Estimates of larval survival of cod by releases of genetically marked yolk-sac larvae

In the spring of 1995, 18 million genetically marked yolk-sac cod larvae Gadus morhua were released into a 2.9-km², nearly land-locked fjord in western Norway. Four quantitative surveys were conducted, 11, 33, and 63 days, and 1 year after the first release. Almost 100% of the collected cod larvae were successfully identified to GPI-1 * genotype. The marked cod larvae constituted 18% of all sampled cod larvae in the first survey and 9% in the two next. The average rate of mortality was estimated to be 23% day ⁻¹ for the first 10 days after release and 12% day ⁻¹ during the next month after release. After 1 year (April 1996), the number genetically marked I-group cod in the fjord was estimated to be <120. The effect of the historical programme of large-scale releases of yolk-sac larvae on recruitment were evaluated and found to be small.     

Radioactive strontium (85Sr) in marking newly hatched pike and success of stocking

Immersion of newly hatched pike fry in an aqueous solution of 1·85 MBq ml⁻¹⁸⁵Sr did not affect their growth or survival over 3 weeks. Cannibal pike fry retained only l.2–3·3% of the ⁸⁵Sr from their labelled prey. Newly hatched ⁸⁵Sr-marked fry stocked into two lakes in 3 years were distinguishable from wild fish 4–6 weeks later. Stocked and wild fry grew equally well, and stocked pike survived best where density of wild pike was highest. There was no evidence of increase in density as a result of Stocking.     

Stocking success of newly hatched pike evaluated by radioactive strontium (85Sr) marking

The stocking of newly hatched pike Esox lucius labelled with radioactive strontium (⁸⁵Sr) and later electrofishing of the same area was found to be a workable tool in assessing the success of pike stockings. ⁸⁵Sr‐labelled individuals constituted 96% of the 0+year pike catch from late summer electrofishing in the stocked littoral areas of the heavily regulated Lokka Reservoir. The density of 0+year pike reached 2·1 individuals 100 m⁻² in the stocked areas in comparison to 0·3 individuals 100 m⁻² in the reference areas. In the three other stocked lakes the proportion of labelled pike in the catch ranged from 0 to 42% in late summer. The results suggest that pike stockings are profitable in filling empty or nearly empty 0+year pike habitats of regulated lakes or other waterbodies, where the natural reproduction of pike has declined due to human activities.     

Colonization of Vibrio pelagius and Aeromonas caviae in early developing turbot (Scophthalmus maximus L.) larvae

Polyclonal antisera made in rabbits against whole washed cells of Vibrio pelagius and Aeromonas caviae were used for detection of these bacterial species in the rearing water and gastrointestinal tract of healthy turbot ( Scophthalmus maximus ) larvae exposed to V. pelagius and/or Aer. caviae . The results demonstrated that this method is suitable for detection of V. pelagius and Aer. caviae in water samples and larvae at population levels higher than 10³ ml⁻¹ and 10³ larva⁻¹. Populations of aerobic heterotrophic bacteria present in the gastrointestinal tract of turbot larvae, estimated using the dilution plate technique, increased from approximately 4 × 10² bacteria larva⁻¹ on day 3 post-hatching to approximately 10⁵ bacteria fish⁻¹ 16 days post-hatching. Sixteen days after hatching, Vibrio spp. accounted for approximately 3 × 10⁴ cfu larva⁻¹ exposed to V. pelagius on days 2, 5 and 8 post-hatching. However, only 10³ of the Vibrio spp. belonged to V. pelagius . When larvae were exposed to Aer. caviae on day 2 post-hatching, the gut microbiota of 5-day old larvae was mainly colonized by Aeromonas spp. (10⁴ larva⁻¹), of which 9 × 10³ belonged to Aer. caviae . Later in the experiment, at the time when high mortality occurred, 9 × 10⁵ Aer. caviae were detected. Introduction of V. pelagius to the rearing water seemed to improve larval survival compared with fish exposed to Aer. caviae and with the control group. It was therefore concluded that it is beneficial with regard to larval survival to introduce bacteria ( V. pelagius ) to the rearing water.     

