New records of deep-water teleost fishes in the Balearic Sea and Ionian Sea ( Mediterranean Sea ) *

During an EC-funded research carried out in the Mediterranean Sea deep-water fish (600-4000 m) were collected in the Balearic Sea as well as the western and eastern Ionian Sea. Caelorhynchus mediterraneus is a new record for the Balearic Sea, Cyclothone braueri, Hygophum benoiti, Paralepis speciosa, Chalinura mediterranea, Coryphaenoides guentheri, C. mediterraneus, Lepidion lepidion and Cataetyx laticeps for the western Ionian Sea, and Polyacanthonotus rissoanus, C. guentheri, C. mediterraneus, L. lepidion and C. laticeps for the eastern Ionian Sea. The bathymetric distribution of other species has been updated. Species richness decreased with depth in the three surveyed areas, showing a significant shift below 1500 m. At depths greater than 1000 m macrourid and morid species were dominant except in the Balearic Sea, where Alepocephalus rostratus was found to be very abundant as deep as 1500 m. At depths greater than 1500 m the dominant species were Bathypterois mediterraneus, C. mediterranea and C. guentheri. The results of this research confirm the scarcity of deep fish fauna in the Mediterranean compared to the Atlantic. For the greatest depths are concerned, the faunistic difference between the western and eastern Mediterranean seems to be most probably due to a lesser number of investigations on the eastern side rather than any real paucity of ichthyofauna.


INTRODUCTION
The first proof of the presence of a deep-sea fauna in the Mediterranean was found by the Washington exploration (1881-83), during which trawls were carried out in the western basin as deep as 3115 m and some macrourid fish were caught and described (Giglioli, 1881).After this exploration, knowledge of Mediterranean deep-sea fauna was mainly provided by the Hirondelle and Princesse Alice expeditions , the ichthyological results of which are reported in Zugmayer (1911) and Roule (1919).The most extensive deep-sea faunistic exploration in the Levant basin of the Mediterranean occurred during the voyages of the Pola (1890)(1891)(1892)(1893).The Danish oceanographic cruises of the Thor (1908) and Dana (1928-29) also extended investigation from the Atlantic to the whole Mediterranean, even catching deep-sea fish at depths greater than 1000 m (Taning, 1918).All these cruises increased the knowledge of fish taxonomy and biodiversity (Tortonese, 1960;Ryland, 2000).
After the Danish oceanographic expeditions, the first noteworthy sampling of deep-sea fish in the Mediterranean was during the Polymède campaign made with the N.O.Jean Charcot (Geistdoerfer and Rannou, 1972) in the western basin and the German Meteor expedition in the eastern basin (Klausewitz, 1989).
In the last thirty years a large number of studies on ichthyofauna have also been conducted in both the western and eastern Mediterranean (Fredj and Maurin, 1987;Quignard and Tomasini, 2000, and references therein).However, they regard mostly depths shallower than 800 m, while knowledge on the ichthyofauna below this bathymetry remains rather scarce.Fredj and Maurin (1987) estimated that only 6 nektobenthic fish species have been strictly recorded at depths greater than 500 m and very little is known about their distribution in the Mediterranean as a whole.Quignard and Tomasini (2000) reported that the divergence in the faunal composition between the western and eastern basins seems to increase due to the migratory flux of Lessepsian fish limited to east of the Siculo-Tunisian sill.This sill has long been considered a geographical barrier to the bathybenthic and bathypelagic faunal mixing between the west and east of the Mediterranean (Tortonese, 1964), raising the question of the poorness of the eastern basin.
Photographs taken with automatic baited cameras dropped in the deep-water of the eastern Mediterranean have provided interesting contributions on active large scavengers dwelling on the deep-sea floor (Isaacs and Schwartzlose, 1975;Gilat and Gelman, 1984;Priede and Bagley, 2000;Jones et al., 2003).However, the baited camera approach suffers from the fact that quantification and even identification can be doubtful.
Considering the vast area covered by the Mediterranean below 1500 m and the various limitations occurring in the sampling of bathyal and abyssal fish species (Merrett and Haedrich, 1997), there is an evident need for further investigations in order to improve our knowledge of the fauna and zoogeography.An opportunity was recently provided by the DESEAS survey (finnanced by the EC), which explored Mediterranean bottoms down to 4000 m in depth.The main objective of this paper is to report the new records and to update the bathymetric distribution of the deep-water teleost fish collected during this survey.Due to the difficulties involved in deep-sea exploration (i.e. the time required to explore unknown deep-sea bottoms suitable to be trawled, the time required for a single haul and the decreasing sampling efficacy with depth), the results are qualitative.
The sampling was conducted with the otter trawl Maireta System (OTMS) using the R/V García del Cid (38 m long; 1500 HP).The OTMS (height 1.8-2 m; horizontal opening 14 m) was trawled by a single warp and operated with a pair of rectangular iron otter boards (1.20 x 2.0 m; 450 kg) (Sardà et al., 1998).The duration of the tow was measured by means of the SCANMAR sonar system.The vessel speed and position were measured using differential GPS.The trawling was carried out during daylight hours.The number of hauls and their depth is reported in Table 1.The deepest haul considered in the Balearic Sea was carried out eastwards between 38°04'N -5°27'E and 38°05'N -5°34'E.Haul duration ranged from 1 to 3 hours, but was standardised to 60 min.Specimens were identified on board following the nomenclature reported in Whitehead et al. (1984Whitehead et al. ( , 1986aWhitehead et al. ( , 1986b)).Total (TL, mm) and pre-anal lengths (PAL, mm) were measured according to the species.Due to the explorative objective of the DESEAS survey and the qualitative nature of this paper, no abundance or biomass indices were computed.The depth range and the number of hauls where the species were found are reported together with the total number of specimens caught and their total biomass.The percentages in number and weight of the species collected in each area were computed excluding the pelagic fish, because they may have been captured during the hauling of the net.Only Lampanyctus crocodilus was included in the analysis since the adult specimens of this species live close to the bottom (Stefanescu and Cartes, 1992).Qualitative species similarity between the three areas was calculated by means of the Sørensen (1948) index.The relationship between species richness and depth was analysed by regression function.The latter two analyses were also computed excluding the pelagic species.

