Effect of salinity on three tilapia (Oreochromis sp.) strains: hatching rate, length and yolk sac size

Document Type: Primary Research paper

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Abstract

Salinity is an important factor for fish embryonic development. In tilapias, tolerance to salinity at any age is influenced by physiological responses of each species and can be transferred into hybrids. We evaluated the differences with respect to hatching rate (HR), total length at hatching (TL) and yolk sac area (YS) in eggs obtained from breeders kept at 0‰ and directly transferred to salinities of 0, 5, 15, 25, 35, 45, 55 and 65 ‰, after egg collection of the following varieties of tilapia: red tilapia (Oreochromis sp) (RT), a hybrid 1 (H1) obtained from the cross of Nile tilapia (male) X red tilapia (female) and a new red synthetic tilapia as hybrid 2 (H2): Pargo-UNAM. The results showed that salinity above 35-45‰ significantly reduced hatching rates in H1 and H2 until reaching 0% HR at 55 and 65‰, while RT eggs hatched at all salinities. TL decreased significantly >35‰, with an interval with no differences between 0-25‰. YS also decreased >25‰ for H1 and H2, with an overall smaller size for RT. These results provide an insight of morphological differences related to salinity tolerance at early stages, as smaller hatching size and increased yolk sac utilization at salinity >35‰.

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