Oxygen consumption by eggs and larvae of striped mullet, Mugil cephalus, in relation to development, salinity and temperature

Oxygen consumption rates during embryonic and the first 38 days of larval development of the striped mullet were measured at 24° C by differential respirometry. Measurements were obtained at the blastula, gastrula and four embryonic stages, and at the yolk-sac, preflexion, flexion and post-flexion larval stages.
Oxygen uptake rates of eggs increased linearly from 0.024 μl O₂ per egg h^-1 (0·323 μl O₂ mg^-1 dry wt h^-1) by blastulae to 0·177 μlO₂ per egg h^-1 (2·516 μlO₂mg ¹dry wth^-1) by embryos prior to hatching. Respiration rates did not vary significantly among four salinities (20,25, 30, 35%₀).
Larval oxygen consumption increased in a curvilinear manner from 0·243 μl O₂ per larva h^-1 shortly after hatching to 18·880 μl O₂ per larva h^-1 on day 38. Oxygen consumption varied in direct proportion to dry weight. Mass-specific oxygen consumption rates of preflexion, flexion, and postflexion larvae did not change with age (10·838 μl O₂ mg ¹dry wt h^-1).
Larval oxygen consumption rates did not vary significantly among salinities 10–35%. Acute temperature increases elicited significant increases in oxygen consumption, these being relatively greater in yolk-sac larvae ( Q₁₀ = 2·75) than in postflexion larvae ( Q₁₀ = 1·40).     

Size-dependent mortality of red sea bream, Pagrus major, juveniles released with fluorescent otolith-tags in News Bay, Japan

Totals of 2^.67 x 10⁵ and 7^.56 x 10⁵ juvenile red sea bream of three size groups (10, 20 and 40 mm t.l.) marked with a fluorescent substance in the otolith were released in News Bay, Oita Prefecture, Japan, in July 1987 and June 1988, respectively; the aim was to estimate growth and mortality of different developmental stages.
Of fish released in 1987 and 1988, 10 618 and 4413, respectively were recaptured during those two years. Released fish remained in the bay until the end of summer, and afterwards migrated out towards open waters. Fish of the 40-mm group released in 1987 grew to over 200 mm t.l. in one year. Mean growth rate for 19 days after release was higher in the 40-mm group (0^.87 mm day⁻¹) than in the 20-mm group (0^.74mm day⁻¹). Survival rates over 19 days were 59^.0 and 10^.1 % for 40-mm and 20-mm fish, respectively, in 1987, and those over 30 days were 69^.2, 3^.3 and 0^.0% for 40-mm, 20-mm and 10-mm fish, respectively, in 1988.
Cannibalism was indicated by the presence of marked otoliths for 20-mm fish in the stomachs of a few 40-mm individuals recaptured 2 days after release. Size-dependent growth and size-selective mortality were both noted in juvenile red sea bream, i.e. the relative size differential between larger and smaller individuals was maintained in the period between marking and recapture, and mortality was inversely proportional to size.     

Energy metabolism in eggs and larvae of the Senegal sole

Oxygen consumption in Solea senegalensis increased during the egg stage reaching values close to 4 nmol O₂ ind⁻¹ at hatching. After hatching, larval oxygen consumption continued to increase, reaching a maximum rate of 9.97⁻¹±87 nmol O₂ ind⁻¹ h⁻¹ 2 days after the opening of the mouth. Body nitrogen content decreased mainly after exhaustion of yolk reserves. Carbon content decreased during the whole endogenous feeding phase, although it decreased twice as quickly after yolk-sac absorption. The free amino acid (FAA) depletion rate was higher during egg development and the yolk-sac period. Complete yolk absorption coincided with the consumption of the 90% of initial FAA content in the eggs and the remaining FAA were consumed at a lower rate. Based on stoichiometrical calculations, FAA appears to be the most important energy substrate during the egg stage (86%) in the Senegal sole. During the period from hatching to the mouth opening, contributions of FAA and lipids as metabolic fuels were similar (41 and 47%, respectively). The decrease in larval protein content during starvation indicates that amino acids from body protein are used as energy substrates under food deprivation.     

