Vessels Disturb Bottlenose Dolphin Behavior and Movement in an Active Ship Channel

Area of Science:

• Marine Biology
• Wildlife Conservation
• Environmental Science

Background:

• The Port of Corpus Christi is a major oil exporter with significant year-round vessel traffic.
• The impact of this industrial activity on local marine mammal populations, specifically common bottlenose dolphins (Tursiops truncatus), is not well understood.

Purpose of the Study:

• To assess the behavioral states and movement patterns of common bottlenose dolphins in the Corpus Christi Ship Channel (CCSC).
• To determine the relationship between vessel traffic and dolphin behavior in this busy port environment.

Main Methods:

• Shore-based digital theodolite and Automatic Identification System (AIS) receiver were used to collect data.
• Multinomial logistic regression and generalized additive models were employed for data analysis.
• Vessel presence within 300m of dolphins was recorded during 80% of observations.

Main Results:

• Dolphins exhibited frequent foraging (40%), traveling (24%), socializing (15%), and milling (14%) behaviors.
• Season, time of day, group size, vessel type, vessel size, and number of vessels significantly predicted dolphin behavioral states.
• Dolphin movement patterns were influenced by season, time of day, group size, calf presence, vessel type, and vessel numbers.

Conclusions:

• The CCSC is a critical foraging area for dolphins, but high industrial activity poses risks of disturbance and injury.
• There is an urgent need to monitor anthropogenic impacts on federally protected dolphins in active shipping channels.
• Findings have broad implications for dolphin conservation in other major ports worldwide.