Effects of Added Shelter and Stocking Density on Growth of Sleepy Cod Oxyeleotris lineolatus in Ponds

Sleepy cod Oxyeleotris lineolatus is a species of freshwater goby in demand in Australian markets by consumers of Asian origin. It is related to marble goby Oxyeleotris marmoratus , the most expensive freshwater food fish in Asia, which is cultured throughout southeast Asia in ponds and cages. The performance of sleepy cod in culture conditions was investigated to assess the viability of farming them in northern Australia. Sleepy cod fingerlings (62.8 ± 0.8 mm total length and 2.56 ± 0.095 g) were stocked into experimental ponds at 32,857 fish/ha, and grown out for 8 mo. Shelter was provided in each of three replicate ponds and was absent in three control ponds. The provision of shelter in juvenile growout was found to be of no benefit, although fish in ponds provided with shelter weighed slightly more per unit length than fish in ponds without shelter. Cannibalism was not a problem in growout, and survival was close to 100%. After the shelter trial was completed, fish were graded into large and small classes (three replicates of each), and grown out without shelter at the same density for 158 d. Following that, fish were again graded, and the largest 30% retained from growout at a density of 8,857 fish/ha (large, 198 ± 6.44 g) or 10,000 fish/ha (small, 48.9 ± 1.27 g). These were grown out for 188 d. Growth of selected stock at low densities was slower than earlier growth rates, although smaller fish gained weight more rapidly than larger fish. Growth rates were better than the only published data for marble goby. Further investigation into high density culture and different genotypes of sleepy cod needs to be undertaken to determine the viability of pond culture.     

Fertility of rainbow trout (Salmo gairdneri) gametes: Gamete viability in artificial media

A series of experiments was performed to test the effect of potassium ions (K⁺) on the storage of rainbow trout (Salmo gairdneri) sperm cells and eggs. Storage of eggs for up to 10 min in saline solutions, extender with K⁺ concentrations of ≤3.4 mM and coelomic fluid did not affect fertility. Fish Extender #6 had a detrimental effect on eggs within 15 s of application and reduced fertility to near zero within 10 min. Variation in the K⁺ concentration indicated that high (≥6.8 mM) concentrations decreased egg fertility while low (≤3.4 mM) concentrations had no effect on fertility. Insemination of eggs before the addition of Fish Extender #6 allowed storage for 14 h. Semen diluted (1:10) in coelomic fluid maintained fertility for 45 s, whereas semen diluted (1:1) in coelomic fluid maintained fertility for 60 min. Fish Extender #6 at K⁺ concentrations between 0 mM and 68 mM had no effect on fertility of semen diluted 1:2.5 after 1 h of storage.     

Effect of feeding time and frequency on the growth and feed utilization of African catfish Clarias gariepinus (Burchell 1822) fingerlings

The effects of feeding time and frequency on the growth, feed utilization and survival of Clarias gariepinus (Burchell 1822; family Clariidae) fingerlings were evaluated in a 25-day study. Groups of African catfish with an initial individual weight of 0.98 ± 0.02 g were offered feeds continuously for 24 h, or during the day or night at different time intervals, with varying meal size. The growth rate was significantly affected by meal times. Widely practised day time feeding with three equal size meals a day gave the lowest growth and highest food wastage. The growth rates of fish fed continuously or during night time following their feed demand were significantly higher with lowest food conversion ratios and food wastage.     

Physiology of seawater acclimation in the striped bass,Morone saxatilis (Walbaum)

Several experiments were performed to investigate the physiology of seawater acclimation in the striped bass, Morone saxatilis. Transfer of fish from fresh water (FW) to seawater (SW; 31–32 ppt) induced only a minimal disturbance of osmotic homeostasis. Ambient salinity did not affect plasma thyroxine, but plasma cortisol remained elevated for 24h after SW transfer. Gill and opercular membrane chloride cell density and Na⁺,K⁺-ATPase activity were relatively high and unaffected by salinity. Average chloride cell size, however, was slightly increased (16%) in SW-acclimated fish. Gill succinate dehydrogenase activity was higher in SW-acclimated fish than in FW fish. Kidney Na⁺, K⁺-ATPase activity was slightly lower (16%) in SW fish than in FW fish. Posterior intestinal Na⁺,K⁺-ATPase activity and water transport capacity (J_v) did not change upon SW transfer, whereas middle intestinal Na⁺,K⁺-ATPase activity increased 35% after transfer and was correlated with an increase in J_v (110%). As salinity induced only minor changes in the osmoregulatory organs examined, it is proposed that the intrinsic euryhalinity of the striped bass may be related to a high degree of “preparedness” for hypoosmoregulation that is uncommon among teleosts studied to data.     

