Survey Results for Italy - area M4 - Part 1: SW Adriatic and NW Ionian Seas

by G. Marano*, A. Tursi**, G. D'Onghia**, N. Ungaro*

* LBMB, Bari, Italy

** DIZO, Bari, Italy

Introduction

The results on the Medits-IT 1999 survey, regarding to southwestern Adriatic and northwestern Ionian Sea (M4 region, strata 22101-22140), are presented in this report.

The survey was carried out, as the previous year, using the fishing vessel "Pasquale e Cristina”. A total of 146 hauls were realized in the study area (28793 km²).

During Medits-IT M4 1999 the most abundant species in weight over the whole M4 area, were Micromesistius poutassou (22.18 kg/km²), Merluccius merluccius (14.56 kg/km²), Galeus melastomus (9.52 kg/km²), Illex coindetii (9.15 kg/km²), Trachurus trachurus (8.39 kg/km²), Phycis blennoides (6.13 kg/km²), Mullus barbatus (5.65 kg/km²), Helicolenus dactylopterus (5.39 kg/km²), Lophius budegassa (4.16 kg/km²); the highest densities (N/km²) were provided by Micromesistius poutassou (2993 N/km²), Trachurus trachurus (1184 N/km²), Mullus barbatus (592 N/km²), Parapenaeus longirostris (400 N/km²), Trisopterus minutus capelanus (379 N/km²), Phycis blennoides (317 N/km²), Merluccius merluccius (310 N/km²), Illex coindetii (280 N/km²).

Some differences in the biomass and density indices were recorded among the areas and years. Concerning the areas, some species, such as Galeus melastomus, Mullus barbatus and Trisopterus minutus capelanus, were found more abundant in the Adriatic Sea while some others, such as Micromesistius poutassou, Trachurus trachurus and Parapenaeus longirostris, were caught with the highest biomass and density in the Ionian basin. The species Phycis blennoides and Helicolenus dactylopterus provided a greater abundance in weight in Adriatic than in the Ionian Sea and vice versa for the abundance in number. The abundances, both in weight and number, of M. merluccius and I. coindetii were rather comparable between the Adriatic and Ionian waters.

With regard to the previous year (1998), Merluccius merluccius showed a slight decrease of the abundance in weight (14.56 vs. 18.2 kg/km²) and number (310 vs. 524 N/km²). A marked increase of the yield has been observed for Micromesistius poutassou (22.18 vs. 8.0 kg/km²). Greater abundance values than the previous survey (1998) were recorded for Mullus barbatus, Trachurus trachurus, Phycis blennoides, Helicolenus dactylopterus and Illex coindetii. A decrease of the yield was shown in Eledone cirrhosa, Parapenaeus longirostris and Aristeus antennatus. The significant abundance of Aristeus antennatus observed in the southernmost sector of Adriatic Sea during 1997 was recorded neither in 1998 nor in 1999.

Global comments for Fish, Crustaceans and Cephalopods, Survey 1999

Fish

Aspitrigla cuculus

This fish was almost exclusively caught in the Adriatic Sea with the highest abundance index in the 200-500 m depth stratum and sector 221h (41.29 kg/km² and 3699 N/km²).

Citharus linguatula

Not found at all.

Eutrigla gurnardus

The species was exclusively caught on the continental shelf of both Ionian and Adriatic Sea with negligible abundance indices.

Galeus melastomus

This selachian was collected at depths greater than 200 m in both sub-areas. In the Ionian Sea the highest abundance values (43.50 kg/km² and 289 N/km²) were shown between 500 and 800 m in the sector 221c while in the Adriatic the highest density value (1111 N/km²) and biomass index (91.49 kg/km²) were detected in the 200-500 m stratum of the sector 221f and 500-800 m of the sector 221e, respectively.

A wide range of size was shown both in Adriatic (11-58 cm TL) and Ionian Sea (12-56 cm TL).

