Survey Results for Greece - area G3: South Aegean Sea

by G. Tserpes, P. Peristeraki and N. Tsimenides

In the 60 hauls effected in the south Aegean Sea during the Medits GR '99 survey, 55 animal species out of the 59 target species were totally found. The majority was fishes, 7 were cephalopods and 5 were crustaceans. Abundance and biomass indices have been estimated and the summarized results are presented below.

In terms of biomass, expressed in kg/km² the highest indices were obtained for the following species:

§ Fishes: Squalus acanthias (37.46), Merluccius merluccius (36.53), Mullus barbatus (33.68), Raja clavata (29.66), Scyliorhinus canicula (24.62), Helicolenus dactylopterus (20.97), Lophius budegassa (19.25), Mullus surmuletus (18.75) and Argentina sphyraena (17.44).

§ Cephalopods: Illex coindetii (13.07).

§ Crustaceans: Parapenaeus longirostris (7.94) and Aristaeomorpha foliacea (7.03).

In terms of abundance, expressed in number of individuals/km² the highest indices were obtained for the following species:

§ Fishes: Mullus barbatus (9158), Mullus surmuletus (4721), Engraulis encrasicolus (4203), Argentina sphyraena (1770) and Spicara smaris (1344).

§ Cephalopods: Illex coindetii (500) and Sepia orbignyana (399).

§ Crustaceans: Parapenaeus longirostris (1991) and Aristaeomorpha foliacea (306).

Only four out of the 59 species of the reference list were not found in the South Aegean Sea: Eutrigla gurnardus, Raja asterias, Dicentrarchus labrax, and Penaeus kerathurus. From the above species, Eutrigla gurnardus and Dicentrarchus labrax were not also found during the 1998 survey.

A more detailed analysis of the results for the most abundant species, or species shown a remarkable differentiation with reference to the previous year, is given below.

Comments per species

Fish

Argentina sphyraena

Present in depths from 100-800 m in lower quantities than 1998. The overall density and biomass indices were 1770 N/km² and 17.44 kg/km² respectively. The highest indices were computed for the 200-500 zone (4567 N/km² and 45.93 kg/km²).

Aspitrigla cuculus

Present in depths between 100-500 m. The overall biomass index was 6.15 kg/km². The highest biomass values were found between 200-500 m (max. 13.92 kg/km²). Lengths ranged from 5 to 27cm.

Centrophorus granulosus

Present only in the 500-800 m zone. The density and biomass indices in this zone were 13 N/km² and 46.47 kg/km² respectively.

Diplodus annularis

Present in depths between 10-100 m. The overall density and biomass indices were 540 N/km² and 11.07 kg/km² respectively. The highest values were found between 10-50 m (135.21 kg/km², 6688 N/km²).

Engraulis encrasicolus

Present in depths between 10-200 m. The overall density and biomass indices were 4203 N/km² and 7.65 kg/km² respectively. The highest values were found between 10-50 m (88.01 kg/km², 53021 N/km²).

Galeus melastomus

Found from 100 to 800 m. The biomass index was 11.32 kg/km² and the maximum value was computed for the 500-800 zone (27.72 kg/km²). The lengths ranged from 15 to 51cm.

Helicolenus dactylopterus

Found between 100-800 m. Overall abundance and biomass indices were 178 N/km² and 20.97 kg/km² respectively. The highest values were computed for the 500-800 m zone (318 N/km², 45.69 kg/km²⁾. The lengths ranged from 3 to 31cm.

Lepidotrigla cavillone

Present in depths between 10-500 m. The overall density and biomass indices were 678 N/km² and 8.56 kg/km² respectively. The highest values were found between 50-100 m (38.84 kg/km², 3988 N/km²).

Lophius budegassa

Found from 50 to 800 m. High biomass index was observed (19.25 kg/km²) and the maximum value was computed for the 200-500 zone (32.99 kg/km²). The lengths ranged from 9 to 71cm.

Merluccius merluccius

Present in almost all depth zones (50-800 m). It had one of the highest abundance indices in terms of biomass (36.53 kg/km²). The highest indices were found in depths between 100-800 m and the maximum ones were computed for the 500-800 m zone in terms of biomass (62.1 kg/km²) and the 200-500 m zone in terms of abundance (480 N/km²). The lengths ranged from 5 to 69cm.

Mullus barbatus

Present from 10 to 500 m. The overall abundance and biomass indices were 9158 N/km² and 33.68 kg/km² respectively, notable higher comparing with the ones of 1997 and 1998. The highest values were obtained at the 0-50 m zone (113895 N/km², 341.95 kg/km²). The lengths ranged from 4 to 22cm. The zone 10-50 m seems to operate as a nursery ground in specific areas, as 96% of the specimens caught in this zone were of lengths 4 to 6cm.