Effects of development, temperature and salinity on metabolism in eggs and yolk-sac larvae of milkfish, Chanos chanos (Forsskål)

Oxygen uptake rates and yolk-inclusive dry weiGhts were measured during the egg and yolk-sac larval stages of milkfish, Chanos chanos (Forsskal). Oxygen uptake by eggs and yolk-sac larvae was measured to assess the effects of four salinities (20,25,30,35 ppt) at 28°C. The effects of three temperatures (23,28,33°C) on oxygen uptake by yolk-sac larvae were determined at a salinity of 35 ppt. Dry weights were measured throughout embryonic development at 28°C and the yolk-sac stage at 23.28 and 33°C.
Oxygen uptake rates of eggs increased more than fivefold during embryogenesis (0.07±0.03 to 0.40 ± 03 μl O₂ egg ⁻¹ h ⁻¹;blastula to prehatch stage). Larval oxygen uptake did not change with age but was affected by rearing temperature (0.33 ± 0.08, 0.44 ± 0.07 and 0.63 ± 0.13 μl O₂ larva ⁻¹ h⁻¹ at 23, 28 and 33°C, respectively; Q₁₀= 1.93). Acute temperature changes from 28 to 33°C caused significant increases in oxygen uptake by embryos (Q ₁₀= 1.69–3.58) and yolk-sac larvae (Q ₁₀=2.55). Salinity did not affect metabolic rates.
Dry weight of eggs incubated at 28°C decreased 13% from fertilization to hatching. Incubation temperatures from 23–33°C did not affect dry weights at hatching. Rearing temperatures significantly affected the rate of larval yolk absorption (Q ₁₀= 2.25).     

Oxygen consumption in Oreochromis niloticus (L.) in relation to development, salinity, temperature and time of day

Oxygen consumption of Oreochromis niloticus at different stages of development was studied in relation to salinity, temperature and time of day, using a Warburg apparatus. The oxygen consumption of newly hatched (0–14 h) larvae was 3.40 μl O₂ larva⁻¹ h⁻¹, of older yolk sac larvae 10.09 μl O₂ larva⁻¹ h⁻¹, and of one-month-old fry 32.99 μl O₂ larva⁻¹ h⁻¹. The QO₂ values showed a decrease with development and growth, ranging from 21.2–26.0 μl O₂ mg⁻¹ h⁻¹ in newly hatched larvae to 2.97 μl mg⁻¹ h⁻¹ in one-month-old fry. Changes in oxygen consumption occurred with salinity, the highest being at 17%o. Active larvae (12-24 mm T.L.) showed a doubling of consumption with a 10° C rise in temperature, and their Q₁₀ factor increased from 2.25 to 3.43 with increasing size. Day-old yolk-sac larvae, late yolk-sac larvae (5 days old) and fry of 12 14 mm length all showed a depression in oxygen consumption at midnight followed by a dawn rise.     

