Manatee

The manatee (genus Trichechus) is a large aquatic mammal belonging to the order Sirenia and the family Trichechidae. While they are protected wildlife, in the context of agriculture in the Caribbean and Florida, they are considered a biological factor impacting hydraulic systems.

Physically, the animal has a massive, streamlined body of gray or brown color, reaching 3 to 4 meters in length. Their front limbs are transformed into flippers, and their tails are rounded, which distinguishes them from the dugong.

Adult individuals can weigh up to 500–600 kilograms. Their constant movement through narrow channels results in significant physical impact on both marginal and benthic vegetation.

Manatee sensory organs are adapted to murky water, allowing them to locate food sources effectively even in low visibility. Their high metabolism necessitates the consumption of huge amounts of biomass.

In agronomic practice, their activity is classified as a factor of anthropogenic-biological conflict in the operation of land reclamation facilities.

The primary diet of manatees consists of aquatic macrophytes, including species like water hyacinth, cattails, pondweed, and algae. They feed on both submerged and floating vegetation.

In agricultural regions, this leads to the destruction of natural plant filters that naturally purify water used for subsequent field irrigation.

Manatees can damage agricultural crops planted in fields adjacent to flooded zones and irrigation canals if access to the water is not restricted.

Damage to the food base in irrigation systems leads to the disruption of hydrodynamic regimes, which secondarily affects the yield of crops dependent on water quality and flow rates.

The damage also manifests as mechanical clogging of sluices with remnants of semi-digested vegetation, which complicates the maintenance of irrigation infrastructure.

Manatee activity is directly dependent on water temperature in reservoirs. During winter, they migrate to warmer waters, often concentrating near warm water discharges from power plants located next to agricultural lands.

The spring period is characterized by high feeding activity, which coincides with the phase of intensive vegetative growth of aquatic weeds in canals.

In summer, the animals disperse throughout the network of reclamation canals, increasing the area of their impact on irrigated farming ecosystems.

In autumn, the animals prepare for winter, which requires the accumulation of fat reserves, so feeding intensity remains high until the first cold spells.

Short-term spikes in activity occur after periods of heavy rainfall, when the influx of nutrients into the water triggers rapid growth of aquatic flora.

The first sign of the presence of animals is a sharp disappearance of dense aquatic vegetation patches in canal sections that were previously densely populated.

On the water surface, one can observe accumulations of fragmented plant debris that were not consumed but were mechanically damaged during the movement of large individuals.

The presence of the animals is accompanied by changes in water transparency due to the disturbance of bottom sediments as massive bodies move along the canal floor.

A characteristic sign is specific damage to benthic vegetation, appearing as trampled patches on the floor of the irrigation system.

The presence of deep furrows and suspended particles in irrigation networks, as well as premature wear of filter grates, often indicates recent herd activity in the sector.

Protection of facilities from manatees is complicated by their conservation status in most countries; therefore, only physical access restriction methods are used.

The installation of specialized barriers and grates at the entrances to irrigation canals prevents the entry of animals into critical zones of the reclamation system.

The use of acoustic deterrents allows for temporarily restricting the presence of animals in areas where repair or agricultural work in the water is being conducted.

The implementation of water usage rotation schedules allows for reducing the attractiveness of individual canal sections for animal feeding during their peak activity periods.

• Installation of mechanical barriers.
• Monitoring of migration routes.
• Acoustic deterrents.
• Restriction of nutrient discharges into water to reduce weed growth.