Regulation of cardiac function in the horn shark by changes in pericardial fluid volume mediated through the pericardioperitoneal canal

The California horn shark (Heterodontus francisci), instrumented with a pericardial catheter and a ventral-aortic flow probe, was studied to determine the effect of complete pericardial chamber evacuation on the time course for restitution of pericardial fluid-volume and pressure, and the effects of both fluid removal and its restitution on cardiac output. Prior to evacuation, pericardial pressure was –0.02±0.02 kPa, and cardiac output was 18±2 ml min^–1 kg^–1. Evacuation reduced pericardial pressure to –0.73±0.14 kPa, and increased cardiac output to 23±4 ml min^–1 kg^–1. The time course for restoration of post-evacuation pressure is described by a non-linear asymptotic function. A large percentage of the pericardial pressure and volume recovery occurred within the first hour, while, complete restoration of pre-withdrawal conditions required about 11 h. Pericardial pressure-volume relationships, determined by incremental infusion of small volumes of elasmobranch saline into the pericardium, confirm previous findings that the operating pericardial pressure in the horn shark is at or near ambient pressure and that both pericardial fluid volume and cardiac stroke volume influence horn shark pericardial pressure.     

Elasmobranch pericardial function. 1. Pericardial pressures are not always negative

Acute studies have led to the generalization that negative pericardial pressure is necessary for optimal cardiac function in elasmobranchs. We chronically instrumented horn sharks with pericardial catheters to test the hypothesis that ejection of pericardial fluid through the pericardioperitoneal canal (PPC) during routine handling could have accounted in part for previous measurements of exclusively negative pressures (–0.3 to –9.1 cm H₂O) in elasmobranchs. Maximum and minimum pericardial pressures measured immediately following routine handling (acute pressures) were more negative than those measured in resting horn sharks at intervals from 1 to 27 days following handling (chronic pressures). Chronic pericardial pulse pressure was less than acute. Entirely positive pericardial pressures were observed on occasion. Handling of chronically catheterized horn sharks resulted in ejection of 21 per cent (range=10–26, n=5) of the initial pericardial fluid volume through the PPC and reduced pericardial pressure. Operating pericardial fluid volume of horn sharks averaged 2.0 ml.kg^–1 (range=1.6–2.6, n=9). The PPC opened after 4.3±0.2 ml.kg^–1 (x±S.E.) of elasmobranch saline had been slowly infused into the pericardium, corresponding to an average pressure of 1.3±0.2 cm H₂O (n=10). The presence of the PPC plus a comparatively large pericardial fluid volume allows horn sharks to regulate pericardial pressure. Our analysis of pericardial pulse pressure, which can be an index of cardiac activity, suggests in contrast to previous studies that the elasmobranch heart can have relatively high stroke volumes at pericardial pressures near ambient. Thus, for venous return in resting or even moderately active elasmobranchs, it is more important that pericardial pressure be pulsatile than at a mean level which is negative.     

Effects of Chronic Aluminum Exposure on Swimming and Cardiac Performance in Rainbow Trout, <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>

Rainbow trout were exposed to 0–80 μg l⁻¹ aluminum (Al) at pH 5.2 in synthetic soft water, for up to 8 weeks. Trout were submitted to an incremental swimming test to quantify their aerobic swimming capacity (U_crit). After a simple, non-invasive cardiac surgery to install Doppler flow probes, their heart rate, cardiac output and stroke volume were measured while swimming at increasing water velocities. Fish exposed to Al accumulated significant amounts of Al at the gills (0–80 μg g⁻¹) and in their liver (5–60 μg g⁻¹) and had decreases in swimming capacity, ranging from 11 to 21%. Analysis of cardiac parameters during swimming revealed that increases in heart rate were used in trout exposed to the highest concentrations of Al to increase cardiac output, whereas control fish tended to increase cardiac output through increases in stroke volume.     

Rates of oxygen consumption and ammonia excretion of juvenile Eurasian perch Perca fluviatilis L.

