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Abstract. The fish assemblages of a strictly protected area and of a neighbouring fished area, located off a Mediterranean urbanized coast (Carry-le-Rouet, France), were compared in order to select the most evident, constant, and easily recorded indices of the 'reserve effect'. Visual censusing was repeated simultaneously at both sites eight time a year during 3 years along four permanent transects layed on shallow rocky bottoms (9–14 m). Overall species richness was 16% higher in the reserve, but differences in average instantaneous richness were only marginally significant. The most contrasting results were shown by the occurrence frequency, abundance, and demographic structure of two types of target species. The type A target species group comprises 16 large meso- and macrocarnivores particularly threatened by spearfishing, including the common nectobenthic sparids Diplodus spp. Type B target species are represented by two small territorial fishes particularly impacted by angling: the serranid Serranus cabrilla and the terminal phase males of the labrid Coris julis . The size structure of Diplodus spp., S. cabrilla , and C.julis subpopulations strongly argues for the role of protected areas as a reservoir of large spawners. Fishing pressure is assumed to modify the social conditions of the C. julis local populations and to induce earlier sex change. 相似文献
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Jean-Georges Harmelin 《Marine Ecology》1990,11(4):351-364
Abstract. Two small sclcractinians, Lepfopsummiu pruvoti (solitary) and Hoplungiu dur-olrix (colonial, aggrcgatcd or not), which arc common pcrcnnial componcnts of Mcditcrrancan submarinc cavcs and dccp vcrtical walls, bcar many cpibionts on thc lowcr part of thcir corallitcs. Samplcs were collectcd ncar Marscillcs (7–58 in) undcr various cnvironmcntal conditions and coral densitics. Frequency of occurrencc of thc major cpizoan groups and of individual bryozoan spccics overgrowing the corallites varies according to habitat charactcristics and to acccssibility of the individual corallitcs for adjaccnt epizoans. Thc most frcqucnt colonizcrs arc: bryozoans (by vcgctative growth and larval settlcrnent), sponges (mainly by vcgctativc growth), and scrpulids. Among the 40 recorded bryozoan species (26 on Leptopsammia, 28 on Hoplangiu), 15 spccics are relatively frequent on each host. Comparisons of data from the corallites with thosc obtained from adjoining samples indicatc the preference for coral substratc of Pucflina radiata. This encrusting bryozoan is highly predominant on both Leptopsammia and Hoplangiu as well as on other scleractinian species. SEM observations show that overgrowth processcs are reversible and that corals may control the invading encruSters by embedding them in their sclerenchyme. The balance and benefits of this epizoan/host system are discussed. 相似文献
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Abstract. A Mediterranean fish assemblage has been visually censused over a period of two years from two permanent, rocky, infralittoral stations (10–15 m) which display a high habitat complexity and are located in a protected area. Six home-range categories were defined for a better understanding of the community structure which was analyzed through qualitative and quantitative data. The respective roles of different sources of variability in species composition and numerical abundance were evaluated. 相似文献
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Nathaniel Bensoussan Jean-Claude Romano Jean-Georges Harmelin Joaquim Garrabou 《Estuarine, Coastal and Shelf Science》2010
In the North West Mediterranean (NWM), mass mortality events (MME) of long-lived benthic species that have occurred over the last two decades have been related to regional warming trend. Gaining robust data sets on thermal regimes is critical to assess conditions to which species have adapted, detect extreme events and critically evaluate biological impacts. High resolution temperature (T) time series obtained during 1999–2006 from 5 to 40 m depth at four contrasted sites of the NWM were analyzed: Area Marina Protegida de les Illes Medes (NE Spain), Riou (Marseilles, France), Parc National de Port-Cros (France), and Réserve Naturelle de Scandola (Corsica, France). The seasonal pattern showed winter T around 11–13 °C, and summer T mainly around 22–24 °C near surface to 18–20 °C at depth. Stratification dynamics showed recurrent downwellings (>40 m) at Medes, frequent observation (1/3rd of the summer) of deep and cold upwelled waters at Riou, while Scandola exhibited stable summer stratification and highest suprathermoclinal T. Port-Cros showed an intermediate regime that oscillated between Riou and Scandola depending on the occurrence of northern winds. Data distribution study permitted to identify and to characterize 3 large scale positive anomalies concomitant with the mass mortality outbreaks of summers 1999, 2003 and 2006. The analysis of biological surveys on gorgonian populations showed significant impacts during the 3 years with temperature anomalies. Besides the degree of impact showed inter-annual differences which could be related to different T conditions concomitant to mortality events, from slight increase in T extreme of only 1–2 °C over short duration, to lengthened more classical summer conditions. Our results therefore support the hypothesis that shallow NWM populations of long-lived benthic species are living near their upper thermal thresholds. Given actual trends and projections in NWM, the repetition of new MMEs in the next decades is extremely likely. In such context, the acquisition of dedicated high resolution T series proves to be crucial for increasing our detection, understanding and forecasting abilities. 相似文献
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