Survey Results for Italy - area M4 - Part 1: SW Adriatic and NW Ionian Seas
* LBMB, Bari, Italy
** IZAC, Bari, Italy
Below is a report on Medits-IT 1997 survey results, referring to south-western Adriatic and north-western Ionian Sea (M4 region, strata 22101-22140).
In the sampled area (28793 kmē) 146 hauls were taken by the fishing vessel "Biancamaria".
During Medits-IT M4 1997 the most abundant species in weight ( kg/kmē) over the whole M4 area, were Merluccius merluccius (mean value 22.82 kg/kmē), Trachurus trachurus (24.72 kg/kmē), Micromesistius poutassou (9.18 kg/kmē), Lophius piscatorius (6.09 kg/kmē), Eledone cirrhosa (4.82 kg/kmē), Aristeus antennatus (4.65 kg/kmē), Parapenaeus longirostris (3.35 kg/kmē); the highest numerical abundance ( Ind/kmē) were provided by Trachurus trachurus (mean value 3361 Ind/kmē), Parapenaeus longirostris (552 Ind/kmē), Micromesistius poutassou (435 Ind/kmē), Merluccius merluccius (303 Ind/kmē), Aristeus antennatus (213 Ind/kmē), Trachurus mediterraneus (158 Ind/kmē).
Also Medits-IT M4 1997 data show a different distribution and abundance of the same resources in relation to geographic areas (south-western Adriatic Sea, north-western Ionian Sea) and to the chosen bathymetric strata. For example, Eledone cirrhosa was mainly distributed in the Ionian Sea within 100 m of depth; Helicolenus dactylopterus in Adriatic Sea between 500 m and 800 m; Mullus barbatus, Pagellus erythrinus and Spicara flexuosa in the Ionian Sea within 200 m of depth; Micromesistius poutassou and Phycis blennoides in Adriatic Sea at depth greater than 200 m; Parapenaeus longirostris in the Ionian Sea on a wide depth range; Aristeus antennatus was distributed in all sectors of the Ionian Sea between 500 m and 800 m depth and was abundantly caught between 200 and 800 m in the southernmost sector of Adriatic Sea.
Trachurus trachurus was caught in both areas, with highest abundance between 50 and 200 m; Nephrops norvegicus down to 50 and 100 m in Adriatic and Ionian respectively; Lophius budegassa and Lophius piscatorius were found in both areas across a wide depth range; Merluccius merluccius is confirmed, once a time, to be widespread and abundant in the whole M4 area and thus the most important demersal resource.
Not found at all.
This species was caught mainly on the continental shelf with very low abundance indexes.
Helicolenus dactylopterus was mainly fished at depths greater than 100 m; abundance indexes were higher in Adriatic Sea, between 500 m and 800 m depth. The highest biomass value (58.46 kg/kmē) was observed in sector 221g. The highest mean density (1003 Ind/kmē) was found between 100 and 200 m in Ionian Sea (sector 221c).
This species was caught beyond 100 m of depth with negligible yield and density. The average abundance index for the whole M4 area was 0.28 kg/kmē.
Lophius budegassa was mainly fished at depths greater than 50 m, the highest abundance index (27.06 kg/ kmē) was observed between 100 and 200 m in the southernmost sector of the Adriatic Sea (sector 221e). The density values ranged from 3 to 65 Ind/kmē.
This species was found across the whole depth range investigated with abundance indexes ranged from 0.29 kg/kmē to 100.85 kg/kmē in the Medits-IT M4 area.
Generally abundant in the whole area, mainly between 50 and 500 m. In this depth zone density ranged from 15/kmē to 1650 Ind/kmē. The highest abundance of 80.34 kg/kmē was observed in the southernmost Adriatic area (sector 221e). A dominance of juveniles (<20 cm) was observed in the catches down to 500 m of depth with the highest concentration between 50 m and 200 m.
The species was found to be abundant mostly between 100 and 200 m with the highest mean abundance (103.32 kg/kmē) and density (6678 Ind/kmē) in Adriatic Sea (sector 221e). The lengths of recruits ranged from 8 cm to 15 cm.
