Anthropogenic impact in the Santa Maria di Leuca cold-water coral province (Mediterranean Sea): Observations and conservation straits

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Abstract

The Santa Maria di Leuca (SML) cold-water coral (CWC) province is a proposed priority conservation area according to several conservation initiatives in the Mediterranean Sea. Part of it is a Fisheries Restricted Area (FRA). Anthropogenic impacts due to fishing on this FRA were investigated using a towed camera system during 2005. The geographic distribution of fishing effort in the SML CWC province was examined through an observers’ program of longline and trawl fishing activities during 2009 and 2010 and Vessel Monitoring by satellite System (VMS) data from 2008 to 2013. Using the video system, it was possible to observe evidence of impacts in the FRA due to longlines, proved by remains of lines on the bottoms and/or entangled in corals, and those due to trawl nets, proved by trawl door scars on the bottom. The application of Generalized Liner Models indicates that the impacts due to longline were significantly related to a geographic site characterized by carbonate mounds while those from trawl net were significantly related to the soft bottoms, consisting of bioturbated fine-grained sediments. The presence of waste of various types was also observed in the FRA; plastic was the most widespread waste and was significantly related to a macrohabitat characterized by the presence of corals.

The geographic distribution of fishing effort for each type of fishing were rather superimposed in the two years of the observers׳ program and six years of VMS data with a significantly greater fishing effort outside the FRA than inside this area. The trawlers generally fished on the muddy bottoms of the upper and middle slope within the SML CWC province and near and inside the northward limit of the FRA. The longliners fished mainly on the shelf in north and off the FRA. The coral by-catch was only recorded during 2009 in 26% of the trawl hauls. No coral by-catch was recorded from longlining in either year. The catches from longlining mainly consisted of Chelidonichthys lucerna, Merluccius merluccius and Conger conger while those from trawling mostly consisted of Aristeus antennatus, Aristaeomorpha foliacea and M. merluccius. The information collected during the observers׳ program and VMS data indicated greater impact due to trawling than longlining. The conservation and effective management of this vulnerable marine ecosystem remain difficult.

Introduction

Cold-water coral (CWC) communities represent extensive three-dimensional habitats that host a variety of faunal associations and are used for shelter, feeding, spawning and as nursery areas by valuable fish and invertebrates of commercial interest (e.g. Freiwald et al., 2004; Tursi et al., 2004; Roberts et al., 2009; Buhl-Mortensen et al., 2010; D’Onghia et al., 2010; Baillon et al., 2012; Henry et al., 2013). For these reasons these habitats are impacted by commercial fishing (e.g. Rogers, 1999; Roberts et al., 2000; Fosså et al., 2002; Hall-Spencer et al., 2002; Reed, 2002; Grehan et al., 2005; Wheeler et al., 2005; Buhl-Mortensen et al., 2010; Söffker et al., 2011; Fabri et al., 2014), generating a widespread alarming scientific consensus on the need for their protection and conservation. In fact, due to the slow recovery rates of corals, the habitats that they build are highly vulnerable (e.g. Roberts, 2002; Morgan et al., 2005; DeVogelaere et al., 2005; Brock et al., 2009; Hourigan, 2009; Buhl-Mortensen et al., 2010; Orejas et al., 2011a, Orejas et al., 2011b; Lartaud et al., 2014). In this respect, CWC have been included on the lists of Vulnerable Marine Ecosystems (VME) (FAO, 2009) for which conservation constitutes a global priority. Furthermore, since corals may provide Essential Fish Habitat (EFH) for commercial fish and invertebrates (Mortensen et al., 2005, Roberts et al., 2009, Mastrototaro et al., 2010, Baillon et al., 2012, Henry et al., 2013), their protection could combine biodiversity conservation and fisheries management objectives according to the Ecosystem Approach to Fisheries (EAF) (Garcia et al., 2003).

