Preliminary evidence that boat speed restrictions reduce deaths of Florida manatees

  • Published source details Laist D. & Shaw C. (2006) Preliminary evidence that boat speed restrictions reduce deaths of Florida manatees. Marine Mammal Science, 22, 472-479.


This study is summarised as evidence for the following.

Action Category

Set and enforce vessel speed limits

Action Link
Marine and Freshwater Mammal Conservation
  1. Set and enforce vessel speed limits

    A before-and-after study in 1986–2005 at a creek and canal in the Indian River estuarine system, USA (Laist & Shaw 2006) reported that after setting vessel speed limits in ‘zones’, a similar number of Florida manatee Trichechus manatus latirostris deaths were recorded to before the speed limits, but setting and enforcing speed limits throughout all areas resulted in fewer manatee deaths. Results are not based on assessments of statistical significance. Average numbers of manatees killed by vessels were similar before (1.8 manatees/year) and after (1.8–2.1 manatees/year) vessel speed limits were introduced to specific zones. Fewer manatees were killed by vessels (average 0.3 manatees/year) after speed limits were introduced and enforced by patrols in all areas. Year-round speed limits (8–11 km/h) were set within specific zones in 1990 and 1994, although low compliance was reported (see original paper for details). In 2002, the creek and canal were designated as manatee refuges and year-round speed limits (8–11 km/h) were set throughout. Patrolling enforcement officers issued warnings and speeding tickets in 2002–2005. Manatees killed by vessels were recorded within the creek, canal and adjacent waters during five years before speed limits were set (1986–1990), 13 years after speed limits were set in zones (1990–2002) and four years after speed limits were set and enforced in all areas (2002–2005).

    (Summarised by: Anna Berthinussen)

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