This species was caught almost exclusively on the continental shelf (<200 m). The highest abundances in weight and number were found in the southern side of the Ionian Sea (Sicilian and Calabrian coasts), whereas the catches were negligible in the southern Adriatic Sea. The majority of specimens had a length between 10 and 15 cm.
Mullus surmuletus was caught across the whole depth range investigated. The highest biomass and density indexes were respectively 6.91 kg/kmē, between 200 and 500 m, and 53 Ind/kmē, in 100-200 m.
This species was found within 500 m, with low abundance. The noteworthy abundance of 59.34 kg/kmē and 6211 Ind/kmē was found along the Sicilian coast (sector 221a).
Few specimens of this species were fished in the deepest zone beyond 200 m.
This species was found only on the continental shelf (10-200 m) and mainly in the Sicilian waters where was recorded the highest abundance (17.17 kg/kmē) and density (296 Ind/kmē).
It was generally found beyond 200 m of depth exhibiting the highest abundance (37.97 kg/kmē, 2250 Ind/kmē) between 200 and 500 m, in the southern Adriatic Sea. Most of the specimens fished were smaller than 20 cm.
This species was found with few specimens in the 221h Adriatic sector.
It was not fished at all.
The species was found down to 200 m. The highest abundance index (58.50 kg/kmē) and density (3499 kg/kmē) were observed in the first depth zone of the southernmost area of the Ionian Sea. The size of the specimens ranged generally from 10 to 20 cm.
This species was fished on the continental shelf (<200 m) but abundance in weight and number was noteworthy only in the southern area of the Ionian Sea. The highest values of 207.66 kg/kmē and 12432 Ind/kmē were shown in the 221b sector. The catches were almost exclusively made up of juveniles.
This species was caught as far as 500 of depth exhibiting the highest yields and densities within 200 m. The highest abundance index and density were 177.98 kg/kmē (sector 221b) and 17233 Ind/kmē (sector 221c) in the Ionian Sea and 118.35 kg/kmē (sector 221e) and 22596 Ind/kmē (sector 221e) in Adriatic. Juveniles were dominant in the catches.
The highest yields and densities were found between 100-200 m: 8.50 kg/kmē and 595 Ind/kmē respectively.
This species was found to be rare in the whole area. The highest value of 28.22 kg/kmē and 39 Ind/kmē were obtained between 100 and 200 m in the Ionian Sea.
It was caught beyond 200 m of depth. Its yields in weight and number were rather low. The highest abundance of 1.90 kg/kmē and 571 Ind/kmē was found in the Ionian Sea (sector 221b).
The species was mainly fished in the deepest water of the southernmost sector of both Ionian and Adriatic Sea. In this latter area a surprisingly catch was carried out. The abundance in weight and number were 76.00 kg/kmē and 2912 Ind/kmē respectively.
The species was caught in the whole depth range investigated. The highest yield (15.07 kg/kmē) was observed between 200 and 500 m in the Adriatic sub-region (221f). Most carapace lengths ranged from 20 to 40 mm.
This species was generally caught at depth greater than 50 m and mainly between 200 and 500 m in the Ionian sub-region. It exhibited the highest abundance (48.05 kg/kmē) along the Calabrian coast (sector 221b).
It was fished as far as 500 m of depth. The highest yields were observed in the Ionian Sea. The highest abundance index was 28.69 kg/kmē (sector 221c).
Most mantle lengths ranged from 6 to 15 cm.
This cephalopod was almost exclusively caught within 100 m of depth with negligible abundance in weight and number.
This species was caught across the whole investigated area, with the highest density between 50 and 200 m depth. It was 264 Ind/kmē in the Ionian Sea (sector 221c) and 292 Ind/kmē in Adriatic (sector 221e).
It was fished almost exclusively in the southern Adriatic sub-region with low abundance indexes.
This species was found in a wide depth range (<500 m) in both sub-regions. However, the highest abundance indexes were within the first 100 m (54.44 kg/kmē at 50-100 m in 221b sector). Very low values of density were observed.
