Exploring composition and behaviour of fish fauna by in situ observations in the Bari Canyon (Southern Adriatic Sea, Central Mediterranean)

Abstract

Canyons play a fundamental role in enhancing the abundance and diversity of marine organisms through the transport of organic matter and food resources, the presence of complex physical habitats and the absence of trawl fishing. During four baited lander deployments carried out in the Bari Canyon (Southern Adriatic Sea, Central Mediterranean), at depths of 443–788 m, about 43 h of video records were taken, for a total of 619,200 video frames. A total of 12 benthopelagic fish species (five chondrichthyes and seven osteichthyes) were identified. The blackspot seabream (Pagellus bogaraveo) was the most often observed fish species. The depth of 787 m represents a new depth record for this fish in the Adriatic Sea. Groups of up to 40 individuals of P. bogaraveo were attracted to the bait and were shown in single frames. The individuals were observed both exploring the area and feeding actively on the bait. The European conger (Conger conger) was recorded at each deployment. Clear scavenger behaviour was also observed in this teleost fish and in the shark Etmopterus spinax. The shark species Centrophorus granulosus and Hexanchus griseus, which are considered ‘vulnerable’ on the published IUCN Mediterranean Regional Red List, were also recorded but, although attracted by the bait, they were never seen feeding on it. Other fish species, harvested on fishing grounds, such as Merluccius merluccius, Helicolenus dactylopterus and Polyprion americanus, were also recorded. This study represents the first in situ documentation, at very low impact, of the fish fauna in the Bari Canyon, providing new insights into its small scale distribution and behaviour, the first in situ direct observation of the variable feeding behaviour of P. bogaraveo and its gregarious habits, as well as indicating that this canyon could act as a refuge area for species that are vulnerable to fishing on the open slope.

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).…”

“…Most of these species have been recently recorded in the Bari Canyon by in situ observations with an ROV and a baited lander (Angeletti et al, 2014;D'Onghia et al, 2014) and the vertical distribution of P. bogaraveo and H. dactylopterus in this area has also been updated (D'Onghia et al, 2014). M. poutassou, M. dypterygia, and S. elongata previously recorded from the southern Adriatic Sea (Ungaro et al, 1999) are here reported for the first time from Bari Canyon.…”

“…In addition, the single individuals of all recorded species could often be distinguished by their different sizes and morphological features, such as marks and scars on the skin. This was not the case for the blackspot sea bream Pagellus bogaraveo since individual numbers gradually increased after lander touchdown but with individuals moving in and out of camera view it was impossible to distinguish between the individuals (D'Onghia et al, 2014).…”

“…1: Uniqueness or rarity; 3: Importance for threatened, endangered or declining species and/or habitats; 5: Biological productivity; 7: Naturalness) as well as the VME (Vulnerable Marine Ecosystem) criteria (1: Uniqueness or rarity; 2: functional significance of the habitat; 3: fragility; 4: life-history traits that make recovery difficult; 5: structural complexity) (FAO, 2009) could also be assigned to the Bari Canyon in planning future marine protected areas and management measures in order to preserve its high biodiversity level in relation to the presence of cold-water coral species. Freiwald et al, 2009;Bo et al, 2012;Sanfilippo et al, 2013;Angeletti et al, 2014;D'Onghia et al, 2014; present paper; B: Tursi et al, 2004;Longo et al, 2005;Schönberg & Beuck, 2007;Carlier et al, 2009;Freiwald et al, 2009;D'Onghia et al, 2010D'Onghia et al, , 2011D'Onghia et al, , 2012Mastrototaro et al, 2010Mastrototaro et al, , 2013Mastrototaro et al, , 2014.…”

“…Corals and a variety of sessile benthic organisms contribute to creating complex three-dimensional habitats exposed to high sedimentation rates and attract numerous species of mobile invertebrates (mainly echinoderms) and fish, as recently reported by Angeletti et al (2014). Fish faunal composition and behaviour have also recently been investigated using a baited lander (D'Onghia et al, 2014).…”