New insights about rearing conditions of Homarus gammarus larvae

Sá, Pedro Tiago Fonseca

http://hdl.handle.net/10400.8/1054

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Authors

Sá, Pedro Tiago Fonseca

Advisor(s)

Leandro, Sérgio Miguel Franco Martins

Marques, Sónia Cristina Ferreira Cotrim

Abstract(s)

The European lobster, Homarus gammarus, is considered one of the most important fishery resources in Europe, with high economic value and very appreciated seafood. However, in the last century their catch has been decreasing dramatically. Several restocking programs have been developed, but their larval development is quite demanding, hindering its cultivation. The present study aimed to contribute to increased knowledge about the larval development and growth of H. gammarus in order to optimize the protocols of captive cultivation. To fulfill these objectives, three complementary and distinct tests were performed, namely: (1) evaluate the effect of different lyophilized diets and live food, (2) evaluate the probiotic effect added to larval rearing and, finally, (3) define the relationship between the temperature effect and the larval development. The effects of the different factors analyzed in experiments were estimated by survival rates, specific growth rates and intermoult period, based on the individual responses of larvae. Each subject was monitored every 12 hours until the post-larvae (PL) stage or until its death. The fatty acid profile showed that the copepods (COP), dry copepods (DC) and dry wild zooplankton (DWZ) diets had high amounts of palmitic acid, DHA and EPA, essential fatty acids, compared with the live artemia nauplii (LAN) and dry artemia nauplii (DAN) diets. Simultaneously, these diets and larvae Zoea I showed similar fatty acid profile, showing once again, that they are the most suitable food for larval rearing of H. gammarus. The diet effect experiment, showed that the dry food, for this type of larval rearing, it is not suitable for H. gammarus larvae, resulting in 100% of mortality before reaching Zoea II, contrasting with the obtained results using live brine shrimp nauplii, with 4.17% survival to PL stage. The addition of probiotics in seawater, proved to be ineffective, with no differences in survival and growth rates, and intermoult period, compared to larvae grown without addition of probiotic in rearing water. In the temperature effect experiment, the larval survival rates decreased with larval development, except at 23°C, demonstrating wide variability. It would be expected that survival rates increased with temperature rising. However, this was not observed in our experiment. Higher survival rates were obtained at the intermediate temperature, i.e. 19°C. With regard to growth rates, the results showed that they decrease with larval development for all tested temperatures, and the temperature increasing did not increased the growth rates. The seawater rising temperature resulted in a decrease of intermoult period in all larval development stages and at all tested temperatures, ranging from 4.77 (Z1) to 16.5 days (Z3) at 16°C, whereas at 23°C, ranged from 3:02 (Z1) and 9.75 days (Z3). The results obtained are an extremely useful guide for future optimization of protocols on larval development of H. gammarus.

Description

Dissertação para obtenção do Grau de Mestre em Aquacultura apresentada à ESTM - Escola Superior de Turismo e Tecnologia do Mar do Instituto Politécnico de Leiria.