摘要:

AbstractImplanted pellets that provide a sustained release of [D‐Ala6Des‐Gly10] LHRH‐ethylamide (GnRHa) were used to induce maturation and ovulation of Southern flounderParalichthys lethostigma. Of the 12 females whose ovaries contained follicles with a maximum diameter ≥500 μm, 11 ovulated for the first time within 90 h of hormone implantation. Only 1 fish with a maximum follicle diameter less than 500 μm ovulated within 2 wk after implantation. Ovulated eggs were manually stripped from the females and mixed with sperm from several males. Most females were spawned 1 to 3 times on consecutive days with variable fertility. One female was spawned 11 times producing 668,000 eggs. Fertility was evaluated by examining the incubated eggs for early stages of embryonic cleavage. The percentage of fertile eggs in subsamples of incubated eggs ranged from 7–95%. The results indicate that GnRHa implants can be used to induce repeated ovulation in this species. The variability in fertility is discussed in relation to

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00263.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractFour separate studies were done on Southern flounderParalichthys lethostigmalarvae during first feeding and metamorphosis to determine the effects of stocking density, salinity, and light intensity on growth and survival. One study used stocking densities of 10, 20, 40, and 80 fish/L during first feeding; the second study compared the growth and survival of larvae stocked at 20 and 33 ppt; and a third experiment evaluated stocking densities of 1/L and 3/L under two different light intensities (1,600 lux vs 340 lux) during metamorphosis. The fourth experiment tested the effects of different salinities (0, 10, 20 and 30 ppt) on larval growth and survival during metamorphosis. Growth and survival (overall 6.9%) were not significantly different (P>0.05) for stocking rates up to 80/L. Larvae placed into 20 ppt salinity had survival through first feeding similar to that of larvae raised at 33 ppt. During metamorphosis, light intensity had no effect (P>0.05) on growth or survival, but fish stocked at 3/L had significantly lower (P0.05) at 10, 20 and 30 ppt, but unmetamorphosed fish did not survive to day 60 at 10 ppt. Based on these results, practical larviculture of Southern flounder may require a two‐step process with high stocking rates (80 fish/L) through first feeding and lower densities (1/L) through metamorphosis. Fingerling production in fertilized nursery ponds might he possible at salinity as low as 20 pp

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00264.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractA series of 20 soil samples was collected from aquaculture areas in 14 provinces of Thailand. Samples represented 10 soil suborders and exhibited wide variation in physical and chemical properties. Soil samples were treated with 0, 25. 50, 100, and 200 ppm phosphorus and incubated under water‐saturated conditions for 1 mo. Amounts of added phosphorus recoverable by water extraction decreased markedly as phosphorus adsorption capacity (PAC) of samples increased (r= 0.88 to 0.96,P<0.01). This suggests that relative abilities of bottom soils to adsorb and release phosphorus added to ponds in fertilizers or feeds can be assessed from PAC data. Because of the importance of phosphorus adsorption by soil in regulating phosphorus availability to phytoplankton in ponds, the PAC appears to be a more useful technique than traditional phosphorus extraction methods as an index of the phosphorus status of aquaculture ponds. The PAC was highly correlated with clay content of soils (r= 0.957;P<0.01), and a knowledge of clay content will permit a rough assessment of phosphorus statu

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00265.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractStable carbon isotope ratios (δ13C) were used to estimate the relative contributions of natural and prepared feeds to the nutrition of golden shinersNotemigonus crysoleucasin ponds. Concurrent feeding trials were conducted in tanks (110 L) and ponds (0.04 ha) to determine the response of golden shiners to three isotopically distinct prepared diets both in the presence (pond) and absence (tank) of natural food. Seston was the primary indicator of the δ13C of natural foods available in the ponds, but δ13C's of free‐swimming, unfed golden shiners provided an additional index. Fish receiving experimental diets were maintained in floating nets within the same ponds. After 6 wk, fish in tanks fed all three diets had acquired the diet label to some degree, while fish in ponds also tracked their respective feeds except for those fed diet 3. This diet contained a large amount of corn meal, which appeared to be poorly assimilated by golden shiners. The use of natural foods by golden shiners fed all three prepared feeds ranged from 40–83% and was inversely correlated with the relative assimilation of the prepared

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00266.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractStrategies to sustain rotifer peak biomass, distribution of rotifer resting eggs in the sediment, and relationship between rotifers and larval fish growth were studied in a series of pond experiments. After the ponds were filled with water, herbivorous rotifers (e.g.,Brachionus calyciflorus) developed first, but were gradually replaced by predatory rotifers (e.g.,Asplanchna). Subsequently, herbivorous cladocerans (e.g.,Moinasp) eventually replaced rotifers and dominated the zooplankton community. The occurrence ofAsplanchnaandMoinaindicated the decline ofB. calyciflorus. Peak rotifer biomass developed 8–10 d after the ponds were filled with water at 20–25 C, 10–15 d at 17–20 C, 15–20 d at 15–17 C, 20–30 d at 10–15 C, and>30 d at20 mg/L) usually lasted 3–5 d, but could be prolonged by pond fertilization or cladoceran controls. A weekly application of dipterex at 0.05 mg/L reduced cladoceran biomass but enhanced rotifer biomass. Our results indicate with a careful management plan it is possible to synchronize the rotifer development wi

