Differential Occupation of Available Coral Hosts by Coral-Dwelling Damselfish (Pomacentridae) on Australia’s Great Barrier Reef

Round 1

Reviewer 1 Report

The manuscript, “Differential occupation of seemingly suitable coral hosts by coral-dwelling damselfishes (Pomacentridae) on Australia’s Great Barrier Reef” is based on multi-species and latitudinal gradient in fish-coral association and demonstrates a differential occupation of coral colonies by damselfish species. The manuscript is well-written and will be of interest to any coral reef ecologists and conservationists. My main concerns are about some choices regarding the statistical analysis and its lack of details (sometimes), and that the discussion could be a bit more elaborate. Upon a small revision, I would recommend this manuscript for publication.

Comments line by line:

Lines 86: Remove the first “of the”

Lines 88: Please change “augments the few” to “increases the number of”

Lines 89: Full stop after “colony morphologies”

Line 90: Replace “by documenting” by “We investigate”

Line 91: Remove “in order”

Line 92: Replace “damselfishes’” by “damselfish”

Line 94: Replace “Investigating” by “Evaluating”

Line 136: Could you please provide more info about the diameter perpendicular?

Line 173: Replace “uncoupling” by “delineate”.

Lines 183-184: What conformity did you check? Did you mean this: “The appropriateness of the models selected were confirmed by testing the normality of residuals”?  

Line 185: Remove “for all models”.

Line 194: Instead of plotting residuals, a Shapiro-Wilk test could have been done for normality as well as a Levene’s test for homogeneity, although normality is the primary test performed to confirm the validity of the model selected.

Lines 199-201: How was the ranking made? What is the minimum value of deltaAICc?

Lines 202-213: This is a bit confusing why GLM and LM were performed instead of just consistently using GLM. It is especially relevant when the effect of coral species and damselfish species is tested. In GLM, this factor could be added as random.Could the authors clarify the reasons why they use different models?

Line 2014: Did the authors also adjust the p-values when performing Tukey post hoc tests? If yes, which correction was applied?

Line 208-210: Please rephrase.

Line 379: It seems like a verb is missing from the sentence.

Lines 385-395: I guess one aspect to explain in more details in the discussion is whether these habitat generalist species are also dietary generalists, which might be or not true. For example, it is easier to access oceanic zooplankton resources in the more exposed sites and thus damselfishes inhabiting branching corals in those environments are more likely to be zooplankton feeders (e.g. Wyatt et al. 2012; McMahon et al. 2016; Gajdzik et al. 2016) and not dietary generalists/omnivores, either omnivores (food on both plank and animal food sources) or bentho-pelagic feeders. This is particularly illustrated by the comments made for Dascyllus aruanus. Indeed, D. aruanus is an ommivorous bentho-pelagic feeder eating zooplankton and algae in equal proportion in other places in the world; e.g. Frédérich et al. 2009; Gajdzik et al. 2016)

Lines 405-406: Some of these colonies might not be occupied because of an impossibility to settle on these colonies due to oceanographic settings. I guess the authors to briefly mention this as another possible factors explaining variations in colony

Lines 446: Place provide examples where coral benefits from having damselfish hosts> For example, increase in oxygen input (e.g. Garcia-Herrera et al. 2017)

Line 457: Please modify the sentence, especially the part after the semi-colon or completely removed it because the next sentence is better written and provides a similar message.

General comments:

 -  Replace “damselfishes’” by “damselfish” throughout the text.

-   Considering that Seriatopora hystrix is the coral host with the highest fish biomass, it could be relevant to discuss about its sensitivity to global climate change.

References

Frédérich, B., Fabri, G., Lepoint, G., Vandewalle, P. & Parmentier, E. (2009). Trophic niches of thirteen damselfishes (Pomacentridae) at the Grand Récif of Toliara, Madagascar. Ichthyol. Res., 56, 10–17.

Gajdzik, L., Parmentier, E., Sturaro, N. & Frédérich, B. (2016). Trophic specializations of damselfishes are tightly associated with reef habitats and social behaviours. Mar. Biol., 163, 1–15.

Garcia-Herrera, N., Ferse, S. C. A., Kunzmann, A. and Genin, A. (2017). Mutualistic damselfish induce higher photosynthetic rates in their host coral. J. Exp. Biol. 220, 1803-1811.

McMahon KW, Thorrold SR, Houghton LA, Berumen ML (2016) Tracing carbon flow through coral reef food webs using a compound-specific stable isotope approach. Oecologia 180:809– 821

Wyatt, A.S.J., Waite, A.M., Humphries, S. (2012) Stable isotope analysis reveals community-level variation in fish trophodynamics across a fringing coral reef. Coral Reefs 31:1029–1044. 

