Variability in the performance of juvenile Chinook salmon is explained primarily by when and where they resided in estuarine habitats

Estuarine habitats provide rearing opportunities for the juvenile life stage of anadromous fishes. Because survival is positively correlated with juvenile performance, these estuarine habitats play an important role in population abundance and productivity. To provide information for the recovery of several depressed stocks of Chinook salmon in the Columbia River Basin, we sought to identify the factors that explain variability in performance. Using otolith‐derived estimates of juvenile somatic growth rate as an index of recent performance, we observed a negative nonlinear relationship between growth rate and day of year, and a decreasing and increasing trend of growth rate over the 8 years of this study and distance from the river mouth respectively. Using a generalised linear modelling approach, we found that variability in juvenile somatic growth rate was best explained by where and when individuals were collected, their body size, contaminant loads, stock of origin, and whether a fish was hatchery produced or unmarked. Lastly, we argue that a considerable improvement to the growth rate of juveniles in estuarine habitats is physiologically possible. The results of this 8‐year study provide a baseline of the performance of juvenile Chinook salmon to evaluate habitat restoration programs and to compare against future anthropogenic conditions.     

Comparing the behavioural thermoregulation response to heat stress by Atlantic salmon parr (Salmo salar) in two rivers

Climate change is expected to increase the frequency and magnitude of extreme thermal events in rivers. The Little Southwest Miramichi River (LSWM) and the Ouelle River (OR) are two Atlantic salmon (Salmo salar) rivers located in eastern Canada, where in recent years, water temperatures have exceeded known thermal limits (~23°C). Once temperature surpasses this threshold, juvenile salmon exploit thermal heterogeneity to behaviourally thermoregulate, forming aggregations in coolwater refuges. This study aimed to determine whether the behavioural thermoregulation response is universal across rivers, arising from common thermal cues. We detailed the temperature and discharge patterns of two geographically distinct rivers from 2010 to 2012 and compared these with aggregation onset temperature. PIT telemetry and snorkelling were used to confirm the presence of aggregations. Mean daily maximum temperature in 2010 was significantly greater in the OR versus the LSWM (p = 0.005), but not in other years (p = 0.090–0.353). Aggregations occurred on 14 and 9 occasions in the OR and LSWM respectively. Temperature at onset of aggregation was significantly greater in the OR (T_onset = 28.3°C) than in the LSWM (T_onset = 27.3°C; p = 0.049). Logistic regression models varied by river and were able to predict the probability of aggregation based on the preceding number of hours >23°C (R² = 0.61 & 0.65; P₅₀ = 27.4°C & 28.9°C; in the OR and LSWM respectively). These results imply the preceding local thermal regime may influence behaviour and indicate a degree of phenotypic plasticity, illustrating a need for localised management strategies.     

Ecosystem services as the products of land system dynamics: lessons from a longitudinal study of coupled human–environment systems

Context

We address understanding of whole-system and landscape-based approaches to the ecosystem services framework by considering the supply of provisioning services and the dynamics of agricultural land use in Scotland between 1940 and 2016.

Objectives

To characterise and understand the dynamics of change in provisioning services from agriculture in Scotland over the period 1940–2016. To identify ways in which funds of capitals and flows of inputs and output ecosystem goods are linked to land management practices and policies at a national scale.

Methods

Data describing agricultural land use, production, financial and energy inputs and outputs, and drivers of change in land use in Scotland are analysed with an accounting framework that links funds of natural, human, physical and financial capital, with flows of goods and services. Flow–fund ratios are used as benchmarks of system performance and dynamics.

Results

Scotland’s agriculture has modernised since 1940 and become more efficient in conversion of resources, with a consequent increase in delivery of provisioning goods and services. Although the energy ratio, and flow of goods per unit hectare and per unit labour have increased, the inputs necessary to maintain those flows of ecosystem goods are also increasing, even as their relative economic costs decrease. Increases in use of fertiliser suggests that production from the soil, as a natural capital fund, is not being conserved without a large, and increasing, input. Analysis of the complexity of the coupled agricultural land system also suggests that land management rather than biodiversity is a necessary subject for evaluation of provisioning services from agriculture. Understanding of ecosystem services based on accounts that integrate inputs, outputs and flows from funds of natural, human, social, financial and physical capitals, provides a process-based foundation for improved understanding of ecosystem services and human–environmental relationships.

Conclusions

Adopting an accounting approach for understanding the role of agricultural land use for supply of provisioning services, and particularly examining a long time-series of accounts, enables understanding of land changes and underlying drivers, as well as the contribution of cultural and other aspects of human systems coupled with environment systems. Accounting for ecosystem services using costs as well as benefits, and use of metrics beyond financial benefit, supports debate and evaluation of trade-offs between services and has direct relevance for decision- and policy-making.

     

Consistency of results from the Vettest 8008 clinical biochemistry analyser.

Findings are presented on the precision of a clinical biochemistry analyser designed specifically for veterinary use. Twenty biochemical analytes have been examined in detail for variation within and between runs. The results indicate that the analyser can provide high precision for all the analytes with the possible exception of calcium, and suggest that the instrument can be used with confidence in the practice laboratory to aid diagnosis and to monitor biochemical changes in animals receiving treatment.     