The impact of fishing on deep-sea coral communities has mainly been documented in the Atlantic (e.g. Rogers, 1999; Roberts et al., 2000; Duncan, 2001; Fosså et al., 2002; Hall-Spencer et al., 2002; Reed, 2002; Grehan et al., 2005; Mortensen et al., 2005; Wheeler et al., 2005; Durán Muñoz et al., 2011; Söffker et al., 2011; Sampaio et al., 2012). However, some studies on this issue have also been carried out in the Mediterranean (Orejas et al., 2009, Madurell et al., 2012, Bo et al., 2014a, Bo et al., 2014b, Fabri et al., 2014, Savini et al., 2014). The obvious impact of trawling on coral communities is the mechanical damage caused by otter boards and nets that destroy the three-dimensional structure of coral colonies (Hall-Spencer, 2001, Buhl-Mortensen et al., 2010). Video surveys carried out off West Norway show that deep-water coral reefs are reduced to rubble by towed fishing gear (Hall-Spencer, 2001). Other fishing gears, such as longlines and gillnets, can also cause damage to coral reefs since they cause breakage of the colonies (Lumsden et al., 2007, Orejas et al., 2009, Durán Muñoz et al., 2011, D’Onghia et al., 2012, Sampaio et al., 2012, Bo et al., 2014a). Furthermore, bottom trawl activity alters the hydrodynamic and sedimentary conditions, indirectly affecting corals and the associated benthic fauna (Puig et al., 2012); in fact, coral species, like all suspension feeders, are particularly vulnerable to the effects of increased sedimentation (Rogers, 1999, Purser, 2015 and references therein).

Deep-sea coral communities characterized by the species Madrepora oculata and Lophelia pertusa are also located in the deep waters of the Mediterranean Sea but their distribution is still incompletely known (Freiwald et al., 2009, Orejas et al., 2009, Lo Iacono et al., 2012, Gori et al., 2013, Mytilineou et al., 2014, Angeletti et al., 2014). These coral communities live at temperatures ranging from 12.9 °C to 13.9 °C close to the upper limit for many CWCs living at bathyal depths (Freiwald et al., 2009). Thus, CWCs in the Mediterranean do not flourish as they do in the Atlantic and their occurrence in the Mediterranean appears to be a relic of a much more extensive distribution during the Pleistocene (Pérès, 1985, Taviani et al., 2005, Wienberg et al., 2009). In addition to limiting hydrological conditions, the Mediterranean CWC communities are also subject to various anthropogenic activities, such as fishing and dumping of litter (Orejas et al., 2009, Coll et al., 2010, D’Onghia et al., 2010, Indennidate et al., 2010, Ramirez-Llodra et al., 2011, Madurell et al., 2012, Bo et al., 2014a, Fabri et al., 2014, Savini et al., 2014).

The Santa Maria di Leuca (SML) CWC province represents an example of living Madrepora-Lophelia-bearing coral mounds in the Mediterranean Sea (Tursi et al., 2004, Freiwald et al., 2009, Mastrototaro et al., 2010). Considering the impact of trawling and, to a lesser extent, of other fishing gears on deep-sea coral communities, in January 2006 the General Fisheries Commission for the Mediterranean (GFCM) created the new legal category of “Fisheries Restricted Area” (FRA) (Fig. 1). The FRA covers a part of the SML CWC province. Towed dredges and bottom trawl nets have been prohibited in the FRA. Members are required to call the attention of the appropriate authorities in order to protect this FRA from the impact of any other activity jeopardizing the conservation of the features that characterize the particular habitat (GFCM-RAC/SPA, 2007). Although trawling is formally illegal, unauthorized operations may still take place. In fact, after the establishment of the FRA, Indennidate et al. (2010) recorded trawling activity inside the northward limit of the FRA and Savini et al. (2014) recorded trawling traces in the coral community.