Not found at all during 1997 survey.
In this first stratum the 5 most important species were Merluccius merluccius, Spicara flexuosa, Trachurus mediterraneus, Trachurus trachurus and Octopus vulgaris.
During Medits-IT 1997 the highest abundance indexes of Merluccius merluccius estimated for the two main subregions of M4 were 51.92 kg/kmē for the north-western Ionian and 9.51 kg/kmē for the south-western Adriatic Sea.
Spicara flexuosa was abundantly caught in the southernmost sectors of Ionian. The indexes of abundance were 58.50 kg/kmē in the Sicilian side (sector 221a) and 24.48 kg/kmē for the Calabrian coast (sector 221c). In the south-western Adriatic the species was fished with the highest yield of 1.53 kg/kmē.
Trachurus mediterraneus showed the surprisingly abundance index of 207.66 kg/kmē with 12432 Ind/kmē along the Calabrian coast (sector 221b).
The abundance index of Trachurus trachurus ranged from 12.85 kg/kmē and 81.51 kg/kmē in the north-western Ionian Sea whereas in south-western Adriatic the species was caught with the highest yield of 8.76 kg/kmē.
The highest abundance of Octopus vulgaris was found in the northernmost sector (221d) of the Ionian Sea (34.61 kg/kmē).
The 5 most important species between 50 and 100 m in the region M4 were Merluccius merluccius, Mullus barbatus, Trachurus trachurus, Eledone cirrhosa and Octopus vulgaris.
Merluccius merluccius abundance indexes recorded in the north-western Ionian ranged from 4.01 kg/kmē to 74.61 kg/kmē. The yields observed in the south-western Adriatic were between 5.84 kg/kmē and 80.34 kg/kmē.
Mullus barbatus was only caught with noteworthy yields in the southernmost sectors of the Ionian Sea (23.69 kg/kmē in sector 221a, 21.78 kg/kmē in sector 221b).
The species Trachurus trachurus was abundantly found in M4 area; along the Ionian coast (sector 221b) was recorded the index of 177.98 kg/kmē while in the Adriatic (sector 221e) it was 110.63 kg/kmē.
Eledone cirrhosa was almost exclusively found in the Ionian Sea with the highest yield of 28.69 kg/kmē (sector 221c).
Also Octopus vulgaris was only caught with noteworthy yields in the Ionian areas, where the highest value was 54.44 kg/kmē (sector 221b).
The 5 most important species for this depth stratum were Merluccius merluccius, Micromesistius poutassou, Trachurus trachurus, Eledone cirrhosa and Illex coindetii.
Merluccius merluccius presented noteworthy abundance indexes in almost all sectors of region M4. The highest value (74.76 kg/kmē) was obtained in the southernmost sector of Adriatic Sea. In the Ionian the abundance indexes ranged from 14.95 kg/kmē (sector 221d) to 63.69 kg/kmē (sector 221a). In the south-western Adriatic Sea the yields were between 12.04 kg/kmē (sector 221g) and the above reported value.
Also Micromesistius poutassou was found with high abundance (103.32 kg/kmē) and density (6678 Ind/kmē) in the sector 221e of the Adriatic Sea. In the Ionian Sea the highest abundance index and density were 22.72 kg/kmē and 1597 Ind/kmē respectively (sector 221c).
Trachurus trachurus was fished with abundance indexes between 14.99 and 158.67 kg/kmē in the Ionian Sea while the yields were between 18.99 and 118.35 kg/kmē in the Adriatic. The highest density corresponded to the value of 22596/kmē and was observed in the latter sub-area.
Eledone cirrhosa was found with the highest abundance index of 11.66 kg/kmē (sector 221b) in the Ionian Sea and 17.17 kg/kmē (sector 221f) in Adriatic.
Illex coindetii was mainly caught in the Ionian Sea exhibiting the maximum average index of 31.13 kg/kmē (sector 221c).
The 5 most important species for this depth range, according to the yields obtained during the national survey, were Merluccius merluccius, Micromesistius poutassou, Phycis blennoides, Parapenaeus longirostris and Nephrops norvegicus.
