Female Gonadosomatic Index Research Articles

Reproductive Dynamics of Coryphaena hippurus (Linnaeus, 1758) Recorded from the Bay of Bengal, India

Ghosh, S.; Satishkumar, M.; Manas, H.M.; Rohit, P.; Abdussamad, E.M., and Gopalakrishnan, A., 2022. Reproductive dynamics of Coryphaena hippurus (Linnaeus, 1758) recorded from the Bay of Bengal, India. Journal of Coastal Research, 38(2), 369–376. Coconut Creek (Florida), ISSN 0749-0208. Coryphaena hippurus, one among the large pelagic species landed from Bay of Bengal, forms an important bycatch in drift gillnets and hook and lines. The present study, first from the region, is aimed at elucidating the reproductive biology from 1150 fishes from 2017 to 2019. Fork length of sampled fishes ranged from 25 cm to 110 cm and females contributed to the catch only up to a length of 88 cm. Growth was negatively allometric and length composition varied between sexes. Sex ratio was 1M:2.04F, significantly favouring females in most months, and more so in fishes measuring below 60.0 cm. Size at sexual maturity for females and males was 54.57 cm and 59.97 cm. Monthly percent contribution of spawning females and males ranged between 20.00 to 60.61 and 29.17 to 53.57. Monthly gonadosomatic index for females and males varied between 1.48 to 3.82 and 0.89 to 1.94. The values differed significantly; higher values during August to November indicated a peak in spawning. However, spawning occurred round the year, as evident by the presence of spawners and moderate values of the gonadosomatic index. Absolute fecundity ranged from 115,200 eggs to 1,501,808 eggs, with an average of 434,688 eggs. Egg size distribution demonstrated asynchronous gonadal development and batch spawning. Egg diameter of most abundant oocytes ranged from 0.60 mm to 0.69 mm, followed by another peak at 0.80 mm to 0.89 mm. Present study, first from region, provides detailed insights on reproductive biology, some of which are maiden information from Indian Ocean and knowledge generated would contribute significantly to stock management.

The fluorescent introduction has begun in the southern hemisphere: presence and life-history strategies of the transgenic zebrafish Danio rerio (Cypriniformes: Danionidae) in Brazil

ABSTRACT Transgenic ornamental fish that fluoresce are becoming popular in the aquarium trade worldwide. Some transgenic zebrafish (TZF) records in natural water bodies have been published, but there are no data on their biological attributes in the new areas. This study aimed to evaluate the distribution, trophic ecology, and reproductive condition of the non-native TZF in headwater creeks located in the largest Brazilian ornamental aquaculture center. Insect fragments – identified as chitinous material in the ‘false stomach’- and aquatic insects were the most consumed item. TZF adults were found in breeding conditions during almost all sampling periods. The Gonadosomatic Index of females and males showed peaks during the rainy season and matched with the rising water levels. Breeding females and males were found at small body sizes, indicating early maturation, and these transgenic females produced a moderate amount of small oocytes. Sex-ratio assessment showed that females and males had the same frequencies in one site, while females were significantly more frequent than males at another location. Management recommendations, such as utilization of best management practices (e.g. screens on outlets), not using unapproved genetically modified organisms in aquaculture, and awareness with fish farmers about transgenic animals, are suggested to avoid new introductions.

Spatial and seasonal variation in reproductive indices of the clupeids Limnothrissa miodon and Stolothrissa tanganicae in the Congolese waters of northern Lake Tanganyika

Knowledge on the reproductive biology of the endemic clupeids Limnothrissa miodon and Stolothrissa tanganicae, two main target species of the pelagic fisheries of Lake Tanganyika, is constrained by fragmented monitoring activities. Here, we investigate the nursing areas of L. miodon, the timing of reproductive activities of littoral and pelagic L. miodon, and the timing of reproductive activities of pelagic S. tanganicae in the Congolese waters of the northern end of Lake Tanganyika (Bujumbura sub-basin). Nursing areas were determined year-round (2009–2010) based on the presence of clupeid larvae at two sandy and two stony beaches. The gonadosomatic index (GSI) and the proportion of fish having ripe gonads were used to study variation in reproductive indices in space (littoral vs. pelagic zones) during one year (2013–2014), as well as in time (dry vs. rainy season) during three years (2013–2016). Larvae of L. miodon were more frequently encountered on sandy than on stony beaches. Mature L. miodon females were more abundant in the littoral than in the pelagic zone, while the proportion of mature males in both habitats was similar. Irregular, low amplitude peaks could be distinguished in the GSI and proportion of mature males and females, but averages only differed between the dry and the rainy season in males. In contrast, GSI and proportions of mature males and females in S. tanganicae were higher in the dry season than in the rainy season. The reproductive effort of males and females of S. tanganicae and littoral L. miodon, but not pelagic L. miodon, was strongly synchronized. Interestingly, reproductive investment was also synchronised between pelagic male L. miodon, and pelagic S. tanganicae. Our time series strongly supports the view that L. miodon reproduces year-round in the littoral zone, while reproduction in S. tanganicae is seasonal. For fisheries management, we recommend year-round protection of sandy beaches, which are the main breeding grounds for L. miodon.