Comparison of sesame cake and cottonseed as supplementary sources of protein to weaned N'Dama bull calves in The Gambia

Summary The potential for increased productivity of N'Dama cattle in response to small supplementary inputs of proteinaceous by-products has been shown to be substantial under village husbandry conditions in The Gambia. Young N'Dama bulls were used to compare sesame cake with cottonseed as sources of supplementary protein during the wet and early dry seasons of 1987. They were fed 0, 40, 80 or 160 g crude protein/day in these forms for four months. Supplementation significantly increased growth rate from 169 g/d in controls to means of 272 and 271 g/d for those given sesame cake and cottonseed respectively; there were no significant differences among the supplemented groups. During the four months of the dry season immediately after supplementation ceased all previously supplemented groups grew significantly more rapidly than the controls (at leastP<0·05), indicating a substantial carry over effect of the supplements. Over this period the mean gain of the groups previously given sesame cake exceeded that of those that had received cottonseed (217 cf. 158 g/d;P<0·01). The economic benefits of these responses were substantial.

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Comparacion de torta de sesamo y de semilla de algodon como fuente suplementaria de proteina para terneros destetos N'Dama en Gambia

Resumen Se ha demonstrado el potencial para incrementar la productividad del ganado N'Dama, como resquesta a peque?as cantidades de insumos suplementarios de proteína, bajo condiciones de villorrio en Gambia. Se utilizaron terneros destetos N'Dama par comparar la torta de sésamo y de semilla de algodón como fuente de proteína suplementaria durate la estaicón lluviosa y principio de la seca del a?o 1987. Se les dió a los animales 0, 40, 80 o 160 g de proteína cruda/día en éstas formas durante cuatro meses. La suplementación incrementó significativamente la tasa de crecimiento, de 169 g/día en controles a 272 y 271 g/día en aquellos que recibieron torta de sésamo y de algodón respectivamente; no hubo diferenca estadística entre los grupos suplementados. Durate los cuatro meses de la estación seca inmediatamente después de que la suplementación fue suspendida, todos los grupos que habían sido suplementados crecieron sgnificativamente más rápido que los controls (P<0·05), indicando un efecto compensatorio en los suplementados. Durante ese período la media de crecimento de los grupos que recibieron torta de sésamo excedió a aquella de los que habían recibido torta de algodón (217 cf. 158 g/d;P<0·01). Los beneficios económicos de estos resultados fueron substanciales.

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Comparaison entre le tourteau de sesame et la graine de coton comme sources complementaires de proteines pour les taurillons N'Dama sevres en Gambie

Résumé Le potentiel de réponse à de petites quantités supplémentaires de sous-produits proteiniques pour accroitre la productivité de bétail N'Dama, s'est révélé manifeste, dans les conditions d'élevage villageois en Gambie. De jeunes taureaux N'Dama ont été utilisés pour comparer le tourteau de sésame et la graine de coton en tant que source de complémentation protéinique pendant la saison sèche et le début de la saison humide au cours de l'année 1987. Ils ont re?u respectivement 0, 40, 80 ou 160 g de proteines brutes par jour sus ces deux formes pendat quatre mois. Cette supplémentation a accru de fa?on significative le taux de croissance, de 169 g/jour pour les témoins jusqu'à des moyennes de 272 et 271g/jour respectivement pour ceux qui ont re?u du tourteau de sésame et de la graine de coton. Quant aux groupes complémentés, il n'ont révélé aucune différence significative. Pendat les quatre mois de la saison sèche et immédiatement après l'arrêt de la supplémentation, tous les lots ayant fait précédemment l'objet d'une distribution complémentaire ont eu une croissance significativement plus rapide que les animaux témoins, du moins pourP<0,05, ce qui indique un effet important de report des suppléments. Durant cette période, le gain moyen des lots qui ont re?u le tourteau de sésame a dépassé celui des lots auxquels on a donné de la graine de coton, soit 217 g/jour contre 158 g/jour pourP<0,01. Les profits économiques de ces réponses ont été appréciables.

     

Economies of Pond Size for Hybrid Striped Bass Growout1

The objective of this study was to evaluate the relationship of pond size and hybrid striped bass growout profitability as an alternative source of farm income in the Mid-Atlantic region. A dynamic, whole farm, Montdarlo capital budgeting simulation model (AQUASIM) and stochastic dominance with respect to a function technique were used to analyze the economics of hybrid striped bass growout from phase II to market production stage for eight farms categorized by pond sizes. Three scenarios are assumed to examine the effects of pond-size dependent changes in feed conversion efficiency and fingerling survival rates on discounted after-tax net present values and probabilities of economic survival and success. Optimal pond sizes were found to be in the 2.5 acre to 10 acre range.     

Characteristics of Rice Cultivars with Implications for Crawfish Double Cropping1

Twenty-five domestic rice (Oryza sativa L.) cultivars were evaluated in a simulated rice/crawfish double cropping system in southwest Louisiana during 1983 and 1984. Wide variation was observed among cultivars in parameters believed to be important for maximizing productivity in such a system. Mean maturity ranged from 99 (Labelle) to 118 days (Starbonnet), while height ranged from 76 (Bellemont) to 130 cm (Della, Nato). Significant differences in grain yield response were observed, with yields ranging from 4,101 (Bluebelle) to 6,665 kg/hectare (Newbonnet). Straw dry matter production varied greatly, from 3,831 (Bellemont) to 9,170 kg/hectare (Della), and was positively correlated with plant height (r = 0.64; P = 0.0001). Ratoon biomass production was negatively correlated with both grain yield (r = -0.39; P = 0.0001) and maturity group (r = -0.69; P = 0.0001). Plant senescence at grain maturity also varied greatly and appears to be a factor in post-harvest ratoon capability. Early or very early maturing cultivars with both proven grain production and good ratooning capability appear best suited. Cultivar selection should be based upon individual farm situations and currently employed agronomic practices.