March of the sculpin: measuring and predicting short‐term movement of banded sculpin Cottus carolinae

Movement of fishes through space and time is critical for population regulation and community structuring, but the dispersal of many benthic stream fishes remains unstudied. We used passive integrated transponders to track the short‐term dispersal of 51 banded sculpin Cottus carolinae throughout a 600 m reach of Little Creek in central Tennessee during April and May. Our objectives were to assess the efficacy of recently developed dispersal models, evaluate temporal variability in movement and determine whether individuals switched between stationary and mobile movement behaviours. Observed movement distances did not differ from modelled leptokurtic dispersal kernels estimated using the fishmove package in the R Statistical Environment for 12 of 13 recapture occasions. Leptokurtic dispersal kernel parameters including the mobile component (σ_mob) and shared stationary component (p) were temporally dynamic and differed from static median values reported for fishes in fishmove, while the more abundant stationary component (σ_stat) showed agreement with fishmove. The recapture occasion during which model predictions were not validated was associated with a large flow pulse that stimulated increased movement at the population scale. At the individual scale, 28 of 51 fish switched between stationary and mobile dispersal behaviour and the frequency distribution of switches was leptokurtic. Collectively, our findings reveal an emergent property characterised by consistent upstream movement of banded sculpin despite variability in population‐scale responses to flow and individual‐scale switches in movement behaviour. This paradox represents the march of the sculpin, in which fish diffusively spread upstream at a constant rate despite multiscale variability in movement behaviours.     

The effect of choice of targeted market,production scale,and land tenure on the economics of integrated tilapia-prawn production

Integrated aquaculture systems have the potential to enhance the environmental sustainability of aquaculture production, if economically feasible. Data from integrated tilapia-prawn production trials were used to develop economic-engineering enterprise budgets for ponds with and without substrate that targeted two different types of markets, using two production scales and two forms of land tenure. Inclusion of substrate increased investment and fixed costs and decreased net returns. Recreational markets (live tilapia for fee fishing and live prawns as bait) were profitable, but sales to supermarkets were not. Production scale and land tenure affected economic outcomes with increased pond size and leasing ponds demonstrating greater profitability. Results provide evidence of the need to carefully evaluate economic trade-offs associated with varying commercial-scale applications to increase the likelihood of adoption of new technologies.     

Altered Herbivore Distribution Associated With Focal Disturbance

Natural disturbances historically created structurally diverse patterns across the landscape, and large herbivores concentrated herbivory in areas where disturbance decreased standing senesced biomass that acted as a grazing deterrent through decreased palatability and overall forage quality. However, following European settlement, many natural large-scale disturbance regimes that influence vegetation and herbivore grazing selection were altered or removed and replaced with fine-scale anthropogenic disturbances. It is unclear how fine-scale focal disturbance and alteration of vegetation structure influences livestock distribution and grazing. Therefore we used a tracked vehicle as a disturbance agent in a mesic mixed-grass prairie to assess the influence of focal anthropogenic disturbance on livestock distribution and grazing. Track vehicle disturbance decreased the height of vegetation (P < 0.05) but did not alter plant species composition (P > 0.05). Cattle fecal pat density was greater (P ≤ 0.05) in locations with track vehicle disturbance. Little bluestem tiller height was shorter (P ≤ 0.05) in tracked locations than nontracked locations in grazed treatments, but was not different in nongrazed locations the first growing season following disturbance. Fecal pat density and tiller height were not different (P > 0.05) between tracked and nontracked locations following the second growing season. Therefore, we concluded that fine-scale focal anthropogenic disturbance alters herbivore distribution and defoliation and can maintain structural heterogeneity, but the effect is ephemeral and does not create long-lasting grazing lawns.     

Tallgrass Prairie Plant Community Dynamics Along a Canopy Cover Gradient of Eastern Redcedar (Juniperus virginiana L.)

North American grasslands make up less than 75% of their historic pre-European settlement area, and they continue to be converted to woodlands by woody plant encroachment. Conversion of grassland to woodland alters nutrient cycling, water use, and light penetration, which drives herbaceous plant community dynamics. Because studies examining this relationship among Juniperus species are limited largely to individual trees, we designed a study to examine the relationship between stand-level canopy cover of eastern redcedar (Juniperus virginiana L.) and the herbaceous plant community. We documented herbaceous plant species composition, abundance, and biomass within a North American tallgrass prairie invaded by eastern redcedar in which canopy cover of eastern redcedar ranged from 0% to 80%. Herbaceous species richness declined as a function of increased canopy cover of eastern redcedar and subsequent loss of open space, but this decrease in species richness closely followed a species–area model. Moreover, composition of C₃ and C₄ grasses and forbs did not change with increasing canopy cover. Herbaceous biomass, which declined with increasing canopy cover, varied most within those plots with intermediate canopy cover. While we found that species richness and biomass declined as canopy cover increased, the decline followed a species–area relationship and was without abrupt change typical of ecological thresholds. We recommend additional research with removal of eastern redcedar trees over a range of canopy cover to assess restoration potential along the encroachment gradient.     