Lunar cycle and reproductive activity of Redbelly yellowtail fusilier, Caesio cuning in Karimunjawa National Park, Indonesia

Abstract. Ayodya FP, Wijayanti DP, Sabdono A. 2021. Lunar cycle and reproductive activity of Redbelly yellowtail fusilier, Caesio cuning in Karimunjawa National Park, Indonesia. Biodiversitas 22: 3075-3082. Redbelly yellowtail fusilier (Caesio cuning) is known as fish that has been widely distributed among Southeast Asian countries. Fishers in Indonesia especially target the species, causing the scarcity and depletion of the catch in many fisheries areas each year. One of the priority aspects in improving fisheries management in conservation areas is information regarding reproductive activities. Many reports suggested that the lunar cycle affects the reproductive activity of fishes. However, none of the studies reported on the effect of lunar cycle on the reproductive activity of C. cuning. This study aimed to explain the lunar cycle effect on the reproductive activity of C. cuning through gonadosomatic index (GSI), viscerosomatix index (VSI), and the observation of oocyte conditions. There were 374 individual fishes collected from Nyamuk Island, Karimunjawa from September to November 2020. Samples were taken in each phase and between major phase of the moon (new, first quarter, full, last quarter) during two lunar cycles. The results point out mature gonad (stage IV and V) was present around the new moon. The peak of female GSI occurred around the last quarter moon with figures 6.12 and 5.51% respectively. The condition of the mature oocyte and ovulation were present around the last quarter and the new moon. The condition indicates imminent spawning.

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.

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.

Effects of Ovaprim, Pituitary Gland Extract and Human Chorionic Gonadotropin on Testosterone, 11-Ketotestosterone,and 17β-Estradiol hormones of catfish (Clarias gariepinus)

This study closely inspected the effects of ovaprim, pituitary gland extract, and human chorionic gonadotropin on 11-ketotestosterone, and 17β-estradiol hormones. Females and males (T1, T2, and T3) were injected with Ova Prim as 0.5 ml/kg of fish, pituitary gland extract of catfish, and Human Chorionic Gonadotropin (HCG), respectively. Results showed that female gonadosomatic index of the spring season (10.45 ±0.35%) were significantly increased compared to other seasons: autumn followed by summer and winter seasons (0.82 ±0.06%). Results showed that T1 was better than T2, but T2 was better than T3 in all reproductive performance parameters. Plasma 17β-estradiol (ng/ml) in female catfish throughout 12 hours after injection of stimulating hormones ranged from 2.15 ng/ml in T1 to 1.65 ng/ml in T3 whereas testosterone in female of catfish throughout 12 hours were ranged from (0.031 ng/ml) in T1 to (0.036 ng/ml) in T3. Also, plasma 11-ketotestosterone (ng/ml) in male of catfish was recorded in T1 (0.154 ng/ml) followed by T2 (0.107 ng/ml) and lowest level in T3 (0.083 ng/ml) but plasma testosterone (ng/ml) in male was recorded in T1 (0.225 ng/ml) followed by T2 (0.189 ng/ml) and lowest level in T3 (0.143 ng/ml).

