Rapp. Comm. int. Mer Médit., 36,2001
308
Introduction
The swordfish is one of the commercially important fish species in the
Turkish waters. It is caught by longlines, gill nets and harpoons (1). Tokac
et al. (2) studied the swordfish fishery in the North Aegean Sea, but did not
give information on the driftnets. At present, some 50-60 fishing vessels
are known to use driftnets for swordfish in the Turkish Aegean Sea.
Dolphins are considered as globally threatened species in spite of some
national and international protection measures. In the Mediterranean, one
of the threats is the driftnet due to its non-selectivity, i.e. it entangles any
species which are larger than the mesh size (3, 4). In the Aegean Sea, the
swordfish driftnet fishery is a relatively new problem for cetaceans and
very little studied (5, 6). Thus the aim of our study is to collect basic data
and accurate information on the swordfish driftnet fishery and dolphin
bycatches in the Turkish Aegean Sea, so that more effective protection
measures can be implemented.
Materials and Methods
Monitoring of the bycatch was made on five vessels of 9-14 m in length,
in May and June, 1999 and 2000, in the Aegean Sea coast of Turkey,
between Marmaris and Fethiye (Fig. 1). The details of fishing trips were
recorded and all the bycatches were examined for species, sex and body
length.
Fig.1. The study area for the swordfish driftnet fishery in the Turkish
coast of the Aegean Sea
Results and Discussion
Driftnets are set at 18-20 hrs and retrieved at 4-5 hrs in the next morning.
The fishing season lasts only two months, May and June. Mesh size of the
driftnet used for the swo
r
d
fish is 240-260 mm and the net is made of ny
l
o
n
p
o
l
y
filament. The total length of the net is 1000 -1500 m on average and the
depth is 4 m. In both 1999 and 2000, 20 boats were counted as operating
s
wo
r
d
fish driftnet fishery in Fethiye - Marmaris area. The fishing areas were
300- 2500 m deep and 5-9 nmiles from the coasts. The driftnet is set in the
depth of 6-7 m in general.
Table 1 shows the list of dolphins incidentally caught by the swordfish
driftnet. In 1999 and 2000, 10 and 9 dolphins were caught, respectively.
Table 1. The species, sex, and body length (BL) of the dolphins inciden-
tally caught in the swordfish driftnets in the Agean Sea.
These data showed that S. coeruleoalba, T. truncatusand G. griseusw
e
r
e
bycatch dolphin species in the swo
r
d
fish driftnet fishery and S
.c
o
e
r
u
l
e
o
a
l-
b
awas the most in?uenced species of all. These three species are shown as
being under the impact of driftnet fishery in the Mediterranean (4). Our
result also re?ects the fact that the most common species in the
Mediterranean is S. coeruleoalba(4). Due to our small sample size, we can-
not discuss neither sex nor body length of the bycatch animals.
This is the first and basic study on the bycatch of the swordfish driftnet
fishery and we understood that there was a considerable threat for dolphins
in the Turkish Agean Sea coast, although dolphins are under the legal pro-
tection and no direct catch is permitted in Turkey.Therefore, special pro-
tection measures should be prepared, for example, an education program
for fishermen for rescue and release live animals from the net. As banned
in the Barcelona Convention, large-scale driftnets exceeding 2.5 km should
be forbidden and appropriate measures should be taken by the relevant
authorities.
Acknowledgement
Authors thank Istanbul University,Turkish Marine Research Foundation
for the financial support, Orkun Komut and Arda Tonay for their kind help
during the surveys.
References
1 - Alicli Z. and Oray I., 1995. A preliminary report on the investigation of
swordfish (Xiphias gladius, L. 1758) caught in the Turkish waters. Collective
Volume of Scientific Papers, ICCAT, XLIV (1) : 148-150.
2 - Tokac A., Metin C., Lök A., and Gurbet R., 1991. Kuzey Ege Denizi’nde Kilic
aglari ile yapilan Kilic Baligi (Xiphias gladiusL. 1758) avciligi (Swordfish fisheries
in the Northern Aegean Sea). In:Egitimin 10.Yilinda Su Ürünleri Sempozyumu.
Izmir, pp.653- 661.
3 - Di Natale A. and Di Sciara N.G., 1994. A review of the passive fishing nets and
trap fisheries in the Mediterranean Sea and of the cetacean bycatch, pp.189-202. In:
PerrinW.F., Donovan G.P., and Barlow J. (eds.), Rep. Int. Whal. Commn (Special
Issue 15). IWC, Cambridge.
4 – UNEP, 1998. Cetacean Populations in the Mediterraean Sea : Evaluation of the
knowledge on the status of species. UNEP (OCA) MED WG.146/inf.3, Tunis, 45p.
5 – Öztürk B., 1996. Yunuslar ve Balinalar (Dolphins and Whales). Anahtar
Yayinlari, Istanbul, 119p.
6.- Öztürk B. and Öztürk A., 1998. Cetacean strandings in the Aegean and
Mediterranean coasts of Turkey.Rapp. Com. int. Mer Médit., 35 : 476-477.
DOLPHIN BYCATCH IN THE SWORDFISH DRIFTNET FISHERY IN THE AEGEAN SEA
Bayram Öztürk
1,2
*,Ayaka Amaha Öztürk
3
andAyhan Dede
1,2
1
Faculty of Fisheries, University of Istanbul, Turkey - ozturkb@istanbul.edu.tr
2
Turkish Marine Research Foundation, Istanbul, Turkey
3
Institute of Science and Technology, University of Istanbul, Turkey
Abstract
Dolphin bycatch in the swordfish driftnet fishery was examined in the Aegean Sea coast of Turkey, in May and June, 1999 and 2000. In
1999, total 10 bycatches were examined, which were Stenella coeruleoalba (7 individuals), Tursiops truncatus(2) , Grampus griseus(1).
In 2000, total 9 bycatches were examined, which were S. coeruleoalba(6),T. truncatus(2) and G. griseus(1).
Keywords : Cetacea, Conservation, Aegean Sea
YearSpecies
Sex
BL(cm)
1999Stenella coeruleoalba
Male
103
Stenella coeruleoalba
Female
140
Stenella coeruleoalba
Male
173
Stenella coeruleoalba
Male
-
Stenella coeruleoalba
Female
-
Stenella coeruleoalba
Male
-
Stenella coeruleoalba
Female
-
Tursiops truncatus
Male
210
Tursiops truncatus
Unknown
-
Grampus griseus
Female
300
2000Stenella coeruleoalba
Male
150
Stenella coeruleoalba
Unknown
-
Stenella coeruleoalba
Female
200
Stenella coeruleoalba
Male
150
Stenella coeruleoalba
Unknown
-
Stenella coeruleoalba
Female
180
Tursiops truncatus
Female
220
Tursiops truncatus
Unknown
-
Grampus griseus
Male
250
