Starting from 2003, in the framework of the LIFE project NAT/IT/000163, a dolphin-fishery interaction study has been conducted in the Archipelago of Pelagie Islands (South of Sicily, Italy), trough surveys with observers boarded on fishing boats and

1
Bottlenose dolphin (Tursiops truncatus)
interaction with gill net for Mullus surmuletus
at Lampedusa (Sicily)
Celoni, F. (1), Azzolin, M. (2), Galante I. (1),
Comparetto G. (1), Giacoma C. (2)
1)CTS Settore Conservazione Natura, Via Andrea
Vesalio 6, 00161 Roma, Italy 2)Università degli
Studi di Torino, Via Accademia Albertina 13,
10123 Torino, Italy
Abstract In the framework of the LIFE project
NAT/IT/000163, a study on interaction between
Bottlenose dolphin (Tursiops truncatus) and
striped red mullet (Mullus surmuletus) fishing
activity has been conducted in Lampedusa waters
(South of Sicily, Italy) (Fig.1). From February
2005 to September 2006 the interaction among
bottlenose dolphins and Mullus surmuletus fishery
was monitored by CTS researchers directly boarded
on fishing boats, during 35 surveys. In case of
dolphins sightings, the observers collected data
on number of animal and behaviour, in order to
describe interaction among dolphins and fishery
gear. The landed fishes were also weighted and
checked for damage at the end of any fishing
trip. Statistical analysis shows a significant
reduction of total fishery catches, expressed in
Kg/square meter of net, when dolphins were
present in the fishing area 0,0015 Kg/m2 of
Mullus surmuletus without dolphins (30 surveys)
and 7,45310-5 Kg/m2 with dolphins (5 surveys)
(Wilcoxon test, Z-3.536, Plt0.05). The
economical impact of the 5 recorded
dolphins-fishery interactions out of 35 fishing
trip resulted in 182.00 of damage.
supported by

• Results
• In the study period 35 surveys have been carried
  out, preliminary results are presented.
• The analysis of dolphins presence during fishing
  activities shows that (Tab.3)
• dolphins were present in 14,3 of the total
  surveys (5 surveys)
• in just one occasion dolphins were sighted
  during setting, in the other ones they were
  sighted while hauling
• in 3 occasion dolphins didnt move from the
  fishing area when fishing vessel approached, but
  stayed there during hauling for 29 minutes on
  average (26-37 range)
• dolphins mean group size was of 3 animals (2-5
  range)
• in just one occasion a calf was sighted.
• Tab.4 show the results for the analysis of landed
  fishes, in term of catch composition, total catch
  and catch for Mullus surmuletus in both
  condition, with and without dolphins and the
  results of statistical analysis (Wilcoxon test).
• The species caught more frequently with Mullus
  surmuletus are Boops boops, Crenilabrus tinca,
  Dactylopeturs volitans, Diplodus annularis, D.
  vulgaris, Maena maena, Pagellus erythrinus,
  Scarus cretese, Scorpaena scrofa and
  Spondyliosoma cantharus (Fig.2).
• In Tab.5 it is showed the economical damage
  evaluation (ED) for the entire study period.

LIFE 2003 NAT/IT/000163
Surveys during fishing activities Surveys without dolphins Surveys without dolphins Surveys with dolphins Surveys with dolphins Total
Surveys during fishing activities N N Total
Surveys during fishing activities 30 85,7 5 14,3 35
Fig. 1 Bathymetry of the Sicily Channel and
location of Pelagie Islands