Ichthyofauna composition
A total of 47 teleost fish belonging to 26 families were collected during the DESEAS survey and are listed in    benthopelagic, bathybenthic and with demersal habits, while 11 species are mesopelagic and bathypelagic.Excluding these latter species (with the exception of L. crocodilus), 27, 20 and 25 species were captured in the Balearic Sea, the western and eastern Ionian Sea respectively.
In the Balearic Sea, Alepocephalus rostratus constituted about 42% in number and 60% in weight of the specimens collected.Lepidion lepidion and Mora moro accounted for 8.3% of the total number and 21% of total biomass respectively.The family Macrouridae was represented by the highest number of species ( 7), about 26% of the total number and 7.8% of the total biomass of the specimens collected.The greatest abundance and biomass were provided by the grenadiers Nezumia aequalis (9.3%) and Trachyrhynchus trachyrhynchus (3.1%) respectively.Apart from Bathypterois mediterraneus, Phycis blennoides and Hoplostethus mediterraneus, the remaining species were represented in small numbers and biomass.
In the western Ionian Sea, B. mediterraneus was the most abundant species in number (33.7% of the specimens captured) while M. moro constituted 57.3% of the biomass of all specimens collected.A noteworthy contribution to the fish fauna of this area was provided by the Macrouridae family as a whole (23.6% in number and 12.3% in weight), of which N. sclerorhynchus and T. trachyrhynchus showed the highest percentage of abundance (11.7%) and biomass (5.8%) respectively.Apart from L. crocodilus, Nettastoma melanorum, Notacanthus bonapartei, L. lepidion and H. mediterraneus, the other species were present in very small numbers.
In the eastern Ionian Sea, Helicolenus dactylopterus constituted 19.6% in number and 42.6% in weight of the specimens captured in the area.rorhynchus was the main component (6.3% in number).Noteworthy abundance and biomass percentages were found for L. crocodilus and H. mediterraneus respectively.The Sørensen similarity indexes were 77% between the Balearic and western Ionian, 71% between the western and eastern Ionian, and 62% between the Balearic and eastern Ionian.
In all three study areas the species richness decreased with depth, showing a shift below 1500 m (Fig. 2).The relationship was best described by a power function (species richness = 4991.3depth -0.9425 ) with statistically significant results (r 2 = 0.66; p < 0.01).

