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Martin, Julien; Sabatier, Quentin; Gowan, Timothy A.; Giraud, Christophe; Gurarie, Eliezer; Calleson, Charles Scott; Ortega-Ortiz, Joel G.; Deutsch, Charles J.; Rycyk, Athena M.; Koslovsky, Stacie M.
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2015 |
A quantitative framework for investigating risk of deadly collisions between marine wildlife and boats.
Methods in Ecology and Evolution 7: 42-50. 3 figs. DOI: 10.1111/2041-210X.12447. Published online Nov. 12, 2015.
–ABSTRACT: 1. Speed regulations of watercraft in protected areas are designed to reduce lethal collisions with wildlife but can have economic consequences. We present a quantitative framework for investigating the risk of deadly collisions between boats and wildlife.
2. We apply encounter rate theory to demonstrate how marine mammal–boat encounter rate can be used to predict the expected number of deaths associated with management scenarios. We illustrate our approach with management scenarios for two endangered species: the Florida manatee Trichechus manatus latirostris and the North Atlantic right whale Eubalaena glacialis. We used a Monte Carlo simulation approach to demonstrate the uncertainty that is associated with our estimate of relative mortality.
3. We show that encounter rate increased with vessel speed but that the expected number of encounters varies depending on the boating activities considered. For instance, in a scenario involving manatees and boating activities such as water skiing, the expected number of encounters in a given area (in a fixed time interval) increased with vessel speed. In another scenario in which a vessel made a transit of fixed length, the expected number of encounters decreases slightly with boat speed. In both cases, the expected number of encounters increased with distanced travelled by the boat. For whales, we found a slight reduction (˜0·1%) in the number of encounters under a scenario where speed is unregulated; this reduction, however, is negligible, and overall expected relative mortality was ˜30% lower under the scenario with speed regulation. The probability of avoidance by the animal or vessel was set to 0 because of lack of data, but we explored the importance of this parameter on the model predictions. In fact, expected relative mortality under speed regulations decreases even further when the probability of avoidance is a decreasing function of vessel speed.
4. By applying encounter rate theory to the case of boat collisions with marine mammals, we gained new insights about encounter processes between wildlife and watercraft. Our work emphasizes the importance of considering uncertainty when estimating wildlife mortality. Finally, our findings are relevant to other systems and ecological processes involving the encounter between moving agents.
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Rycyk, Athena M.; Deutsch, Charles J.; Barlas, Margaret E.; Hardy, Stacie K.; Frisch, Katherine; Leone, Erin H.; Nowacek, Douglas P.
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2018 |
Manatee behavioral response to boats.
Mar. Mamm. Sci. 34(4): 924-962. 5 tabs. 15 figs. + suppl. information. doi:10.1111/mms.12491. Feb. 28, 2018.
–ABSTRACT: The long?term viability of the Florida manatee is threatened in part by mortality from boat collisions. This study investigated manatee behavior during boat approaches to better understand factors that lead to manatee–boat collisions. Digital acoustic recording tags (DTAGs) and Argos?linked GPS tags were deployed on 18 manatees in southwest Florida, and boat traffic around them was mapped. Suites of manatee behavioral, environmental, and boat?related factors were recorded during opportunistic boat passes. We built generalized linear mixed models to determine which factors accounted for variation in occurrence, number, and timing of manatee behavioral changes during boat passes. Manatees responded to boats, changing their orientation, depth, and fluking behavior most often when a boat approached closely (<10 m). Manatees were also more likely to change their depth when not on a seagrass bed and when actively fluking before a boat pass. Boat speed did not affect the occurrence or intensity of manatee response. Compared to fast approaches, however, slower passes allowed the manatee more time to respond, and behavioral change occurred earlier relative to the time of the boat's closest point of approach. We conclude that faster boats likely pose a greater risk of collision with manatees than do slower boats.
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Bibliography and Index of the Sirenia and Desmostylia 