Intra‐annual changes in reproductive indices of male and female Himalayan snow trout,Schizothorax richardsonii(Gray, 1832)

Periodic changes in reproductive hormone levels, gonadal histology and gonadosomatic index (GSI) of snow trout, Schizothorax richardsonii, were examined to ascertain annual cycle of gonadal development and reproductive status in their natural habitat. In females, there were coherent changes in plasma 17β-oestradiol and vitellogenin along with GSI, oocyte maturation and vitellogenic progression, collectively indicating two distinct maturation peaks during the months of September and February. Coinciding with this, in males, plasma 11-keto testosterone was also noticeably higher during September and February, with highest GSI values in September. However, plasma 17α, 20β-dihydroxyprogesterone levels in males were found to be persistently high from September to February. This observation suggests the potential presence of matured oozing males over a longer period, unlike in females. Overall, the close association between reproductive hormone levels, GSI and gonadal maturation stages in males and females (particularly, the presence of postovulatory follicle complexes) with apparent natural synchronization clearly indicates that S. richardsonii breeds twice in a year, possibly during late September to early November and late February to early April in the coldwater riverine habitats of the Indian Himalayan region.

A Teleost Fish Model to Understand Hormonal Mechanisms of Non-breeding Territorial Behavior.

Aggressive behaviors occurring dissociated from the breeding season encourage the search of non-gonadal underlying regulatory mechanisms. Brain estrogen has been shown to be a key modulator of this behavior in bird and mammal species, and it remains to be understood if this is a common mechanism across vertebrates. This review focuses on the contributions of Gymnotus omarorum, the first teleost species in which estrogenic modulation of non-breeding aggression has been demonstrated. Gymnotus omarorum displays year-long aggression, which has been well characterized in the non-breeding season. In the natural habitat, territory size is independent of sex and determined by body size. During the breeding season, on the other hand, territory size no longer correlates to body size, but rather to circulating estrogens and gonadosomatic index in females, and 11-ketotestosterone in males. The hormonal mechanisms underlying non-breeding aggression have been explored in dyadic encounters in lab settings. Males and females display robust aggressive contests, whose outcome depends only on body size asymmetry. This agonistic behavior is independent of gonadal hormones and fast acting androgens. Nevertheless, it is dependent on fast acting estrogenic action, as acute aromatase blockers affect aggression engagement, intensity, and outcome. Transcriptomic profiling in the preoptic area region shows non-breeding individuals express aromatase and other steroidogenic enzyme transcripts. This teleost model reveals there is a role of brain estrogen in the control of non-breeding aggression which seems to be common among distant vertebrate species.

Do males and females respond differently to ocean acidification? An experimental study with the sea urchin Paracentrotus lividus

Seawater pH lowering, known as ocean acidification, is considered among the major threats to marine environment. In this study, post-spawning adults of the sea urchin Paracentrotus lividus were maintained at three pH values (8.0, 7.7, 7.4) for 60 days. Physiological, biochemical, cellular, behavioural and reproductive responses were evaluated in males and females. Significant differences between sexes were observed, with higher ammonia excretion and lower catalase activity in males. Respiration rate (after 21 days), catalase activity in gonads and total coelomocyte count showed the same increasing trend in males and females under low pH. Ammonia excretion, gonadosomatic index and lysozyme activity exhibited opposite responses to low pH, with an increasing trend in males and decreasing in females. Results demonstrated that exposure to low pH could result in different response strategies of male and female sea urchins at a physiological, biochemical and immunological level. Reduced female gonadosomatic index under low pH suggested decreased energy investment in reproduction.

Investigation on Endocrine Disruption of the Larval Lampricide 3-Trifluoromethyl-4-Nitrophenol: Short-Term Reproduction Assay with Fathead Minnow (Pimephales promelas).

3-Trifluoromethyl-4-nitrophenol (TFM) has been used for more than 60 yr to control the invasive parasitic sea lamprey (Petromyzon marinus) in the Great Lakes Basin (USA/Canada). In the early 1990s, researchers reported that TFM induced vitellogenin in fish and that TFM was an agonist for the rainbow trout estrogen receptor. To support continued registration of TFM for sea lamprey control, regulatory agencies required further testing to evaluate potential endocrine disruption effects. Fathead minnow (Pimephales promelas) were exposed to TFM at measured concentrations of 0.0659, 0.181, 0.594, 1.79, and 5.11 mg active ingredient (a.i.)/L for 21 d. No-observable- and lowest-observable-effect concentrations (NOEC and LOEC, respectively) were determined to be 1.79 mg/L or greater for each endpoint. Male survival in the highest treatment group was reduced relative to the controls. Percentage of egg fertility was reduced in the highest treatment group, resulting in an estimated NOEC of 1.79 mg/L. Whereas no effect on the gonadosomatic index (GSI) was observed for males, female GSI was increased in the 5.11-mg/L treatment. Vitellogenin production was not altered relative to the controls for all TFM treatment groups. However, female testosterone was elevated in the 5.11-mg/L treatment. The results suggest that prolonged exposure to TFM at concentrations exceeding 1.79 mg/L has the potential to disrupt endocrine function. Biologically relevant effects were found at the highest exposure concentration following a 21-d exposure. However, the duration of exposure in our study is not consistent with typical treatment durations (12 h) for sea lamprey control. Environ Toxicol Chem 2020;39:1599-1607. © 2020 SETAC.

