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Cetaceans of the Central Tyrrhenian Sea: Going, Going ... Gone???
Arcangeli, A., Marini, L. and Crosti, R. 2012. Changes in cetacean presence, relative abundance and distribution over 20 years along a trans-regional fixed line transect in the Central Tyrrhenian Sea. Marine Ecology 34: 112-121.

The authors state that during the last two decades (from 1988 to 2006), increases in temperature and salinity trends at deep and intermediate levels were documented in the Central Tyrrhenian Sea, with clear accelerations observed since the 1990s, citing the work of Gasparini et al. (2005) and Schroder et al. (2006). In addition, they say that "the increasing intensity of some pressures, including maritime traffic (Abdulla and Linden, 2008), may have had an impact on species size and distribution." Hence, they had good reason to strive to acquire some meaningful real-world data pertaining to this specific situation.

What was done
After describing how, from 1990-1992, dedicated surveys along a fixed-transect in the Central Tyrrhenian Sea had been carried out twice a week (mostly late May through late September) by Marini et al. (1997) - who used passenger ferries as research platforms - Arcangeli et al. (2012) go on to describe how they made similar measurements from 2007-2009 "under the same protocol and supervision of the same investigators (Arcangeli et al., 2008), giving the opportunity to compare consistent data over a long period." So did their persistence pay off?

What was learned
Contrary to what many might have expected, the three Italian researchers report that "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)." And they say that sightings of fin whales (Balaenoptera physalus) increased dramatically by fully 300%.

What it means
Excited about their positive findings, and hoping to preserve the impressive cetacean populations they encountered, Arcangeli et al. (2012) say that the sea creatures' current abundant presence implies "the consequent necessity of specific legislative acts for cetacean conservation," which is something they are hoping to promote.

Abdulla, A. and Linden, O. (Eds.). 2008. Maritime Traffic Effects on Biodiversity in the Mediterranean Sea: Review of Impacts, Priority Areas and Mitigation Measures. International Union for Conservation of Nature, Centre for Mediterranean Cooperation, Malaga, Spain.

Arcangeli, A., Crosti, R., Marini, L., Poggi, A., Poldi, A., Pulcini, M., Safontas, C., Sdringola, S. and Ukmar, E. 2008. Monitoring cetacean populations over 15 years in Central Tyrrhenian Sea using a non-dedicated ferry as a observation platform. In: Pierce, G.J. and Lick, R. (Eds.). European Research on Cetaceans 22.

Gasparini, G.P., Ortona, A., Budillon, G., Astraldi, M. and Sansone, E. 2005. The effect of the eastern Mediterranean transient on the hydrographic characteristics in the Strait of Sicily and in the Tyrrhenian sea. Deep-Sea Research I 52: 915-935.

Marini, L., Consiglio, C., Angradi, A.M., Catalano, B., Sanna, A., Valentini, T., Finoia, M.G. and Villetti, G. 1997. Distribution, abundance and seasonality of cetaceans sighted during scheduled ferry crossings in the central Tyrrhenian Sea: 1989-1992. Italian Journal of Zoology 63: 381-388.

Schroder, K., Gasparini, G.P., Tangherlini, M. and Astraldi, M. 2006. Deep and intermediate water in the western Mediterranean under the influence of the Eastern Mediterranean Transient. Geophysical Research Letters 33: 1-6.

Reviewed 31 July 2013