Dolphin & Vessel Interactions
The Corpus Christi Ship Channel experiences a variety of daily boat traffic. Dolphins use this ship channel for their daily activities, such as feeding, mating, and playing. Vessel operation and marine construction in coastal areas commonly interrupts dolphin behavior. Close follows from ecotours and loud noises from construction and shipping have been found to disturb dolphin habitat use, behavior, and abundance in an area. A project is underway to gain knowledge of dolphin and vessel interactions in the ship channel off of Port Aransas, Texas.
Photo Credits: Eliza Mills, NMFS permit no. 23203
How do we study dolphin and vessel interactions?
A unique aspect of this project is that all data collection on dolphin behavior and interactions with vessels occurs from shore in Port Aransas, Texas. Many studies on dolphin behavior use a research boat as it is easier to get closer to the dolphins in order to collect data on specific individuals through photo-identification techniques (we do this too in other projects!). However, when specifically looking at dolphin and vessel interactions, this method can alter dolphin behavior as well due to the research vessel. Collecting data from land for this project is ideal as we have no alter on dolphin behavior, habitat use, and abundance.
From shore in Port Aransas, TCBDP researchers set up a field station consisting of a table and chair, binoculars, a digital theodolite, a field computer, and a canopy (to reduce the Texas heat!). TCBDP researchers also use a Sony camera to visually capture dolphins and vessels in the Corpus Christi Ship Channel.
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A digital theodolite is used in the field to track dolphin movement and document behaviors. The theodolite is a surveying instrument that uses two reference locations (chosen by the researchers) to triangulate the area an object is in. The scope of the theodolite is aimed at the dolphin at the surface of the water and a GPS location (latitude and longitude coordinates) can be calculated for that specific location. TCBDP researchers can collect accurate locations of dolphin groups in the ship channel to be mapped in software like ArcGIS for spatial analysis. The digital theodolite is connected to a field computer running Mysticetus software. Mysticetus creates a map of the dolphin and vessel tracks in real-time, so we can see how the dolphins are moving in the ship channel (see picture above for map reference).
Behaviors are collected through observation of dolphin activity using binoculars. We document when dolphins are foraging/feeding, traveling, mating, playing, and performing other more unique activities like bow-riding.
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Currently, TCBDP researchers are trying to determine if dolphin behavior changes with vessel presence and their specific vessel aspects: vessel type, vessel size, bow shape, vessel speed, vessel activity). Determining the influence of vessels activity on dolphin behavior could help in promoting dolphin protection and conservation in an industrialized coastal area.