy. Also, in the second spawn, the GSI was 24.1% smaller, a fact that affected female fecundity and weight of the egg clutches, which were respectively 12 % and 11 % lower than in the first spawn. However, the energy supply allocated to each embryo was equivalent in both spawns. This study shows how L. uruguayensis females mixed the capital and income breeding strategies to take advantage of all available resources to produce two spawns in a short reproductive season.

The dynamics of the liver weight and liver indices in the course of gonad maturation of gadid species on Eastern Kamchatka

Longterm data on the liver weight, hepatosomatic (HSI) and gonadosomatic (GSI) indices of walleye pollock, Pacific cod and saffron cod are analyzed on Eastern Kamchatka in seasonal aspect and in the course of gonad maturation. Individual values of the indices extensively vary and depend on the fish body length, season and stage of gonad maturity. The dynamics of the HSI is agree to the dynamics of the GSI during the year and depending on gonad maturity. The maximum values of the HSI are typical for walleye pollock and Pacific cod individuals with the gonads of the III stage of maturity. The maximum values of the index in saffron cod are found in mature individuals with immature gonads. The minimum values are demonstrated by the fish with the gonads at the stage of final spawning or of post-spawning recovery. During the annual reproduction cycle males and females of walleye pollock and cod realize different scenarios of spending and accumulating liver fat. Whereas the maximum HSI is observed in the fish with the gonads at the III maturity stage, the minimum values in males are typical for individuals with smelting gonads, and in females – on finishing the spawn. That can be connected to possible feeding for the individual. Liver weight and liver index can increase in males just shortly after finishing spawning, in females that is found only at the stage of post-spawning recovery.

Stress promotes reproduction in the annual fish Austrolebias reicherti

Glucocorticoids (GCs) regulate metabolism and energy balance by mediating physiological and behavioural responses to stress. Vertebrates respond to environmental challenges by increasing GC levels, which mediate the reallocation of resources from delayable activities such as reproduction to immediate survival necessities. However, when future reproductive potential is low, it has been hypothesized (and evidenced in a few semelparous species) that stress should adaptively promote reproduction rather than suppress it, even at the expense of wellbeing. Due to their unique life cycle and particular habitat, annual fishes (Cyprinodontiformes, Aplocheiloidei) are ideal unexplored model systems to test the prediction that GCs promote reproduction. Annual fishes are among the most remarkable extremophile species with the shortest vertebrate life span. They inhabit ephemeral ponds, and after reaching sexual maturity in few weeks, they breed continuously. As the breeding season progresses, and pond dry-out is imminent, future mating opportunities decrease together with the impoverishment of environmental conditions. In this study, we evaluate, for the first time in annual fishes, how reproduction is affected by high GC levels. We first show that male Austrolebias reicherti increase their cortisol levels as the breeding season progresses and environmental conditions deteriorate in the wild. Furthermore, increased cortisol levels in males were associated with increases in female gonadosomatic (GSI) and hepatosomatic (HSI) indices and a decrease in male HSI. Secondly, we show that cortisol treatment induces (1) an increase in male courtship behaviour and in the intensity of male typical coloration, (2) a weight loss in males and (3) an increase in female HSI. Overall, we demonstrate that cortisol promotes reproduction in both sexes of A. reicherti with sexually distinct effects, representing a clear exception to the traditional role of the stress response impairing reproduction.

Plasma energetic substrates and hepatic enzymes in the four-eyed fish Anableps anableps (Teleostei: Cyprinodontiformes) during the dry and rainy seasons in the Amazonian Island of Maracá, extreme north of Brazil

ABSTRACT Anableps anableps is a viviparous teleost typical from Amazon Delta estuaries. It is representative of this biome in Maracá, which offers a potential for biomonitoring. The aim of this study is to apply different biomarkers to males and females of this species and verify possible seasonal influences on their physiology. To collect fish, three expeditions were carried out from the rainy season of April 2018 to the rainy season of February 2019. Biometric parameters and gonadosomatic (GSI), hepatosomatic (HSI), and viscerosomatic (VSI) indexes were calculated, and blood samples were taken to measure triglycerides, total proteins, glucose, and activity of the enzymes aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP). The GSI of males is higher in the rainy season and of females in the dry season. This is probably related to the embryogenesis process. Males show an increase in biomass during the dry season, a metabolic homogeneity, and females show an increase in plasma glucose, triglycerides, and ALT activity. The tested biomarkers are potential for biomonitoring, preliminarily suggesting that there is a seasonal asynchronism between males and females of A. anableps as for the allocation of energy resources at different times of their life cycle.

