T. Deprez

Macrodebris and microplastics from beaches in Slovenia.

The amount of marine debris in the environment is increasing worldwide, which results in an array of negative effects to biota. This study provides the first account of macrodebris on the beach and microplastics in the sediment (shoreline and infralittoral) in relation to tourism activities in Slovenia. The study assessed the quality and quantity of macrodebris and the quality, size and quantity of microplastics at six beaches, contrasting those under the influences of tourism and those that were not. Beach cleanliness was estimated using the Clean Coast Index. Tourism did not seem to have an effect on macrodebris or microplastic quantity at beaches. Over 64% of macrodebris was plastic, and microplastics were ubiquitous, which calls for classification of plastics as hazardous materials. Standard measures for marine debris assessment are needed, especially in the form of an all-encompassing debris index. Recommendations for future assessments are provided for the Adriatic region.

Idiomysis mozambicus, a new mysid species (crustacea: mysidacea) from Mozambique

Idiomysis mozambicus is described from coastal waters of Mozambique. The species can be distinguished from the other species of the genus by the one-segmented antennal scale, the two-segmented exopod of the fourth male pleopod and the bluntly pointed rostrum.

Estimating Muricid abundances from trapping methods used in Mediterranean Tyrian Purple industry

A new statistical method based on a stochastic dynamic model is proposed to assess population abundances of murcid species at scales relevant to both Ancient and Modern artisanal, coastal fisheries. Motivated by the long-term goal of reconstructing the dynamics of exploited murex populations during Antiquity, the objective was to quantify the population density of the banded-dye murex, Hexaplex trunculus (Linnaeus, 1758) from successive captures with baited traps, using a method similar to the technique employed in the Mediterranean purple dye industry. A stochastic model simulating cumulative captures while taking into account high variability was developed and calibrated with data acquired during a field experiment conducted on Crete Island, near Heraklion. Sampling devices were deployed in two shallow water habitats. The traps’ catchability and the Effective Area of Attraction were estimated using the individual speed and behavioural response toward the bait observed during independent laboratory experiments. The average density of H. trunculus was estimated at 2.2 ± 1.4 SE individuals per square meter, with no significant differences between seagrass and rocky habitats, respectively. The clearing time (the time to catch all individuals within reach of the trap) of the successive experiments was 84 ± 6 SE hours, on average. This means that clearing ca. 0.4 ha of subtidal area would be necessary to produce ca. 1.0 g of pure dye pigment. While the method is discussed here with respect to a particular historical context, it is generalizable to making population abundance estimates for other species such as whelks, in modern fisheries.

An inference procedure for behavioural studies combining numerical simulations, statistics and experimental results

The technical difficulties of performing underwater observation mean that marine ecologists have long relied on behavioural experiments to study reactions of marine organisms. In this article, we examine the underlying complexity of assumptions made in raceway experiments and we propose a statistical inference procedure tailored to this type of experimental protocol. As an example, experiments were performed to test if light of two different intensities affects the proximal behaviour (i.e. direct, local and immediate) of two species of crustaceans, the hermit crab (Pagurus bernhardus), and the green crab (Carcinus maenas). Individuals were collected in the vicinity of the Sven Loven Marine Center in Tjarno (Sweden). Their movements in raceways were recorded and the statistical distance between the resulting experimental distribution and a simulated null distribution was used to compare their behaviour in two situations: dim (when they were expected to feed) and bright light (when they were expected to shelter). Initial tests indicated no differences of behaviour between dim and bright light for the two species. However, when compared with the reference state (here, a null distribution) the behaviour in dim light deviates significantly from the null distribution suggesting non-random behaviour. Our results suggest that efforts should be made to understand the behaviours of the individuals of these two species to establish a comprehensive reference state as a basis for comparison. This fundamental information should be a prerequisite before implementing experiments testing how potential disturbances affect individual organisms in behavioural ecology.

A new species of Gastrosaccus (Crustacea, Mysidacea) from Algoa Bay (South Africa)

Gastrosaccus wittmanni sp. nov. was collected from surface-waters near Kings Beach in Algoa Bay (South Africa). Morphologically, it is characterised by having seven strong spines on each side of the telson. In between the strong spines, spinules are present except between the first most proximal pair. The endopod of the first female pleopod bears one terminal plumose seta. Most of the setae on antennules, antennae, thoracopods, pleopods and uropods are jointed.