Mullus surmuletus

Present in almost all bathymetric zones (10-500 m). The overall abundance and biomass indices were 4721 N/km² and 18.75 kg/km² respectively. The highest indices were obtained for the 10- 50 m zone (59198 N/km², 184.96 kg/km²). The lengths ranged from 5 to 30cm. The zone 10-50 m seems to operate as a nursery ground in specific areas as the length of most specimens (99%) caught in this zone ranged from 5 to 10cm.

Pagellus acarne

Present from 10 to 500 m. In 1998 the overall abundance and biomass indices were of the highest ones, 1814N/km² and 26.93kg/km² respectively, while in 1999 a significant decrease was observed in the overall indices (205 N/km² and 3.51 kg/km²). The highest index was computed for the 10-50 m zone (1542 N/km², 17.54 kg/km²). The lengths ranged from 6 to 22cm. All the specimens found in the 10-50 m zone were smaller than 15cm.

Pagellus bogaraveo

Found in the 100-800 m zone in quantities lower than the ones of 1998. The overall abundance and biomass indices were 61 N/km² and 6.35 kg/km² respectively. The highest values were observed at the zone 500-800 m (10.35 kg/km², 95 N/km²). Lengths ranged from 13 to 26cm.

Pagellus erythrinus

Present from 10 to 500 m. The overall abundance and biomass indices were 161 N/km² and 8.91 kg/km² respectively, lower than the previous year. The highest indices were computed for the 10-50 m zone (60.48 kg/km², 1261N/km²). The lengths ranged from 9 to 28cm.

Raja clavata

Present in depths 50 to 800 m at high biomass values. The overall abundance and biomass indices were 77 N/km² and 29.66 kg/km² respectively, both lower than the previous year. The lengths of specimens ranged between 13-68cm.

Scyliorhinus canicula

Present in all depth zones. The overall density and biomass indices were 228 N/km² and 24.62 kg/km² respectively. The lengths ranged from 11 to 51cm.

Serranus cabrilla

Present in depths from 10-200 m. The overall density and biomass indices were 235 N/km² and 7.64 kg/km² respectively. In the 10-50 zone had the highest density and biomass indices (2007 N/km², 58.51 kg/km²).

Spicara smaris

Present in depths from 10-200 m. The overall density and biomass indices were 1344 N/km² and 13.16 kg/km² respectively, lower than 1998. In the 100-200 zone had the highest density and biomass indices (5200 N/km², 49.58 kg/km²). The lengths ranged from 4 to 18cm.

Squalus acanthias

Present in all depth zones over 50 m but most commonly found in the 200-500 zone. The overall density and biomass indices were 77 N/km² and 37.46 kg/km² respectively, significantly lower than the ones of 1998. In the 200-500 zone had the highest indices (223 N/km², 90.18 kg/km²).

Crustaceans

Aristaeomorpha foliacea

Found in considerable high quantities only between 500-800 m (862 N/km², 19.8 kg/km²). The lengths of individuals ranged from 19 to 60 mm.

Parapenaeus longirostris

Highly abundant by means of number (1991 N/km²). Present from 50 to 800 m. The highest values were obtained at the zone 200-500 (4091 N/km², 17.96 kg/km²). The lengths ranged from 9 to 33mm.

Cephalopods

Eledone moschata

Present at depths down to 200 m. The overall density and biomass indices were 68 N/km² and 6.32 kg/km² respectively. In the zone 50-100 m the highest indices (582 N/km², 35.3 kg/km²) were obtained. The lengths ranged from 2 to 8cm.

Illex coindetii

Present in all bathymetric zones, but mostly abundant between 100-500 m. It was the most abundant cephalopod among the target species (13.07 kg/km², 500 N/km²). The highest abundance index by means of biomass was computed for the 200-500 m zone (31.59 kg/km²), while most abundant by means of density was at the zone 100-200 m (1201 N/km²). The lengths ranged from 3 to 20cm.

Sepia officinalis

Present at depths down to 200 m. Mainly found from 10-50 m where the highest indices (611 N/km², 43.75 kg/km²) were obtained. The lengths ranged from 4 to 20cm.

Sepia orbignyana

Present in depths from 100-500 m. The overall density and biomass indices were 399 N/km² and 7.05 kg/km² respectively. In the 200-500 m zone had the highest density and biomass indices (820 N/km², 15.29 kg/km²).