Stress Responses and Gonadosomatic Index of Red Tilapia (Oreochromis Spp.) Subjected To Visual And Physical Interactions

Red tilapia is a popular cultured species due to its attractive color and excellent growth and feed conversion rates. In this study, the effect of visual and physical interactions on the ventilation rate (VR), eye color pattern (ECP), and Gonadosomatic Index (GSI) of red tilapia was evaluated. There were four treatments in the study: T1 (No Interaction); T2 (Visual Interaction); T3 (Visual and Physical Interactions) and; T4 (Physical Interaction). Changes in VR and ECP were monitored for 15 days, while GSI was computed at the end of the study. The mean VR and ECP of the red tilapia exposed to visual and/or physical interactions were significantly higher compared to those in the control (P˂0.05). However, the fastest VR and darkest ECP were observed in T3. This conforms to the results of GSI wherein T3 had the lowest GSI which may be due to the higher level of stress experienced by fish in T3 compared to other treatments. On the other hand, T4 had the highest female GSI as opposite sex fish were exposed to physical interaction. Communication between sexual partners modulates reproductive behavior.

Analysis of reproductive biology and spawning season of the pink ear emperor Lethrinus lentjan, from marine ecosystem

A total of 593 samples ofLethrinus lentjan(Lacepede, 1802) were collected from the Red Sea, Jeddah, Saudi Arabia, to study their productive biology and spawning season of the local population. Sampling was carried out on a monthly basis for a period of one year. The monthly sex ratios indicated that females were dominant throughout the study period, with an overall male:female sex ratio of 1:7.98, although males were larger than females. The highest monthly performance maturation index (PMI), as well as the male and female gonadosomatic index (GSI) and ovarian maturation rate (OMR) were observed in February and March. Histological examination of the gonads confirmed the process of sexual transformation in this fish species, wherein individuals mature first as female, and then change sex to male (protogynous hermaphroditism). Histological sections also showed that the sexual maturation of males ofL. lenjtancomprised three main stages, while the sexual development of females could be classified into four main stages. Extended spawning in the form of batches released during different months throughout the year were recorded for this fish species, with the main spawning season in February and March, and an additional, shorter spawning season in September.

Reproductive biology of the Atlantic mackerel Scomber scombrus Linnaeus, 1758 in Mediterranean coast of Sinai, Egypt.

This work aims to investigate reproductive biology of the Atlantic mackerel (Scomber scombrus L. 1758) to provide biological base for management of its fisheries in the Mediterranean coast of Sinai, Egypt. Monthly samples of S. scombrus were collected from the commercial catch in different landing sites of the Mediterranean coast of Sinai during 2019. The length-weight relation was found as W= 0.0116 L2.9556, W= 0.0077 L3.091 and W= 0.0094 L3.022715 for males, females and combined sexes respectively. Overall sex ratio (males: females) was 1: 1.4 during the period of study. Gonado- Somatic Index (GSI) of females showed that S. scombrus spawn during March, April and May, since GSI peaked in these months (6.5, 7.2 and 5.2 % respectively). The lowest value of GSI of females was recorded in October (0.05%). Lengths at first sexual maturity (Lm) were determined as 23.2 and 23.4 cm for males and females respectively. The absolute fecundity (F) was increasing with the fish length and described by a power equation: F = 0.0014 L5.6414. The relative fecundity gradually increased from 2481.8 to 7599.3 eggs per cm (average 4748.9 eggs / cm). To protect and maintain the stock of Atlantic mackerel in the Mediterranean coast of Sinai, it is recommended to ban using fishing nets of illegal mesh sizes and other destructive fishing methods which catch small fish sizes. Length at first capture should be larger than length at first sexual maturity (> 23.4 cm) and ban fishing nets targeting S. scombrus during its spawning season (from March to May).