Transgenerational marking of freshwater fishes with enriched stable isotopes: a tool for fisheries management and research

A promising new method of marking larval freshwater fishes with enriched stable isotopes by means of injecting the maternal parent with the marking agent was investigated. The ¹³⁸Ba:¹³⁷Ba ratios in the otoliths of larval golden perch Macquaria ambigua were compared to determine the effect of injecting female broodstock with different dosages of enriched ¹³⁷Ba at various times before spawning. There was 100% mark success in the progeny of fish injected with 20 μg g⁻¹ of enriched ¹³⁷Ba 24 h before inducing spawning with hormones and 40 μg g⁻¹ administered at the same time as inducement of spawning. Injection of 40 μg g⁻¹ enriched ¹³⁷Ba 21 days before spawning resulted in only 81% mark success and suggests rapid elimination of barium in M. ambigua . Injection with enriched ¹³⁷Ba did not significantly affect the fertilization rate, number of fertilized eggs or hatching rate compared with long-term hatchery records. These results suggest that transgenerational marking is an effective and affordable means of mass-marking larval fishes. Thousands of larval fishes can be permanently marked with a unique artificial isotopic mark via a single injection into the maternal parent, thus avoiding the handling of individual fishes or having to deal with chemical baths. Because no single mark or tagging method is suitable for all situations, transgenerational marking with enriched stable isotopes provides another method for researchers and managers to discriminate both hatchery-reared and wild fishes.     

Muscle growth in yolk-sac larvae of the Atlantic halibut as influenced by temperature in the egg and yolk-sac stage

Atlantic halibut eggs and yolk-sac larvae were incubated at 1, 5 and 8° C. Eggs incubated at 8° C gave slightly shorter larvae at hatching with a significantly smaller total cross-sectional area of white muscle fibres than eggs incubated at 5° C. Transport of eggs 2 days prior to hatching gave significantly longer larvae at hatching with a significantly larger red fibre cross-sectional area than when eggs were transported shortly after the blastopore closure. A higher survival until 230 degree days after hatching was also observed in the former group. All eggs incubated at 1° C died before hatching and all larvae incubated at 1° C died before 45 degree days after hatching. From hatching until 230 degree days the total white cross-sectional area increased threefold in all temperature groups. The increase in white cross-sectional area was entirely due to hypertrophy between hatching and 150 degree days (10 mm L _S). Recruitment of new white fibres increased in germinal zones at the dorsal, ventral and lateral borders of the myotome from 150 degree days onwards, but at 230 degree days (12–13 mm L _S) the recruitment fibre zone constituted <10% of the total white cross-sectional area. Larval incubation at 8° C gave slightly longer larvae with a significantly larger cross-sectional area of recruitment fibres at 230 degree days than incubation at 5° C. The larval group incubated at 8° C also had a significantly lower survival until 230 degree days than did the 5° C group. Incubation temperature regimes did not affect the volume density of myofibrils in the axial muscle fibres at 230 degree days. Thus hypertrophy is the predominant mechanism of axial white muscle growth in Atlantic halibut yolk-sac larvae and an increased rearing temperature during the yolk-sac stage increases white muscle fibre hyperplasia.     

A study of the mechanism of algal uptake in yolk-sac larvae of Atlantic halibut (Hippoglossus hippoglossus)

The drinking rate of water, and the ingestion- and assimilation rates of algae in yolk-sac larvae of Atlantic halibut were examined by use of³H-dextran and¹⁴C-labelled algae. The drinking rate throughout the yolk-sac stage was in the range of 7–160 nl per larva h⁻¹, with a slight increase towards the end of the period. The ingestion rate of algae ( Tetraselmis sp.) was very low before day 30 and showed a peak between day 43 and 48 at 5° C. The assimilation efficiency of the algae was in the range of 1-5%. The clearance rate of algae was 100–1000 times higher than the drinking rate, and was correlated to the distance between the gill arches. Bigger cells were more effectively retained than smaller ones. The results suggested that the larvae acted as filter feeders from day 30 up to the point when they are expected to start feeding on bigger prey.     

