RESULTS OF A 2 YEAR ANGEL SHARK SURVEY BY "DAVY JONES DIVING" IN THE ISLAND OF GRAN CANARIA
Krupskaya Narváez1, 3,
Filip Osaer1, 3, Brian
Goldthorpe2, Eduardo Vera2
and Ricardo Haroun1
1BIOGES Centro de Investigación
en Biodiversidad y Gestión Ambiental,
Facultad de Ciencias del Mar. Universidad de Las
Palmas de Gran Canaria. Campus de Tafira s/n,
35017, Las Palmas de G. C. España.
2DAVY JONES DIVING, Calle Luis Velasco
39, Playa de Arinaga, 35118 Aguimes, Las Palmas de
G. C. España.
3SQUALUS, Fundación colombiana
para la investigación y conservación
de tiburones y rayas. Carrera 64 A No. 11 A-53,
Cali, Colombia.
krupska@gmail.com, filiposaer@gmail.com y
info@DavyJonesDiving.com and rharoun@dbio.ulpgc.es
INTRODUCTION
The dive centre "Davy Jones Diving" is collecting data of their interactions with the angel shark Squatina squatina in the Island of Gran Canaria in order to contribute to the study of habitat use of this critically endangered species (IUCN, Morey et al., 2006).
RESULTS
During the period of May 2006 until August 2008, a
total of 271 angel sharks were sighted in 1709
dives. 244 of these interactions took place in the
coastal area of "El Cabron". The months with the
highest likelihood of sightings were January 2007
and February 2008, although sightings remained high
from December to June, in both years (Fig. 1).
After being rarely seen during autumn, a sudden
peak in sightings occurs when the temperature drops
below 21 oC. The sightings remain high until the
temperature raises again over 21 oC (Fig. 2). Up to
3 sharks were spotted in one dive during the months
of May 2007 & 2008, December and February 2007.
9% of the sightings were juveniles.
It is difficult to identify the sex of the sharks
which are fully covered with sand and also from
juveniles without causing a lot of stress to them.
Therefore, the sex could only be determined in 41%
of the cases. The overall sex distribution is 1:
1,6 (female, 61 : male, 38). Males were only seen
between November and May, while females were seen
all year round. Both sexes are found in similar
depth ranges (2.5 - 30 m), but were usually seen
around 9 m of depth.
The sharks are normally found solitary (98%) and
also while resting on the bottom (85%) of which 80%
were buried in the sand. In rare occasions they
were found on rocky outcrops. Only during the
colder months (November to June) they were
encountered while swimming (15%), of which 70% were
males. Also during this period, 40% of the resting
males were found uncovered and only 28% of the
females.
Generally angel sharks do not react (79%) to the
presence of the divers. They remain in their
resting position or continue swimming their course,
even if this is towards the divers. Only 21% did
not appreciate the attention of the group and swam
away and in 1 case the reacting shark turned
towards one of the divers.
CONCLUSION
This study was able to find a regular pattern in
the sightings of the common angel shark in the "El
Cabron" coastal area.
The sharks can be seen throughout the year, but the
colder months (temperatures below 21 oC) have the
highest likelihood of sightings. Also, during this
period, most of the sightings are in relative
shallow waters (9 m) and close to the coastline
(less than 50 m). Peaks in sightings can change
over the years depending on the sea conditions
(temperature). Juveniles were found both during the
day and at night, throughout the year and without
showing a preference for temperatures or
months.
Although the preference of the sharks is laying on
the bottom and being fully covered with sand, they
were also found during the colder months while
being uncovered and while swimming. Proportionally,
males were more often found while swimming and not
covered with sand than females, indicating that
males are more active or more mobile than females
during these months.
One anecdote revealed interesting information about
the feeding behavior during the day. In May 2008, a
male shark which was found buried, released its
prey while swimming away from the divers. The
released lizardfish swam away quickly, indicating
that it had been captured recently. This shows that
the angel sharks, even though while buried in the
sand during the day, are alert for capturing prey
and are not asleep as assumed by many.
Finally it is also worth to emphasize that 3 male
angel sharks were freed from fishing nets found
between 6 and 12m of depth.
ACKNOWLEDGEMENTS
We are very grateful to: Annette Goldthorpe, Andy Batty, Jim Darby, Johan Rust, Hector, Natalie Craig, Pablo Naranjo Garcia, Ron van der Linden, Uwe Gohr and all the other staff and guests of the "Davy Jones Diving Centre" for their continuous recording of the interactions with angel sharks. The 'Agencia Española de Cooperación Internacional' (AECI-MAE) for the, funding of Ph D of Krupskaya Narváez and The Shark Foundation.
BIBLIOGRAPHY
Morey, G., Serena, F., Mancusi, C., Fowler, S.L.,
Dipper, F. & Ellis, J. 2006. Squatina squatina.
In: IUCN 2007.
2007 IUCN Red List of Threatened
Species. . Downloaded on 29 September 2007