The “deep-sea corals” habitat is reported on the list of priority habitats present in Italy (Relini and Tursi, 2009) according to the SPA/BIO protocol (Barcelona Convention) and the SML CWC province is also included among the selected areas of conservation interest in the open sea, including deep sea (Specially Protected Areas of Mediterranean Importance) (SPAMIs) (UNEP-MAP-RAC/SPA, 2009, UNEP-MAP-RAC/SPA, 2010; de Juan et al., 2012). The criteria of rarity, importance for life history stages of species, importance for threatened and endangered species/habitats, vulnerability, biological diversity and naturalness, make this ecosystem a Sensitive Habitat (SH) (de Juan and Lleonart, 2010). In this respect, the SML CWC province is included in the proposed conservation plan of “Vulnerable habitats” (de Juan and Lleonart, 2010). In addition, this Mediterranean CWC area is also among the proposed priority conservation areas according to several conservation initiatives (e.g. UNEP MAP EBSA; CIESM/Mediterranean Marine Peace Parks; Oceana/MedNet) (Oceana, 2011, Micheli et al., 2013).

The objective of this study is to provide a contribution to the knowledge of the fishing activity in this CWC province and anthropogenic impact in the FRA where mounds covered with corals are mainly distributed in international waters. Three types of data have been used in this work: video records, direct fishery observations and Vessel Monitoring by satellite System (VMS). The first type of data was taken during the APLABES project (Corselli, 2010); the second was collected during the observers׳ program carried out in the context of the CoralFISH EU 7FP project (Indennidate et al., 2010); the third type of data has been provided by the Ministero delle Politiche Agricole Alimentari e Forestali (MIPAAF) – Direzione Generale Pesca, which is the owner and user in the Data Collection Framework for Fisheries Sector (http://ec.europa.eu/fisheries/cfp/fishing_rules/data_collection/index_en.htm). The second and third type of data were used in order to provide exact locations of the commercial fishing operations and allow the assessment of whether fishing gears are deployed on coral mounds and sensitive beds or on neighboring sedimentary bottoms outside the FRA. All the relevant results are presented in relation to the present knowledge of the SML CWC province and the relevant conservation perspectives for this rare and fragile ecosystem.

Section snippets

Study area, biodiversity and fishery resources

The SML CWC province, located along the Apulian margin, a few miles off Cape Santa Maria di Leuca in the Northern Ionian Sea (Central Mediterranean) (Fig. 1), is the widest and deepest known deep-sea coral community in the Mediterranean (Freiwald et al., 2009, Corselli, 2010). Living colonies of M. oculata and L. pertusa have been collected between 425 and 1100 m in depth in the SML CWC province (Tursi et al., 2004, Mastrototaro et al., 2010). The westernmost presence of both M. oculata and L.

Analysis of video records from APLABES project

The fishing impact due to both longlines and trawl nets are widespread in the FRA (Table 2 and Fig. 2). The number of impacts due to longline was the same of those due to trawl net. The greatest number of longline remains standardised to unit area (N/10 m2) was observed at the MS06-Yellow Chain geographic site (Fig. 3A) which comprises several elongated reliefs up to 25 m high characterized by the presence of living coral colonies (Vertino et al., 2010). Other geographic sites where longline

Discussion

The results of this work regard data collected both before (video survey) and after (observers׳ program and VMS data) the institution of the FRA in the SML CWC province. During the video survey, the same number of impacts due to longline and trawl net was recorded; however, the impacts due to longlines were significantly related to a geographic site characterized by coral mounds (MS06) while those from trawl nets were significantly related to fine-grained sediments (Table 2). The presence of

Acknowledgments

This study benefited from video recorded during the FIRB ‘APLABES’ (Apulian PLAteau Bank Ecosystem Study) using the RV ‘Universitatis’, from an observers׳ program carried out as part of the EU 7FP CoralFISH project (No. 213144) and from VMS data provided by the Italian Ministero delle Politiche Agricole Alimentari e Forestali (MIPAAF) – Direzione Generale Pesca. The authors acknowledge the RITMARE project funded by the Italian Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR)

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