Helicolenus dactylopterus

This teleost fish was mainly collected at depths greater than 100 m. It was found with the highest biomass index in the Adriatic Sea, between 500 and 800 m (109.24 kg/km²) and the highest density along the Ionian coast in the depth stratum of 100-200 m (1155 N/km²).

The size of the specimens ranged from 4 to 31 cm TL in Adriatic and from 3 to 30 cm TL in the Ionian. In this latter district a higher percentage of small individuals (< 10 cm TL) was found. An increase of the average size with depth was observed in both sub-areas.

Lepidorhombus boscii

This species was generally caught between 100 and 500 m with negligible biomass and density indices. The average biomass index for the whole M4 area was 0.6 kg/km² in 1998 and 0.59 kg/km² in the last survey.

Lophius budegassa

Lophius budegassa was found across the whole depth range investigated. Both the highest biomass index (25.94 kg/km²) and density value (331 N/km²) were observed in the sector 221b of the Ionian Sea, the former between 100 and 200 m and the latter within 50 m.

The largest specimens found in Adriatic and Ionian measured 66 and 45 cm TL respectively. A higher percentage of small individuals (< 15 cm TL) were found in the Ionian Sea.

Lophius piscatorius

Also this species was found across the whole depth range investigated. However, apart from some noteworthy exception observed in Adriatic (48.57 kg/km² in 500-800 m; 11.72 kg/km² in 200-500 m and 10.17 kg/km² in 50-100 m) the abundance indices were rather negligible.

Merluccius merluccius

Generally abundant in the whole area and across the whole vertical range. In the Ionian Sea the highest biomass index (46.33 kg/km²) and density index (5198 N/km²) were found in the third depth stratum (100-200 m) of the sector 221c. In the Adriatic Sea the highest biomass index (48.57 kg/km²) and density (829 N/km²) were computed for the second stratum (50-100 m) of the sector 221e.

Although a wide range of sizes was shown both in Adriatic (5-76 cm TL) and in the Ionian (4-61 cm TL), the bulk of the stock was made up of specimens smaller than 25 cm TL in both basins. The fraction of large specimens (> 30 cm TL) was more abundant in the southwestern Adriatic Sea than in the Ionian.

Micromesistius poutassou

The species was found with remarkable abundance in the Ionian Sea. Here the highest biomass index (894.81 kg/km²) and density (86221 N/km²) were obtained at depths between 100 and 200 m in the sector 221b. In the Adriatic the greatest abundance indices (13.73 kg/km² and 699 N/km²) were recorded at depths between 200 and 500 m in the sector 221f.

Minimum and maximum sizes were 4 and 40 cm TL respectively in Adriatic and 6 and 38 cm TL respectively in the Ionian. In the former area the stock was mostly represented by specimens with total length between 10 and 20 cm, in the latter the highest percentage of sizes was between 5 and 15 cm TL. These small specimens were mostly caught between 100 and 200 m. The largest specimens were generally found at depth greater than 200 m.

Mullus barbatus

The species was caught almost exclusively on the continental shelf (<200 m). The highest biomass (between 28.15 and 88.08 kg/km²) and density indices (between 4342 and 19317 N/km²) were found in Adriatic within 50 m of depth. The highest abundance values in the Ionian Sea (19.4 kg/km² and 431 N/km²) were recorded at depths between 100 and 200 m in the sector 221b.

A noteworthy pulse of recruitment, made up of specimens with sizes between 4 and 9 cm TL, was found in the Adriatic Sea. The majority of specimens caught in the Ionian sectors had a total length between 10 and 18 cm.

Mullus surmuletus

This fish was caught as far as the 200-500 m depth stratum. The highest biomass index and density were 61.41 kg/km² and 1063 N/km² respectively. Apart from these values recorded in Adriatic, between 10 and 50 m in the sector 221g, its catch in the whole study area was somewhat negligible.

The size-range was 9-28 cm TL in Adriatic and 16-26 cm TL in the Ionian Sea.

