摘要:

AbstractPlasma chemistries were measured in Atlantic salmon (Salmo salar) exposed to elevated nitrite concentrations in an attempt to identify those parameters of potential value as early predictors of nitrite stress in a water‐reuse system. The most notable finding was a decrease in alkaline phosphatase (ALP) activity with increasing time of exposure to elevated nitrite concentrations. Chloride was found to have a protective effect against nitrite toxicity as indicated by higher ALP activities and lower percent methemoglobin in fish exposed to elevated nitrite concentrations at the higher of two chloride concentration

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb00999.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractSeawater‐adapted female chinook salmon (Oncorhynchus tshawytscha) in their second summer were treated with one of three doses of recombinant bovine growth‐hormone (rbGH) administered in a continuous fashion by osmotic pump for approximately five weeks. Untreated fish, sham‐treated fish and fish treated with the low dose of hormone (0.003 μg/g bwt/day) did not differ significantly in their growth performance over the 10 week course of the experiment. By the end of the treatment period (week 6) the mean increases in fork length and weight for these groups were 7.6% and 38.9%, respectively. A dose‐dependent enhancement of growth was observed for the fish treated with the mid (0.016 μg/g bwt/day) and high (0.078 μg/g bwt/day) doses of hormone. After 6 weeks, the fish given the mid dose of rbGH had gained 9.6% in fork length and 45.3% in weight, while the fish treated with the high dose of rbGH had gained 13.9% in fork length and 52.9% in weight. A significant increase in specific growth rate was observed for these latter two groups during the treatment period while condition factor declined in response to the high dose of rbGH. This experiment indicates that chronic administration of growth‐hormone to chinook salmon can result in a dose dependent elevation of growth rate. Results are discussed in relation to previous attempts to accelerate the growth of Pacific salmon with growth‐hormone and the potential for using recombinant growth‐hormone to improve the production characteristics of salmon being cult

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb01000.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractMedian lethal concentrations of un‐ionized ammonia‐nitrogen to red drum (Sciuenops ocellarus) were 0.9 ± 0.14 mg/L (mean ± SE) after 24 h and 0.8 ± 0.16 mg/L after 48 h (salinity = 4.0%, temperature = 20 C, pH = 6.8–7.1). Ammonia moved quickly from the environment into the plasma with 90% of steady state concentrations being reached after 33 minutes. When ammonia‐exposed fish were moved to ammonia‐free water, 90% of the ammonia which had accumulated in the plasma was no longer present after 3.3 minutes. The sensitivity of red drum to environmental ammonia appears to be similar to that of most other fishes tested. Based on the median lethal concentrations for red drum observed in this study and the acute‐chronic concentration ratios for other species of fish, it is suggested that red drum fingerlings be chronically exposed to no more than 0.05 mg/L un‐ionized

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb01001.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractAcute toxicity of nitrite to red drum fingerlings was investigated under static conditions in environments containing 36.0 to 0.6 g/L salinity. The 48 h median lethal concentrations ranged from 85.7 mg/L nitrite‐N (36.0 g/L salinity) to 2.8 mg/L nitrite‐N (0.6 g/L salinity). Plasma nitrite concentrations increased with exposure time during a 48 h study and exceeded environmental concentrations in fish exposed to 9.1 and 5.1 mg/L nitrite‐N (1.4 g/L salinity). During 24 h of exposure, methemoglobin levels increased with increasing environmental nitrite conditions in fish exposed to 3, 6 and 9 mg/L nitrite‐N for 24 h (1.4 g/L salinity). The chloride component of salinity was not as effective in preventing nitrite toxicity as in other species of fish, indicating a potential problem for the culture of red drum in low‐salini

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb01002.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe relationship between water quality, weather, lunar phase and daily changes in crawfish (Proearnbums clurkii) catch per unit effort (CPUE) was determined in five experimental crawfish ponds from March through May, 1984 and 1985. Air and water temperatures, solar radiation, dissolved oxygen, wind velocity, barometric pressure, precipitation and lunar phase were recorded daily during the harvesting phase of the study. Crawfish CPUE (g/trap/24 h) was significantly correlated with water temperature, dissolved oxygen, lunar phase, barometric pressure, wind velocity and the relative density of harvestable size crawfish. Most statistically significant environmental or climatological variables explained less than 20% total daily variation in crawfish CPUE.The nine environmental variables were reduced to four factors—temperature‐harvestable crawfish, cold fronts, rain showers, and lunar phase—with principal‐components analysis. Eighty‐five percent of the variation in daily crawfish catch was attributed to water temperature and relative density of harvestable crawfish, and 7.1% was explained by lunar phase. Rain showers and cold fronts accounted for 4.8 and 2.5% of the daily variation in crawfish CPUE, respectively. Crawfish catch increased with an increase in water temperature and relative abundance of harvestable crawfish, and with short duration rain showers. Conversely, crawfish CPUE declined with the approach of full moon and with passage of co