• Introduction
• Starting from 2003, in the framework of the LIFE
  project NAT/IT/000163, a dolphin-fishery
  interaction study has been conducted in the
  Archipelago of Pelagie Islands (South of Sicily,
  Italy), trough surveys with observers boarded on
  fishing boats and interview of fishermen.
• The local fishery fleet consists of 95 boats with
  fishing licences the most common systems are
  bottom trawls, hand lines, trolling lines and,
  after these, gill nets, long lines, pots and
  purse seines.
• The results of interviews for different fishing
  gears (Tab.1) show that interaction is complained
  for all of them, but for long lines and pots. The
  focus of the present study is on set gill net,
  because of a complained major economical damage.
• In the study area bottlenose dolphin population
  is regularly monitored in the area by the Nature
  Conservation Department of CTS.
• Mullus surmuletus is fished from August to April,
  using gill nets with mesh size between 22 and 25
  mm, an average overall length of about 1 Km
  (range 0,5-2,4 Km), an average height of 2 m, and
  a mean surface of 2.195 square meter. Those gill
  nets are set at depths ranging from 10 to 45
  meter, twice a day, depending on weather
  condition. Usually the first set is before dawn
  and the first haul is at sunrise, while the
  second set is in the afternoon and the second
  haul is right after sunset. Mean duration of
  setting, fishing and hauling are respectively 13
  (range 9-15 minutes, SD 2.17), 104 (range 45-231
  minutes, SD 42.49) and 45 minutes (range 25-80
  minutes, SD 10.26).

Tab.3 - Survey without/with dolphins
  Without T. truncatus With T. truncatus Without T. truncatus With T. truncatus
  Total mean catch Total mean catch Mean catch for Mullus surmuletus Mean catch for Mullus surmuletus
Kg/m2 0,0072 (SD 0,0052) 0,0069 (SD 0,0073) 0,0015 (SD 0,0012) 7,45310-5 (SD 8,12810-5)
CPUE Kg/Km 15,76 (SD 11,72) 12,57 (SD 12,98) 3,17 (SD 2,37) 0,14 (SD 0,15)
Wilcoxon test results Z -0,660, Pgt0,05 Z -0,660, Pgt0,05 Z-3,536, Plt0,05 Z-3,536, Plt0,05
Tab.4 Fishery catches without/with dolphins
Fishing gear N of fishermen N of fishermen that complain damages N of fishermen that complain damages N of fishermen that complain damages N of fishermen that complain damages
Fishing gear interviewed to fish Type of damage to fishing gear Type of damage
Bottom trawl 17 10 damaged fish 12 holes in net
Trolling and hand line 15 13 damaged fish and caugth fish reduction 14 line damaged
Long line 12 0   0  
Gill net 10 9 damaged fish and fish caugth reduction 9 holes in net
Purse seine 5 4 caught fish reduction 3 holes in net
Pot 5 0   0  
Economic damage in euro () of striped red mullet catch (Mullus surmuletus) Economic damage in euro () of striped red mullet catch (Mullus surmuletus) Economic damage in euro () of striped red mullet catch (Mullus surmuletus) Economic damage in euro () of striped red mullet catch (Mullus surmuletus) Economic damage in euro () of striped red mullet catch (Mullus surmuletus) Economic damage in euro () of striped red mullet catch (Mullus surmuletus)
L (Kg/Km) l (Km) F D Kg price (Euro) ED (Euro)
Mean off catch loss Mean length of Frequency of Total N of Striped red mullet Economic
per species per Km of net the net interactions fishing surveys value damage
3,02692 1 0,143 35 12,00 181,80
Tab.5 - Estimate of Economic damage of Mullus
surmuletus in Euro
Fig.2 Percentage of fishery catches
Tab. 1 Results of interviews

• Material and methods
• From February 2005 to September 2006 the
  interaction among bottlenose dolphins and Mullus
  surmuletus fishery was monitored by researcher
  directly
• boarded on two fishing boats (Tab.2). On board
  observers collected data on fishing area (net
  geographical position, depth and distance from
  shore),
• landed fishes (weight of each species), dolphin
  presence and dolphin-fishery interaction.
• The economic damage caused by the loss of catch
  due the dolphin-fishery interaction was
  calculated considering
• the average catch loss of the main target species
  per km of net (L)
• the local commercial value of the target species
  per kg
• the mean net length used daily by each vessel
  (l)
• the fishing days
• the overall frequency of interactions (F).
• The frequency of interactions was estimated from
  the number of interactions observed during the
  overall number of fishery experiments
• (Lauriano et al., 2004).

