Con enorme piacere ed orgoglio vi comunichiamo che la prestigiosa rivista internazionale
Marine Ecology ha pubblicato il nostro articolo
Changes in cetacean
presence, relative abundance and distribution over 20 years along a
trans-regional fixed line transect in the Central Tyrrhenian Sea
che illustra i progressi fatti dalla nostra ricerca sui traghetti a partire dagli anni '90 ad oggi.
Cogliamo l'occasione per ringraziare qui tutti coloro i quali, studenti, volontari, equipaggi dei traghetti, Compagnie di navigazione, sponsor, negli anni hanno reso (e rendono tuttora) possibile questa ricerca che, per durata e risultati, ha poco o niente da invidiare a quelle condotte da importanti istituzioni pubbliche (ed a costi assai più elevati).
E andiamo avanti!
Riassunto:
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.