Long‐term study of the reproductive timing of the Neotropical catfish Iheringichthys labrosus (Lütken, 1874): Influence of temperature and river discharge

AbstractUnravelling the effect of climate variability on species biology has been one of the main goals of ecological studies. Environmental factors such as river discharge and temperature have being proposed as triggers of reproductive cycle in fish. In temperate climates, fish reproduction is affected mainly by temperature, while is influenced by flood pulses in large tropical rivers. We evaluated the influence of temperature and river discharge as triggers of Iheringichthys labrosus’ reproduction. We studied the following reproductive variables: gonadosomatic index (GSI), hepatosomatic index (HSI) and condition factor (K). Females of I. labrosus were examined in a time series of ten years along three sites located in Lower Uruguay River at the beginning (last week of November‐first week of December, spring) and by the end of the reproductive period (middle‐end of April, autumn). Generalised linear models detected a positive effect of mean winter temperature and site on the spring mature female GSI. Site was significant in addition to the interaction between temperature and site. Moreover, the effect of winter temperature was stronger than water discharge in triggering reproductive timing of I. labrosus, contrary to the model proposed for other species in tropical systems. Additionally, a literature review suggested a latitudinal gradient on reproduction, occurring earlier and prolonged with decreasing latitude (and increasing temperature). In this study, we stated the effect of temperature on the life history in a Neotropical fish using a multifaceted approach, particularly important in the current context of global climate warming.

Reproductive biology and behavior associated with a spawning aggregation of the yellowfin grouper Mycteroperca venenosa in the US Virgin Islands

The reproductive characteristics, movement patterns and courtship behaviors associated with a yellowfin grouper (Mycteroperca venenosa, Linnaeus, 1758) fish spawning aggregation (FSA) were assessed between 2004 and 2014. The FSA was located on the Grammanik Bank, a seasonally closed area on the edge of the Puerto Rico platform, south of St. Thomas, US Virgin Islands. Fish arrived at the FSA site around full moon and departed 10–12 days after full moon (dafm), during two or three consecutive months, from January to May each year. Males were significantly larger than females and preceded females at the spawning site. Courtship coloration and behaviors showed distinct patterns relative to lunar date and time of day. Spawning was observed for several days each month in 2008, 2009, 2011 and 2014, from 6 to 10 dafm. Female gonadosomatic index (GSI) values were highest from 4 to 7 dafm. Spawning, which began at sunset, consisted of 7 to 12 males following one female along the bottom before ascending 10–20 m, then "rushing" upward to release gametes. Histological analysis of ovaries indicated females spawned every 2–3 nights, although 11.6% were capable of spawning two consecutive nights. Total spawning population size of yellowfin grouper fluctuated from 600 to 1100 fish during the study period, but consistent annual population assessments using scuba were difficult to carry out due to ocean conditions. Based on size-frequency analysis and other metrics, the M. venenosa spawning population at the Grammanik bank appears to be stable at this time with existing regulations.

Effects of altered photoperiod regimes during winter on growth and gonadosomatic index in Arctic charr ( Salvelinus alpinus ) reared in freshwater

The short‐ and long‐term effects of altered photoperiods during winter on growth and final gonadosomatic index (GSI) were investigated in 178 individually tagged 2‐year‐old smolt Arctic charr from an anadromous strain. The fish were reared at ambient temperature (2.3–12.5°C) for 18 months and reared at five different photoperiods. One group was reared on constant LD16:8 (light–dark, N = 40) photoperiod and a second group on continuous light (LD24:0, N = 32) throughout the experimental period. Three groups of fish were moved from LD16:8 to LD24:0 for 44 days and subsequently back to LD16:8, that is early winter light group (Early WL: 17 November–5 January; N = 35), Mid WL group (5 January–23 February; N = 38) and Late WL group (23 February–6 April; N = 33). No differences in growth were found for females, whereas males reared at constant LD24:0 were larger (mean ± SEM, 1,780 g ± 180) compared with the Late (1,264 g ± 101) and Mid WL (1,413 g ± 120) groups towards the end the study. Exposure to continuous light during early winter significantly influenced the GSI in female Arctic charr, whereas no differences were found in the males. Female GSI (%) was lowest in the Mid WL group (1.7) and highest in the LD24:0 group (7.0). In conclusion, the present study demonstrated that application of brief continuous light treatments during January and February can possibly be used as a tool to lower subsequent female maturation in Arctic charr farming.