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00267.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractAustralian red claw crayfishCherax quadricarinatuswere cultured in nine 0.02‐ha earthen ponds at densities of l/m2, 3/m2and 5/m2for 158 d. Average weight at stocking was 3.2 g. All ponds were provided with a combination of hay and corn silage at a rate of 500 kg/ha per month and a commercial crayfish ration fed at 5%, decreasing to 2% of estimated biomass/d during the growing season. Overall survival rate was 72%, and did not differ among treatments. Final yields and average weights varied significantly with stocking density. Red claw averaged 67 g with an average pond yield of 475 kg/ha at l/m2. At 3/m2and 5/m2, red claw averaged 48 g and 38 g, respectively, and yielded 1,020 kg/ha and 1,422 kg/ha, respectivel

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00268.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe effects of culture parameters of tank color and feeding regimes were examined on larval white bassMorone chrysopsduring 1994–1995. Under high surface illumination (998 lux), dark tank walls were essential for effective prey capture. Larvae reared in clear glass aquaria did not grow and had died by day 6 of the study. In contrast, 48.7% of the larvae reared in black‐walled tanks were alive on day 24 and had grown to 17.2 mm total length (TL). In another study, larvae were fed rotifersBrachionus plicatilisandArtemianauplii in different feeding protocols. In one treatment only rotifers (10/mL) were fed day 1 (4 d post‐hatch), rotifers andArtemia(3/mL) were fed days 2–4, andArtemiafed days 5–15. This protocol produced similar growth (mean size 11.7 mm TL) and survival (mean 30.3%) as slower weaning times from rotifers toArtemia. Juveniles (27‐day‐old, 17.2 mm TL) were converted to a dry crumble diet over a 14‐d period by slow transfer from a combination diet consisting of liveArtemianauplii, frozen adultArtemia, plankton flakes and dry crumbles. Survival offish weaned to the dry diet was 64.5%. Most of the mortalities during the weaning period were fish with uninflated swim bladders which were cannibalized by larger fish. Using the above tank culture techniques, white bass were reared to a mean size of 73.2 mm TL (mean weight 5.8 g) over a 73‐d period. This essentially closes the life cy

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00269.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe potential for commercial culture of hybrid striped bass is promising in many areas of the United States. While several different striped bass hybrids are candidates for culture, differential performance has not been thoroughly evaluated. Comparative performance of two striped bass hybrids was evaluated in six, 757–1, fiberglass tanks receiving a continuous flow of ambient pond water for 397 d. Three replicate tanks were stocked with 50 fingerlings (66 fish/m3) of either striped bass female × white bass male (mean weight 23 g) or striped bass female × yellow bass male hybrids. Fish were fed a 35% protein ration throughout the study, and weight was recorded for all fish at stocking and at 21‐d intervals. White bass hybrids grew significantly faster (0.94 g/d) than yellow bass hybrids (0.59 g/d). Survival to harvest averaged 65% and 44% for yellow bass and white bass hybrids, respectively. A significant difference from the expected 1:1 sex ratio occurred for yellow bass hybrids (100% female), but not for white bass hybrids (56% female). Mean condition factor, 1.63 and 1.39, and fillet percentage, 30.7% and 28.4%, was significantly higher for white bass hybrids compared to yellow bass hy

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00270.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.—Captive‐reared, 10‐mo‐old, male striped bassMorone saxatiliswere sampled monthly for testicular development between February and June 1994. One of the five males sampled in February showed precocious testicular development and had a gonado‐somatic index (GSI) of 1.26%. while the other four fish had immature testes with a mean GSI ± sx, of 0.17 ± 0.03%. Spermiating individuals were present from April to June. In April the average body weight (BW) of spermiating males was 65 ± 4 g and their GSI reached a mean value of 4.75 ± 0.52%. In June, milt collected from ten precocious males contained motile spermatozoa with a mean of 31 ± 7% of the sperm showing forward movement. Mean milt volume and sperm concentration were 1.67 ± 0.41 mL/kg BW and 92.3 ± 1.8 ± 109spermatozoa/mL. respectively. These data show that male striped bass reared in captivity can reach sexual maturity during their first year. This is one year earlier than previously reported for striped bass in mid

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00271.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.–Erythrocyte nuclei from normal diploid (2N) and cold‐shocked triploid (3N) Asian catfishClarias macrocephaluswere comparatively stained with fluorescent stain, ethidium bromide and with a bright‐field stain, Giemsa. Stains were applied to dried blood smears on glass slides, with blood taken from fingerling fish without sacrificing the fish. Both stains produced comparable quality visual comparisons, with significant differences (P<0.001) between nuclear dimensions of 2N and 3N cells. Triploid nuclei were larger and more elongate than diploid nuclei. Karyotypic comparisons revealed that diploid fish had 54 chromosomes, while triploid fish had 81. Ethidium bromide nuclear staining required only 3 min after slides were air‐dried and fixed, while Giemsa staining required more than

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00272.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY