Medes Islands Research Articles

A small-scale fishery near a rocky littoral marine reserve in the northwestern Mediterranean (Medes Islands) after two decades of fishing prohibition

Fishing in the Medes Islands Marine Reserve (511 ha, including a no-take zone and a buffer area) was prohibited in 1983. This study is the result of a 2.5-year monitoring program (sampling on board fishing boats from June 2003 to December 2005) aimed at characterizing the small-scale fishing carried out near the reserve. A total of 109 species were identified. The various metiers in use with the fishing gears trammel net, longline and gillnet were identified on the basis of the landing profiles. The main fishing target species included striped red mullet (Mullus surmuletus), common sole (Solea solea), gilthead seabream (Sparus aurata), common cuttlefish (Sepia officinalis), common pandora (Pagellus erythrinus), seabass (Dicentrarchus labrax), spiny lobster (Palinurus elephas) and hake (Merluccius merluccius). Most of the catches consisted of mature individuals and discards were very low or nil. The exception was Palinurus elephas, with catches made up mostly of juveniles. The estimated stock parameters for Mullus surmuletus, Pagellus erythrinus, Sparus aurata and Scorpaena porcus (Lc mean catch length; Lopt length at maximum yield per recruit; Y/Rc; Y/Rmax; Y/R at F(0.1), Y/R(0.1)) and the distributions of the exploited sizes, with presence of very large individuals, suggest a situation of low fishing pressure.

Patterns of variation in recruitment and post-recruitment processes of the Mediterranean precious gorgonian coral Corallium rubrum

This research seeks to quantify recruitment, early survival and early colony growth in different populations of the precious Mediterranean red coral. Although basic to our understanding of red coral ecology and population dynamics, these early life-history descriptors are still poorly understood. To fill this lack of knowledge, marble settlement tiles were placed at 35±1m depth within 3 populations of Corallium rubrum dwelling in the coralligenous habitat of different geographic areas of the north-western Mediterranean: Calafuria and Elba Island (Italy), and Medes Islands MPA (Spain), following a multifactorial ANOVA model and sampled photographically for four years (2003–2006). Overall, 517 red coral recruits settled on the tiles during the experiment, 189 of which (126 at Calafuria and 63 at Elba) were still surviving, in 2007, when the tiles were removed. The recruitment density at Medes was only one tenth of that at Calafuria and Elba (0.56±0.21 vs. 6.06±1.75 and 4.66±1.01recruitsdm−2, mean±SE). No colony survived after four years at Medes, where the lowest recruitment rate was also found. As the age of each new settled colony was known, it was possible to measure the early growth rates of individual colonies. The growth rates thus obtained were two to three times higher than that measured in older colonies and differed significantly between the geographic areas (the growth of colony basal diameter was 0.68±0.02 and 0.59±0.19mm/year at Calafuria and Elba), while no significant difference was found between the actual colony growth and that previously measured in the former area. A test for secondary substrate selectivity, carried out in one area, showed that red coral preferentially settles on tubes of Serpulida than on other encrusting organisms. However, since recruitment density at Medes was lower despite the four-fold higher cover of Serpulida found there, other factors, intrinsic to the populations, such as different size–age structures or densities, leading to different larval output, may likely have determined red coral recruitment rates in the studied areas.

Assessing the Effectiveness of Marine Reserves on Unsustainably Harvested Long‐Lived Sessile Invertebrates

Although the rapid recovery of fishes after establishment of a marine reserve is well known, much less is known about the response of long-lived, sessile, benthic organisms to establishment of such reserves. Since antiquity, Mediterranean red coral (Corallium rubrum) has been harvested intensively for use in jewelry, and its distribution is currently smaller than its historical size throughout the Mediterranean Sea. To assess whether establishment of marine reserves is associated with a change in the size and number of red coral colonies that historically were not harvested sustainably, we analyzed temporal changes in mean colony diameter and density from 1992 to 2005 within red coral populations at different study sites in the Medes Islands Marine Reserve (established in 1992) and in adjacent unprotected areas. Moreover, we compared colony size in the Medes Islands Marine Reserve, where recreational diving is allowed and poaching has been observed after reserve establishment, with colony size in three other marine protected areas (Banyuls, Carry-le-Rouet, and Scandola) with the enforced prohibition of fishing and diving. At the end of the study, the size of red coral colonies at all sampling sites in the Medes Islands was significantly smaller than predicted by growth models and smaller than those in marine protected areas without fishing and diving. The annual number of recreational dives and the percent change in the basal diameter of red coral colonies were negatively correlated, which suggests that abrasion by divers may increase the mortality rates of the largest red coral colonies within this reserve . Our study is the first quantitative assessment of a poaching event, which was detected during our monitoring in 2002, inside the marine reserve. Poaching was associated with a loss of approximately 60% of the biomass of red coral colonies.

