Abstract
While larger groups tend to be better at making decisions, very few studies have explored how ecological variables, including predation pressure, shape how group size affects decision making. Our cross-population study of wild-caught guppies (Poecilia reticulata) shows that leading individuals from larger groups made faster decisions when deciding to leave the start area and reach the junction of a Y-maze, which allows for compromise over timing. However, at the junction of the Y when the fish needed to make a mutually exclusive decision that does not allow for compromise, there was no effect of group size in high predation fish on decision speed. In fish from low predation habitats, speed was fastest at the intermediate group size with a decline in speed in the largest group size. These results challenge the view that decision making always improves with group size and shows this effect depends on ecological and decision-making conditions.
The low return rate of fish released for stock enhancement has often been attributed to hatchery-reared fish having inferior behavioral characteristics. We tried to improve the behavioral characteristic of red sea bream (Pagrus major) juveniles by using a net-chasing treatment. The fish were provided with 2 min of net chasing twice daily for 3 weeks, following which their behavioral characteristics (emergence from a start area, avoidance response to novel stimulus, and foraging following transfer between tanks) were individually tested and compared with a control group. A predator exposure test was then conducted using marbled rockfish (Sebastiscus marmoratus). Net-chased fish exhibited a shorter latency to emergence, a higher avoidance rate, and an earlier foraging time than the control fish, indicating that the net-chasing treatment may improve adaptability for environmental change and alertness to a novel object. The net-chased fish also exhibited a better survival rate than the control fish, with an odds ratio of 6.76. We suggest that net-chasing training represents an easy and efficient method for improving the behavior of fish for stock enhancement.
Abstract
The paper presents empirical formulae for the calculation of austenite supercooled transformation temperatures, basing on the chemical composition, austenitising temperature and cooling rate. The multiple regression method was used. Four equations were established allowing to calculate temperature of the start area of ferrite, perlite, bainite and martensite at the given cooling rate. The calculation results obtained do not allow to determine the cooling rate range of ferritic, pearlitic, bainitic and martensite transformations. Classifiers based on logistic regression or neural network were established to solve this problem.
This article, based on a study conducted in a multi-ethnic Sure Start programme between 2003–6, explores aspects of the interface between policy, implementation and use of services. The early Sure Start discourse depicted parents both as legitimate recipients of support and as active and aspirational agents. It is argued that the second of these identities, tapping into a ‘social investment’ agenda, increasingly characterised the direction of the policy discourse. Interview data from professionals in the case study area about local need and use of services, however, emphasised the ‘constrained agency’ of many local mothers, and the inappropriateness therefore of the perceived direction of policy.
AbstractTwo questions are discussed: what is the nature of the boundary between the Devonian rocks of the Meneage and of the Start area on the one hand, and the mica- and green schists to the south of them on the other; and are the latter also Devonian or older than Devonian ? The author gives his views on the boundary in both cases, and concludes that the mica- and green schists in both are of Devonian age.
The effect of group size on the speed of decision making depends on compromise and predation risk across populations in the guppy Poecilia reticulata