The impact of feeding, fish size (body weight from 18.5 to 56.5 g) and water temperature (20 and 23 °C) on oxygen consumption (OC, mg O₂ kg^–1 h^–1) and ammonia excretion (AE, mg TAN kg^–1 h^–1) was studied in Eurasian perch held in recirculation systems. OC for both fed and feed-deprived (3 days) fish was higher at 23 °C (278.5 and 150.1 mg O₂ kg^–1 h^–1) than at 20 °C (249.3 and 135.0 mg O₂ kg^–1 h^–1; P < 0.01). AEs for both fed and feed-deprived fish were also significantly higher at 23 °C than at 20 °C (P < 0.001). Water temperature and fish size had a significant impact on the oxygen:feed ratio (OFR, kg O₂ kg^–1 feed fed day^–1) and ammonia:feed ratio (AFR, kg TAN kg^–1 feed fed day^–1; P < 0.001). Their average values at temperatures of 20 and 23 °C were 0.17 and 0.19 kg O₂ kg^–1 feed fed day^–1 and 0.009 and 0.011 kg TAN kg^–1 feed fed day^–1, respectively.     

A new technique of feeding, repeated sampling of blood and continuous collection of urine in white sturgeon

A new technique combining oesophageal intubation, dorsal aorta cannulation, and urinary catheterization was developed to monitor concentration of nutrients in the blood circulation and their metabolites in the urine of 1–2 kg white sturgeon, Acipenser transmontanus. Three experiments were conducted to assess the technique based on: (1) quantitative delivery of nutrients; (2) stress levels post-operation; and (3) monitoring of nutrients in the blood and metabolites in the urine. In Experiment 1, recovery of intubated Cr₂O₃ was 105±5% (mean ± SEM, n=3) 3 h after intubation. In Experiment 2, plasma cortisol and glucose concentrations returned to respective basal levels of 8.2±1.8 ng ml^–1 and 74± mg dl^–1 (n=9) 48 h post-operation. In Experiment 3, sturgeon intubated with 1 g kg^–1 body weight of glucose or dextrin at 48 h post-operation showed a significantly different (p<0.05) peak plasma glucose level of 139±4 and 100±5 mg dl^–1 (n=5), respectively, at 4 h. Urinary glucose excretion was 1.8±0.9 mg kg^–1 h^–1 (n=5) 4–8 h after intubation with glucose. Our results show that the new technique allows quantitative delivery of nutrients, repeated sampling of blood, and continuous collection of urine in white sturgeon with minimum stress.     

The effect of dietary vitamin E on the pleopodal egg number of Astacus leptodactylus (Eschscholtz, 1823)

The effect of vitamin E on the pleopodal egg number of Astacus leptodactylus (Eschscholtz, 1823) was studied. Crayfish were fed 2% of their total wet weight daily with vitamin E supplemented diets and a control for 70 days. The vitamin E content of the control diet, diet 1, diet 2 and diet 3 were 20 mg kg^–1, 40 mg kg^–1, 80 mg kg^–1 and 160 mg kg^–1 respectively on a dry weight basis. Vitamin E levels of the control and experimental diets were analysed by High Performance Liquid Chromatography. Results showed that diets containing supplemental vitamin E were associated with an increase in the number of pleopodal eggs. The best result was obtained with diet 2 containing 80 mg kg^–1 supplemental vitamin E.     

