An Experimental Investigation of Colonel Blotto Games

"This article examines behavior in the two-player, constant-sum Colonel Blotto game with asymmetric resources in which players maximize the expected number of battlefields won. The experimental results support all major theoretical predictions. In the auction treatment, where winning a battlefield is deterministic, disadvantaged players use a 'guerilla warfare' strategy which stochastically allocates zero resources to a subset of battlefields. Advantaged players employ a 'stochastic complete coverage' strategy, allocating random, but positive, resource levels across the battlefields. In the lottery treatment, where winning a battlefield is probabilistic, both players divide their resources equally across all battlefields." (author's abstract)"Dieser Artikel untersucht das Verhalten von Individuen in einem 'constant-sum Colonel Blotto'-Spiel zwischen zwei Spielern, bei dem die Spieler mit unterschiedlichen Ressourcen ausgestattet sind und die erwartete Anzahl gewonnener Schlachtfelder maximieren. Die experimentellen Ergebnisse bestätigen alle wichtigen theoretischen Vorhersagen. Im Durchgang, in dem wie in einer Auktion der Sieg in einem Schlachtfeld deterministisch ist, wenden die Spieler, die sich im Nachteil befinden, eine 'Guerillataktik' an, und verteilen ihre Ressourcen stochastisch auf eine Teilmenge der Schlachtfelder. Spieler mit einem Vorteil verwenden eine Strategie der 'stochastischen vollständigen Abdeckung', indem sie zufällig eine positive Ressourcenmenge auf allen Schlachtfeldern positionieren. Im Durchgang, in dem sich der Gewinn eines Schlachtfeldes probabilistisch wie in einer Lotterie bestimmt, teilen beide Spieler ihre Ressourcen gleichmäßig auf alle Schlachtfelder auf." (Autorenreferat

Comparative effects of temperature on suspension feeding and energy budgets of the pearl oysters Pinctada margaritifera and P. maxima

This study assessed the effects of seasonal temperatures on suspension feeding, related physiological parameters and energy budgets in 2 pearl oysters, Pinctada margaritifera and P. maxima. Pearl oysters that were acclimatised at approximately 19, 23, 28 and 32°C in the field were tested in the laboratory at these temperatures. Clearance rate (CR), absorption efficiency (ae), absorbed energy (AE), respired energy (RE), excreted energy (EE) and the value of (AE - RE) were significantly affected by temperature. They usually increased with increasing temperature. ae, RE, EE and the value of (AE - RE) differed significantly between the pearl oyster species. P. margaritifera had a significantly higher CR than P. maxima at 19°C. P. maxima had higher ae than P. margaritifera at 28 and 32°C. As a result, P. margaritifera had greater AE than P. maxima at 19°C, but the latter species had greater AE at 32°C. Temperature significantly affected the RE of P. margaritifera over a wider temperature range (19 to 32°C) than P. maxima (19 to 23°C). However, interspecific differences in RE were only significant at 32°C. P. maxima had significantly higher EE at 32°C than P. margaritifera, although this energy accounted for a very small portion of AE (<5%). P. maxima exceeded P. margaritifera in Scope for Growth [SFG = (AE - RE) - EE] at 32°C, but the latter species had greater SFG at 19°C. These results agree with observations of the occurrence of P. margaritifera at higher latitudes and lower temperature habitats. The temperature effects on suspension feeding, related physiological parameters and SFG indicate that there will be marked seasonal variations in growth in both species in environments where water temperatures vary seasonally. In bioenergetic terms, the optimum temperature ranges for these pearl oysters are approximately 23 to 28 and 23 to 32°C for P. margaritifera and P. maxima, respectively

Comparative effects of microalgal species and food concentration on suspension feeding and energy budgets of the pearl oysters Pinctada margaritifera and P. maxima (Bivalvia: Pteriidae)

This study aimed to determine the influence of microalgal species and food concentration on various physiological parameters and Scope for Growth (SFG) in adults of 2 pearl oysters, Pinctada margaritifera and P. maxima. Clearance rate, pseudofaecal production rate, absorption efficiency, respiration rate and excretion rate were determined over a range of food concentrations using 2 microalgal diets, Tahitian Isochrysis sp. (T-Iso) and Dunaliella primolecta at 28°C. Clearance, pseudofaecal production and respiration rates were significantly affected by microalgal diet. From these results, and because of the higher energy content of T-Iso, pearl oysters feeding on T-Iso had maximum values of SFG that were 1.5 to 2.1 times higher than when feeding on D. primolecta. Clearance rate and absorption efficiency were significantly related to food concentration as negative exponential relationships (p < 0.001). Generally, pseudofaecal production, respiration and excretion rates were significantly related to food concentration as positive linear relationships (p < 0.005). Optimal food concentrations for maximum SFG for P. margaritifera and P. maxima were 1 to 2 mg 1-1 and 2 to 3 mg l-¹, respectively. P. maxima was better adapted to a wider range of food concentrations. P. maxima maintained positive SFG up to 9 mg l-¹ food concentration when feeding on T-Iso and up to 7 mg l⁻¹ when feeding on D. primolecta, while equivalent values for P. margaritifera were 7 mg l⁻¹ and 5 mg l⁻¹, respectively. These results are in accordance with P. maxima occurring in a wider range of habitats than P. margaritifera, and experiencing greater concentration ranges of suspended particulate matter

