Ecological and genetic characterization of the population of
the bottlenose dolphin Tursiops truncatus along the Israeli
coastline.
Aviad Scheinin
Tursiops is a cosmopolitan genus found in temperate and tropical marine
waters worldwide. Although it tends to primarily inhabit coastal waters, it can
also be found in pelagic waters. The pelagic populations seem to be
genetically isolated from the coastal. In Israel, the common bottlenose dolphin
Tursiops truncatus is the most abundant cetacean species along the
Mediterranean coastline. Although, worldwide, this is the most researched
cetacean species, in Israel, research on this species has only just begun. The
main research carried out so far in Israel was based on the investigation of
carcasses washed ashore, by collection of morphological data and by
analysis of the levels of heavy metals in their tissues. Before this work, only a
couple of preliminary open sea dolphin surveys were done.
This study’s main aim was to perform an ecological and genetic
characterization of the bottlenose dolphin population along the Israeli
coastline, as a representative of the poorly-researched eastern basin of the
Mediterranean Sea. Towards this aim, 30 half-day dolphin surveys were
conducted between the years 2000-2002, from a research boat. In 13
surveys, dolphins were sighted and documented using the individual photo
identification method. In 9 out of the 13 sightings, the dolphins were spotted in
the vicinity of trawlers. On all encounters, common bottlenose dolphins were
the only species observed, with an average group size of 4.72 (S.D. = 1.35).
So far, 25 dolphins were photo identified and cataloged. Only 2 out of the 25
identified individuals were observed twice.
A molecular analysis was performed on muscle/skin samples of 11-beached
members of the population of the bottlenose dolphins (Tursiops truncatus)
along the entire Israeli coastline, using microsatellite markers. As part of a
feasibility study of the use of such markers on skin-scrubbed samples, the
occasion rose to include in the analysis 7 captive Black-Sea bottlenose
dolphins (Tursiops truncatus ponticus), living in the Eilat “Dolphin Reef”,. A
new protocol was created to extract nuclear DNA from the skin tissues, since
there is a lack of information about this procedure in the literature. Nine
microsatellite markers (EV01, EV14, EV94, TexVet03, TexVet05, TexVet07,
D14, D22 and D28), taken from the literature, were applied on the combined
study group. The results showed that the Israeli Mediterranean coastal
dolphins may be divided into 2 subpopulations, northern and southern. When
comparing the Black-Sea dolphins to Mediterranean dolphins using cluster
analysis,
a
clear
difference
(an
appreciable
genetic
distance?)
is
demonstrated. The latter result lends support to the genetic isolation of
Tursiops truncatus ponticus and, if further substantiated, may help to
implement specific management plans In order to adopt international
agreements, such as the recently-failed attempt to move it from Appendix II to
I for better local protection.
This research is another brick in the foundation of cetacean research in Israel.
Supervised by: Prof. Yoram Yom-Tov, Dr. Ofer Mokady & Dr. Dan Kerem