Preliminary results of cetacean diversity off the Pacific Ocean of Nicaragua (Central America)

Abstract

This is the first study that has been conducted in the waters of Nicaragua (Central America) along the Pacific Ocean to assess the diversity and occurrence of cetaceans. Boat based surveys were carried out in San Juan del Sur (South-Western Nicaragua) and in Padre Ramos (North-Western Nicaragua) in August 2015 and January -March 2016. Boat based surveys were also effectuated in San Juan del Sur in July 2016 as well as Land based surveys from January-March 2016 (93h of effort). During this period 166 hours and 189 hours of boat based effort has been spent in San Juan del Sur and Padre Ramos respectively. 104 Sightings were recorded during the surveys and 6 cetacean species were identified: one mysticete (Megaptera novaeangliae (n=13)) and five odontocetes (Stenella attenuata (n=70), Stenella longirostris (n=1), Tursiops truncatus (n=17), Steno bredanensis (n=1), Pseudorca crassidens (n=2)). For each sighting: species, groups size, geographic position and primary behavior was recorded. These results will have important implications for future spatial management in the frame of the construction of the canal of Nicaragua.

Full text

Joëlle De Weerdt1, Victoria Pouey-Santalou1, Etienne Pouplard1
Joelle.deweerdt@eli-s.com
1 ELI-Scientific, Allée de Verdalle 39, 33470 Gujan-Mestras, France. www.nicacetacea.org
Preliminary results of cetacean diversity off the Pacific
Ocean of Nicaragua (Central America)
We would like to thank our foundations and research groups for their support and guidance:
UNIVERSIDAD NACIONAL AUTONOMA
DE NICARAGUA, MANAGUA
UNAN-MANAGUA
Joëlle De Weerdt
INTRODUCTION & OBJECTIVE
•First systematic study conducted on
cetacean research along the Pacific Ocean
of Nicaragua (Central America)
•No scientific data available on cetacean
diversity in the country
•Assess the presence and occurrence of
cetaceans in Nicaragua
MATERIAL AND METHODS
RESULTS & DISCUSSION
Boat based survey effort
2015-2016 (Fig 2 & 3)
PR : 189h -SJDS : 166h
CONCLUSIONS & FUTURE PERSPECTIVES
Species
2015-2016 PR
SJDS
Stenella
attenuata X X
Steno
bredanensis X
Pseudorca
crassidens X
Stenella
longirostris X
Tursiops
truncatus X X
Megaptera
novaeangliae X X
•Boat based surveys on a 7m fiberglass boat, sea state <4
on Beaufort scale in San Juan del Sur SJDS (South-
Western Nicaragua) & in Padre Ramos PR (North-
Western Nicaragua) (Fig 1.)
Survey period : August 2015 / January -March 2016
(SJDS & PR) and July 2016 (SJDS only).
For each sighting: species, group size, geographic
position and primary behavioral activity were assessed
•Encounter rate= N/L With N= Number of encounters &
L = Distance surveyed (Nm)
Padre Ramos San Juan del Sur
✓6 different species of cetaceans has been observed along the Pacific coast of Nicaragua during 2015-2016.
✓Encounter rates are higher for humpback whales and pantropical spotted dolphins in San Juan del Sur. Mean group sizes are in the
same range for most of the species encountered on both study sites.
✓More investigation is needed to unravel seasonal variations in the occurrence of the different cetacean species.
Fig. 1: Localization of the study sites in Nicaragua
Species
# of
sightings
% sightings
Mean group
size
Encounter
rate
# of
sightings
% sightings
SJDS
Mean group
size
Encounter
rate
Megaptera novaeangliae 6 14.6 2.3 0.4 8 12.5 1.5 1.1
Steno bredanensis 1 2.4 4.0 0.1
Stenella attenuata 23 56.1 7.9 2.0 47 73.4 7.6 6.2
Tursiops truncatus 9 22.0 3.7 0.8 8 12.5 3.5 0.8
Stenella longirostris 1 1.6 2.0 0.1
Pseudorca crassidens 2 4.9 7.0 0.1
Total 41 100 64 100
Padre Ramos
San Juan del Sur
Fig. 2: Effort and distribution of the different cetacean species in Padre Ramos Fig. 3: Effort and distribution of the different cetacean species in San Juan del Sur
The distribution patterns of
the different cetacean species
differ between the two study
sites.
5 species observed in PR
and 4 species observed in
SJDS
Table 1 : % sightings, Mean group size and encounter rate of each
cetacean species occurring in PR and SJDS.
Mean group sizes:
•Similar for all the dolphin species occurring on both study sites
•Slightly higher mean group size for humpback whales in SJDS
compared to PR
Encounter rates:
•Similar for T. truncatus between the two study sites
•Higher for M. novaeangliae and S. attenuata