Integration of economic and hydrologic models: Exploring conjunctive irrigation water use strategies in the Volta Basin

We describe the development, calibration and preliminary application of a dynamically coupled economic–hydrologic simulation–optimization model ensemble for evaluating the conjunctive use of surface and groundwater in small reservoir-based irrigation systems characteristic of the Volta Basin, Africa. We focus on a representative small reservoir-irrigation system located in the Antakwidi catchment in Ghana. The model ensemble consists of the physical hydrology model WaSiM-ETH and an economic optimization model written in GAMS. Results include optimal water storage and allocation regimes for irrigated production, given conjunctive surface water and groundwater systems. The goal of our research, conducted within the GLOWA Volta project, is to develop a decision support system for improving the management of land and water resources in the face of potential environmental change in the Volta Basin.     

Habitat overlap of juvenile and adult lake trout of Great Bear Lake: Evidence for lack of a predation gradient?

A range of organisms, from plankton to fish, commonly shift their habitat distributions horizontally or vertically due to predation risk. Juvenile lake trout, Salvelinus namaycush, are generally viewed as occupying deep areas of lakes to decrease predation pressure from adults. In contrast, we found that juvenile lake trout from Great Bear Lake, NT, Canada, occupied a variety of habitats and from shallow to deep depths (0–150 m), overlapping with adult lake trout. No evidence occurred for a length depth‐based segregation (e.g., ontogenetic shift). Genetic variation was also similar among juveniles in the different depth zones. However, isotopic niches and C:N ratios among juveniles showed some variability in niche widths and positions for individuals caught from the 51–150 m zone compared to juvenile individuals caught from 0–20 m and 21–50 m zones. The uniformly distributed adult lake trout in Great Bear Lake may evenly distribute predation pressure (including cannibalism) across shallow‐ and deep‐water habitats more than in other lakes. As a result, juveniles may respond to differences in foraging opportunities rather than predation risks. Juvenile lake trout did not appear to conform to the general pattern of juveniles seeking a deep‐water refuge to reduce predation risks. In contrast, juvenile lake trout of Great Bear Lake displayed broad resource use across all depths and habitats.     

Sex-Reversal of Oreochromis aureus by Immersion in Mibolerone,a Synthetic Steroid1

Mibolerone (MI), a synthetic steroid, was used to sex-reverse undifferentiated Oreochromis aureus fry. Fry were exposed to 0.0, 0.3, 0.6, or 1.0 ppm MI in static-water solutions for five weeks (immersion treatments) or were fed a diet containing 1.0 ppm MI for four weeks in a flow-through system. Following hormone treatment, the fish were grown to over 60 mm total length prior to sex determination using gonadal squash examination. Fish immersed in 1.0, 0.6, or 0.3 ppm MI had average tissue MI concentrations of 14.4, 5.6, and 3.3 ppm, respectively. Immersion in either 1.0 or 0.6 ppm MI for five weeks resulted in an average of 82% males and 18% ovo-testicular fish (inter-sex fish) with no gonadal females being produced. Exposure to 0.3 ppm MI resulted in 78.7% males, 20.7% ovo-testicular fish, and 0.7% gonadal females. Feeding a diet containing 1.0 ppm MI resulted in 85% males, 11% ovo-testicular fish, and 4% gonadal females. Fry growth and survival were negatively correlated with the MI concentration of the immersion treatments. Exposing tilapia fry to static-water solutions of 0.6 ppm MI for five weeks appears to be a feasible method of eliminating the production of functional females. Immersion solutions should be changed at least weekly to maintain an effective hormone concentration.     