Sex disparities determined by biometric and hematological measurements in Astyanax bimaculatus

ABSTRACT This study aimed to compare the body indexes and hematological characteristics between Astyanax bimaculatus males and females. Four hundred fish were randomly distributed into four polyethylene tanks (100 fish/unit) in a recirculation system and fed four times a day (3% of biomass). After 90 days, ten fish (five ♀ and five ♂) were removed to perform blood tests and to measure weight, height, total length, height/length ratio, condition factor and index determination: vicerosomatic (VSI), hepatosomatic (HSI), and gonadosomatic (GSI). The results showed a higher average weight (g) in females (12.32±0.71) compared to males (6.98±0.75), the same happened to height (cm) = (3.01±0.07) and (2.40±0.05), total length (cm) = (3.01±0.07) and (2.40±0.05), VSI (%) = (11.43±0.81) and (3.55±1.05), HSI (%) = (0.72±0.08) and (0.30±0.04), respectively. Mean corpuscular hemoglobin (pg) was higher in females (3.72±1.20) than in males (2.99±1.51). Regarding the number of thrombocytes (103.µL-1), there was an increase in males (25.71±3.91) compared to females (17.40±6.40).

2,4,6-Tribromophenol is toxic to Oreochromis niloticus (Linnaeus, 1758) after trophic and subchronic exposure

The presence of 2,4,6-Tribromophenol (TBP) in the environment increased the risk of exposure to aquatic organisms affecting the animal development or metabolism. The current study investigated the low, subchronic and trophic effect of TBP in both, male and female adult of Oreochromis niloticus. The fish were exposed to 0.5 or 50 ng g−1 of TBP every ten days for 70 days. Then, hepatosomatic (HSI) and gonadosomatic (GSI) indexes, erythrocyte parameters (hemoglobin content, nuclear morphology and morphometrical abnormalities), biochemical endpoints (glutathione S-Transferase and catalase activities, non-protein thiols, lipid peroxidation and protein carbonylation levels in the liver; and acetylcholinesterase activity in the brain and muscle), histopathological analysis (liver) and vitellogenin levels (plasma) were considered. TBP affected the HSI in male and female fish, but not the GSI. Principal Component Analysis revealed that erythrocytes from males are more sensitive to TBP exposure. Likewise, TBP induced the expression of vitellogenin, CAT activity and liver lesion in male fish comparatively with control group, but GST and NPT were influenced only by sex. Finally, the results showed that the antioxidant mechanism and cholinesterase activity effects were more pronounced in male than in female. The current data shows evidences of estrogenic endocrine disruption and toxicity in O. niloticus exposed to TBP, revealing the risk of exposure to biota.

Silver catfish (Rhamdia quelen) breeders fed on crude glycerin-containing diets exhibited metabolic alterations and increased sperm concentration

This study aimed to evaluate the effects of the inclusion of crude glycerin in silver catfish (Rhamdia quelen) broodstock diets on their growth, characteristics of fresh and cryopreserved sperm, blood biochemical parameters, and tissue centesimal composition. A total of 150 males (52.8 ± 2.93 g) and 225 females (53.4 ± 3.38 g), reared in 15 excavated 16 m2 nursery tanks, were included in the study. The fish were fed rations containing 300 g digestible protein (DP) kg−1 and 12.55 MJ digestible energy (DE) kg−1 diet, and five different crude glycerin levels (0, 40, 80, 120, and 160 g kg−1). Male growth and reproductive parameters, the DNA integrity in fresh sperm, as well as the characteristics of cryopreserved sperm were evaluated 12 months after the start of the experiment. Blood samples were also obtained to quantify the calcium, triglyceride, glucose, total protein, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total cholesterol, and high-density lipoprotein (HDL) cholesterol plasma levels, and to evaluate the erythrocyte DNA integrity. Fish were euthanized and dissected to evaluate the hepatosomatic (HSI), viscerosomatic (VSI), and gonadosomatic (GSI) indices, and to evaluate the centesimal composition of the organs and tissues. There was an increase (p < .05) in the sperm concentration of animals fed the highest level of crude glycerin. The other seminal and spermatic parameters from fresh or cryopreserved sperm remained unchanged (p > .05). Among blood parameters, the total cholesterol and total protein levels were augmented (p < .05) in fish fed rations containing 80 g glycerin kg−1, while the calcium level decreased (p < .05) in fish fed 160 g crude glycerin kg−1. The growth was not altered (p > .05). Increases were observed in the muscle dry matter and ash and testicular raw protein contents (p < .05) in the group fed the ration with the highest crude glycerin level; in contrast, the muscle protein levels were decreased (p < .05). The preliminary results showed that Rhamdia quelen males fed the highest crude glycerin dietary levels led to metabolic alterations which increased protein deposition in the testis and increased sperm concentration, without damages on growth or survival. The higher sperm concentration will allow to producing more doses of cryopreserved sperm.

