Estimating population parameters of longsnout seahorses, Hippocampus reidi (Teleostei: Syngnathidae) through mark-recapture

Abstract

Estimating population parameters is essential for understanding the ecology of species, which ultimately helps to assess their conservation status. The seahorse Hippocampus reidi is directly exposed to anthropogenic threats along the Brazilian coast, but the species still figures as Data Deficient (DD) at IUCN's Red List. To provide better information on the ecology of this species, we studied how population parameters vary over time in a natural subtropical environment. By combing mark-recapture models for open and closed populations, we estimated abundance, survival rate, emigration probability, and capture probability. We marked 111 individuals, which showed a 1:1 sex ratio, and an average size of 10.5 cm. The population showed high survival rate, low temporary emigration probability and variable capture probability and abundance. Our models considering relevant biological criteria illuminate the relatively poorly known population ecology and life history of seahorses. It is our hope that this study inspires the use of mark-recapture methods in other populations of H. reidi in a collective effort to properly assess their conservation status.Keywords: Capture Probability, Emigration Probability, Population Ecology, Robust Design, Survival Rate.Parâmetros populacionais são essenciais para compreender a ecologia das espécies, além de auxiliar a avalição do seu status de conservação. Dentre as espécies de cavalo-marinho que ocorrem no Brasil, Hippocampus reidi é a mais abundante, o que expõe suas populações a frequentes ameaças antropogênicas. Entretanto, esta espécie ainda consta como Deficiente em Dados (DD) na lista vermelha da IUCN. Considerando esta falta de informações sobre populações de H. reidi, utilizamos métodos de marcação e recaptura para avaliar como parâmetros de uma população de ambiente subtropical variam ao longo do tempo. Baseado em históricos de captura individuais, combinamos modelos de populações abertas e fechadas para estimar abundância, taxa de sobrevivência, probabilidade de emigração e probabilidade de captura. Ao todo, marcamos 111 indivíduos, em proporção sexual de 1:1, e tamanho médio de 10,5 cm. Esta população relativamente pequena apresentou alta taxa de sobrevivência, baixa probabilidade de emigração temporária e probabilidade de captura e abundância variáveis. A partir dos nossos modelos que consideraram critérios biológicos relevantes, fornecemos estimativas de parâmetros chave que auxiliarão a compreensão da ecologia e da história de vida de cavalos-marinhos. Nossa expectativa é que este método passe a ser amplamente utilizado em outras populações, em um esforço coletivo para avaliar o estado de conservação desta espécie.Palavras-chave: Desenho Robusto,

Seasonal and spatial variation in the reproductive biology of the dwarf seahorse Hippocampus zosterae

“…Other researchers working with larger Hippocampus spp. have had higher recapture rates in focal studies with tagged individuals that could be followed visually over a breeding season, with recapture rates as high as 8%–76% (Correia et al, ; Harasti et al, ; Siqueira et al, ). This individual focal approach is problematic in smaller Hippocampus spp., such as H. zosterae , that are found in dense seagrass beds with little to no visibility of the animals without collection methods such as a seine or push net.…”

Biology of Hippocampus patagonicus (Syngnathidae) in Brazilian waters. A species threatened with extinction, with suggestions for the conservation of seahorses in Brazil

“…The maximum height of a species does not appear to vary with latitude, although H. abdominalis exhibited greater height at higher latitudes, which may represent a response to temperature variation . In general, seahorses also do not display differences in size between the sexes Silveira, 2005;Pujol, 2014;Siqueira et al, 2017), as seen in the RS sample. Concerning weight, however, males are expected to be heavier than females, due to the development of the brood pouch (Lovett, 1969;Vincent, 1990;Filleul, 1996;Silveira, 2005;Silveira & Fontoura, 2010).…”

“…Among the three species of seahorses that occur in Brazil (Silveira et al, 2014), Hippocampus reidi Ginsburg, 1933, which inhabits marine and estuarine waters, is the most studied (Silveira, 2000(Silveira, , 2005Rosa __________________ Corresponding editor: Yassir Torres et al, 2007;Mai & Velasco, 2011;Silva et al, 2017;Siqueira et al, 2017). Regarding the other two species, Hippocampus erectus Perry, 1810 and Hippocampus patagonicus Piacentino & Luzzatto, 2004, little is known about life history characteristics in Brazilian waters, since none of them are found in estuaries, where seahorses are more accessible and study less expensive than at sea.…”

Life history and population dynamics of an endangered seahorse (Hippocampus capensis) within an artificial habitat

“…The distance moved by seahorses within a specific area, still following a mark‐recapture approach, can, however, provide some insights into site fidelity. Studies have found that seahorses show high site fidelity (Caldwell & Vincent, 2013; Curtis & Vincent, 2006; De La Nuez Hernández et al ., 2016; Harasti et al ., 2014b; Moreau & Vincent, 2004; Siqueira et al ., 2017). Similarly, this study found that H. capensis remained within a relatively small area (~70 m 2 ) for an extended period of time, which emphasises the need to protect this specific habitat from any localised impacts.…”