Pagellus acarne

This species was found in a wide depth range with low abundance. The highest biomass index of 9.08 kg/km² and the highest density of 520 N/km² were found along the Adriatic coast, within 50 m of depth in the sector 221g.

Pagellus bogaraveo

Few specimens of this species were fished on the deepest bottoms.

Pagellus erythrinus

This fish was almost exclusively found on the continental shelf (10-200 m) and mainly in the Ionian waters where the highest biomass index (30.41 kg/km²) and density (1620 N/km²) were recorded in the sector 221d. In Adriatic the highest abundance (5.2 N/km²; 158 N/km²) was obtained in the sector 221f.

The smallest and greatest specimens measured 6 and 22 cm TL respectively in the Ionian waters and 8 and 19 cm TL respectively in Adriatic.

Phycis blennoides

This teleost was found on a wide depth range and mostly between 200 and 800 m. It exhibited the highest biomass index (73.11 kg/km²) in the southern Adriatic Sea (in the 500-800 m stratum of the sector 221f) and the highest density (2809 N/km²) in the northern Ionian Sea (in the 200-500 m stratum of the sector 221d).

A wide range of sizes, up to 48 cm TL in the Ionian and 50 cm TL in Adriatic, was shown. However, the bulk of stock was made up of specimens with sizes between 5 and 12 cm TL in the former area and between 10 and 17 cm TL in the latter.

Raja clavata

This species was found with few specimens in the 221h Adriatic sector at depths between 200 and 500 m.

Scyliorhinus canicula

This shark was caught with few specimens between 100 and 200 m in Adriatic (sector 221e) and between 200 and 500 m in the Ionian (sector 221a and 221b).

Solea vulgaris

Only 3 specimens were collected within 50 m of depth in Adriatic Sea (sector 221h).

Spicara flexuosa

The species was found as far as 200 m. The highest biomass index (56.04 kg/km²) and density (3205 N/km²) were observed in the second depth stratum of the sector 221b of the Ionian Sea.

The size of the specimens ranged from 10 to 19 cm TL in the Ionian and from 8 and 18 cm TL in Adriatic.

Spicara smaris

This fish was collected with negligible abundance indices as far as 200 m of depth both in Adriatic and Ionian Sea.

Trachurus mediterraneus

This species was mainly caught on the continental shelf (<200 m) with low biomass and density values in both investigated basins. The highest biomass index value was 9.58 kg/km² in Adriatic Sea and 11.32 kg/km² in the Ionian. The highest density values were 123 N/km² and 137 N/km² in Adriatic and Ionian respectively.

A broad size-range was shown in both Adriatic (7-34 cm TL) and Ionian Sea (4-26 cm TL).

Trachurus trachurus

This species was caught as far as 500 m of depth. In the Ionian Sea the highest abundance indices were found in the sector 221b at depths between 100 and 200 m (75.95 kg/km²; 16371 N/km²) while in Adriatic they were shown in the sector 221g in the same depth range (39.79 kg/km²; 6127 N/km²).

The sizes of this fish ranged from 4 to 35 cm, however the small specimens were dominant in the catches. The majority of the individuals had a total length between 5 and 12 cm both in the Ionian and Adriatic Sea.

Trigloporus lastoviza

This fish provide negligible catches within 50 m of depth in the northernmost sector of the Ionian Sea and within 200 m in all sectors of Adriatic.

Trisopterus minutus capelanus

The highest biomass index (15.75 kg/km²) and density (2090 N/km²) were found in the sector 221h of Adriatic Sea, between 50 and 100 m.

Zeus faber

The species was found to be rare in the whole study area.

Crustaceans

Aristaeomorpha foliacea

This shrimp was caught beyond 200 m of depth. In the Ionian Sea the highest abundance indices of 4.19 kg/km² and 791 N/km² were found in the 200-500 m of the sector 221d while in Adriatic the greatest biomass (3.78 kg/km²) and density (236 N/km²) were shown between 500 and 800 m of the sector 221h.

