Mean GSI Research Articles

Reproductive Cycle, Size at Maturity and Fecundity of Giuris margaritaceus in Limboto Lake

Graphical Abstract Highlight Research The size of the first mature gonads in hulu'u fish can be analyzed. Differences in sperm and egg size characterize sexual maturity. Sexual maturity is not influenced by season. Hulu'u fish have an asynchronous spawning type. Abstrack Understanding fish reproduction biology, particularly sexual maturity, the reproductive cycle, and fecundity, is useful for managing fisheries. The reproduction of Giuris margaritaceus in Limboto Lake is regrettably unknown. Over a year, fish specimens (N = 662) were gathered. They ranged in length from 6.5 to 20.9 cm (mean SD 10.9±2.5). Fecundity varied from 30,057 to 61,920. The first sexual maturity of male and female fish occurred at different sizes, 11.2 cm and 10.3 cm, respectively. This information is needed to determine this fish's lowest acceptable harvest length under the management aim to enter all-female fish for reproduction at least once. We estimated the reproductive of G. margaritaceus cycle using the size of the oocytes, histological analysis of the ovaries, and monthly mean GSI. These techniques produced the same reliable conclusion: G. margaritaceus can spawn yearly, with maximal between September and October. Based on this finding, spawners of Giuris margaritaceus can be kept from entering the reproductive stock between September and October. Future efforts to fine-tune fishing efforts for the effective management of G. margaritaceus may be aided by the study's findings.

Insights into the Food and Feeding Habits of the Indian Mackerel (Rastrelliger kanagurta) from the Coast of Goa

The Indian Mackerel is a commercially important fish species and India contributes to world’s 90% of mackerel production. The present study deals with gut content analysis of the Indian Mackerel Rastrelliger kanagurta to determine the type of feed and the feeding habitat. The gonado-somatic index and gastro-somatic indices were determined to find out the spawning period and maturity of the fishes. The stomach emptiness was also calculated to estimate the fish appetite from the stomach content. The present study indicated that Diatoms formed the predominant planktonic feed followed by Dinoflagellates. A total of 25 different types of planktons were found to be preferred by Rastrelliger kanagurta. The gut content also revealed sand particles, fish scales and cnidarian spicules. Highest mean GSI and lowest GaSI were observed in the month of April. The stomach emptiness index revealed gluttonous feeding from November to March and comparatively gluttonous feeding in the month of April. From the present study it can be concluded that Rastrelliger kanagurta, though shows preference for diatoms (40.74%) and dinoflagellates (22.22%), the dietary preference is not limited to it, but they also exhibited preference for Crustaceans (except copepods) (14.81%), Cyanobacteria (7.40%), Copepods (7.40%), molluscs (3.70%) and Protists (3.70%). The present study analysed the food constituents and feeding habitat of the Indian mackerel through gut content analysis. The intensity of feeding was also compared to the size of the fishes, reproductive maturity and the spawning time.

SILVERING ASPECTS AND IMPACT OF ANGUILLICOLA CRASSUS ON EUROPEAN EELS FISHED IN THE MAFRAGH ESTUARY (WESTERN MEDITERRANEAN)

In this study, we focused our research on the impact of the nematode Anguillicola crassus on the growth and silvering mechanism of the structural eel subpopulation in the Mafragh Estuary using a rapid method that allowed us to identify silver eels that migrate to the Sargasso Sea the following season. The results of our study show that the fraction of the eel population present, a mean length, as 634.52 ± 73.84 mm, a mean weight as 532.43 ± 225.31 g and the mean age was 4.45 ± 1.09 years. The sex ratio observed is in favor of silver females (70%). In the latter, the average OI value exceeds 11% and that of FI is above 5%. The highest mean GSI values were found in migrating females of stage IV (0.93%±0.34) and stage V (0.94%±0.54); Migrant eels of stage IV show the lowest mean HSI values (1.29%±0.27) and IGu values (1.66±0.87) and the highest Mean K-value (0.248± 0.068) despite their high infestation with A. crassus (P = 66%, I=11.5 worms/infested eel; A = 7.67 worms/examined eel).

