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.     

Induced spawning in bream, Abramis brama (L.), using carp and bream pituitary extract and hCG

Induced spawning in bream, Abramis brama (L), was studied using acetone-dried common carp pituitary (CP) and bream pituitary (BP) with or without the addition of human chorionic gonadotrophin (hCG). The total dose administered to fish was of 5.0 mg kg^?1 BP or 4.0 mg kg^?1 CP with or without 2000-2200 IU hCG kg^?1 for females and 2.5 mg kg^?1 BP or 2.0 mg kg^?1 CP with or without 1000–1100 IU HCG kg^?1 for males. In all male treated groups 100% of spermiation was observed: in females the most effective method was a triple injection with hCG and carp pituitary, resulting in 79% of females ovulated (over 68% of eyed eggs). Biological quality of eggs, expressed as a percentage of eyed eggs, was negatively correlated with time elapsing between resolving (final) injection and ovulation. Spawning success, expressed as a value of S_e (spawning effectiveness coefficient), was higher in fish treated with triple injection.     

Dietary isoleucine requirement of juvenile blunt snout bream,Megalobrama amblycephala

A 9‐week feeding trial was conducted to estimate the dietary isoleucine requirement of juvenile blunt snout bream. Six isonitrogenous and isoenergetic experimental diets were formulated to contain graded isoleucine levels ranging from 5.3 to 20.1 g kg^?1 dry diet. At the end of the experiment, weight gain (WG), specific growth rate (SGR), feed efficiency ratio (FER) and protein efficiency ratio (PER) increased with increasing dietary isoleucine level up to 11.1 g kg^?1 dry diet, and dietary isoleucine level above 14.2 g kg^?1 dry diet declined these performances. Dietary isoleucine levels (14.2 and 17.3 g kg^?1 dry diet) significantly improved whole‐body protein content, but decreased whole‐body lipid, plasma triglyceride and cholesterol contents. Significantly lower visceral fat index (VFI) in fish fed with 14.2 g kg^?1 dietary isoleucine was observed compared to those fed with deficient or excessive isoleucine. Dietary isoleucine supplementation significantly increased plasma isoleucine concentration, while plasma valine and leucine concentrations showed a reversed trend. Dietary isoleucine levels regulated the target of rapamycin (TOR) gene expression and improved plasma superoxide dismutase (SOD) activity in juvenile blunt snout bream. Based on second‐order polynomial regression model analysis of SGR and FER, the optimum dietary isoleucine requirement was estimated to be 13.8 g kg^?1 dry diet (40.6 g kg^?1 dietary protein) and 14.0 g kg^?1 dry diet (41.2 g kg^?1 dietary protein), respectively.     

Changes in free amino acid profile of red snapper <Emphasis Type="Italic">Lutjanus campechanus</Emphasis>, eggs,and developing larvae

The free amino acids (FAA) profile was determined for newly fertilized eggs and resultant larvae from wild-caught red snapper Lutjanus campechanus induced to spawn with hCG. Yolk sac and oil globule volumes of eggs and larvae were monitored over time from digital photographs. FAA profiles of the eggs and larvae were measured in picomoles (pmol) of FAA/mg of eggs by HPLC. Newly fertilized eggs had a mean total FAA content of 21.72 ± 3.55 nmoles/egg (92.81 ± 9.71 nmoles/mg eggs). Leucine, valine, lysine, and isoleucine were the most abundant essential FAA comprising 35.9% of the total FAA. Alanine, serine, asparagine, and glycine were the most abundant non-essential FAA comprising 34.2% of the total FAA. At 24 h post-hatch (hph) the mean total FAA had decreased by 81% since egg fertilization. The bulk of the FAA decrease was between the time of hatch and 12 hph. Only 8.5 ± 1.5% of the initial concentration in fertilized eggs of isoleucine, 9.7 ± 2.5% of arginine, and 9.9 ± 2.0% of threonine remained at 12 hph. Among the non-essential FAA, alanine dropped the most by 12 hph with 4.6% of the concentration found in a recently fertilized egg remaining, while cysteine had increased 254.7 ± 26.2%. The yolk sac volume decreased rapidly in the first 12 hph and was further reduced 77.0 ± 2.5% from 12 to 24 hph. The oil globule depletion rate was a more linear decline from fertilized egg to 36 hph.     