Minimum and maximum carapace lengths were 13 and 64 mm respectively in the Ionian and 17 and 54 mm respectively in Adriatic Sea.

Aristeus antennatus

This species was mostly collected in the deepest waters of the Ionian Sea and of the southernmost sector of the Adriatic Sea. The highest biomass and density indices were 26.27 kg/km² and 1364 N/km² respectively. They were obtained at 500-800 m depth stratum of the sector 221d.

In the Ionian Sea the carapace lengths ranged from 16 to 63 mm whereas in Adriatic the sizes were between 20 and 48 mm CL.

Nephrops norvegicus

The species was caught at depths greater than 50 m in Adriatic and 100 m in the Ionian. In the former area the highest abundance indices (15.99 kg/km²; 537 N/km²) were observed between 200 and 500 m of the sector 221f, in the latter the highest values (5.90 kg/km²; 368 N/km²) were obtained in the same depth range of the sector 221d.

A wide range of sizes, between 9 and 73 mm CL, was shown in the Ionian Sea while the carapace length ranged from 19 to 57 mm in the Adriatic waters. However, individuals whose sizes were between 20 and 50 mm CL constituted the bulk of the stock in both sub-regions.

Parapenaeus longirostris

This shrimp was caught at depth greater than 50 m and mainly between 200 and 500 m in the Ionian sub-area. It exhibited the highest biomass index (23.40 kg/km²) at 200-500 m while the greatest density (4515 N/km²) in the 100-200 m depth stratum, both along the Sicily coast (sector 221a). In Adriatic the highest abundance values (4.63 kg/km²; 387 N/km²) were shown at 200-500 m of the sector 221f.

In the Ionian Sea, the stock of this shrimp was made up of specimens with sizes between 7 and 40 mm carapace length. However, the majority of individuals had sizes between 10 and 20 mm CL. In Adriatic Sea, the sampled population exhibited sizes between 10 and 37 mm CL. An increase of the average size according to depth was shown in the whole study area.

Cephalopods

Eledone cirrhosa

It was fished as far as 500 m of depth with the highest yields in weight between 100 and 200 m in the Ionian Sea (11.82 kg/km²) and between 200 and 500 m in Adriatic (12.37 kg/km²). The highest density indices were shown at 100-200 m in both subareas (193 N/km² in the Ionian and 68 N/km² in Adriatic).

The size-frequency distributions exhibited two modal components, corresponding to 2-5 cm and 8-12 cm DML, in both Ionian and Adriatic Sea.

Eledone moschata

This cephalopod was mostly caught within 200 m of depth with biomass indices up to 18.65 kg/km² (sector 221a of the Ionian Sea) and density up to 54 N/km² (sector 221h of the Adriatic Sea).

Illex coindetii

The species was caught across the whole-investigated areas and depths. The greatest biomass index (89.39 kg/km²) was found in the Ionian basin between 100 and 200 m (sector 221b) while the highest density (1471 N/km²) in Adriatic at 50-100 m (sector 221e).

The size-range was 4-23 cm DML in the Ionian and 3-21 cm DML in Adriatic. Small specimens (< 10 cm DML) were found in both sub-regions.

Loligo vulgaris

It was only caught with noteworthy abundance values (47.31 kg/km²; 3154 N/km²) on the continental shelf of the Adriatic Sea.

Octopus vulgaris

This cephalopod species was almost exclusively found within the continental shelf of both basins. The highest abundance indices (19.93 kg/km²; 173 N/km²) were shown in the first 50 m of the sector 221f (Adriatic Sea).

Sepia officinalis

The species was only found within 50 m of depth. The highest biomass index of 10.56 kg/km² was obtained in the Sicily waters (sector 221a) while the highest density value of 103 N/km² was shown in the northernmost sector of Adriatic Sea (sector 221f).

