Effects of River Salinization on Freshwater Fish Behavior—Cerebral Lateralization, Activity, Boldness, and Schooling^†

Round 1

Reviewer 1 Report

In general, the abstract seems good (in format and content). Even considering that the space is limited, I have some suggestions to clarify a few points:

L16 What does it means secondary? alternative wording?

L20 What do you mean with "regarding population trends"? Group behaviour?

L21-22 If possible, include salinity values.

L22 and next. Explain briefly which was the "recording system".

L3, L25 Lateralization/lateralized? Alternative wording?

Author Response

Dear Reviewer,

Thank you for your commentary. To clarify your points:

P1. L16 What does it means secondary? alternative wording?
R: Salinization is denominated secondary when resulting from human activities, usually land development and agriculture. In our experiments, we recreate an acute exposure to salinity as to simulate a secondary salinization scenario, for example industrial discharges. Therefore, we find it the most appropriate to use this terminology.

P2. L20 What do you mean with "regarding population trends"? Group behaviour?
R: Results were interpreted regarding population trends, i.e. regarding fish behaviour in each treatment of salinity as a group, and not as independent individuals. However, the text was removed for clarification.

P3. L21-22 If possible, include salinity values.
R: Salinity levels of the water during our experiments were only measured by conductivity (mS/cm). To contextualise, seawater has conductivity levels of 35 to 50 mS/cm, therefore we found our salinity gradient appropriate to observe the effects of salinity in freshwater fish.

P4. L22 and next. Explain briefly which was the "recording system".
R: We performed various timed behavioural experiments, and instantly monitored and recorded the behaviours every three minutes, by visual observation of each behavioural parameters. The text was improved for clarity.

P5. L3, L25 Lateralization/lateralized? Alternative wording?
R: Studies found that several stressors, including salinity, might affect cerebral lateralization in intolerant fish species – i.e. interspecific variation in both strength and direction of laterality in fish, at a population level. In these trials, individual behavioural lateralization was assessed by performing a standard detour test, and the direction of turns in front of the barrier in the channel was recorded. Thus, when interpreting the results, we accessed if fish turned more often to the left or the right of the obstacle, in other words, if the group was lateralized more to the left or right. We believe this terminology to be the most appropriate in this context.

Please find attached the document with track changes. 

Kind regards,

Tamara Leite