In 2004 (17 April-13 May) the LAPE project, with additional assistance from the Government of Japan, conducted a sighting survey from the specialized cetacean research vessel Shonan Maru. The observers worked from the upper bridge and two expert observers worked from the top barrel position, approximately 20 m above the water.
The survey was a stratified transect design but unfortunately was unable to include the waters of Trinidad and Tobago. Data collected from the tracks indicated as primary search lines were used in the statistical analysis of cetacean abundance.
The sighting conditions during the survey were marginal at times and at others, required suspending primary sighting effort. The small numbers of sightings (42 cetacean detections while on primary search effort) made statistical estimation of abundance challenging. Species level estimates were not possible and, even at the functional group level, the sample sizes were below the desirable minimum numbers. Notwithstanding this, there is a need to obtain some estimates of density and abundance from these data. These results are associated with large margins of error and potential biases. In spite of these uncertainties, these are the only data suitable for abundance estimation available for the LAPE area.
The focus of the present project is on trophic functional groups and, considering which species are likely to be similar in terms of detectability, estimation based on the following species groups was felt to be reasonable.
Group 1: Shallow-diving small cetaceans (20 primary detections): This group comprises bottlenose dolphins, short-snouted spinner dolphins, pantropical spotted dolphins, Atlantic spotted dolphins, Fraser's dolphins, striped dolphins, short-finned pilot whales and melon-headed whales.
Group 2: Deep-diving whales (11 primary detections): This group comprises sperm whales, Gervais' beaked whales, unidentified beaked whales (Mesoplodon sp. and Ziphiidae).
Group 3: Baleen whales (11 primary detections): This group comprises humpback whales, Bryde's whales and unidentified baleen whales.
Sightings classified by functional groups
Baleen whales - Note that humpback whales, although sighted and included in these results, were not included in the LAPE model functional groups as they do not feed in the LAPE area.
Killer whales - No species of killer whales were identified during the survey.
Shallow-diving small cetaceans.