Comments by stratum, survey 1999

Stratum 10-50 m

Considering the whole study area and both biomass and density indices, in the first depth stratum (10-50 m), the five most important species were Mullus barbatus, Trachurus trachurus, Spicara flexuosa, Pagellus erythrinus and Merluccius merluccius.

During Medits-IT 1999 the highest abundance indices of Mullus barbatus estimated for the two main sub-regions of M4 area were 88.08 kg/km² and 19317 N/km² for the Adriatic Sea and 9.71 kg/km² and 274 N/km² for the Ionian Sea.

The biomass indices of Trachurus trachurus ranged from 0.48 to 66.3 kg/km², corresponding to density values from 80 to 10617 N/km², in the north-western Ionian Sea while they were between zero and 31.94 kg/km² (2410 N/km²) in the south-western Adriatic.

Spicara flexuosa was mostly caught in the southernmost sectors of the Ionian, as observed in the previous year. The abundance indices were 34.7 kg/km² and 1724 N/km² in the Sicilian side (sector 221a) and 19.54 kg/km² and 1165 N/km² along the Calabrian coast (sector 221b). In the southwestern Adriatic Sea the species was collected with biomass indices up to 4.0 kg/km² and density values up to 203 N/km².

Also Pagellus erythrinus was mainly found in the Ionian basin, both in the southernmost sector (28.15 kg/km² and 801 N/km²) and in the northernmost one (30.41 kg/km² and 1620 N/km²). The greatest abundance indices obtained in the Adriatic were 5.2 kg/km² and 158 N/km².

The catch of Merluccius merluccius in this stratum provided biomass and density indices of 19.57 kg/km² and 709 N/km² in the Ionian and 14.21 kg/km² and 383 N/km² in Adriatic.

Stratum 50-100 m

The five most important species between 50 and 100 m in the region M4 were Merluccius merluccius, Trachurus trachurus, Spicara flexuosa, Illex coindetii, and Eledone moschata.

In the north-western Ionian Sea the biomass indices recorded for Merluccius merluccius ranged from 3.35 to 38.18 kg/km² while the density values were between 94 and 631 N/km². In the southwestern Adriatic waters the indices observed were between 10.42 and 48.57 kg/km² and between 93 and 829 N/km².

Trachurus trachurus was caught with average yields up to 27.03 kg/km² (7263 N/km²) in the Ionian Sea and up to 10.86 kg/km² (1536 N/km²) in the Adriatic.

Concerning the species Spicara flexuosa, the highest biomass index of 56.04 kg/km² and density of 3205 N/km² were recorded along the Ionian coast (sector 221b) while the highest values of 3.73 kg/km² and 145 N/km² were found in the Adriatic Sea (sector 221h).

The average abundance in weight of Illex coindetii ranged from 2.7 to 34.99 kg/km², corresponding to density from 15 to 1471 N/km², in the Adriatic sub-area and from zero to 10.91 kg/km² (257 N/km²) in the Ionian Sea.

Eledone moschata was caught with the greatest biomass and density indices of 18.65 kg/km² and 33 N/km² in the Ionian basin (sector 221a) and of 9.28 kg/km² and 54 N/km² in the Adriatic one (sector 221h).

Stratum 100-200 m

The five most important species for this depth stratum were Merluccius merluccius, Micromesistius poutassou, Trachurus trachurus, Lophius budegassa, and Illex coindetii.

For Merluccius merluccius the highest biomass index of 46.33 kg/km², with a density value of 5198 N/km², was obtained in the Ionian. In the southwestern Adriatic Sea the biomass and density indices were between 11.87 and 33.38 kg/km² and between 233 and 717 N/km², respectively.

Micromesistius poutassou was abundantly captured only in the Ionian Sea where the highest biomass index was 894.81 kg/km² and the density was 86221 N/km² (sector 221b).

