We are pleased to announce the publication of the paper:
"Changes in
cetacean presence, relative abundance and distribution over 20 years along a
trans-regional fixed line transect in the Central Tyrrhenian Sea"
http://onlinelibrary.wiley.com/doi/10.1111/maec.12006/abstract
ABSTRACT
From 1989 to 1992, systematic cetacean surveys were carried out twice weekly
along a trans-regional fixed transect in the Central Tyrrhenian Sea, utilising
passenger ferries as research platforms. Using the same protocol and supervised
by the same investigators, the research restarted in 2007, providing the
opportunity to compare consistent data over a long 20-year period. The
monitored transect (Civitavecchia-Golfo Aranci) runs along a strategic area
just outside the southeastern border of the Pelagos Sanctuary. Over the last
two decades, an increasing trend of temperature and salinity, in the deep and
intermediate layers, has been documented in the region, as well as general
changes over the Mediterranean basin. These changes, together with the
increasing impact of some pressures (e.g. maritime traffic) may have led to
changes in oceanographic and anthropogenic features and, subsequently, in
cetacean presence and distribution. The research aimed to
verify whether any changes occurred in the pattern of cetacean occurrence over
the 20-year period along the representative transect in the Central Tyrrhenian
Sea. Data from 90 summer weekly runs undertaken in the 1990s were compared with
data obtained from 95 runs undertaken in the 2000s. Each ferry run was
considered an independent statistical unit: the encounter rate (ER = number of
sightings per hour spent on effort) was calculated to compare relative
abundance between periods, years and months. Spatial analysis was performed on
geographical data using Kernel analysis to map the distribution of sightings.
Logistic regression (GLM) was performed to compare habitat preference. Total
encounter rate in the 1990s (ER = 0.59 ± CI 0.08) was significantly lower
(P < 0.01) compared with the 2000s (ER = 0.94 ± CI 0.15). The same seven out of
eight species known for their regular presence in the Mediterranean Sea were
sighted in both the
investigated periods. The most common species were striped dolphin (Stenella
coeruleoalba), fin whale (Balaenoptera physalus) and common bottlenose dolphin
(Tursiops truncatus). Neither the pilot whale nor any other rare or occasional
species were sighted during the 6 years of the study. Despite the time span, no
dramatic changes were observed for any species, bar fin whale, in terms of
distribution, relative abundance, group size or habitat preference. Sightings
of fin whale have surprisingly increased (+300%, P< 0.001), and their spatial
and temporal distribution and habitat preference showed a radical difference
between the two periods. The 2000s surveys confirmed the existence of high
density areas of cetaceans, especially of fin whale, and the consequent
necessity of specific legislative acts for cetacean conservation.
http://onlinelibrary.wiley.com/doi/10.1111/maec.12006/abstract
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