Seasonal variation of striped dolphins, fin- and sperm whales' abundance in the Ligurian Sea (Mediterranean Sea)
In order to investigate seasonal changes in cetacean relative abundance, a series of surveys were conducted between the French mainland and Corsica. From February 2001 to February 2004, thirty similar transects were conducted monthly, using the same dedicated boat and a consistent sampling protocol,...
| Published in: | Journal of the Marine Biological Association of the United Kingdom |
|---|---|
| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Cambridge University Press (CUP)
2007
|
| Subjects: | |
| Online Access: | http://dx.doi.org/10.1017/s0025315407054719 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0025315407054719 |
| Summary: | In order to investigate seasonal changes in cetacean relative abundance, a series of surveys were conducted between the French mainland and Corsica. From February 2001 to February 2004, thirty similar transects were conducted monthly, using the same dedicated boat and a consistent sampling protocol, including visual observation and passive acoustic sampling. A total effort of 5759 km was sampled, conducted at the same speed and in good sighting conditions. Relative abundances of striped dolphins ( Stenella coeruleoalba ) and fin whales ( Balaenoptera physalus ) were determined using standard line-transect methodology. The relative abundance of striped dolphins peaked in May and September (>1.3×10 -2 ind.km -1 ), while a consistent minimum value (<0.6×10 -2 ind.km -1 ) was obtained from December to April. A maximum relative abundance of fin whales occurred in August with 5.6×10 -2 ind.km -1 and decreased to almost zero from November to January. For sperm whale ( Physeter macrocephalus ), a long diver species, frequency and abundance indices were determined using acoustic sampling. The highest acoustic relative abundance was observed from August to October, with more than 2×10 -2 ind.km -1 . Environmental parameters (sea surface temperature and chlorophyll) were computed for the sampling area from remote sensing imagery and pooled on a monthly basis, to correlate with relative abundance indices of the three species. |
|---|