Megafauna of vulnerable marine ecosystems in French mediterranean submarine canyons: Spatial distribution and anthropogenic impacts

Abstract

Vulnerable Marine Ecosystems (VME) in the deep Mediterranean Sea have been identified by the General Fisheries Commission for the Mediterranean as consisting of communities of Scleractinia (Lophelia pertusa and Madrepora oculata), Pennatulacea (Funiculina quadrangularis) and Alcyonacea (Isidella elongata). This paper deals with video data recorded in the heads of French Mediterranean canyons. Quantitative observations were extracted from 101 video films recorded during the MEDSEACAN cruise in 2009 (Aamp/Comex). Qualitative information was extracted from four other cruises (two Marum/Comex cruises in 2009 and 2011 and two Ifremer cruises in 1995 and 2010) to support the previous observations in the Cassidaigne and Lacaze-Duthiers canyons. All the species, fishing impacts and litter recognized in the video films recorded from 180 to 700 m depth were mapped using GIS. The abundances and distributions of benthic fishing resources (marketable fishes, Aristeidae, Octopodidae), Vulnerable Marine Species, trawling scars and litter of 17 canyons were calculated and compared, as was the open slope between the Stoechades and Toulon canyons. Funiculina quadrangularis was rarely observed, being confined for the most part to the Marti canyon and, I. elongata was abundant in three canyons (Bourcart, Marti, Petit-Rhône). These two cnidarians were encountered in relatively low abundances, and it may be that they have been swept away by repeated trawling. The Lacaze-Duthiers and Cassidaigne canyons comprised the highest densities and largest colony sizes of scleractinian cold-water corals, whose distribution was mapped in detail. These colonies were often seen to be entangled in fishing lines. The alcyonacean Callogorgia verticillata was observed to be highly abundant in the Bourcart canyon and less abundant in several other canyons. This alcyonacean was also severely affected by bottom fishing gears and is proposed as a Vulnerable Marine Species. Our studies on anthropogenic impacts show that seafloor disturbance by benthic fishing is mainly attributable to trawling in the Gulf of Lion and to long lines where rocky substrates are present. The bauxite residue (red mud) expelled in the Cassidaigne canyon was seen to prevent fauna from settling at the bottom of the canyon and it covered much of the flanks. Litter was present in all of the canyons and especially in considerable quantities in the Ligurian Sea, where the heads of the canyons are closer to the coast. Three Marine Protected Areas and one fishing area with restricted access have recently been established and should permit the preservation of these deep ecosystems.

Macro- and megafauna recorded in the submarine Bari Canyon (southern Adriatic, Mediterranean Sea) using different tools

“…The association of C. conger, P. bogaraveo, and H. dactylopterus with the cold-water coral M. oculata in the catch also confirms the preferred distribution of these species within the coral habitat, previously documented in the SML CWC province (D'Onghia et al, , 2011(D'Onghia et al, , 2012. Moreover, the most frequent observations of C. conger and H. dactylopterus in the present study using both baited lander and longline could be due to a preferential distribution of these fishes in a complex and heterogeneous habitat (D'Onghia et al, 2014;Fabri et al, 2014).…”

“…Almost all the fish species found generally occur in other Mediterranean canyons (e.g. Stefanescu et al, 1994;Ramirez-Llodra et al, 2010;Company et al, 2012;Farrugio, 2012;Watremez, 2012;Fabri et al, 2014). The association of C. conger, P. bogaraveo, and H. dactylopterus with the cold-water coral M. oculata in the catch also confirms the preferred distribution of these species within the coral habitat, previously documented in the SML CWC province (D'Onghia et al, , 2011(D'Onghia et al, , 2012.…”

“…Most new records regard sponges, for which new information is reported for deep-sea species confirming their importance in the structure of CWC communities. An important contribution to the biodiversity is also presented for bryozoans, fishes, and annelids; many species previously reported from cold-water coral communities of the Mediterranean Sea (Longo et al, 2005;Mastrototaro et al, 2010;D'Onghia et al, 2011;Fabri et al, 2014) had not been recorded in the Bari Canyon.…”

“…Berné et al, 1999;Canals et al, 2004Canals et al, , 2009Puig et al, 2008) as well as to their biodiversity and fishery resources (e.g. Cartes et al, 1994;Stefanescu et al, 1994;Gili et al, 2000;Palanques et al, 2005;Sardà et al, 2009;Farrugio, 2012;Revenga Martinez de Pazos, 2012;Fabri et al, 2014). In the last two decades, the canyons have been investigated as a part of national projects carried out in different countries as well as in the context of European projects designed to gain new insight into the biodiversity, ecosystem structure, and function in the deep sea (e.g.…”

First report of live deep-water cnidarian assemblages from the Malta Escarpment

“…By and large, the most relevant actors of such aphotic communities are cnidarians and sponges associated with poorly sampled hard bottoms at depths exceeding 200 m. This is primarily the case for the so-called white coral communities documented at bathyal depths in the Strait of Sicily, southern Adriatic, Ionian, Ligurian, Marmara, northwestern Mediterranean and Alboran seas (Tursi et al 2004;Taviani et al 2005aTaviani et al , 2005bTaviani et al , 2011aFreiwald et al 2009;Mastrototaro et al 2010;Vertino et al 2010;Gori et al 2013;Angeletti et al 2014;Fabri et al 2014), the sponge-dominated habitats in the Tyrrhenian, Ionian and Adriatic seas (Bo et al 2012;Calcinai et al 2013), and antipatharian-gorgonacean communities in the Tyrrhenian, Ionian and Adriatic seas and in the Strait of Sicily (Costantini et al 2010;Taviani et al 2010;Bo et al 2011;Angeletti et al 2014;Deidun et al 2014). From this ecological perspective, the Malta Escarpment in the central Mediterranean happens to be one of the least explored in European waters.…”