Sex steroids in diploid and triploid gibel carp (Carassius gibelio) of both sexes in different phases of the reproductive cycle

The changes in concentrations of 17ß-estradiol (E2), testosterone (T), 11-ketotestosterone (11-KT) in the gonads and plasma of diploid and triploid gibel carp (Carassius gibelio) from the Siemianowka Reservoir, the Vistula River drainage were quantified and compared using an enzyme immunoassay. The phase of gonad maturity was based on histological analysis and the gonadosomatic index. All fish had properly developed gonads in the pre-spawning, spawning and late spawning phases of the reproductive cycle in the fish collected in April, June and October, respectively. Diploid and triploid females and males did not differ in mean GSI in all reproductive phases. In October, ovaries of most females contained vitellogenic oocytes, testes had large numbers of spermatozoa. The hormone concentrations in both tissues depended mainly on the reproductive phase, but not on ploidy. The patterns of changes in E2 concentrations was similar in females and males. In the pre-spawning phase, diploid and triploid females showed differences in the concentrations of 11-KT in gonads and plasma, and T in plasma. Diploid males differed in pattern of T concentrations in gonads and plasma, while all males showed a similar pattern of 11-KT plasma concentrations. Spermatozoa observed in triploid males suggest that they participate in reproduction. Gibel carps, regardless of ploidy, had an extended period of reproduction, which makes this invasive species a potentially greater threat to native ichthyofauna. The sex androgen concentrations that differed between 2 n and 3 n females could be physiological factors potentially contributing to the coexistence of gynogenetic C. gibelio females and sexual diploids.

Insight on the reproductive biology of small striped cuttlefish, Sepia prabahari in Gulf of Mannar, Indian Ocean and recommendation for a minimum legal size

This paper provides insight into the size composition and reproductive aspects of small striped cuttlefish Sepia prabahari distributed exclusively in the Gulf of Mannar (GoM) Biosphere Reserve, in the Indian Ocean which contributes 11% to the cephalopod catch in this region. The size composition in the fishery varied between 4.6 and 14.6 cm in dorsal mantle length (DML) and the length group between 8.1 and 10 cm dominated the catch (45%). The DML-weight relationship for male, female and for the pooled sexes were 0.5561 DML2.31; 0.4821 DML2.39 and 0.5214 DML2.34 respectively. Observations on maturity stages indicated year-round spawning with two peaks. Maturity indices increased in tandem with the gonadal development in the cuttlefish. Mean GSI in females showed a multi-fold increase from 0.41 in maturing to 2.20 in mature stages, while it increased from 0.51 to 1.35 for the respective stages in males. The minimum legal size (MLS) was set considering the minimum size at maturity of 7.0 cm for the species. The Lm50 estimated at 9.2 cm DML for males; 9.7 cm for females and 9.4 cm for the pooled sexes, showed early maturation in males. The size composition indicated that nearly 53.7% of the commercial catch in the fishery is below the Lm50, while 5% of the catch was below MLS. Management measures limiting the fishing pressure on sub-adults are recommended for sustainable exploitation of the resource.

Popularity of Commercial and Non-Commercial Diets From 2010–2020: A Google Trends Analysis