Artificial reproduction of Anguilla anguilla: evaluation of biometrics characteristics of a population from Valle Campo Lagoon, Comacchio (Italy)

One of the major problems in artificial eel reproduction is identification of broodstock with high performance reproductive characteristics. The aim of this study was to study population characteristics and the reproductive potential of eels (Anguilla anguilla) located in Valle Campo valley (Comacchio, Italy). A total of 200 eels/period (spring–summer and autumn–winter) were measured to obtain an external indicator of their maturation state. Morphometric parameters were used to calculate condition factor (K), eye index (EI) and pectoral fin length index (PFLI). Silver index analyses showed the lack of silver males and of fully mature females. Most represented females were yellow females at stage II. Silver females represented 27.9% of the population. Seasonal analysis shows how temperature reduction favoured the presence of silver females versus yellow females. Statistical analysis of EI, cranial (CI), PFLI and gonadosomatic (GSI) indexes showed that significant differences were found for EI, CI, PFLI and GSI between yellow and silver eels. No significant difference was found between stage III and IV silver eels, while a significant difference for EI was found between stage I and II yellow eels and for IC at stage II with respect to all other stages. The present study defined how Valle Campo could present environmental and trophic conditions which could favour precocious development of a population of silver females with a noticeable reproductive potential, to be used in open sea release or in artificial reproduction programmes. On the contrary, the valley seems to present unfavourable conditions for both development and sexual maturation of male eels.

Incidence of morphometry variation, growth alteration, and reproduction performance of the annular sea bream (Diplodus annularis) as effective tools to assess marine contamination: how useful is a multi-biotimarkers approach?

A wide variety of contaminants in the aquatic environment causes several deleterious effects on aquatic organism traits ranging from molecular to individual and population levels. This in situ study investigated morphometry, growth performance, and reproduction success of a teleost fish, Diplodus annularis, from a polluted site "Sayada" and a reference site "Salakta" in the eastern Tunisian coastline. Morphometric indexes, generalized Procruste analysis, thin plate, and otolith contour methods were used to assess the pollution effects on morphological traits. The growth performance of fish from contaminated and control sites were studied using the Von Bertalanffy equation. Gonadosomatic (GSI) and Hepatosomatic (HSI) Indexes and absolute and relative fecundity were used to assess the impact of pollution on the reproduction success of this species. The obtained results showed that the fish of the contaminated zone had significant alteration of the morphology, slower growth, significant increase in the HSI, significant decrease in female GSI, and a decrease in absolute and relative fecundity compared to specimens from the unpolluted zone. Based on these results, the biological traits of Diplodus annularis can be used as biological biomarkers in the monitoring and protection programs of the marine contamination in the Mediterranean Sea.

Reproductive strategy of Scyliorhinus canicula (L., 1758): a holistic approach based on macroscopic measurements and microscopic observations of the reproductive organs

Understanding reproductive features of elasmobranchs that affect population recovery and natural mortality is essential for conservation management planning. Considering macroscopic and microscopic observations of the reproductive tract in 2253 individuals, sampled in Hellenic waters over a 7-year period, four reproductive stages were described. The presence of advanced spermatocyst stages in immature testes supported the early gamete development and long maturation process. The simultaneous presence of follicles of all developmental stages in mature ovaries indicated a protracted egg-laying season. An extended reproductive period was also supported by monthly records of egg-laying females, sexually active males, large egg cases and high values of the gonadosomatic (GSI) and hepatosomatic (HSI) indices. Size at maturity was similar for both sexes. Females and males exhibited no depth segregation compared with individuals of different maturity stages regardless of sex. Sex, size and maturity stage significantly affected GSI, HSI and the relative condition factor. All three somatic indices showed a similar monthly variation, supporting a fat assimilation rate that follows maturation rate, with both affecting physiological condition. The severe population decline that Scyliorhinus canicula has recently undergone should focus our attention on future research supporting robust population modelling to help management of the species.