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb01003.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractFour commercially available crayfish baits and two trap types were evaluated for efficiency in trappingOrconecres virilisandO. immunisfrom 13 unmanaged, contiguous earthen ponds in southern Illinois from May through October 1988. Specifically, this study compared three long‐life baits and one one‐day bait to gizzard shad, and four‐funnel submerged pillow traps to three‐funnel stand‐up pyramid traps in matched‐pair comparisons. Data fromO. immunisharvest was not included in the final evaluation because of the relatively low numbers caught (343). The three long‐life baits attracted significantly moreO. virilisthan did gizzard shad, but the attractability of the one‐day bait was not significantly different from shad. There were no significant differences between four‐funnel pillow traps and three‐funnel pyramid traps or between catch per unit effort from deep or shallow ends of typical culture ponds. These data indicate that wild populations ofO. virilisare susceptible to trapping with typical baits and traps used in the southern United States, and these methods may be more effective than those

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb01004.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractGold, bronze, and black (normal pigmentation) body colors inTilapia mossambicaare controlled by a single autosomal gene with incomplete dominant gene action:GGfish are blackggfish are gold;Ggfish are bronze. Because gold body color is produced by the recessive genotype, it is easy to produce and to maintain a truebreeding population of goldT. mossambicafor commercial purposes. If all other colors are culled, the population will breed true, because gold × gold will always produce 100% gold offspring. TheGgene will be a valuable genetic marker for many genetic studies, such as the production of gynogeneticT. mossambica

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb01005.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe reproductive performance of yearling Florida red tilapia broodstock was studied in laboratory aquaria at salinities of 1 (freshwater), 9, 18, 27 and 36 ppt under controlled photoperiod (14 L:10 D) and temperature (28 C).Spawning was observed at all salinities, although egg production per unit female weight at each spawn was significantly higher at 1 ppt than at higher salinities. An inhibitory effect of salinity on reproductive performance was evidenced by a trend toward lower fertilization, hatching, and survival of prejuveniles with increasing salinity. Fry production per unit female weight declined at salinities above 18 ppt. The results suggest that Florida red tilapia broodstock may be maintained under salinities as high as 18 ppt without impairing fry production, suggesting that hatchery production in brackishwater would be practical in areas where freshwater resources are limiting.

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb01006.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA feeding trial was conducted to study the feasibility of using soybean meal (SBM) to replace fish meal (FM) as a protein source for tilapia feeds containing 24% dietary protein. Replacement levels were 0%, 33%, 67% and 100%. At each replacement level, methionine was either supplemented up to the amount that the 100% FM protein diet contained or not supplemented. The experiment was carried out for eight weeks in a recirculated water system. Fish fed diets in which 100% of the FM was replaced with SBM either with or without methionine supplementation had significantly (P0.05) from that of the control group. These data suggest that when dietary protein level was suboptimal (24%), up to 67% of the FM protein in tilapin feeds can be replaced by hexane‐extracted SBM protein without any adverse effect on tilapia growth and feed conversion rati

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb01007.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe production ofColossoma macropomum(tambaquí), a relatively little studied fish from the Amazon and Orinoco basins, was compared with that ofTilapita nilotica, a fish well known for its good production characteristics. The experimental design was randomized and arranged in 2 × 2 factorial with each species being tested at 2,500 and 10,000 fish/ha. Treatments were replicated three times. Fingerlings (22–31 g) were stocked into 870 m2earthen ponds, fed a commercial diet (25% protein), and harvested after 129 days. Mean yield (kg/ha) for tilapia at high and low density was 3,361 and 917, respectively, and for colossoma was 3,682 and 977, respectively. The yield difference between species was not significant (P>0.05) while the difference between densities was highly significant (P<0.01). Although yield was not different for the species, tambaquí weight gain was significantly greater than that of adult tilapia because of reproduction in the tilapia ponds. Mean tilapia and tambaquí weight gains (g) for low density were 379 and 471, respectively, and 321 and 395, respectively, for high density. Increasing the stocking density fourfold resulted in an almost fourfold increase in net yield for both species, although individual weight gains were not significantly affected. There was no interaction between species and density for the production characteristics studied.This study concluded that under culture conditions that included a short growth period, high quality rations, and stocking rates up to 10,000/ha, production of tambaquí was equal to, or better than that of tilapia. Also, stocking rates lower than 10,000/ha would result in lower yields of both species while not producing a significantly large

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1989.tb01008.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY