GnRHa‐induced Multiple Spawns and Volition Spawning of Captive Spotted Rose Snapper,Lutjanus guttatus,at Mazatlan,Mexico

Sexual maturation and induced spawning treatments were carried out with captive spotted rose snapper, Lutjanus guttatus. A total of 3013 × 10⁶ eggs (64.7% were floating) were produced from eight treated females in 42 spawns induced with GnRHa implants during the course of the present study. GnRHa ethylene‐vinyl acetate copolymer effective doses were 204 ± 11 µg/kg in June 2005, and 224 ± 13 µg/kg in July 2005. General fertilization was 50.9 ± 34.5% and 12–14 h after spawning, viability of floating eggs was 90.4 ± 12.4%. Mean incubation period at 29–31 C was 18–20 h, and mean hatching was 94.4 ± 8.2% (73–100%). Newly hatched larvae were 2.18 ± 0.15 mm in total length (TL). One month after the last hormone experiment, previously GnRHa‐treated and untreated fish began spawning voluntarily. Hormone‐treated breeders had higher fecundity than untreated fish, producing 72.5 million eggs versus 13.9 million eggs for the untreated fish, over the following 11 mo. Combined data of volitional spawning for total egg fertilization, viability, hatching, and larval TL were 77.7 ± 1.8%, 90.3 ± 1.3%, 87.9 ± 2%, and 2.50 ± 0.12 mm, respectively. These results can ensure the sustainability of a commercial hatchery.     

Effect of water temperature on individual reproductive activity of pollack (Pollachius pollachius)

The effects of water temperature on pollack (Pollachius pollachius) spawning features were individually assessed. During the spawning period, nine fish sets, each composed of one female and two males (mean body weight: 2.5±1.0 kg), were placed in small-volume tanks (2 m³). Fish sets were held at 8, 10, or 12 °C (n=3 for each temperature).Three females released eggs at 8 and 10 °C, while only two spawned at 12 °C. One hundred thirty-one individual spawns were collected from the eight spawning fish sets. The number of spawns collected per female was significantly lower at 12 °C (3.0±3.6), compared to 10 °C (17.3±10.1) and 8 °C (23.3±2.5). Egg number (eggs kg⁻¹ BW) was significantly lowered at 12 °C (26,068±35,989) compared to 10 °C (323,230±136,796) and 8 °C (599,612±249,545). The number of viable eggs (eggs kg⁻¹ BW) was significantly lower at 12 °C (4,175±7,167) compared to 8 °C (192,034±145,870).When incubated at a common temperature of 10 °C, hatching and malformation percentages were significantly enhanced for breeders maintained at 8 °C (respectively, 35.8±8.5–7.3±1.4%) compared to 10 °C (9.8±8.0–2.3±1.8%). Then, pooling data were recorded at the three temperatures; a significant decrease of egg diameter with time was observed.The individual reproductive activity of pollack experienced by breeders was deeply affected by temperature during the spawning period. A temperature of 12 °C is suggested to be close to the temperature reproduction upper limit in this species.     

Effect of salinity on reproductive performance of Acanthopagrus latus (Houttuyn) in spawning tanks

More than 250 male and female yellowfin seabream (Acanthopagrus latus) were caught in the creeks near the Mahshar area in the north‐west of Persian Gulf using fishhooks to study the effects of salinity on reproductive indices. The experiments were carried out using three salinity treatments (30 ± 1 g L^?1, 35 ± 1 g L^?1 and 40 ± 1 g L^?1) with three replications. A total of six males and three females were randomly introduced to each tank. The survival rate of the broodstock was estimated at more than 90% at different salinity levels and the maximum rate was observed at 30 g L^?1 of the experiment rate. The percentage of buoyant eggs was more than 90% at 40 g L^?1 and it was significantly different from other treatments. The average number of eggs per female (312 914 ± 65 085), and the average number of eggs per kilogram of female (649 460 ± 173 574) at 40 g L^?1 were more than those in the other treatments but no significant differences were observed (P ≤ 0.05). The average percentage of fertilized eggs (86.7%) and the average percentage of hatched larvae (67%) at 40 g L^?1 treatment was more than those at 30 g L^?1 and 35 g L^?1 treatments but no significant differences were observed (P ≤ 0.05). At 40 g L^?1 salinity, in all spawning cases, the released eggs were hatched. Overall, the present study has shown that better buoyant eggs of A. latus can be obtained at salinity 40 g L^?1. On the other hand, the percentage of fertilized eggs and hatched larvae were not affected by salinity.     

Spawning of captive Senegal sole (Solea senegalensis) under a naturally fluctuating temperature regime

Senegal sole aquaculture is at present limited due to poor reproduction of captive breeders in many facilities. Temperature seems to play an important role in controlling reproduction of Solea senegalensis, and differences in temperature regimes followed by various hatcheries are likely to be responsible for lack of success in some of them. This work describes the reproduction of captive soles, held in facilities that used water at ambient temperature, from a marshy environment where this species naturally breeds. Acclimated sole breeders were kept for two consecutive years. The main spawning period occurred from February to May, with a secondary spawning in autumn. Total yearly fecundity ranged from 1.15×10⁶ to 1.65×10⁶ eggs kg⁻¹ body weight. Of the total egg batches produced, only 5.4% corresponded to autumn spawns. The male population was found to produce sperm all year round, with a maximum proportion of 100% occurring in spring, and a minimum proportion of around 50% in summer. Females showed the more developed ovary stages from October to May, with partial regression in the summer months. During the main spawning period, eggs were produced between 46% and 69% of days.Spawning took place at temperatures from 13 to 23 °C, although higher fecundities (P<0.05) occurred between 15 and 21 °C. Within the range between 17 and 20 °C, the mean number of spawned eggs was 29,600±21,600 eggs day⁻¹ kg⁻¹. Most of the eggs (65–73%) were produced after temperature increased up to 2.5 °C within 3 days prior to spawning. Mean egg fertilization was 63.1±17% (year 2002) and 44.9±18% (year 2003), and hatching rates varied from 69.7±24% (2002) to 56.5 ±25% (2003). Weak correlations were found between either fertilization or hatching and fecundity, whereas a positive regression (P<0.05) indicated that higher hatching rates were achieved when fertilization increased. A weak, but significantly (P<0.05) positive correlation was found between egg fertilization and the spawning temperature. Present results indicate temperature is an important control factor for reproduction of S. senegalensis, and suggest it can be used to properly manage controlled captive reproduction of this species.     

First results on spawning, larval rearing and growth of the wedge sole (Dicologoglossa cuneata) in captivity, a candidate species for aquaculture

The wedge sole is a target species in the fisheries of the Gulf of Cadiz (Spain). Having reared them to commercial size, we have studied reproduction and breeding in captivity of the wedge sole in this work here. The breeders adapt easily to captivity, and they can spawn in less than 1 year in captivity. The relative fecundity is relatively high, 1.06–2.33 · 10⁶ eggs kg⁻¹ per spawning season (mean 1.6 ± 0.1). Larval SGR is high, 7.2 ± 0.2% day⁻¹ (range 5.8–9.1), similar to other cultured flatfish species. In 1 year, some individuals reach market size and can release eggs, registering SGRs of 1.39–1.66% day⁻¹ (mean 1.56 ± 0.01). This species presents some very different characteristics with respect to other farmed flatfishes (turbot, halibut and Senegal sole, mainly), so that it is necessary to develop new techniques to optimise its cultivation. In the present work, the first results are presented on the biology of the wedge sole in captivity.     

Spawning and Development of Larvae and Juveniles of the Rare Blue Mauritius Angelfish,Centropyge debelius (1988), in the Hatchery

This study documents the rearing and life history stages of the rare blue Mauritius angelfish, Centropyge debelius, from spawning of eggs through sexual maturity. A C. debelius pair was maintained at our facility for 22 mo. The pair was conditioned to spawn for a 4‐mo period in the fall of 2005 and a 4‐mo period in the summer of 2006 using water temperature and photoperiod manipulation. Continuous spawning was achieved at water temperatures between 22 and 24 C and a photoperiod of long day (LD) 13.5:10.5. Over a 124‐d period, the female produced 97 spawns, 59% of which resulted in fertile eggs. The average fecundity per spawn was 237 eggs (range 13–813 eggs). Fertility of all preserved spawns averaged 19.0 ± 19.8%. Larval rearing attempts using wild caught zooplankton and Artemia nauplii resulted in a total of 10 C. debelius juveniles raised through metamorphosis with an average larval survival up through metamorphosis of 0.36%. Three resulting juveniles were raised through sexual maturity. Sexual dichromatism was first observed about 180 d posthatch. A statistical model: Y = (X× 0.32437) ? (X²× 0.00043) ? 2.004, where Y = total length (mm) and X = number of days in culture, explained 97.6% of the variation in growth (P < 0.001, R² = 0.976). The development of eggs and larvae was observed to be similar to that of other Centropyge species that have been cultured. Results of this study indicate that the artificial propagation of C. debelius is technically feasible and forms the basis for this report.     

The effect of male absence on the larval production of the spider crab Maja brachydactyla Balss, 1922

The spider crab Maja brachydactyla, Balss 1922 can produce three consecutive broods per breeding season in the wild, whereas females in captivity can spawn up to four times in the absence of males. The effect of male absence on the larval production of the spider crab M. brachydactyla was studied in a 2‐year experiment in which females were kept in captivity in the presence or absence of males. The broodstock were maintained under natural photoperiod conditions, temperature (18.5 ± 1.0°C) and salinity (34.8 ± 0.7 g L^?1). The number of larvae, and when possible, the dry weight and proximate biochemical composition of each larval batch were calculated and the data grouped seasonally. The larval production (P < 0.001) and protein content (P = 0.037) were significantly lower in the absence of males. However, considering that the larval production in male presence decreased due to the low female survival rate, particularly in the last part of the experiment, the presence of males should be managed to maintain a high larval production and condition without jeopardizing the survival of females. Therefore, we recommend keeping females segregated from males and transferring males to female tanks only to mate.     

Optimal temperature and photoperiod for the spawning of blue crab,Callinectes sapidus,in captivity

Like all poikilotherms, the growth and reproduction of blue crab, Callinectes sapidus depends on temperature and season. Warmer water temperatures in the Chesapeake Bay allow for ovarian development and spawning, while colder water temperatures slow their metabolism and reproduction. The current study aimed to identify optimal environmental conditions for inducing reproduction in animals held in long‐term captivity for year round production in aquaculture through environmental manipulations. Temperature and photoperiod were the main environmental factors tested for 25 weeks: 11°C and 21°C, with the following photoperiods: 0L:24D, 8L:16D, 16L:8D and 24L:0D. At 21°C, the females increased spawning frequency, which was arrested at 11°C. Shorter light exposure at 21°C increased spawning frequency, while constant light inhibited and did not produce spawning. Constant dark (0L:24D) at 21°C produced the most (86%) spawns, but yielded poor larval quality. At 21°C with all photoperiod conditions except constant light, the first spawning took 94.8 ± 32.4 days to occur (n = 17). With females producing multiple spawns, the intervals between the first and second spawns and the second and third spawns were 37.7 ± 8.7 days (n = 6) and 31.0 ± 7.1 days (n = 2) respectively. Analysis of our data using response surface methodology (RSM) predicts the following conditions: at 15–19°C and 0–10 hr darkness for maximal survival and at 19–22°C and 0–8 hr darkness for spawning. The number of larvae produced was positively correlated with size (weight) of the female C. sapidus, suggesting the importance of female size in reproduction.     

Spawning induction and seed production of Eastern little tuna,Euthynnus affinis (Cantor, 1849), in the post‐ and pre‐spawning seasons by hormonal treatment in a semi‐closed recirculation system with elevated temperature

