Abstract
The global trade in seahorses is increasing and new rearing techniques are currently available for a few species. One of the main bottlenecks in seahorse production is reproductive success, which is dependent upon the administration of high quality diets to breeders. However, little is known about the most adequate diets, on how they should be administered and on how they might affect newborn performance. In this study, three homogeneous groups of adult seahorses Hippocampus guttulatus were maintained in captivity. Each group was fed on one of the following diets since the onset of the breeding period: unenriched adult Artemia (Diet A), unenriched adult Artemia and mysidaceans (Diet AM) and mysidaceans (Diet M). As a positive control, a wild pregnant male was used. The mixed diet AM provided the highest overall breeding success and reasonable fatty acid profiles, and better resembled newborn from a wild male. The use of mysidaceans solely (Diet M) provided the worse results in spite of the high DHA content. Significant differences were observed in newborn characteristics and fatty acid profiles among dietary groups and along the breeding season, especially in total n-3 HUFA and DHA. Monospecific diets including Artemia or mysidaceans very likely suffered nutritional deficiencies, which were reflected in morphological alterations of the muscle tissue (diet A) or abnormal early mortalities in newborn (diet M). Three progressive stages were identified along the whole breeding period: initial mixed capital-income period (100 – 120 days since the onset of the breeding period), followed by an inflexion period (short transitional stage - income sources), and finally a long period characterized by the use of income sources and the progressive exhaustion of body reserves. Special attention should be deserved to the progressive changes in fatty acid profiles along the breeding season, resulting in a decrease in newborn performance. Considering the time required for a diet to be reflected in newborn, we recommend Hippocampus guttulatus breeders to be fed on a high quality diet for at least three months prior the breeding period.
Highlights
The global trade in seahorses is estimated to exceed 20 million animals per year to sustain the aquarium trade, the traditional Chinese medicine and as souvenirs (Vincent, 1996; Planas et al, 2017a)
Monospecific diets including Artemia or mysidaceans very likely suffered from nutritional deficiencies, reflected in morphological alterations of the muscle tissue or abnormal early mortalities in newborn
Those deficiencies seemed to be overcome with the mixed diet AM, which provided the highest overall breeding success and reasonable fatty acids (FAs) profiles, and better resembled newborn from a wild male
Summary
The global trade in seahorses is estimated to exceed 20 million animals per year to sustain the aquarium trade, the traditional Chinese medicine and as souvenirs (Vincent, 1996; Planas et al, 2017a). Low spawning quality and juvenile survival rates are the most critical factors for optimizing commercial seahorse aquaculture (Adams et al, 2001; Chang and Southgate, 2001; Lin et al, 2007). Broodstock preparation is a critical step in the success of the spawning process of a certain species. On this regard, many studies have been directed toward egg quality in oviparous fishes and the underlying characteristics to produce viable fry (Kjørsvik et al, 1990; Brooks et al, 1997). The egg’s potential to produce viable fry is determined by several physical, genetic, and chemical factors, including the initial physiological processes occurring in the egg itself (Kjørsvik et al, 1990)
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