New records
Polyacanthonotus rissoanus (Filippi and Vérany, 1859) This benthopelagic species had been collected between the Balearic Islands and Sardinian waters at a depth of 2830 m (Geistdoerfer and Rannou,1972).Recently, it was caught by Stefanescu et al. (1992a) and Moranta et al. (1998) in the Catalan Sea and off the Balearic Islands respectively.In the eastern Mediterranean a specimen was found at a depth of 1400 m (171 mm TL) (Goren and Galil, 1997).During the DESEAS cruise 2 specimens (150 and 180 mm TL) were captured for the first time in the eastern Ionian Sea from depths of 2200 and 2600 m.

Chalinura mediterranea Giglioli, 1893
The first finding of this species in the Mediterranean was in the Tyrrhenian Sea from depths of 2805-2904 m (Giglioli, 1881).Specimens were collected off Nice at depths of 2200-2400 m (Carpine, 1970).Geistdoerfer and Rannou (1972) captured 14 specimens at four stations off North Africa between the Balearic Islands and Sardinia, from 2370 to 2830 m.In the Catalan Sea C. mediterranea was found between 1308 and 2251 m (Stefanescu et al., 1992a) and south of the Balearic Islands between 1400 and 1800 m (Moranta et al., 1998).In this sector, during the present study 33 specimens (22-98 mm PAL) were sampled at 1500, 2500 and 2800 m, updating the vertical distribution shown previously.This is the first record of the species from the western Ionian Sea, 11 specimens (8-85 mm PAL) were collected between 1500 and 4000 m, the deepest the species has been sampled by trawling in the Mediterranean.
In the eastern Ionian Sea (35°54'N 22°21'E) C. mediterranea was captured at 4500 m using traps (Albertelli et al., 1992), a depth record for the Mediterranean.Records of C. mediterranea in the eastern Mediterranean were taken using lander platforms equipped with baited cameras and baited trap deployments between 1500 and 4264 m (Jones in Priede and Bagley, 2000;Jones et al., 2003).During the DESEAS sampling in the eastern Ionian Sea 6 specimens (30-65 mm PAL) were collected between 1300 and 2600 m.
Coryphaenoides guentheri (Vaillant, 1888) C. guentheri is widespread throughout the Mediterranean (Whitehead et al., 1986a).This species was found for the first time in the western Mediterranean between Balearic and Sardinian waters (2370-2830 m) (Geistdoerfer and Rannou, 1972 as Chalinura guentheri).In the Catalan Sea, it is known at depths between 1200 and 2251 m (Stefanescu et al., 1992a(Stefanescu et al., , 1994)), and off the southern Balearic Islands between 1400 and 1800 m (Moranta et al., 1998).In the present study 17 specimens (35-82 mm PAL) were hauled at 2500 and 2800 m in the Balearic Sea; 5 specimens (24-60 mm PAL, 1500-1700 m) and 3 specimens (55-88 mm, 1700-2600 m) were collected in the western and eastern Ionian Sea respectively.Iwamoto and Ungaro, 2002 This grenadier fish has been recently described by Iwamoto and Ungaro (2002) from specimens collected in the western and central Mediterranean.These authors reported that the species was previously recorded in the western Mediterranean as C. vaillanti off Corsica (Raimbault, 1963) and in the Ligurian Sea (Orsi and Relini, 1972), as C. occa in the Catalan Sea by Allué (1983) and Allué et al. (1984) and as C. labiatus in the Catalan Sea by Stefanescu et al. (1992aStefanescu et al. ( , 1992b) ) and Massutí et al. (1995).In the Adriatic Sea the species was found at depths between 1015 and 1196 m, initially reported as C. occa (Ungaro et al., 2001) and then described as a new species (Iwamoto and Ungaro, 2002).