Effects of sublethal, acidic aluminum exposure on blood ions and metabolites, cardiac output, heart rate, and stroke volume of rainbow trout, Oncorhynchus mykiss

Doppler flow probes were fitted around the ventral aorta of rainbow trout, which were exposed to combinations of pH and aluminum (pH 5.1–6.2, Al 0–80 g l^–1) for 60 h. Fish accumulated Al at the gill and exhibited decreased blood Na⁺, Cl^–, and Ca²⁺ concentrations, and increased K⁺, hematocrit, hemoglobin, glucose, and lactate, indicating increasing ionoregulatory disturbance with increasing Al concentration. Fish exposed to ambient water (6.2) or low-pH (5.3) water without Al exhibited slight reductions in heart rates, as well as increased stroke volume, resulting in little variation in cardiac output. In the presence of Al (20 to 40 g l^–1) at low pH (5.1–5.3), fish increased their heart rate slightly and generally maintained their stroke volume, resulting in increased cardiac output in the first two days of exposure. At the highest Al concentration (80 g l^–1, pH 5.1), tachycardia was observed, concomitant with a decrease in stroke volume. The ionoregulatory imbalance and resulting increased blood viscosity explain these increases in heart rate rather than stroke volume in fish exposed to high concentrations of Al.     

Grow-out culture of tropical abalone, Haliotis asinina (Linnaeus) in suspended mesh cages with different shelter surface areas

Thisstudy investigated the effects of shelter surface area (SSA) on the feeding,growth and survival of the donkey-ear abalone, Haliotisasinina reared in mesh cages (0.38×0.38×0.28m) suspended in flow-through tanks (water volume = 6m³). Cages had sections of polyvinylchloride (PVC) thatprovided shelters with surface area of 0.22 m², 0.44m² and 0.66 m².Hatchery-produced abalone with initial shell length of 32 ± 1mm and wet weight of 7.5 g were stocked at 50individuals cage^–1 that corresponded to stocking densities ofca. 227, 113 and 75 abalone m^–2 of SSA. The ratios of sheltersurface area to cage volume (SSA:CV) were 5.5, 11 and 16.5. Abalones wereprovided an excess red seaweed Gracilariopsis bailinae(= Gracilaria heteroclada) at weekly intervals overa 270-day culture period. Feeding rates (18–20% of wet weight), foodconversion ratio (26–27) and percent survival (88–92%) did notdiffer significantly among treatments (p > 0.05). Body size at harvest rangedfrom 56 to 59 mm SL and 52 to 57 g wet body weightwith significant differences between abalone reared at SSA 0.22m² and 0.66 m² (p < 0.05).Abalone reared in cages with 0.66 m² SSA grewsignificantly faster at average daily growth rates of 132 m and188 mg day^–1. Stocking densities of 75–113m^–2 SSA in mesh cages suspended in flow-throughtanks resulted in better growth of abalone fed red seaweed.     

Quantifying the dietary biotin requirement of the catfish,Clarias batrachus

Asian catfish, Clarias batrachus, were fed semi-purified basaldiets containing 0, 0.1, 0.5, 1, 3 and 5 mg biotin kg^–1diet for 60 days. Fish fed the control diet (no biotin) showed(P < 0.05) higher mortality, lower weight gain, specificgrowth rate (SGR), feed efficiency ratio (FER) and protein efficiencyratio (PER) than in fish fed diets supplemented with biotin. The highestweight gain, SGR, FER and PER were noticed in fish fed 1 mg biotinkg^–1, followed by 0.5, 5, 3 and 0.1 mg biotinkg^–1, except for PER (followed by 0.5, 5, 0.1 and 3 mgbiotin kg^–1). Quadratic analysis showed that the optimumdietary biotin requirements for maximal weight gain, PER and PER were2.49, 2.54 and 2.52 mg kg^–1, respectively. Liver biotinconcentrations were influenced by levels of biotin in the diet.Concentration of liver biotin increased as level of dietarysupplementation increased and no biotin was detected in the liver of thecontrol fish. Liver pyruvate carboxylase and acetyl CoA carboxylaseactivities were higher in fish fed biotin-supplemented diets than incontrols. Biotin concentrations, pyruvate carboxylase and acetyl CoAcarboxylase activities in liver associated with normal growth rangedfrom 10.59 to 10.66 g g^–1, 147.97 to 148.18 units mgprotein^–1 and 12.76 to 12.78 units mg protein^–1, respectively. Biotin deficiency symptoms such as anorexia, darkskin colour and convulsions were observed in fish fed the control diet.The optimum dietary biotin requirement for maximal growth of C.batrachus is about 2.49 mg kg^–1 diet.     

