Ecologia comportamental do cavalo-marinho brasileiro Hippocampus reidi Ginsburg, 1933 em recifes rochosos do estado do Rio de Janeiro

Abstract

Seahorses are teleost fishes which present movement limitation, due to low propulsion generated by dorsal fin and also to presence of a prehensil tail. This difficulty provides a sedentary behavior to species. Increase of male body mass during breeding season probably also provides a greater inactivity during this period. Greater inactivity leads to territorial defense behavior for resourses like food, partner or / and offspring protection. Distribution of H. reidi in Rio de Janeiro state is unknown. This study aims to: I) describe distribution and relate some environmental variables, to density of H. reidi; II) Evaluate the inactive behavior; III) verify and describe intra-specific and intra-sexual territorial behavior of male.This study was accomplished along Rio de Janeiro state coast. Behavioral aspects and distribuiton of H. reidi were studied by snorkeling and visual census. Distribution of seahorses was determined by transects of 20 x 5 m. Percent of substrate cover, dissolved oxygen and temperature were taken in field and salinity and turbidity were analyzed in laboratory. Activity was verified by focal method of one hour per individual. Territorial defense experiment was tested by experiments in situ of translocation of breeding and non-breeding male to territories of other breeding and non-breeding males, one by one. Seahorse distribution was patchy along state coast, presenting a mean density of 0,007 ind.m-2. Factors measured did not explain different densities among areas (p = 0,5284; r2= 0,2188; F = 1,0414). The following site presented higher density (0,01 ind.m-2): Praia de Araçatiba. Male in general appeared to be more inactive than female (KW=54,561; p<0,001), but breeding male presented the most inactive behavior. A great relation was found between IGSa (adapted Gonadossomatic Index) and male inactivity (r=0,81; p < 0,001). Exposure was described as territorial behavior exibited by the study species. Breeding male exibited territorial behavior in relation to other male (KW=46,00; p < 0,0001). Relation between IGSa and interaction time was not significative, showing that both, brood pouch size and individual size, did not present strong influence over interaction (r = 0,0539; p=0,6349; n = 80). According to data it was possible to conclude that male seahorses are more inactive than female and brood pouch increases degree of inactivity. Male in advanced breeding stage were more territorial. Species distribution occurred along Rio de Janeiro coast, showing a large distribution in state with low density. Species distribution is patchy and apparently still can not be explained by none studied factor.