Protein Kinase FA/Glycogen Synthase Kinase-3α After Heparin Potentiation Phosphorylates τ on Sites Abnormally Phosphorylated in Alzheimer''s Disease Brain

In this work, we tested the effect of ion channel blockers and of phorbol ester treatments on [³H]dopamine ([³H]DA) release and neurotensin (NT)-induced facilitation of [³H]DA release from cultures of rat fetal mesencephalic cells. The potassium channel blockers tetraethylammonium and 4-aminopyridine increased basal [³H]DA release and decreased K⁺-evoked [³H]DA release, whereas apamin was without effect. K⁺-evoked [³H]DA release was decreased by ω-conotoxin and nifedipine, totally suppressed by cadmium, and unaffected by amiloride. These results show the differential sensitivity of [³H]DA release to blockade of various ion channels and suggest the involvement of N-type, L-type, and non-L-non-N-type, but not T-type, voltage-sensitive calcium channels in K⁺-evoked release. Phorbol 12-myristate 13-acetate increased both spontaneous and K⁺-evoked [³H]DA release, suggesting a modulatory action of protein kinase C on DA release in this system. Unexpectedly, however, the effects of the phorbol ester were not counteracted by the protein kinase C inhibitors H7, staurosporine, or polymyxin B. NT-induced facilitation of K⁺-evoked [³H]DA release was insensitive to most of the ion channel blockers, except cadmium (64% decrease in NT effect), suggesting that the corresponding potassium' and calcium channels were not involved in the effect of NT on [³H]DA release in this system. The NT effect was totally suppressed by phorbol ester treatments, indicating a possible desensitization of the corresponding transduction mechanisms after protein kinase C activation.     

Kinetic characteristics of the sodium uptake mechanism during the development of embryos and fry of Atlantic salmon, Salmo salar L., in an improved water quality

The kinetics of active sodium uptake in dechorionated embryos, yolk-sac fry and start-feed fry of Atlantic salmon were compared in two groups reared either in low conductivity, untreated, river water (conductivity ∼ 46 μS cm⁻¹, pH 5.75), or in 'improved' river water buffered with sea water (conductivity ∼2200 μS cm ¹, pH 6.56), the latter treatment often being used in commercial hatcheries to avoid problems associated with periodic acidification.
Maximal transport rate ( V _max) increased during development in both groups but was always significantly higher in embryos and fry maintained in untreated river water. Values for K _m were not seen to vary during development up to 12 weeks after hatching and were not significantly different between groups, or from values reported for adult Atlantic salmon in fresh water.
The results are discussed with respect to the influence of Na⁺ concentrations in the perivitelline fluid of developing eggs and in the external medium surrounding fry on V _max and K _m. The ability of fry reared entirely in buffered river water to maintain sodium balance following transfer to untreated river water is also considered.     

Metabolic utilization of body stores during the early life of whitefish, Coregonus lavaretus L.

Patterns of oxygen consumption, ammonia and urea excretion were monitored during late embryogenesis, i.e. 5 days before mass hatching and 12 days during the free-swimming stage of whitefish larvae, Coregonus lavaretus. Oxygen consumption increased from 1.31 to 2.53 mgO₂ h⁻¹× 10³ eggs⁻¹ at hatching. Fasted, free-swimming larvae showed increasing oxygen consumption to the tenth day after hatching when it reached 5.52 mgO₂h⁻¹× 10³ larvae⁻¹. Ammonia and urea excretion increased during pre-hatching period from 52.1 to 163.2 and 26.8 to 51.4 μgh⁻¹× 10³ eggs⁻¹, respectively. The nitrogen excretion rate increased between the sixth and tenth day of fasting, i.e. for ammonia from 117.7 to 160.9 and for urea from 35.8 to 52.5 μg h⁻¹× 10³ larvae⁻¹. Cumulative data on nitrogen and energy metabolism indicated that during late embryogenesis, and up to the fifth day after hatching, protein dominated in the energy expenditure. During the free swimming stage, the ratio of fat to protein in energy expenditure rose from 0.86 to 1.99. Combined data for several fish species indicated high dependance of oxygen uptake during the hatching period on egg size and temperature.     

