FORENSIC METHODS FOR CHARACTERIZING WATERCRAFT FROM WATERCRAFT‐INDUCED WOUNDS ON THE FLORIDA MANATEE (TRICHECHUS MANATUS LATIROSTRIS)

Abstract

Watercraft‐related mortality represents 1,253 (24.9%) of 5,033 Florida manatee (Trichechus manatus latirostris) deaths recorded between 1 January 1979 and 31 December 2004. Wound patterns generated by collisions with watercraft are diagnostic. Sets of cuts and scrapes that are roughly equidistant and perpendicular to the direction of vessel travel are consistent with lacerations made by propeller blades. From these lesions, estimates of propeller diameter, pitch, rotation, and direction of travel may be obtained. Considerable overlap of propeller sizes and pitches on different size vessels, common use of counter rotation propellers, and numerous other complicating factors may confound efforts to accurately predict vessel size and type from propeller wounds. Of the more than one million watercraft registered in Florida, 98% are ≤12.2 m (40 ft), yet watercraft 5.3–36.6 m (17.5–120 ft) are known to have killed manatees. Analysis of a 5‐yr subset of mortality data suggests that a disproportionate number of propeller‐caused watercraft‐related mortalities could be attributed to propeller diameters ≥43.2 cm (17 in.), inferring that these were caused by watercraft ≥12.2 m (40 ft).

Embarcações motorizadas: uma ameaça aos peixes-boi marinhos (Trichechus manatus) no Brasil

“…Este fato vem sendo um fator de preocupação na Flórida (Estados Unidos), onde ao longo dos anos os casos de atropelamentos aumentaram, sendo estas circunstâncias responsáveis por grande parte das mortalidades com esta espécie (Beck et al 1982, O'Shea et al 1985, Nowacek et al 2004, chegando a representar aproximadamente 25% (n = 1.253) do total das 5.033 mortes registradas entre um de janeiro de 1979 a 31 de dezembro de 2004 (Rommel et al 2007) e mesmo quando estes indivíduos não vêm a óbito em muitas situações apresentam mutilações graves e permanentes (Powell 2002, Yan et al 2006. Para assegurar a integridade dos peixes-boi marinhos no Brasil, algumas medidas foram criadas e dentre estas, a adoção de instrumentos legais, que restringem a navegação de embarcações motorizadas em áreas de grande utilização destes animais (Brasil 1993(Brasil , 1997.…”

Swimming kinematics of the Florida manatee (Trichechus manatus latirostris): hydrodynamic analysis of an undulatory mammalian swimmer

“…Unless migrating, speed and thrust are less important to the manatee that has very few threats outside of humans (Reynolds and Odell, 1991;Gerstein, 2002;Reynolds and Powell, 2002;Rommel et al, 2007). The majority of their daily activities involve feeding on sessile aquatic plants and resting (Hartman, 1979;Best, 1981;Bengston, 1983;Etheridge et al, 1985;Marshall et al, 2000).…”

Diving behavior of female loggerhead turtles (Caretta caretta) during their internesting interval and an evaluation of the risk of boat strikes

“…Increasing water traffic is associated with the increasing probability of boat impacts on sea turtles in Florida (Fig. 4) as has been similarly documented for manatees (Rommel et al, 2007). The trends of increasing boat impacts on sea turtles prompt the present study to evaluate the risk to loggerheads from recreational water crafts and boat races in a region occupied by a large nesting aggregation of southwest Florida loggerhead turtles.…”

“…According to a study of 1,500 recreational boat designs by Mellor (1992) % of the vessels were 15-20 m in length (this was the highest percentage in the survey) (Thomas and Stratis, 2002). And in another study (Rommel et al, 2007) the far majority (98%) of boats operating in Florida waters are less or equal to 12.2 m. Thus, the maxi-mum draft of a powerboat of 12.2 m total length is 1.5 m and a boat of 15 m in length would have a maximum draft of 0.77m (see Fig. 9 for calculation).…”

“…Ninety-eight percent of boats registered in the state of Florida are less than or equal to 12.2 meters (40 ft) in length (Rommel et al, 2007). To understand why turtles are struck by boat hulls and propellers requires knowledge of boat draft.…”