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Abstract(s)
O cavalo-marinho de focinho comprido (Hippocampus guttulatus) é uma espécie típica de climas temperados, incluindo o mar Mediterrâneo, e a sua maior população encontra-se no sul de Portugal, nomeadamente na Ria Formosa.
Devido à sua elevada população, eram referidos como associados a habitats de ervas marinhas, mas manifestam presentemente preferência as macroalgas do género Codium sp., nas quais se prendem com a sua cauda preênsil que os protege das fortes correntes.
Apresentando uma biologia muito particular (cuidados parentais elevados, fracos nadadores, etc.) sofrem múltiplas ameaças presentes nos seus habitats, tanto de origem natural como antropogénica, estando classificados como “data deficient/informação suficiente pela IUCN, 2014.
Durante todo o seu ciclo de vida, a alimentação de Hippocampus guttulatus é constituída principalmente por crustáceos. Na fase inicial da vida, alimentam-se de presas de pequenas dimensões, frequentemente copépodes. Posteriormente, passam a ingerir presas de maior tamanho, onde se incluem, por exemplo, anfípodes, misidáceos e pequenos camarões. Apesar do seu aparente e normal comportamento passivo, os cavalos-marinhos são predadores ativos com a capacidade e necessidade de ingerir volumes significativos de alimento, que atingem valores maiores nas suas primeiras semanas de vida.
No entanto, a conjugação entre o comportamento de escolha de habitat e sua ecologia alimentar fazem com que habitem áreas específicas da Ria Formosa, nas quais ocorrem em maior número e condicionaram o alimento disponível.
Deste modo e com a realização deste trabalho, pretende-se avaliar em ambiente controlado (cativeiro) o consumo diário de alimento pelos cavalos-marinhos Hippocampus guttulatus, e a forma como o consumo afeta o seu índice de condição física. O trabalho envolveu a comparação com a condição física de cavalos-marinhos de três locais de meio natural: Culatra (Local 1), Bóia (Local 2) e Remanço (Local 3), relacionando-a com a disponibilidade de presas presentes em cada local.
O trabalho de campo foi realizado no período de início de Outono (Outubro de 2014). A experiência em cativeiro foi realizada nos meses de Março e Abril de 2015, com o objetivo de aferir e avaliar a quantidade de alimento necessário para a manutenção de uma condição física ótima, informação essa que foi comparada com a informação recolhida em ambiente natural. Os cavalos-marinhos foram medidos e pesados semanalmente de forma a avaliar a evolução do seu peso e crescimento em função do alimento que lhes era fornecido. Este alimento foi contabilizado diariamente.
Com os dados provenientes das medições do comprimento, os indivíduos foram classificados como pequenos e grandes, informação essa relacionada com o consumo diário de misidáceos de que ambas as classes se alimentavam, sendo que, como expectável, os pequenos comeram menos e os grandes mais. Esta informação também foi relacionada com o Índice de consumo alimentar (FCR) e a Taxa de Crescimento Específica (SGR) dos cavalos-marinhos.
Por fim e através dos dados resultantes das medições de peso e comprimento foi calculado o índice de condição física de todos os cavalos-marinhos de cativeiro e procedeu-se à comparação com os índices de condição física dos cavalos-marinhos de meio natural. No geral, os cavalos-marinhos de meio natural apresentaram uma condição física melhor que os de cativeiro, com algumas variações entre os locais amostrados, o que será devido a diferenças na abundância de presas e nas estruturas de fixação disponíveis, essenciais à estabilização destes peixes nas correntes oceânicas.
Sendo assim e como os cavalos-marinhos se encontram em estado de vulnerabilidade na Ria Formosa, este estudo poderá contribuir para a conservação das suas populações no futuro e criar em cativeiro as boas condições que o meio natural lhes proporciona.
