Abstract
Tropical gar, Atractosteus tropicus, is a carnivorous fish species from Southern México with high value and acceptance in local markets. Therefore, the present study aims to spare proteins in diets for larviculture of this species. An experiment was performed using three different experimental diets with increasing carbohydrate levels based on potato starch (S) and decreasing protein content (P) and total energy: 16% S (16% S–44% P), 22% S (22% S–40% P) and 28% S (28% S–36% P). Tropical gar larvae (five days post-hatching, 2.1 mm average notochordal length) were assessed for growth, survival, degree of cannibalism, and digestive enzyme activities for 30 days. Highest growth and survival (24%), as well as the lowest cannibalism (33%), was seen in larvae fed the 28% S diet, and these larvae also had the highest lipase, amylase and glucosidase activities (0.28, 0.56 and 0.11 units, respectively). Protease activity (alkaline protease, trypsin, chymotrypsin, and leucine aminopeptidase) was higher in the larvae fed the 22% S diet than in those given the 16% S and 28% S diets. In conclusion, dietary inclusion of potato starch at 28% S enhanced growth, survival and some digestive enzyme activities, and decreased cannibalism in the larval gar. Potato starch could replace dietary protein as a major source of energy for A. tropicus larvae, thereby reducing the cost of diets.
Highlights
Aquaculture in México has great potential, especially of native freshwater species, such as the tropical gar (Atractosteus tropicus, Gill 1863) in the Southwest
Growth of A. tropicus larvae showed significant differences (p < 0.05) among the three diets, Growth of A. tropicus larvae showed significant differences (p < 0.05) among the three diets, such such that larvae fed the 28% S diet exhibited a higher growth than larvae fed the 16% S diet, while the that larvae fed the 28% S diet exhibited a higher growth than larvae fed the 16% S diet, while the 22%
The specific activity of α-amylase was markedly and significantly higher (p < 0.05) in larvae fed the 28%S diet relative to the other two diets, which showed no significant differences between (Figure 5A)
Summary
Aquaculture in México has great potential, especially of native freshwater species, such as the tropical gar (Atractosteus tropicus, Gill 1863) in the Southwest. Total fisheries production of this species was ~300 tons per year and it is decreasing every year [1]. Inclusion of specific food components, mainly during the larval stage, could contribute to maximize their growth and survival, and increase fry production in mass culture [2]. Studies related to the use of live prey as well as adaptation to commercial rainbow trout formulated diets (silver cup) show that high rates of cannibalism occur using artificial diets during the first 15 days of larviculture of A. tropicus [3]. For this reason, careful handling of larvae is Fishes 2017, 2, 3; doi:10.3390/fishes2010003 www.mdpi.com/journal/fishes
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