Reproductive cycle of Aplodinotus grunniens females (Rafinesque, 1819) in the Usumacinta River, Mexico

The freshwater drum Aplodinotus grunniens is a species widely distributed in North America. In the Mexican southeast, this species occurs in the Usumacinta River, where it supports an artisanal fishery. In this regard, the present study was conducted to supply detailed information on the female reproductive cycle of this species. Calculations of gonadosomatic (GSI) and hepatosomatic (HSI) indexes, histological and visual staging of ovaries as well as the staging of oocyte development were applied together to determine the reproductive changes during an annual cycle. The histological analysis revealed the presence of spawning capable females throughout the year, and the distribution frequencies of oocyte diameters displayed the continuous occurrence of mature oocytes, with great data dispersion and different modal groups. These observations were further corroborated by the presence of alternating peaks and drops in the GSI and HSIs, which were correlated with the occurrence of maturing and spawned females. These data, taken together, reveal that A. grunniens from the Usumacinta River is a partial spawner with asynchronous ovarian development and undetermined fecundity that reproduces year-round, but with spawning occurring preferably during the rainfall-flooding season (June to November). The Usumacinta River seems to be a permanently favorable environment for sheltering, feeding and growth of A. grunniens broods, especially during the flooding season. The information generated in this study will be useful for the development of management strategies in the wild as well as for the exploration of A. grunniens as a potential species for aquaculture production in southern Mexico.

Dry or wet? What is the best choice to determine gonadosomatic and hepatosomatic indexes in females of Macrobrachium amazonicum ?

The gonadosomatic (GSI) and hepatosomatic (HSI) indexes are widely used for the evaluation of reproductive biology in crustaceans. However, the use of either wet or dry weight for estimating these indexes is not standardized in the literature. Here, we compare the GSI and HSI indexes based on wet and dry samples of females of Macrobrachium amazonicum from populations with different phenotypes (large and small‐size prawns) as a model. In our analysis, for GSI, the application of wet weight tended to overestimate the values recorded in the initial (I‐II) and intermediate (III) stages of ovarian development, and underestimate the results in the final (IV‐V) stages when compared to the use of dry weight. This could be attributed to the reduction in cytoplasmic organelles and water content of the cytosol due to the increase in yolk and lipids in the oocytes throughout ovarian development. For HSI, no significant differences were detected between wet and dry samples. However, the dry HSI computed at all stages of development was overestimated when compared to the use of wet samples, and only the hepatopancreas of females at the final stage (V) showed a significant decrease in water content. Thus, our results indicate that M. amazonicum females maintain constant hepatopancreatic reserves throughout ovarian development. In this way, the use of dry weight is more adequate to estimate GSI and HSI in this species.

Reproduction and sexual dimorphism of daubed shanny (Teleostei: Leptoclinus maculatus) in Svalbard waters

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.

Reproduction of the fish Poeciliopsis gracilis (Cyprinodontiformes: Poeciliidae) in Coatetelco, a tropical shallow lake in Mexico

A reproductive analysis of 1 225 specimens of Poeciliopsis gracilis obtained through monthly samples from Coatetelco, a tropical shallow lake in Central Mexico, was made. There was an evident sexual dimorphism, including a difference in body size at the onset of reproduction. Sex ratio deviated significantly from unity. Monthly variations in gonadosomatic (GSI), hepatosomatic (HSI) indexes and ovarian development stages showed that the spawning season was from July to October, coinciding with the rainy season and phytoplankton biomass increase.