Caelorhynchus mediterraneus
In the Catalan Sea the misidentified C. labiatus (actually C. mediterraneus) was found in the depth range of 1046-2201 m (Stefanescu et al., 1992a) and off the southern Balearic Islands between 1200 and 1800 m (Moranta et al., 1998).The first finding of C. labiatus in the eastern Mediterranean recorded by Galil and Goren (1994) from depths of 1390-1500 m, not cited by Iwamoto and Ungaro (2002), most probably also corresponds to C. mediterraneus.
The specimens of C. mediterraneus collected during the DESEAS survey had the same features (snout shape, squamation, color and size) indicated in the description of the species (op.cit.).In the Balearic Sea 36 specimens (33-90 mm PAL) were found at depths of 1200 and 1500 m.The findings in the western and eastern Ionian Sea represent the first records of the species in these two areas.In the former, 34 specimens (38-86 mm PAL) were sampled from depths of 1200-1500 m, and in the latter only 2 specimens (95 and 107 mm PAL) were caught at a station at 1300 m.

Lepidion lepidion (Risso, 1810)
The presence of Lepidion lepidion in the western Mediterranean (between north Africa and south Sardinia, at 2450 m depth) dates back to the Polymède campaign (Geistdoerfer and Rannou, 1972).In the Catalan Sea this fish was found in the depth range of 984-2251 m (Stefanescu et al., 1992a) and off the southern Balearic Islands between 1000 and 1800 m (Moranta et al., 1998).In this latter area, during the present research, 77 specimens (70-318 mm TL) were captured at depths between 1000 and 1500 m.
L. lepidion has recently been recorded in the Adriatic Sea from depths of 1015-1196 m (Ungaro et al., 2001).In the eastern Mediterranean its occurrence has been recorded using deep-water photographic equipment and baited traps: in the Cretan Sea between 1500 and 2500 m and in the Rhodes Basin between 2300 and 3850 m (Jones in Priede and Bagley, 2000;Jones et al., 2003).During the DESEAS cruise L. lepidion was found down to 1700 m in both the western and eastern Ionian Sea, with 22 specimens (145-291 mm TL) in the former and 8 specimens (165-310 mm TL) in the latter.

Cataetyx laticeps Koefoed, 1927
One juvenile and two adults were sampled for the first time in the Mediterranean at depths of 2830 and 2370 m respectively during the Polymède campaign (Geistdoerfer and Rannou, 1972).C. laticeps was collected between 1739 and 2251 m in the Catalan Sea (Stefanescu et al., 1990(Stefanescu et al., , 1992a) and down to 1800 m south of the Balearic Islands (Moranta et al., 1998).In this area 6 specimens (90-500 mm TL) were collected from depths of 2500 and 2800 m during the DESEAS cruise.
In the eastern Mediterranean one specimen (350 mm TL) was found at a depth of 1400 m off the Israeli coast (Goren and Galil, 2002).During this research 4 specimens (311-384 mm TL) were collected in the western Ionian between 2000 and 3300 m and 10 specimens (200-397 mm TL) in the eastern Ionian between 1700 and 2600 m.

Halosaurus ovenii Johnson, 1863
This benthopelagic species was reported between 400 and 1700 m (Whitehead et al., 1986a).A speci-men (229 mm TL) was collected off the Balearic Islands (38°04'N 5°27'E; 38°05'N 5°34'E) at a depth of 2800 m.The present finding represents the deepest record of the species in both the Mediterranean and the northeast Atlantic.
Bathypterois mediterraneus Bauchot, 1962 The tripodfish was previously collected by Geistdoerfer and Rannou (1972) between the Catalan Sea and off north Africa at depths between 2140 and 2830 m.More recently, it was recorded both in the Catalan Sea as deep as 2251 m (Stefanescu et al., 1992a;Morales-Nin et al., 1996b) and off the southern Balearic Islands down to 1800 m (Moranta et al., 1998).In this latter area during the present study specimens were found between 1000 and 2800 m.
The occurrence of B. mediterraneus in the western Ionian Sea has long been known (Bauchot, 1963;Geistdoerfer and Rannou, 1972).The present finding, between 800 and 3300 m, broadens its known vertical distribution in the area and in the whole Mediterranean Sea.The presence of B. mediterraneus in the eastern Ionian Sea and slightly eastwards was reported by Klausewitz (1989) (1433-1626 m south-east of Crete and 2572-2596 m south-west of Cyprus).During the DESEAS cruise it was collected between 800 and 2600 m.
Lampanyctus crocodilus (Risso, 1810) Carpine (1970) sampled some specimens of this species off Nice trawling at depths between 2200 and 2400 m.Moranta et al. (1998) reported the occurrence of the species south of the Balearic Islands at a maximum depth of 1800 m.During the DESEAS cruise specimens were collected from 650 to 2500 m.
L. crocodilus has been collected in the Ionian Sea since the Thor expedition in the Mediterranean (Taning, 1918).During June 2001, specimens were caught in the western Ionian from 600 down to 3300 m, the greatest depth at which the species has been found in the area and anywhere in the Mediterranean.In the eastern Ionian it was found down to 1300 m in depth.