Merluccius merluccius was fished in almost all districts of M4 area; in the north-western Ionian Sea its abundance ranged from 5.97 kg/kmē to 50.19 kg/kmē. In the south-western Adriatic the maximum yield in weight was 57.29 kg/kmē (sector 221e). The highest mean density was 1646 Ind/kmē (sector 221h).
Micromesistius poutassou was mainly caught in the Adriatic Sea with the highest values of 47.48 kg/kmē and 2231 Ind/kmē (sector 221h).
Also the yields of Phycis blennoides were greater in Adriatic than in Ionian. In fact, in the south-western Adriatic the highest index of abundance was 37.97 kg/kmē (sector f) while in the north-western Ionian Sea it was 3.75 kg/kmē (sector d).
The yields of Parapenaeus longirostris were significantly higher in Ionian than in Adriatic. They ranged from 7.29 kg/kmē (1349 Ind/kmē) (sector a) to 48.05 kg/kmē (9225 Ind/kmē) (sector b) in the north-western Ionian Sea. In Adriatic the maximum value of abundance and density were 5.64 kg/kmē and 369 Ind/kmē (sector 221e) respectively.
Nephrops norvegicus was mostly caught in Adriatic sectors with the highest biomass index of 15.07 kg/kmē and density of 1219 Ind/kmē (sector 221f).
In this bathymetric stratum the 5 most important species for the M4 region were Aristeus antennatus, Merluccius merluccius, Helicolenus dactylopterus, Micromesistius poutassou and Phycis blennoides.
Aristeus antennatus was fished in all sectors of the Ionian Sea and for the first time with the highest abundance (76.00 kg/kmē) and density (2912 Ind/kmē) in the southernmost sector of Adriatic Sea which would represent the northernmost area of distribution for this shrimp. In the Ionian the abundance in weight ranged from 7.99 kg/kmē and 24.34 kg/kmē, the abundance in number was between 299 Ind/kmē and 1659 Ind/kmē.
Merluccius merluccius was mainly fished in the south-western Adriatic Sea, where the highest index (31.93 kg/kmē) was recorded in the sector h. In the north-western Ionian the biomass indexes ranged from 0.00 kg/kmē to 8.47 kg/kmē.
Helicolenus dactylopterus too was mainly caught in the south-western Adriatic Sea, where the abundance indexes ranged from 6.72 kg/kmē to 58.46 kg/kmē.
Micromesistius poutassou provided yields ranging from 0.00 kg/kmē to 2.24 kg/kmē in the Ionian Sea and from 2.76 kg/kmē to 15.43 kg/kmē in Adriatic waters.
The abundance of Phycis blennoides was between 0.98 kg/kmē and 3.85 kg/kmē in the Ionian Sea and between 0.00 kg/kmē and 21.98 kg/kmē in Adriatic.
The data (yields in kg/kmē and Ind/kmē, length-frequency distributions) collected during Medits-IT M4 1997 survey are compared with those of Medits-IT M4 1996 one.
The length-frequency distributions, for sectors and bathymetric strata, are relative to the most abundant species in the investigated area.
Not found at all in both surveys.
This species exhibited very low converging abundance indexes in both surveys: 0.04 kg/kmē and 6 Ind/kmē during 1997 and 0.04 kg/kmē and 8 Ind/kmē during 1996.
This species showed comparable abundance indexes and densities for the whole study area. The average values of 2.02 kg/kmē and 47 Ind/kmē were obtained in 1997; the mean indexes of 1.90 kg/kmē and 39 Ind/kmē were shown in 1996.
Although for negligible yields, this species exhibited lowest abundance index in 1997 data (0.28 kg/kmē) respect to those obtained during 1996 Medits-IT (0.68 kg/kmē).
Both abundance in weight and number of this fish was lower in the last survey. In fact, the former came out as 5.67 kg/kmē in 1996 and 2.71 kg/kmē during 1997 cruise, the latter was 30 Ind/kmē in 1996 and 12 kg/kmē in 1997.