Spatial and temporal variability of deep-water algal assemblages in the Northwestern Mediterranean: The effects of an exceptional storm

There are deep-water populations of the endemic and threatened Mediterranean brown alga Cystoseira zosteroides in the Medes Islands Marine Reserve (NW Mediterranean). Here, the distribution, population structure, individual growth, mortality and recruitment rates of this species over two years are described in relation to the effects of an exceptional storm. We found a high spatial variability in the structure and dynamics of C. zosteroides populations at small geographical scales, suggesting that environmental factors acting at the population level display a key role in population size structure, mortality and recruitment. The elevated mortality rates recorded at some locations (almost 80%) is amongst the highest recorded for perennial algae as a consequence of a single storm, emphasizing the importance of episodic catastrophic events in the maintenance of these deep-water, slow-growing populations. These findings are of particular importance not only to fully understand the ecology of C. zosteroides, but also for its conservation.

The influence of environmental characteristics on fish larvae spatial patterns related to a marine protected area: The Medes islands (NW Mediterranean)

We assessed the linkages between environmental variables and the spatio-temporal distribution patterns of larval abundance of coastal fish assemblages within and outside the Medes Islands marine protected area (MPA; NW Mediterranean) to explore possible fisheries effects such as larvae export of the latter. We analyzed small-scale fish larvae distribution of 28 representative taxa from the rocky fish assemblage and combined the former in different groups with the help of cluster analysis. Further we assessed the influence of selected abiotic variables on group and species distributions using Generalized Additive Models (GAM’s). We found a high level of variability in the response of larvae groups and species to environmental variables over the two studied periods (spring and summer); depth and habitat of the adults being the most important factors. In addition, distance to the MPA was found as an important variable in defining the location of larvae of strictly coastal species. Our results provided evidence of larval export of three commercial species affected by the MPA ( Epinephelus marginatus, Pagellus erythrinus and Scorpaena porcus). Thus our study contributes to the few empirical assessments of larvae export from MPAs and adds to the understanding of the functioning of MPAs as fisheries management tools. Nevertheless, in the future integrated assessments of fisheries effects of MPAs are required that measure the effect of larvae and biomass export on increased fishing yield while taking into account fishing effort dynamics.

Small-scale distribution of fish larvae around the Medes Islands marine protected area (NW Mediterranean)

During the spring and summer of 2003, the small-scale spatial distribution of fish larvae was analysed in and around the Medes Islands marine protected area (MPA). High specific richness was found during both seasons, which is when most coastal fish species spawn in the NW Mediterranean. Despite the small dimensions of the area, well-defined larval fish patterns were found. Larvae from pelagic eggs were located farther from the adult habitat than those from demersal eggs; however, there were exceptions, which highlight the influence of larval behaviour and pelagic larval duration. Inside the reserve, there was both a high diversity index and a high abundance of shorefish larvae in relation to the high abundance of adults and a possible retention of larvae in the MPA. Although there was a great variability both in species composition and abundance between periods, the sampling station assemblages were similar. Factors such as habitat and spawning location of adults, and the role of the MPA seem to determine the stability of the larval distribution patterns in time. The importance of small-scale approaches is highlighted to understand the fish larval spatial distributions.

Bioeconomic model for a three-zone Marine Protected Area: a case study of Medes Islands (northwest Mediterranean)

Abstract Merino, G., Maynou, F., and Boncoeur, J. 2009. Bioeconomic model for a three-zone Marine Protected Area: a case study of Medes Islands (northwest Mediterranean). – ICES Journal of Marine Science, 66: 147–154. The bioeconomic effects of establishing a three-zone Marine Protected Area (MPA) are investigated. The division of the area into zones, fully protected, partially protected, and a fishing zone, permits a combination of extractive (fishing) and touristic activities. The consequences for species conservation, commercial fishing, and touristic activities are analysed for a set of different area-size distributions and fishing-effort levels. The model parameters are based on Medes Islands MPA in the northwestern Mediterranean. For the case study, the economic analysis includes revenues from scuba diving, glass-bottom boat trips, and commercial fisheries. Our results help to illustrate the benefits of the coexistence of extractive and non-extractive activities in a realistic, three-level MPA.