We previously established a method for spawning induction in Eastern little tuna (ELT) Euthynnus affinis (Cantor, 1849) by administering a gonadotropin‐releasing hormone analog (GnRHa) during the natural spawning season in Japan (August–October). In order to establish seed production of ELT in the off‐spawning season, we first conducted three spawning induction trials by GnRHa administration from October 2011 to January 2012 using ELT broodstock (2 years old; three females and four males) maintained in a 10‐m³ tank with a semi‐closed recirculation system and static elevated temperature. Average water temperature and daily egg production in three trials lasting 11–15 days were 27.0 ± 0.09°C and 268 173 eggs (Trial 1), 27.0 ± 0.11°C and 277 9098 eggs (Trial 2), and 25.5 ± 0.39°C and 291 113 eggs (Trial 3) respectively. Mean fertilization rate and mean hatching rate were 70.4% and 60.5% (Trial 1), 83.9% and 79.6% (Trial 2), and 62.5% and 57.4% (Trial 3) respectively. We also succeeded in producing ELT larvae in the pre‐spawning season (April–July), although the quantity and quality of larvae produced were inferior to those produced in other calendar months. In trials involving periodic GnRHa administration during the off‐spawning seasons, hatched larvae were obtained in the 10‐m³ tank after six of nine administrations in the 2011–2012 off‐spawning season and in 16 of 19 administrations in the 2012–2013 off‐spawning season. The findings of this study demonstrated that hormonal treatment and thermal control could be used to extend the spawning period in ELT, potentially allowing larval production in the post‐ and pre‐spawning seasons.     

Spawning behaviour,early development and first feeding of the bluestriped angelfish [Chaetodontoplus septentrionalis (Temminck & Schlegel, 1844)] in captivity

Successful natural spawning of Chaetodontoplus septentrionalis in captivity from 19 March to 11 May, 2008 is described for the first time. A single male dominates a harem of two females, spawning with each at dusk, from 10 min before to 20 min after sunset. Each female laid an average 119 × 10³ eggs during the spawning period. Fertilized eggs were spherical, buoyant and had a diameter of 0.83 ± 0.02 mm (mean ± SD). Embryonic development lasted 15–18 h at 28.1 °C. Newly hatched larvae were 1.60 ± 0.07 mm in total length (TL) with 27 myomeres. Larvae completed yolk absorption within 3 days post hatching (ph) at 3.01 ± 0.08 mm TL. Ten days ph, the larvae had attained 3.95 ± 0.12 mm TL. Larvae were fed either 100% s‐type rotifers (Brachionus rotundiformis), 100% copepods (Microsetella sp.), a combination of the two (50%:50%) or without live feed (starved control) to determine the effect of live feed on the survival rate. The survival was significantly (P<0.001) higher in larvae fed a combination of diet than the others. These results indicate that C. septentrionalis is a potential species for captive breeding programs and the use of a combination of diet (s‐type rotifers and copepods) may be a suitable first food for the larvae.     

Efficacy of 17 α‐methyl testosterone and letrozole on sex reversal of protogynous grouper,Epinephelus tauvina (Forskal, 1775) and spawning performance of sex‐reversed males

This study aimed to test the efficacy of 17 α‐methyl testosterone (17 α‐MT) alone and in combination with letrozole, an aromatase inhibitor, for the induction of sex reversal in protogynous greasy grouper, Epinephelus tauvina. Further, the long‐lasting effects of these treatments and spawning performance of sex‐reversed males were also investigated. Greasy grouper with oocytes in the perinucleolus stage were implanted with 5 mg 17 α‐MT kg^?1 body weight (T₁), 5 mg 17 α‐MT and 0.2 mg letrozole kg^?1 body weight (T₂) and 5 mg 17 α‐MT with 0.4 mg letrozole kg^?1 body weight (T₃) and no androgens/enzyme inhibitor implanted (C). The 17 α‐MT alone and in combination of letrozole‐induced sex reversal in greasy grouper, whereas untreated control fish (C) showed normal ovarian development. However, T₂ and T₃ group showed 100% sex reversal and completion of spermatogenesis up to functional male phase in 2 and 3 months, respectively, whereas T₁ group resulted in only 66.67% functional male with motile spermatozoa after 4 months. Sex‐reversed males successfully fertilized the eggs during induced spawning. There were significant differences on fertilization and hatching rates between T₂ group (79.00 ± 4.36%; 77.67 ± 2.87%, respectively) and T₁ group (57.67 ± 3.17%; 63.87 ± 2.91%, respectively). The result suggested that 17 α‐MT (5.0 mg kg^?1 BW) in combination with letrozole (0.2 mg kg^?1 BW) has the potential to produce 100% sex‐reversed male in short period in greasy grouper, which might greatly help in seed production of greasy grouper.     