Induction of Out-of-Season Spawning of Pikeperch, Sander Lucioperca (L.)

Pikeperch were induced to spawn 3 months prior to the natural spawning period through photothermal and hormonal stimulation. Females (five specimens in each group) were stimulated with injection of human chorionic gonadotropin (hCG) once (200 IU kg^–1), twice (200 IU kg^–1, second dose after 48 h–400 IU kg^–1) or three times (200 IU kg^–1, after 24 h–200 IU kg^–1 and after another 24 h–200 IU kg^–1). The control group was injected once with 0.9% NaCl. The males were stimulated with a single hormone dose of 200 IU kg^–1. Eggs were obtained from all the hormonally treated fish. None of the control group females, which were only stimulated photothermally, ovulated any eggs. The time of ovulation was 66–71 h following the first injection, and the eggs viability until the eyed stage (from 71.5 to 77.5%) did not depend on the number of hormone doses (P > 0.05). The out-of-season spawning method described in this paper could be used to provide pikeperch larvae for intensive culture systems (recirculating water systems) before natural spawning season and to produce larger-sized pikeperch fingerlings for stocking.     

Nitrogenous waste excretion and accumulation of urea and ammonia inChalcalburnus tarichi (Cyprinidae), endemic to the extremely alkaline Lake Van (Eastern Turkey)

The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 – 19°C; pH 9.8; 153 mEq·I^–1 total alkalinity; 22 total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169moles·kg^–1 fish·h^–1, respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 – 35moles·g^–1·ml^–1) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min^–1·g^–1) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min^–1·g^–1) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated.     

The effects of experimental anaemia on CO2 excretionin vitro in rainbow trout,Oncorhynchus mykiss

The effects of severe experimental anaemia on red blood cell HCO₃ ^– dehydrationin vitro were examined in rainbow trout,Oncorhynchus mykiss. After 5 days of anaemia (haematocrit=4.9±1.1%) induced by intraperitoneal injection of phenylhydrazine hydrochloride, fish displayed elevated arterial CO₂ tensions (anaemic PaCO₂=3.19±0.42 torrvs. control PaCO₂=1.35±0.17 torr) and a significant acidosis (anaemic pHa=7.73±0.04vs. control pHa=7.99±0.04). However, after 15–20 days of anaemia (hct=6.6±0.8%) induced by blood withdrawal, the arterial CO₂ tension was significantly lower than the control value, suggesting that physiological adjustments occurred within this time period to compensate for the lowered haematocrit. Compensation probably did not involve alterations in ventilation, which was unaffected by 5 days of anaemia (anaemic ;w=786±187 ml min^–1 kg^–1 vs. control ;w=945±175 min^–1 kg^–1), based on indirect Fick principle measurements.Potential adaptations to longer term anaemia at the level of the red blood cells were investigated using a radioisotopic HCO₃ ^– dehydration assay. Owing to the difference in haematocrits, the HCO₃ ^– dehydration rate for blood from anaemic fish was significantly lower than that for control fish following equilibration at the same CO₂ tension. This difference was eliminated when HCO₃ ^– dehydration rates were measured on blood samples adjusted to the same haematocrit, a result which implies that the intrinsic rate of CO₂ excretion at the level of the red blood cell was not up-regulated during anaemia. The difference was also eliminated by equilibrating the blood samples with CO₂ tensions appropriate for the group from which the sample was obtained,i.e., PCO₂=1.4 torr for control samples and PCO₂=3.2 torr for anaemic samples; each at the appropriate haematocrit. It is concluded that the elevated PaCO₂ helps to reset CO₂ excretion to the control level, but that some additional physiological adjustment occurs to lower the PaCO₂ after 15–20 days of anaemia.     

