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Abstracts of selected recent publications

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Feeding habits of the small-spotted catshark Scyliorhinus canicula (L., 1758) in the Central Mediterranean

Abstract

Scyliorhinus canicula collected from 45 stations during the MEDITS annual bottom trawl survey had a Total Length range of 14-52 cm; males were more abundant than females. Of 532 stomachs sampled, 74.4% had identifiable prey material that indicated opportunistic feeding on a wide range of macrobenthic fauna. Teleosts and crustaceans were the most important prey groups (58.7 %/w and 19.3 %/w respectively). Cannibalism was also observed. There were significant differences in diet composition between the sexes and between different size classes for males and females combined.

Gravino F., Dimech M. & Schembri P.J. (2010). Feeding habits of the small-spotted catshark Scyliorhinus canicula (L., 1758) in the Central Mediterranean. Rapport du Congrès de la Commission Internationale pour l'Exploration Scientifique de la Mer Méditerranée 39: 538. 

The full paper may be downloaded from here

Catshark_Scyliorhinus_canicula 

Small-spotted Catshark Scyliorhinus canicula 

 

Deep-water Corallium rubrum (L., 1758) from the Mediterranean Sea: preliminary genetic characterisation

The precious red coral Corallium rubrum (L., 1758) lives in the Mediterranean Sea and adjacent Eastern Atlantic Ocean on subtidal hard substrates. Corallium rubrum is a long-lived gorgonian coral that has been commercially harvested since ancient times for its red axial calcitic skeleton and which, at present, is thought to be in decline because of overexploitation. The depth distribution of C. rubrum is known to range from c. 15 to 300 m. Recently, live red coral colonies have been observed in the Strait of Sicily at depths of c. 600–800 m. This record sheds new light on the ecology, biology, biogeography and dispersal mechanism of this species and calls for an evaluation of the genetic divergence occurring among highly fragmented populations. A genetic characterization of the deep-sea red coral colonies has been done to investigate biological processes affecting dispersal and population resilience, as well as to define the level of isolation/differentiation between shallow- and deep-water populations of the Mediterranean Sea. Deep-water C. rubrum colonies were collected at two sites (south of Malta and off Linosa Island) during the cruise MARCOS of the R/V Urania. Collected colonies were genotyped using a set of molecular markers differing in their level of polymorphism. Microsatellites have been confirmed to be useful markers for individual genotyping of C. rubrum colonies. ITS-1 and mtMSH sequences of deep-water red coral colonies were found to be different from those found in shallow water colonies, suggesting the possible occurrence of genetic isolation among shallow- and deep-water populations. These findings suggest that genetic diversity of red coral over its actual range of depth distribution is shaped by complex interactions among geological, historical, biological and ecological processes.

Costantini, F.; Taviani, M.; Remia, A.; Pintus, E.; Schembri, P.J. & Abbiati, M. (2009). Deep-water Corallium rubrum (L., 1758) from the Mediterranean Sea: preliminary genetic characterisation. Marine Ecology 31: 261-269.

Corallium_rubrum

Deep-water red coral Corallium rubrum from the 'Hanging Gardens of Linosa' at a depth of 673m (ROV image courtesy of QUEST-ROV MARM, Universitat Bremen ©)    

Fishers' perception of a 35-year old Exclusive Fisheries Zone

Fishers’ attitudes and perceptions are critical for the success of fisheries protection areas with their associated biota, and a failure to understand fishers’ behaviour may undermine the success of such fisheries management measures. In this study, we examine fishers’ perception of a long-established exclusive fisheries zone around Malta and to investigate if the perceptions depend on fishers’ demographic, economic, social characteristics and fishing activity of the fishers. A questionnaire survey was undertaken to evaluate the demographic characteristics, economic situation (costs and revenue) and fishers’ activity and behaviour, together with their perception of the Fisheries Management Zone (FMZ). A total of 241 interview responses were analysed which was a response rate of 60%. The perception of most fishers was that the establishment of the FMZ has had an overall negative impact on their fishing activity and that the zone is not important for the protection of local fish stocks. When asked about the beneficial effect of the zone for fishers, most fishers from all backgrounds said that the zone does not benefit commercial fishers, but benefits mainly recreational fishers. The most evident differences in the perceptions and attitudes were between the full-time, part-time and recreational fishers. Fishers that have been fishing for more than 35 years and fishers from the main fishing village also had different attitudes from other fishers towards the FMZ. The results of this study suggest that the proportion of individual income derived from fishing was the strongest factor that influenced attitudinal differences, with home port and fishing experience having less important effects. The main differences in attitude among fishers were related to the protection and conservation effects of the zone, enhancement of resources and conflicts among user groups. The heterogeneity among fishers’ attitudes revealed by the present study has important implications for the implementation of spatial closures. Some sectors of stakeholders may require additional incentives to accept restrictions on access if spatial management is to achieve its intended objectives.

Dimech, M., Darmanin, M., Smith, I.P., Kaiser, M.J. & Schembri, P.J. (2009) Fishers' perception of a 35-year old Exclusive Fisheries Zone. Biological Conservation, 142 (11): 2691-2702.