COMPETITIVENESS OF U.S. AQUACULTURE WITHIN THE CURRENT U.S. REGULATORY FRAMEWORK

Increased attention has been paid in recent years to both positive and negative effects of increasing numbers of regulations on businesses in the United States. The decline in U.S. aquaculture has been attributed in part to increasing volumes of imports and high feed prices. However, there is increasing concern that the U.S. regulatory environment, as compared to that of international competitors, may also have contributed to this decline. More than 1,300 laws apply to U.S. aquaculture and even though the majority has been issued by individual states and apply only to specific types of aquaculture businesses in that state, the cumulative regulatory burden has increased over time. Major compliance categories include: 1) environmental management; 2) food safety; 3) legal and labor standards; 4) interstate transport of aquatic products; 5) fish health; and 6) culture of commercially harvested species. A substantial portion of the regulatory burden is the managerial and labor time spent on compliance in addition to the direct cost increases. The streamlined one-stop process adopted in Norway appears to have allowed growth of aquaculture within a comprehensive regulatory framework, yet the lack of such a streamlined approach in the United States appears to have contributed to the decline of existing industries and to serve as a deterrent to investment in newly emerging technologies. Favorable regulatory environments in countries that export to the U.S. contrast sharply with the increasingly inefficient, cumbersome and/or restrictive U.S. environment. Such disparities have created competitive disadvantages for U.S. producers. Attention is needed by policy makers to search for streamlining mechanisms and by the scientific community to address the growing competitive disadvantage to U.S. aquaculture to respond to increased global demand for farmed seafood.     

Predicting water intake by yearling feedlot steers

Data from 4 separate beef cattle feedlot experiments, which were conducted at the Southeast Colorado Research Center (SECRC) in Lamar, CO, in 2001, 2003, 2004, and 2007, were utilized in a retrospective longitudinal study investigating possible relationships between daily water consumption (WC), DMI, and weather variables. The data set consisted of 8,209 records from 2001, 2003, 2004, and 2007, with pen based daily WC (L?animal(-1)) and DMI measurements and calculated daily steer BW from April to October in each year. Daily weather data were obtained from the weather station located at Lamar Municipal Airport located approximately 1.9 km from SECRC. Data collected consisted of daily high, low, and mean temperature; high, low, and mean humidity; high, low, and mean sea level pressure; mean wind speed; total precipitation; and average daily wind direction (cosine of radians from due north). Univariate analysis demonstrated that the continuous variables of BW, humidity, and sea level pressure were negatively related (P < 0.0001), whereas DMI, temperature the previous day, daily temperature, change in temperature from the previous day, average wind speed, and the temperature-humidity index (THI) were positively related (P < 0.001) to daily WC. There was a trend (P < 0.06) for the cosine of wind direction (1 = due north and -1 = due south) to be negatively related to WC. The multivariate, parsimonious model predicting average daily WC included (P < 0.05) average humidity, average humidity squared, high temperature squared, high humidity squared, low temperature, low temperature squared, low humidity, average sea level pressure, average wind speed, average daily BW, high sea level pressure, low sea level pressure, high humidity, and low humidity. The generalized R(2) of the parsimonious multivariate model was 0.32. These results indicate that BW and numerous weather factors are related to WC by yearling feedlot steers. Dry matter intake had minimal impact on WC for yearling feedlot steers consuming steam-flaked corn-based high concentrate diets from mid-spring to early fall.     

Effects of gastrointestinal parasites on parasite burden, rectal temperature, and antibody titer responses to vaccination and infectious bovine rhinotracheitis virus challenge

Thirty-three colostrum-deprived Holstein bull calves (initial BW of 131 ± 4 kg) were used to determine the effect of timing of anthelmintic administration relative to vaccination on antibody titer response to vaccine component antigens. When calves were at least 3 mo of age, they were sorted randomly into individual pens and assigned to 1 of 3 treatment groups, treatments consisted of 1) dewormed 2 wk before vaccination (DPV), 2) dewormed at the time of vaccination (DV), or 3) control, vaccinated but not dewormed (CONT). All calves were inoculated with infective larvae of brown stomach worms (Ostertagia ostertagi) and intestinal worms (Cooperia spp.) on d 1, 7, 10, 14, and 18 for a total dose of 235,710 infective larvae per calf. Calves (DPV and DV) were dewormed on d 21 or 35 with a 10% fenbendazole suspension at 5 mg/kg of BW. On d 35, all calves were vaccinated with a modified-live virus respiratory vaccine containing IBRV (infectious bovine rhinotracheitis virus), BVDV-1 (bovine viral diarrhea virus genotype 1), BVDV-2 (BVDV genotype 2), PI-3 (parainfluenza-3), and BRSV (bovine respiratory syncytial virus). During the 103-d experiment, weekly fecal egg counts, blood, and rectal temperatures were collected and health status was recorded daily. Blood samples were obtained weekly to determine serum neutralizing (SN) antibody titers to IBRV, BVDV-1, BVDV-2, and PI-3 and cytokine levels for IL-4, IL-6, TNF-α (tumor necrosis factor-α), and IFN-γ (interferon-gamma). There was a tendency (P < 0.09) for CONT calves to have greater IL-4 concentrations. By design, control calves had greater (P < 0.01) fecal egg counts during the experiment. All calves developed antibody titers to IBRV, BVDV-1, BVDV-2, and PI-3 by d 15 postvaccination. On d 88, all calves were challenged with IBRV and blood samples were obtained on d 88, 89, 90, 93, 95, 98, 99, and 103. All calves had increased rectal temperatures during the final 7 d of the IBRV challenge. However, the CONT group had greater (P < 0.01) rectal temperatures on each sampling day except d 90 compared with the DPV and DV treatments. Therefore, deworming before or at vaccination reduced parasite burden and decreased rectal temperature increase after an IBRV challenge. Deworming strategy had no effect on antibody response to vaccination or IBRV challenge.     

