Download An integrated biological-geological approach for the

An integrated biological-geological approach for the management of
renewable marine resources: the COMSOM Project
Claudio Lo Iacono1, Silvia De Juan2, Montse Demestre2
1: Unidad Tecnología Marina (UTM-CSIC), Pg. Maritim Barceloneta 37- 49, 08003 Barcelona, Spain – [email protected]
2: Instituto de Ciencias del Mar (ICM-CSIC), Pg. Maritim Barceloneta 37- 49, 08003 Barcelona, Spain
Fishing with trawling gears is one of the major sources of damage to benthic communities and habitats and there is an urgent need for developing ecosystem indicators as tools for the management of fisheries. To that aim a
comprehensive biological and geo-acoustical dataset is essential to relate biotic and abiotic characteristics of habitats and ultimately assess potential changes in the structure of benthic communities and habitats caused by
fishing activities. Aiming to define new strategies for the management of fishery resources, in the framework of COMSOM Project (CTM2008-04617 and CTM2008-04206-E), we adopted a seascape ecology approach integrating
biological variability and geological heterogeneity in the study of trawling disturbance in the Mediterranean.
Cabo
De
Creus
Cabo
De
Palos
The study areas were surveyed with geo-acoustic methodologies (Sidescan Sonar,
Multibeam) and ROV to characterise the physical attributes and define the distribution of
benthic habitats. A 2m-beam trawl and a Van Veen grab were used to collect benthic fauna
and a CTD to record hydrographical variables.
Thyrrenian
Sea
The benthic habitats, mapped combining biological and geological information (e.g. density of indicator species at
each area, sediment distribution), have been contrasted with the different levels of fishing effort at each site. These
data allowed the identification of different habitats and communities. detected
Area
Fig.2
Ionian
Sea
Greece
Site
Sediment type
Nº of trawl marks
Dominant species
Observations
South
mud
86615
Starfish Astropecten irregularis
Fish Citharus linguatula
Crustacean Goneplax rhomboides
North
mud
102017
Starfish Astropecten irregularis
Crustaceans Alpheus glaber and
Medorippe lanata
High abundance of angler fish
(Lophius spp)
West
mud
Brittle star Ophioderma longicauda
Starfish Astropecten irregularis
Bivalvia Acanthocardia echinata
Brittle star biocenosis (Fig.4)
North
Gravelly muddy-sand
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Bivalve Astarte sulcata
Ascidia Ascidiella scabra
Sea urchin Spharaechinus granulata
Polyquete Hermione sp
Patches of maërl (Fig.5)
South
Sandy mud
137243
Starfish Echinasster sepositus
Hermit crab Dardanus arrossor
Ascidia Pyura dura
The heaviest fished areas
are composed by muddy
sediments with high
abundance of mobile
invertebrates, like brittle
stars, and lack of habitat
forming species.
20 m
Fig.1: Four coastal areas located in the Mediterranean and subjected to
variable trawling intensity have been selected: two areas in the western
Mediterranean (Cabo de Creus and Cabo de Palos, Spain), one area in
the central Mediterranean (northern Tyrrhenian, Italy) and one area in
the eastern Mediterranean (Ionian Sea, Greece). Each area is between 40
and 70 m depth and is characterised by soft-bottoms and by sporadic
rocky outcrops. In the present work preliminary results are shown for
two areas: Cabo de Palos (CP) and Greece (G). These areas contain 2
and 3 sampling sites respectively, with different environmental
characteristics (e.g.: sediments, trawling effort) (Table 1).
Fig.2: MB bathymetry (2m resolution),
sidescan sonar records, epibenthic
dredges and sediment samples collected
in the area of Cabo de Palos (Spain).
Cabo de
Palos
20 m
Fig.3: Trawl marks observed in the sidescan
sonar records which allow estimating the
fishery intensity in the study areas.
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The site with the lowest
trawling intensity (Cabo
de Palos north) presents
maërl beds, high
densities of ascidians and
bivalves.
Patches of Posidonia oceanica and the
algae Codium bursa (Fig.6). Maërl.
Physical-biological interactions
Ordination of samples on the species composition
(Bray-Curtis similarity). The two axes explain 51%
of variance; most variance is explained by the 1st
axis that separates the Greece sites from CP sites.
Greece samples have lower dispersion index than
CP samples; and Greece samples are clustered by
sites, north-west-south, whereas CP samples are
mixed.
Correlations between physical and biological
variables (Spearman correlation) larger than 0.6
are included in the plot: mud and median depth
well correlate with Greece sites. Gravels, sands
and D50 characterize CP sites.
Number of trawl marks, having a weaker
correlation, characterize samples from the fished
areas Greece west and CP south.
5 cm
Fig.4: Epifauna (brittlestars) collected at
the western Greek site.
10 cm
5 cm
Fig.5: Epifauna including starfish, sea urchin and
maerl biocenosis collected at the CP northern site.
Fig.6: Epifauna including starfish and Codium
bursa collected at the CP southern site.
Concluding remarks: Mapping the areas subjected to different trawling intensities will provide a valuable tool to detect
habitat and community degradation, which is essential for the spatial planning of fishing activities. These preliminary results
highlight the importance of the habitat variables in the benthic community structure and, in this context, the obtained results
bring an invaluable opportunity to proof the feasibility of a seascape integrated approach in the study of benthic habitats and
in the management of marine ecosystems exploited by fishing activities.