Preliminary observations of the reproductive biology of the Frenchman seabream Polysteganus baissaci (Sparidae) from Mauritius

The Frenchman seabream Polysteganus baissaci is an important commercial fish species found on the slopes of the fishing banks of the exclusive economic zone of Mauritius. Exploitation of this species started in 2007, and it is targeted using hydraulic reels with baited hooks. The introduction of suitable management measures is important for this fishery and a sound understanding of the biology is required. Monthly biological data were collected over a 2-year period from fish landed in the commercial catch, to investigate aspects of the biology. A total of 698 females and 1 129 males (sex ratio 1:1.6) were collected from commercial fishing vessels operating on the Nazareth Bank. Females dominated smaller size classes (30–36 cm total length [TL]), whereas males were mostly present at larger sizes (37–44 cm TL). Although ripe and spent female gonads were found throughout the study period, the gonadosomatic index (GSI) revealed a peak in spawning between April and September, coinciding with the cooler sea temperatures in the region. Male GSI (0.169 [SD 0.0443]) during its peak month (August) was more than 14-times lower than the female GSI (2.470 [SD 1.0185]) during its peak month (July), and this, together with male and female length frequencies and adult sex ratios, provides strong supporting evidence for protogyny in this species. Although this fishery appears to harvest adults exclusively, which is positive in terms of sustainability, the potential hermaphroditism in this species necessitates implementation of a conservative harvest strategy, including effort limitation and a closed fishing season over the peak spawning period.

Genetic parameters of reproductive traits in male and female North African catfish, Clarias gariepinus (Burchell, 1822)

The heritability and genetic correlations for reproductive traits were estimated for North African catfish, Clarias gariepinus (Burchell, 1822) (Cg). Data were collected from 349 females at 486 days old, and 273 males at 510 days old, representing 82 full-sibs and 27–28 half-sibs, respectively. The studied traits included gonadosomatic index (GSI) of males and females, relative fecundity (number of eggs/kg-female) (RF), average egg weight (AEW), sperm concentration (SC) and percentage live sperm (LS). The heritability was low for all traits (0.0457 ± 0.0035 for female GSI, 0.0199 ± 0.0015 for RF, 0.0443 ± 0.0034 for AEW; and 0.0276 ± 0.0022 for male GSI, 0.0224 ± 0.0019 for SC, and 0 for LS). Most of genetic correlation was low among the reproductive traits (−0.18 to 0.33, irrespective of sign) except for moderate to high genetic correlation for female GSI&AEW, RF&AEW and male SC&LS. The genetic correlation values between body weight at spawning and reproductive traits were low (−0.03–0.06). The present results imply that selection to improve reproductive traits of Cg may be infeasible, and that selection to improve growth will not have detrimental effects on reproductive traits of males or females.

Factors limiting successful reproduction in wild silver carp, Hypophthalmichtys molitrix, in Kherrata Reservoir, Algeria

Abstract Silver carp, Hypophthalmichtys molitrix (Cyprinidae), is the most important freshwater fish in Algerian aquaculture. No natural spawning is observed in Algerian water bodies. This study was conducted with the aim of investigating silver carp reproduction in the wild in Algeria. This investigation can contribute tools to facilitate successful artificial reproduction. Macroscopic and histological analysis of the gonads was conducted, and the monthly distribution of maturity stages and oocyte diameters were monitored in an aggregate sample of 130 male and female silver carp, H. molitrix, (450-710 mm total length). The gonadosomatic index (GSI) ranged from 2.76 to 18.88% in females and from 0.34 to 1.85% in males. The female GSI values were the highest from June to August indicating the onset of the spawning season. The histological structures of the gonads revealed five different developmental stages in females and three stages in males. The oogenesis stages were the perinucleolar stage, the yolk vesicle stage, the primary yolk, the secondary yolk, and the tertiary yolk. Migratory nuclei and hydrated oocytes, which are considered to be the maturation stage, were not observed. Three different spermatogenesis phases (immature, maturing, and mature testis) were identified, which included final spermatozoa maturation.