Evaluation of tuna by‐product meal as a protein source in feeds for juvenile spotted rose snapper Lutjanus guttatus

This study evaluated the use of tuna by‐product meal (TBM), a locally produced feed ingredient, as a replacement for fish meal (FM) in diets for spotted rose snapper, Lutjanus guttatus. Six isonitrogenous compounds [480 kg^?1 crude protein (CP) and isoenergetic diets (21 kJ g^?1)] were formulated to replace 0 (D‐0%), 10 (D‐10%), 20 (D‐20%), 30 (D‐30%), 40 (D‐40% or 50% (D‐50%) of FM protein with TBM protein. Each diet was fed to four replicate groups of spotted rose snapper (initial weight 5.4 g ± 0.04 g) to apparent satiation three times a day. After 8 weeks of feeding, the fish gained 4–5 times their initial weight. Spotted rose snapper fed D‐30% had a significantly higher specific growth rate (2.7% day^?1) than fish fed the other diets containing lower or higher amounts of TBM. Haematological parameters and whole‐body proximate composition were unaffected by diet (P > 0.05). The ADC for protein and energy in D‐0%, D‐20% and D‐30% were significantly higher than those for the D‐40% and D‐50% groups. A broken line model indicated that 262 g kg^?1 TBM in the diet would yield maximum growth of the spotted rose snapper. The results of this study demonstrate that TBM is an acceptable ingredient for replacing 25–30% of dietary protein from FM in spotted rose snapper diets but that higher replacement levels reduce fish performance.     

Hormonal induction of ovulation in pikeperch (Sander lucioperca L.) using human chorionic gonadotropin (hCG) and mammalian GnRH analogue

The aim of the present study was to study spawning stimulation in artificial reproduction of females pikeperch (Sander lucioperca L.) using “Chorulon” containing the human chorionic gonadotropin (hCG) and compare with “Supergestran” containing a mammalian GnRH ([D-Ala⁶]GnRHProNhet) analogue. The females were divided into eleven experimental groups and injected with hCG at 250, 500, 750, and 1 000 IU kg^?1 body weight (BW) and mGnRHa at 1, 2.5, 5, 10, 25, and 50 μg kg^?1 BW. In all treatments, a single intramuscular injection of hormone was performed. Control group was injected with 0.9 % NaCl, 0.9 cm³ kg^?1 BW. The average percentages of ovulating females were 88.5 ± 12.3 and 80.8 ± 10.9 % in hCG- and mGnRHa-treated groups, respectively. The average diameter of eggs was 0.95 ± 0.06 and 0.98 ± 0.06 mm in hCG- and mGnRHa-treated groups, respectively. Neither ovulation rate nor diameter of egg was statistically differed among hormonally treated groups. Statistical difference was observed only in hatching rate, where the average were 73.6 ± 14.4 and 50.6 ± 17.7 % in hCG and mGnRHa-treated groups, respectively. Among hormonally treated groups, the best results were observed in groups treated with hCG at 500 and 750 IU kg^?1 and in groups treated with mGnRHa at 25 μg kg^?1. No ovulation was observed in the control group. This study indicated successful ovulation in pikeperch using a single intramuscular injection of hCG or mGnRHa analogue.     