Patterns of species and functional diversity around a coastal marine reserve: a fisheries perspective

Abstract Marine protected areas (MPAs) are expected to function simultaneously as biological conservation and fisheries management tools, but empirical evidence linking biodiversity conservation with fisheries benefits is scarce. Around the Medes Islands marine reserve (Spain, NW Mediterranean) patterns of fish catch diversity, catch (CPUE) and income (IPUE) were assessed and the economic value of diversity for local fisheries was explored by combining a Geographic Information System (GIS) analysis with geostatistics. Catch data were derived from the trammel net fleet operating around the MPA to gain information on species diversity, functional diversity, functional redundancy, CPUE and IPUE. Results revealed significant impact of both the fishing prohibition in the MPA and the presence of seagrass beds on diversity metrics, catch and income. Clear differences in functional redundancy in fish assemblages were found within the study area, indicating greater resilience of the fish assemblage against fishing pressure or human impact close to the MPA (⩽2 km). In contrast, fish assemblages beyond 2 km of the MPA border are more vulnerable to disturbance. High values of diversity, CPUE and IPUE overlapped close to the MPA border and close to seagrass beds. The spatial approach developed suggests that, in addition to the more commonly studied effect of density‐dependent spillover of adult fish, increased levels of ecological diversity and economic diversity can also result in fisheries benefits of an MPA. Hence, the fishing regulations in and around the Medes Islands marine reserve have shown that biological conservation and fisheries benefits can be complementary in the long‐term, which should be considered in future policies for MPAs or MPA networks. Copyright © 2008 John Wiley & Sons, Ltd.

Diet of Yellow-legged Gull (Larus michahellis) chicks along the Spanish Western Mediterranean coast: the relevance of refuse dumps

In recent decades, the Yellow-legged Gull (Larus michahellis) has become a problematic species in many Mediterranean countries, mainly because it interferes with human interests. However, this gull also has a negative impact on several other bird species, many of which are classified as endangered. Two different European Union Action Plans are currently under development with the aim of decreasing the availability of food derived from human activities, such as garbage and fishery discards, which are considered to be the main causes of the superpopulations of this gull. Here, we describe the diet of Yellow-legged Gull chicks, with particular emphasis on establishing the dependence of each population on refuse dumps, in order to forecast changes in gull population dynamics in response to the management decisions being implemented. We sampled four colonies along the Western Mediterranean in Spain: the Medes Islands, the Ebro Delta, the Columbretes Islands, and Mazarron Island. To elucidate their feeding ecology and to avoid obtaining a discrete estimation from a single sampling, we collected regurgitates from each colony three times throughout the chick-rearing period. Slightly differential feeding habits were observed between chick age classes. Younger chicks in all four colonies tended to be consistently provisioned with smaller prey such as invertebrates. Distinct uses of several foraging habitats among localities were observed. In particular, the use of refuse dumps was common and abundant in two of the colonies: the Medes and Mazarron Islands. As a consequence of current management strategies, generalized reductions in Yellow-legged Gull populations and increases in the consumption of alternative food resources to those of fishery discards and refuse scraps are expected. Finally, we predict that decreased food availability will force some gulleries to increase predation on endangered species, thereby raising a conservation concern.

Physiological responses of the seagrass Posidonia oceanica to elevated organic matter content in sediments: An experimental assessment