Comments per stratum

Stratum 10-50 m

Twenty-five out of the 59 target species were found in this depth zone. Twenty of them were fishes and 5 cephalopods.

This stratum is characterized by the presence in high numbers of the two members of the Mullidae family (Mullus surmuletus and Mullus barbatus), as well as Sparus pagrus. All the above species were found in densities higher than 10000 N/km² and Mullus surmuletus and Mullus barbatus exceeded 50000 N/km².

The 0-50 m zone operates in most cases as a nursery ground for the members of the Mullidae and Sparidae families. The aforementioned species with the addition of Diplodus annularis and Engraulis encrasicolus were also the most abundant in terms of weight. The highest biomass index was obtained for Mullus barbatus (341.95).

Among cephalopods the most common species were Sepia officinalis and Eledone moschata.

Stratum 50-100 m

Thirty-four out of the 59 target species were found in this depth zone. Twenty-eight of them were fishes, 5 were cephalopods and one crustacean.

In this stratum the most abundant species in terms of number were Lepidotrigla cavillone, Spicara flexuosa, Loligo vulgaris, Spicara smaris, Mullus barbatus and Pagellus acarne. Lepidotrigla cavillone had the highest index, which reached up to 3988 N/km².

Mullus barbatus and Scyliorhinus canicula had the highest indices in terms of biomass, which exceeded the 40 kg/km². The next more abundant species in terms of biomass were Lepidotrigla cavillone, Spicara flexuosa and Spicara smaris.

The most common cephalopod species of the zone was Eledone moschata (582 N/km², 35.3 kg/km²) and Loligo vulgaris by means of density (2213 N/km²).

Stratum 100-200 m

Forty-three out of the 59 target species were found in this depth zone. Thirty-four of them were fishes, 7 were cephalopods and 2 were crustaceans.

In this stratum Spicara smaris was the most abundant species in terms of number and its density reached up to 5200 N/km². Other abundant species among fishes were Argentina sphyraena (2047 N/km²), and Lepidotrigla cavillone (1878 N/km²).

In terms of biomass the most abundant species was Raja clavata (59.04 kg/km²) followed by Spicara smaris (49.58 kg/km²) and Scyliorhinus canicula (38.5 kg/km²).

The most common cephalopod species of the zone were Illex coindetii (1201 N/km², 15.4 kg/km²) and Sepia orbignyana (766 N/km², 12.4 kg/km²).

The most abundant species of crustaceans of the zone was Parapenaeus longirostris (2734 N/km², 7.07 kg/km²).

Stratum 200-500 m

Thirty-four out of the 59 target species were found in this depth zone. Twenty-eight of them were fishes, 4 were cephalopods and 2 were crustaceans.

The species with the highest biomass index were: Squalus acanthias (90.18 kg/km²), Raja clavata (47.34 kg/km²), Argentina sphyraena (45.93 kg/km²), Scyliorhinus canicula (41.67 kg/km²), Merluccius merluccius (33.2 kg/km²), Lophius budegassa (32.99 kg/km²) and Illex coindetii (31.59 kg/km²)

The species with the higher abundance in terms of number were Argentina sphyraena (4567 N/km²), Parapenaeus longirostris (4091 N/km²), Sepia orbignyana (820 N/km²) and Illex coindetii (818 N/km²).

Stratum 500-800 m

Twenty out of the 59 target species were found in this depth zone. Fifteen of them were fishes, 1 was cephalopod and 4 were crustaceans.

The most abundant species in terms of number were Aristaeomorpha foliacea (862 N/km²), Parapenaeus longirostris (638 N/km²), Helicolenus dactylopterus (318 N/km²), and Merluccius merluccius (232 N/km²).

In terms of weight the most abundant species were Merluccius merluccius (62.1 kg/km²), Centrophorus granulosus (46.47 kg/km²), Helicolenus dactylopterus (45.69 kg/km²) and Galeus melastomus (27.72 kg/km²).

Aristaeomorpha foliacea characterizes the stratum as it is exclusively found in this depth zone.

Discussion

The most remarkable difference between 1998 and 1999 is an important decrease of the overall biomass index for the following species: Pagellus acarne (1998: 26.3 kg/km², 1999: 3.51 kg/km²), Lepidopus caudatus (1998: 21.32 kg/km², 1999: 4.95 kg/km²), Squalus acanthias (1998: 62.63 kg/km², 1999: 37.46 kg/km²), and Aristaeomorpha foliacea (1998: 17.51 kg/km², 1999: 7.03 kg/km²).

On the contrary, a notable increase of the overall biomass index was observed for the species Mullus barbatus (1998: 18.71 kg/km², 1999: 33.68 kg/km²).