Nettastoma melanorum Rafinesque, 1810
The species was recorded off the Balearic Islands down to 1400 m by Moranta et al. (1998).During the DESEAS survey, it was captured between 600 and 1500 m in the western Ionian and between 600 and 1300 m in the eastern Ionian.
Phycis blennoides (Brünnich, 1768) Although in the Catalan Sea Phycis blennoides was recorded in the depth range 960-1308 m (Stefanescu et al., 1992a), off the southern Balearic Islands it was only collected down to about 1000 m (Moranta et al., 1998).In this area during the DESEAS survey the species was sampled as deep as 1200 m.
In the Levant basin P. blennoides was recorded down to 1200 m in depth (Goren and Galil, 1997).This teleost is common in the western Ionian Sea where it is generally caught at a maximum depth of 800 m (Parenzan, 1960;Pastore, 1976;Franceschini et al., 1993;Matarrese et al., 1996).In June 2001, for the first time, it was sampled down to 1000 m.
Mora moro (Risso, 1810) This teleost is one of the most abundant species between 800 and 1400 m off the southern Balearic Islands (Moranta et al., 1998).It has been caught off Crete from 800 to 1000 m (Kallianiotis et al., 2000) and in the Adriatic Sea from 826 to 1196 m (Ungaro et al., 2001).During the DESEAS campaign M. moro was sampled down to 1200 m in the western Ionian and 1300 m in the eastern Ionian.
Notacanthus bonapartei Risso, 1840 and Nezumia sclerorhynchus (Valenciennes, 1838) are common species in the Ionian Sea, generally caught at a maximum depth of 800 m (Parenzan, 1960;Papaconstantinou, 1988;Matarrese et al., 1996;D'Onghia et al., 1998a).During the present study both species were sampled between 600 and 1500 m on the western side of the Ionian Sea.N. bonapartei was collected at a depth of 1100 m and N. sclerorhynchus at a depth of 1300 m in the eastern area of this basin.
Trachyscorpia cristulata echinata (Koehler, 1896) was found during a haul carried out at 1500 m in the Balearic Sea.Its previous finding was in the Alboran Sea (Maurin, 1962;Fredj and Maurin, 1987) and off the Balearic Islands (Massutí et al., 1993), but at a maximum depth of 1000 m.Recently, a small specimen (144 mm TL) was collected off western Sicily at a depth of 600 m (Ragonese and Giusto, 1999).
The new records and the updated depth ranges of the benthopelagic and demersal species collected during the DESEAS survey are shown in Figure 3. DISCUSSION Despite sampling limitations, which caused a different number of hauls and a different sounded depth range in the three areas, this study provides new faunistic and biogeographic data on the Mediterranean deep-sea ichthyofauna.
New records of deep-water fish are presented mostly for the Ionian Sea, in which the least research into deep-sea fish fauna has been carried out.
The finding of C. mediterraneus in all three areas confirms its distribution throughout the Mediterranean (Iwamoto and Ungaro, 2002).The specimens described as C. labiatus in the Levant Sea (Galil and Goren, 1994) are probably C. mediterraneus.
The absence of C. caelorhynchus in our samples from the Ionian Sea was due to the small number of hauls within the species depth range (Cohen et al., 1990).The species is rather common on the upper slope in the Ionian Sea (D'Onghia et al., 1998a(D'Onghia et al., , 2000;;Labropoulou and Papaconstantinou, 2000).
The depth distribution of several species has been updated.For L. crocodilus, B. mediterraneus and C. laticeps, it is the greatest depth recorded in the Mediterranean.In our opinion, the greatest depth at which some pelagic species were found cannot be reliably considered as the species depth range since they may have been captured in shallower waters during the hauling of the net.However, bathypelagic species, such as Stomias boa and Chauliodus sloanei, have also been reported below 3000 m in the Atlantic (Tortonese, 1960).Moreover, the presence of this latter bathypelagic fish, together with B. mediterraneus and C. laticeps, has been documented at a depth of 2900 m in the Levantine basin of the Mediterranean Sea using a remote operating vehicle (Galil, 2004).