Fertilization by refrigerator stored sperm of the Indian major carp, Labeo calbasu (Hamilton, 1822)

This study reports on the spermatological properties, and on the development of a protocol for refrigerator storage (4°C) of Labeo calbasu (Hamilton, 1822) sperm for artificial breeding. Volume, motility, concentration and pH of the freshly collected sperm were 2.21 ± 0.53 (μL g^?1 of fish weight) (mean ± SD), 95 ± 1 (%), 1.93 ± 0.44 × 10⁹ (cells mL^?1) and 7.56 ± 0.17 respectively. Sperm activation was evaluated at different osmolalities of NaCl solution, and motility ceased completely when osmolality of the extender was ≥287 mOsmol kg^?1. Sperm retained motility for 24, 72 and 108 h, after refrigerator storage when sperm were undiluted, suspended in Alsever's solution and suspended in Alsever's solution containing 5% methanol respectively. Fertilization rate of fresh eggs with sperm stored at 4°C in Alsever's solution and Alsever's solution containing 5% methanol was 77% and 60% with a hatching rate of 60% and 43% respectively. The fertilization and hatching success of the stored sperm suggests potential to use refrigeration for transporting genetic material to hatcheries for artificial breeding of L. calbasu in Bangladesh.     

On the breeding behaviour and reproduction of the freshwater prawn,Macrobrachium rosenbergii (de Man 1879) (Decapoda‐Crustacea) under laboratory conditions

The giant freshwater prawn, Macrobrachium rosenbergii is one of the most common decapod species, and now getting more attention from the aquaculturists world wide due to its high market demand. It is commercially important because of its size as well as its eating flesh qualities. The breeding behaviour, reproduction and hatching of this species were observed for about 8 months during 2009. Juveniles (0.55 ± 0.177 g total weight and 2.7 ± 0.12 cm, total length) were reared in rounded fibre glass tanks (1.3 m, diameter). Pre‐mating moult occurs in prawns once the ovaries ripen in their carapace cavity so as to transform the prawn into berried stage. Recorded incubation period ranged from 18 to 24 days. The number of eggs ranged from 2050 to 150 500 and the fecundity ranged from 435.2 to 3849.1 eggs. Number of hatched larvae ranged from 1825 to 123 410 larvae for females of 4.71 to 39.1 g respectively. The number of eggs carried by female prawn was directly proportional to its body weight (no. of eggs = 3441.3 wt. of female – 32 292, r² = 0.819). (fecundity = 82.066 wt. of female ? 235.04, r² = 0.7779; fecundity = 317.86 length of female ? 2651, r² = 0.833). Hatching rate ranged from 65% to 91%, and there was a correlation between number of hatched larvae and size of female parent (no. of larvae = 10 369 length of female – 102 965, r² = 0.8159; no. of larvae = 2792.9 wt. of female – 26 268, r² = 0.829). This study can greatly help in the management strategies of prawn hatcheries and improve its hatching technology.     

Reproductive performance in induced and spontaneous spawning of the mangrove red snapper, Lutjanus argentimaculatus: a potential candidate species for sustainable aquaculture