Discussion and conclusion This study represents
one of the first attempts in the Mediterranean
basin to study depredation by bottlenose dolphins
to local fisheries. Since the economy of
Lampedusa, one of the biggest island of the
Pelagie Archipelago, is mainly based on fishery
and tourism, and the Pelagie Archipelago is part
of a Marine Protected Area, it is of primary
importance to analyse thoroughly the conflict
between fishermen and bottlenose dolphins in that
area. This study highlights the existence of
what was called operational competitive
interaction (Northridge and Hofman, 1999 Reeves
et al., 2001) between bottlenose dolphins and
fishermen. The analysis of mean catch shows a
significant reduction of fishing catches for
Mullus surmuletus in case of dolphins presence,
even if the frequency of interaction (estimated
from the number of interactions observed during
the overall number of fishery experiments) seems
lower than in other areas 0.143 in Lampedusa
(2005-2006), against 0.27 (1999), 0.25 (2000) and
0.50 (2001) for Sardinia water (Lauriano et al.,
2004). In total the economical impact of the 5
recorded dolphins-fishery interactions out of 35
fishing trip resulted in 182.00 of damage,
about the 15 of the total revenue. Even if the
catch loss in the study area doesnt seem so
relevant, its important to take in account that
for Lampedusa the mean CPUE of striped red mullet
is quite lower than the one for other areas (e.g.
2,9 Kg/Km for Lampedusa against 5,301 Kg/Km for
Sardinia) leading to a worse perception by
fishermen of dolphin depredation. Due to that
some fishermen go from set net to trawling with a
major impact for the ecosystem.
Two kinds of management interventions would be
therefore desirable in the area the first one
aimed at limiting the use of less selective gear
in order to reduce the undesirable biological
effects exerted on resources the second aimed at
finding a system to reduce the interaction
between dolphins and fishing nets.
  Length Tonnage Hp
Boat 1 8.45 3 80
Boat 2 9 2,5 80
References Bearzi G., 2002 Interactions between
cetacean and fisheries in the Mediterranean sea.
In G. Notarbartolo di Sciara (Eds.), Cetaceans
of the Mediterranean and Black Seas state of
knowledge and conservation strategies. A report
to the ACCOBAMS Secretariat, Monaco, February
2002. Section 9 20 pp. Lauriano G., C.M.
Fortuna, G. Moltedo and G. Notarbartolo Di
Sciara, 2004 Interactions between common
bottlenose dolphins (Tursiops truncatus) and the
artisanal fishery in Asinara Island National Park
(Sardinia) assessment of catch damage and
economic loss. In J. Cetacean Res. Manage. 6(2)
165173 pp. Northridge, S.P. and Hofman, R.J.,
1999. Marine mammal interactions with fisheries.
pp. 99-119. In J.R. Twiss Jr. and R.R. Reeves
(eds.). Conservation and Management of Marine
Mammals. Smithsonian Institution Press,
Washington and London. 576pp. Reeves, R.R., Read,
A.J. and Notarbartolo di Sciara, G. 2001. Report
of the Workshop on Interactions between Dolphins
and Fisheries in the Mediterranean Evaluation of
Mitigation Alternatives, May 2001, Rome, Italy.
Paper SC/53/SM3 presented to the IWC Scientific
Committee, July 2001, London (unpublished).
Tab. 2 Boats description
Acknowledgements We thank all the fishermen of
Lampedusa that cooperated with Delta Project.
Without them all the collected information would
havent had a confirmation in the reality. We are
grateful to the Management Board of the Pelagie
Marine Protected Area for its cooperation. We
thank all the people that participated to the
data collection.
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