Cetacean and sea turtle sightings in Gabon

Marijke N. de Boer

Information on cetaceans and marine turtles off Gabon in tropical West Africa was collected during boat-based surveys carried out between 7 March and 7 August 2009. Thirteen cetacean species were positively identified comprising two baleen whale species, one sperm whale species and ten species of delphinid. Bryde’s whale (Balaenoptera brydei) and humpback whale (Megaptera novaeangliae) were the most frequently encountered species. Cetaceans were found throughout a range of sea surface temperature between 20.5˚C and 27.5˚C and a wide range of depths with the majority of effort and sightings occurring seaward of the shelf break. Of particular interest from the study were the following: (1) Gabonese waters have a broad cetacean diversity, especially with a large and diversified delphinid community in the northern part of the study area; (2) the variations in oceanographic conditions within Gabonese waters are likely to result in a temporal variation in species composition; (3) the sightings of Atlantic spotted dolphin (Stenella frontalis) are the first at-sea sightings confirmed for these waters, although not unexpected given their distribution and abundant presence in surrounding waters; and (4) the poorly known Clymene dolphin (Stenella clymene) was sighted on four occasions in deep oceanic waters and was the most abundant cetacean. These are the first confirmed records of Clymene dolphins in Gabonese waters.

The main purpose of this study was to contribute information on the distribution and relative abundance of cetaceans sighted during a geophysical survey in Gabonese waters and where possible relating the occurrence of different species with oceanographic parameters such as sea surface temperature (SST) and depth.

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Overview

This section explains attributes included in the original dataset. OBIS-SEAMAP restricts the attributes available to the public to date/time, lat/lon and species names/counts only. Should you need other attributes described here, you are encouraged to contact the data provider.

Attributes described below represent those in the original dataset provided by the provider.
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Attributes in dataset

Attribute (table column)	Description
oid	Unique ID number (generated by OBIS-SEAMAP)
sighting_no	Sighting Number
date_time	Date and time at local time zone
datetime_utc	Date and time at UTC
observer	The name of the observer who first sighted the animal
latitude	Latitude in decimal degrees
longitude	Longitude in decimal degrees
depth	Water depth (metres)
species	Species name
latin_name	Latin name
sp_tsn	Taxonomic Serial Number added by OBIS-SEAMAP
certainty	Certainty
distance	Distance (m)
num_animals	Number of animals
notes	Notes
timezone_h	Time zone added by OBIS-SEAMAP
geom	Geometry field added by OBIS-SEAMAP