A reliable breeding technique was developed for the mangrove red snapper, Lutjanus argentimaculatus (Forsskal 1775), to help sustain the aquaculture of this immensely popular species in Southeast Asia. Using standardized indices of female maturity (based on mean oocyte diameter of ≥0.40 mm), time of injection (1000–1130) and sex ratio (one female to two males), a single injection of 100 μg kg^?1 luteinizing hormone‐releasing hormone analogue (LHRHa) (n=16 fish), but not 50 μg kg^?1 (n=five fish), successfully induced egg (62.5% success rate) and larval (43.8%) production. Human chorionic gonadotropin (hCG) at 500 IU kg^?1 (n=five fish) also failed to induce spawning, but doses of 1000 (n=22 fish) and 1500 IU kg^?1 (n=15 fish) gave spawning (77.3% and 80.0% respectively) and hatching success rates (72.7% and 60.0% respectively) that were not significantly different from those of 100 μg kg^?1 LHRHa. No spawning was observed in saline‐injected controls (n=seven fish). While mean spawning latency, egg diameter, egg production per spawn, percent egg viability, hatching rate, percent of normal larvae and cumulative survival of eggs to normal larvae did not differ significantly among the effective hormones and doses, 1000 IU kg^?1 hCG had a higher percentage (76.5%) of total spawns with egg production per spawn in excess of one million than those of 1500 IU kg^?1 hCG (50.0%) and 100 μg kg^?1 LHRHa (40.0%). Mangrove red snapper spontaneously spawned from March–April to November–December with a peak of egg collection and spawning in May–June. Egg collection per spawn ranged from 0.05 to 6.35 million. Spontaneous spawning of mangrove red snapper exhibited lunar periodicity with spawns mostly occurring 3 days before or after the last quarter and new moon phases and occurred consistently between 02:00 and 04:00 hours. High fecundity and good egg quality, coupled with the ability to respond to induce spawning or natural spawning in captivity, provide a sound basis for improving the sustainability of red snapper aquaculture in Southeast Asia.     

The effects of salinity on reproductive performance and plasma levels of sex steroids in Caspian kutum Rutilus frisii kutum

Sexually mature kutum, Rutilus frisii kutum, captured from its natural habits, the Caspian Sea and the Khoushkrood River, reared at 0.5 g L^?1 and 8–13 g L^?1 for approximately 1 year in experimental condition, for assessing the effect of salinity on reproduction. Plasma concentrations of sex steroid hormones (17β‐estradiol, testosterone and 17α‐hydroxyprogestrone) were measured in the three stages of gametogenesis. Female kutum held at <0.5 g L^?1 or 8–13 g L^?1 had no ovulated oocytes in their ovaries. In contrast, males held in captivity were spermiated, similar to their wild counterparts. The average sperm volume of males held at <0.5 g L^?1 (2.36 ± 0.46 mL) was lower than males held at 8–13 g L^?1 (3.65 ± 0.73 mL) at the end of the experimental period. The highest concentration of testosterone was observed in mid‐gametogenesis in wild fish that was significantly higher than the concentration seen in fish held in either <0.5 g L^?1 or 8–13 g L^?1. Female kutum showed suppressed steroid hormones in captivity, resulting in failure in the gonad development. However, male kutum adapt well to captivity and showed synchrony in steroid hormone variations with the wild fish, resulting in the testicular development. Results of this study also indicate that salinity plays a minor, but vital, role in reproduction of kutum, a factor that needs to be considered for keeping broodstock of brackish water fish species like kutum.     

First results of spawning and larval rearing of longfin yellowtail Seriola rivoliana as a fast‐growing candidate for European marine finfish aquaculture diversification

The present study describes the adaptation of longfin yellowtail Seriola rivoliana as broodstock and first larval rearing trials under intensive and semi‐intensive conditions. Fifteen sub‐adults were captured in the South coast of Gran Canaria (Canary Islands, Spain) in June 2007. Fish (initial weight 1.76 ± 0.25 kg) reached a weight of 6.0 ± 1.1 kg in July 2010. Once a year, fish were sampled to determine individual growth in weight and size. In addition, the state of sexual maturity was established based on gonadal biopsies. On the basis of repeated hormonal injection (GnRHa, 20 μg/kg), 10 successful spawns were obtained between July and October 2009, with 92.5 ± 5.5% and 72.6 ± 17.2%, fertilization and egg viability respectively. First results of larval rearing under semi‐intensive conditions, showed an average survival at 30 DAH of 2.5% as compared with 0.5% under intensive conditions. The low survivals under the two rearing conditions in addition to their failure to pass a stress test could be attributed to deficiencies in essential fatty acids as could be seen in both eggs and feeds. Morphometric parameters showed no significant difference between the two rearing systems in 230 DAH larvae.     