Coliforms as a measure of sewage contamination of the River Zambezi

The effect of releasing untreated sewage from Victoria Falls Town into the Zambezi river was determined by bacteriological examination of water samples collected upstream of Victoria Falls and for 22 km downstream. Most probable numbers of faecal coliforms and Escherichia coli were estimated. Water upstream of the falls, on the Zimbabwe side of the river, contained between seven and 130 E. coli per 100 ml. This section of the river was free from major sources of faecal pollution. Below the falls, but before the Victoria Falls Town sewage outfall, numbers of E. coli were between 1.8 × 10² and 1.4 × 10⁴/100 ml, indicating the existence of a sewage discharge other than that from Victoria Falls Town. The river was also highly polluted from the Victoria Falls Town sewage outfall to a point 18.6 km downstream. The highest E. coli count was 3.3 × 10⁴/100 ml and declined slowly to 1.4 × 10³/100 ml 18.6 km downstream of the outfall.     

Incorporation of Radioiodine into the Developing Endostyle of the Larval Lamprey

Incorporation of radioiodine (¹³¹I⁻) into small larvae of the Japanese river lamprey, 14 days after fertilization, was studied by radioautography. A small amount of radioiodine was incorporated into the larvae and became located in the mid-dorsal region of endostylar cells. The incorporation of radioiodine was greatest in endostylar cells near the junction with the anlage of the endostyle duct. It is possible that these cells form the anlage of the endostyle duct, which enters the endostyle.     

The Synthesis and Release of [3H-Tyrosine1]Methionine5-Enkephalin from Guinea Pig Brain Slices

Abstract: Stores of methionine-enkephalin were labelled on the N -terminal by incubation of whole brain slices with [³H]tyrosine (10 °Ci/ml). The ³H radioactivity corresponding to the position of authentic Met-enkephalin after extraction on Amberlite XAD₂ and separation by thin-layer chromatography was taken as an index of synthesis. Maximal incorporation of the labelled tyrosine into Met-enkephalin was attained after 4 h of incubation at 37°C and was inhibited in the presence of 10 μ M cycloheximide. Isolated nerve terminals failed to incorporate any [³H]tyrosine. The labelled compound had opiatelike activity and consisted of the same five amino acids as an authentic standard. Incubations with leucine aminopeptidase indicated that the labelled tyrosine was on the N -terminus and removal of this tyrosine resulted in loss of opiate-like activity. The incorporation of [¹⁴C]glycine, selected as an alternative precursor, was consistent with de novo synthesis and not N -terminal exchange. A radioimmunoassay was also used to quantify the amount of labelled Met-enkephalin. KCl (50 m M ) elicited a Ca²⁺-dependent release of the synthesised [³H]Met-enkephalin from whole brain slices and also from isolated nerve terminals. The release of Met-enkephalin radioimmunoactivity paralleled that of [³H]met-enkephalin. Preliminary investigations have suggested that carbamyl choline inhibited this release and its effect was partially reversed by atropine.     

Experimental Infection of Nosema sp. Ghose in an Unnatural Host Lesioderma sericorne

ABSTRACT. Various doses of a microsporan parasite, Nosema sp., were fed to third and fourth instar larvae of Lesioderma sericorne that infested different types of stored grains. A spore dose of 3 × 10³ spores/individual resulted in a 39% infection rate, reduction in larval and adult weights, and mean spore concentrations of 1.28 ± 0.2 × 10⁸ spores/larva and 1.1 ± 0.2 × 10⁸ spores/adult. At the above dose, mortality was not well marked (about 35% in larvae and 25% in adults). At 3 × 10⁴ spores/individual, the rate of mortality increases to 80% in larvae and 60% in adults. However, more of the pest population (88% of larvae and 73% of adults) died at a dose of 3 × 10⁵ spores/individual. This dose produced mean spore concentrations of 3.91 ± 0.2 × 10⁸ spores/larva and 2.89 ± 0.2 × 10⁸ spores/adult. Insect death was caused by heavy damage to gut epithelia and fat bodies.