Paraíba Coast IMMA

Criterion A – Species or Population Vulnerability

Populations of West Indian manatees (Trichechus manatus) are sensitive to changes in coastal environments, and are threatened by entanglement in fishing gear, boat strikes, and primarily by the loss of habitat (Borges et al., 2007; Meirelles, 2008). In Brazil, the frequent occurrence of stranded manatees, in particular neonates, reflects anthropogenic threats including accidental capture in fishing nets, and the degradation of the estuaries in which the species breeds (Parente et al., 2004; Meirelles et al., 2014 ; Aquasis, 2016; Medeiros et al., 2021).

Given the considerable pressures on the surviving wild populations, West Indian manatees are considered one of the Brazilian aquatic mammals most threatened with extinction (MMA, 2022), with a total population in the Brazilian Northeast estimated to be just over 1,000 individuals (Alves et al., 2015). The species is globally classified as “Vulnerable” (Deutsch et al. 2008) and nationally listed in Brazil as “Endangered” (MMA, 2022). However, recently an independent assessment classified the species as “Critically Endangered” in Brazil (Meirelles et al., 2022).

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

Aerial surveys and other studies indicate that the Paraiba coast hosts relatively high densities of manatees in comparison with other areas of Brazil’s coastline (e.g. Alves et al., 2015).  However, there are indications that the population has been reduced over the years due to various anthropogenic factors (Lima et al., 2011; Alves et al., 2013; Alves et al., 2015).

Since the first manatee surveys conducted in Brazil in the 1980s, the estuaries of the Mamanguape and Miriri Rivers, both contained within this IMMA have consistently registered the highest frequency of occurrence and abundance of the species. Albuquerque and Marcovaldi (1982) indicated that the estuary of the Mamanguape River, in Paraíba state, hosted the highest manatee concentration on the northeastern coast in Brazil, where groups of up to 15 animals were documented near the mouth of the river and along the coast.

In addition to the native manatee populations, the region is a release area for rehabilitated manatees. Radio and satellite tracking of some these released individuals provides insight into the home ranges and fidelity to sites in the region (Normande et al., 2016; dos Santos et al., 2022). Home range size of tracked individuals was 2.56 – 42.07 km², small enough to be contained within the IMMA. The longest distance travelled from the coastline upriver was 14.24 km and the longest distance offshore was only 0.93 km (dos Santos et al., 2022).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

The estuaries of the Mamanguape and Miriri rivers are considered relevant areas for the reproduction of manatees, as they have reefs that provide more sheltered environments with shallow waters (Silva et al., 2011). Births generally occur between October and March, when sightings of females with calves are frequent (Lima et al., 2011).  Mating is more frequently observed during the dry period (austral summer) (Balensiefer et al., 2017).

Sub-criterion C2: Feeding Areas

Dos Santos (2020) characterized the home range areas of rehabilitated manatees released in this region. The results showed that manatees exhibited a preference for sites shallower than two meters, with food resources and freshwater availability.

The presence of reefs covered with marine algae is a determinant factor in the occurrence of the manatee. They were sighted feeding on algae that grow over the reefs close to beaches that were of high energy during high tide. They occur in depths of 0.4 to 3.8 m; the distance from the beach varies according to the tide level (Paludo & Langguth, 2002).

Paludo (1998) recorded, through direct observations, the manatees feeding on banks of algae, where a large proportion of red algae were recorded. Borges et al. (2008) analysed stomach content samples from manatees accidentally caught in the states of Rio Grande do Norte, Paraíba and Alagoas, in addition to samples of faeces from released and wild animals in northern Paraíba. A wide range of items was recorded, such as seagrass, algae and mangroves. The authors draw attention to the significance of red algae found in the contents studied. These findings support the direct observations made by Paludo (1998). These algae appear to be abundant on the coast of Paraíba, where the majority of the samples studied came from. The findings indicate that seaweeds are an important item in the diet of the species in the region, different from what has been recorded in other places, where this item seems to be consumed occasionally or accidentally along with seagrass.