Abstract Objectives When looking to follow or change a diet, Americans have many choices across numerous commercial (COM) and non-commercial (NCOM) diets. Since the Internet is a go-to source for information, this study sought to use Google Trend Data (Google Search Interest; GSI) from 2010–2020 to examine the popularity of diets included in the 2021 U.S. News & World Reports’ (USN) Best Diet's Report. There were four aims: 1) identify which COM and NCOM diets had the highest GSI, 2) identify which diets had a higher GSI compared to the healthiest COM and NCOM diet (Weight Watchers and the Mediterranean Diet, respectively; determined by USN), 3) determine if any relationship exists between GSI and various USN healthfulness scores, and 4) determine which diet type (e.g., Balanced, Elimination, Low Calorie, etc.) has the highest GSI. Methods COM (n = 15) and NCOM (n = 24) diet names as well as their diet type (Balanced, Elimination, High protein, Low Calorie, Low Carbohydrate, or Low Fat) and scorings (Overall, Health, Managing or Preventing Diabetes, Heart-Health, Short-term and Long-term Weight Loss, Ease of Following, Nutrition, and Safety) were collected from USN and popularity was measured using GSI data (GSI Range: 0–100) collected from Google Trends for the United States from 2010–2020. Spearman or Pearson correlation analyses were used when necessary with alpha set to 0.05. Results Weight Watchers (mean GSI: 29.80) and the Keto Diet (mean GSI: 15.05) had the highest mean GSI over the past ten years of all COM and NCOM diets, respectively. While Weight Watchers had the highest mean GSI and was the highest ranked COM diet by USN, four diets had a higher GSI compared to the Mediterranean Diet (in descending order: Keto Diet, Paleo Diet, Vegan Diet, and the Fast Diet). The diet type with the highest mean GSI was low carbohydrate for both COM and NCOM diets. Mean GSI was not correlated with any of the USN diet scores (P > 0.05 for all). Conclusions These results suggest that numerous, less-healthful NCOM diets are more popular than the most healthful NCOM diet, the Mediterranean Diet. Understanding what attracts people to these less-healthful NCOM diets can provide insight into diet selection that can be used to better support diet choice. Funding Sources None.

Reproductive biology of the white marlin ( Kajikia albida ) in the southwestern and equatorial Atlantic Ocean

The present work describes the reproductive biology of the white marlin (Kajikia albida) caught in the southwestern and equatorial Atlantic Ocean. The gonads of 924 fish were collected by observers on board Brazilian tuna longliners, between November 2004 and December 2006. The spawning season was assessed by the monthly frequency distribution of distinct stages of maturity and monthly mean female gonadosomatic index GSI. Sixty-one percent (n = 656) of the fish examined were female, with a Lower Jaw Fork Length (LJFL) between 83 and 236 cm (mean = 155.5 ± 16.63). The 268 males had a LJFL between 90 and 220 cm (mean = 152.3 ± 34.62). Although the northeastern region of Brazil does not appear to be a significant spawning area for the species, the results suggest a higher reproductive activity in the third quarter of the year. Using a Bayesian logistic model approach, length at 50% maturity was estimated at 145.04 cm (credibility interval of 95%, 143.94–146.09 cm), for females, and at 140.03 cm (credibility interval of 95%, 137.28–142.52 cm), for males.

Aspects of the bionomics of Brackish Water Prawn (Macrobrachium macrobrachion: Herklots 1851) in the interconnecting lagoons of South-Western Nigeria

ABSTRACT Macrobrachium macrobrachion is a caridean shrimp native to brackish and fresh waters of West Africa and is also considered to have potential for aquaculture and other research purposes. The bionomics of M. macrobrachion from Badagry, Lagos and Epe Lagoons were investigated monthly for 24 months between June 2013 and May 2015. The sex ratio revealed that there were more females from Badagry and Lagos Lagoons with males dominating Epe Lagoon. The fecundity estimates from the three lagoons ranged between 760 and 84,850 eggs with a weak correlation (R < 0.5). The mean GSI values ranged between 1.76 and 35.29% and showed that there were no significant differences (P > 0.05) in M. macrobrachion from Badagry and Lagos Lagoons while the GSI values from Epe Lagoon was significantly different (P < 0.05) from other lagoons. The egg diameter from the three lagoons ranged from 258 to 450 μm with no significant differences (P > 0.05) in the values. The dominance of females in Badagry and Lagos Lagoons could be attributed to the fact that both lagoons are salty and the females require such conditions to spawn while males dominated Epe Lagoon. The scientific observations documented in this study, will therefore serve as important references in the species assessment, cultivation, management and conservation of the prawn fisheries.