The seahorse long snout (Hippocampus guttulatus) is typical specie of temperate climes, such as Mediterranean, and whose biggest population is located in South of Portugal, in Ria Formosa. Due to its high population, they were associated to seagrass habitats, although they are also showing preference in macroalgae of the type Codium sp., in which they attach themselves with their prehensile tail to be protected from the strong ocean currents. They present a very particularly biology (parenthood caring, weak swimmers and so on) and for this reason they suffer a large number of menaces in their own habitats, not only from natural source, but also by human. They are classified as “data deficient” by the IUCN, 2014. Through their life cycle, the eating of Hippocampus guttulatus is made up of crustaceans. However, in their initial life, they feed themselves with small preys, most of them copepod. Afterwards, they begin to take bigger preys, for instance, amphipods, mysids and small shrimps. Apparently they are a very pacific animal, but they are actually active hunters and they have the ability and the necessity of eating great volumes of food, which become even bigger in their first weeks of life. Nevertheless, the combination between their behaviour and they eating ecology makes possible the existence of several species, which also can diminishes the food available. This work aims to evaluate in a controlled environment (Captivity) the daily consumption made by the seahorses Hippocampus guttulatus, and the way it affects their physical condition. The work has involved the cooperation with the seahorses’ physical condition in three different natural spots: Culatra (Spot 1), Bóia (Spot 2) and Remanço (Spot 3). They were all related with the availability of the preys nowadays. The fieldwork was made in the beginning of October 2014. The captivity experience was made between March and April 2015 and it aimed to evaluate the necessary maintenance of eating in order to keep the seahorses in their best shape. This information was compared to the ones who lived in their natural environment. The seahorses were measured and weighted weekly so it became possible to register their evolution according to the food they were eating. The eating was controlled daily. With this data from length, all the individuals were classified as small and big, depending on their daily eating of mysids both species were getting. The expected happened: the little ones ate less and the big ones more. This information was also related with the Food Conversion Rate (FCR) and the Specific Growth Rate (SGR) of the seahorses. Finally, resuming the data from the measures lenght and weight, it was calculated the rate of the physical condition of all captivity and the natural environment seahorses. In general, the natural environment seahorses present a much better physical condition than the ones kept in captivity. It also showed some variety among the places tested, due to the different abundance of prey and holdfasts to be fixed, which are essential to the stability of these fishes in the oceanic currents. The seahorses are in a state of vulnerability in Ria Formosa and this study could be helpful to the conservation of their populations in the future and to create the same good conditions as the natural environment in captivity.
The seahorse long snout (Hippocampus guttulatus) is typical specie of temperate climes, such as Mediterranean, and whose biggest population is located in South of Portugal, in Ria Formosa. Due to its high population, they were associated to seagrass habitats, although they are also showing preference in macroalgae of the type Codium sp., in which they attach themselves with their prehensile tail to be protected from the strong ocean currents. They present a very particularly biology (parenthood caring, weak swimmers and so on) and for this reason they suffer a large number of menaces in their own habitats, not only from natural source, but also by human. They are classified as “data deficient” by the IUCN, 2014. Through their life cycle, the eating of Hippocampus guttulatus is made up of crustaceans. However, in their initial life, they feed themselves with small preys, most of them copepod. Afterwards, they begin to take bigger preys, for instance, amphipods, mysids and small shrimps. Apparently they are a very pacific animal, but they are actually active hunters and they have the ability and the necessity of eating great volumes of food, which become even bigger in their first weeks of life. Nevertheless, the combination between their behaviour and they eating ecology makes possible the existence of several species, which also can diminishes the food available. This work aims to evaluate in a controlled environment (Captivity) the daily consumption made by the seahorses Hippocampus guttulatus, and the way it affects their physical condition. The work has involved the cooperation with the seahorses’ physical condition in three different natural spots: Culatra (Spot 1), Bóia (Spot 2) and Remanço (Spot 3). They were all related with the availability of the preys nowadays. The fieldwork was made in the beginning of October 2014. The captivity experience was made between March and April 2015 and it aimed to evaluate the necessary maintenance of eating in order to keep the seahorses in their best shape. This information was compared to the ones who lived in their natural environment. The seahorses were measured and weighted weekly so it became possible to register their evolution according to the food they were eating. The eating was controlled daily. With this data from length, all the individuals were classified as small and big, depending on their daily eating of mysids both species were getting. The expected happened: the little ones ate less and the big ones more. This information was also related with the Food Conversion Rate (FCR) and the Specific Growth Rate (SGR) of the seahorses. Finally, resuming the data from the measures lenght and weight, it was calculated the rate of the physical condition of all captivity and the natural environment seahorses. In general, the natural environment seahorses present a much better physical condition than the ones kept in captivity. It also showed some variety among the places tested, due to the different abundance of prey and holdfasts to be fixed, which are essential to the stability of these fishes in the oceanic currents. The seahorses are in a state of vulnerability in Ria Formosa and this study could be helpful to the conservation of their populations in the future and to create the same good conditions as the natural environment in captivity.
Description
Tese de mestrado em Ecologia Marinha, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2015
Keywords
Hippocampus guttulatus Índice de condição física Abundância de presas Cativeiro Ria Formosa Teses de mestrado - 2015