How does a cooperatively breeding cichlid (Neolamprologus pulcher) adapt its behaviour to a turbid environment?

Sammanfattning

Turbidity, caused by suspended particles scattering light, impairs visual perception and has been shown to alter short-term behaviour in fish. However its long-term effects remain poorly understood. This study aims to investigate the long term effects of increased turbidity on Neolamprologus pulcher and whether they habituate to it over time. The term “long-term”, referring to a two week testing period, is used in relation to prior publications on this subject where “short-term" tests spanned from minutes to a few hours. We hypothesize that turbidity will affect the behavior of N. pulcher. In this study, we investigated the behavioural responses of the cooperatively breeding cichlid N. pulcher to turbidity over eight weeks (two weeks per treatment) using a within-subject experimental design. We exposed breeding groups to both turbid (1.96-5.45 NTU) and clear (0.43-1.21 NTU) water conditions and measured rates of aggressive, affiliative and submissive behaviours, spatial dynamics, feeding activity, and territory maintenance. We did not observe any noticeable effect of turbidity on any of these behaviours. However we found trends of behaviours changing between treatments over time. Such as a decline in overt aggression toward group members in clear water and a decline in restrained aggression towards the predator in clear water. Affiliative- or submissive behaviours between group members occurred too rarely in the study to draw any firm conclusions. Additionally we found no effect of behavioral habituation to increased turbid conditions over time. These results imply that the behaviours of N. pulcher show little to no effect on turbidity after 15 hours exposure at turbidity level of ~3 NTU. These results offer insights into what effects visual impairment may have on the behaviour of N. pulcher, and possibly other group-living fish in environments affected by increased turbidity.