Reproduction and Seasonal Growth Estimates of the Black Goby, Gobius niger (Osteichthyes: Perciformes: Gobiidae) in the Southeastern Black Sea Region of Turkey

Seasonal growth pattern and reproductive biology of the black goby, Gobius niger, were studied in southern Black Sea between December 2012 and November 2013. The seasonal von Bertalanffy growth parameters, computed from ELEFAN, were estimated as L∞ = 11.90 cm TL, K = 0.701 year-1, C = 0.633, and WP = 0.492 for the Hoenig seasonal model and as L∞ = 12.14 cm TL, K = 0.680 year-1 for non-seasonal von Bertalanffy model. The size at sexual maturity (TL50) was estimated as 8.9 cm TL. The GSI ranged 0.60 in December and 8.57 in April (mean 3.82±0.818) for females and between 0.61 in October 2013 and 2.90 in May 2013 (mean 1.70±0.260) for males. The seasonal growth was pronounced probably due to reproduction activity which extended investment of energy in reproduction causing slower growth. The GSI development was related to photoperiod and the monthly variations of GSI values indicating that the intensive spawning occurred between April and August. During spawning time, the mean GSI value of females (6.04±1.177) was 2.9 times higher than the mean GSI values of males (2.08±0.423) (P &amp;lt; 0.05). The results of this study were offered as biological input parameters regarded as a reference for the conservation and management of the Black Sea stocks of the black goby.

Reproductive cycle, sexual maturity and fecundity of Nemipterus furcosus (Valenciennes, 1830)

Understanding the reproductive biology particularly sexual maturity, reproductive cycle and fecundity of fish is useful for fisheries management. Unfortunately, there is no information about reproductive biology of Nemipterus furcosus. This study addresses this deficit for N. furcosus. We conducted a 12-month study to understand the reproductive biology particularly the sex ratio, sexual maturity, fecundity and reproductive cycle of N. furcosus at the east coast of peninsular Malaysia. Results indicated that ratios of male and female were statistically similar up to 19.0 cm TL (total length). Male outnumbered female above 19.0 cm TL (P < 0.05). The fecundity ranged between 54,970 and 236,938 with a mean fecundity of 102,477 ± 43,580 (standard deviation). Male and female fish reached first sexual maturation at almost same size, 15.8 and 15.6 cm, respectively. This information is needed to determine the lowest acceptable harvest length of this fish under the management aim to enter all female fish for reproduction minimum one time in their life. We estimated the reproductive period of N. furcosus applying oocytes diameter, histological examination of ovaries and monthly mean GSI. All of these methods gave a consistent result about spawning season, which appeared to be from March to July with peaks in March and June. Based on this result, N. furcosus spawners can be protected during March to July for entering the reproductive stock. Apart from artificial breeding, the results of this study might facilitate future efforts at fine-tuning fishing effort for a proper management of N. furcosus.

Sex ratio and reproduction of invasive red devil, (Amphilophus labiatus: Cichlidae) in Lake Sentani, Indonesia

AbstractThe Red Devil Cichlid Amphilophus labiatus (Günther 1864), native to Lake Nicaragua and Lake Managua in Central America, is widely cultivated as an attractive, yet aggressive, aquarium fish that has been introduced to several freshwater locations around the world. It was recently introduced into Lake Sentani in Indonesian New Guinea, a naturally rich aquatic habitat home exhibiting a diverse fauna with high endemism. To better understand the invasive potential and impacts of A. labiatus, the present study was undertaken to describe the sex ratio and reproductive potential of A. labiatus in Lake Sentani through determination of its gonad maturation stages, gonado‐somatic index and fecundity. The fish were collected using floating gill nets at six locations around the lake between June and August 2019. Sex identification, gonads type, gonad stage and weight, fecundity were observed in the laboratory. Of the total 542 of A. labiatus collected during the survey, 345 individuals were sampled for sex ratio and reproduction. The overall male:female ratio was skewed towards males in a ratio of 3.28:1. The males were generally found to be in the gonad maturation stage I, while the females were commonly found in gonad maturation stages III and IV for all sampling locations during the study period. The highest male mean GSI value was found for the Yakonde site (0.24 ± 0.21) and at the Ayapo site (1.11 ± 1.01) for the females, with a fecundity of 191–2,720 eggs. The fish have spread to most parts of the lake, being conditioned to potentially spawn at any location, thereby providing an explanation for the observed rapid increase of the A. labiatus population over the last ten years. The results of the present study suggest a high invasive potential for this species in this and other similar lake habitats, warning that their careful management should be undertaken to restrict their further spread in Indonesia and elsewhere.