Oxygen consumption and responses to hypoxia of ammocoetes of the southern hemisphere lampreyGeotria australis

The standard rate of oxygen consumption of ammocoetes (larvae) ofGeotria australis with a mean weight of c. 0.5 g was 9.6, 31.4 and 59.4l g^–1 h^–1 at 4.5, 15.5 and 25.0°C respectively, which gives an overall Q₁₀ of 2.4. The regression coefficient for the logarithmic relationship between oxygen consumption and body weight at 15.5°C was 0.704. The ammocoetes ofG. australis have a much lower rate of oxygen consumption at 15.5 and 25.0°C than those of holarctic lampreys. This presumably reflects the lower oxygen delivery pressure to their tissues and helps account for their slow growth rate. At 15.5°C, ammocoetes ofG. australis emerged from the substrate at 21–25 mm Hg and, unlike those of the Northern HemisphereIchthyomyzon greeleyi, died at 14–17 mm Hg. Thus, despite having a thinner water/blood barrier in the gills and blood with a higher oxygen affinity and capacity than holarctic ammocoetes, the larvae ofG. australis cannot survive very low dissolved oxygen tensions. This is apparently related to an inability of larvalG. australis to meet the high oxygen requirements of the respiratory pump at these oxygen tensions. During metamorphosis, oxygen consumption at 15.5°C rose from approximately 27l g^–1 h^–1 at the beginning of transformation to 33.2l g^–1 h^–1 by Stage 3 and then rapidly to 66l g^–1 h^–1 at Stage 6. It remained near this level in Stage 7 and the downstream migrant.     

Effects of purified microcystin-LR and cell extracts of Microcystis strains PCC 7813 and CYA 43 on cardiac function in brown trout (Salmo trutta) alevins

Sub-lethal cardiac responses of brown trout alevins (Salmo trutta L.) were determined in response to aqueous extracts of the cyanobacterium Microcystis strains PCC 7813 (microcystins detectable by HPLC) and CYA 43 (no microcystins detectable by HPLC) and to the purified cyanobacterial hepatotoxin, microcystin-LR (MC-LR) at concentrations of 5, 50 and 500 g microcystin-LR equivalents l^–1. Responses were determined using a flow chamber and video camera attached to a low power microscope. Heart rate in brown trout alevins was acutely sensitive to cyanobacterial extracts and significant increases were observed within 15–60 sec of exposure to aqueous extracts, although no change was observed on exposure to purified MC-LR. Stroke volume increased in all treatments at 50 and 500 g MC-LR equivalents l^–1, which may, at least in part, have been due to vasodilation of the yolk-sac blood vessels. Cardiac output increased significantly at all three concentrations of cyanobacterial cell extracts but not at the lowest concentration of MC-LR, although the rate increased at levels at/or above 50 g l^–1. Increased heart rate, stroke volume and cardiac output occurred at environmentally relevant microcystin concentrations of Microcystis PCC 7813 and CYA 43 aqueous extracts.     

The effects of temperature in the life cycle of two consecutive generations of the cuttlefish Sepia officinalis (Linnaeus, 1758), cultured in the Algarve (South Portugal)

We are presently culturing the 4^th generation of thecuttlefish, Sepia officinalis in our laboratory. A firstgeneration (F1) was grown from eggs collected from the wild (Ria Formosa–South Portugal) during the summer, at mean temperatures of 27°C ± 3°. In the present study, a second generation(F2), originated from eggs laid in the laboratory by females from F1 wascultured between the start of autumn and the end of spring, at meantemperaturesof 15 °C ± 4 °C. The life cycle ofcuttlefish from F2 was compared to F1. Populations of 30 cuttlefish were usedineach experiment. Cuttlefish were grown from one day old until the cycle wascompleted (when the last female in each population had died). Cuttlefish fromF2cultured at much lower temperatures had a longer life cycle, of almost 9 months(260 days) compared to cuttlefish from F1, which completed their cycle in lessthan 6 months (165 days). Cuttlefish from F2 grew significantly larger (U =0.00; p < 0.01) with mean weights of 343.3 ± 80.5 g and248 ± 33.1 g for males and females, respectively, comparedtoF1 (199.6 ± 40 g and 143.3 ± 30.9 g formales and females, respectively). Females from F2 had higher fecundity (225eggsfemale^–1) compared to females from F1 (144 eggs perfemale^–1), produced bigger eggs (t = 45.60752; p < 0.0001),weighing 0.74 ± 0.18 g, compared to 0.46 ± 0.11 fromF1,and bigger hatchlings (t = 7,144783; p < 0.0001), weighing 0.10 ±0.02g, compared to 0.09 ± 0.02 g for the summerpopulation.     