Although some differences were shown in the ichthyofauna composition between the three areas, the same pattern of the species richness with depth was shown in each of them.Below a depth of 1000 m, the species of the Macrouridae and Moridae families were dominant in all three areas investigated, with the exception of the overwhelming presence of A. rostratus in the Balearic Sea.At depths greater than 1500 m, the dominant species were B. mediterraneus, C. mediterranea and C. guentheri (Stefanescu et al., 1992a(Stefanescu et al., , 1993;;Moranta et al., 1998;Goren and Galil, 2002).In agreement with the observations of the latter authors, L. crocodilus was found with noteworthy abundance on both sides of the Ionian Sea.Despite the sampling limitations, the qualitative faunistic similarity between the three areas was rather high.Considering that some common species, such as C. agassizii, C. caelorhynchus and L. boscii, were only found in one of the areas sampled, the similarity between the areas can be considered even higher than that estimated.In addition, this survey suffers from limitations common to many simple exploratory tools, such as the fact that its samples are highly selective.Thus, species known to be distributed in both the Balearic Sea and the Ionian Sea were not caught by the net used.
The number and biomass shown for A. rostratus in the western Mediterranean according to previous studies (Stefanescu et al., 1993;Morales-Nin et al., 1996a;Moranta et al., 1998), and the total lack in the two easternmost areas in the ten hauls carried out in its depth distribution range (984-2209 m, according to Stefanescu et al., 1992a), might be the consequence of its exclusive distribution in the western Mediterranean.The same consideration may also be valid for N. aequalis, which seems to be only distributed on this side of the Mediterranean, although the main check-lists report this species distributed throughout the basin (Whitehead et al., 1986a;Bauchot, 1987;Cohen et al., 1990).On the other hand, the presence of N. sclerorhynchus in the western Mediterranean has long been known (e.g.Rannou, 1975Rannou, , 1976)).
The absence of these species in the eastern Mediterranean remains an open question.According to Galil and Goren (1994), their absence might be due to the distance from the point of faunal entry at the Gibraltar Strait and to the shallow Siculo-Tunisian sill.However, this contrasts with the fact that many other deep-water Atlantic species are widespread in the Mediterranean.Moreover, the exclusive abundant occurrence of A. rostratus and N. aequalis only off the Balearic Islands might also be the consequence of the different trophic conditions between the west and east Mediterranean.In fact, megafaunal biomass in the deep sea is linked to the surface productivity regime (Haedrich and Rowe, 1977;Gordon 1979;Merrett, 1987).As recently reported by Danovaro et al. (1999), primary production, chlorophyll a concentrations and carbon fluxes in the western Mediterranean are significantly higher than in the eastern Mediterranean, and influence bacterial and meiofaunal densities and biomass.Melley et al. (2000) reported that, in the context of oligotrophic Mediterranean conditions, the western basin shows nitrogen and phosphate concentrations of about 90 and 129% respectively greater than the Ionian Sea.Maynou and Cartes (2000) reported that phytoplankton pigment concentration differs by almost an order of magnitude between the western and eastern Mediterranean Sea.
In addition, Moranta et al. (1998) reported that A. rostratus is more abundant south of the Balearic Islands (Balearic Sea in this study) than north of the islands where the species L. lepidion and B. mediterraneus are more abundant.According to Moranta et al. (1998) and Massutí et al. (2004), the differences between the megafauna of these areas could be due to the differences in trophic transfer systems.South of the Balearic Islands where much of the food is of planktonic origin, the most abundant species is A. rostratus, which feeds mainly on gelatinous macroplankton (Carrassón and Matallanas, 1990), while north of the Balearic Islands, where benthic and benthopelagic organisms form the important food resources (Cartes et al., 1994), the most abundant species are L. lepidion and B. mediterraneus, which prey on benthic decapods (Carrassón et al., 1997) and benthopelagic crustaceans (Carrassón and Matallanas, 2001) respectively.These different conditions in the trophic web, due to surface productivity and the presence of canyons, could explain the absence of A. rostratus in the Ionian Sea, where submarine canyons are widespread on the slope (D'Onghia et al., 1998b).
