Mark-recapture method applied on two coastal pantropical spotted dolphin populations (Stenella attenuata graffmani) in Nicaragua: A comparison.

Abstract

Pantropical spotted dolphins (Stenella attenuata) are a widespread species in the Pacific Ocean. Recent genetic studies have confirmed that two subspecies (coastal and offshore) were identified along the Pacific coast from Mexico to Nicaragua. Studies using mark-recapture methods on pantropical spotted dolphins are scarce. This study offers a comparison on mark-recapture between two coastal populations of pantropical spotted dolphins in Nicaragua. Two study sites have been included: Padre Ramos (PR) lying in the North-West coast of Nicaragua and San Juan del Sur (SJDS) in the South-West coast of Nicaragua. Spotted dolphins have been studied within the cetacean conservation project in Nicaragua over a total effort time of 346h in August 2015, in January to March 2016 and in July 2016. Photo-identification data has been collected and thanks to the mark-recapture technique resightings of individual spotted dolphins have been inferred. Resighting rates in SJDS are higher during February and March compared to in PR during the same period. The animals were seen most of the time feeding in SJDS which could be explained by the presence of the Costa Rican Dome (CRD), an upwelling zone, that comes toward the coastal area of SJDS from February to April. More research is needed that include more specific data in the analysis in order to confirm the hypothesis. Understanding cetacean distribution in function of natural currents in tropical ecosystems have important implications for the management and safeguard of this cetacean species occurring in 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
Mark-recapture method applied on two coastal pantropical spotted
dolphin populations (Stenella attenuata graffmani) in Nicaragua: A
comparison
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
•Pantropical spotted dolphins (Stenella attenuata
graffmani) are a widespread species in the Pacific
Ocean.
•Recent genetic studies have confirmed that two
subspecies (coastal and offshore) were identified
along the Pacific coast from Mexico to Nicaragua.
•Studies using mark-recapture methods on
pantropical spotted dolphins are scarce.
•This study offers a comparison on mark-recapture
applied on two coastal populations of pantropical
spotted dolphins in Nicaragua.
•The objective is to investigate the residency
patterns, site fidelity and seasonal occurrence of
the spotted dolphins in Nicaragua
MATERIAL AND METHODS
RESULTS & DISCUSSION
CONCLUSIONS & FUTURE PERSPECTIVES
•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.). Boat based
survey effort 2015-2016 PR :189h - SJDS : 166h.
•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
•A quality Grading system has been applied and only
pictures having quality 1 (best quality) were
integrated in the analysis.
•Use of dorsal fin characteristics and spots for
identification
Fig. 1: Localization of the study sites in Nicaragua
Fig 3: Resighting rate of Spotted dolphins in Nicaragua. 4% and
16% of the dolphins were observed more than once in PR
in SJDS
Manchita (Man)
Panchita (Pan)
Resighting rates of spotted dolphins in San Juan del Sur (16%) are higher than in Padre Ramos (4%). Resightings in San Juan Del Sur,
occurred both during dry season (Jan-Apr) and wet season (Aug-Jul) (Table 1).
2015
ID Sex Aug Jan Feb Mar Jul RR
Sa_SJDS_001 2
Sa_SJDS_006 2
Sa_SJDS_014 2
Sa_SJDS_015 2
Sa_SJDS_022 3
Sa_SJDS_037 5
Man 9
Pan 6
Sa_SJDS_052 5
Sa_SJDS_053 6
Sa_SJDS_054 7
ELI-S 9
Sa_SJDS_056 4
Sa_SJDS_057 6
Sa_SJDS_058 2
Sa_SJDS_059 3
Sa_SJDS_060 F2
Sa_SJDS_061 2
Sa_SJDS_063 3
Sa_SJDS_064 2
Sa_SJDS_065 3
Sa_SJDS_072 2
Sa_SJDS_077 3
Sa_SJDS_085 2
Sa_SJDS_095 2
Sa_SJDS_096 2
Sa_SJDS_101 2
Sa_SJDS_103 2
Sa_SJDS_104 2
Sa_SJDS_109 2
Sa_SJDS_110 2
Sa_SJDS_114 2
Sa_SJDS_115 2
Sa_SJDS_121 2
Sa_SJDS_122 2
Sa_SJDS_124 3
Sa_SJDS_126 3
Sa_SJDS_128 2
Sa_SJDS_132 3
Sa_SJDS_136 2
Sa_SJDS_137 3
Sa_SJDS_202 2
Sa_SJDS_206 4
Sa_SJDS_209 2
Sa_SJDS_211 2
Sa_SJDS_214 2
Sa_SJDS_226 4
Sa_SJDS_233 2
Sa_SJDS_234 F2
Sa_SJDS_239 4
Sa_SJDS_253 2
Sa_SJDS_255 2
Sa_SJDS_256 3
2016
Table 1: Seasonal occurrence of spotted
dolphins of San Juan del Sur
observed more than one time. RR=
Resighting Rates
Fig 2: Example of quality one pictures of two spotted dolphins
displaying a high spotting pattern and clear dorsal fin
knicks and notches
The presence of coastal nutrient rich upwelling waters (Costa Rican Dome) in San Juan del Sur might explain the higher fidelity of pantropical spotted in the area during dry
season. The favorable conditions probably promote the presence of prey and could explain the higher resighting rate observed in SJDS compared to PR.
More research is needed to investigate if the trend is similar over different years and to compare resighting rates between dry and wet season