Gonadosomatic Index as a Determinant of Spawning Season in the Milieu of Ovarian Dynamics of Indian Freshwater Spiny Eel Mastacembelus armatus (Lacepede)

Gonadosomatic index is a less expensive and alternative method than histological observation for the determination of spawning season in fish species. Mastacembelus armatus, an indigenous fish species of southern Asia, also resides in Indian subcontinent. This fish species is facing an alarming declining in their number in the last decade. Due to its moderate cost, It is mainly taken by the lower income group of people of the society. Reproductive care, by artificial breeding, has been taken for those fish species having a high cost in the market or becoming less in number in nature for business purposes or preserving the biodiversity, respectively. The present study was undertaken to understand the spawning season of the fish Mastacembelus armatus by calculating the gonadosomatic index, so in recent future artificial breeding can be done in this fish species. The mean GSI value for testes is 0.95 ± 0.06, 1.42 ± 0.22, 2.10 ± 0.38 and 0.72 ± 0.08 in growth, maturation, spawning and resting phase respectively. The mean GSI value for ovary is 1.38 ± 0.4, 2.86 ± 0.84, 12.50 ± 1.70 and 1.80 ± 0.15 in growth, maturation, spawning and resting phase respectively. In this study it was found that spawning season include one peak in a year and mainly it falls in the months of June to August in both the sexes.

Body condition (Wr ) and reproductive potential of bighead and silver carp hybrids: Postzygotic selection in the Mississippi River Basin.

Invasive bighead (Hypophthalmichthys nobilis) and silver carp (H. molitrix) are reproductively isolated in their native range, but form a bimodal, multigenerational hybrid swarm within the Mississippi River Basin (MRB). Despite observed F1 hybrid superiority in experimental settings, effects of postzygotic selection on bighead and silver carp hybrids have not been tested in a natural system. Individual parent and hybrid genotypes were resolved at 57 species‐specific loci and used to evaluate postzygotic selection for body condition (Wr) and female reproductive potential (presence of spawning stage gonads and gonadosomatic index [GSI]) in the MRB during 2009–2011. Body condition in the Marseilles Reach, Illinois River declined with a decrease in species‐specific allele frequency from 1.0 to 0.4 for each species and early generation hybrids (F1, F2, and first‐generation backcross) had lower mean Wr than late generation hybrids (2nd+ generation backcrosses) and parentals. Proportions of stage IV and stage V (spawning stage) female gonads differed between bighead and silver carp, but not among parentals and their early and late generation hybrids within the MRB. Mean GSI values did not differ between parentals and hybrids. Because reproductive potential did not differ between hybrids and parentals, our results suggest that early generation hybrids occur in low frequency either as a factor of poor condition (Wr) and postreproductive survival, infrequent reproductive encounters by parental bighead and silver carp, or selection pressures acting on juvenile or immature life stages. Our results suggest that a combination of genetic and environmental factors may contribute to the postzygotic success of bighead and silver carp hybrids in the Mississippi River Basin.

Cyclic variations of gonad development of snow trout, Schizopyge niger from the river Jhelum of Kashmir Himalaya