The First Attempt to Artificially Reproduce the Endangered Cyprinid Lake Minnow Eupallasella Perenurus (Pallas)

The standard artificial reproduction technique with the use of Ovopel (GnRH analogue) was evaluated for the critically endangered cyprinid species in Poland, the lake minnow Eupallasella perenurus. Wild spawners were angled at the beginning of the spawning season. Only females with a condition coefficient value higher than the mean were included in the experiment and then stimulated with Ovopel. Group A (n = 20) was given standard treatment (0.2 pellet kg^–1 and 1.0 pellet kg^–1 after 12 h), whereas group B (n = 8) was treated with a single dose of 2.0 pellets kg^–1. After fertilisation with the dry method, the glutinous eggs attached to the bottom of flow-through aquaria were incubated at 17.1–18.4°C. Throughout incubation (85D°), dead eggs were removed and counted. The same was done with dead larvae, those with deformed bodies or those with empty alimentary tracts after 2 days of external feeding. Two injections of Ovopel resulted in a significantly (P 0.05) higher ovulation rate in comparison with the single dose (70 and 25% in groups A and B, respectively). The individual hatching rates were very high (98.4–100%), as was the share of good quality larvae (91.1 and 96.5% of stripped eggs in groups A and B, respectively). These results indicate that the standard propagation method used with commercially important cyprinid species can also be used to successfully breed E. perenurus.     

Utilization of carotenoids from various sources by rainbow trout: muscle colour,carotenoid digestibility and retention

Rainbow trout (Oncorhynchus mykiss) with a mean (sd) weight of 120 (2) g were fed diets supplemented with astaxanthin extracted from the yeast Phaffia rhodozyma (OY1 = 50 mg carotenoids kg^–1 feed, OY2 = 100 mg carotenoids kg^–1 feed), astaxanthin (AX = 100 mg astaxanthin kg^–1 feed) and canthaxanthin (CX = 100 mg canthaxanthin kg^–1 feed) for 4 weeks. Muscle analyses at the end of the experiment indicated a significantly higher carotenoid concentration in the AX group, while CX and OY1 groups were similar in spite of the differences in dietary concentration. The measure of total muscle colour difference (E^* _ab) between initial samples and 4 week ones was higher for the AX fish group but showed no significant difference between OY1, OY2, and CX. The hue and the reflectance ratio (R₆₅₀:R₅₁₀) of fish muscle increased in proportion to carotenoid intake. Digestibility (ADC) of yeast astaxanthin in OY1 and OY2 groups was significantly higher than that in the AX group. Canthaxanthin ADC was about one sixth of that of astaxanthin (AX group). Carotenoid retention in the muscle, expressed as a percentage of carotenoid intake, was higher for the AX group than that recorded for OY1 and OY2. According to ADC, carotenoid retention showed a marked lower value for the CX group. Muscle retentions were similar for astaxanthins from both sources.     