Effects of two different dietary sources of long chain omega-3, highly unsaturated fatty acids on incorporation into the plasma, red blood cell, and skeletal muscle in horses

The objective of this study was to examine the effects of different sources of dietary omega-3 (n-3) fatty acid supplementation on plasma, red blood cell, and skeletal muscle fatty acid compositions in horses. Twenty-one mares were blocked by age, BW, and BCS and assigned to 1 of 3 dietary treatments with 7 mares per treatment. Dietary treatments were: 1) control or no fatty acid supplement (CON), 2) 38 g of n-3 long chain, highly unsaturated fatty acid (LCHUFA) supplement/d provided by algae and fish oil (MARINE) containing alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and docosapentaenoic acid (DPA), and 3) 38 g of n-3 LCHUFA supplement/d provided by a flaxseed meal (FLAX) containing ALA. Each supplement was added to a basal diet consisting of hay and barley and was fed for 90 d. Blood samples and muscle middle gluteal biopsies were taken at d 0, 30, 60 and 90 of supplementation. Plasma, red blood cell and skeletal muscle fatty acid profiles were determined via gas chromatography. Plasma linoleic acid (LA) and ALA were at least 10 and 60% less (P < 0.01), respectively, in the MARINE compared with the FLAX and CON groups. Plasma EPA and DHA were only detected in the MARINE group, and EPA increased 40% (P < 0.001) from d 30 to 60, and DHA 19% (P < 0.01) from d 30 to 90. Red blood cell LA and ALA were not different among treatments. Red blood cell EPA and DHA were only detected in the MARINE group, where EPA increased 38% (P < 0.01) from d 30 to 60, and DHA increased 56% (P < 0.001) between d 30 and 90. Skeletal muscle LA was at least 17% less (P < 0.001) in the MARINE group compared with the other treatments. Skeletal muscle ALA was 15% less (P = 0.03) in the MARINE group compared with FLAX and CON groups. Skeletal muscle EPA was at least 25% greater (P < 0.001) in MARINE group compared with other treatments and increased (P < 0.001) by 71% from d 30 to 60. Skeletal muscle DHA was at least 57% greater (P < 0.001) in the MARINE group compared with other groups and increased (P < 0.001) by 40% between d 30 and 90. As far as the authors are aware, this is the first study to demonstrate that dietary fatty acid supplementation will affect muscle fatty acid composition in horses. Incorporation of n-3 LCHUFA into blood and muscle depends directly on dietary supply of specific fatty acids.     

Phosphorus supplements and fluorosis in cattle—a northern Australian experience

SUMMARY Chronic fluoride toxicosis caused lameness, dental lesions and illthrift in an extensive beef cattle herd in northern Australia. Up to 15% of the herd was lame and the disease forced the culling of large numbers of cows. The source of fluoride was fertiliser-grade monoammonium and diammonlum phosphate fed as part of a mineral supplement. Large quantities of mineral supplement were provided to the cattle because lameness was attributed to phosphorus deficiency, which is endemic in the area. Most lameness developed in the late dry season in the post-lactation phase. Severe lameness was caused by fractured pedal bones.     

The Economics of Intensifying Catfish Production: A Production Function Analysis1

Yields of channel catfish in the United States have increased as a result of higher levels of stocking, feeding and aeration. A Cobb-Douglas production function was estimated using survey data from 66 catfish ponds in West-Central Alabama to determine if further intensification of catfish production in West-Central Alabama would be profitable. Feed, capital, stocking rate, and length of production period explained most of the variation in yield. Values of the marginal products for feed, stocking rate and capital were consistently higher than input costs during the study period. Profit-maximizing levels of input use were higher than the levels of inputs used in West-Central Alabama during the study period. Results indicated that more intensive use of production inputs would increase yield and profits. However, careful interpretation of these results requires consideration of non-profit factors such ns cash Row and risk as well as the specific nature of the data used to develop the production relationship. The method utilized in this study can generally be applied to any aquaculture production system, but the recommendation for more intensive input use is specific to the pond data collected for this study.