Methods Used During Gross Necropsy to Determine Watercraft-Related Mortality in the Florida Manatee (Trichechus Manatus Latirostris)

Abstract

Between 1993 and 2003, 713 (24%) of 2,940 dead Florida manatees (Trichechus manatus latirostris) recovered from Florida waters and examined were killed by watercraft-induced trauma. It was determined that this mortality was the result of watercraft trauma because the external wound patterns and the internal lesions seen during gross necropsy are recognizable and diagnostic. This study documents the methods used in determining watercraft-related mortality during gross necropsy and explains why these findings are diagnostic. Watercraft can inflict sharp- and blunt-force trauma to manatees, and both types of trauma can lead to mortality. This mortality may be a direct result of the sharp and blunt forces or from the chronic effects resulting from either force. In cases in which death is caused by a chronic wound-related complication, the original incident is usually considered to be the cause of death. Once a cause of death is determined, it is recorded in an extensive database and is used by Federal and state managers in developing strategies for the conservation of the manatee. Common sequelae to watercraft-induced trauma include skin lesions, torn muscles, fractured and luxated bones, lacerated internal organs, hemothorax, pneumothorax, pyothorax, hydrothorax, abdominal hemorrhage and ascites, and pyoperitoneum.

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

“…Após diversas avaliações de peixes-boi envolvidos em colisões com embarcações na Flórida, as diferentes formas de lesões encontradas foram atribuídas ao tipo da hélice (diâmetro, rotação e ângu-lo), modelo de casco e a postura do animal no momento da colisão ( Pitchford et al 2001, Ligtsey et al 2006, Rommel et al 2007). Estas constatações inerentes às características das embarcações e a posição do animal na ocasião do atropelamento, podem estar relacionados às diferentes apresentações dos ferimentos constatados com os peixesboi marinhos deste estudo.…”

Serum Amyloid A (SAA) as a Biomarker of Chronic Infection Due to Boat Strike Trauma in a Free-ranging Florida Manatee (Trichechus manatus latirostris) with Incidental Polycystic Kidneys

“…Up to 33% of manatee mortality is a result of human interaction; of these, watercraft strikes are the most common cause (Lightsey et al, 2006). Up to 97% of manatees in a USGS photo identification database for manatees have multiple scar patterns that indicate nonlethal encounters with propellers and boat skegs (O'Shea et al, 2001).…”

REVIEW: Slower boat speeds reduce risks to manatees

“…The speed at which a propeller is turning may also affect the resulting damage in that fast spinning propeller blades may cut through the skin more readily, while slower ones may cause more impact trauma (Lightsey et al 2006, Rommel et al 2007. As a result, injuries caused by the propeller blades may or may not be less severe if the boat is traveling at a slower speed.…”

“…The same cannot be said for the severity of injuries caused by blunt force trauma (i.e. non-cutting injuries), which can be caused by a boat's hull, keel, rudder, lower unit (including skeg), propeller (non-cutting), or other feature that extends below the water surface (Pitchford et al 2005, Lightsey et al 2006, Rommel et al 2007). The severity of blunt force injuries is directly related to the mass/weight of the boat and its speed at the time of collision, and blunt force injuries have caused more than half of the documented boat-related manatee deaths.…”

“…The severity of blunt force injuries is directly related to the mass/weight of the boat and its speed at the time of collision, and blunt force injuries have caused more than half of the documented boat-related manatee deaths. Lightsey et al (2006) reported that 58% of the boat-related deaths between 1993 and 2003 were the result of blunt force trauma, as compared to 32% that were caused by sharp force trauma (including propeller, skeg, and rudder cuts) and 10% that were caused by a combination of blunt force and sharp force trauma.…”