The aim of the present study was to know the cyclic changes in gonadal maturation and to investigate the various developmental stages of oocytes and testicular germ cells of snow trout, Schizopyge niger. A total of 316 fish specimens were procured from three sites of river Jhelum during November 2016 to October 2017 and the histological analysis of their gonad was carried out. The results of the present study indicates that the male population was found significantly (p < 0.05) higher compared to female population and were reported as (1.6:1; M:F). The highest mean GSI value was recorded in male (12.24 ± 0.89) during the month of March and for female (13.74 ± 0.92) also in the month of March, which indicated that the gonadal development reached its peak during this month. The highest mean oocyte diameter was 1.04 ± 0.20 mm observed in March, showing that the oocyte reached its maturity during this month. Histological study of ovary revealed the evidence of vitellogenic yolk granule stage and ripe mature stage from December to April. While in case of male, four stages of spermatogenesis were distinguished and spermatozoa were highly abundant in the months of March and April. Mean ± SE of absolute fecundity was 3,224 ± 421 eggs and also, the relative fecundity was 69 egg/g body weight. Based on the results of GSI and the analysis of gonad histology, it was observed that the peak breeding season of S. niger occurred in the month of March. It was also noted that spawning period of this fish begins in the month of February and lasts till April with a peak breeding season in the month of March. The present study will provide a baseline information about the appropriate peak breeding of the fish, which will be useful for artificial breeding as well for prevention of fishing from natural habitat.

Some reproductive biology parameters of mosquitofish Gambusia holbrooki Girard, 1859 (Poeciliidae) in some waterbodies of southeastern Caspian basin, Iran

Eastern mosquitofish, Gambusia holbrooki , is an invasive exotic fish for Iranian inland water. This study conducted to evaluate some reproductive traits of this species in six waterbodies from southeastern Caspian basin. A total of 8500 individuals were sampled from the AlmaGol Wetland, Alakooli Dam Lake, Gomishan Lagoon, Voshmgir Dam Lake, Golestan Dam Lake, and estuary of Gorgan River during February to September 2014. The maximum age in all areas was 1 + for males and 2 + for females. The highest mean GSI value was 2.6 for males in April-May and 29.6 for females in May. Egg diameter ranged from 0.5 to 2.5 mm with a mean value of 1.43 mm. Absolute fecundity varied between 2 to 212 eggs. Both ova diameter and absolute fecundity were positively correlated with females' size, while relative fecundity had no significant correlation with females' size (length and weight). The results showed a significant variations in reproductive characteristics among the populations inhabiting different habitats. This finding is important with respect to life history of the species and ecological view as well.

The Side Effect of the Melastoma malabathricum L Ethanol Extract on the Gonad Maturation of Female Orange Mud Crab (Scylla olivacea)

The medicinal plants in aquaculture are currently being studied quite extensively by researchers. Medicinal plants can act as an inducer or aphrodisiac and an antifertility agent in gonad maturation. The aimed of the experiment was to known side effects of the herb M. malabathricum L. on maturation process in female mud crab (S. olivacea). This study used 40 crabs with an average weight of 200-250g. The experiment consists of two treatment groups. The controls group (A) that received 100 μl of aquadest and group treatment (B) received 100 μl of 2 mg/g of ethanol extract M. malabathricum L. were studied. For 5, 10, 15, and 20 days of experiment, crabs were anesthetized and sacrified. The ovary was collect for GSI and histology. The end of experiment days (20 day), the hemolymph was collect to used ELISA assay. The result showed, significant differences in treatment group and control groups (p&lt;0.05) in terms the macroscopic morphology of ovary, the mean GSI and the diameter of oocytes. Histological showed the influence of extract M. malabathricum L. on inhibited the ovary development compared with the control groups. Based on this results, it is concluded that ethanol extract of M. malabathricum L. leaves at a dose of 2 mg/g act as an antifertility agent for ovary maturation of S. olivacea.

Age, growth and reproduction of Paracobitis malapterura (Teleostei: Nemacheilidae) from Qom River, Iran

We examined 271 specimens of Paracobitis malapterura throughout the spawning season (February to July, 2014) from Qom River (Central Iran) to describe their age, growth, and reproduction. Sex ratio was 1:6.1 in favor of females. Among the examined specimens, the maximum age was 3 + years. The specimens ranged 35-120mm in total length and 0.38-9.58g in total weight. Length-weight relationship was estimated as W=1E-05TL 2.94 , W=2E-05TL 2.73 , and W=1E-05TL 2.92 for females, males and combined sexes, respectively. The growth type was isometric for females and sexes combined and negative allometric for males. Based on the gonado-somatic index values, spawning occurs between late February and late April. The highest mean GSI was 1.9, and 13.85 for males and females, respectively in April. The absolute fecundity ranged from 164 to 793 with a mean of 353.3 eggs. Fecundity was positively correlated with fish size (length and weight).