 

Differences in demersal community structure and body-size spectra within and outside the Maltese Fishery Management Zone (FMZ)

We examined the protection effect of a long-established fisheries protection zone by studying the demersal communities and the biomass size spectra of specific taxonomic groups. The results and the relevant management implications of the community analysis are discussed within the context of the MEDITS trawl survey program, from which the data was derived. The demersal fishery resources on the muddy bottoms of Maltese trawling grounds were found to be stratified in four main depth ranges: 83 to 166 m (outer continental shelf), 140 to 230 m (shelf break), 270 to 440 m (shallow slope), and 466 to 701 m (deep slope). Significant differences were detected between the inside and outside zones of the outer continental shelf. Stations from this stratum inside the protected zone had twice as much biomass as those outside as well as larger individuals of some species (e.g. elasmobranchs). The depth strata identified do not coincide with those sampled in existing trawl survey programmes in the Sicilian Channel, which were set up without reference to demersal assemblage structure and its relation to depth. It is therefore clear that characterisation of the biotic assemblages is important in order to obtain a better sampling representation of each depth-stratum/assemblage type, and this should be considered in the survey design.

Dimech M., Camilleri M., Hiddink J.G., Kaiser M.J., Ragonese S., Schembri P.J. (2008). Differences in demersal community structure and body-size spectra within and outside the Maltese Fishery Management Zone (FMZ). Scientia Marina, 72 (4): 669-682.

The full paper may be downloaded from here  

Medits_Haul

Typical catch from a Medits trawl (photo © Mark Dimech)


Role of environmental variables in structuring demersal assemblages on trawled bottoms on the Maltese continental shelf

Demersal assemblages from trawl surveys made at depths of 45-800 m in trawled areas within the 25NM Fisheries Management Zone round the Maltese Islands were related to environmental characteristics on the seabed. Depth, temperature, and mean grain size all affected the structure of the demersal assemblages but depth and temperature gradient were overall the most important in that order; while mean grain size seemed more important for relatively shallow bottoms (<80 m) than for deep ones.

Dimech M., Camilleri M., Kaiser M.J. & Schembri P.J. (2007). Role of environmental variables in structuring demersal assemblages on trawled bottoms on the Maltese continental shelf. Rapport du Congrès de la Commission Internationale pour l'Exploration Scientifique de la Mer Méditerranée 38: 463.

The full paper may be downloaded from here

 

Demersal assemblages on deep water trawling grounds off the Maltese islands: Management implications

Data from three consecutive years of trawl surveys were used to characterise the demersal assemblages present on trawling grounds around the Maltese Islands, (Central Mediterranean) in water ranging from 85 to 800 m depth. Five different assemblages were present which seemed related to depth zones that do not coincide with those sampled in existing stock assessment programmes. It is therefore clear that the depth strata sampled in such programmes need to be revised to make them more biologically relevant and to achieve a better sampling representation of each assemblage type.

Dimech M., Camilleri M., Kaiser M.J. & Schembri P.J. (2007). Demersal assemblages on deep water trawling grounds off the Maltese islands: Management implications. Rapport du Congrès de la Commission Internationale pour l'Exploration Scientifique de la Mer Méditerranée 38: 462.

The full paper may be downloaded from here

 

Litter as a source of habitat islands on deep water muddy bottoms.

Certain types of marine litter, usually considered as pollutants, may also be a resource, serving as artificial reefs on sedimentary bottoms. In order to study this aspect, marine debris was collected by bottom trawl from muddy bottoms (depths of 45-700m) in the waters around the Maltese islands, during July 2005. The associated fauna was identified and quantified. Litter was found to support a higher abundance of organisms than the surrounding sediment, but a lower species richness. However, the suite of epifaunal species on the debris was different from the infauna of the surrounding substratum. Thus litter was found to increase the overall biodiversity of particular areas.

Pace R., Dimech M., Camilleri M., Mosteiro Cabanelas A. & Schembri P.J. (2007). Litter as a source of habitat islands on deep water muddy bottoms. Rapport du Congrès de la Commission Internationale pour l'Exploration Scientifique de la Mer Méditerranée 38: 567.

The full paper may be downloaded from here.

5.7_An_anthozoan_using_a_beer_can_as_a_substratum 

An anthozoan using a beer can as a substratum (photo © Roberta Mifsud)

 

Deep-water corals in Maltese waters

This paper reports the occurrence of living deep-water corals, Lophelia pertusa and Madrepora oculata, from stations 21-42 km off the southern and south-western coast of Malta. Fragments of living colonies of both species, as well as some large pieces of Lophelia frameworks were recovered from depths of 390-617 m together with the solitary coral Desmophyllum dianthus (= cristagalli). The accompanying biota included the barnacle Pachylasma giganteum, the gastropod Coralliophila richardi, the bivalves Asperarca nodulosa and Spondylus gussonii, and the polychaete Eunice norvegicus, all of which are frequently associated with deep-water corals. The occurrence of the Lophelia-adrepora-Desmophyllum triad, the large pieces of coral frameworks consisting predominantly of live, healthy polyps, and the associated biota, suggest that coral patches may be present in at least some of the investigated localities, rather than just fragmented remains or isolated colonies.

Schembri P.J., Dimech M., Camilleri M. & Page R. (2007) Living deep-water Lophelia and Madrepora corals in Maltese waters (Strait of Sicily, Mediterranean Sea). Cahiers de Biologie Marine 48: 77-83. 

Lophelia_pertusa

Deep-water coral Lophelia pertusa trawled frm a depth of c.600m from the South Malta Coral Province (photo © Daniel Schembri)

 

 

 

 

 

 

 

 

 

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