Home ranges and movement patterns of the marine tucuxi dolphin, Sotalia fluviatilis, in Baía Norte, southern Brazil

Autor: Paulo A. C. Flores, Mariel Bazzalo
Rok vydání: 2004
Předmět:
Zdroj: Latin American Journal of Aquatic Mammals. 3
ISSN: 2236-1057
1676-7497
Popis: 2 Abstract - Marine tucuxi dolphins (Sotalia fluviatilis) studied in Baia Norte, southern Brazil, exhibited very small overall home ranges with daylight movements in consistent water depths of around 3m. Mean overall home range areas calculated through two methodologies were similar, measuring 13.38km² ± 1.92 using the Minimum Convex Polygon method and 15.22km² ± 0.66 through the kernel estimator. Mean core areas calculated by kernel were extremely small (mean = 1.49km² at 50% UD (utilization distribution) and 0.87km² at 25% UD levels). The geographical distributions of home ranges and core areas overlapped extensively at both 50% UD and 25% UD. Daylight movements ranged from 0.16 to 28.97 km/day (mean = 5.65 ± 0.56km/day, SD = 5.36) with mean minimum rate of movement of 2.6 ± 0.2km/h (SD = 2.02). Daylight movement patterns varied seasonally with higher values of distance moved and rate of movement in winter and winter and autumn, respectively. The marine tucuxi home ranges and daylight movement patterns presented here are smaller than much of what is known for other coastal small cetaceans. The percentage of overall home range within the limits of a protected area designated for the tucuxis could be considered moderate to high depending on the estimator used (54.06% or 5.9km² by MCP and 74.71% or 11.35km² using the kernel). Nevertheless, core areas are completely within the protected area. Conservation implications of these findings include the need to: (i) create a buffer zone to the south of the existing protected area which will encompass the overall home range of the tucuxis; (ii) establish constant, adequate enforcement of fishery and boat traffic regulations in the core areas; and (iii) regulate boat traffic and aquaculture farming in important areas which are not yet subject to specific regulations. Resumo - Tucuxis marinhos (Sotalia fluviatilis) estudados na Baia Norte, sul do Brasil, apresentaram areas de vida bastante pequenas com movimentos diurnos em profundidades constantes proximas de 3m. A media das areas de vida geral calculadas atraves de dois metodos foram similares, medindo 13.38km² ± 1.92 usando o Minimo Poligono Convexo e 15.22km² ± 0.66 pelo estimador kernel. A media das areas de vida principais calculadas pelo metodo kernel foram extremamente pequenas (media = 1.49km² a 50 % UD e apenas 0.87km² a 25% UD (niveis de utilizacao de distribuicao)). Houve intensa sobreposicao da distribuicao geografica das areas de vida gerais e principais tanto aos niveis de 50% UD quanto de 25% UD. Os movimentos diurnos variaram de 0.16 a 28.97km/dia (media = 5.65 ± 0.56km/dia, DP = 5.36) com taxa minima de movimento media de 2.6 ± 0.2km/h (DP = 2.02). Os padroes de movimentos diarios variaram sazonalmente sendo os maiores valores de distância percorrida e taxa de movimento encontrados no inverno e no inverno e outono, respectivamente. Os valores de areas de vida e movimentos diurnos apresentados sao menores do que muitos dos valores conhecidos para outros pequenos cetaceos costeiros. A porcentagem das areas de vida geral dentro dos limites marinhos da unidade de conservacao criada para proteger os tucuxis marinhos no local pode ser considerada moderada a alta, dependendo do estimador de area de vida considerado (54.06% ou 5.9km² pelo Minimo Poligono Cconvexo e 74.71% ou 11.35km² usando o kernel). De qualquer forma, as areas de vida principais estao completamente dentro da unidade de conservacao. Implicacoes para a conservacao dessa especie na area de estudo incluem a necessidade de: (i) criar um zona tampao ou de amortecimento ao sul dos atuais limites da unidade conservacao, de forma a incluir toda a area de vida dos tucuxis marinhos; (ii) estabelecer uma fiscalizacao adequada e constante da pesca e do trafego de embarcacoes nas areas de vida principais dos tucuxis; e (iii) regulamentar o trafego de embarcacoes e a maricultura em areas importantes ainda nao sujeitas a legislacao e regulamentacao especificas.
Databáze: OpenAIRE
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