Dietary leucine requirement of Juvenile Nile tilapia,Oreochromis niloticus

An 8‐week feeding trial was conducted to evaluate the effects of dietary leucine on growth performance, feed utilization, body composition and non‐specific immune responses of juvenile Nile tilapia. Five isonitrogenous and isoenergetic diets were formulated to contain graded levels of L‐leucine (5.3, 8.1, 10.9, 13.2, 15.6 and 18.1 g kg^?1 diet, respectively) from dietary ingredients and crystalline L‐leucine. Each diet was randomly assigned to triplicate groups of 20 juvenile fish (1.94 ± 0.01 g) three times daily to apparent satiation. Results showed that the weight gain (WG) and specific growth rate (SGR) increased as dietary leucine concentrations increased from 5.3 to 13.2 g kg^?1 and then decreased slightly with further increase in dietary leucine concentrations. Quadratic regression analysis (y = ?522.6x² + 1304.x + 132.6, R² = 0.684) on weight gain against dietary leucine levels indicated that the optimal dietary leucine requirement was estimated to be 12.5 g kg^?1 diet (corresponding to 43.1 g kg^?1 of dietary protein). Leucine supplementation had no impact on the survival and body composition of tilapia. Serum lysozyme activity of fish fed diet containing 13.2 g kg^?1 leucine significantly increased compared to fish fed diet containing 5.3 g kg^?1. Serum superoxide dismutase activity and immunoglobulin M (IgM) concentration were not significantly affected by dietary leucine supplementation.     

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.     

Induction of ovulation in ornamental common carp (Koi, Cyprinus carpio L.) using LHRHa ([d-Ser(tBu)6, Pro9-NEt]-LHRH) combined with haloperidol and carp pituitary extract

The effects of a single injection of mammalian superactive analogue [d ‐Ser(tBu)⁶,Pro⁹‐NEt]‐LHRHa (20 μg/ kg^?1) combined with the dopamine antagonist, haloperidol (HAL, 0.5 mg kg^?1), for induction of ovulation in the koi carp broodstocks were determined under routine hatchery conditions. The results were compared with classic carp pituitary extract (CPE, double injection) application (water temperature 22 °C). Physiological saline (0.7% NaCl)‐injected fish were used as a control group and no ovulation occurred in this group. The spawning ratio was high in the LHRHa+HAL treatment group and in the CPE treatment group (6/7 and 5/7 respectively). The latency period was 14–16 h in the LHRHa+HAL treatment group and 12–14 h in the CPE treatment group (after the second injection). There was no difference between the two ovulating groups with respect to the spawning index (the weight of eggs as a percentage of female body weight) and fertilization rate of eggs (P>0.05). As a result, ovulation can be induced successfully in koi carp broodstocks with 20 μg kg^?1 [d ‐Ser(tBu)⁶,Pro⁹‐NEt]‐LHRHa+0.5 mg kg^?1 HAL treatment in a single injection without decreasing the egg quality. Application of this combination can be useful for hatchery and broodstock management in koi carp culture.     

Quantitative dietary leucine requirement of juvenile Pacific white shrimp,Litopenaeus vannamei (Boone) reared in low‐salinity water

The experiment was conducted to determine the leucine requirement of juvenile Pacific white shrimp Litopenaeus vannamei (Boone) in low‐salinity water (0.50–1.20 g L^?1). Six diets were formulated to contain 410 g kg^?1 crude protein with fish meal, peanut meal and precoated crystalline amino acids with different concentration of l ‐leucine (16.72, 19.60, 22.06, 24.79, 27.28 and 30.16 g kg^?1 dry diet). Each diet was randomly assigned to triplicate groups of 30 shrimps (0.38 ± 0.002 g), and the feed trial lasted for 8 weeks. The results indicated that the maximum weight gain was observed at 24.95 g kg^?1 dietary leucine group, whereas the diets containing higher leucine concentration conversely reduced the growth performance (P < 0.05). Moreover, the highest body protein content and body protein deposition and the lowest haemolymph AST and ALT activities were also found at 24.95 g kg^?1 dietary leucine group. With the increase in leucine in diets, a dose‐dependent increase was found in body lipid content and haemolymph urea concentration. The polynomial regression calculated using weight gain, feed efficiency and body protein deposition indicated that the optimal dietary leucine requirement for L. vannamei reared in low‐salinity water was 23.73 g kg^?1 leucine of dry diet, correspondingly 57.88 g kg^?1 of dietary protein.     

