On the Acclimatization of Pelagic Fish Species Juveniles in a Closed Environment: An Atlantic Horse Mackerel Case Study

The effects of different artificial light wavelengths on some behavioural features of juvenile pelagic Atlantic horse mackerel, Trachurus trachurus (Actinopterygii: Perciformes: Carangidae)

“…The behavioural response in terms of positive (attraction) and negative (repulsion) phototaxis of juvenile Atlantic horse mackerel individuals was measured by the frequency of presence recorded in percentage (%), resembling the method reported by Hunter (1966). The observation period has been divided into three main phases: 'Early' (1-5 min), 'Middle' (6-15 min), 'Late' (16-20 min), consistent with that reported in Okpala et al (2017). Recordings were observed at 2× speed with a temporal sequence of 30 frames, randomly chosen within 1 min intervals throughout the session.…”

“…Prior to carrying out the study, ethical approval was obtained consistent with the procedures specified by the Risorse Biologiche e le Biotecnologie Marine -Consiglio Nazionale delle Ricerche (IRBIM-CNR). All the methodology applied herein was guided by standards of previously published references (Marchesan et al 2005, Liao et al 2007, Meager et al 2010, Okpala et al 2017. Collection of juvenile fish individuals.…”

“…Acclimatisation process. Acclimatization period has always been deemed very useful particularly when fish are brought into a new closed environment (Marchesan et al 2005, Okpala et al 2017. Introducing the acclimatisation period appears routinely observed in other fish-related studies (Marchesan et al 2005).…”

“…Introducing the acclimatisation period appears routinely observed in other fish-related studies (Marchesan et al 2005). Before the start of the experiment, the fish juvenile individuals were acclimatized (Okpala et al 2017) for 20 days. Specifically, this acclimatization process involved the use of an isolated chamber with a photoperiod of both twelve hours of light (from 0800 to 2000 h) and dark (from 2000 to 0800 h).…”

“…Specifically, this acclimatization process involved the use of an isolated chamber with a photoperiod of both twelve hours of light (from 0800 to 2000 h) and dark (from 2000 to 0800 h). Given that high feeding intensity of Atlantic horse mackerel especially during early mornings and night has been reported (Jardas et al 2004), the fish juvenile individuals were fed ad libitum twice per day (at scheduled times) with crushed frozen shrimps (Okpala et al 2017). Importantly, no juvenile individuals died during the entire acclimatization process.…”