Here we studied the effects of adding organic carbon and nutrients to sediment on the physiology and survival of the seagrass Posidonia oceanica in a field experiment in the Medes Islands (NE Spain). Nine randomly selected plots were established at a depth of 10 m; three were enriched with organic carbon (OM treatment), three with organic carbon and nutrients (OMN treatment), and three were kept as controls (CON). The experiment was performed over 5 months and sampling of plants and sediments was done in March, May and July 2002. Sediment sulfide pools and pore water ammonium concentrations increased significantly in OM and OMN plots, both treatments showing increased reducing conditions in the sediment. Plants in these two treatments showed higher mortality and lower biomass compared to plants from CON plots. The greatest effects on seagrass occurred in the OMN plots, indicating a synergistic effect of organic carbon and nutrient additions. Treatments had significant effects on plant nitrogen (N) and phosphorous (P) metabolism, shown by an increase in free amino acid (FAA) content, a change in FAA composition and a lack of increase in N and P tissue content. Treated plants showed higher g-aminobutyric acid (GABA) and malate concentrations and lower concentrations of non-structural carbohydrates compared to CON, indicating that anaerobic respiration in below-ground tissues occurred. Several of the physiological changes shown by P. oceanica can be interpreted as adaptations to anoxia exposure. However, the increased mortality in treated plots demonstrates that this seagrass does not tolerate highly reduced sediments.

Spatial variability in reproductive cycle of the gorgonians Paramuricea clavata and Eunicella singularis (Anthozoa, Octocorallia) in the Western Mediterranean Sea

Paramuricea clavata (Risso, 1826) and Eunicella singularis (Esper, 1794) are the most representative gorgonian species in hard bottoms sublittoral communities in the Western Mediterranean Sea. Reproductive cycles of two populations of both species were studied in two distinct locations approximately 600 km apart (Medes Islands and Cape of Palos), in order to assess interpopulation variability on a relevant geographic scale. Seasonal variation of lipid concentration levels in the gorgonian tissue was used as a tool to quantify energy storage by each studied population in order to explain possible interpopulation differences in gonadal output. Sex ratio in Medes Islands populations of both species was 1:1, while in Cape of Palos sex ratio was significantly male biased (1:7) in P. clavata, and female biased (1.7:1) in E. singularis populations. Spawning timing occurred in all cases coinciding with a marked increase in sea-water temperature in spring, and after the most successful feeding season, but comparing localities there was a clear temporal shift in the time of gametes release, appearing well linked to the shift in sea-water temperature rising in spring in both sites at the depth where populations are placed. Therefore, in this study the temperature appears as the main synchronizing factor of gonadal development within these populations. Significant differences in gonadal volume per polyp were found in both species owing mainly to differences in the number of gonads per polyp between populations, with Cape of Palos populations displaying higher values in both studied species, suggesting that the exposition to different local conditions may be reverted in a different gonadal output. But the observed patterns in lipid concentrations levels in gorgonians disable us to conclude that lipid concentration levels explain the observed differences in gonadal output found in this study.

Temporal patterns of spawning of the dusky grouper Epinephelus marginatus in relation to environmental factors

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 325:187-194 (2006) - doi:10.3354/meps325187 Temporal patterns of spawning of the dusky grouper Epinephelus marginatus in relation to environmental factors Bernat Hereu1,*, David Diaz1, Josep Pasqual2, Mikel Zabala1, Enric Sala3 1Departament d’Ecologia, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain 2C./ Santa Anna s/n, L’Estartit, 17288 Girona, Spain 3Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, La Jolla, California 92093-0202, USA *Email: hereu@ub.edu ABSTRACT: The dusky grouper Epinephelus marginatus pair spawns in summer in the NW Mediterranean. Only a few spawning sites have been identified, mostly in marine reserves. Because the dusky grouper is vulnerable to fishing, there is a need to identify and predict the occurrence of spawning for conservation purposes. To gain insight into the temporal patterns of dusky grouper spawning, we monitored a reproductive population in the Medes Islands Marine Reserve, Catalonia, from 1996 to 1999. We observed 44 successful spawning events. At a monthly scale, the highest reproductive activity occurred in August, when surface temperatures were at a maximum (monthly average of 24 to 25°C), and during days with 14 daylight hours, 2 mo after the summer solstice (21 to 22 June). At a daily scale, the greatest number of spawns occurred when the surface temperature was highest (25 to 26°C) and the temperature at 20 m was 17 to 19°C, during anticyclonic conditions, and when tidal amplitude and wave height were largest. Spawning occurred during all moon phases, although it was more frequent during the new moon and the first quarter. Reproductive males did not show sustained spawning activity during consecutive days and had an average spawning rate of 1.5 spawns d–1. All spawning occurred at dusk, between 1 h before and 30 min after sunset. There was no population-wide synchronicity of spawning, since we never observed all monitored males spawning within the same day. These results should allow researchers to predict the temporal occurrence of dusky grouper spawning elsewhere in the Mediterranean. KEY WORDS: Epinephelus marginatus · Spawning · Reproductive patterns · Environmental factors · Marine reserves Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 325. Online publication date: November 07, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Spatial and temporal variation of natural toxicity in cnidarians, bryozoans and tunicates in Mediterranean caves

