Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is well-written and easy to follow. My review comments are primarily focused on the content of the Methods and Results sections, and how the analysis was undertaken.

Methods.

Author should acknowledge that the study design means that the impact of urbanization was inferred from spatial pattern alone. Is there any historical (pre-urban development) fish collection data that could be used to expand the interpretation of Table 2 data? Even if it is not suitable for a BACI style comparison, historical accounts of only trout and sculpin in urban reaches would complement this study's findings.     

3.1 Fieldwork.

Providing the following details would improve the description of fish sampling: (i) when during the year was sampling done, and was it done during the same year; (ii) is the single-pass method used associated with a state or regional backpack electrofishing protocol (especially as catch data is used to calculate a coldwater IBI)? If so, provide reference; (iii) while length of habitat sampled was standardized, was search effort (seconds) recorded? (iv) single-pass sampling was used to describe stream fish assemblages. Several studies have evaluated whether single-pass sampling of streams is sufficient for this purpose - provide supporting references (e.g. Kruse et al. 1998, Meador et al. 2003, Bertrand et al. 2006, Kauth et al. 2019).

3.2 Data Analysis

line 137. Readers may not be familiar with the coldwater IBI that it is important to the study's results/interpretation. Provide a some details and purpose of the index; including some of the individual metrics that would be relevant to the species caught (Table 2). 

line 148. While nMDS allows the author to visualize the 2 groups of fish community data, the fish fauna is not diverse and among-site differences are easy to discern simply by reading Table 2; especially as rural sites have only 1 to 3 species. nMDS is not necessary to communicate study results.   

line 149. Given the large difference in channel width among sites (2.7 to 10m), the area (and presumably electrofishing effort) sampled at each site is not equal. For comparisons of species richness, similarity indices and multivariate analysis, the author needs to evaluate when standardization by area or individuals is needed to avoid comparisons among incongruous data - and adjust data analysis accordingly.      

Results.

Table 1. use same heading order as other tables. 

lines 177-180. Which metrics of the IBI were most influential in generating good and fair scores?

Discussion.

Lines 223-237. Without pre-urbanization fish assemblage data from the urban sites or fish data from other rural stream sites close to the Mississippi River, the relative importance of close proximity to a large species pool versus habitat degradation cannot be inferred. This limitation of the sampling design needs to be acknowledged, and more robust designs to improve hypothesis-testing identified.    

Lines 294-307. The prescription of restorative actions is difficult without more detailed instream habitat/geomorphological data than what was collected in this study. To improve the identification of appropriate interventions, the author could recommend appropriate detailed investigations should be completed first.     

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This paper is an intersting small scale study of fish in small creeks near the Driftless Area of southeastern, Minnesota, USA.

The data are limited in sample size, but the results are well structured to get the most information possible without attempting to do anything unnecessary.  There are two main areas that should be updated before acceptance for publication.

Firstly the Methods section needs upadating.  Importantly, at the moment there is no time stamp on the data collection and this information is essential.  Not only for future researhcers to use the dtaa in comparison studies, but to allow the reader to evaluate the potential of temporal confoudning in the survey data collected.  That is, as long as the surveys were all done within a reasonable time frame, the reader can be assured that the results reflect spatial impacts, not temporal ones.  I have made some other comments about other minor methods section information that is missing regarding the cold water IBI and the siimlarty measure used for the ordination.

Secondly, the design is very limited and not ideal.  This is common and sometimes unaviodable in our already impacted world.  I feel the discussion should investigate the limitations of the study some more. In essence, there are many reasons why the downstream sites may be different to the upstream ones, apart from urbanisation. For example differences in efishing efficiency, water temperature, etc.  In an ideal design there would be reference surveys in streams that havent yet been urbanised.  If this is not possible, then it should be mentioned in the least. Consider that the current research is a design wheres sites are chosen by "expert opinion of representativeness", in just four creeks in one small region.  To that end, it really is just a pilot study and the title of the paper should make it clear that the results are not intended as a universal statement.  

Overall the results support previous research findings, is well presented and the writing is very good. Neverthelss, the paper will be improved by making several technical clarifications and i have highlighted many of these in my attached review with comments.

Comments for author File: Comments.pdf

Author Response

Please see the attachment. I also have another document responding to general comments that I will attempt to submit as well.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Good job with revisions to the draft paper. I have provided below suggested text edits to improve readability of the inserted sentences.

lines 117-118:

Brook trout also were stocked and successfully reproduced in some of the coldest headwater streams. A few native brook trout populations have persisted as well [48].

lines 166-168.

Single-pass electrofishing is sufficient for documenting the fish community in small streams such as those in this study [51–54], and data collected with this protocol are used to calculate a regional coldwater fish index of biotic integrity [32]

line 191-193: 

Prior to statistical comparisons, taxa richness values were standardized across sites using electrofishing effort (taxa/1000 sec electrofishing time). Sampling effort was variable among sites due to differences in stream area and habitat complexity. 

lines 221-222. Stream site water temperatures were not measured during sampling. 

Table 4. change electrofishing duration to electrofishing effort (to be consistent with earlier text). Also, move the row to the bottom of the table, below totals.

lines 304-309. 

Unfortunately, water temperature data was not available for my rural and urban stream sites, so I was unable to determine the role of water temperature in structuring fish communities. Future studies need to include water temperature monitoring, especially at the urban sites.

lines 337-340. 

Water temperature data from my study sites and these other, least disturbed streams would allow me to assess the influence of temperature on fish communities structure.

lines 447-448. 

needed to determine if the patterns observed in this pilot study are generalizable across the region. 

Author Response

Review Round 2

 

I made all the suggested changes listed below.

Good job with revisions to the draft paper. I have provided below suggested text edits to improve readability of the inserted sentences.

lines 117-118:

Brook trout also were stocked and successfully reproduced in some of the coldest headwater streams. A few native brook trout populations have persisted as well [48].

lines 166-168.

Single-pass electrofishing is sufficient for documenting the fish community in small streams such as those in this study [51–54], and data collected with this protocol are used to calculate a regional coldwater fish index of biotic integrity [32]

line 191-193: 

Prior to statistical comparisons, taxa richness values were standardized across sites using electrofishing effort (taxa/1000 sec electrofishing time). Sampling effort was variable among sites due to differences in stream area and habitat complexity. 

lines 221-222. Stream site water temperatures were not measured during sampling. 

Table 4. change electrofishing duration to electrofishing effort (to be consistent with earlier text). Also, move the row to the bottom of the table, below totals.

lines 304-309. 

Unfortunately, water temperature data was not available for my rural and urban stream sites, so I was unable to determine the role of water temperature in structuring fish communities. Future studies need to include water temperature monitoring, especially at the urban sites.

lines 337-340. 

Water temperature data from my study sites and these other, least disturbed streams would allow me to assess the influence of temperature on fish communities structure.

lines 447-448. 

needed to determine if the patterns observed in this pilot study are generalizable across the region.