Using behavioral landscape ecology to predict species’ responses to land-use and climate change

Climate change and habitat destruction are widely recognized as major threats to species’ survival. As a result of these anthropogenic impacts, species are often forced into novel landscapes where their persistence is difficult to predict. Knowledge of how individuals move or disperse through the landscape, choose habitat in which to settle, and produce offspring which survive to repeat the process can greatly improve our ability to predict species’ persistence. The field of behavioral landscape ecology uses a strong theoretical base to explore, often experimentally, how the behavior of a particular species is affected by heterogeneous and rapidly changing landscapes and can offer valuable insight for managing species in the face of human-induced environmental changes. When interpreted by modelers, results of landscape-level behavioral experiments can be quantified for use in predictive models. To this end, we summarize the methods and results of research using direct experimental manipulation techniques broken into the following categories: translocations, playback experiments, food resource manipulations, manipulations of reproductive success, direct manipulations of the landscape, and manipulations of predation risk. We review and place in a theoretical framework the results from this emerging body of research regarding how organisms move in and respond to different types of landscapes, both natural and human-altered. We go onto highlight the potential of each experimental method to quantify different processes, which may be useful when interpreted by modelers attempting to parameterize predictive models. Finally, we suggest future directions for experimental research that will allow for greater integration of behavioral landscape ecology and predictive modeling.     

Failure to establish congenital bluetongue virus infection by infecting cows in early pregnancy.

Two groups of 10 pregnant cows were inoculated with bluetongue virus type 11 at either 40 or 60 days of gestation. All the cows became infected as judged by the detection of viraemia and seroconversion but they showed no clinical signs. Seventeen of the cows produced live calves none of which showed any evidence of prenatal infection. After challenge with the same virus all the calves became viraemic and seroconverted. The response to challenge of the two groups did not differ from that of a control group challenged at the same time. It was concluded that the infection of pregnant cows in early gestation with this virus did not result in the transplacental infection of the fetuses and did not produce immunotolerant, latently infected calves.     

Pharmacokinetics of a porcine insulin zinc suspension in diabetic dogs

Ten dogs with naturally occurring diabetes mellitus were injected with a highly purified porcine insulin zinc suspension at a dose according to their expected requirement. Plasma insulin and glucose concentrations were measured at two-hourly intervals over 24 hours following injection. There were either one or two peaks in plasma insulin concentration: one at about four hours (mean 4.3 21.3 [SD]) and another at about 11 hours (mean 11 pM1-85) after the injection. The second insulin peak was seen in only eight dogs. Persistence of elevated plasma insulin concentrations ranged from 14 to 24 hours (mean 17.4 pM 3.65). These results compare favourably with those published for other intermediate-acting insulin preparations used to treat canine diabetes mellitus and suggest that this preparation has useful properties for the successful management of many canine diabetics.     

Performance of Solanum habrochaites LA1777 introgression line hybrids for marketable tomato fruit yield in Asia

Wild relatives of the cultivated tomato (Solanum lycopersicum L.) are major sources of new genetic diversity for tomato improvement. Introgression lines (IL) are near-isogenic lines homozygous for one or several mapped wild DNA fragments in a common recurrent parent. A set of ILs developed by Cornell University from Solanum habrochaites accession LA1777 and recurrent parent E6203 has been made publicly available through the Tomato Genetics Resource Center of the University of California-Davis. Our objective was to identify LA1777 introgressions with potential to increase the marketable fruit yield of tomato grown in the tropics. A subset of ILs were each crossed to CLN2498E (resistant to bacterial wilt and some begomoviruses) to create IL hybrids (ILH). ILH, IL recurrent parent E6203, CLN2498E, and CLN2498E × E6203 (Hchk) were evaluated in replicated trials in Thailand, India, and Taiwan during two dry seasons. Highly significant effects for marketable fruit yield were detected in Thailand and Taiwan. ILH heterozygous for S. habrochaites segments at the bottom of chromosome 1 yielded about 20% than the Hchk at Thailand and Taiwan. Our results agree with previous results from Cornell University researchers who found a segment of S. habrochaites DNA located between TG158 and TG27 associated with increased total fruit yield in previous trials conducted in upper state New York. Yield improvement due to this S. habrochaites introgression can occur over a wide range of environments.