Dietary taurine improves reproductive performance of Nile tilapia (Oreochromis niloticus) broodstock

This study was conducted to evaluate the effects of supplemental taurine on reproductive performance of Nile tilapia (Oreochromis niloticus) broodstock fed soybean meal‐based diets. Four isonitrogenous (350 g kg^?1 protein), isocaloric (18 MJ kg^?1) diets were formulated to contain 0, 5, 10 and 15 g kg^?1 taurine. The diets were fed to triplicate groups of juvenile Nile tilapia (10–15 g average body weight) at a female: male ratio of 3 : 1, to apparent satiation, three times per day for 130 days. The size at first maturation decreased with increasing dietary taurine to 10 g kg^?1 and levelled off with further taurine supplementation. The time to first spawning was also significantly shorter at 10 g kg^?1 taurine level. Spawning performances, including spawning frequencies, total number of spawnings per tank, number of spawnings per female and absolute fecundity, were all significantly improved with increasing dietary taurine up to 10 g kg^?1. However, the quadratic regression analyses indicated that the maximum spawning performance occurred at 8 g kg^?1 of supplemental taurine. Eggs produced from broodstock fed 10 g kg^?1 taurine exhibited significantly higher hatchability and required shorter time for hatching and yolk‐sac absorption and also resulted in higher larval weight than at other dietary taurine levels. The highest egg protein, total amino acids and taurine were also obtained at 10 g kg^?1 taurine. These results suggest that 8 g kg^?1 dietary taurine is required for optimum reproductive outputs of Nile tilapia broodstock.     

Synchronization of ovulation in cultured northern whitefish (Coregonus peled,Gmelin 1788) using [D‐Arg6Pro9Net]‐sGnRH analogue and its effect on egg quality

Female northern whitefish were treated with salmon [D‐Arg⁶Pro⁹Net]‐sGnRHa emulsified in Freund′s incomplete adjuvant as a sustained release treatment (sGnRHa‐FIA) or with [D‐Arg⁶Pro⁹Net]‐sGnRHa dissolved in physiological saline as acute release treatment (sGnRHa‐PS). Females in four experimental groups (A, B, C, D) and one control group (E) were injected intraperitoneally as follows: A and B – sGnRHa‐FIA at doses of 50 and 25 μg kg^?1, respectively; C – double injection (DI) of sGnRHa‐PS at 25 μg kg^?1 administered 3 days apart; D – single injection (SI) of sGnRHa‐PS at 25 μg kg^?1; and E – control group receiving a 1:1 mixture of FIA and physiological saline. All treatments induced and synchronized ovulation. Mean time to ovulation was significantly reduced (P < 0.05) in GnRHa‐treated groups compared with control. Hormone treatments did not affect the relative fecundity. Slight differences were found in ovarian fluid pH between group A and D (P < 0.05). Except for group C, egg size was significantly reduced (P < 0.01) in hormonally synchronized groups compared with the control. Survival to the eyed stage of eggs from females in groups A, B and C was significantly lower (P < 0.01) than in groups D and E. Per cent hatched alevins was lower (P < 0.01) in groups A, B and C than in groups D and E. We conclude that synchronization of ovulation in northern whitefish can be induced by a single acute injection of [D‐Arg⁶Pro⁹NEt]‐sGnRHa at 25 μg kg^?1 BW if given near the natural spawning time determined by water temperature below 2°C.     