Trachurus trachurus was caught with biomass indices between 1.05 and 75.95 kg/km² in the Ionian Sea and between 1.33 and 39.79 kg/km² in the Adriatic. The highest density values were 16371 N/km² in the former sub-area and 6127 N/km² in the latter.

Lophius budegassa was found with the highest biomass index of 25.94 kg/km² in the Ionian Sea (sector 221b) and of 21.8 kg/km² in the Adriatic Sea (sector 221e).

Illex coindetii was sampled with the highest biomass index of 89.39 kg/km² and density of 1102 N/km² in the Ionian Sea. The greatest values of biomass and density were 14.27 kg/km² and 878 N/km² in Adriatic.

Stratum 200-500 m

The five most important species in this depth range were Merluccius merluccius, Phycis blennoides, Galeus melastomus, Parapenaeus longirostris and Nephrops norvegicus.

Merluccius merluccius was captured with the highest biomass average value of 45.31 kg/km² in the southwestern Adriatic (sector 221e) and 37.99 kg/km² in the northwestern Ionian Sea (sector 221a).

Phycis blennoides was caught with the greatest biomass index (38.07 kg/km²) in the Adriatic Sea (sector 221e) and with the highest density index (2809 N/km²) in the Ionian (sector 221d).

The yields of Galeus melastomus were greater in the Adriatic than in the Ionian. In the former area the highest mean abundance indices were 30.19 kg/km² and 1111 N/km² while in the latter they were 9.63 kg/km² and 72 N/km².

The abundances of Parapenaeus longirostris were significantly greater in the Ionian than in Adriatic. The highest biomass and density indices were 23.40 kg/km² and 4133 N/km² respectively in the sector 221a (Ionian Sea) and 4.63 kg/km² and 387 N/km² respectively in the sector 221f (Adriatic Sea).

Nephrops norvegicus was caught with the highest biomass and density indices of 15.99 kg/km² and 537 N/km² respectively in Adriatic (sector 221f) and of 5.9 kg/km² and 368 N/km² respectively in the Ionian Sea (sector 221d).

Stratum 500-800 m

In this bathymetric stratum the five most important species for the M4 region were Galeus melastomus, Helicolenus dactylopterus, Phycis blennoides, Merluccius merluccius and Aristeus antennatus.

The species Galeus melastomus showed noteworthy average abundance indices both in Adriatic and in the Ionian Sea. In the former area the highest biomass and density values were 91.49 kg/km² and 402 N/km² respectively (sector 221e) while in the latter they were 43.5 kg/km² and 289 N/km² respectively (sector 221c).

Helicolenus dactylopterus was mainly caught in the southwestern Adriatic Sea, where the biomass indices ranged from 6.16 to 109.24 kg/km² and density values were between 24 and 465 N/km². The highest indices shown in the Ionian basin were 6.46 kg/km² and 62 N/km².

Also Phycis blennoides was mostly caught in the Adriatic Sea between 500 and 800 m. Its greatest biomass and density indices were 73.11 kg/km² and 477 N/km² respectively (sector 221f). The highest values observed in the Ionian Sea were 4.47 kg/km² (sector 221b) and 337 N/km² (sector 221d).

The catch of Merluccius merluccius in this depth stratum was exclusively represented by few and big specimens. The greatest biomass index of 22.68 kg/km² was recorded in Adriatic (sector 221h) while in the Ionian Sea the highest biomass average value was 2.15 kg/km² (sector 221d).

Aristeus antennatus was caught in all sectors of the Ionian Sea and only in the sector 221e and 221f of the Adriatic. In the Ionian basin the average yields in weight ranged from 0.18 to 26.27 kg/km² while the density values were between 10 and 1364 N/km². In the Adriatic the highest biomass and density indices were 8.38 kg/km² and 556 N/km², respectively.