Epidemiologic study of toxoplasmosis on a sheep ranch

An epidemiologic study was done on a ranch in northern California on a flock of ewes that had a history of abortions, mummified fetuses, weak or stillborn lambs, and failure to conceive. Of 56 ewes tested, 33 (59%) had serum agglutinating antibodies against Toxoplasma gondii, with an unusually high proportion of high titers. Over a 2-year-period, reproductive problems were higher (39% to 42%) among the seropositive ewes than among the seronegative ewes (9% to 33%). Of 89 sera received from persons and 7 species of animals on the ranch, 44 (49%) were found to be seropositive to T gondii, including seropositive members of a family of 6. The rancher's wife and teenage daughter, both of whom were involved with lambing, had serum titers exceeding 4,096. Other members of the family not involved with lambing were seronegative by the indirect hemagglutination test. The 2 infected persons are known to have come in contact with placentas, birth fluids, fetuses, and colostrums from these infected ewes.     

Haematological characteristics of the common marmoset (Callithrix jacchus jacchus)

Blood cell indices and parameters of haemostasis were studied in the common marmoset. The majority of the results were similar to those found in man. Differences from man were that the prothrombin time was shorter in the marmoset, higher concentrations of aggregating stimuli were required to cause platelet aggregation, and marmoset platelets did not aggregate under the influence of adrenalin. There was sexual dimorphism evident in the data for fibrinogen concentration and for platelet count, both of which were higher in females than in males. Marmoset platelets were very similar in ultrastructure to those of man.     

Habitat functional response mitigates reduced foraging opportunity: implications for animal fitness and space use

Context

Animals selectively use landscapes to meet their energetic needs, and trade-offs in habitat use may depend on availability and environmental conditions. For example, habitat selection at high temperatures may favor thermal cover at the cost of reduced foraging efficiency under consistently warm conditions.

Objective

Our objective was to examine habitat selection and space use in distinct populations of moose (Alces alces). Hypothesizing that endotherm fitness is constrained by heat dissipation efficiency, we predicted that southerly populations would exhibit greater selection for thermal cover and reduced selection for foraging habitat.

Methods

We estimated individual step selection functions with shrinkage for 134 adult female moose in Minnesota, USA, and 64 in Ontario, Canada, to assess habitat selection with variation in temperature, time of day, and habitat availability. We averaged model coefficients within each site to quantify selection strength for habitats differing in forage availability and thermal cover.

Results

Moose in Ontario favored deciduous and mixedwood forest, indicating selection for foraging habitat across both diel and temperature. Habitat selection patterns of moose in Minnesota were more dynamic and indicated time- and temperature-dependent trade-offs between use of foraging habitat and thermal cover.

Conclusions

We detected a scale-dependent functional response in habitat selection driven by the trade-off between selection for foraging habitat and thermal cover. Landscape composition and internal state interact to produce complex patterns of space use, and animals exposed to increasingly high temperatures may mitigate fitness losses from reduced foraging efficiency by increasing selection for foraging habitat in sub-prime foraging landscapes.

     

Control of introduced mammalian predators improves kaka Nestor meridionalis breeding success: reversing the decline of a threatened New Zealand parrot

The kaka (Nestor meridionalis) is a threatened, endemic New Zealand parrot that is declining primarily because of predation by introduced mammals. Numbers of female kaka surviving to sexual maturity more than compensated for adult female mortality at three sites with predator control but not at three unmanaged sites. Nesting success at the sites with predator control was significantly greater (?80%) than at unmanaged sites (?38%) while predation on adult females was significantly less (5% c.f. 65%). Predation was the most common cause of nesting failure at all sites. Stoats (Mustela erminea) appeared to be the main predator, although evidence of possum (Trichosurus vulpecula) predation on eggs, nestlings and nesting females was also found. These results suggest that control of stoats and possums can potentially reverse the decline of the kaka on the main islands of New Zealand.     

Nutritional degenerative myopathy in a population of captive bred Uroplatus phantasticus (satanic leaf-tailed geckoes).

Severe generalized degenerative myopathy was diagnosed in a population of captive bred satanic leaf-tailed geckoes (Uroplatus phantasticus). The diagnosis was based on characteristic histological changes and response to dietary therapy. This is the first reported case of nutritional myopathy in the satanic leaf-tailed gecko.