Response of fingerling stinging catfish,Heteropneustes fossilis (Bloch) to varying levels of dietary l‐leucine in relation to growth,feed conversion,protein utilization,leucine retention and blood parameters

Growth response of fingerling Heteropneustes fossilis (6.8 ± 0.2 g; 11.2 ± 0.3 cm) to dietary l ‐leucine levels was assessed by conducting 8‐week feeding trial in a flow‐through system (1–1.5 L min^?1) at 28 °C water temperature. Casein–gelatin‐based isonitrogenous (380 g kg^?1; crude protein) and isoenergetic [17.9 MJ kg^?1; gross energy (GE)] basal diet was supplemented with different levels of l ‐leucine to achieve desired leucine levels ranging between 10 and 22.5 g kg^?1 dry diet. Analysed values were 9.9 (Lc_9.9), 12.4 (Lc_12.4), 15.1 (Lc_15.1), 17.4 (Lc_17.4), 20.1 (Lc_20.1) and 22.4 (Lc_22.4) g leucine kg^?1 diet. Fishes were stocked randomly in quadruplicates and fed to satiation at 07:00 and 17:30 h. Maximum absolute weight gain (AWG g fish^?1), feed conversion ratio (FCR), protein utilization efficiency (PUE%), leucine retention efficiency (LRE%) and haematological parameters were found in fish fed diet Lc_17.4. For precise determination of dietary leucine requirement of Singhi, AWG g fish^?1, FCR, PUE% and LRE% were subjected to broken‐line and second‐degree polynomial regression analysis. Second‐degree polynomial regression analysis fitted the data more accurately (P > 0.05) exhibiting high R² values. Hence, based on this analysis, dietary leucine requirement of fingerling H. fossilis is recommended to be 16.5 g kg^?1 of the diet, corresponding to 43.4 g kg^?1 protein for developing leucine‐balanced commercial feeds.     

Induced spawning in perch, Perca fluviatilis L., using FSH + LH with pimozide or metoclopramide

Induced spawning in perch, Perca fluviatilis L., was studied using follicle stimulating hormone and lutenizing hormone (FSH + LH) with the addition of pimozide or metoclopramide. The doses administered to fish were: 75 IU kg^?1 of FSH + LH with 5 or 10mgkg^?1 of pimozide (P) or metoclopramide (M) in females, and 25 IU kg^?1 of FSH + LH with 2.5 or 5 mg kg^?1 of P or M in males. Hormonal injections in males (except the injection of FSH + LH with 10 mg kg^?1 of M) did not influence the quantity of milt obtained. All females treated in this experiment had oocytes at the same stage of nucleus migration, so the time of ovulation was very synchronous, i.e. 16-24 h after injection. The relationship between the quality of the eggs, expressed as a survival to eyed-egg stage, and latency was inverse. Spawning success, expressed as a spawning effectiveness coefficient (S_e), was highest in the fish that had been treated with FSH + LH with a higher dose of M.     

Dietary taurine enhances growth and feed utilization in larval Nile tilapia (Oreochromis niloticus) fed soybean meal‐based diets

This study was conducted to evaluate the effects of dietary taurine on growth performance and feed utilization of Nile tilapia (Oreochromis niloticus) larvae. Four plant protein‐based, isonitrogenous (400 g kg^?1 protein), isoenergetic (19 MJ kg^?1) diets supplemented with four taurine concentrations (0.0, 5.0, 10.0 and 15.0 g kg^?1; designated as T₀, T_0.5, T₁ and T_1.5, respectively) were prepared. The diets were fed to triplicate groups of fish larvae (0.024 g average body weight), to apparent satiation, three times per day for 60 days. Larval growth rates and feed utilization efficiency were significantly improved with increasing supplemental taurine up to 10 g kg^?1 and decreased with further taurine supplementation. The quadratic regression analyses indicated that the maximum larval performance occurred at about 9.7 g kg^?1 of total dietary taurine. Fish survival was significantly lower at 15 g kg^?1 dietary taurine than at other taurine levels. Body protein significantly increased, while body moisture and ash decreased, with increasing dietary taurine up to 10 g kg^?1 and decreased with further taurine supplementation to 15 g kg^?1. Body lipid was not significantly affected by dietary taurine concentration. A number of body amino acids (tryptophan, arginine, histidine, leucine, isoleucine, valine, alanine, glycine, threonine and taurine) significantly increased with increasing supplemental taurine up to 10 g kg^?1 and then decreased with further increase in dietary taurine levels. The rest of body amino acids were not significantly affected by dietary taurine. The present results suggest that about 9.7 g kg^?1 dietary taurine is required for optimum performance of Nile tilapia larvae fed soybean meal‐based diets.     

Artificial spawning of African catfish Heterobranchus longifilis: differences between the effects on reproduction in females treated with carp pituitary homogenate or Ovopel

The effects of the controlled reproduction of African catfish Heterobranchus longifilis after ovulation stimulation with carp pituitary homogenate (CPH; 4 mg kg^?1; group I) or Ovopel (1/5+1 pellet kg^?1; group II) were investigated. After the application of Ovopel, eggs were obtained from a higher percentage of females than after a CPH treatment (87.5% and 75.0% respectively). The statistically significant (P≤0.05) effect of ovulation stimulator was specified only in the case of the weight of eggs (expressed in grams and in percentage of female body weight), being higher in fish treated with Ovopel compared with CPH‐treated fish (176.02 g, 8.43% and 109.51 g, 5.48%). The quality of eggs expressed in percentage of live embryos after 24 h incubation was higher by 7.5% in fish treated with Ovopel. Latency period did not significantly affect the weight of eggs, fertilization percentage or percentage of living embryos after 24 h of egg incubation. However, the weight of eggs and percentage of living embryos after 24 h incubation were higher in fish spawning after 12 h latency (159.38 g and 85.30%) compared with the weight and quality of eggs obtained from females spawning after 14 h latency (126.15 g and 76.04%).     

Investigation of the nutritional requirements of Australian snapper Pagrus auratus (Bloch & Schneider 1801): digestibility of gelatinized wheat starch and clearance of an intra-peritoneal injection of d-glucose

Two experiments were performed to investigate the digestibility and utilization of carbohydrate sources by Australian snapper Pagrus auratus. In the first experiment, snapper of two different size classes (110 and 375 g) were fed a reference diet containing no starch (REF) or diets containing 150 (PN15), 250 (PN25), 350 (PN35) or 450 g kg^?1 (PN45) of 100% gelatinized wheat starch to investigate the interactive effects of fish size and starch inclusion level on apparent organic matter (OM) or gross energy (GE) digestibility (ADC), post‐prandial plasma glucose concentration, hepatosomatic index (HSI) and liver or tissue glycogen content. A second experiment used a 72 h time course study to investigate the ability of larger snapper (300–481 g) to clear an intra‐peritoneal injection of 1 g d ‐glucose kg^?1 body weight (BW). Organic matter and GE ADCs declined significantly in both fish sizes as the level of starch increased (PN45energy small fishenergy large fish). There was no interaction between fish size and inclusion level with respect to GE or OM ADCs. Gross energy ADC for both sized fish was described by the linear function GE ADC=104.97 (±3.39)–0.109 (±0.010) × inclusion level (R²=0.86). Hepatosomatic index, liver and muscle glycogen concentrations were significantly elevated in both small and large snapper‐fed diets containing gelatinized starch compared with snapper fed the REF diet. Three‐hour post‐prandial plasma glucose concentrations were not significantly affected by fish size, inclusion level or the interaction of these factors (REF=PN15=PN25=PN35=PN45), and ranged between 1.60 and 2.5 mM. The mean±SD resting level of plasma glucose (0 h) was 2.4±1.1 mM. Circulating levels of plasma glucose in snapper peaked at 18.9 mM approximately 3 h after intra‐peritoneal injection and fish exhibited hyperglycaemia for at least 12–18 h. There were no significant differences between the plasma glucose concentrations of snapper sampled 0, 18, 24, 48 or 72 h after injection (0=18=24=48=72<12< 1<3=6 h), indicating snapper required almost 18 h to regulate their circulating levels of glucose to near‐basal concentrations. Australian snapper are capable of digesting moderate levels of gelatinized wheat starch; however, increasing the dietary content of starch resulted in a reduction in OM and GE digestibility. Smaller snapper appear to be less capable of digesting gelatinized starch than larger fish, and levels above 250 and 350 g kg^?1 of diet are not recommended for small and large fish respectively. Snapper subjected to an intra‐peritoneal injection of d ‐glucose have prolonged hyperglycaemia; however, the post‐prandial response to the uptake of glucose from normally digested gelatinized starch appears to be more regulated.     

Multiple GnRHa injections to induce successful spawning of wild caught greater amberjack (Seriola dumerili) matured in captivity

Reliable reproduction and sufficient amounts of juveniles obtained in captivity constitute a main bottleneck for mass production of greater amberjack. The aim of the present study was to combine several aspects of broodstock management and hormonal induction, to obtain a large number of high quality spawns. Captured Seriola dumerili sub‐adults were kept for three years in 10 m³ tanks. When fish were larger than 75 cm, they were individually tagged, periodically explored to determine gonad maturation and injected with gonadotropin releasing hormone analogue from June to October. A total of 15 inductions to four males and two females produced 330 821 ± 219 519 eggs/induction and a total of 22 spawns. The number of spawns and female fecundity (2.48 millions eggs/female/spawning season) were similar to those of free wild populations and higher than those previously obtained in captivity for this species. Egg quality increased from an initial low in the first two spawns in June to give, during July to October, a mean of 96.01 ± 6.50% fertilized eggs, 92.58 ± 17.56% hatched eggs, 78.66 ± 12.60% larval survival at day 3 after. These results showed that intramuscular injections of 20 μg kg^?1 body weight GnRHa under natural temperature and photoperiod conditions in the Canary Islands produced a high induction efficiency.     

Captive Breeding of Endangered Ompok pabda with Ovatide

The Pabdah catfish, Ompok pabda, was successfully spawned with the synthetic hormone Ovatide at two different doses (0.4 and 0.6 ml/kg of body weight of female). The latency period was 9–10 h at 0.6 ml compared to 10–12 h at 0.4 ml kg^?1 of body weight. All the females spawned successfully. Average rate of fertilization (75.5 %) and hatching (60.5%) was higher with a dose of 0.6 ml kg^?1, while lower fertilization (65.1%) and hatching rate (45%) were observed at 0.3 ml kg^?1 of body weight. Fecundity ranged from 80–130 eggs gm^?1 body weight of female. Eggs hatched between 12–14 h after spawning at a water temperature 28°–32°C. The mean egg diameter was 0.95 ± 0.15 mm.     

Artificial spawning of carp (Cyprinus carpio L.): differences between females of Polish strain 6 and Hungarian strain W treated with carp pituitary homogenate, Ovopel or Dagin

Investigations of the effects of controlled reproduction were conducted on carp females of Polish strain 6 and Hungarian strain W after ovulation stimulation with carp pituitary homogenate (CPH) (0.3 mg+2.7 mg kg^?1 body weight), Ovopel (1/5+1 pellet kg^?1 body weight) or Dagin (1 dose kg^?1 body weight). In both strains, the highest percentage of spawning females was found after the Ovopel treatment. After treatments with CPH and Dagin this percentage did not differ in strain 6; however, after Dagin, it was higher in fish of strain W. After CPH or Ovopel stimulation the females of line 6 yielded eggs of higher weight compared with line W. After the Dagin treatment the weight of eggs obtained from females, both strains was similar but much lower than after the two remaining agents. The quality of eggs expressed both by the percentage of fertilization and that of living embryos after 24 and 36 h incubation was similar in the two strains only in the group treated with Ovopel. After CPH application eggs of better quality were obtained from strain 6 compared with strain W; however, after the treatment with Ovopel, eggs of much better quality were noted in strain W. In general, the best effects of reproduction were recorded in the case of Ovopel and the poorest in that of Dagin. Females of strain 6 yielded eggs of a higher weight but the percentages of spawning females were higher in strain W after each of the applied spawning agents. A new approach to this problem consisted in investigating the interaction between ovulation stimulators and origin of females of fish treated with Dagin.