 

Author Response

Please see all revision comments in the combined reviewer cover letter.

Author Response File: Author Response.pdf

Reviewer 2 Report

General comments:

The goal of this manuscript is to contribute to our knowledge about the occupancy of hard corals by coral-dwelling damselfishes, across a large spatial scale. The spatial scale and sites used provides variation in exposure, habitat, depth, coral cover, and reef zone. The fish-coral associations among reef zone and exposure represents our current knowledge about coral-dwelling damselfish occupancy and is based off a substantial dataset (51 sites along the GBR). Overall the paper is very well-written, cogent, interesting and presents conclusions that are logical and warranted relative to the study design. I therefore have very few major comments on the paper. My general concern is that I think the manuscript can better contextualize the author’s findings within other coral reef research. Specifically, I think that the study can be improved and scope broadened by providing more research and discussion on Pomacentrids as it relates to the findings in the introduction and discussion – habitat use, other latitudinal studies, and competition (few references provided). In addition, the text should be cleaned to be more concise. All should be solvable in the new manuscript version. I am open for further revisions if necessary.

 

Major comments:

Title:

Is there a better/more suitable title that does not use the word “seemingly”?

Abstract:

I would like to see a little more context leading up to the methods and results. Perhaps simplify the results into more coherent and concise sentences? Use space to add in more about why this study is important. Currently the abstract only says “habitat-forming corals and fishes are critical for the function of reefs” – a stretch/broad statement – broaden scope and introduce your study system/organisms. I also think the last two sentences can, and should be, improved to contextualize the present studies results. This will improve the studies citations in the future. Currently, ‘understanding the establishment, nature, influence, and resilience’ reads very broad and I am not even sure the results speak to all of these conclusions. Instead of reaching here be specific to how the results of the study fit into present coral reef research. E.g. ‘This research reveals a suite of factors at the local coral scale that influence occupation rates, including colony height, position on the benthos as well as the distance to other potential host corals.’

Introduction:

I would like to see more background on Pomacentridae literature and linked coral associations in the introduction (recent references below). Likely some of the text from the methods (ln 141-147) can be brought up to the introduction. In the current form the second to last introduction paragraph sets the stage for habitat, reef zone, specialist fishes, and literature on all three mentioned families. More text focused on the study species would help the reader understand how the current study fits into what we already know. For example, the studies in line 88 – what did they find? Be more specific in mentioning these studies findings rather than just the citation. Also, a brief discussion on competition is missing.

Methods:

Include Fig S1 in the main text? I respect the level of detail included in the data analysis section, but I feel that much of this can be streamlined and is repetitive. I would like to see the authors make an attempt to keep only the vital information to reproduce the study and/or analysis and direct the rest to the supplemental material.

Results:

Consider changing colours/shading for Fig. 3. I only see 4 colours: D. reticulatus and P. amboinensis are indistinguishable (understanding the low biomass values). Similar to my comments on the methods, the results should be streamlined. This level of detail is required for a PhD thesis chapter but not for a publication. It is difficult to pull the main findings out. E.g. parentheses detail in ln 340-341 is not needed, only keep ‘pooled’. Ln 347-349 and Ln 350-351 (SIMPER … colonies had fish) methods section? Remove repetitive explanatory statistical information, i.e. in 3.1 section ln 261 change to (betareg(logit): p = 0.002) and for ln 262 change to (p = 0.016). In the following paragraphs keep explanatory information with each first mention and omit for following cases (until the statistical test changes). This will help reduce text.

Discussion:

Well written. Few clean-up’s, see minor comments: e.g. paragraph ln 432-451 has 8 (i.e. …)’s. Cut down text and simplify thoughts and concepts for clarity.

Minor comments:

Ln 14 – ‘large spatial scale’

Ln 14-17 – clarify values here. 93% abundance of fish-coral associations? This is confusing. Also, what does -32% average prevalence mean? Negative percent?

Ln 19-21 – break this up with two percentages, one for each habitat type? Reef slope AND sand patch habitats hosted 75%? What was the other 25%?

Ln 68 – citation to number

Ln 86 – ‘for five damselfish’

Ln 104 – sentence about sheltered vs exposed is needed here instead of brief mention. Researchers in a different field might not be as familiar with the terminology and weather/exposure differences among sides of a reef.

