Behavioural analyses
Neophobia (number of contacts and inspections of a novel object) and exploratory behaviour were assessed using a plastic test arena (7 cm depth x 7 cm width x 30 cm length) filled with 0.7 L of water. The arena was divided into six equally spaced zones: a covered acclimatisation section (zone 0) with a sliding opaque door, and five open test zones (5 cm each) without cover (zones 1, 2, 3, 4 and 5) delineated by marks at the top margins of the arena walls. A coloured toy block (0.5 cm depth x 0.5 cm width x 3.5 cm height) was glued at the middle of zone 3 to serve as a novel object (Fig. S2). Nine-month old fish were placed individually into zone 0 for 15 min acclimatisation, after which the removable gate was slowly lifted, and the fish behaviour recorded for 20 min with an overhead camera fixed 0.5m above the arena. After the test period, tanks were drained, rinsed with ethanol and distilled water. Videos were analysed by the same person using BORIS v. 7. 1. 4 (Friard & Gamba 2016) to ensure consistency. The following four behaviours were quantified for both parents and offspring: (1) latency (s) to exit the acclimatisation zone, (2) number of inspections within 3 cm of the novel object (i. e. individual facing towards the novel for more than three seconds), (3) number of contacts with the novel object, and (4) number of movements between zones (activity).