Sperm Whales Colissions In Canary Islands
Fotografia de A. Tennakoon bajo Creative Commons Attribution 2.0 Generic License.
Ship-strikes are an unpleasant reality related to cetaceans. Cetaceans need come to the surface to breathe, and at that moment is when they are vulnerable to collisions with shipping traffic. As known, the most swallow diving species and those wich spends more time on the surface are especially sensitive to this problem. That is the case of sperm whales colissions in Canary islands.
A mixed group of researchers, led by Andrea Fais, a researcher of BIOECOMAC group at the University of Laguna, recently published an important study that reflects the situation of the population of sperm whale (Physeter macrocephalus) in order to examine the viability of the population against the threat of ship strikes. You can freely download the article (http://dx.doi.org/10.1371/journal.pone.0150660).
The sperm whale is a deep diving cetacean forming groups of females with immature, that show a marked tendency to occupy a certain area, and males who leave these family groups to travel alone or in small groups of males in polar regions. Only with females are found in warmwater for reproduction.
This tendency of females to occupy a particular place, philopatry, makes to several of them to find what could be called home. In our shores they find good habitats with abundant resources but due to human presence and activities their survival rate drops to cause local extinctions. Their survival will depend on factors such as the size of the population itself or the flexibility of it. Studies such as André, M (1997) put the focus of the survival of this species in the Canary Islands in collisions with large ships.
According to the calculations presented in this new study previously cited, the recruitment rate, ie the ability of a population of incorporating new individuals by birth, is 2.5 whales per year, given that the absolute abundance obtained was 225 animals in the archipelago.
Picture taken from the cited paper. doi:10.1371/journal.pone.0150660.g005
Between 1991 and 2007, 11% of stranded cetaceans showed signs of collision, about 59. What is a very high figure. It has also been identified that the vessel speed is a determining factor in collisions.
One of the fatal outcome of this work is that the amount of sperm whales that the islands are able to produce, those 2,5 baby sperm whales per year, are dangerously close to the nearly 2 sperm whales stranded with signs of having collided with a boat by year, not counting the bodies that are never recovered. These results herald a decline in population. Further research is needed to mitigate the factors threatening the survival of the species.
We hope that the authorities concerned and the aforementioned companies take a firm determination to protect local fauna. We know collaboration that companies have always shown for these issues cooperating on projects such as the Canarias con la Mar (https://canariasconlamar.wordpress.com/).
We must not forget that damaging our natural environment we hit our own goose that lays golden eggs. How to fill the ferris if the quality of our tourist attractions diminishes? Let us be responsible.
Fais A, Lewis TP, Zitterbart DP, Álvarez O, Tejedor A, Aguilar Soto N (2016) bundance and Distribution of Sperm Whales in the Canary Islands: Can Sperm Whales in the Archipelago Sustain the Current Level of Ship-Strike Mortalities? PLoS ONE 11(3): e0150660. doi:10.1371/journal.pone.0150660
André M. Distribución y conservación del cachalote (Physeter macrocephalus) en las Islas Canarias. Ph.D. Thesis, University of Las Palmas de Gran Canaria. 1997.