The average yield of Lophius piscatorius obtained during the 1997 research (6.09 kg/kmē) was higher than 1996 survey (2.15 kg/kmē).
Merluccius merluccius is the most widespread and abundant demersal species in M4 area. No definite trend was detected by depth and geographic area. In fact, the average yield for the whole region was 22.82 kg/kmē in 1997, 24.95 kg/kmē during 1996 and 24.96 kg/kmē in 1995.
For this species a slight decrease in abundance was yielded. During this year the yield in weight and density were 9.18 kg/kmē and 435 Ind/kmē respectively whereas they were 10.49 kg/kmē and 746 Ind/kmē respectively during 1996.
For this species a significant decrease in abundance was shown. Both yields in weight (1.78 kg/kmē) and density (49 Ind/kmē) in the 1997 research were lower than those obtained during 1996 for which abundance index was 3.09 kg/kmē and density 169 Ind/kmē.
This species presented very low and comparable values of abundance between the years: 1.05 kg/kmē and 12 Ind/kmē during 1996; 0.80 kg/kmē and 9 Ind/kmē in 1997.
An increase in the catch was shown in the 1997 survey.
This species was found to be rare in the investigated area during both trawl surveys of Medits-IT M4.
This species was found to be occasionally in both surveys of Medits-IT M4; the yield found in 1997 (0.65 kg/kmē) was barely higher than that obtained during 1996 (0.34 kg/kmē).
This species was not found in both years of Medits-IT M4.
This species presented comparable values during the 1996 research (2.34 kg/kmē and 83 Ind/kmē) and in 1997 Medits-IT survey (2.45 kg/kmē and 83 Ind/kmē).
This species was never found in the north-western Ionian and only occasionally in the south-western Adriatic in both years.
This species was not caught during Medits-IT M4 of both years.
This species were found with comparable yields between the 1997 research (1.91 kg/kmē and 79 Ind/kmē) and 1996 Medits-IT M4 (1.50 kg/kmē and 66 Ind/kmē).
This species exhibited significant increase in the abundance indexes between the two surveys: 0.98 kg/kmē and 27 Ind/kmē in the 1996 cruise; 3.22 kg/kmē and 158 Ind/kmē in the 1997 one.
An increase of the average abundance in weight and number during 1997 survey (24.72 kg/kmē, 3361 Ind/kmē) respect to that obtained during 1996 (17.86 kg/kmē, 2428 Ind/kmē) was shown.
For this species a decrease of the biomass and density was recorded during 1997. The abundance indexes were 2.84 kg/kmē and 589 Ind/kmē within the 1996 trawl survey and 1.02 kg/kmē and 86 Ind/kmē during 1997 Medits-IT M4.
This species was occasionally fished in both research years.
For this species the yields obtained in the two research surveys were somewhat negligible and presented the same magnitude (0.36 kg/kmē in 1996 survey and 0.21 kg/kmē in 1997).
The yield in weight and number for this crustacean was higher in 1997 survey (4.65 kg/kmē and 213 Ind/kmē) than in 1996 (2.54 kg/kmē and 147 Ind/kmē). A significant increase of the abundance in the southernmost sector of Adriatic Sea was observed in 1997. This was due to the eastwards migration of this species, particularly abundant in the Ionian Sea.
The comparison of the yields for the two Medits-IT M4 surveys showed for this species barely lower abundance values in the last survey: 1.47 kg/kmē during 1997 and 2.07 kg/kmē in 1996.
The yields in weight and number obtained during 1997 (3.35 kg/kmē and 552 Ind/kmē) were slightly higher than those found in 1996 (2.23 kg/kmē and 419 Ind/kmē).
An increase in abundance was shown. While during 1996 research for the whole M4 region values of abundance as 2.57 kg/kmē and 12 Ind/kmē were estimated, during 1997 Medits-IT the abundance indexes came out 4.82 kg/kmē and 22 Ind/kmē.
This species was caught with low yields in both surveys. A comparable values were found, however, in the abundance indexes during 1997 and 1996: 2.25 kg/kmē in the former and 3.00 kg/kmē in the latter.