The natural toxicity of cnidarians, bryozoans and tunicates in two caves was assessed using the Microtox® technique in spring and autumn. One cave was located in the Cabrera Archipelago (Balearic Islands) and the other in the Medes Islands (Catalan littoral). The organisms analysed were good representatives of the coverage of each Phylum in the communities; however, these Phyla are less abundant than sponges which are the dominant group in these caves. Seventy-one percent of the species of cnidarians and bryozoans analysed were toxic in one of the caves, communities or seasons, which indicates the relevance of bioactive species in these groups. The tunicate Lissoclinum perforatum was the most toxic species. Although all three Phyla had some highly toxic species, a common pattern that related the caves, communities and seasons was not found. Seasonal variation of toxicity in cnidarians and bryozoans was higher in the Cabrera than in the Medes cave. Moreover, variation in toxicity either between communities or between seasons was a common trait for most cnidarians and bryozoans, whereas tunicates remained toxic throughout communities and seasons.

Increased predation of juvenile European spiny lobster (Palinurus elephas) in a marine protected area

One of the aims of Mediterranean marine protected areas (MPAs) is to increase populations of exploited species, such as the European spiny lobster (Palinurus elephas), which is considered a key species for its commercial and ecological value. Monitoring of temporal patterns in abundance of early benthic stages of P. elephas indicated that predation may be higher inside the Medes Islands MPA relative to adjacent control sites. Tethering experiments were performed to test whether predation rates actually differed within and outside the MPA. Relative mortality of recently‐settled juveniles inside the MPA was much higher than in control sites in adjacent non‐protected areas. Treatments with and without shelter indicated that predation on recently‐settled juvenile spiny lobsters was moderated by the availability of suitable shelter. The decline or absence of fish predators in the fished area may be the reason why juvenile lobsters outside the MPA experience lower predation than within the MPA.

The effects of predator abundance and habitat structural complexity on survival of juvenile sea urchins

We studied the effect of the abundance of predatory fishes and structural complexity of algal assemblages on the survival of juveniles of the sea urchin Paracentrotus lividus on Mediterranean infralittoral rocky bottoms. Post-settlement juveniles (2–10 mm) were placed on four distinct natural substrates with increasing structural complexity (coralline barren, algal turf, erect fleshy algal assemblages and small crevices) inside and outside the Medes Islands Marine Reserve. Predation on these sea urchins increased at greater abundance of predatory fishes, and decreased with greater structural complexity. The refuge provided by structural complexity, however, decreased with increasing size of sea urchin recruits. Predation on the smallest post-settlers was carried out almost exclusively by small fishes (<20 cm), mainly the labrid Coris julis, while the dominant predator of larger juveniles was the sparid Diplodus sargus. Our results demonstrate the cascading effects caused by the prohibition of fishing in marine reserves, and highlight the potential role of small predatory fishes in the control of sea urchin populations.

The Past and Present Topology and Structure of Mediterranean Subtidal Rocky-shore Food Webs

The understanding of the taxonomic composition of Mediterranean subtidal rocky-shore food webs is extraordinary; the information on trophic links and food-web structure is, however, still meager. An initial description of the rocky-bottom food web of the Medes Islands off the Catalan coast includes a minimum of 1350 species organized in five trophic levels. A minimum of 151 trophic links have been identified for 37 broad trophic/taxonomic categories (including humans), although estimates of the total number of links at the species level may be on the order of thousands for fishes alone. Mediterranean food webs are dynamic, their topology and structure varying along seasonal and environmental gradients. Fishing has been for thousands of years the single major factor provoking changes in the structure of these Mediterranean food webs. Ecologically extinct megafauna (monk seal, loggerhead turtle, sharks) accounted for 24% of the identified trophic interactions. The removal of these large consumers had undescribed ecological consequences. Improved understanding of present and past Mediterranean food webs will improve understanding of the effects of human activities and help us preserve and restore these food webs.