Effect of lipid levels on reproductive performance of Oreochromis karongae

A study was conducted at Bunda Fish Farm to evaluate the effects of dietary lipid levels on reproductive performance of Oreochromis karongae. Fish were reared in 12 hapas for 86 days, with four experimental diets containing 8.28%, 10.17%, 12.09% and 14.05% levels of lipid, replicated three times. At the end of the experiment, O. karongae fed 10.17% and 12.09% lipid had the highest absolute fecundity (237.5 ± 6.50 and 271.3 ± 26.19, respectively) as compared with fish fed on 8.28% and 14.05% lipid levels (90.3 ± 46.3 and 143.7 ± 30.8 respectively). Higher number of spawns (5) were observed in fish fed on diets containing crude lipid of 10.17%. We can assume also that diets of 10.17% lipid are not costly as those of 12.09% or 14.05% lipid. It was found that the size of eggs depended on the number of eggs spawned by the female fish, as the number of eggs increased, the weight of eggs and mean egg diameter decreased. There were no significant differences (P > 0.05) among treatments in terms of relative fecundity. Based on these findings, it is recommended that diets containing crude lipid of 10% should be fed to broodstock for optimum reproductive performance of O. karongae.     

Effects of supplementary fennel (Foeniculum vulgare) essential oil in diet on growth and reproductive performance of the ornamental fish,Convict cichlid (Cichlasoma nigrofasciatum)

This study evaluated the effects of diet containing 0 (C: control), 75 (D₁), 100 (D₂), 125 (D₃) and 150 (D₄) mg kg^?1 F. vulgare essential oil on growth and reproductive performance of C. nigrofasciatum. A total of 225 Convict cichlids female with mean weight (1.65 ± 0.02 g) were distributed into 15 glass aquaria (15 fish tank^?1) in triplicate treatments. During 40 days of experimental period, fish fed at 3% of their body weight daily. At the end of experiment, growth indices, gonadosomatic index and reproductive indices were determined. The best feed conversion ratio was obtained in D₄ (1.19 ± 0.03, P < 0.05). The addition of F. vulgare essential oil did not have any statistical effects on other growth indices (specific growth rate, weight gain and condition factor). Total survival rates in all treatments and control were uniformly high, ranging from 93% to 97% (P > 0.05). F. vulgare essential oil has no negative effect on survival rate of C. nigrofasciatum. There were no significant differences among protein content of fish body (P > 0.05). The lowest value of fat content (26.5 ± 0.5%) was observed in D_2, and it had significant difference with control and other groups (P < 0.05). The ash percentage in treatments fed with F. vulgare essential oil were higher than control fish (P < 0.05). The highest moisture content was detected in D₄ (72.68 ± 0.19%) and D₂ (71.23 ± 2%) groups. Among the used dosage, D₄ was the most effective dosage that could significantly increase GSI (11.06 ± 1.55%), fecundity (340 ± 21) and hatching ratio (92.33 ± 1.63%). There were no significant differences in diameter of eggs among various treatments (P > 0.05).     

Hormone-induced ovulation, natural spawning and larviculture of Brazilian flounder Paralichthys orbignyanus (Valenciennes, 1839)

Mature Brazilian flounders Paralichthys orbignyanus were captured in coastal southern Brazil and their reproduction in captivity was studied. Brazilian flounder will spawn naturally in captivity when the water temperature is around 23 °C and 14 h of light is provided daily. Females were induced for ovulation and hand stripping using human chorionic gonadotropin, luteinizing hormone‐releasing hormone analogue or carp pituitary extract. There was no need to inject males, as running milt was observed during the spawning season. Fertilization and hatching rates were above 80% independent of the hormone used. Notochord length at hatching was 2.18±0.07 mm for larvae hatching from naturally spawned eggs. Larvae were reared in salt water (30–35 g L^?1) at 24 °C and under continuous illumination. Larviculture was with green water (Tetraselmis tetrathele 50 × 10⁴ cells mL^?1). Rotifers (10–20 ind mL^?1) were offered as first food 3 days after hatching and gradually replaced by Artemia nauplii (0.5–10 ind mL^?1). Larvae settled to the bottom 20 days after hatching and completed metamorphosis within a week after that. The total length for newly metamorphosed juveniles was 12.9±2.2 mm and the mean survival was 44.8%. The results demonstrate the feasibility of producing Brazilian flounder fingerlings for stock enhancement or grow‐out purposes.