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Habitat
use and status of Chilean and Peale’s dolphins in the Chiloé Archipelago
in southern Chile, Dipl.
Biol. Sonja Heinrich
Survival strategies
of two poorly known dolphin species in one of the biggest aquaculture growth
regions in South America
Since summer 2002
yaqu
pacha added another poorly known small dolphin species (see also La
Plata-Dolphin) to its list of action: the Chilean dolphin. Chilean
dolphins occur only in the coastal waters of middle and southern Chile
(approximately from Valparaiso to Tierra del Fuego).
For
decades, Chilean dolphins along with other species such as the larger Peale’s
dolphins, Lagenorhynchus australis, have been taken extensively for bait
in commercial swordfish and crab fisheries in southern Chile.
This
detrimental direct take now seems to have ceased due to more restrictive
legislation and changes in fishing methods.
At
present, main concerns for Chilean dolphins and for Peale’s dolphins arise
from incidental catches in coastal artesanal gill net fisheries and from
progressive destruction of potentially critical habitat.
Aquaculture
farms (e.g. for salmon and mussels) have been expanding dramatically in
the sheltered bays and fjords in southern Chile and could impact the entire
coastal ecosystem.
The
little scientific information that is available suggests that aquaculture
farming activites in the Archipiélago de Isla Chiloé could
overlap with important dolphin habitat (such as foraging and nursing areas).
For
conservation measures to be effective it is important to identify
these critical dolphin habitats and to determine the extend and effects
of human activities on the resident dolphin populations.
The Chiloé
dolphin project
Since
early 2001 an international team of German, British and Chilean biologists
has been studying habitat use of and potential man-made impacts on Chilean
and Peale’s dolphins in the Chiloé Archipelago.
The
team is gathering information on distribution, ranging patterns and social
behaviour of the two dolphin species as well as on biological and physical
properties of their marine habitat.
Data
has been collected using boat-based sighting surveys (zig-zag line transects)
conducted with a small inflatable boat (zodiac).
This
is the first time that the well-known photo-ID method is applied to Chilean
dolphins (Peale’s dolphins have been photographed before in Tierra del
Fuego) and it proved to be a bit of a challenge due to the erratic and
shy behaviour of these little dolphins. Resighting data of identifiable
dolphins can now be used to establish residency patterns, home ranges and
to investigate local population sizes as well as social affiliations among
the dolphins.
The
boat surveys also allow to examine the dolphins’ distribution in time,
space and in relation to oceanographic (e.g. water depth, sea surface temperature,
salinity), biological (e.g. prey distribution) and anthropogenic (e.g.
boat traffic, aquaculture farming) parameters.
Data
from the photo-ID surveys and environmental monitoring will be combined
to model habitat utilization by the dolphins and determine critical habitats.
These data provide ecological baseline information on each dolphin species,
help to formulate specific recommendations for coastal management plans
(especially to create marine protected areas) as well as for the growing
ecotourism ventures.
This
project is conducted in close cooperation with the local district councils
on Chiloé, the Chilean Maritime Authorities and different local
interest groups. Local involvement is one of the most important factors
(along with secure funding) to guarantee a successful scientific long-term
project and to effectively implement conservation strategies. |
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