Reproductive biology of lotak, Cyprinion macrostomum Heckel, 1843 (Pisces: Cyprinidae), from the Tigris River drainage

Some reproduction aspects of the doctor fish, Cyprinion macrostomum, were examined for the first time from the Tigris River drainage. A total of 316 specimens were caught from Gamasiab River in western Iran, at monthly intervals throughout the year from January to December 2013. Age, sex ratio, fecundity, oocytes diameter, gonado‑somatic (GSI), modified gonado‑somatic (MGSI) and Dobriyal (DI) indices were estimated. Regression analyses were used to find relations between fecundity and fish size (length and weight), gonad weight, and age. Sex ratio differed significantly from unity, and the percentage of males was greater than that of females. The mature females and males were longer than 108 mm and 94 mm in total length (+2 and +1 in age, respectively). The GSI ranged between 0.09-2.94% and 1.70-15.53% for males and females, respectively. Gonad indices showed spawning took place from May to August, when the water temperature was 16 to 24 °C. The average diameter of the oocytes ranged from 0.2 mm to 1.7 mm, in the spawning season. The averages of absolute and relative fecundity (relative to body weight) were 3642.51 eggs (SD ±1219.92) and of 55.04 (SD ±14.12) per gram body weight, respectively. The absolute fecundity was significantly related to body weight and ovary weight.

Reproductive biology of Alburnus mossulensis (Teleostei: Cyprinidae) in Gamasiab River, western Iran

In the present investigation, some reproductive characteristics of Alburnus mossulensis were examined. Sampling of 325 specimens were carried out at monthly intervals from Gamasiab River, Tigris River drainage, western Iran, through the year 2013. Age, sex ratio, fecundity, oocytes diameter, gonadosomatic (GSI), modified gonadosomatic, Dobriyal and hepatosomatic indices were measured. Regression analysis was used to estimate the relations between fecundity and standard length, body weight, gonad weight and age. All of the male with 70.0mm and female with 75.0mm in standard length, and all of those older than one year were ripe. The mean egg diameter ranged from 0.11mm (August) to 0.84mm (May). Spawning took place in May, when the water temperature was 18 to 22°C. Average GSI values for females at the beginning of the reproduction period (March) and in ripe mature females (May) were 5.05% and 12.03%, respectively. The averages of absolute and relative fecundity (g/body weight) were 1920 eggs (±1025SD) and 99.03 (±94), respectively. The absolute fecundity was significantly related to body length and ovary weight.

Reproductive biology of Poecilia sphenops Valenciennes, 1846 (Cyprinidontiformes: Poeciliidae) at the Emiliano Zapata Reservoir in Morelos, Mexico

ABSTRACT Poecilia sphenops is a native species recently recorded in the Balsas basin and the Amacuzac River in Morelos (Mexico), in which it is abundant and widely distributed. This study analyzed some aspects of the reproductive biology of Poecilia sphenops from the Emiliano Zapata Reservoir, in Central Mexico. Specimens were collected using a 20 m-long seine with a 5 mm mesh size, from January to December 2006. A total of 581 specimens were collected: 407 females (70.0%), 83 males (14.3%) and 91 individuals with no differentiated sex (15.7%). Fish ranged from 20 to 96 mm in total length and 0.01 to 13.07 g in body weight. The female to male sex ratio (4.9:1) deviated significantly from the unity (χ2= 214.2, p&lt;0.05). Monthly variations in gonadosomatic (GSI) and hepatosomatic (HSI) indexes and ovarian development stages showed that P. sphenops spawning season occurred between July and October, concurring with the rainy season. Another reproduction peak was registered in February. The largest length registered for males and females was 96 mm and 83 mm, respectively.

Comparison of growth parameters of tiger puffer Takifugu rubripes from two culture systems in China

Growth parameters, such as body weight (BW), viscerosomatic (VSI), hepatosomatic (HSI), and gonadosomatic (GSI), of the tiger puffer Takifugu rubripes reared in two culture systems, open-indoor combination aquaculture system (OIS) and recirculating aquaculture system (RAS) were compared in the present study. At the end of the trial, the tiger puffers in RAS (BW: 878.06±134.61g; GSI: 2.78±0.34%; VSI: 14.33±2.00%; HSI: 9.11±1.63%) obtained higher BW and GSI, but lower VSI and HSI than those reared in OIS (BW: 771.10±170.49g; GSI: 0.44±0.26%; VSI: 18.50±2.98%; HSI: 13.64±2.43%) (P<0.05). Based on the data, slaughter ratio (SR) of the fish in RAS (85.19±1.82%) was significantly higher than that reared in OIS (81.57±3.06%) (P<0.05). Moreover, the male fish grew better than the female in OIS, however the trend was reverse in RAS. Fishes reared in RAS had already entered puberty after ~500days culture. Given the high economic value of soft roe (gonad of male tiger puffer), these results inspired us in carrying out monosex culture to promote the development of tiger puffer industry. Statement of relevanceThis study inspired us in monosex culture of tiger puffer.