Estudo populacional do cavalo-marinho HIPPOCAMPUS REIDI GINSBURG, 1933 (TELEOSTEI: SYNGNATHIDAE) em dois estuários cearenses

Abstract

Seahorses are bony fishes included in the Hippocampus genus. Many aspects of their biology make them extremely vulnerable to overexploitation. The intense commerce and habitat degradation allied to their biology, contribute to the decline of their populations. Considering the level of threat to these animals around the world and their relevance as a “flagship species”, studies concerning their ecology are extremely important. The purpose of this study was to determine spatial and temporal distribution of the abundance of Hippocampus reidi at the Pacoti and Malcozinhado rivers, registering also other ecological aspects of the species. Transects with an area of 100 m2 were conducted along the riverbanks. Each river was divided into two stations with increasing distances from the sea. The mean density determined was of 0,008 individuals/m2. The Pacoti River showed a significantly higher mean density when compared to the Malcozinhado River (p=0,019). There was no difference between the two stations in the Pacoti River, while in the Malcozinhado an evident difference was noticed. Both rivers showed a decreasing trend in the densities during the study, but the differences were not significant (p=0,33 and p=0,41, for Pacoti and Malcozinhado, respectively). No seazonal variation in abundance was determined. The animals from the Pacoti River were significantly higher than those from the Malcozinhado (p=0,027). Sez ratio was 1:1, and males were higher on average than the females (p=0,013). Black and brown colored seahorses were more abundant than other colors. The roots of Laguncularia racemosa were preferably chosen as anchoring substrata. The present study showed that environmental differences on the estuaries, such as mangrove areas, discharge volume and vulnerability to impacts might cause differences in the abundance of H. reidi. The adequate management of this threatened species depend strongly on a good knowledge of its ecology.