Comportamento de juvenis de Oreochromis niloticus classificados por personalidade frente a diferentes desafios

Abstract

In the study of behavior, the terms used to differentiate animals by personality are “bold” and “shy” or proactive and reactive, respectively. The objective of this work was to classify Nile tilapia (Oreochromis niloticus) juveniles by personality and to conduct exploration and competition tests among individuals of different personalities in the face of challenges. For the personality classification with the new environment test, 324 tilapias were used. The test was carried out until 60 bold and 60 shy animals were obtained. After selection, the animals were identified with a microchip and divided into six tanks of 200L in a recirculation system, with 20 animals per tank and divided by personality. Two tests were carried out: the test of the new object which consisted of the selection of two random animals, “bold” and “shy”. These animals were transferred to the test tank and checked which one approached to the object placed in the tank. The second test was the competition for food. In a 200L tank, a transparent cylinder was placed in the central region, the cylinder contained a square hole in its central region with enough space for the passage of a fish. A “bold” and a “shy” animal were placed at the same time in the tank for each test. After 10 min of acclimatization, a feed pellet was added inside the cylinder. When the pellet was captured by the fish, the time was recorded, and another feed pellet was added. After consuming the second pellet, a third one was added, and observations were again made. The total time taken to consume the three pellets was 20 min. In the first test, animals with a “bold” personality showed a shorter average approach time to the new object compared to animals with a “shy” personality (p <0.001). Regarding the 60 tests carried out with the pairs "bold" and "shy", 65% "bold" and 21.6% "shy" arrived at the object first. 13.3% of the tests none of the animals approached the object. For the competition test for food, it was found that for the first feeding (Pellet 1), animals with a “bold” personality obtained a shorter average time compared to animals with a “shy” personality (p <0.001). In the second feeding (Pellet 2), the data did not show a statistical difference (p = 0.1733). The same verified to pellet 1 was observed for the third feeding (Pellet 3) (p = 0.001). The average number of “bold” animals that captured pellet 1 was higher (58.4%) compared to “shy” (33.3%). In general, the “bold” animals proved to be more exploitative to both types of challenges.