Impacts of otter (Lutra lutra L.) predation on fishponds: A study of fish remains at ponds in the Czech Republic

The increasing numbers of otters (Lutralutra L.), which are protected by the CzechAct of Nature and Landscape Protection, arecausing serious problems for fishpondmanagement. The diet of otters on pond farmsconsists predominantly (80%) of common carp,Cyprinus carpio, and to a lesser extentother pond fish species (perch, Percafluviatilis, zander, Stizostedionlucioperca and grass carp, Ctenopharyngodon idella). The size of carpcaptured by otters ranged between 376–683 mmTL (500 ± 88 mm) and 1,049–11,768 g(3,478 ± 2,867 g). Reconstructed originalweight and length of captured grass carp andperch were 599 and 182 mm TL, and 2,665 and163 g, respectively. In most of prey fishcorpses left by otters, only viscera andassociated parts were consumed. The weight ofindividual common carp corpses was estimated as73.0 ± 24.6 (26.3–95.9)% of theoriginal reconstructed weight, which means thatonly 27.0 ± 17.2 (4.1–73.7)% of fishbody mass was consumed by otters. In perch,62.8% of fish body mass was left unconsumed.Heavy losses have been reported also on fishstocks in ice-covered ponds during the winterperiod, when shoals of resting fish have beendisturbed and stressed due to otter hunting.     

Effects of dietary carnitine and lipid on growth and body composition of hybrid striped bass (Morone chrysops ♀× M. saxatilis ♂)

A study was undertaken to investigate the effects of graded dietary levels and different types of carnitine on hybrid striped bass (Morone chrysops × M. saxatilis %) fed different levels of lipid. An incomplete factorial design was utilized in which diets containing lipid at either 5 or 10% were supplemented with l-carnitine at 0, 500, or 1000 mg kg^–1 diet, dl-carnitine at 1000 mg kg^–1 diet, or carnitine chloride to provide 1000 mg carnitine kg^–1 diet. Juvenile hybrid striped bass (3.3 g fish^–1) were stocked into individual 38-l aquaria connected as a brackish water (6), recirculating system and fed each diet in triplicate for 9 weeks.Supplementation of the diet with 1000 mg carnitine kg^–1 increased muscle carnitine from 35.5 to 47.7 g g^–1 tissue. Carnitine supplementation did not result in increased weight gain regardless of carnitine level or type; however, weight gain showed a significant (p<0.05) response to dietary lipid with fish fed diets containing 10% lipid growing 34% more than fish fed diets with 5% lipid. The hepatosomatic index also was unaffected by diet, but the intraperitoneal fat (IPF) ratio was significantly elevated (5.1 vs 3.2%) in fish fed diets with 10% lipid compared to those fed diets with 5% lipid. Fish fed diets containing 1000 mg carnitine kg^–1 had increased IPF ratio values at 4.7% compared to 3.9% for fish fed the basal diet. Liver lipid also was responsive to dietary treatment, increasing from 6.7 to 8.8% of wet weight as dietary lipid increased from 5 to 10%. The relative quantities of triglycerides, free fatty acids and phospholipids in muscle and liver were not influenced by carnitine level, carnitine type or dietary lipid level. Supplementation of carnitine does not appear to be beneficial to hybrid striped bass based on either growth performance or body composition.     

Induced Ovulation in Obscure Puffer Takifugu obscurus by Injections of LHRH-a

Obscure puffer Takifugu obscurus (Abedate) is one of the several species of Takifugu genus that migrate to the Yangtze River, China during the spawning season of February to May. It is a popular fish among locals and fetches a premium price owing to its high-quality meat. It is also a potential species for intensive culture as its natural populations are currently declining. There have been no published studies on the effects of GnRH-a injection on the obscure puffer. In this paper, we report the results of several obscure puffer ovulation trials conducted in 1995 and 1996. We demonstrated that ovulation could successfully be induced in obscure puffer collected from open systems during spawning period using a dosage of LHRH-a as low as 40 µg kg^–1 in two injections. We found no significant differences among 80, 60, 40 µg LHRH-a kg^–1 treatments in ovulation success, egg production, fertilization rate and hatch rate. Accordingly, we recommend the use of 40 µg LHRH-a kg^–1 as the optimal dosage from an economical point of view.