Multi-Species Assessment of Injury, Mortality, and Physical Conditions during Downstream Passage through a Large Archimedes Hydrodynamic Screw (Albert Canal, Belgium)

Round 1

Reviewer 1 Report

GENERAL COMMENTS

This is an interesting study on downstream fish migration, focused on multispecies risk of injury and mortality during downstream passage through a large Archimedes screw for bream, eel and roach. At the same time, the study also addressed the physical conditions through the facility, that fish experienced, by using live fish and passive sensors. This is a novel study with appealing findings and a broader scope. Overall, the study is well-written, well-structured and with clearly defined objectives/hypotheses. I found it however too long and I think some sections could be shortened (say, in 20%) without losing important information. I also suggest the authors to better support the choice of their species, for example, do they represent different swimming modes (i.e. anguilliform, sub-carangiform and carangiform?), different ecological guilds? This would extend the scope of your study. Below are specific comments should the authors want to use them to improve their manuscript.

 

SPECIFIC COMMENTS

L26 – I think you could further develop this point, i.e. readers expect to see here which species showed the highest injuries and mortality. Could add this (% in parentheses).

L48-50 – Could you provide references to these studies?

L96 – Why were these species chosen? Because of their different ecological guilds? Swimming modes? Other?

L98-111 – All this paragraph should be removed from here and moved to the final part of the Discussion. How can you comment on the findings /achievements of your work, if you are presently on the Introduction did not assess yet the methods, results, etc.

Here, you should end this section by stating your specific objectives and predictions (i.e. why are the objectives and the expected results for each of them).

Table 1 – Rotational speed: pay attention to the / notation with m3/s (perhaps better m3.s-1)

L164-168 – This was already said on lines 136-140, so please remove.

L172-173 – I think you could go further here and explore the fact that these 3 species may represent different swimming modes? Different ecological guilds? This would extend the scope of your study.

L200- How many fish per species did you employed here?

Table 2 – tables should be self-explicative without the caption, however the column “operation scenario” with the 3 options (low, medium, high) is not clear per se. Perhaps adding “low, medium and high rotational speeds”?

L217 – Provide brand and model of the sensors.

L224 – place parentheses when calling for figures.

L243 – Replace “Below it are” by “Below there are”.

Figure 4 – Suggest to changes the symbols, as these are not perceptible according to the rotational speed. Suggest to use a color gradient (lighter color- low; darker color-high) or the same symbol with different sizes (smaller-low; larger-high).

L350 – You cannot pass from figure 3 to figure 6, without first citing figures 4 and 5. Renumber then all your figures, so can appear in sequence.

L400-403 – This should go to the M&M, as this is not a result but methods.

L405 – Could you specify?

L417-419 – But what the mortality rates for each species under these conditions? Specify please.

L421,430 – Please be consistent in the use of the Chi-square symbol (the is upper, not lower).

L430-432 – Could you please provide values (mortality rates) between parentheses?

Figure 5 – Same comment as figure 4.

L480-487 – Please save comparisons with other studies for the Discussion. Here you should present the results only.

L491 – “operational scenarios 40 Hz and 48 Hz.” Please keep consistency, and refer instead to the low, medium or high rotational speed scenarios. Same on L503, Fig. 6,..

L496-497 – This is methodology and should be moved accordingly. Same on lines 499-500.

L501 – 33Hz or 30Hz? Suggest removing “some”.

L520 – I clearly think that this section should be removed. Does not make here a summary of results that you have presented before, and there is hardly any numbers or statistics here. The manuscript, I think, is also far too long, and this is clearly a section that can be removed, without losing important information.

564 – the lowest (not “lowest”)

Fig A2 – provide units for length and weight.

Table A1 and A2 – Provide complete captions (i.e. study area, goal,..).

Author Response

Please, see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

In my opinion this paper is an example of well-designed outdoor experiment providing very interesting information on the effect of Archmedes hydrodynamic screw on the downstream passing fish. 

I will recommend that this paper be published after the changes in the organisation of the text proposed below have been made and minor shortcomings have been remedied:

1. Line 106-111: placing the results in the introduction is an unusual practice; I would expect hypotheses rather than results here!
2. Line 296-297: these are results, so they should be moved to the chapter “Results”.
3. Line 306-308: these are results, so they should be moved to the chapter “Results”.
4. Line 450: instead of: “55% of recovered eels…” should be: “55% of recovered breams…”
5. Line 480-487: this paragraph should be moved to the chapter “Discussion”.

 Figures and Tables

1. Figure 5. Since the drawings should be self-explanatory, it should be mentioned that in the case of eel, the injury type “scale loss'' means “superficial scratches” (assuming that I have correctly understood the relevant description in the chapter 'Materials and Methods')
2. Figure A3. The inclusion of this figure in the appendix is somewhat inconsistent, given that Figure 4 is in the main part of the manuscript. I suggest moving this figure to the main part of the manuscript.
3. Table A1 and A2. Such exact p-values in the last column of these tables are more confusing than informative. I suggest giving standard values: p<0.01 or p<0.001

Author Response

Please, see the attachment.

Author Response File: Author Response.pdf