Cyclic variations of gonad development of an air-breathing fish, Channa striata in the lentic and lotic environments

The study was conducted to know the cyclic changes in gonadal maturation and to investigate the developmental stages of oocytes and testicular germ cells of an air-breathing fish, Channa striata. Fish were sampled monthly from lentic and lotic environments of three geographical locations of Bangladesh from December to November and the histological analysis of their gonad was done to evaluate the objectives. The highest mean GSI was 5.95 ± 0.20 for female in July and 0.14 ± 0.01 for male also in July showing that the gonadal development reached its peak during this month. The highest mean oocyte diameter was 1257.50 ± 24.17 μm observed in July implying that the oocyte reached maturity in this month. Histological study of ovary revealed the evidence of early yolk granule stage and late yolk granule stage from April to July. In case of male four stages of spermatogenesis were distinguished and spermatozoa were highly abundant in June and July. So the monthly pooled values of GSI and the analysis of gonadal histology indicated that the peak breeding season of C. striata occurred in July in the lentic and lotic environments. Samples collected from lentic and lotic habitats are suggestive of no difference in the development of the gonad. The results of the present study will be useful for selective breeding programme, conservation and sustainable fishery management of C. striata in its natural habitat.

The sex ratio, Gonadosomatic Index and Fecundity of the Copper Mahaseer, Neolissochilus hexagonolepis (Mc Clelland, 1839) from Tamor river, Nepal

The sex ratio, Gonado Somatic Index and fecundity of the Copper Mahseer, Neolissochilus hexagonolepis were investigated. The sex ratio was 1:1.2 (Male to female). The gonado-somatic index ranged from 0.084 % to 16.47 % for female fish and 0.086% to 5.81 % for male fish. The highest mean GSI 9.037 % was recorded in July for female fishes and the highest 2.838 % was recorded in September for male fishes. The total weight and total length of the fishes had strong positive correlation. Also, the correlation between the weight of gonad and GSI was positively correlated. Absolute fecundity ranged from to 11424. Fecundity had strong positive correlation with total length (r = 0.98), total weight (r= 0.9) and total length (r= 0.88).

Reproductive strategy of a non-annual rivulid in a perennial wetland

ABSTRACT Atlantirivulus riograndensis (Costa &amp; Lanés, 2009) is a fish registered to the basin of Patos lagoon and the adjacent coastal plains in southern states of Rio Grande do Sul and Santa Catarina, Brazil, found in shallow water courses with that have large quantities of aquatic vegetation and forest edges. The objective of this study was to investigate the reproductive strategy and tactics of this species including the sex ratio, the length at first maturity, spawning type, fecundity and the possible associations among reproduction and abiotic factors. Sampling of specimens occurred in perennial wetlands within the Banhado dos Pachecos wildlife refuge, in the city of Viamão, state of Rio Grande do Sul, Brazil, which is a conservation unit that belongs to an area of environmental protection in the Pampa Biome. The capture of 30 A. riograndensis specimens per month occurred from January to December of 2012. A total of 188 females and 172 males were captured and the total sex ratio was 1:1 in the sampled population. Sexual maturity of the species occurs after 13.59 and 11.92 mm (SL) for females and males, respectively. Both a multiple spawning and a long reproductive period (since August to March) were confirmed by the presence of post-ovulatory follicles that were observed through histological analysis and the values of the gonadosomatic index in females considered spawning capable. The average absolute fecundity of the species is of 19.33 (± 6.18) vitellogenic oocytes in mature ovaries. No significant relationship was found between mean GSI and the abiotic data. Reproductive tactics presented by A. riograndensis indicate a species with an opportunistic reproductive strategy, following the pattern of other species of the Rivulidae family.