Basic reporting

The manuscript “Biogeographic pattern in the cartilaginous fauna (Pisces: Elasmobranchii and Holocephali) in the southeast Pacific Ocean” by Bustamante et al. describes the assemblages of sharks, skates and chimaeras off the coast of Chile through fishery independent trawl surveys. The paper is well written, generally clear and free from excessive grammatical and spelling errors. Sufficient background and introductory material is provided to place the study into context and the methods and materials are well described.

A detailed list of edits and annotations is provided as an attachment. Please read these over and clear up any confusion. Although the text is generally well written there are still errors that should be addressed. The one recurrent error is the overuse of the semicolon. Many times in the text, a semicolon is used when a comma was appropriate. Please revise all the uses of the semicolon in the manuscript and ensure that it is appropriate. You can refer to materials like this (https://owl.english.purdue.edu/owl/resource/607/04/) for help.

The figures and tables are clear and informative. There are no redundancies or irrelevant figures. The legends of figures 5 and 6 could use a line about the meaning of the site code (e.g. 7A.2, 5B.4, etc…). This will help the reader pick up patterns. Figure 1 is good, and if it is possible to add the areas of high fishery CPUE, that might be even more useful.

Experimental design

The manuscript clearly outlines a research question and the methodology is relevant for addressing that question. Overall, the experimental design, fieldwork and analyses are appropriate. There are a few small areas that are not entirely clear, and hopefully my annotations will help clear those up. Also, as noted above, the site codes should be explained in the main text of the manuscript.

Although it is well understood that survey data is not perfect and that the available data should be used, there are some flaws in the data collection that should be acknowledged by the authors. The primary one is the difference of timing in the tows at different sites. As mentioned on lines 85-87, all sites were not towed in the same season and there is a bias as to the timing of sampling of different latitudes. Since latitudinal gradients are discussed quite heavily in the paper, there should also be a discussion as to the potential effects of the sampling timing at different sites. This would work quite well in the last section of the Discussion.

Validity of the findings

The results and interpretation of the results are appropriate, relevant and statistically sound, and provide a significant addition to the knowledge base of fish community assemblages. The authors do a good job of providing a review of existing data and how this study contrasts and adds to the existing knowledge base.

Comments for the author

I recommend this manuscript be accepted for publication after the edits and suggestions made here are incorporated or addressed. These will help with the clarity and thoroughness of the manuscript.