Ln 166 – don’t need ‘recorded by eye as they were swimming around’

Ln 170 – again, ‘clove oil’ may not be known by the reader. I suggest directly noting the amount diluted in ethanol/seawater and mentioning this is used as an aesthetic.

Ln 365 – change to ‘… and branch spacing (shaded), had …’

Ln 376 – restructure sentence to not have a subset of thought in parentheses.

Ln 379 – delete ‘very’

Ln 380 – delete parentheses text

Ln 390 – what does ‘(and aspect ratio)’ add to this sentence?

Ln 392 – parentheses text needs to be cut down throughout the manuscript. At this point the reader should know what abiotic and biotic mean. If they don't introduce these terms in context in the introduction or include the additional information in the sentence structure.

Ln 440 – change to g m^-2 not g 250 m^-2

 

Notable studies that are similar, updated references on competition and habitat-use in other groups of Pomacentrids for introduction paragraph:

- Pratchett et al 2016. Habitat-use and specialisation among coral reef damselfishes. In: Frédérich B, Paramentier E (eds) Biology of damselfishes. CRC Press, Boca Raton, pp 84–121 (habitat use/competition)

- Gajdzik et al 2018. Similar levels of trophic and functional diversity within damselfish assemblages across Indo-Pacific coral reefs. Funct Ecol 32:1358–1369. (gradient)

- Maire et al 2018. Community-wide scan identifies fish species associated with coral reef services across the Indo-Pacific. Proc R Soc B 285. (broaden results in discussion, counter point)

- Eurich et al 2018. Habitat selection and aggression as determinants of fine-scale partitioning of coral reef zones in a guild of territorial damselfishes. Mar Ecol Prog Ser 587:201–215. (habitat use/competition)

- Komyakova et al 2019. Comparative analysis of habitat use and ontogenetic habitat-shifts among coral reef damselfishes. Environ Biol Fish 102:1201. (ontogenetic shifts/competition)

- Waldock et al 2019. The shape of abundance distributions across temperature gradients in reef fishes. Ecol Lett 22:685–696. (gradient/broaden results in discussion)

- Morais et al 2019. Pelagic Subsidies Underpin Fish Productivity on a Degraded Coral Reef. Curr Biol 29:1521–1527. (high-flow environments)

Author Response

Please see all revision comments in the combined reviewer cover letter.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper shed some light on the interesting association between tropical hard corals and fishes of the family Pomacentridae. The information helps understanding on large scale the dynamics occurring between the coral reef and the associated fauna, and it’s important in a conservation perspective. The manuscript is detailed and well written, and I suggest its publication after minor changes that are listed below.

 

Line 37 – Delete “invertebrate”.

Line 38 – Change “crustacea” to “crustaceans”.

Lines 42-43 – I would suggest to add the scientific names of the cited families; I believe it’s better not to use only the common names to identify specific organisms in a scientific paper.

Line 53 – To avoid redundancy, change “coral colonies” to “corals”.

Line 54 – Delete “colonies”.

Line 56 – Add “spp.” after “Gobiodon”.

Line 71 – Add authority of the species.

Line 75 – I believe that fishes associated with corals can be divided into two main groups: plankton feeders and corallivorous. Maybe this aspect can be developed a bit more in this section.

Lines 85-86 – It seems that some words are missing in the sentence.

Line 100 – I would suggest to move the map from the supplementary material to the main paper. In the map, not all 51 sites are shown, please add the missing ones. In the caption, please write the scientific names in full.

Lines 104-109 – I find the sentence a bit confused, maybe it can be rewritten.

Lines 111-113 – I think it would be nice, if it’s possible, to add a figure with the pictures of the cited species. It would improve the manuscript.

Same lines – Please add authorities and write scientific names in full.

Line 149 – Performed by scuba diving? Please add.

Line 150 - How? Visual census? At what distance, how many operators? Please add, or alternatively, since you explain the same aspect from line 165, delete from here and add the missing information in that sentence.

Line 216 – Delete the unnecessary bracket.

Line 247 – Add missing reference number.

Line 252 – To avoid redundancy, change the last “damselfish” to “species”.

Line 253 – For the same reason, delete “coral”.

Line 298 – Can you please add how many specimens of this species (and eventually the others) were found on average on each coral? I think it would be interesting to have an information about the abundancy, and not only the biomass.

Line 321 – Same, it would be nice to add the number of specimens.

Line 421 - Maybe some pictures or a draw showing different coral morphologies and different species of fishes would be nice.

Author Response

Please see all revision comments in the combined reviewer cover letter.

Author Response File: Author Response.pdf