This species was mainly fished in Adriatic with negligible yields during both years.
An increase in weight was observed during 1997 in both north-western Ionian and south-western Adriatic Sea: the value of 2.21 kg/kmē was estimated within 1996 cruise and 2.89 kg/kmē in the context of 1997 survey.
Not found at all during 1996, just very few specimens were caught in 1997.
Apart from some numerical differences by strata between the two surveys, the structure of hake population came out overlapped. The Medits net caught, from 10 m to 500 m depth, a high percentage of 6-15 cm specimens (modal value about 10-12 cm). During both surveys larger specimens than 35-40 cm were mainly caught below 450-500 m depth.
During 1997 the fraction of juveniles (<12 cm) was more abundant in the south-western Adriatic Sea than in the Ionian.
This species exhibited most numerous size classes between 8 and 15 cm during both surveys. These specimens were mostly caught between 100 and 200 m. Larger specimens, whose sizes were between 20 and 35 cm, were generally found in 200-500 m depth stratum.
The length-frequency distributions of Mullus barbatus did not show significant differences between the surveys. The lengths mainly ranged from 10 to 20 cm. A slight increase in size according to depth was observed.
The catch in number was higher in the Ionian sub-region.
Although a wide range of sizes up to 61 cm was shown, the bulk of stock in both sub-regions was made up of specimens smaller than 15 cm. These specimens were mostly caught on the deepest bottoms.
No significant differences were observed between the size composition of 1997 and 1996 Medits-IT surveys.
The sizes of this fish ranged from 6 to 35 cm. The majority of individuals had a length between 10 and 20 cm and were mainly caught within 100 m of depth.
There was no differences between the two years.
A wide range of sizes was mainly shown in the Ionian Sea where the smallest (9 mm) and largest (75 mm) carapace length were found. However, the stock in both sub-regions was constituted by individuals whose sizes were between 20 and 40 mm as observed in the previous year.
Size-frequency distributions of this shrimp in the Ionian Sea were comparable to those of 1996. The carapace lengths ranged from 16 to 66 mm and the most abundant fraction of the sampled population had a size between 20 and 45 mm.
As before reported, a large amount of individuals was caught in Adriatic Sea for the first time during 1997 in relation to migration phenomenon.
The sizes of these specimens were between 21 and 56 mm carapace length, with the majority comprised between 35 and 50 mm.
This shrimps was mainly caught in the Ionian Sea where the sizes ranged from 8 to 40 mm carapace length. The bulk of stock in this area was between 10 and 30 mm, an increase of the average size according to depth was shown.
In Adriatic Sea the sampled population exhibited sizes between 21 and 42 mm carapace length.
No significant differences between the 1996 and 1997 surveys were shown.
The length-frequency distributions of Eledone cirrhosa were comparable between the two surveys. The sizes mainly ranged from 6 to 15 cm mantle length. Juveniles (<5 cm mantle length) were found in both Ionian and Adriatic Sea.
A comprehensive analysis of Medits-IT M4 1997 generally confirms the Medits-IT M4 1996 data relative to the bathymetric and geographic distribution of demersal resources. The significant difference is the abundant presence of Aristeus antennatus in the southernmost sector of Adriatic Sea, neighbouring the Ionian, during 1997. In our opinion, this was the consequence of an eastwards migration of the stock, confirmed also by local fishermen.
Some differences in the abundance indexes and densities were recorded between the areas and years. Concerning the areas, in Adriatic Sea some species, such as Micromesistius poutassou, Phycis blennoides and Helicolenus dactylopterus, were found more abundant than in Ionian during 1997. Some other species, such as Mullus barbatus and Parapenaeus longirostris, were mostly caught in the Ionian Sea.
With regard to the years, a decrease in abundance for Mullus barbatus and Trisopterus minutus capelanus was shown, while an increase for Trachurus trachurus, Trachurus mediterraneus, Aristeus antennatus and Eledone cirrhosa was detected.
Generally speaking, the two years produced quite closely results regarding the length-frequency distributions of the most important demersal species, confirming that recruitment represents the remarkable fraction in the catch of most of them.