MARINE MAMMAL COMMISSION — Annual Report for 1992 
Flood Gates and Navigation Locks — Along 
Florida’s waterways, manatees sometimes are caught 
in the doors of flood gates or navigation locks and are 
crushed or drowned. Between 1977 and 1980, an 
average of eight such deaths was recorded annually. 
To address the problem, the programs for computer- 
operated gates were modified to eliminate narrow 
openings that might trap animals. For seven of the 
next ten years, deaths attributable to these structures 
declined to three or fewer per year, and it was 
thought that the problem was resolved. Higher 
mortality levels (seven deaths) in 1983 and 1988 were 
considered anomalous and due, at least in part, to 
system failures. In 1991, however, the previous 
mortality record due to gates and locks (nine deaths in 
1978) was equaled and some deaths occurred at 
modified structures that apparently were working 
properly. The responsible agencies therefore consti- 
tuted a task force to investigate the problem. 
During the Commission’s review, representatives 
of the South Florida Water Management District, the 
Department of Natural Resources, and the Fish and 
Wildlife Service reported on task force work to date. 
While the cause of the recent mortality increase is not 
fully understood, some deaths may be due to an 
increase in the frequency of gate openings caused 
inadvertently by previous modifications to maintain a 
minimum opening safe for manatees to pass through. 
Further adjustment of gate opening cycles are there- 
fore being tested. However, because this does not 
appear to be the only factor involved, other solutions 
are being reexamined. Sonar detection devices to 
alert operators when animals are near gates are being 
tested. Other solutions under discussion include the 
installation of slotted gates and automatic reverse 
mechanisms similar to safeguards on elevator doors. 
Program Review Follow-Up 
After its manatee program review, the Marine 
Mammal Commission consulted with its Committee of 
Scientific Advisors and took the following actions: 
Recovery Program Priorities and Support — 
When the Service adopted the revised Manatee Recov- 
ery Plan in 1989, the Commission reviewed its 
provisions and wrote to the Service on 2 March 1990, 
recommending minimally acceptable levels of funding 
and personnel needs through Fiscal Year 1995. 
Because it is difficult to predict rates of progress and 
new developments several years in advance, such 
assessments need to be reexamined periodically. A 
major objective of the Commission’s 1992 program 
review, therefore, was to reexamine its earlier recom- 
mendations. In light of what was learned, the Com- 
mission wrote to the Service on 17 June 1992. 
In its letter the Commission noted that substantial 
cooperative efforts had been initiated in the past three 
years and appeared to be addressing the critical issues. 
It also noted that this progress was, in no small 
measure, directly attributable to the revised Recovery 
Plan and the work of the Fish and Wildlife Service 
staff. With regard to future research and management 
work by the Service, the Commission’s 17 June letter 
updated its March 1990 recommendations on priority 
task and resource needs. 
For Service research, the Commission noted that 
priority needs include maintaining recently established 
telemetry capabilities, developing methodology and 
programs to monitor the condition of essential mana- 
tee feeding habitats, and pursuing certain new manatee 
life history work (including manatee age determination 
research, aerial photogrammetry to define manatee 
population size/age class structure, studies of the 
nutritional value of food plants, and survival rate 
estimation). The Service’s manatee research is carried 
out by the National Ecology Research Center’s Sirenia 
Project, based in Gainesville, Florida. To meet its 
manatee research needs, the Commission recommend- 
ed that the Sirenia Project be supported at the follow- 
ing levels over the next five fiscal years: $704,000 in 
1993; $693,000 in 1994; $689,000 in 1995; $701,000 
in 1996; and $669,000 in 1997. 
Among its priority management needs, the Com- 
mission noted that the Service needed to continue 
consultations with the Corps of Engineers and other 
agencies On activities affecting manatees; assist State 
and county officials in developing local manatee 
protection plans and rules; develop and implement 
rules for new manatee sanctuaries and refuges; assess 
the incidence of and possible solutions to manatee 
mortality caused by large vessels; pursue steps to 