Discussion and remarks

The results of the Medits-IT M4 1999 survey confirm previous observations on the geographic and bathymetric distribution of the fishery resources in the southwestern Adriatic and northwestern Ionian Sea. They point out the importance of some species in the M4 area, such as Merluccius merluccius on a wide depth range, Mullus barbatus in coastal waters and crustacean species in the upper slope, and confirm that recruitment represents the remarkable fraction of the catch for most of the species. Moreover, the present results stress the fluctuations in the abundance of many species from year to year.

Although Merluccius merluccius is confirmed to be widespread and abundant in the whole M4 area, a decrease of its yield has been shown in the last surveys (1994 = 24.11 kg/km²; 1995 = 24.96 kg/km²; 1996 = 24.95 kg/km²; 1997 = 22.82 kg/km²; 1998 = 18.20 kg/km²; 1999 = 14.56 kg/km²).

A marked increase of Micromesistius poutassou catch (22.18 kg/km²) respect to the 1994 survey (5.78 kg/km²) and the previous three years (1996 = 10.49 kg/km²; 1997 = 9.18 kg/km²; 1998 = 8.0 kg/km²) and comparable with the 1995 survey (20.22 kg/km²) has been observed. This fish alternates its highest biomass and density indices between the Ionian (1994, 1995 and 1999) and Adriatic Sea (1996, 1997 and 1998).

The highest abundance indices for Phycis blennoides related to the whole M4 area have been recorded in this last survey (6.13 kg/km²; 317 N/km²). Although its highest biomass was generally found in the southwestern Adriatic Sea, its density was sometime higher in the Ionian Sea, as shown in this last survey.

The greatest yield value for Helicolenus dactylopterus was found during 1995 survey (6.4 kg/km²). After this year the yield dropped to 1.9 kg/km² (1996) and exhibited an increasing trend until the last survey (2.02 in 1997 kg/km²; 4.3 in 1998 kg/km²; 5.39 kg/km² in 1999). Also in this fish, although the highest biomass values were always recorded in Adriatic Sea, the highest density indices were found in the Ionian waters during 1997 and 1999.

Lepidorhombus boscii was always caught with negligible biomass and density indices in the whole M4 study area. The values recorded in Adriatic were generally greater than in the Ionian.

The yield of Mullus barbatus related to the whole M4 area in this last survey (5.65 kg/km²; 592 N/km²) is comparable to that obtained in 1995 (5.33 kg/km²; 204 N/km²) and greater than all other years. Although the highest abundances of this fish have generally been found in the Ionian Sea, along the Sicilian and Calabrian coasts, the highest biomass and density indices have been recorded in the Adriatic Sea during the last survey.

Although the species Trachurus trachurus and Spicara flexuosa have a low commercial value, they assume importance in term of biomass and density mostly in the southernmost sectors of the Ionian Sea. In fact, noteworthy catches have been recorded each year as part of Medits project.

Concerning the crustacean species, Aristaeomorpha foliacea was found with very low yields throughout the Medits surveys while Aristeus antennatus was caught with fluctuating abundance indices, between 0.95 kg/km² (1995) and 4.65 kg/km² (1997). This shrimp is a typical resource of the Ionian Sea even though significant increases of its abundance may be found in the southernmost sector of Adriatic Sea in relation to eastward displacement, as shown in 1997.

Also Parapenaeus longirostris was collected with changing yields (between 2.23 kg/km² in 1996 and 5.2 kg/km² in 1998) and with highest biomass and density indices in the northwestern Ionian waters than in the southwestern ones.

The catches of Nephrops norvegicus in M4 area were rather comparable among the 6 Medits surveys and comprised between 1.26 kg/km² (1994) and 2.07 kg/km² (1996). This species is typically more abundant in the Adriatic sub-area than in the Ionian.

With regard to the cephalopod species, a decrease of the yield has been shown in Eledone cirrhosa (1.36 kg/km²) and an increase in Illex coindetii (9.15 kg/km²) during 1999 than the previous years, considering the whole M4 area. Both species alternate their greatest abundance in weight and number between the Adriatic and the Ionian Sea.