Water quality, sediment and biological parameters at four nearshore reef flats in the Herbert River Region, Central Great Barrier Reef 2003

This report summarises the results of a study from 1995 to 1997 estimating the nutrient status of four inshore fringing reef flats in the vicinity of the Herbert River mouth in the central section of the Great Barrier Reef World Heritage Area. The study sites were at Great Palm Island, Fantome Island, and North Island of the Brook Islands group. Variables measured were nutrient parameters and biological parameters that may serve as proxy measures for nutrient availability

Feeding adaptations of the pearl oysters Pinctada margaritifera and P. maxima to variations in natural particulates

The tropical pearl oysters Pinctada margaritifera (Linnaeus) and P. maxima Jameson are suspension feeders of major economic importance. P. margaritifera occurs in coral reef waters characterised by oligotrophy and low turbidity. P. maxima habitats are generally characterised by high terrigenous sediment and nutrient inputs, and productivity levels. These differences in habitat suggest that P. margaritifera will feed more successfully at low food concentrations, while P. maxima will cope with a wider range of food concentrations and more silty conditions. The effect of varying concentrations of natural suspended particulate matter (SPM) on clearance rate (CR), pseudofaeces production, absorption efficiency (abs.eff.), respired energy (RE) and excreted energy (EE) was determined for P. margaritifera and P. maxima. The resultant scope for growth (SFG) was determined and related to habitat differences between the oysters. There was no selective feeding on organic particles in either species. P. margaritifera had higher CR at low SPM concentration (<2 mg l⁻¹), while P. maxima had higher CR under turbid conditions (SPM: 13-45 mg l⁻¹). The latter species produced less pseudofaeces in relation to its filtration rates; consequently, this species ingested more SPM than P. margaritifera. P. maxima had positive SFG over a wider range of SPM concentrations (up to 30-40 mg l⁻¹) while P. margaritifera maximised SFG under low SPM conditions (<3 mg l⁻¹). Thus feeding responses and energy balance reflected the typical habitats of each species. P. margaritifera retained smaller particles than P. maxima, enabling it to consume a wider particle size range of SPM at low food levels. P. maxima was adapted to its environments of greater SPM load through greater ingestion rates and higher digestive ability. The optimum SPM concentrations and particle size range for P. margaritifera (SPM < 5 mg l⁻¹, size > 3 µm) and P. maxima (SPM = ca 3 to 15 mg l⁻¹, size > 4 µm) may be used for selection of optimum pearl culture sites

The pearl oysters, Pinctada maxima and P margaritifera, respond in different ways to culture in dissimilar environments

Growth, Condition Index (CI) and survival of the pearl oysters, Pinctada maxima and R margaritifera, were measured in three size groups of oysters over 14 months at two dissimilar environments in the Great Barrier Reef lagoon. These were the Australian Institute of Marine Science (AIMS) in a mainland bay and Orpheus Island Research Station (OIRS) in coral reef waters. Temperature, suspended particulate matter (SPM) and particulate organic matter (POM) were monitored during the study. Temperature at AIMS fluctuated more widely than at OIRS both daily and seasonally, with annual ranges 20-31 degrees C and 22-30 degrees C, respectively. Mean SPM concentration at AIMS (11.1 mg l(-1)) was much higher than at OIRS (1.4 mg l(-1)) and fluctuated widely (2-60 mg l(-1)). Mean POM level was also substantially higher at AIMS, being 2.1 mg l(-1) compared with 0.56 mg l(-1) at OIRS. Von Bertalatiffy growth curve analyses showed that P. maxima grew more rapidly and to larger sizes than P. margaritifera at both sites. For the shell height (SH) of R maxima, growth index phi'=4.31 and 4.24, asymptotic size SHinfinity = 229 and 205 mm, and time to reach 120 mm SH (T-(120))= 1.9 and 2.1 years at AIMS and OIRS, respectively. While for P margaritifera, phi'=4.00 and 4.15, SHinfinity = 136 and 157 mm, and T-(120) = 2.5 and 3.9 years at AIMS and OIRS, respectively. R maxima had significantly lower growth rates and lower survival of small oysters during winter compared with summer. There were, however, no significant differences between the two sites in growth rates of P. maxima and final Cl values. In contrast, P. margaritifiera showed significant differences between sites and not seasons, with lower growth rates, survival of small oysters, final Cl values and asymptotic sizes at AIMS. The winter low temperatures, but not high SPM at AIMS, adversely affected P. maxima. Conversely, the high SPM levels at AIMS, but not temperature, adversely affected P. margaritifera. This was in accordance with earlier laboratory-based energetics studies of the effects of temperature and SPM on these two species. P maxima has potential to be commercially cultured in ca. > 25 degrees C waters with a wide range of SPM levels, including oligotrophic coral reef waters with appropriate particle sizes. It is possible to culture R margaritifera in turbid conditions, but its poor performance in these conditions makes commercial culture unlikely. (c) 2005 Elsevier B.V. All rights reserved