High similarities in dorsal fin ratios of common bottlenose dolphins (Tursiops truncatus) in the Caribbean Sea

Dorsal fins, one of the most notable dolphin's physical features, play important kinematic and hydrodynamic roles and are related to physiological and environmental adaptation processes. Differences in dorsal fin shape have been recently associated with geographic variation, habitat specialization between ecotypes, and ontogenetic factors. We studied dorsal fin variation across several common bottlenose dolphin populations in the Caribbean. A total of 252 dorsal fin photographs from eight coastal regions in the Caribbean were selected for analysis. Dolphin dorsal fin proportions were compared among regions and compared with data previously collected from Holbox, Mexico. Dorsal fin models were constructed for each region. We found that across the Caribbean, coastal bottlenose dolphins exhibit low variation in dorsal fin shape, with the most common dorsal fin pattern having low and triangular shapes, two traits that greatly contrast with the oceanic ecotype. Also, significant differences in overall dorsal fin proportions found among some adjacent groups support the hypothesis that subgroups could be present even within extremely short geographical distances ‐ as has been previously documented. The results of this study can be implemented in population monitoring efforts worldwide, as it uses free software and provides a step‐by‐step guideline to analyze the data. Resumen Las aletas dorsales son una de las características físicas más notables de los delfines. Éstas desempeñan funciones cinemáticas e hidrodinámicas importantes, relacionándose con adaptaciones a procesos fisiológicos y ambientales. Recientemente se han asociado las diferencias en la forma de la aleta dorsal de los delfines con variaciones geográficas, especializaciones de hábitats entre ecotipos y factores ontogenéticos. En este trabajo, se analizó la variación de la forma de la aleta dorsal en poblaciones de toninas del Caribe. Para esto, se seleccionaron un total de 252 fotografías de aletas dorsales provenientes de ocho regiones costeras, se compararon las proporciones de las aletas dorsales entre regiones, así como con datos previamente reportados para Holbox, México y finalmente, se construyeron modelos generalizados de aletas dorsales para cada región. Se encontró que, en la región Caribe, el ecotipo costero exhibe una baja variación en la forma de la aleta dorsal, presentando un modelo predominantemente triangular y bajo, dos rasgos que contrastan grandemente con el ecotipo oceánico. Ade