Schooling tendency and foraging benefit in the ocean surgeonfish

Summary Field observations of individuallytagged ocean surgeonfish (Acanthurus bahianus) indicated that schooling provided a foraging benefit: an increase in relative forging time. The magnitude of this increase differed among individuals, primarily due to time budgets of the fish when they were not in schools. The proportion of nonschooling time devoted to foraging was positively correlated with fish size, while the proportion of schooling time that was spent forging was similar for all individuals. Schooling tendency (percentage of time in schools) was positively related to magnitude of foraging benefit and negatively related to fish size. When fish size was held constant by partial correlation, schooling tendency remained positively related to foraging benefit. These results provide evidence that fish which derive a greater foraging benefit from school membership spend more time in schools.     

Markov Modulated Poisson Processes for Clustered Line Transect Data

We model the points of the detection along the transect line by a Markov modulated Poisson process (MMPP). The MMPP can accommodate the spatial cluster structure typical of many line transect surveys. The basic idea is that animal density switches between a low and a high level according to a latent Markov process. The MMPP is attractive from a mathematical point of view, as it provides an explicit expression for the likelihood function and other important quantities. We focus on estimating the level of overdispersion in the number of detected animals, as this is important for quantifying the precision of the line transect estimator of animal abundance. The approach is illustrated using both simulated data and data from a minke whale sighting survey conducted in the North Atlantic. Received: August 2004 / Revised: August 2005     

Untersuchungen zum Vorkommen polycyclischer Moschus-Duftstoffe in verschiedenen Umweltkompartimenten

In addition to the three compounds discussed in our first communication (UWSF 6/4, 183–189, 1994) this paper mentions another four substances from the group of the polycyclic musk flavors analysed in a number of detergents and cosmetics, in surface waters, in waste waters from municipal sewage treatment plants and in fish. These four substances are: 6-acetyl-1,1,2,3,3,5-hexamethylindane (AHMI, known for instance under the trade name Phantolide^®), 6,7-dihydro-1,1,2,3,3-pentamethyl-4 (5H)-indanone (DPMI, known for instance under the trade name Cashmeran^®), 7-acetyl-1,1,4,4-tetramethyl-6-ethyltetraline (ATTN, known for instance under the trade name Versalide^®) and 5-acetyl-1,1,2,6-tetramethyl-3-isopropylindane (ATII, known for instance under the trade name Traseolide^®). The results of these analyses show that except for ATTN, the manufacture of which was discontinued some ten years ago, these substances are considered to have an ubiquitous distribution in surface waters. This pollution evidently comes from the use of these flavors in various detergents and cosmetics, from where they enter surface waters via the waste waters from municipal sewage treatment plants. Choosing the Ruhr river as an example, the authors demonstrate that the pollution level is constant and that — due to their lipophilic nature — the compounds accumulate in fish leading to concentrations which markedly exceed those known, e.g., for nitromusk flavors in environmental samples. Two of the main contaminants are HHCB and AHTN, which have the highest concentrations both in the detergents analyzed and in environmental samples.     

Effects of starvation,season, and diet on the free amino acid and protein content of<Emphasis Type="Italic"> Calanus finmarchicus</Emphasis> females

Effects of food availability and season on the free amino acid (FAA) and total protein content of the copepod Calanus finmarchicus females were investigated in two mesocosm experiments on the Norwegian west coast in spring and autumn. Starved C. finmarchicus females showed no change in total FAA content, but the FAA pool composition changed drastically. During the first 10 days of starvation the protein content showed a moderate decline (<2 µg ind ^-1); however, during the following 21 days the total content was drastically reduced, from 63 to 9 µg ind ^-1. This supports the notion of a sequential catabolism of endogenous nutrients during starvation. In females at high food concentrations, the body protein content increased during spring, but decreased during autumn. The FAA pool composition of females differed between spring and autumn in 14 of the 18 FAA investigated. Reduced body protein content and increased proportion of essential free amino acid were observed during starvation. Similar changes were observed in females sampled at the end of the mesocosm experiments in the autumn. The results suggest that mature C. finmarchicus females are in a negative protein balance during autumn, despite high food concentrations, contributing to a lower fitness than in females maturing during the spring.     

Optimal foraging in bumblebees: Why is nectar left behind in flowers?

Summary Queen bumblebees (Bombus appositus) leave nectar behind in Delphinium nelsoni flowers with high-standing crops of nectar. Bumblebees deplete flowers in areas with lower-standing crops. Residual volumes predicted by an optimal feeding hypothesis agree with field measurements.     

The effect of patch constellation on the exchange of individuals between habitat-islands

Metapopulation models assume that inter-patch dispersal dominantly depends on distance between patches and the dispersal capability of organisms in question. We used a spatially explicit, individual-based model to investigate the potential effect of patch constellation on the exchange of individuals between patches. We simulated migration of individuals from a start- into a target-patch with both patches having the same size and shape. Simulation experiments were carried out for four patch constellations and two different movement patterns. Our results demonstrate a substantial effect of patch constellation on the exchange of individuals. They also show that the magnitude and even the direction of this effect crucially depends on their movement pattern. We conclude that particularly for highly correlated movement patterns patch shape and constellation can not readily be ignored when modelling inter-patch dispersal between habitat-islands.