Temporal and spatial variability in settlement of the sea urchin Paracentrotus lividus in the NW Mediterranean

Settlement into the benthic habitat may be an important process in regulating sea urchin abundance, which potentially modifies the structure of benthic communities. Strong settlement events may increase sea urchin abundance beyond a certain threshold, leading to the formation of coralline barrens (overgrazed communities with a dominance of encrusting coralline algae). To understand the role of settlement in regulating sea urchin populations we first need to determine settlement variability. Temporal variation in settlement of the sea urchin Paracentrotus lividus was monitored at three sites in the Medes Islands, NW Mediterranean, during three settlement seasons (March 1998 through October 2000). Spatial variation in settlement was studied in 1999 at 50 sites along a gradient of exposures to waves and currents, inside and outside the archipelago, and separated by distances from tens to thousands of meters. Bathymetric distribution of settlement was also studied in 2000 at six sites at 5, 10, 15 and 20 m depths. Settlement of P. lividus occurred in a single annual peak within 3 weeks in May–June. Differences in settlement between years were more than two orders of magnitude. Spatial variability was found at all scales investigated, showing strong patchiness at the smallest spatial scales (tens of meters). Sea urchins settled preferentially at depths between 5 and 10 m. Substratum type, level of protection, and adult population densities were not significant in determining settlement. However, settlement was found to be related to the degree of exposure to waves and currents, indicating that physical processes are very important at the spatial scales investigated. This greatly variable settlement is a necessary, although not sufficient, condition to create gradients of adult P. lividus abundance. Further studies should be designed to investigate the interaction between settlement strength and post-settlement mortality.

Larval fish communities in the Medes Islands Marine Reserve (North-west Mediterranean)

This study describes the spatio-temporal distribution patterns of fish larvae in a nearshore temperate area off the north-west Mediterranean, located in the vicinity of the Medes Islands Marine Reserve. Our findings suggest that both the abundance and species richness of the larvae of shorefish species (i.e. resident species) is high in the Medes Islands but also in the adjacent unprotected coastal area. In addition to the large inshore species component observed in the Medes Islands the results were also indicative of a significant influx of shelf and oceanic species, and hence it can be concluded that the effect of protection is not the only factor responsible for the spatial patterns observed. The larvae of certain shorefish species, e.g. Coris julis, Boops boops, Serranus hepatus, Blenniidae and Gobiidae undergo significant dispersal out towards the open sea, while other species, e.g. Tripterygion tripteronotus and Gobiesocidae were able to maintain distributions that remain in the vicinity of the adults, confirming that pelagic larvae are not necessarily at the mercy of passive dispersal.

Biochemical characteristics of settling particulate organic matter at two north-western Mediterranean sites: a seasonal comparison

Gross sedimentation rates (GSR) and the main biochemical characteristics of settling particulate matter were monitored at two NW Mediterranean sites (the Bay of Banyuls-sur-Mer, France, and the Medes Islands, Spain) throughout a year to assess possible differences in particulate organic matter (POM) availability to the benthic community. A similar seasonal pattern was observed at both sites with higher organic contents and lower GSR during the spring–summer than during the autumn–winter period. At both sites, there was a negative correlation between GSR and sediment trap organic contents, which is indicative of the importance of resuspension in driving GSR. Along the same line, GSR in Medes correlated positively with wave height. The principal component analysis based on GSR and biochemical characteristics of sediment trap material always segregated samples from the two studied sites mostly due to the occurrence of higher lipid and lower carbohydrate contents in Medes. These differences were indicative of the presence of more labile settling POM in the Medes Islands. They were more pronounced during the spring–summer than during the autumn–winter period. Such a pattern may reflect differences in the sensitivity of the two studied sites to resuspension. According to this interpretation, between-sites differences would be high when resuspension is low (i.e. during the spring–summer period when resuspension would mainly affect Banyuls) and become low when resuspension is high (autumn–winter period when resuspension would affect both sites).

Characteristics of divers at a Spanish resort

This article studies scuba diving around the Medes Islands, situated opposite the tourist resort of L’Estartit, on the Catalan Mediterranean coast. Information on the profile of divers and an assessment of their stay in L’Estartit was obtained by a survey. The results show that scuba divers who visit the Medes Islands are, on average, middle-aged, male Europeans of medium or high socio-economic level, who return to L’Estartit attracted by the rich marine life of the area. The survey also shows high levels of satisfaction associated with their stay.