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Dissertation
Direct and indirect effects of recreational boats on diamondback terrapins (Malaclemys terrapin)
Doctor of Philosophy (Ph.D.), Drexel University
Aug 2012
DOI:
https://doi.org/10.17918/etd-3982
Abstract
Recreational boating has become an increasingly popular activity over the past 100 years as a result of extensive human population growth in coastal areas. Recreational boats may affect aquatic organisms directly through injury and mortality due to boat strikes and indirectly though increased levels of anthropogenic sounds. The objective of this study was to determine whether recreational boats affect diamondback terrapin (Malaclemys terrapin) populations in Barnegat Bay, New Jersey, USA. I used six years of mark-recapture data to determine whether terrapin injury rates have increased temporally and whether larger terrapins had a higher risk of anthropogenic injury than smaller terrapins. I also used a Cormack-Jolly-Seber (CJS) model to determine if survivorship differed between injured terrapins and uninjured terrapins. In some locations, injury rate of terrapins increased from 2006 to 2011. Larger terrapins were found to be more likely than smaller terrapins to be injured by boats or automobiles. Injured terrapins in some locations also had significantly lower survivorship than uninjured terrapins. I recorded Auditory Evoked Potentials (AEPs) to determine hearing capability of diamondback terrapins in air and underwater. Terrapins responded to sounds from 100 to 1000 Hz with best hearing from 400 to 600 Hz in air. Underwater, terrapins responded to sounds from 50 to 800 Hz with mean lowest threshold of 86 dB re 1 [mu]Pa rms. I recorded sounds of recreational boats and personal watercraft (PWC) in Barnegat Bay and found that boats and PWCs produce sounds that are in the hearing range of diamondback terrapins. Diamondback terrapins were exposed to playback recordings of approaching boat engines in situ. I measured behavioral responses to boat engine sounds including swimming speed, swimming depth, and orientation of terrapin in the water column. Diamondback terrapins did not behaviorally respond to sounds of approaching boats. The lack of behavioral response of diamondback terrapins to recreational boats threatens the survival of terrapin populations. Conservation actions (such as boater education, speed limits, and partial or complete closures of wildlife areas to boats) must be initiated to protect aquatic wildlife from injury and mortality from recreational boats.
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Details
- Title
- Direct and indirect effects of recreational boats on diamondback terrapins (Malaclemys terrapin)
- Creators
- Lori A. Lester - DU
- Contributors
- Harold W. Avery (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Biology; College of Arts and Sciences; Drexel University
- Other Identifier
- 3982; 991014632061304721