Estrutura populacional do cavalo-marinho Hippocampus reidi em um estuário do semiárido brasileiro, com recomendações para o manejo sustentável

Abstract

Seahorse populations are threatened due to degradation of their natural habitats, bycatch, use of individuals in traditional beliefs and aquarism. The specie Hippocampus reidi is the only one occurring in the State of Ceará, classified as vulnerable according to Ordinance No. 445 of Ministry of the Environment, of December 17, 2014. The aim of this study was to characterize the population structure of H. reidi in the Pacoti River estuary, Ceará, and to propose suggestions for the sustainable management of the population. The research was carried out between December 2017 and October 2018, in eleven sampling areas formed by variable length transects. The size, sex, colour and support substrate were obtained from everyone. The population density was estimated and the effect of the salinity and rainfall variables on the density was evaluated. Sexual proportion, height, coloration and anchorage substrate were also analysed. Salinity, rainfall and size of the photic zone were used to characterize the habitats. Through the 11 months of sampling, there were a total of 231 records of H. reidi individuals, with a mean density of 0,0389 ind.m‾ ² (± 0.0277). No influence of the salinity and rainfall variables on the density of seahorses in the estuary of the Pacoti River was identified. The sexual ratio was 1:1. Sixty males were pregnant (56.60%), and a correlation between the proportion of pregnant males and rainfall was identified. The mean size of individuals of H. reidi was 12.69 cm (± 1.98). The orange staining pattern was dominant (45.03%). White mangrove (Laguncularia racemosa) was recorded as the most often anchorage substrate (38.53%), followed by sand (23.38%) and red mangrove (Rhizophora mangle; 16.88%). In conclusion, the population of H. reidi in the Pacoti River estuary has higher density and body size than in previous studies and has been reproducing throughout the year, with a predominance of vibrant colours and preferences for more complex anchorage substrates. The spatial-temporal density of the species in the Pacoti estuary was not influenced by salinity and rainfall. The present study is a tool that evaluates the potential of the population for commercial exploitation in a sustainable way, with adequate management of the species and its ecosystem.