Even though these conditions could be the cause of the exclusive presence of A. rostratus in the western Mediterranean, they do not explain the lack of N. aequalis in the eastern basin.In fact, this fish has a feeding niche that overlaps with N. sclerorhynchus and C. caelorhynchus (Geistdoerfer, 1975;Macpherson, 1979;Marques and Almeida, 1998), which are both abundant in the eastern Mediterranean.The diet overlap could be responsible for the competitive exclusion of N. aequalis in the Ionian Sea, since N. sclerorhynchus is the dominant macrourid fish in this basin at the same depths at which N. aequalis is distributed in the Balearic Sea (Moranta et al., 1998;and in this study).N. aequalis may be present in the western and eastern Ionian Sea but since it is less abundant than N. sclerorhynchus it could have been misidentified because its identification depends on analysis of scales, otoliths and morphological features (Cohen et al., 1990;Marques and Almeida, 1998).
The DESEAS results confirm the abundance of C. agassizii and H. dactylopterus on the upper slope of the eastern Ionian Sea.This might be due to the absence of fishing pressure in this area below 400-500 m in depth (D'Onghia et al., 2003).However, according to these authors, the differences in the ichthyofauna composition and abundance between the eastern and western Ionian upper slope could also be due to the different hydrographic conditions on the two sides of the basin.Along the Greek coasts the water masses are warmer and have high salinity, while along the Italian ones they are colder and slightly less saline (Robinson and Golnaraghi, 1992;Theocaris et al., 1993).
Finally, the DESEAS results confirm the scarcity of deep fish fauna in the Mediterranean compared to the Atlantic (Haedrich et al., 1980;Gordon and Duncan, 1985;Haedrich and Merrett, 1988).The recent origin of the deep-sea fauna in the Mediterranean, the "canal effect", the high temperature and the oligotrophy of the basin are considered the main causes of this qualitative and quantitative poverty (Fredj and Maurin, 1987;Bouchet and Taviani, 1992;Quignard and Tomasini, 2000).
Although some differences have been detected between the ichthyofauna of the three study areas, common patterns are shown in the faunistic composition at the greatest depths, indicating that the difference between the western and eastern Mediterranean seems to be most probably due to a lesser amount of research work on the eastern side rather than a real paucity of ichthyofauna.For instance, Tortonese (1960) reported in his remarks on the Mediterranean deep-sea fishes that "L.crocodilus becomes gradually scarcer eastward".On the contrary, during the DESEAS cruise this fish was found to be more abundant in the eastern Ionian Sea than in the Balearic Sea.L. crocodilus is also one of the most abundant deep-sea fishes of the Levantine basin (Goren and Galil, 2002).
Considering the different swimming behaviour of the deep-water fishes and the sampling limitations of the trawl net, this study confirms that gaps in the knowledge on the deep-sea fauna and zoogeography of the Mediterranean can only be overcome by using different recording techniques and sampling methods.
FIG. 3. -Updated depth ranges of the deep-water benthopelagic and demersal teleost fishes collected during the DESEAS survey.The symbol (N) indicates new records for the study areas.

Table 2 .
Most of them are strictly benthic, NEW RECORDS OF DEEP-WATER TELEOST FISH IN THE MEDITERRANEAN 173

TABLE 1 . -Number of hauls by depth carried out in the three study areas during the DESEAS survey.
Map of the Mediterranean Sea with indication of the study areas during the DESEAS survey.

TABLE 2 .
-Species collected in the Balearic Sea, in the western and eastern Ionian Sea during DESEAS survey, with indication of depth range, number of hauls in which the species were caught, total number (N) and total biomass (g); *, indicates the mesopelagic and bathypelagic species.