Efficacy of artificial shelters for roach,Rutilus rutilus,against predators in the presence of reeds

Abstract Cormorants, Phalacocorax spp., have great potential to affect recreational fisheries and have increased substantially in abundance over the last decades in UK inland waters. Fabricated refuges provide a potential means of reducing fish losses, yet the benefits of such structures may be marginal if natural shelters are abundant and favoured, or if strong density‐dependence limits refuge use. This study examined the efficacy of artificial shelters in mesocosm enclosures that allowed standardised and replicated observations of roach, Rutilus rutilus (L.), distribution. When given a choice between occupying open water, simulated reedbeds and artificial brushwood shelters, roach used brushwood shelters extensively across a range of fish densities. When fish had a choice of occupying open water or reedbeds offering no overhead cover, they actively avoided reedbeds and used open water almost exclusively. Occupation of reedbeds was positively related to the amount of overhead cover they provided. When artificial brushwood shelters and reedbeds offered complete overhead cover, brushwood shelters were occupied twice as much as reedbeds. Artificial shelters may therefore have wide application in stillwaters with abundant reedbeds unless the reedbeds are coupled with extensive overhead cover.     

Factors affecting formation of methyl nitrite in soils

The formation of CH₃ONO in 11 soils treated with HNO₂ or NaNO₂ in a closed system, was studied by measuring the concentration in the gas space above the soil and by absorbing CH₃ONO in HI. The gaseous concentration of CH₃ONO increased and then decreased following additions of HNO₂ or NaNO₂, and the production of CH₃ONO increased with increasing concentrations of HNO₂ or NaNO₂ added to soils.
The amounts of CH₃ONO trapped in HI were 13.5 to 20.4 times higher than those determined by integrating under the net production curves. The evolved CH₃ONO amounted to 0.4 to 3.5% of added NO₂⁻, and 4.2 to 50% of the gaseous forms of N absorbed by acidic KMnO₄ solution. The CH₃ONO evolved from soils was positively correlated with the methoxy content of the soils, and inversely related to soil pH, with negligible amounts being evolved from alkaline soils. The results show that CH₃ONO is a product of NO₂⁻ decomposition in soils, and indicate that small concentrations of the gas may be produced in N–fertilized soils in which NO₂⁻ accumulates.     

ADSORPTION ON HYDROUS OXIDES I. OXALATE AND BENZOATE ON GOETHITE

The adsorption of oxalic acid on synthetic goethite (α-FeOOH) was studied using adsorption isotherms. Infrared spectra were obtained for goethite-oxalate complexes at several points on the isotherms. On a goethite preparation with a phosphate sorption capacity of 200|μmolg^?1 the amounts of oxalate strongly adsorbed varied from near zero at pH 8 to about l00μmolg^?1 at pH 4 and below. At pH 3.4, the first l00μmolg^?1 of oxalic acid added was strongly adsorbed as a binuclear complex (FeOOC–COOFe), replacing two singly-coordinated OH groups by ligand exchange. At higher concentrations a further 200 μrnol g^?1 of oxalic acid formed a monodentate complex (FeOOC–COOH) so that more oxalate could be accommodated. Benzoic acid was weakly adsorbed on goethite with one benzoate oxygen replacing one singly-coordinated OH. The other oxygen of the COO group fitted into the goethite surface so that the benzene ring was at a high angle to the (100) face.     

Surgical Approach for Removal of Nonarticular Base Sesamoid Fragments of the Proximal Sesamoid Bones in Horses

Objectives— To describe a surgical approach for the removal of nonarticular base sesamoid fragments in performance horses and to report the outcome. Study Design— Retrospective study. Animals— Horses (n=11), 7 months to 10 years of age, with lameness because of nonarticular base sesamoid fragments. Methods— Lameness was localized to the metacarpophalangeal/metatarsophalangeal region by clinical examination or response to diagnostic local anesthesia. Radiographs confirmed the diagnosis of a nonarticular base sesamoid fragment. Surgical removal was performed with an incision over the base of the affected sesamoid through the digital flexor tendon sheath. After identifying the fragment with the aid of needles, a small vertical incision was made in the straight distal sesamoidean ligament (SDSL) and the fragment was freed from its attachments and removed. Six months convalescence and rehabilitation was prescribed for all horses. Results— Eleven horses had 16 nonarticular fragments of the base of the proximal sesamoid bones. Eleven (69%) fragments occurred in the forelimbs with the right front (82%) and medial sesamoid (73%) more commonly affected. Horses were treated by surgical fragment removal. In horses with follow‐up, 9 of 10 returned to their intended use. Conclusions— Surgical removal of nonarticular base sesamoid fragments can be accomplished through a palmar/plantar approach through the digital flexor tendon sheath and SDSL. This “keyhole” approach minimizes damage to the distal sesamoidean ligament attachments to the sesamoid base and allows some horses to return to their intended use. Clinical Relevance— Surgical removal of nonarticular base sesamoid fragments should be considered in horses with performance‐limiting lameness as a result of the fragment.     

Amino acid availability and protein digestibility of several protein sources for Nile tilapia,Oreochromis niloticus

Apparent amino acid availability coefficients and protein digestibility of four animal products [fish meal (FM), meat and bone meal (MBM), poultry by‐product and feather meal] and four plant protein‐rich products [soybean meal (SBM), cottonseed meal‐28, cottonseed meal‐38 and corn gluten meal (CGM)] were determined for Nile tilapia, Oreochromis niloticus. Ingredients were incorporated to a practical reference diet at a 7 : 3 ratio (70% of reference diet and 30% of test ingredient). Chromic oxide was used as external digestibility marker. Among animal products poultry by‐product meal (PBM; 89.7%) and FM (88.6%) presented the highest apparent protein digestibility (APD) while MBM (78.4%) and feather meal (78.5%) presented the lowest APD. Among plant protein‐rich products CGM (91.4%) and SBM (92.4%) presented the highest APD values while cottonseed meal‐28 presented the lowest APD (78.6%). Average apparent amino acid availability of feed ingredients was similar to protein digestibility with 92.3%, 89.6%, 73.4%, 80.7%, 88.9%, 84.4%, 91.2% and 79.7% values for SBM, CGM, cottonseed meal‐28 and 38, FM, MBM, PBM and feather meal respectively. These results indicate that O. niloticus is able to utilize efficiently different feedstuffs.